ALUMINIUM IN COMMERCIAL VEHICLES EUROPEAN ALUMINIUM ASSOCIATION FOREWORD
Aluminium in Commercial Vehicles has been compiled by the European Aluminium Association in answer to the needs of manufacturers and users of commercial vehicles and accessories. It is a com - pendium of basic information on such aspects of aluminium as:
• The reasons for using it
• The main rolled, extruded and cast alloys available to manufacturers; their properties, mechanical characteristics etc.
• The design and calculation of structures, fatigue and collision behaviour
• The joining of semi-finished products: fabrication, welding and other joining techniques
• The corrosion resistance of aluminium alloys under service conditions
• Surface treatment
• Cleaning and repair
This guide will be of particular interest to design and process engineers, to repair and maintenance man - agers and more generally to anyone with an interest in the applications and development of aluminium in road transport.
Given the obvious limitations of a single volume, it has not been possible to deal with all aspects in detail. We have opted to present what we regard as the most up-to-date concepts and have indicated the most relevant standards which the reader can refer to for further information.
The information in this publication is general in nature and is not intended for direct application to specific technical or scientific projects. The European Aluminium Association cannot be held liable for any damage, costs or expenses resulting from the use of the information in this publication. For additional information please contact your aluminium supplier to be able to discuss details dir ectly with the relevant experts. CONTENTS
I. FOREWORD ...... 3
II. ALUMINIUM IN TRANSPORT ...... 7 1. One century of aluminium in transport ...... 8 2. Evolution of commercial vehicles ...... 12 3. Aluminium applications and weight savings ...... 13 4. Today’s concerns ...... 13
III. WHY USING ALUMINIUM ...... 15 1. Short pay-back ...... 16 2. Aluminium performance properties ...... 18 3. Environmental and social Benefits ...... 22 4. On the road… ...... 25
IV. FREQUENTLY ASKED QUESTIONS ...... 29 1. Aluminium ...... 30 2. Aluminium chassis ...... 32 3. Aluminium tippers ...... 35 4. Aluminium tankers ...... 37
V. ALUMINIUM ALLOYS FOR COMMERCIAL VEHICLES ...... 39 1. Foreword ...... 40 2. International product designation ...... 41 3. Basic temper designations ...... 42 4. Subdivisions of H temper designations ...... 42 5. Subdivision of T temper designations ...... 43 6. Typical alloys for commercial vehicles ...... 44 7. Influence of temperature on mechanical properties . . . . 50 8. Influence of fabrication on the properties of the alloys . 52 9. List of standards ...... 55
VI. DESIGN AND CALCULATION ...... 57 1. Foreword ...... 58 2. Possibilities with aluminium ...... 58 3. Symbols ...... 58 4. Aluminium versus Steel ...... 59 5. Limit state design ...... 62 6. Serviceability limit state ...... 64 7. Ultimate limit state ...... 64 8. Fatigue ...... 76 9. Special design issues ...... 86 10. References ...... 89 VII. FABRICATION ...... 91 1. Foreword ...... 92 2. Fabrication of products from plate ...... 93 3. Fabrication of products from extrusions ...... 98 4. Drilling ...... 102 5. Tapping ...... 103 6. Deep Drawing ...... 104 7. Spinning ...... 105
VIII. WELDING ...... 107 1. Foreword ...... 108 2. TIG welding (Tungsten Inert Gas) ...... 109 3. MIG welding (Metal Inert Gas) ...... 110 4. Plasma MIG welding ...... 118 5. Laser welding ...... 118 6. Laser MIG welding ...... 119 7. Resistance welding ...... 120 8. FSW - Friction Stir Welding ...... 120 9. Surface preparation before welding ...... 122 10. Quality control ...... 123 11. Design and prevention of deformation ...... 126
IX. OTHER JOINING TECHNIQUES ...... 129 1. Adhesive bonding ...... 130 2. Screwing and bold fastening ...... 133 3. Riveting ...... 133 4. Snap-Lock & Clipping ...... 135
X. DECORATION AND FINISHING ...... 137 1. Foreword ...... 138 2. Possibilities with aluminium ...... 138 3. Mechanical finishing ...... 139 4. Chemical decoration ...... 141
XI. CORROSION RESISTANCE ...... 145 1. Definition of corrosion ...... 146 2. Corrosion of aluminium ...... 146
XII. CLEANING OF ALUMINIUM COMMERCIAL VEHICLES ...... 153 1. Foreword ...... 154 2. The nature of stains ...... 154 3. The choise of detergent ...... 155 4. Application of the detergent ...... 155
XIII. REPAIR OF ALUMINIUM COMMERCIAL VEHICLES ...... 157 1. Foreword ...... 158 2. Execution of repair ...... 159 3. Repair of aluminium chassis ...... 159 4. MIG and TIG weld repairs ...... 160
Acknowledgments and photo credits ...... 162 EUROPEAN ALUMINIUM ASSOCIATION CHAPTER II
ALUMINIUM IN TRANSPORT
1. ONE CENTURY OF ALUMINIUM IN TRANSPORT ...... 8 2. EVOLUTION OF COMMERCIAL VEHICLES ...... 12 3. ALUMINIUM APPLICATIONS AND WEIGHT SAVINGS ...... 13 4. TODAY’S CONCERNS ...... 13 8 EUROPEAN ALUMINIUM ASSOCIATION ALUMINIUM IN COMMERCIAL VEHICLES CHAPTER II
1. One century of aluminium in transport
Airbus A380
In 1903, the Wright brothers is fundamental to the aviation It was in the 1920s that alu - made aviation history when they industry. It accounts for more minium shipping applications achieved the world’s first flight than 60% of the structural started to expand due to new powered by a lightweight weight of the Airbus A380, and alloys becoming available for engine made with aluminium up to 80% of short- and mid- marine applications. components. Today, aluminium range aircrafts. EUROPEAN ALUMINIUM ASSOCIATION ALUMINIUM IN COMMERCIAL VEHICLES CHAPTER II 9
Cruise ship with aluminium superstructure Today, 1000 high-speed passen - ger ships are in service, most of them have a structure and superstructure made of alu - minium. Cruise ship superstruc - tures are commonly made of aluminium, while over half of all yachts are completely made out of aluminium. These ships take full advantage of aluminium’s lightness and strength, as well as its corrosion- resistance, an indispensable prop - erty for marine environments.
Catamaran UAI 50 (Babcock) 10 EUROPEAN ALUMINIUM ASSOCIATION ALUMINIUM IN COMMERCIAL VEHICLES CHAPTER II
TGV Duplex (Alstom-SNCF)
In the 1980s, aluminium speed trains. In 1996, the TGV thanks to its aluminium struc - emerged as the metal of choice Duplex train was introduced, ture. Today, aluminium metros to lower running costs and to transporting 40% more passen - and trams operate in many cities improve acceleration of metros, gers while weighing 12% less and aluminium trains are used tramways, intercity and high than the single deck version, all all over the world. EUROPEAN ALUMINIUM ASSOCIATION ALUMINIUM IN COMMERCIAL VEHICLES CHAPTER II 11
In 1899, a small sports car with The average volume of alu - an aluminium body was unveiled minium used in passenger cars at the Berlin international car was already 131kg in 2005. exhibition. In 1948, Land Rover started using aluminium outer The same year, one car in every skin sheets. four produced in Europe had an aluminium bonnet and around Today, besides well-known alu - one third of European cars were minium-intensive cars like the already equipped with alu - Audi A8, many cars contain sig - minium bumper systems. Aluminium bonnet nificant amounts of aluminium.
Aluminium bumper system prepared for crash test 12 EUROPEAN ALUMINIUM ASSOCIATION ALUMINIUM IN COMMERCIAL VEHICLES CHAPTER II
2. Evolution of commercial vehicles
Having made its debut in Parisian minium tankers, vans and tipping charging bodies and a multitude buses in 1910, aluminium was vehicles. Today, most tankers and of components. Considering used for a variety of elements in silo semi-trailers are made entirely today’s European fleet, aluminium commercial vehicles in the 1930s. of aluminium. It is also frequently saves on average 800kg per artic - The 1950s saw the first alu - used for vans, tipping or self-dis - ulated vehicle.
TODAY 1976
1950 1930
First aluminium parts 1910 in Parisian buses EUROPEAN ALUMINIUM ASSOCIATION ALUMINIUM IN COMMERCIAL VEHICLES CHAPTER II 13
3. Aluminium applications 4. Today’s and weight savings concerns
Some examples… The key concern of transport companies is profitability.
The rising diesel price and the investment in new engine tech - nologies increase costs, while it is hard to increase transport prices due to the high competi - tion between operators.
Any investment must therefore have a very short payback time.
Consequently, vehicle manufac - turers must constantly improve l Components for tractors l Safety parts their performance at minimum & rigid trucks - front bumpers : -15kg costs. The choice of a material - cabin & door: -200kg - rear bumpers : -15kg will therefore depend on its - chassis: -350kg - side bumpers : -20kg price, its mechanical properties - powertrain parts: -125kg - front and rear under-run and its impact on vehicle pro - - suspension parts: -110kg protections duction costs. l Complete superstructures l Trailers sub-structures - rigid body: 90m2 = -800kg - chassis: 13.5m = -700kg From a society point of view, - tipping body: -800 to -2200kg - chassis: 6m = -300kg energy efficiency, reduction of - ADR fuel tank: 43000l = -1100kg - chassis+floor: 13,5m = -1100kg greenhouse gases and road - self-discharging body - legs: -35kg safety are in the priority list of - silo l Accessories European authorities. l Components - air pressure vessels: for superstructure 6x60l = -54kg Chapter III explains how alu - - curtain rails: 2x13.5m = -100kg - diesel tank: 600l = -35kg minium helps to take up these - front wall: -85kg - toolbox: -15kg challenges. - rear door: -85kg - tail lift: -150kg - side boards: 600mm = -240kg - wheels: 14 rims = -300kg - stanchions: 10x600mm = -50kg - reefer floor EUROPEAN ALUMINIUM ASSOCIATION CHAPTER III
WHY USING ALUMINIUM
1. SHORT PAY-BACK ...... 16 1.1. Increased payload + Higher residual value = Additional incomes ...... 16 1.2. Fuel saving + long life + reduced maintenance = Cost savings ...... 16 1.3. Make your own calculation on www.alutransport.eu ...... 16 1.4. Coping with road tolls ...... 17 1.5. Reduced risk of work accident ...... 17 2. ALUMINIUM PERFORMANCE PROPERTIES ...... 18 2.1. High strength-to-weight and high stiffness-to-weight ratios ...... 18 2.2. Durability ...... 19 2.3. Stability ...... 20 2.4. Diversity & functionality of semi-finished products, castings and forgings . . . . . 20 2.5. Easy to work with ...... 21 3. ENVIRONMENTAL AND SOCIAL BENEFITS ...... 22
3.1. Aluminium reduces CO 2 emissions ...... 22 3.2. Aluminium as a complement to EURO IV & EURO V engines ...... 22 3.3. Aluminium improves road safety ...... 23 3.4. Aluminium is easily and economically recycled ...... 24 4. ON THE ROAD … ...... 25 4.1. Looking good forever ...... 25 4.2. Aluminium is easy to repair ...... 26 16 EUROPEAN ALUMINIUM ASSOCIATION ALUMINIUM IN COMMERCIAL VEHICLES CHAPTER III
1. Short pay-back
1.1. Increased payload + Higher residual value = Additional incomes
Aluminium reduces dead vehicle Furthermore, used aluminium due to the fact that aluminium is weight. When transporting high- vehicles have a lot of success on easily recycled, without losing density freight, which usually sat- the second, and even third hand any of its quality and saving 95% urates the maximum gross vehi- market, where they are usually of the primary energy input. cle weight, aluminium allows the sold for a very good price. Finally, loading of more goods. This when they have reached the end translates into additional income of their long service life they still and/or better competitiveness. have a high scrap value. This is
1.2. Fuel saving + long life + reduced maintenance = Cost savings
A study conducted by the IFEU1 Aluminium’s well-known corro- in cooperation with the TU-Graz2 sion resistance is an obvious concluded that 1 ton saved on advantage in road transport: It the total weight of an articulated contributes to a long service life, truck leads to a fuel saving of 0.6 especially in vehicles which work litres /100 km. in conditions that can cause seri- ous corrosion problems. No This saving occurs during trips painting or other surface protec- made below the maximum gross tion is required and it is easy to vehicle weight, i.e. when trans- clean. Maintenance is therefore porting low-density goods, for kept to a minimum. partly loaded or empty trips.
1.3. Make your own calculation on www.alutransport.eu
Make your own payback calcula- and have a look at the example tion on www.alutransport.eu beside.
1. Institut für Energie und Umwelt Forschung, Heidelberg, Germany 2. Technical University of Graz, Austria EUROPEAN ALUMINIUM ASSOCIATION ALUMINIUM IN COMMERCIAL VEHICLES CHAPTER III 17
Road toll station
1.5. Reduced risk of work accident
1.4. Coping with road tolls In countries where road toll is Mobile parts that are manipu - limited to the heaviest vehicle lated at each delivery, like drop- According to the “user pays” category, “mini-semi-trailers” are side walls or rear doors, are principle, an increasing number built using a substantial amount lighter to move when made out of countries are introducing road of aluminium allowing the oper - of aluminium. This saves a lot of tolls that increase cost per kilo - ator to keep a good payload effort for the drivers. metre. On the other hand, while not exceeding the weight increasing payload with alu - limit where a toll is applicable. Using extrusions with rounded minium allows spreading this edges or folded sheets with round extra cost over a bigger tonnage corners for the floors of box vans of goods. reduces the risk of injuries.
Mini-trailer (Tang Fahrzeugbau GmbH) 18 EUROPEAN ALUMINIUM ASSOCIATION ALUMINIUM IN COMMERCIAL VEHICLES CHAPTER III
2. Aluminium performance properties
2.1. High strength-to-weight and high stiffness-to-weight ratios
Aluminium alloys used in com - No weight saving can be obtained To illustrate the upper and the mercial vehicles have strength- with aluminium if the design is lower limits of aluminium light- to-weight and stiffness-to- simply copied from steel. weighting, let’s analyze two weight ratios comparable with extreme equivalence philoso - the most advanced metals like Designs optimised for aluminium phies “equal strength” and high strength steel and titanium. are based on specific sections (20 “equal stiffness” to traditional to 40% higher beams), smooth chassis beam. These properties, among many transitions and clever joints, others, are taken into account which normally give 40-60% when designing a vehicle. weight saving over competing metals, as explained below.
Comparison of weight-optimised designs made with 3 different metals and 2 design criteria
DEFINITION Standard High strength Aluminium steel steel alloy Yield strength (MPa) 350 760 250 E-Modulus (MPa) 210000 210000 70000 Density (kg/m 3) 7800 7800 2700
EQUAL STRENGTH EQUAL STIFFNESS Standard High strength Aluminium Standard High strength Aluminium steel steel alloy steel steel alloy Strength 1=1=1Strength 1<2.17 > 1.54 Stiffness 1>0.30 < 0.56 Stiffness 1=1= 1 Weight 1>0.71 > 0.42 Weight 1=1> 0.55 Section height 1>0.65 < 1.18 Section height 1=1<1.40
Unfair comparison! EUROPEAN ALUMINIUM ASSOCIATION ALUMINIUM IN COMMERCIAL VEHICLES CHAPTER III 19
Unpainted aluminium patrol boat (All American Marine)
At equal strength: • The aluminium beam is the lightest, but has a lower stiffness than the standard steel beam. • The high-strength steel beam ranks second for lightness, but its stiffness is also the lowest! • The aluminium solution is about 60% lighter than the stan - dard steel one (0.42 vs. 1) and still 40% lighter than the high strength steel one (0.42 vs. 0.71).
At equal stiffness: • The aluminium beam is the (1.54 vs. 1) and a much higher 2.2. Durability lightest, with 45% weight saved stiffness (1 vs. 0.30). Some operators still fear prob - (0.55 vs 1). lems with aluminium trailer chas - • The high strength steel beam Last but not least, we should sis in heavy duty applications, weighs the same as the standard underline that further weight but they should know that the steel beam, because, based on optimisation is possible with alu - lifespan is not material related if the same parent metal, both minium because: properly designed. materials have identical elastic • The above comparison is properties (E-modulus). based on a standard beam Experienced manufacturers opti - • Compared to the standard steel design, the so-called “double T” mize their design for the material beam, the aluminium one is • Finite element modelling they use and are able to produce about 50% stronger, and the high allows a more precise definition aluminium chassis offering an strength steel one about 120%. of most favorable section’s equivalent or longer lifespan but geometry; at a much lower weight than Comparing an aluminium beam • These sections, even if very conventional models. designed for equal stiffness to a complex, can easily be produced standard steel beam and a high with the aluminium extrusion It is also important to underline strength metal beam designed for process. that aluminium vehicles often equal strength to that standard • For parts where strength is the operate in transport segments steel beam, only shows small leading criteria, high-strength where the load factors are the weight saving for aluminium aluminium alloys can also be highest (solid and liquid bulk, (0.55 vs. 0.71) but that compari - used and provide further weight public works etc…). In other son is unfair , as the latter will savings words, they are much more have a much higher strength intensively used than conven - 20 EUROPEAN ALUMINIUM ASSOCIATION ALUMINIUM IN COMMERCIAL VEHICLES CHAPTER III
tional ones, and this fact is taken into account in the design of alu - minium vehicles.
Correctly used, aluminium alloys have been developed to offer optimum corrosion resistance in all environments. Just one exam - ple: the widespread use of unpainted aluminium in marine applications.
2.3. Stability
Achieving IRTE 3 Class A 4 tipping stability standard for an alu - minium tipper chassis is no prob - lem. Aluminium, according to tests carried out in the summer of 2002 has no issues with flex - ing and easily provides the equiv - alent rigidity of steel. Tipping stability test (STAS) Indeed, a full-aluminium vehicle, significantly lighter than others, passed the IRTE Class A test at 44 2.4. Diversity & functionality of semi-finished products, tonnes with its standard chassis, castings and forgings reminding everyone that an appropriate design leads to both Vehicle designers and manufac - • Extruded semis: hollow or solid lightness and torsional stiffness. turers have a wide range of alu - shapes, standard or customized minium alloy semi-finished prod - • Castings and forgings ucts from which to choose: 3. Institute of Road Transport Engineers, • Rolled semis: sheets, tread UK. plates (floor plates), pre-painted 4. “Class A” standard states that a sheets trailer should be able to tilt sideways 7° without falling with a fully loaded and raised body. EUROPEAN ALUMINIUM ASSOCIATION ALUMINIUM IN COMMERCIAL VEHICLES CHAPTER III 21
Various aluminium products
This diversity of semi-finished 2.5. Easy to work with products makes it possible to: Aluminium alloys used in the • Design structural elements manufacture of commercial vehi - with special functions such as cles and their accessories are shapes with grooves for screw easy to process. They lend them - heads, hydraulic circuits, inertia selves to a variety of shaping and shapes, snap-locks, welding joining techniques that will be flanges etc. reviewed in chapters 7, 8 & 9. • Save on time and cost for assembly and finishing. This can In a nutshell, aluminium can compensate for the added raw easily be material cost of structures made • cut: sawing, shearing, water jet, from aluminium alloys compared laser or plasma cutting with equivalent steel structures. • machined: milling, drilling • Reduce stress due to welding • bent by placing castings at assembly • joined: welding, adhesive bond - intersections or using special ing, bolting and riveting extrusions to divert welding stresses into less stressed areas of Furthermore, being light, alu - a fabricated structure. minium is easy to handle in the • Design complex cast or forged workshop. shapes. 22 EUROPEAN ALUMINIUM ASSOCIATION ALUMINIUM IN COMMERCIAL VEHICLES CHAPTER III
3. Environmental and social Benefits
3.1. Aluminium reduces CO 2 emissions 3.2. Aluminium as a complement to EURO IV To achieve emission reductions, it ton saved on an urban bus saves & EURO V engines is not only important to develop between 1,700-1,900 liters of low-emission engines, but also to diesel fuel per 100,000 km. use them in the most rational The European Environment way possible. Saving weight with Taking primary production, use Directives for trucks date back to aluminium is a good way of stage and end-of-life recycling 1988, while the first standard achieving this objective as into account, life-cycle saving s limiting emissions of nitrogen explained below. have been estimated as follows: oxides (NOx) and particulates (PM) from heavy-duty diesel Aluminium contributes to the • 1kg of aluminium in today’s engines were introduced at the reduction of CO 2 emissions from average articulated truck saves beginning of the 1990’s. road transport as follows: 28kg of CO 2 • 1kg of aluminium in an urban The EURO IV and EURO V stan -
• When carrying heavy goods, it bus typically saves 40-45kg of CO 2 dards represent a dramatic reduc - increases the load capacity of tion of NO x and PM emissions. vehicles and therefore improves However, they also impose new transport performance, allowing combustion processes and more goods to be carried per exhaust after-treatment techni - trip. In this case, one ton saved ques representing an additional on the dead weight of an articu - weight-penalty up to 300kg. lated truck saves 1,500 liters of diesel fuel over 100,000 km. Using more aluminium compo - • When carrying voluminous nents allows the manufacturer to goods, it reduces the overall compensate for this weight weight, lowering fuel consump - penalty. The payload can there - tion per kilometer. In this case, fore be preserved and even one ton saved on the dead increased. weight of an articulated truck saves 600 liters of diesel fuel over 100,000 km. • When carrying passengers, it reduces the overall weight and lowers fuel consumption. One EUROPEAN ALUMINIUM ASSOCIATION ALUMINIUM IN COMMERCIAL VEHICLES CHAPTER III 23
Truck with crash-module
3.3. Aluminium improves road safety
In the context of its Road Safety crash energy per unit of weight Last but not least, extra safety Action Programme, the European than traditional systems. As a features always mean additional Commission is looking into the rule of thumb, the light-weight - weight, which can be balanced introduction of crash energy ing potential exceeds 40%. by replacing heavy materials by absorption criteria for trucks. The aluminium. aluminium industry has already For this reason, aluminium is very developed several solutions for well suited for front, rear and the automotive and railway sec - side bumpers. tors and would be ready to take Aluminium elements can also be up this challenge for trucks. used to improve the energy absorbing potential of front and Regarding metal deformation rear end under-run protection that energy-absorbing elements devices, and may also be used to undergo upon impact, alu - build soft deformable truck minium systems make it possible noses. to absorb significantly more 24 EUROPEAN ALUMINIUM ASSOCIATION ALUMINIUM IN COMMERCIAL VEHICLES CHAPTER III
Aluminium tipper on scrap yard (Galloo recycling)
3.4. Aluminium is easily and economically recycled
Unlike traditional vehicles that the motivation to sell to a scrap required to produce primary alu - are exported to end their life a merchant is very high and land- minium is not lost: it is “stored in long way from Europe, alu - filling is avoided. the metal”. minium-intensive trailers gener - ally spend their entire life in our Recycled aluminium does not continent, where they are even - loose any of its quality and saves 5. “The fate of aluminium from end-of- 5 tually dismantled . Due to the 95% of the primary production life commercial vehicles”, Université de high value of aluminium scrap, energy input. The energy Technologie de Troyes EUROPEAN ALUMINIUM ASSOCIATION ALUMINIUM IN COMMERCIAL VEHICLES CHAPTER III 25
8 years old aluminium tipping body re-used on a new truck
4. On the road…
4.1. Looking good forever ward matter to produce vans Aluminium is used to produce with rounded body corners both the lightest, the strongest and The modern commercial vehicle inside and out. the most beautiful wheels. cannot escape the pressures of industrial design. Operators want With tippers and self-discharging Last but not least, no corrosion their vehicles to look good with bodies, this makes for a smooth will appear after impact on alu - clean, pleasing lines, something unloading and easier cleaning. In minium parts, therefore preserv - which aluminium alloy semis are addition, using double wall alu - ing the image of the company. ideal for producing. minium extruded boards allows the preservation of a perfect For example, using functional exterior surface over the time. extrusions and plain or pre- Image conscious operators appre - painted aluminium sheet that is ciate this type of construction very easy to shape, it is a straightfor - much. 26 EUROPEAN ALUMINIUM ASSOCIATION ALUMINIUM IN COMMERCIAL VEHICLES CHAPTER III
Double wall extruded boards for tippers 4.2. Aluminium is easy to repair
Few people know that Land Rovers have had aluminium clo - sure panels since 1948, and in the last 50 years, nobody has ever complained about repair problems. This illustrates the fact that repair is possible, but alu - minium repair techniques are definitely different from those of steel. Leading chassis manufac - turers have set up a European dealer network where an effi - cient repair service is offered.
Forged aluminium wheel EUROPEAN ALUMINIUM ASSOCIATION ALUMINIUM IN COMMERCIAL VEHICLES CHAPTER III 27
Repair of an aluminium tipper (Benalu) EUROPEAN ALUMINIUM ASSOCIATION CHAPTER IV
FREQUENTLY ASKED QUESTIONS
1. ALUMINIUM ...... 30 1.1. What are the advantages of an aluminium vehicles? ...... 30 1.2. Is there an additional cost for an aluminium vehicle? ...... 30 1.3. What are the main benefits for the environment? ...... 30 1.4. Is it necessary to paint an aluminium vehicle? ...... 31 1.5. Is it possible to repair an aluminium vehicle? ...... 31 1.6. Does aluminium burn ? ...... 31 2. ALUMINIUM CHASSIS ...... 32 2.1. How is an aluminium chassis designed and what are the weight savings achievable? . 32 2.2. Are there different aluminium chassis designs? ...... 33 2.3. Is the life of an aluminium chassis shorter than a steel chassis? ...... 34 2.4. How does aluminium compete with high strength steel? ...... 34 3. ALUMINIUM TIPPERS ...... 35 3.1. Are there different aluminium tipping body designs? ...... 35 3.2. What about the wear resistance of aluminium tipping bodies ...... 35 3.3. What type of chassis is needed for an aluminium tipper body? ...... 36 3.4. What about tipping stability? ...... 36 4. ALUMINIUM TANKERS ...... 37 4.1. How should a tank for the transport of dangerous goods (ADR) be designed? . 37 4.2. Which alloys are suitable for ADR tanks? ...... 37 30 EUROPEAN ALUMINIUM ASSOCIATION ALUMINIUM IN COMMERCIAL VEHICLES CHAPTER IV
1. Aluminium Aluminium bodied truck
1.1. What are the advantages of an aluminium vehicles?
Truck fleet operators benefit from smaller fleets with less higher payload, the longer life from a better performance of staff, lower fuel bills and lower and the higher residual value of their fleet. road toll costs. the equipment these companies There is a significant payload can generate more profit by increase which makes the fleet Trailer rental companies can offer using state-of-the-art equipment. much more profitable. Another operators semi-trailers with a bet- fact is cost savings that result ter performance. Due to the
1.2. Is there an additional cost for an aluminium vehicle?
Yes, aluminium vehicles are slightly ference in detail, we can see that, is paid back after less than two more expensive than equivalent when heavy goods are trans- years. Make your own calculations steel designs. If we analyse the dif- ported, the additional investment on www.alutransport.eu.
1.3. What are the main benefits for the environment?
Aluminium contributes to the • When carrying voluminous Taking primary production, use reduction of CO2 emissions from goods, it reduces the overall stage and end-of-life recycling road transport as follows: weight, lowering fuel consump- into account, life-cycle savings • When carrying heavy goods, tion per kilometre. In this case, have been estimated1 that 1kg it increases the load capacity of one ton saved on the dead of aluminium in today’s aver- vehicles and therefore improves weight of an articulated truck age articulated truck saves transport performance, allowing saves 600 litres of diesel fuel 28kg of CO2. more goods to be carried per over 100,000 km. trip. In this case, one ton saved on the dead weight of an artic- ulated truck saves 1,500 litres of diesel fuel over 100,000 km.
1. CO2 reduction potential of aluminium for articulated trucks, EAA (European Aluminium Association), 2005 EUROPEAN ALUMINIUM ASSOCIATION ALUMINIUM IN COMMERCIAL VEHICLES CHAPTER IV 31
Repair of an aluminium tipper (Stas)
1.4. Is it necessary to paint an aluminium vehicle?
No, it is not. Aluminium with its ance. If an operator chooses to motivation to do so lies in hav - natural «alumina» layer has an pay extra money (and weight ing a fleet with a particular excellent protection perform - too!) for the paint finish, the branding.
1.5. Is it possible to repair an aluminium vehicle?
It is often said that aluminium 50 years nobody has ever com - Please refer to the Chapter XIV vehicles cannot be repaired, plained about repair problems. for detailed information. however this is totally wrong. This illustrates the fact that Few people know that Land repair is possible as for any Leading chassis manufacturers Rover cars have had an alu - other materials, but aluminium have set up a European dealer minium body since the end of repair techniques are definitely network where an efficient world war two, and in the last different from those of steel. repair service is offered.
1.6. Does aluminium burn?
NO, aluminium and its alloys and do not contribute to the Aluminium alloys will however are, under atmospheric condi - spread of fire. melt at around 650°C, but with - tions, totally non-combustible out releasing harmful gases. 32 EUROPEAN ALUMINIUM ASSOCIATION ALUMINIUM IN COMMERCIAL VEHICLES CHAPTER IV
2. Aluminium chassis
2.1. How is an aluminium chassis designed and what are the weight savings achievable?
Leading European trailer manu - sections (20 to 40% higher tional model. If this would be facturers are using strength, beams), smooth transitions and the sole criteria, the weight sav - stiffness and durability criteria. clever joints, which normally ing obtained with aluminium give 40-60% weight saving over would be maximized (up to No weight saving can be competing metals (see Chapter 60%) and high strength steel obtained with aluminium if III), as explained below. solutions would provide about design is simply copied from half the weight saving achiev - steel. Designs optimised for alu - 1) A good light-weight trailer able with aluminium (about minium are based on specific has to be as strong as a tradi - 30%).
Chassis for aluminium tipper (Benalu) EUROPEAN ALUMINIUM ASSOCIATION ALUMINIUM IN COMMERCIAL VEHICLES CHAPTER IV 33
Chassis for aluminium tipper (Leciñena) 2) A minimum stiffness is gener - ally required. • If this stiffness has to be equal with standard steel models, weight savings obtained with aluminium will be around 45% with a superior strength, but high strength steel cannot achieve any weight saving. • If the minimum stiffness required is lower than the one of standard steel models, weight savings obtained with aluminium will be somewhere between 45% & 60% and weight savings obtained with high strength 2.2. Are there different aluminium chassis designs? steel somewhere between zero and half of what can be Each manufacturer has its own seems to be a must, deflection is achieved with aluminium. design, which to a high degree the main criteria, and this gener - depends on the working condi - ally leads to longer lifetime than 3) Vehicles durability must be tions the vehicle is made for and conventional models, coupled insured. As aluminium vehicles on the specific manufacturing with an attractive weight saving. are much more intensively used experiences of the chassis pro - than conventional ones, their ducer (e.g. some prefer fully In other countries, equal lifetime resistance to fatigue must be welded constructions whereas with steel models will be the higher. This result is obtained others prefer mixed welded and main criteria. A good design will with a proper design. Among of bolted constructions). It is also lead to, at least, an equivalent a lot of others, higher sections, important to underline that alu - lifetime, stiffness within require - smooth transitions and clever minium vehicles are much more ments (even though it may be joints are keys to success. intensively used than conven - slightly lower than steel mod - tional ones, and this fact is els), but the weight saving will taken into account in the design be maximized. of vehicles. Apart from that, there are two dominating In any case, they will usually be design philosophies in the chas - stronger than classic models, sis world. and the risk for starting yield In countries like Italy, where failure from static overload will equal stiffness with steel models be lower for aluminium chassis. 34 EUROPEAN ALUMINIUM ASSOCIATION ALUMINIUM IN COMMERCIAL VEHICLES CHAPTER IV
Bolted aluminium chassis for tipper (Menci)
2.3. Is the life of an aluminium chassis shorter than a steel chassis?
The lifespan of a chassis is a design used in transport segments tanks, tippers), nevertheless well issue and not a material issue. where the load factors are the designed vehicles can easily Aluminium chassis are mostly highest (solid & liquid bulk exceed 20 years of service life.
2.4. How does aluminium compete with high strength steel?
We should make a distinction What is seldom communicated ness, the only solution is to between pure aluminium and is that all alloys based on the change the material e.g. switch - aluminium alloys. same parent metal have nearly ing from steel to aluminium (see Pure aluminium is never used in the same elastic properties. Chapter III). commercial vehicles. A wide variety of aluminium alloys do This means that if someone is exist, including high strength looking for a lightweight alter - solutions. native to a standard chassis while keeping the same stiff - EUROPEAN ALUMINIUM ASSOCIATION ALUMINIUM IN COMMERCIAL VEHICLES CHAPTER IV 35
3. Aluminium tippers
3.1. Are there different aluminium tipping body designs?
Yes, there are a lot of tipper productivity for manufacturers, more details, please have a look variants and all of them can be as well as increased payload, at Chapter VI. built using dedicated aluminium low running costs and a great semi-products that offer high fleet image to operators. For
3.2. What about the wear resistance of aluminium tipping bodies
The wear condition can vary Typical bottom plate material is: Typical values for bottom plate extremely from one load to • 5083 H32, H321, H34 thickness are listed below: another. Therefore it is not • 5086 H24 • 6 mm for light-duty opera - always possible to link the actual • 5383 H34 tions like agricultural products, hardness of an alloy to the wear • 5454 H22, H24 coal or sand transport resistance. It was found out that • 5456 H34 • 8 mm for medium-duty serv - for a very large extent, the type or other, mill-specific alloy types. ice like recycling products of load is a decisive factor. • 10 mm for heavy-duty trans - port like gravel The choice of material for the • Up to 12 mm in extreme cases construction of tipping trailers is nowadays often a question of Please refer to Chapter VI for specific experiences, material more details. availability and manufacturer’s specific production methods. 36 EUROPEAN ALUMINIUM ASSOCIATION ALUMINIUM IN COMMERCIAL VEHICLES CHAPTER IV
IRTE tipping stability test (STAS)
3.3. What type of chassis is needed for an aluminium tipper body?
Some operators still fear prob - related. Indeed, strength, like the same performance but at a lems with aluminium trailer stiffness and lifetime, are only much lower weight than con - chassis in heavy-duty applica - design criteria. Experienced ventional steel models. tions, but they should know manufacturers are able to pro - that strength is not material duce aluminium chassis offering
3.4. What about tipping stability?
It is often said that achieving ing summer 2002 confirmed to both lightness and torsional the IRTE 2 Class A 3 tipping sta - that both statements were stiffness. bility standard for an alu - totally wrong. minium tipper chassis would be difficult simply because "it Indeed, a full-aluminium vehicle, 2. British Institute of Road Transport flexes too much" or that, to significantly lighter than others, Engineers (IRTE) provide the equivalent rigidity passed the IRTE Class A test at 3. IRTE's "Class A" stability standard of a steel chassis "the lightness 44 tonnes with its standard for tipping on uneven ground states that a trailer should be able to tilt side - benefit would be practically chassis reminding everybody ways 7° without falling with a fully eliminated", but tests run dur - that an appropriate design leads loaded and raised body. EUROPEAN ALUMINIUM ASSOCIATION ALUMINIUM IN COMMERCIAL VEHICLES CHAPTER IV 37
4. Aluminium tankers
4.1. How should a tank for the transport of dangerous 4.2. Which alloys are goods (ADR) be designed? suitable for ADR tanks?
Tanks for the transport of dan - pressure not exceeding 0.5 bar - Suitable aluminium alloys for gerous goods have to be built Design and construction” that application are listed in according to the rules defined in • EN 14025 “Tanks for the standard EN 14286 “Aluminium the following agreement and transport of dangerous goods - and aluminium alloys - weldable standards: Metallic pressure tanks - Design rolled products for tanks for the • ADR: Agreement for the and construction” storage and transportation of transport of Dangerous goods dangerous goods” as well as in by Road 4 More details are given in chapter V. • EN 13094 “Tanks for the Chapter VI. Aluminium suppliers are listed in transport of dangerous goods - the “links” section of the web - Metallic tanks with a working site www.alutransport.org .
4. See ADR, Annex A, Part 6, Chapter 6.8 : http://www.unece.org/trans/danger/danger.htm
Aluminium road tanker (Schrader) EUROPEAN ALUMINIUM ASSOCIATION CHAPTER V
ALUMINIUM ALLOYS FOR COMMERCIAL VEHICLES
1. FOREWORD ...... 40 2. INTERNATIONAL PRODUCT DESIGNATION ...... 41 3. BASIC TEMPER DESIGNATIONS ...... 42 4. SUBDIVISIONS OF H TEMPER DESIGNATIONS ...... 42 5. SUBDIVISION OF T TEMPER DESIGNATIONS ...... 43 6. TYPICAL ALLOYS FOR COMMERCIAL VEHICLES ...... 44 6.1. Flat rolled products ...... 45 6.2. Extruded products (forged products) ...... 46 6.3. Castings ...... 48 6.4. Selection guide for the different alloys (indicative) ...... 49 7. INFLUENCE OF TEMPERATURE ON MECHANICAL PROPERTIES ...... 50 7.1. Elevated temperature ...... 51 7.2. Low and very low temperatures ...... 51 8. INFLUENCE OF FABRICATION ON THE PROPERTIES OF THE ALLOYS ...... 52 8.1. Work hardening of non-heat treatable alloys ...... 52 8.2. Softening by annealing and recovery ...... 52 8.3. Heat treatable alloys ...... 53 8.4. Castings ...... 54 9. LIST OF STANDARDS ...... 55 40 EUROPEAN ALUMINIUM ASSOCIATION ALUMINIUM IN COMMERCIAL VEHICLES CHAPTER V
1. Foreword
Aluminium in its pure form is a ties can be varied in a great over the world. Company spe - very soft metal and hence not range making it possible to have cific trade names are often com - suited for structural applica - suitable alloys for literally all plemented by the standardized tions. Thanks to the addition of applications. designation. alloying elements such as cop - per, manganese, magnesium, As the Aluminium Industry is a All relevant standards are listed zinc etc… and thanks to ade - global industry there is the enor - at the end of this chapter. quate production processes, the mous chance, that the product physical and mechanical proper - designation is uniform almost all
Aluminium rolling mill EUROPEAN ALUMINIUM ASSOCIATION ALUMINIUM IN COMMERCIAL VEHICLES CHAPTER V 41
2. International product designation
In order to identify the various A list of all standardized cast case of pure aluminium the last alloys, 4-digit numbers have alloys can be found in EN 1706. two digits of the 4-digit number been standardized for wrought A selection of alloys for use in indicate the percentage of purity alloys (see EN573-1) and 5-digit commercial vehicles will be pre - above 99.0%. E.g. 1070 means numbers for cast alloys. sented in section 6. aluminium with at least 99.70% A list of all registered wrought The first digit of the alloy num ber of aluminium or, in other words alloys and their chemical composi - indicates the dominant alloying less than 0.30% impurities. tion can be found in EN 573-3 for element; the remaining digits are Europe and in the so-called “Teal just numbers for identification sheets 1” at international level. purposes (Table V.1). Just in the
TABLE V.1 CATEGORIES OF ALUMINIUM ALLOYS Dominant alloying element wrought alloy cast alloy None (“pure aluminium”) 1xxx Copper 2xxx 2xxxx Manganese 3xxx Silicon 4xxx 4xxxx Magnesium 5xxx 5xxxx Magnesium and Silicon 6xxx Zinc and Magnesium (with or without copper) 7xxx 7xxxx Other elements (e.g. Iron or Lithium) 8xxx
From these eight categories are cates that it is an experimental aluminium plant and on the trans - three families so called “non heat alloy, or followed by a letter A formation process of the semi- treatable“, or “work hardening” which says that this is a national fin ished to the finished product. alloys (1xxx, 3xxx, 5xxx) and four variation of the basic alloy. These processes are characterized “heat treatable alloys” (2xxx, with the so called “temper desig - 4xxx, 6xxx, 7xxx). The 8xxx family The physical and mechanical nation” which attends the alloy cannot be attributed to one or properties of these alloys not only number. When alloy number and the other group. depend on their chemical compo - temper designation are indicated, The alloy number can be pre - sition but also to a great extent on the metal is clearly identified and ceded by a letter X which indi - the manufacturing process in the its properties defined.
1. The latest edition of the Teal Sheets is available for free download from the EAA website http://www.eaa.net/en/about-aluminium/standards/international-registra tion/ 42 EUROPEAN ALUMINIUM ASSOCIATION ALUMINIUM IN COMMERCIAL VEHICLES CHAPTER V
3. Basic temper designations
• F - as fabricated: this condi - work-hardening or by hot rolling • T - heat treated: heat treat - tion designates products made by at temperatures above the ment can combine some or all of plastic deformation without any recrystallisation temperature. the following operations: solu - particular control of the rates of • H - strain-hardened and pos - tion treatment, quenching, age hardening or softening by defor - sibly partially softened: this hardening, artificial ageing and mation or any heat treatment. relates to strain-hardened prod - possible plastic deformation. • O - fully annealed: this con - ucts with or without subsequent For more details, please refer to dition is the most ductile and is holding at a temperature high EN 515. obtained by the process of anneal - enough to induce partial soften - ing without any subsequent ing of the metal.
4. Subdivisions of H temper designations
The first digit after H indicates hardened and whose mechanical approximately midway between the specific combination of basic properties are stabilized either by that of the O temper and that of operations: a low temperature heat treat - the HX8 tempers. • H1X: work-hardened only. ment or as a result of heat intro - • HX2 designates tempers These designations identify prod - duced during fabrication. whose ultimate tensile strength ucts that are work-hardened For more details, please refer to is approximately midway between to obtain the desired strength EN 515. that of the O temper and that of without supplementary heat The second digit following the the HX4 tempers. treatment. letter H indicates the final degree • HX6 designates tempers • H2X: work-hardened and par - of strain hardening, as identified whose ultimate tensile strength is tially annealed. These designa - by the minimum value of the ulti - approximately midway between tions apply to products which are mate tensile strength. that of the HX4 tempers and that work-hardened more than the • 8 has been assigned to the hard - of the HX8 tempers desired final amount and then est temper normally produced. • HX1, HX3, HX5, HX7 designate reduced in strength to the • Tempers between O (annealed) tempers intermediate between desired level by partial annealing. and HX8 are designated by those defined above. Note: These • H3X: work-hardened and sta - numerals 1 to 7. temper designations are not bilized. These designations apply • HX4 designates tempers included in EN 515. Mechanical to products which are work- whose ultimate tensile strength is properties of these tempers shall EUROPEAN ALUMINIUM ASSOCIATION ALUMINIUM IN COMMERCIAL VEHICLES CHAPTER V 43
Extrusion press be agreed between the manufac - • H112 applies to products that Products are strain hardened at turer and the customer. may acquire some strain-hardening the last operation to specified The third digit , when used, indi - from working at an elevated tensile property limits and meet cates a variation of a two-digit temperature or from a limited specified levels of corrosion temper. amount of cold work, and for resistance in accelerated type • HX11 applies to products that which there are no upper corrosion tests. Corrosion tests incur sufficient strain-hardening after mechanical property limits. include inter-granular and exfoli - the final annealing such that they fail • H116 applies to products, ation. This temper is suitable for to qualify as annealed but not so made of those alloys of the 5XXX continuous service at tempera - consistent an amount of strain-hard - group in which the magnesium tures not higher than 65°C. ening that they qualify as HX1. content is 3% nominal or more.
5. Subdivision of T temper designation s
The first digit following the let - to a substantially stable condition • T7: Solution heat-treated and ter T is used to identify the spe - • T3: Solution heat-treated cold- over-aged/stabilized cific sequences of basic treat - worked, and naturally aged to a • T8: Solution heat-treated, cold ments. Numerals 1 to 10 have substantially stable condition worked and then artificially aged been assigned as follows: • T4: Solution heat-treated and • T9: Solution heat-treated, artifi - • T1: Cooled from an elevated naturally aged to a substantially cially aged and then cold-worked temperature shaping process and stable condition • T10: Cooled from an elevated naturally aged to a substantially • T5: Cooled from an elevated temperature shaping process, stable condition temperature shaping process and cold-worked, and then artificially • T2: Cooled from an elevated then artificially aged aged. temperature shaping process, • T6: Solution heat-treated and For more details, please refer to cold-worked, and naturally aged then artificially aged EN 515. 44 EUROPEAN ALUMINIUM ASSOCIATION ALUMINIUM IN COMMERCIAL VEHICLES CHAPTER V
6. Typical alloys for commercial vehicles
Out of the vast variety of known • availability of semi-finished In the following tables the most alloys as listed in EN 573-3 and products widely used alloys for the appli - in the Teal Sheets, just a few are • mechanical properties cation in commercial vehicles of importance for the manufac - • physical properties are presented. ture of commercial vehicles. • suitability for fabrication Selection criteria are: • weldability • corrosion resistance
Aluminium coils EUROPEAN ALUMINIUM ASSOCIATION ALUMINIUM IN COMMERCIAL VEHICLES CHAPTER V 45
Aluminium rolling slabs
6.1. Flat rolled products TABLE V.2 REFERENCE STANDARDS FOR MECHANICAL PROPERTIES OF WROUGHT ALLOYS – FLAT ROLLED PRODUCTS In commercial vehicles, the most commonly used alloys are 3003, Alloy Standards 2 5005, 5059, 5083, 5086, 5088, 3003 EN 485-2 5182, 5186, 5383, 5454, 5456, 5005 EN 485-2 5754, 6061 and 6082. 5059 EN 485-2 and EN14286 5083 EN 485-2 and EN14286 The mechanical properties of 5086 EN 485-2 and EN14286 these alloys can be found in the 5088 EN 485-2 and EN14286 standards listed in Table V.2 and 5182 EN 485-2 and EN14286 Table V.3 gives indications on 5186 EN14286 engineering suitability. 5383 EN 485-2 and EN14286 5454 EN 485-2 and EN14286 5754 EN 485-2 and EN14286 6061 EN 485-2 6082 EN 485-2
2. See standards denominations at the end of this chapter section 9. 46 EUROPEAN ALUMINIUM ASSOCIATION ALUMINIUM IN COMMERCIAL VEHICLES CHAPTER V
TABLE V.3 ENGINEERING SUITABILITY FOR ROAD TRANSPORT APPLICATIONS – FLAT ROLLED PRODUCTS
Alloy Temper Shaping Welding Anodizing Corrosion resistance 3003 H14,H24,H16 BAAA 5005 H14,H24 B A AA 5059 O, H111 BAAA 5083 O,H111 AAAA H116,H22,H24, H34 CAAA 5086 O,H111 AAAA H116,H22,H24 CAAA 5088 O, H111 AAAA 5182 O, H111 AAAA 5186 O, H111 AAAA 5383 H22, H32 BAAA 5454 O,H111 AAAA H22,H24 BAAA 5456 H34 CAAA 5754 O,H111 AAAA H22,H24 BAAA 6061 T4 CAAA T6 D AA A 6082 T4 CAAA T6 DAAA
A = very good; B = good; C = fair; D = poor, to be avoided EUROPEAN ALUMINIUM ASSOCIATION ALUMINIUM IN COMMERCIAL VEHICLES CHAPTER V 47
Aluminium extrusion billets
6.2. Extruded products TABLE V.4 (forged products) ENGINEERING SUITABILITY – EXTRUDED & FORGED PRODUCTS Alloy Temper Welding Anodizing Corrosion resistance In commercial vehicles, the most 6060 all AA A commonly used alloys are 6060, 6005A all AA A 6005A, 6008, 6106, 6082, 6008 all AA A 6061 and 7020. 6106 all AA A 6082 all AA A The mechanical properties of 6061 all AA A these alloys can be found in 7020 T6 AA C standard EN 755-2 and Table V.4 7003 T6/T7 AA B gives indications on their engi - 7108 T6/T7 AA B neering suitability. A = very good; B = good; C = fair; D = poor, to be avoided 48 EUROPEAN ALUMINIUM ASSOCIATION ALUMINIUM IN COMMERCIAL VEHICLES CHAPTER V
Semi-trailer chassis beam made out of two extruded flanges and a sheet as web
Extruded rail for sliding curtain
6.3. Castings
In commercial vehicles, the most commonly used alloys are 21100, 42000, 42100, 43000, 44000. Their chemical composition and mechanical properties can be found in standard EN 1706 and Table V.5 reflects their casting characteristics.
TABLE V.5 CASTING CHARACTERISTICS Alloy Fluidity Resistance to Pressure Machinability Corrosion hot tearing tightness resistance 21100 CDD AD 42000 BABBB/C 42100 BABBB 43000 AAB BB 44000 AAACB
A = very good; B = good; C = fair; D = poor, to be avoided EUROPEAN ALUMINIUM ASSOCIATION ALUMINIUM IN COMMERCIAL VEHICLES CHAPTER V 49
6.4. Selection guide for the different alloys (indicative)
Alloy, temper Van body Curtainsider body 3003*, 5005*, 5052*
6005 T6, 6005A T6, 6063A T6
6060 T6, 6063 T6
*coated sheets Alloy, temper Tipper or self-discharging Tipper with ribbed sides 6005 T6, 6005A T6, 6005A T5 6005 T6 body with smooth sides 6060 T5/T6 6063 T6 6005AT6 5083 H111, 5754 H111
5083 H34/H32/H321 • 5086 H24 5383 H34 • 5454 H22/H24 in case of self-discharging floor 5456 H34 Tank for liquid bulk Alloy (O/H111 for all) Silo for solid bulk
5083, 5086, 5383, 5454, 5754
5182, 5186, 5059, 5088
do not allow weight optimization of ADR tanks
Alloy, temper Chassis beam: Chassis beam: two profiles 6005A T5/T6, 6082 T6 one single profile one plate 5083 H111/H34 5086 H111/H24 5456 H34
OTHER APPLICATIONS
Wheels ...... 6061, 6082 Bumper beams, crash boxes Diesel fuel tanks ...... 5052, 5754 & roll over protections ...... 7003, 7108 Tail lifts ...... 6005A Suspension parts ...... 21100 Floors ...... 6082, 5086, 5754 Structural components-Hinges-Supports . .42000, 42100 Framing for buses ...... 6060, 6005A Complex shapes with medium strength ...... 43000 Sides & roofs for buses ...... 3003, 5005 Very complex shapes Crash modules ...... 6008 without structural function ...... 44000
Beside these well known alloys eration with the supplier of the offer best performance for the it is possible to define, in coop - semis, tailor made products that foreseen purpose. 50 EUROPEAN ALUMINIUM ASSOCIATION ALUMINIUM IN COMMERCIAL VEHICLES CHAPTER V
7. Influence of temperature on mechanical properties
Aluminium alloys change their TABLE V.6 mechanical and corrosion resist - CHANGE IN MECHANICAL PROPERTIES OF 5086 O AFTER ance properties when subjected HOLDING AT TEMPERATURE FOR 10,000 HOURS to temperatures other than Temperature Mechanical properties (*) ambient temperature. Tables V.6 °C Rm (MPa) Rp 0,2 (MPa) A% & V.7 show the interrelationship -196 390 140 34 between service temperature -80 280 120 26 and mechanical properties. In -28 270 120 24 Figure V.1 this is shown for one +20 270 120 22 alloy graphically. +100 270 120 26 +150 210 110 35 +200 155 105 45
TABLE V.7 CHANGE IN MECHANICAL PROPERTIES OF 6082 T6 AFTER HOLDING AT TEMPERATURE FOR 10,000 HOURS Temperature Mechanical properties (*)
°C Rm (MPa) Rp 0,2 (MPa) A% -196 380 330 16 -80 330 295 13 -28 330 285 12 +20 320 285 12 +100 300 265 15 +150 240 220 18 +200 130 105 28
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8. Influence of fabrication on the properties of the alloys
8.1. Work hardening of 8.2. Softening recrystallization and annealing. non-heat treatable alloys by annealing and recovery This growth is revealed during subsequent working, e.g. fold - Hardening is achieved by cold It is possible to restore the ductil - ing, by the rough “orange peel” deformation, known as work ity of the work hardened metal by effect on the surface of the hardening, that improves the heat treatment known as metal. Grain growth above physical properties and the hard - “annealing ” (partial or full around 100 microns reduces the ness of the metal. It also reduces annealing). In this process, which deformation capacity of work the metal’s capacity for deforma - takes place at temperatures hardening aluminium alloys. tion and its ductility (Figure V.2). between 150°C and 350°C, the The following conditions are The greater the deformation or hardness and mechanical charac - essential if a fine-grained annealed higher the work hardening rate, teristics of the metal slowly begin structure is to be achieved: the more pronounced is the to decrease: this is the recovery • The metal must have under - effect. It is also governed by the phase [A-B] (Figure V.3). At lower gone a sufficient rate of defor - composition of the material. annealing temperatures this leads mation corresponding to a rela - The 5083 alloy, for example, to medium-strength material which contains between 4 and properties. They then fall away FIGURE V.2 4.9% of magnesium, acquires a more rapidly at high temperatures WORK HARDENING CURVE OF ALLOY 5083 great hardness but its capacity above 280 °C during recrystal - for deformation is less than that lization [B-C] and eventually MPa A% ‰ of the 5754 alloy which contains attain a minimum value that cor - 500 between 2.6 and 3.6% Mg. responds to the mechanical char - Work hardening is a general phe - acteristics of the fully annealed Rm nomenon that takes place what - metal [C-D]. 400 30 R ever the method of deformation Restoration and annealing are p0,2 used: rolling, deep drawing, fold - accompanied by a change in the 300 20 ing, hammering, bending, press - texture and size of the grains of ing, etc. This means that it will metal observed under a micro - 200 10 also occur during fabrication in scope with X50 magnification. A the workshop. The texture can change from a fibrous structure to a fully recrys - 100 ‰ tallized structure (Figure V.3). Temper 0 H12 H14 H16 H18 Work hardening % 10 20 30 40 50 60 70 80 The grain can grow in size during EUROPEAN ALUMINIUM ASSOCIATION ALUMINIUM IN COMMERCIAL VEHICLES CHAPTER V 53
FIGURE V.3 tive reduction in section of at HARDNESS CURVE DURING ANNEALING least 15%. This is “critical work hardening”. If this condition is Micrographic views not met, then heat treatment must be restricted to restoration without recrystallization, • A rapid temperature gradient of 20 to 60°C per hour, A • Temperatures over 350 to s Recovery s B e
380°C must be avoided, n d r • Holding times must be limited a H to 2 hours maximum. Recrystallization C Annealing D For 5000 series alloys, annealing is usually performed between 320°C O Time and 380°C for 30 to 120 minutes.
Note: Non-heat treatable alloys in the annealed temper (O, H111) TABLE V.8 ( typical ) can only be brought to higher 6000 SERIES ARTIFICIAL AGEING strength by work hardening. Alloy Initial temper Artificial ageing Final Temper* 6060 T1 - T4 6hat 185°C T5 - T6 8.3. Heat treatable alloys or 8 h at 175°C If some plastic deformation must 6005 T1 - T4 8hat 175°C T5 - T6 be done on products of heat 6106 T1 - T4 8hat 175°C T5 - T6 treatable alloys, it should be car - 6061 T4 8hat 175°C T6 ried out in the T4 temper; first the 6082 T1 - T4 16 h at 165°C allowable degree of deformation or 10 h at 170°C T5 - T6 is bigger than for the T6 temper or 8 h at 175°C and second there is a moderate effect of work hardening. If for * T5, for an initial temper of T1, T6 for an initial temper of T4. the final product e.g. a bent extrusion in a 6XXX alloy T6 tem - per is needed, age hardening can be carried out. Table V.8 gives an indication how to proceed, using typically a hot air furnace. 54 EUROPEAN ALUMINIUM ASSOCIATION ALUMINIUM IN COMMERCIAL VEHICLES CHAPTER V
Flywheelhouse casting for truck engine (Brabant Alucast)
8.4. Castings
Casting is the shortest path from molten metal to the fin - ished product. It is recom - mended for geometrically-com - plex parts. It is advantageous to involve the foundry from the conceptual phase into the design process. The expert of the foundry, knowing the plants equipment, the process of mak - ing the mould, the flow of metal because of the wearing of the • For the same reason, isolated into the mould, the cooling and cutting tools due to the high sil - bosses should be avoided and shrinking of the cast piece etc. icon content of the alloys. walls must be correctly sized to can be of great help during the The corrosion resistance of cast assist running, design phase. When the design pieces with the as-cast surface is • There should be a fillet at of a casting is optimized in view better than for machined sur - every inside corner to avoid of its production it is in most faces of the same piece due to cracking during the casting cases possible for the foundry to the much thicker oxide layer. operation (this is particularly guarantee much better mechan - important for 21100 alloys), ical properties than those listed Design of casting parts • The filling design should be in standard EN 1706, especially Generally speaking it is essential somewhat asymmetrical to with respect to elongation. to be aware of production pos - ensure controlled solidification sibilities and limitations from the and uniform feed, The Table V.5 (see section 6.3) initial development stage of a • The number of intersections merits some explanation. new component, not just in and undercuts should be kept to The alloy 21100 needs very terms of the choice of alloy and a minimum as they complicate careful design of the pieces with casting technique but also in tooling and the casting opera - respect to the casting process terms of design. There are a tion and hence increase the and, in addition to that, the number of basic rules which cost. This applies equally to metal treatment in the foundry, designers should follow: deburring operations, especially the degassing of the • Sections should be kept uni - • The choice of dimensional molten metal, must be carried form and thickness transitions tolerances must allow for the out very carefully in order to should be smooth, avoiding a casting technique and any sub - minimize micro-porosity. build-up of metal at intersections sequent heat treatment defor - The index B or C in the column so as to reduce the risk of shrink - mation can occur during solu - “Machinability” has been put age porosity during cooling, tion treatment and quenching. EUROPEAN ALUMINIUM ASSOCIATION ALUMINIUM IN COMMERCIAL VEHICLES CHAPTER V 55
9. List of standards
• EN 485 Aluminium and aluminium alloys – Sheet, strip and plate Part 1: Technical conditions for inspection and delivery Part 2: Mechanical properties Part 3: Tolerances on dimensions for hot rolled products Part 4: Tolerances on dimensions for cold rolled products
• EN 515 Aluminium and aluminium alloys – Wrought products – Temper designations
• EN 573 Aluminium and aluminium alloys – Chemical composition and form of wrought products Part 1: Numerical designation system Part 2: Chemical based designation system Part 3: Chemical composition Part 4: Forms of products
• EN 755 Aluminium and aluminium alloys – Extruded rod/bar, tube and profiles Part 1: Technical conditions for inspection and delivery Part 2: Mechanical properties Part 3: Round bars, tolerances on dimensions and form Part 4: Square bars, tolerances on dimensions and form
• EN 1706 Aluminium and aluminium alloys – Castings – Chemical composition and mechanical properties
• EN 12392 Aluminium and aluminium alloys – Wrought products – Special requirements for products intended for the production of pressure equipment
• EN 14286 Aluminium and aluminium alloys – Weldable rolled products for the storage and transport of dangerous goods
Registration record series Teal Sheets : International alloy designations and chemical composition limits for wrought aluminium and wrought aluminium alloys available for free download from the EAA web - site: http://www.eaa.net/en/about-aluminium/standards/international-registration/ EUROPEAN ALUMINIUM ASSOCIATION CHAPTER VI
DESIGN AND CALCULATION
1. INTRODUCTION ...... 57 2. POSSIBILITIES WITH ALUMINIUM ...... 58 3. SYMBOLS ...... 58 4. ALUMINIUM VERSUS STEEL ...... 58 5. LIMIT STATE DESIGN ...... 62 5.1. Philosophy ...... 62 5.2. What is the ultimate limit state ...... 62 5.3. What is the serviceability limit state ...... 62 6. SERVICEABILITY LIMIT STATE ...... 63 7. ULTIMATE LIMIT STATE ...... 64 7.1. Cross section classes ...... 64 7.2. Load bearing resistance ...... 64 7.3. Welded connections ...... 69 7.4. Bolted connections ...... 73 8. FATIGUE ...... 76 8.1. Theory ...... 76 8.2. Practice: comparison between good and bad chassis solutions ...... 82 9. SPECIAL DESIGN ISSUES ...... 86 9.1. Tanks for the transport of dangerous goods - ADR ...... 86 9.2. Tippers ...... 87 10. REFERENCES ...... 89 58 EUROPEAN ALUMINIUM ASSOCIATION ALUMINIUM IN COMMERCIAL VEHICLES CHAPTER VI
1. Introduction 2. Possibilities 3. Symbols with aluminium The new European design code Frequently used symbols are for aluminium structures is used defined in this section: as a basis for this chapter. The The advantages of designing fo characteristic value of 0.2 % name of this standard is: with aluminium are: proof strength
EN 1999 Eurocode 9: Design of • High strength-to-weight ratio fu characteristic value of ulti - aluminium structure • Possibilities to create your own mate tensile strength
cross-sections with the extrusion fub characteristic ultimate tensile Part 1-1 General structural rules technique strength of bolt Part 1-2 Structural fire design • Good corrosion resistance E modulus of elasticity Part 1-3 Structures susceptible to • Long vehicle life d bolt diameter
fatigue • Easy to work with do hole diameter Part 1-4 Cold-formed structural • Easy to repair t wall thickness sheeting A cross section area Part 1-5 Shell structures Especially for product design, the W section modulus
use of tailor-made profiles is a γM partial safety factor for resist - Part 1-1 is used for all static great advantage for aluminium ance (see the definitions in sec - design and Part 1-3 for all compared with other metals. In tion 5.2), in EN 1999-1-1: fatigue design shown in this profile design the material can be chapter. placed where the effect of the Subscript Ed is used for factored A new European standard for the material is optimal regarding load effects. It may be on axial execution of structural alumini - resistance. Details can be made force (N Ed ), bending moment um is under development and is in such a way that it will ease the (M Ed ), shear force (V Ed ), torsion soon ready for publication. It is fabrication and assembling of (T Ed ) and forces in connection recommended to use relevant the components. with bolted connections (F v,Ed for parts of this standard for execu - shear force and F t,Ed for tension tion of aluminium components force). for use in commercial vehicles. The name of this standard is: EN 1090-3: Execution of steel structures and aluminium struc - tures – Part 3: Technical require - ments for aluminium structures EUROPEAN ALUMINIUM ASSOCIATION ALUMINIUM IN COMMERCIAL VEHICLES CHAPTER VI 59
4. Aluminium versus Steel
Both steel and aluminium are member will get twice the ther - steel struc ture and check after - metals with relatively high mal elongation as a similar steel wards whether the deflection is strength. Both materials are member with the same tempera - within the requirement. incombustible and will not con - ture difference. Since the elastic When designing an aluminium tribute to a fire. For structural modulus of aluminium is 1/3 of structure, it will often be the purposes the main differences ste el, the stresses in an aluminium deflection criterion that will be are: member with fixation are 2/3 of governing. For that reason, the Elasticity: The modulus of elas - that in a similar steel member. design procedure will start with ticity (E-modulus) of aluminium is the deflection criterion and it will 1/3 of that of steel. This means Most of the structural aluminium be checked afterwards if the that an aluminium beam with alloys have relatively high stress or the resistance of the the same cross-section and the “strength-to-E modulus” ratio. structure is within the limits. same loads as a steel beam will This effect is especially clear The deflection of members under have a deflection 3 times that of when the aluminium alloy is bending load depends on the the steel beam. strain-hard ened or heat-treated. modulus of elasticity (E) and on Weight: The density of alumini - Structural aluminium alloys have the moment of inertia (I) togeth - um is 1/3 of that of steel. This roughly twice the “strength-to-E er with the load and the span. means that a steel beam will modulus” ratio than standard steel. With the same span and load, it weigh 3 times more than an alu - However, when compared with will be the product E x I that will minium beam with the same high strength steels, structural determine the deflection. cross-section. aluminium alloys have about the To get the same deflection of Welding: When welding a hard - same “strength-to-E modulus” steel and aluminium beams in ened aluminium alloy some of ratio. It should also be noted that bending, the moment of inertia the hardening effects will be lost. the elastic modulus of an alloy of the aluminium beam must be The strength in the heat affected mainly depends on its parent three times that of steel. If the zone (HAZ) will be reduced. This metal. In other words, all alu - increase in the moment of inertia reduction depends on the alloy, minium alloys have very similar E- is to be done only by increasing temper, type of product and modulus, but this is also valid for the thickness of the web and welding procedure. Ordinary steel alloys. Consequently, the so flanges, the aluminium beam will steel has no strength reduction called “high strength steels” have the same weight as the after welding. don’t have better elastic proper - steel beam. Thermal elongation: The coef - ties than mild steel. ficient of thermal elongation of Steel designers often use the aluminium is twice that of steel. strength of the material as gov - This means that an aluminium erning criteria when desig ning a 60 EUROPEAN ALUMINIUM ASSOCIATION ALUMINIUM IN COMMERCIAL VEHICLES CHAPTER VI
To save weight, the aluminium If the height of the aluminium An I 330 x 200 x 6 x 10 will have beams in bending have to be alloy beam shall be 240 mm, this a moment of inertia of higher. An example will illustrate will be satisfied by an I-beam of I = 117.3 · 10 6 mm 4 this: I 240 x 240 x 12 x 18.3 and a mass = 15.8 kg/m An aluminium beam shall have which has a moment of inertia which give a weight saving of 49%. the same deflection as an IPE and the mass of These three different aluminium 240 steel beam. The moment of I = 116.6 · 10 6 mm 4 beams will give the same deflection inertia and the mass of the IPE mass = 30.3 kg/m as an IPE 240 steel beam. It will be 240-beam are If the height of the aluminium the shape and stability of the beam I = 38.9 · 10 6 mm 4. alloy beam can be 300 mm, the that will determine the weight of mass = 30.7 kg/m. deflection criteria will be satisfied the beam. Table VI.1 shows the The aluminium beam must have by an I 300 x 200 x 6 x 12.9 beams and the weight savings. a moment of inertia of which has a moment of inertia of I =116.7 · 10 6 mm 4 I = 116.7 · 10 6 mm 4 to get the same deflection. and a mass =18.4 kg/m which is a weight saving of 40%.
TABLE VI.1 Steel Aluminium Aluminium Aluminium ‰ ‰ ‰ t h
w ‰ ‰ ‰
‰ ‰ b
Moment in inertia in mm 4 38.9 10 6 116.6 10 6 116.7 10 6 117.3 10 6 E x I (N/mm 2) 8.17 10 12 8.16 10 12 8.17 10 12 8.21 10 12 h (mm) 240 240 300 330 b(mm) 120 240 200 200 w (mm) 6.2 12 66 t (mm) 9.8 18.3 12.9 10 Unit weight (kg/m) 30.7 30.3 18.4 15.8 Weight in % of the steel beam 100 % 99 % 60 % 51 % EUROPEAN ALUMINIUM ASSOCIATION ALUMINIUM IN COMMERCIAL VEHICLES CHAPTER VI 61
The stress in an aluminium struc - FIGURE VI.1 ture designed according to STRESS COMPARISON BETWEEN ALUMINIUM AND STEEL BEAMS deflec tion criteria is very often low. In the following example a steel beam, IPE 240 is compared ) a p with an aluminium beam I 330 x ‰ M 200 x 6 x 10 (both beams are ( S355 σ shown in the table VI.1). The deflection criterion is 1/250 of 300 span (24 mm), the span is 6000 EN AW-6082 T6 mm and the load is 11.6 kN/m. In the Figure VI.1. the stress-strain curves for steel S355 and alu - minium EN AW-6082 T6 is 200 shown. The stress and strain for both the steel and aluminium 161 beam is also shown. With the same deflection, the same load 100 and the same span, the steel 73 beam has a bending stress of
161 MPa while the aluminium 5 0 7 1 , 7 0 beam has a bending stress of 73 0 ε (%) , 0 MPa. This is the maximum stress ‰ when the deflection is 24 mm for 0,1 0,2 0,3 0,4 0,5 0,6 0,7 both beams.
Additional comparison of weight-optimized beams are also given in Chapter III, section 2.1 62 EUROPEAN ALUMINIUM ASSOCIATION ALUMINIUM IN COMMERCIAL VEHICLES CHAPTER VI
5. Limit state design
5.1. Philosophy methods that the new design all structural materials in civil standards are based on. In engineering. For aluminium the Limit state design and partial Europe the EN 19xx standards actual standards are: safety factor method are the are the basis for this method for
EN 1990 Eurocode – Basis for structural design EN 1991 Eurocode 1 – Actions on structures. All parts EN 1999 Eurocode 9 – Design of aluminium structures
EN 1990 gives the partial safety EN 1991 gives the characteristic EN 1999 gives the design rules factor on loads and rules for loads for structures and buildings for aluminium structures. combination of loads to give the such as self weight, live loads, different action effects. wind loads, snow loads, traffic loads etc.
5.2. What is the ultimate the scattering of the strength ferent loads. The partial safety limit state properties and the geometry of factor is different for the differ - the cross section. For connec - ent types of loads, their certainty The ultimate limit state is the tions the partial safety factor and how they are combined. condition where the safety of the shall in addition take care of Dead loads (i.e. self weight of structure is calculated. A struc - uncertainties in the welds and in structure) have a low partial safe - ture shall not collapse and design the bolts and bolt configuration. ty factor while the live load (i.e. in accordance with the ultimate The partial safety factor for the all forces that are variable during limit state shall avoid structural load effects ( γF) shall take care of operation, e.g. weight of goods, failure. the scattering of the determina - road vibrations etc…) has a high - The partial safety factor for the tion of the loads and the proba - er partial safety factor. resistance ( γM) shall take care of bility in the combination of dif - EUROPEAN ALUMINIUM ASSOCIATION ALUMINIUM IN COMMERCIAL VEHICLES CHAPTER VI 63
The condition to be fulfilled is: Typical values for the load effect vehicles the following load fac - factors in buildings and civil engi - tors may be used: Rk ≥ γ . E neering are 1.2 for dead loads Dead load: 1.1 γ F k M and 1.5 for live loads. For design Live load: 1.5 where: of components for commercial
Rk is the characteristic value of the resistance; it may be axial FIGURE VI.2 tension or compression, bending moment, shear or a combined resistance. ‰ y E is the characteristic value of c k n e the load effects; it may be axial u q e r
tension or compression, bending F moment, shear or a combined load effect on a cross section or a connection.
γM is the partial safety factor for the resistance, also often called material factor.
γF is the partial safety factor for the load effects, also often called ‰ Rk load factor. Ek E . γ < Rk k F γ This relation is shown in the M Figure VI.2.
Typical values for the partial safe - ty factor for the resistance are
1.10 ( γM1 ) for members and 1.25
(γM2 and γMw ) for bolt and rivet 5.3. What is the serviceability limit state connections and welded connec - tions. These are the material fac - The serviceability limit state is In serviceability limit states both tors for building and civil engi - the condition where the service - the partial safety factor for the neering and may also be used in ability criteria have to be satis - resistance ( γM) and the partial all structural design because the fied. The most used serviceability safety factor for the load effects material, the geometrical dimen - criteria are: (γF) are 1.0. sions and the fabrication of con - • Deflection limits in all directions nections are almost similar in all • Dynamic effects like vibrations aluminium structures. 64 EUROPEAN ALUMINIUM ASSOCIATION ALUMINIUM IN COMMERCIAL VEHICLES CHAPTER VI
6. Serviceability limit state 7. Ultimate limit state All calculations in serviceability limit state are elastic calculations. Where: 7.1. Cross section classes Elastic deformations are calculat - σgr is maximum compressive ed and compared with the limits stress in serviceability limit state Cross-sections are classified in 4 for deflections. The sizes of vibra - in the cross section, based on the classes. In Table VI.2 the differ - tions have to be calculated in the gross cross-section properties ent classes identify how the same manner. If the vibration has (positive in the formula) cross-section behaves during a high number of cycles, the Igr is the moment of inertia for compression and bending. This members and the connection the gross cross-section is directly linked to the resistance details have to be checked for Ieff is the moment of inertia of the (load bearing capacity) of the fatigue. effective cross-section in ultimate cross-section. Normally the calculations of elas - limit state, with allowance for Thin parts of a cross-section may tic deflections are based on the local buckling buckle at low stresses, and this moment of inertia for the gross will reduce the resistance of the cross-section of the member. For cross-section. This is taken care members in cross-section class 4 of with the rules for cross-section (see section 7.2.4 in EN 1999-1-1) classification. it is necessary to reduce the moment of inertia, if the stresses of the compression part of the cross section are higher than the stresses when local buckling occurs. Moment of inertia for calculation of deflections for cross section class 4 members:
σgr Iser = Igr - (Igr - Ieff ) fo EUROPEAN ALUMINIUM ASSOCIATION ALUMINIUM IN COMMERCIAL VEHICLES CHAPTER VI 65
TABLE VI.2 Class 1 Class 2 Class 3 Class 4
Cross-sections that can Cross-section that can Cross-section where the Cross-section that will get form a plastic hinge with develop their plastic calculated stress in the local buckling before the rotation capacity moment resistance, but extreme fibre of the alu- attainment of proof stress required for plastic analy- have limited rotation minium member can in one or more parts of sis without reduction of capacity. reach its proof strength. the cross-section. the resistance. The resistance may be The resistance may be The resistance is calcu- The resistance is calculat- calculated on the basis calculated on the basis lated on the basis of ed on basis of an effec- of plastic behaviour tak- of perfectly plastic elastic design. tive cross-section. Rules ing the material harden- behaviour for the materi- for calculating the effec- ing effect into account. al using the conventional tive cross-section are Rules are given in EN elastic limit as the limit given in EN 1999-1-1, 1999-1-1. Annex F. value. Rules are given in 6.1.5 EN 1999-1-1. Annex F.
EN 1999-1-1, 6.1.4 gives rules t = the corresponding thickness commercial vehicles will be opti- how to classify any cross-section. η = a value depending on the mised regarding weight. Cross A β value (i.e. width to thickness stress situation and if the part is section classes 1 and 2 will there- ratio) is calculated as: an outstand or an internal cross- fore seldom be used. Elastic section part design in cross section class 3 and b β = η . Limits are given for the β value 4 will be the normal situation. t for the different classes and for where: welded or unwelded parts and b = the width of a cross-section for outstand or internal parts. part Most aluminium structures in
7.2. Load bearing resistance EN 1999-1-1 gives rules for cal- these rules are listed, and refer- culating the load bearing resist- ences are given: The load bearing resistance shall ances for different kinds of mem- always be higher than the fac- bers exposed by different load tored load effects. effects. In the Table VI.3, some of 66 EUROPEAN ALUMINIUM ASSOCIATION ALUMINIUM IN COMMERCIAL VEHICLES CHAPTER VI
TABLE VI.3 Situations Ref. EN 1999-1-1 Resistance Tension 6.2.3 The smaller of: . . Ag . fo 0,9 . Anet fu Aeff fu No,Rd = , Nu,Rd = or Nu,Rd = γM1 γM2 γM2
No,Rd is the design resistance to general yielding.
Nu,Rd is the design resistance to axial force of the net cross-section at holes for fasteners or the effective cross-section at welds.
Ag is the gross cross-section.
Anet is the net area of cross-section.
Aeff is the effective area of cross-section taking the HAZ effects into account. Compression 6.2.4 The smaller of: . (with no Anet . fu Aeff fo Nu,Rd = , Nc,Rd = buckling) γM2 γM1
Nu,Rd is the design resistance to axial force of the net cross-section at holes for fasteners.
Nc,Rd is the design resistance to axial force at each cross-section.
Anet is the net section area with deduction for holes and if required the effects of HAZ softening at the cross section with holes.
Aeff is the effective section area based on the reduced thickness allowing for the effect of local buckling. Bending 6.2.5 Bending moment resistance in a net section: moment Wnet . fu Mu,Rd = γM2 Bending moment resistance in each cross section: . α Wel . fo Mc,Rd = γM1 6.2.5.2 Wnet is the elastic modulus of the net section allowing for holes and HAZ softening.
Wel is the elastic modulus of the gross section. 6.2.5.1 α is the shape factor given in table 6.4 in EN 1999-1-1, 6.2.5. Shear 6.2.6 The design value for shear resistance for non-slender sections:
AV . fo VRd = √3 . γM1
Av is the shear area. 6.7.4 6.7.5 For slender webs and stiffened webs the rules for capacity of plate 6.7.6 girder webs have to be used (plate buckling). EUROPEAN ALUMINIUM ASSOCIATION ALUMINIUM IN COMMERCIAL VEHICLES CHAPTER VI 67
Situations Ref. EN 1999-1-1 Resistance Torsion 6.2.7 The design St. Venants torsion moment resistance without warping:
WT,pl . fo TRd = √3 . γM1
WT,pl is the plastic torsion modulus 6.2.7.2 For torsion with warping the capacity is the sum of two internal 6.2.7.3 effects. For combined shear force and torsional moment the capacity is given by a reduced shear capacity. Bending and 6.2.8 The shear force will reduce the moment resistance. If the shear shear force is less than half of the shear force resistance, the effect of the moment resistance is so small that it can be neglected. Bending and 6.2.9 Formulae are given for the combined effect of an axial tension axial force and bending moments about one or two axis for: 6.2.9.1 • open cross-sections 6.2.9.2 • hollow sections and solid cross-sections 6.2.9.3 • members containing localized welds Bending, shear 6.2.10 The shear force will reduce the combined axial tension and and axial force moment resistance. If the shear force is less than half of the shear force resistance, the effect of the combined axial tension and moment resistance is so small that it can be neglected. Web bearing 6.2.11 This is for design of webs subjected to localized forces caused by concentrated loads or reactions applied to a beam. Compression 6.3 Members subject to axial compression may fail in one of the (buckling three ways listed below: resistance) • flexural • torsional or flexural torsional • local squashing The design buckling resistance of a compression member is: . . . κ χ Aeff fo Nb,Rd = γ M1 κ is a factor to allow for effect of the HAZ at welds χ is the reduction factor for the relevant buckling mode
Aeff is the effective area of the cross section. (For cross section class 1, 2 and 3 this is the gross cross-section, for cross section class 4 it is reduced for local buckling effects) 68 EUROPEAN ALUMINIUM ASSOCIATION ALUMINIUM IN COMMERCIAL VEHICLES CHAPTER VI
Situations Ref. EN 1999-1-1 Resistance Members 6.3.3 Members subject to bending and axial compression may fail in one of in bending the two ways listed below: and axial • flexural buckling compression • lateral-torsional buckling 6.3.3.1 Combination formulas are given for members with axial compression in combination with bending about one or two axis and fail for flexural buckling. These formulas are given for: • open double symmetric cross-section • solid cross-section • hollow cross-section and tube • open mono-symmetrical cross-section 6.3.3.2 Combination formula for open cross-section symmetrical about major axis, centrally symmetric or double symmetric cross-section is given for lateral- torsional buckling. Formulas are also given for calculation of the following effects: 6.3.3.3 • members containing localized welds 6.3.3.4 • members containing localized reduction of cross-section 6.3.3.5 • unequal end moments and/or transverse loads Plate girders 6.7 A plate girder is a deep beam with a tension flange, a compression flange and a web plate. The web is usually slender and may be reinforced by transverse or/and longitudinal stiffeners. Webs buckle in shear at relatively low applied loads, but considerably amount of post-buckled strength can be mobilized due to tension field action. Plate girders are sometimes designed with transverse web reinforcement in form of corrugations or closely-spaced transverse stiffeners (extrusions). Plate girders can be subjected to combinations of moment, shear and axial loading, and to local loading on the flanges. Because of their slender proportions they may be subjected to lateral torsional buckling, unless properly supported along the length. Failure (buckling) modes may be: 6.7.2 & 6.7.3 • web buckling by compressive stresses 6.7.4 & 6.8 • shear buckling 6.7.6 • interaction between shear force and bending moment 6.7.5 • buckling of web because of local loads on flanges 6.7.7 • flange-induced web buckling 6.1.5 • torsional buckling of flange (local buckling) 6.3.2 • lateral torsional buckling EUROPEAN ALUMINIUM ASSOCIATION ALUMINIUM IN COMMERCIAL VEHICLES CHAPTER VI 69
7.3. Welded connections and the alloys being welded. 7.3.2. Butt weld Values are given in Table 8.8 in 7.3.1. General EN 1999-1-1. Heavy loaded members should be Single sided butt welds with no welded with full penetration butt The rules given in EN 1999-1-1, backing is practically impossible welds. The effective thickness of clause 8.6, apply to structures to weld in aluminium. If single a full penetration butt weld welded by MIG or TIG and with sided butt welds cannot be should be taken as the thickness weld quality in accordance with avoided, the effective seam of the thinnest connecting mem - EN 1090-3. Certified welders are thickness can be taken as: ber. The effective length should highly recommended. • the depth of the joint prepara - be taken as the total length if Recommended welding consum - tion for J and U type run-on and run-off plates are ables can be found in: • the depth of the joint preparation used. If not, the total length • Chapter VIII, section 3.8 minus 3 mm or 25%, whichever is should be reduced by twice the • EN 1999-1-1, section 3.3.4 the less for V or bevel type effective thickness. (Figure VI.3) • EN 1011-4 In addition to the single sided FIGURE VI.3 When welding hardened alu - butt weld, a fillet weld may be minium alloys, part of the hard - used to compensate for the low F, σ ening effect will be destroyed. In penetration of the butt weld. a welded connection it can be When designing a welded connec - ‰ three different strengths: tion some few practical precautions t‰
• the one of the parent (not should be taken into account. ‰ b ‰ heat affected) material ( fo) • Provide good access to the • the one in the heat affected welding groove. The “welding zone ( fo,HAZ ) head” of the equipment used for F, σ • the one of the weld metal ( fw) welding aluminium is rather large, so there must be enough Butt weld subject to normal stresses Normally it will be necessary to space around the weld. check the stresses in the HAZ and • Good access is also needed for in the welds. checking the weld. All welds ‰ The strength in HAZ is depend - shall be 100 % visually examined
F, τ ‰ ent on the alloy, the temper, the in addition to some non-destruc - t
type of product and the welding tive testing (NDT). ‰ b ‰ F, τ procedure. Values are given in • Full penetration single sided Table 3.2 in EN 1999-1-1. butt welds are impossible to The strength in the weld (weld weld without any backing. metal) is dependent on the filler If possible, position the welds in Butt weld subject to shear stresses metal (welding consumables) areas where the stresses are low. 70 EUROPEAN ALUMINIUM ASSOCIATION ALUMINIUM IN COMMERCIAL VEHICLES CHAPTER VI
FIGURE VI.4 Design formulas for butt welds: Normal stress, tension or com - FILLED WELD
pression, perpendicular to weld ‰ t axis: 1 ‰
fw σ⊥ ≤ γMw ‰ Shear stress: 1
f g τ ≤ 0,6 . w ‰ ‰ γMw 2
a t Combined normal and shear ‰ a ‰
‰ ‰ stress: a ‰ ‰ pen ‰ f 2 . 2 w √σ⊥ + 3 τ ≤ γMw
FIGURE VI.5 7.3.3. Fillet weld EXAMPLE OF UNIFORM STRESS DISTRIBUTION
A fillet weld is defined with the throat thickness “a” given in mm. The Figure VI.4 shows how to measure the throat thickness. The effective length should be taken as the total length of the τ τ weld if: • the length of the weld is at least 8 times the throat thickness • the length of the weld does FIGURE VI.6 not exceed 100 times the throat EXAMPLE OF NON UNIFORM STRESS DISTRIBUTION thickness with a non-uniform stress distribution • the stress distribution along the length of the weld is constant
τ τ EUROPEAN ALUMINIUM ASSOCIATION ALUMINIUM IN COMMERCIAL VEHICLES CHAPTER VI 71
The forces acting on a fillet weld σ⊥ : normal stress perpendicular τ⊥ : shear stress acting on the shall be resolved into stress com- to the throat section throat section perpendicular to ponents with respect to the σ⎜⎜ : normal stress parallel to the the weld axis throat section (see Figure VI.7). weld axis τ ⎜⎜ : shear stress acting on the These components are: throat section parallel to the weld axis
FIGURE VI.7 FORCES ACTING ON A FILLET WELD
σ
‰ ⊥ F,σ ‰
‰ τ ‰ a II ‰
σII ‰
‰ ‰
τ τ⊥
Design formula for fillet weld:
f 2 . 2 2 w √σ⊥ + 3 (τ⊥ + τII ) ≤ γMw 72 EUROPEAN ALUMINIUM ASSOCIATION ALUMINIUM IN COMMERCIAL VEHICLES CHAPTER VI
7.3.4. Heat affected zone welds and fillet welds. The W: weld metal, check of weld sketches below (ref. BS 8118) F: heat affected zone, check of The stress in the heat affected indicate the failure plane for fusion boundary zone has to be checked. The some welds (Figures VI.8, VI.9, T: heat affected zone, check of stress is calculated for the small - VI.10, VI.11): cross section est failure plane for both butt
FIGURE VI.8 FIGURE VI.9 BUTT WELD FILLET WELD
W F W F
P F ‰
v ‰ ‰P
t a
‰ ‰ P v ‰ ‰
P ‰ a ‰ P
P ‰ t ‰P a v ‰ a F
‰ t ‰ Pv T
FIGURE VI.10 FIGURE VI.11 T BUTT WELD T FILLET WELD
P a Pa
P ‰
v ‰
‰ Pv ‰
‰ t ‰ ‰ t T ‰ T W F F W
W F F F
T T T T EUROPEAN ALUMINIUM ASSOCIATION ALUMINIUM IN COMMERCIAL VEHICLES CHAPTER VI 73
7.4. Bolted connections Minimum, regular and maximum spacing, end and edge distances The rules for bolted connections are for bolts are given in the Table given in EN 1999-1-1, clause 8.5. VI.4.
TABLE VI.4
Minimum Regular Maximum
. e1 = 4 t + 40 mm e = 4 . t + 40 mm e = 1.2 . d e = 2.0 . d 2 1 0 1 0 . e = 1.2 . d e = 1.5 . d 14 t 2 0 2 0 p ≤ . . 1 { 200 mm p1 = 2.2 d0 p1 = 2.5 d0 . . p2 = 2.2 d0 p2 = 3.0 d0 14 . t p ≤ 2 { 200 mm
14 . t p1 ≤ . p = 2.5 . d { 200 mm p1 = 2.2 d0 1 0 . p = 3.0 . d . p2 = 2.4 d0 2 0 14 t p ≤ 2 { 200 mm
Outer lines: 14 . t p ≤ 1 { 200 mm . . p1 = 2.2 d0 p1 = 2.5 d0 Inner lines: 28 . t p ≤ 1 { 400 mm o) outer line i) inner line d0 is the diameter of the hole and t = thickness of the plate
The maximum clearance for fit - • block tearing, failure in shear • bearing failure of the bolt hole ted bolts is 0.3 mm and for non- in a row of bolts along the shear • tension failure of the bolt fitted bolts 1.0 mm. face of a bolt group and tension • punching shear around the failure along the tension face of bolt head or nut Failure modes for bolted connec - the bolt group • combined shear and tension tions may be: • shear failure in the bolt failure 74 EUROPEAN ALUMINIUM ASSOCIATION ALUMINIUM IN COMMERCIAL VEHICLES CHAPTER VI
TABLE VI.5
Failure mode Formula Parameters
Shear αv = 0.6 for steel bolts, 4.6, 5.6 and 8.8 αv . fub . A resistance per Fv,Rd = αv = 0.5 for steel bolts, 4.8, 5.8, 6.8 and 10.9 γM2 shear plane αv = 0.5 for stainless steel and aluminium bolts A is the cross-section of the bolt at the shear plane
e Bearing 2.8 2 - 1.7 k1 . αb . fu . d . t d0 resistance Fb,Rd = γM2 k1 = smallest of for edge bolts { 2.5 p 1.4 2 - 1.7 d0 k1 = smallest of for inner bolts { 2.5
αd
fub αb = smallest of fu {1.0
e1 αd = for end bolts 3 . d0
p1 1 αd = − for inner bolts 3 . d0 4
k2 = 0.9 for steel bolts Tension k . f . A 2 ub s k = 0.5 for aluminium bolts resistance Ft,Rd = 2 γM2 k2 = 0.63 for countersunk steel bolts
As is the tensile stress area of the bolt d is the mean of across points and across flats Punching shear m 0,6 . π . dm . tp . fu of a bolt head or the nut or the outer resistance Bp,Rd = γM2 diameter of the washer
tp is the thickness of the plate under the bolt head or the nut
Combined Fv,Ed is the load effect of shear F F shear v,Ed t,Ed F is the load effect of tension + ≤ 1.0 t,Ed F 1.4 . F and tension v,Rd t,Ed EUROPEAN ALUMINIUM ASSOCIATION ALUMINIUM IN COMMERCIAL VEHICLES CHAPTER VI 75
FIGURE VI.12 Connection details that carry ten - PRYING FORCES sile forces, and where the tensile N=F +Q forces don’t go directly through N N=FN +Q the bolts, additional forces in the bolts have to be accounted for. These forces are called prying Q Q forces (Q) and they can be con - siderable large. See the figure VI.12.
2FN
Truck bodies for beverage transport 76 EUROPEAN ALUMINIUM ASSOCIATION ALUMINIUM IN COMMERCIAL VEHICLES CHAPTER VI
8. Fatigue
8.1. Theory stress concentrations. With con - defined as the algebraic differ - tinuous repeating loads the crack ence between the stress peak Structures with repeating loads will grow, this will be shown as and the stress valley in a stress may be susceptible to fatigue one striation in the failure sur - cycle. At low stress ranges the when the number of load cycles face for each load cycles. The dis - crack grows slowly and with high is high, even when the loads give tance between the striations is stress range it grows fast. (Figure low stresses in the structure. depending on the stress range VI.13) Fatigue failure starts with devel - and that is giving the growing opment of a crack at a point with speed. The stress range is
Trailer fatigue testing in laboratory (Benalu) EUROPEAN ALUMINIUM ASSOCIATION ALUMINIUM IN COMMERCIAL VEHICLES CHAPTER VI 77
FIGURE VI.13 ‰ 3 ‰ σ
‰ σ
‰ ‰
‰ max
1 3 σ ‰
σ σm ‰ Δ 0 3
T σ 2 ‰
‰ ‰ ‰ σmin
1. Stress peak Δσ Stress range Stress amplitude 2. Stress valley σ3 3. Stress cycle
Rules for fatigue design are given in EN 1999-1-3. The rules are The picture is showing the striations in a fatigue failure surface of an aluminium tube. based on quality levels given in EN 1999-1-3 and EN 1090-3. • The fatigue strength depends on: • type of detail (design) • stress range • number of cycles • stress ratio • quality of manufacturing 78 EUROPEAN ALUMINIUM ASSOCIATION ALUMINIUM IN COMMERCIAL VEHICLES CHAPTER VI
The properties of the parent influence at all. For a plate or The fatigue strength is given as material have very little influence extrusion with no manufacturing SN curves for the different on the fatigue strength in practi- or only holes and notches the details. All detail categories given cal structures and components. standard deviate between EN in EN 1999-1-3 have their own For connections the properties of AW 7020 and all other structural SN curve. A typical SN curve is the parent material have no alloys. shown on the Figure VI.14.
FIGURE VI.14
Δσ 2)
S
a ‰ 1
m1 b ΔσC c ΔσD 1
m2 d ΔσL
e . e 2 . 10 ‰ 5 10 ‰ N 1) N L NC D
104 105 106 107 108 109 N a. Fatigue strength curve b. Reference fatigue strength c. Constant amplitude fatigue limit d. Cut-off limit
1) Number of cycles (108) at rect, other calculation methods range don’t result in a tensile which the cut-off limit is defined are recommended (Annex F of stress exceeding the design stress 2) For low cycles fatigue, this EN 1999-1-3). It shall be checked in ultimate limit state. part of the curve may not be cor- that the maximum design stress EUROPEAN ALUMINIUM ASSOCIATION ALUMINIUM IN COMMERCIAL VEHICLES CHAPTER VI 79
The stress ratio, R, is the mini- elements, where the residual stress, the fourth gives the weld mum stress divided by the maxi- stresses has been established, type, the fifth gives the stress mum stress in a constant ampli- taking into account any preac- parameter, the sixth gives the tude stress history or a cycle tion or lack of fit, there will be an welding characteristics, the sev- derived from a variable ampli- increase in the fatigue strength enth gives the quality level for tude stress history. Favourable for R < -0.25. For other cases the internal imperfections and stress ratio will enhance the there will be no change from the the eight gives the quality level fatigue strength for some cases values in the standard. for the surface and geometrical compared with the values given Some typical details categories imperfections. The requirements in the standard. For initiation are shown in the Table VI.6. The for the quality levels are found in sites in base material away from first row in the table gives the EN ISO 10042 and additional connections, there will be an detail type number, the second requirements are given in EN increase in the fatigue strength row gives the detail category, the 1090-3. for R < +0.5. For initiation site at third gives a sketch of the detail welded or mechanical fastened and also showing the initiation connections in simple structural site and the direction of the
TABLE VI.6 ‰ ‰ Continuous 5.1 63-4,3 automatic B C
Full penetration welding ‰ ‰ butt weld Δσ Weld caps ground
‰ ‰ flush 5.2 56-4,3 Δσ C C
At weld discontinuity ‰ ‰
‰ ‰ Any backing
Δσ Full penetration 5.3 45-4,3 ‰ bars to be C D ‰ butt weld Δσ continuous
At weld discontinuity ‰ ‰ 5.4 45-4,3 Nominal stress at initiation site B C
Continuous fillet
‰ weld ‰ ‰ Δσ ‰ 5.5 40-4,3 Δσ C D At weld discontinuity 80 E UROPEAN ALUMINIUM ASSOCIATION ALUMINIUM IN COMMERCIAL VEHICLES CHAPTER VI
Detail types 5.4 and 5.5 are an The SN curves that correspond to The numerical values for the example where the same detail these detail categories are shown same curves are shown in the has different fatigue strength on Figure VI.15. Table VI.7. depending on the quality of the weld.
FIGURE VI.15 INFLUENCE OF WELD QUALITY ON FATIGUE STRENGTH
NC NO NL 500 400
Δσ 300 N/mm2 200 150 S 100
50 40 63-4,3 30 56-4,3 45-4,3 40-4,3 20 36-4,3
15 28-4,3
10
5 104 105 106 107 108 109 N EUROPEAN ALUMINIUM ASSOCIATION ALUMINIUM IN COMMERCIAL VEHICLES CHAPTER VI 81
TABLE VI.7
SLOPE Cycles N
m1 m2 1E+05 1E-06 2E+06 5E+06 1E+07 1E+08 1E+09 4.3 6.3 126.4 74.0 63.0 50.9 45.6 31.6 31.6 4.3 6.3 112.4 65.8 56.0 45.3 40.5 28.1 28.1 4.3 6.3 90.3 52.9 45.0 36.4 32.6 22.6 22.6 4.3 6.3 80.3 47.0 40.0 32.3 29.0 20.1 20.1 4.3 6.3 72.3 42.3 36.0 29.1 26.1 18.1 18.1 4.3 6.3 56.2 32.9 28.0 22.6 20.3 14.1 14.1
Fatigue field test (Benalu) 82 EUROPEAN ALUMINIUM ASSOCIATION ALUMINIUM IN COMMERCIAL VEHICLES CHAPTER VI
8.2. Practice: comparison between good and bad chassis solutions
The following sections shows They all refer to the load case good and bad design solutions described in Figure VI.16. for aluminium trailer chassis.
FIGURE VI.16 BOUNDARY CONDITIONS AND BEAM GEOMETRY AS A BASIS
FOR THE FINITE ELEMENT ANALYSIS ‰ 7300
‰
‰ 3000‰ 2150 ‰ ‰
N 115
cm ‰
‰ ‰ ‰ 1000 1250
5 ‰ 7300 6 1
‰ ‰ 1
‰ 0 ‰ ‰ ‰ R1000 0 ‰
‰ 4
‰
‰ ‰ 1900 941 ‰ 0
‰ ‰ 6 R1000 100
Load case with 0,5x115 N/cm is used (dashed rectangle). Cross section of the beam is a simple symmetrical H-section with a flange-width of 150 mm, flange-thickness of 12 mm and web-thickness 8 mm. (1: To achieve the gooseneck, a part of the web has been cut off and re-joined by welding at a distance of 60 mm from the lower flange.) EUROPEAN ALUMINIUM ASSOCIATION ALUMINIUM IN COMMERCIAL VEHICLES CHAPTER VI 83
8.2.1. Gooseneck FIGURE VI.17
PLAIN CHASSIS BEAM, R = 1000 mm (σmax = 43 MPa, δ= 5.3 mm) The Gooseneck area of the chas- sis beam will be the most stressed part and has to be very carefully treated to avoid prob- lems. Generally good precautions ‰ will be: • It is of utmost importance to avoid all welding or heat treat- σmax =43MPa ment on, or near, the flanges. • No welded or bolted attach- ments to, or near, the flanges in this area. FIGURE VI.18 • No joining of the beams and/or reinforcement of the PLAIN CHASSIS BEAM, R = 450 mm (σmax = 73 MPa, δ= 6.9 mm) beams in this area. • No sudden variation of material
thickness or properties in this area. It is obviously mandatory to fol- ‰ low the fabrication or shop drawings, design manuals, weld- ing procedures, QA-manuals and σ =73MPa the designer’s guidance through- max out the whole fabrication process.
Figures VI.17, VI.18 and VI.19 FIGURE VI.19 present a few lifespan examples PLAIN CHASSIS BEAM, R = 300 mm (σ = 85 MPa, δ= 7.5 mm) depending on the geometry of the max Gooseneck (i.e. curvature radius).
One can see the increase in stress level is approximately 70% and ‰ the increased deflection (δ) approximately 23%. The conse- quence will be a relative lifespan σmax =85MPa decrease of 50 % from the nor- 84 E UROPEAN ALUMINIUM ASSOCIATION ALUMINIUM IN COMMERCIAL VEHICLES CHAPTER VI
mal radius of 450 mm to 350 FIGURE VI.20 mm. As illustrated, an increased HOLE IN CHASSIS BEAM FLANGE, (ø = 20 mm): σmax = 102 MPa radius of 1000 mm will offer very low stresses and demonstrates simply the importance of smooth transitions.
8.2.2. Perforation
The fixture of the supporting legs
to the chassis beam will normally ‰ be located at the highest stressed ‰ area of the chassis beam, i.e. in the gooseneck area. Hence a per- σmax =102MPa foration of the bottom flange by σ =73MPa boltholes must be avoided as well as any welding on or near the flange. Figures VI.20 and VI.21 show the consequence of perforating the flange compared to the web in FIGURE VI.21 this area.
HOLE IN CHASSIS BEAM FLANGE, (ø = 20 mm): σmax = 73 MPa (on flange) The reduced relative lifespan will be as much as >80% due to the effect of stress concentration in the perforated area of the flange. For the situation with the perfo-
ration through the web, the lifes- ‰ pan will not be reduced. Both examples show the importance of a location away from the most stressed area of the beam. If a σ =35MPa perforation through the flange is inevitable, the location should be ‰ as close as possible to the edge of the flange (as far from the σmax =73MPa web as possible). Note that EUROPEAN ALUMINIUM ASSOCIATION ALUMINIUM IN COMMERCIAL VEHICLES CHAPTER VI 85
required minimum distance from FIGURE VI.22 the edge should be according to FIXTURE BY WELDING ON FLANGE: σmax = 97 MPa actual standards, normally 1,5ø – 2,0ø depending on direction of load, etc. Also note that local bending capacity of flange must be checked according to actual location.
8.2.3 Welding ‰
A fixture by welding in the web area of the beam is a much-used ‰ σmax =97MPa alternative to bolting, and will be fully acceptable as long as weld- σ=73 MPa ing is avoided in or near the flange (i.e. in the most stressed area of the beam). Figures VI.22 and VI.23 illustrate the conse- quence of welding on the flange and on the web. FIGURE VI.23
The lifespan reduction will be as FIXTURE BY WELDING ON WEB: σmax = 73 MPa (on flange) much as >90% in the case of the fixture by welding on flange, due to the effect of stress concentra- tion in the welded area of the flange and the decreased materi- al properties due to heating.
The fixture by welding in the web ‰ area will be of no effect to lifes- pan. In both cases a geometrical- ly perfect weld is assumed. In real ‰ life, imperfections are common σ =25MPa and therefore good workman- ship and after treatment of welds σmax =73MPa must be considered. 86 EUROPEAN ALUMINIUM ASSOCIATION ALUMINIUM IN COMMERCIAL VEHICLES CHAPTER VI
Aluminium road tankers (Schrader) 9. Special design issues
9.1. Tanks for the ing equivalence formula, where Furthermore, absolute minimum e is the minimum shell thickness shell thicknesses are fixed transport of dangerous 0 for mild steel and R and A, the depending on the type of tank, goods - ADR m tensile strength and elongation the shell dimension and the Tanks for the transport of dan - of the metal chosen. material used. gerous goods have to be built e0 × 464 according to the rules defined in e = 3 (R × A) 2 the following agreement and √ m standards: For tanks protected against damage: • ADR: Agreement for the trans - • For shells with circular cross-section ≤ 1.80 m: 1 port of Dangerous goods by Road e0 = 3 mm • EN 13094 “Tanks for the e cannot be lower than 4,00 mm for aluminium alloys 2 transport of dangerous goods - • For shells with circular cross-section > 1.80 m
Metallic tanks with a working e0 = 4 mm pressure not exceeding 0.5 bar - e cannot be lower than 5,00 mm for aluminium alloys Design and construction” For other tanks:
• EN 14025 “Tanks for the e0 = 5 mm for shells with circular cross-section ≤ 1.80 m transport of dangerous goods - e0 = 6 mm for shells with circular cross-section > 1.80 m Metallic pressure tanks - Design and construction” 1. See ADR - Annex A – Part 6 – Chapter 6.8: In particular, tank shell thickness http://www.unece.org/trans/danger/danger.htm (e) is determined by the follow - 2. Whatever the result of the equivalence formula is. EUROPEAN ALUMINIUM ASSOCIATION ALUMINIUM IN COMMERCIAL VEHICLES CHAPTER VI 87
Suitable aluminium alloys for that 9.2. Tippers Another version which came up application are listed in standard in the last few years is a material EN 14286 “Aluminium and alu - 9.2.1. Construction – mix version with a steel bottom minium alloys - weldable rolled plate and aluminium side- walls products for tanks for the stor - Tipper body trailers (or “dump (bolted to the steel plate). age and transportation of dan - bodies”) are constructed in two gerous goods”. See also Chapter different versions: Two main tipper types can be dif - V, section 6.4 in this manual. • Combination of plates and ferentiated: extrusions (more frequently used • Rectangular trailer For tanks protected against dam - version) • Half – pipe trailer age, several alloys listed in EN • Extrusion intensive construc - 14286 allow manufacturing tank tion, where all sides of the trailer Independent from the type of tip - shells with e = 5.3 mm (corre - are made of clamped and / or per, all extrusion cross – sections sponding to R m x A = 6600) and welded extrusion profiles and the thickness of the plates even e = 5.0 mm (for those with are calculated with respect to:
Rm x A ≥ 7152).
Aluminium tipper bodies (Stas) 88 EUROPEAN ALUMINIUM ASSOCIATION ALUMINIUM IN COMMERCIAL VEHICLES CHAPTER VI
Production of aluminium tipper bodies (Schmitz)
• Actual load (compression / Wear is not only taken into 9.2.2.2. Factors influencing tension) account for the calculation of the the wear • Bending forces (static and dur - actual plate or extrusion thick - The wear condition can vary ing tipping operation) ness, especially of the bottom extremely from one load to • Other forces like shear stress, plate, but also for the type of alu - another. Therefore it is not deflection, buckling minium to be chosen. always possible to link the actual hardness of a work-hardened In addition, the type of products 9.2.2.1. Defintion of Wear alloy to the wear resistance 3. It to be transported has to be taken The mechanism of wear is quite was found out that for a very into consideration during design complex. Wear generally occurs large extent, the type of load is a of the tipper. This is due to the when one surface (usually harder decisive factor. fact, that the load can be just than the other) cuts off material concentrated locally and on a from the second. The area of con - Soft goods like potatoes, fruits, very small area or it can be divid - tact between the two surfaces is sugar beets or other agricultural ed quite uniform across the thereby very small and concen - products are much less abrasive whole bottom of the tipper body. trated on surface asperities. The than mineral goods. In case of shear forces are transferred mineral goods like stones, pow - 9.2.2. Wear through these points and so the ders, cement, chalk etc. the size, local forces can be very high. form (sharpness) and hardness of Wear (or abrasion- resistance) is the material is by far the most the most discussed issue when it Abrasives can act like in a grind - critical factor regarding abrasion comes to the construction of an ing process where the abrasive is (in laboratory tests even the aluminium tipper. A lot of uncer - fixed relative to one surface or in change of a type of sand tainties about the abrasion – a lapping process, where the increased the wear by 35%). resistance of the aluminium as abrasive tumbles, producing a well as the totally different type series of indentations. of loads makes it nearly impossi - 3. Abrasive wear of aluminium alloys rubbed against sand , K. Elleuch, ble to find a perfect solution for S. Mezlini, N. Guermazi, Ph. Kapsa, each transport problem. Wear 261 (2006) 1316–1321 EUROPEAN ALUMINIUM ASSOCIATION ALUMINIUM IN COMMERCIAL VEHICLES CHAPTER VI 89
Even the wear debris acts there- 9.2.3. Material selection 10. References by as an additional source for abrasion. The choice of material for the bottom plate of tipping trailers is • EN 1999-1-1 Eurocode 9 Also the number of tipping opera- nowadays often a question of Design of aluminium structures, tions is to be considered. The more specific experience, material Part 1-1 General structural rules. often the trailer is tilted, the more availabilty and manufacturer s • EN 1999-1-3 Eurocode 9 often abrasion occurs. The num- specific production methods. Design of aluminium structures, ber of cycles has a linear function Part 1-3 Structures susceptible to when set into relation to the mass Typical bottom plate material is: fatigue. lost of the aluminium plate. • 5083 H32, H321, H34 • EN 1090-3 Execution of steel • 5086 H24 structures and aluminium struc- Very often, tippers are used by • 5383 H34 tures, Part 3 Technical require- the transport companies for • 5454 H22, H24 ments for aluminium structures other products than they are • 5456 H34 • EN-ISO 10042 Arc-welded joints originally made for and so a reli- or other, mill-specific alloy types. in aluminium and its weldable able calculation of the lifetime of alloys – Guidance on quality lev- an aluminium bottom plate can- els for imperfections. not be determined. • BS 8118 Structural use of alu- minium, Part 1 Code of practice for design. • ADR: Agreement for the trans- port of Dangerous goods by
Full aluminium tipper (Menci) Road. • EN 13094 Tanks for the trans- port of dangerous goods - Metallic tanks with a working pressure not exceeding 0.5 bar - Design and construction. • EN 14025 Tanks for the trans- port of dangerous goods - Metallic pressure tanks - Design and construction. • EN 14286 Aluminium and alu- minium alloys - weldable rolled products for tanks for the stor- age and transportation of dan- gerous goods. EUROPEAN ALUMINIUM ASSOCIATION CHAPTER VII
FABRICATION
1. INTRODUCTION ...... 92 1.1. 5000 series alloys ...... 92 1.2. 6000 series alloys ...... 92 1.3. 7000 series alloys ...... 93 2. FABRICATION OF PRODUCTS FROM PLATE ...... 93 2.1. Storage ...... 93 2.2. Marking out ...... 94 2.3. Cutting to shape ...... 94 2.4. Edge rolling ...... 97 2.5. Bending ...... 97 2.6. Non-machinable faces ...... 97 3. FABRICATION OF PRODUCTS FROM EXTRUSIONS ...... 98 3.1. Storage ...... 98 3.2. Cutting ...... 98 3.3. Bending ...... 98 4. DRILLING ...... 102 4.1. Twist drill ...... 102 4.2. Straight flute drill ...... 102 4.3. Gun drill ...... 102 4.4. Half-round or three quarter round drill ...... 102 5. TAPPING ...... 103 5.1. Chip removal ...... 103 5.2. Upsetting ...... 104 5.3. Threaded inserts ...... 104 6. DEEP DRAWING ...... 104 7. SPINNING ...... 105 7.1. Advantages of spinning ...... 105 7.2. Diameter of spinning blanks ...... 105 92 EUROPEAN ALUMINIUM ASSOCIATION ALUMINIUM IN COMMERCIAL VEHICLES CHAPTER VII
1. Introduction
The forming operations used in 1.1. 5000 series alloys 1.2. 6000 series alloys the commercial vehicle industry are many and various. The man - In soft conditions, 5000 series These are used mainly as extruded ufacturer will cut, fold, roll and alloys have excellent forming sections. The main alloy elements bend semi-finished sheets and properties as suggested by the are magnesium and silicon. extrusions to produce a vehicle difference between proof stress These are heat treatable alloys or an accessory. and ultimate tensile strength and supplied in the T6 or T5 condi - by the level of elongation 1. tion and, less commonly, in the These operations, some of which T4 or T1 condition 3. such as cutting and drilling can As metals are hardened by now be programmed and auto - mechanical cold working, it may Generally speaking the shaping mated, are carried out according be necessary to improve ductility properties of this family of alloys to rules which we have summa - so as to continue forming by in the fully heat-treated condi - rized in this chapter. In certain machine or by hand. This is done tion are limited. Nevertheless cases and in some countries they by annealing 2, a process that is shaping should be performed are also standardized, and the easy to accomplish either in a cold as heating will considerably relevant standards are referred to furnace or with a welding torch, reduce mechanical properties where they exist. using tallow as a temperature (approx. 40 %). indicator which turns a light More complex shaping of the In any case, it is very important to brown colour at 340 °C. Heat extrusions may be done in the T1 use equipments dedicated to alu - indicator crayons or even a stick or T4 condition, before ageing to minium. pyrometer may also be used. full hardness in T5 or T6. In this case it is beneficial to do the Most aluminium alloys used in If necessary, inter-stage anneal - forming within a short time win - commercial vehicles belong to ing can be repeated between dow of a few days after the solu - the family of aluminium-magne - shaping operations, however tion heat-treatment to T1 or T4, sium alloys (5000 series) for rolled there is one golden rule: only products or to the aluminium-sili - anneal the metal if it becomes con-magnesium family (6000 difficult to work, in other words 1. Please refer to EN 485-2. series) for extruded products. when the work-hardening rate 2. For 5000 alloys with Mg content is greater than or at least equal above 3%, this must be done very care - fully to prevent sensitization to inter - to the so-called critical work- granular corrosion. See also Chapter XI, hardening rate. section 2.2.6. 3. Please refer to Chapter V section 5, for an explanation of these tempers. EUROPEAN ALUMINIUM ASSOCIATION ALUMINIUM IN COMMERCIAL VEHICLES CHAPTER VII 93
2. Fabrication of products from plate i.e. before that the material gets hardened by cold-ageing. If very extensive shaping is to be The general methods of aluminium They are best stored under cover done, you should do this in a alloy fabrication and the machines in a ventilated area and separat- time-span of a few minutes after used are not very different from ed by timber blocks to prevent the treatment to T1 or T4. those used for steel. Aluminium condensation stains. alloys are easy to fabricate. 1.3. 7000 series alloys However, their relative softness These extrusions are used in must be taken into account and some high-strength applications it is essential to use special tools within transportation, automo- to avoid damaging aluminium tive and sports equipment. The surfaces. Risks of contamination main alloy elements are zinc and from traces of ferrous and magnesium. cuprous metals must also be The extrusions are used in the T5, avoided as these can cause local- T6 or a T7 over-aged condition. ized corrosion. It is essential to FIGURE VII.1 The shaping may take place in work in an environment where the T1 or T4 condition, before such risks are minimized. STORAGE the material is artificially aged. More complex forming is done in 2.1. Storage the T4 condition, shortly after the solution heat treatment, Aluminium sheets are classified before ageing to T6 or T7. by family of alloy and stored Before using 7000 alloys, prior upright when more than 0.8 mm consultation with the supplier is thick (Figure VII.1). Thin sheets strongly recommended. (less than 0.8 mm) should be stored flat.
Aluminium sheets should never be placed directly on the ground, even if concreted, and should be kept away from splash water, condensation and hostile envi- ronments. 94 EUROPEAN ALUMINIUM ASSOCIATION ALUMINIUM IN COMMERCIAL VEHICLES CHAPTER VII
2.2. Marking out 2.3. Cutting to shape 2.3.2. Circular saw
Scribing tools should not be Plate or crocodile shears can be As with the band saw, the saw used, since any tracing marks used to make straight cuts. The pitch varies with the thickness or which might be left on the fin - rating of the shear should be section to be sawn but the process ished component can become more or less the same as for cut - of cutting, which is a function of crack starters under high loads. ting non-alloyed steel with low the machine characteristics, makes carbon content and the same it similar to milling (Figure VII.3). This precaution is not necessary thickness. FIGURE VII.3 where the scribe indicates a cut - SAW - MILLING OR CIRCULAR
ting line. Sawing is a common cutting
‰
process which is very economical t t ‰
‰ ‰
‰ As a general rule it is advisable to for aluminium alloys. t ‰ t – ‰ ‰ –
trace using a hard pencil (e.g. 3 p‰ ‰ 3
5H) which is easier to see and 2.3.1. Band saw ‰ 60° 60° ‰ ‰ ‰
h ‰ d ‰
easy to erase in case of error. ‰ ‰
The most common type of saw is ‰ ‰ 25° the band saw. This can be a sim - ple timber band saw but with a d: draw of 8° FIGURE VII.2 over 1 mm of width blade of specially designed pro - BANDSAW file to break and dislodge the aluminium chips from between
2,5 to 8 mm
‰ 1,8 t the saw teeth. With the band saw and circular ‰ ‰ ‰ saw, the cutting speeds for This is achieved by the alterna - 3000, 5000 and 6000 series tion or pitch of the teeth and by alloys are as follows: the clearance angle defined • HSS blade: 600 to 1000 m/min. ‰
55° Figure VII.2. • Carbide blade: 800 to 1500
‰ ‰ t ‰ ‰ m/min. 3° to 0° The portable milling saw is a tool that can be used to straight cut products up to 20 mm thick and THE CHARACTERISTICS OF A BAND SAW FOR ALUMINIUM ARE AS FOLLOWS: with good rates of advance. It may be preferable to use a jig - Diameter of flywheel • E (thickness) = saw for thicknesses of 6 mm or 1000 • Width = 10 to 30 mm less. The jigsaw is highly • Tooth pitch = 2.5 to 8 mm; two teeth must always be in action manoeuvrable and can be used • Lubricant = tallow or soluble oil. to cut complex curves. EUROPEAN ALUMINIUM ASSOCIATION ALUMINIUM IN COMMERCIAL VEHICLES CHAPTER VII 95
Water jet cutting (SAG)
2.3.3. Fluid jet of garnet, corundum or other Its performance is also excellent, very hard minerals are used. and in aluminium, thicknesses Metals, including aluminium between 1 and 100 mm can be alloys, can be cut using water The advantage of this process is cut at rates of 3500 mm/min jets bearing abrasive particles that it does not affect the metal - down to 30 mm/min for the larg - (PASER process) at high pressures lurgical condition of the product er thickness. (3000 bars and over). Granules and is very versatile. 96 EUROPEAN ALUMINIUM ASSOCIATION ALUMINIUM IN COMMERCIAL VEHICLES CHAPTER VII
2.3.4. Plasma Compared to traditional plasma, The plasma is formed in a special water VORTEX plasmas facilitate torch, and an inert gas (usually There are two plasma cutting greatly increased cutting speeds argon or nitrogen) moving at techniques (Figure VII.4): and reduce nuisance factors such great speed is dissociated under • traditional plasma, with a draft as smoke, noise, ozone discharge. the effect of an electric arc to of some 6°, The process requires substantial attain the plasma state. • water VORTEX plasma, with amounts of power however. a very small cutting draft, of the Owing to its high cutting speed order of 2°. (several metres per minute), its quality and precision of cut and FIGURE VII.4 suitability for automation, a plas - ma cutting machine can be a PLASMA TECHNIQUES highly profitable investment, even for short production runs. Plasmagen gas Plasmagen gas -
‰ - 2.3.5. Laser cutting ‰
‰ This process is mainly used in the ‰ ‰ automotive industry. Electrode Electrode ‰ More information can be found
in the Aluminium Automotive ‰
‰ ‰ Cooling Manual (www.eaa.net/aam). Copper water Water cone ‰ + + Note:
‰ The width of the heat affected Vortex water inlet Plasma column zone is less than 1 mm whatever Plasma in vortex Plasma in free air the alloy and for all thicknesses. However cracking is sometimes observed in the short transverse FIGURE VII.5 dimension (Figure VII.5) that can FIBRE ORIENTATION attain a depth of some 2 mm. Whatever the thickness of the ng product, machining off 2 mm of e lli
s ro r of e on ‰ n i material will restore the metal's v ect o s ir i D n ‰ t c a
‰ original qualities.
r n e o t i r t
i c
t ire d r ‰ l d This is obviously unnecessary if o ina
h ud
s t ‰ i the cut pieces are intended for Transve ong rse dire ‰ L ction use as welding blanks. EUROPEAN ALUMINIUM ASSOCIATION ALUMINIUM IN COMMERCIAL VEHICLES CHAPTER VII 97
2.4. Edge rolling 2.5. Bending 2.6. Non-machinable faces
This shaping technique requires For multiple folds, holes should As with bending, one worth - no special equipment for alu - be used to mark the crossover while precaution is to remove all minium. The rollers must of points of the fold lines to avoid score marks from the edges course be clean and have causing cracks when the folds caused by cutting so as to pre - smooth surfaces. are made. vent the formation of cracks at points of deep deformation. Aluminium does not require any special bending tools, and con - Shaping is carried out on the ventional table bending 5754, 5086 and 5083 grades machines or presses are perfectly (and on other alloys in the same adequate provided the working family) in the annealed or H111 parts of the tooling are free from condition. In some cases shaping unacceptable irregularities. may call for inter-stage anneal - ing 4, and this can be done as The bending radii to be observed described before using an as a function of the thickness are annealing torch and tallow as given in standard EN485-2. temperature indicator. Plasma cutting (Benalu) Inter-stage annealing can be carried out several times in the course of the shaping opera - tion; however care should be taken to avoid annealing a metal that is only slightly work- hardened to prevent the risk of grain enlargement.
4. For 5000 alloys with Mg content above 3%, this must be done very care - fully to prevent sensitization to inter - granular corrosion. See also Chapter XI, section 2.2.6. 98 EUROPEAN ALUMINIUM ASSOCIATION ALUMINIUM IN COMMERCIAL VEHICLES CHAPTER VII
3. Fabrication of products from extrusions
Extrusions are usually individually 3.1. Storage 3.2. Cutting protected in packing cases to prevent problems such as fret - Extrusions are best left in their The processes of sawing ting in transit. original packing cases until described above are also suitable required. As with aluminium for cutting aluminium extrusions sheets, they should never be set . down directly on the ground, 3.3. Bending even if concreted, and should be kept away from splash water, The bending of extrusions on an condensation and hostile envi - industrial scale may be carried ronments to prevent possible out with different methods and corrosion during storage. means.
3-point press bending (Benalu) EUROPEAN ALUMINIUM ASSOCIATION ALUMINIUM IN COMMERCIAL VEHICLES CHAPTER VII 99
3.3.1. Bending by 3-point 3.3.2. Bending by 3-point 3.3.3. Bending by press-bending press-bending with rotating compression bending dies This may be done when the bend A sliding tool forces the extrusion radius is small compared to the This process is typically using a to follow a circular die. The height of the extrusion section, tool in a press or a bending extrusion is not moving length - and when the accuracy (spring- machine. The rollers may be wise relative to the die. back) of the bend as well as the kinder to the extrusion work piece optics are not so important. It is than by the method in 3.3.1 due typically performed in a simple to less abrasive sliding action tool in a (mostly) hydraulic press. between tools and work piece. 100 EUROPEAN ALUMINIUM ASSOCIATION ALUMINIUM IN COMMERCIAL VEHICLES CHAPTER VII
Bending over rotating tools
3.3.6. Stretch-bending over a fixed tool (“swing arm stretch-bending”)
The ends of the profile are gripped to stretch-bend the profile against a fixed last which has the form of the finished product. In many cases this form may be a bending sweep built-up by compounded radii. Nearly all of the cross section of the extrusion will be subjected to tensile stress above the yield stress limit, and this applies to the full length of the work piece. This means that the spring-back effect on global shape will be little, con - stant and predictable. When a closed extrusion is formed in this way, the outer wall may be sub - jected to sagging. This may be countered by using a basic extru - sion with an outer wall which is barrel-shaped outward or by inserting a suitable elastic material (e.g. rubber). The operation may 3.3.4. Bending by 3.3.5. Bending by rotary be performed by a dedicated tool compression roll-forming draw bending in a press or in a stretch-bending machine. It is identical with 3.3.3, but with It is mostly performed in stan - a rotating wheel instead of the dard tube-bending machines. sliding tool. Very severe reforming may be made. It is usually per - formed in roll-forming machines with purpose-built tools. EUROPEAN ALUMINIUM ASSOCIATION ALUMINIUM IN COMMERCIAL VEHICLES CHAPTER VII 101
3.3.7. Stretch bending between extrusion and dies. 3.3.10. Mechanical calibration by rotating dies (rotary Rotary stretch bending can be of parts of the extrusion stretch bending) implemented in a dedicated press tool or in a stand-alone This is usually performed by com - By this method the extrusion is bending machine. pression-stretching or expansion- gripped at its ends and bent over stretching in a dedicated tool in a one ore two (normally two) 3.3.8. Three-dimensional press. rotating dies having a contour stretch-bending corresponding to the final prod - 3.3.11. Achievable bending uct shape. The stretching comes Over fixed or rotating dies (lasts), radius as a result of the rotation and the extrusion is gripped at its may effectively be controlled by ends, and stretched into a three- The achievable radii for bent the location of the rotary axes. dimensional shape (“out of the extrusions are highly dependent As opposed to the situation in plane”). This may be done with on the geometry of the profiles conventional stretch bending tools where the movements are and are difficult to predict. method (3.3.6), the bending defined mechanically, or in pro - Therefore it is advisable to carry starts at the end and propagates grammable tools or machines. out tests on specimen. Table VII.1 towards the centre of the extru - gives guidance for bending of sion. The primary bending 3.3.9. Manipulation hollow circular tubes. If smaller moment is generated by the of the cross section radii are needed, filling of the rotating dies, and is typically con - tubes with sand before bending stant along the workpiece. The This is usually performed by is helpful. process is characterized by very indenting or pressing in a dedi - low transversal (shear) forces and cated tool in a press. thus also low contact forces
TABLE VII.1 BENDING HOLLOW TUBES (D ≤ 90 mm ): BENDING RADIUS AS A FUNCTION OF RATIO D/ t
Ratio D/t Alloy Temper 5 10 15 20 25 30 5754 H111 1 to 1.5 D 2.5 to 3 D 3.5 to 4 D 4.5 to 5 D 6 to 7 D 8 to 9 D 6060 O 1 to 1.5 D 2.5 to 3 D 3.5 to 4 D 4.5 to 5 D 5 to 6 D 7 to 9 D T5 2 to 2.5 D 3 to 4 D 4 to 5 D 6 to 7 D 8 to 10 D 12 to 15 D
D: Outside diameter t: Thickness 102 EUROPEAN ALUMINIUM ASSOCIATION ALUMINIUM IN COMMERCIAL VEHICLES CHAPTER VII
4. Drilling
Drilling aluminium alloys is a sim - 4.1. Twist drill 4.3. Gun drill ple operation but calls for careful sharpening and polishing of the To have a substantial sharpening This type of drill is excellent for drills given the relative softness gradient, the helix angle must be large diameter holes of 20 mm of the aluminium alloys used in 40° while the point angle varies and over, also for drilling stacked the manufacture of commercial from 120° to 140° according to sheets. The drilling conditions are vehicles. If inadequate sharpen - the shape of the neck, with a the same as for the standard ing causes the drill to bend or clearance angle of 8°. The other twist drill. buckle, it will tear the metal characteristics of the twist drill around the part of the hole that are as follows: 4.4. Half-round or three is already drilled. • cutting speed 30 to 80 m/min quarter round drill depending on rating and the The following types of drill can be desired quality - for very accurate These drills are used mainly in used for drilling aluminium alloys 5: holes the ideal speed is 30 m/min, boring operations. The accuracy • the standard twist drill - the • penetration rate determined by of the bore diameter achieved most common type, the drill diameter: 0.05 mm/rev with these tools is of the order of • the straight flute drill, for a 2 mm diameter drill, to 0.3 0.02 mm: • the gun drill, mm/rev for a 30 mm diameter • cutting speeds are between 10 • the half-round or three quarter drill, and 15 m/min, round drill. • soluble oil cooling, • rate of advance is 0.05 mm/rev, • point height : this must • cooling is with cutting oil. exceed the thickness of the drilled material.
4.2. Straight flute drill
This drill facilitates rapid chip removal and is more efficient for aluminium alloys of medium hardness than the twist drill. The four cylindrical witnesses also prevent "triangulation" of the hole and provide drill guidance.
5. Steel twist drills can be used for small runs with mainly manual tools. EUROPEAN ALUMINIUM ASSOCIATION ALUMINIUM IN COMMERCIAL VEHICLES CHAPTER VII 103
5. Tapping
Threads in aluminium may be If threads are made in alumini - There are two methods of tapping: made, when other joining tech - um, care should be taken to • by chip removal, niques are not applicable 6. ensure that the thread length is • by upsetting. sufficient for the purpose. The thread length may be between 1
6. In a connection, where continuous and 2 times the major diameter joining methods such as welding or of the threads, and must depend bonding are used, no additional fasten - on the application, the alloy as ers should be applied. well as the te mper of the materi - Threaded holes in aluminium should al. For example, the necessary only be used where no other possibility exists and the yield strength of the metal thread length of a high strength exceeds 200 N/mm2. The bearing length 6000 alloy in T6 may be 1.2 times of the bolt should be 1,5 x diameter of the major thread diameter. the bolt. If the bolts must be used for repeated loosening and tightening, Conversely a softer alloy demands inserts should be applied e.g. Helicoils. a longer thread length.
TABLE VII.2 DIAMETER OF PILOT HOLES FOR THREAD TAPPING ∅ nominal 456810 12 14 16 18 20 Pitch 0.70 0.80 1 1.25 1.50 1.75 222.5 2.5 Diameter 3.2 4.2 4.9 6.6 8.3 10 11.7 13.7 15 17
5.1. Chip removal in the annealed condition must The cutting speed varies from 10 be some 3-5% bigger than in to 50 m/min depending on the Only taps with straight threads Table VII.2 and for castings with machine and method of clamp - should be used to avoid seizing 12 and more % silicon content ing the tap, whether floating or the metal at the flanks. Table some 2% smaller. in a chuck. Cooling is done with VII.2 gives diameters for pilot cutting oil. holes for tapping aluminium alloys in the 5000 and 6000 series. Pilot holes for these alloys 104 E UROPEAN ALUMINIUM ASSOCIATION ALUMINIUM IN COMMERCIAL VEHICLES CHAPTER VII
6. Deep drawing
5.2. Upsetting 5.3. Threaded inserts Deep drawing is mainly used in the automotive sector. The thread is achieved by plastic It is usual to use threaded inserts For more information on that deformation of the metal using a – available in diameters M2 to technique, please refer to the tap with- a rounded polygon sec- M68 (Figure VII.9) – when Aluminium Automotive Manual: tion that has no cutting wedge. screwed aluminium alloy assem- http://www.eaa.net/aam/ blies are required to be frequent- The diameter of the pilot hole ly dismantled. The inserts are in will depend on the desired the form of a spring made from thread depth, and must be rolled wire or are a diamond sec- drilled accurately. Upsetting tion made of stainless steel. speeds can attain 50 m/min, cooling is done with cutting oil. Captive threads can also be used. These have one or two flights Tapping by upsetting offers a that grip the flanks of the screw number of advantages with alu- thread and counteract the loos- FIGURE VII.9 minium alloys: ening effects of dynamic stress- HELI-COIL INSERTED THREAD • the tap has a long life, es, vibrations or thermal shock. • it increases the hardness of the Boring is done using a standard thread, its tearing resistance and twist drill, but tapping must be fatigue strength, done with a special tap. All chips • no chips. and cutting fluid must be removed from the bore before the insert is fitted.
Threaded inserts are fitted with pneumatic hand tools which
hold them by a driver at the top Notch end of the thread. This can then ‰ be broken off after fitting.
Threaded inserts can also be ‰ Driver used to repair a tap in aluminium that is worn or has been rejected during manufacture. EUROPEAN ALUMINIUM ASSOCIATION ALUMINIUM IN COMMERCIAL VEHICLES CHAPTER VII 105
Spinning of an aluminium tank-end (König)
7. Spinning
Spinning is a forming technique used in the commercial vehicle industry to make some compo - nents such as tank-ends.
7.1. Advantages of spinning
The tools used in spinning are very simple, being basically the internal shape of the required form. However production times can be up to 20 longer than for deep drawing.
Calculations combining the cost 7.2. Diameter of spinning ning, the diameter of the blank is of tooling and production costs blanks less critical for the success of a show that spinning is competitive part than it is in deep drawing, for short runs. Three formulae are used to and it is only the cost of the quickly determine the diameter material that dictates shape opti - of blanks for the most common mization. A simplified calculation shapes (Figure VII.10). In spin - is adequate for prototypes.
FIGURE VII.10 DIAMETER OF SPINNING BLANKS ‰
H ‰ h
‰ ‰
‰ ‰ D ‰ d D ‰ ‰ ‰
blank = D ×π blank = H + d blank =4 h + D ∅ 2 ∅ ∅ 3 EEUROPEAN ALUMINIUM ASSOCIATION CHAPTER VIII
WELDING
1. FOREWORD ...... 108 2. TIG WELDING (TUNGSTEN INERT GAS) ...... 109 2.1. Manual TIG welding ...... 110 2.2. Automatic TIG welding ...... 110 2.3. TIG welding with AC ...... 111 2.4. TIG welding with DC, reverse polarity ...... 111 2.5. Edge preparation for TIG welding ...... 111 2.6. Choice of filler wire or rod ...... 111 2.7. Selection of welding process ...... 111 3. MIG WELDING (METAL INERT GAS) ...... 112 3.1. Manual MIG welding ...... 112 3.2. Automatic MIG welding ...... 113 3.3. Smooth current MIG Welding ...... 113 3.4. Pulsed current MIG welding ...... 114 3.5. Wire pulsation ...... 114 3.6. CMT – Cold Metal Transfer ...... 114 3.7. Edge preparation for MIG welding ...... 115 3.8. Choice of filler wire or rod ...... 117 3.9. Selection of welding process ...... 119 4. PLASMA MIG WELDING ...... 118 5. LASER WELDING ...... 118 6. LASER MIG WELDING ...... 119 7. RESISTANCE WELDING ...... 120 8. FSW - FRICTION STIR WELDING ...... 120 9. SURFACE PREPARATION BEFORE WELDING ...... 122 10. QUALITY CONTROL ...... 123 10.1. Approval procedures ...... 123 10.2. Inspecting welded joints ...... 123 10.3. Weld defects & approval criteria ...... 124 11. DESIGN AND PREVENTION OF DEFORMATION ...... 126 11.1. Causes of deformation ...... 126 11.2. Solutions ...... 126 108 EUROPEAN ALUMINIUM ASSOCIATION ALUMINIUM IN COMMERCIAL VEHICLES CHAPTER VIII
Welder (STAS)
1. Foreword
Welding is the most common welds this layer must be removed are taken. One method of mini - method of joining used in the or at least broken up. mizing distortion is to select a manufacture of commercial vehi - Despite the fact that the melting process with small energy input. cles and their bodies e.g. tanks, interval of aluminium is by far tippers, dumpers, chassis etc. lower than that of steel, the high TIG and MIG arc welding are the The different physical, chemical thermal conductivity and the two processes most commonly and mechanical properties of high melting energy make that, used in the commercial vehicle aluminium compared with those for arc welding, aluminium industry. The technical progress of steel lead to the specific requires about the same amount made by other techniques such behaviour of aluminium during of energy as steel. as plasma, laser, resistance or welding. In an atmosphere con - friction stir welding and the ever taining oxygen, a well anchored The thermal elongation of alu - growing diversity of semi-fin - oxide layer builds up on alumini - minium is twice that of steel and ished products will encourage um. This layer has a melting point the loss in volume of the weld the application of such welding of some 2000°C against the pool during solidification is methods which have up to now melting interval of 630-660°C for important, causing distortion of been little used in the commer - the metal underneath. For quality the joint, if no remedial measures cial vehicle industry. EUROPEAN ALUMINIUM ASSOCIATION ALUMINIUM IN COMMERCIAL VEHICLES CHAPTER VIII 109
2. TIG welding (Tungsten Inert Gas)
In this process, an electric arc is positive phase ensures penetra- is weaker but the welding power struck between a refractory elec- tion and cooling of the electrode. is higher and products 10 to 12 trode made of tungsten and the TIG welding is suitable for metal mm thick can be welded with a workpiece, while a shroud of thicknesses between 1 and 6 mm. single pass. However this process inert gas, usually argon, shields is strictly for automatic welding the electrode and protects the There is a TIG version where heli- only owing to the difficulty of molten pool against oxidation. um is used as the shielding gas. keeping the arc at a constant This process uses a high-frequen- This helps achieving a high tem- controlled height within 0.5 mm. cy stabilized AC power source. perature in the arc but requires The oxide film is removed during direct current with straight polarity. the negative phase, while the The effect of oxide film removal
FIGURE VIII.1
PRINCIPLE OF TIG WELDING ‰ Tungsten Electrode Contact (for current) Welding Power Shielding Gas ‰ Source Shielding Gas Nozzle ‰ ‰
‰
Filler Metal
‰ ‰
Weld Seam ‰
Arc Work Piece 110 E UROPEAN ALUMINIUM ASSOCIATION ALUMINIUM IN COMMERCIAL VEHICLES CHAPTER VIII
2.2. Automatic TIG welding
Here, the welding torch is auto- matically guided and, if filler is TIG welding of an air pressure vessel (SAG) used, it is fed automatically from a reel. Automatic TIG welding is an attractive proposition for welding 2.1. Manual TIG welding into the weld pool. The manual large production runs, especially process is used mainly for small when there is no access to the For manual TIG welding, the filler welds, circular welds and rela- back of the weld. material is a hand-held rod fed tively thin components. The fabrication of compressed air reservoirs is a good example of the use of automatic TIG weld- ing. These reservoirs consist of a FIGURE VIII. 2 sheet rolled and welded to form MANUAL AND MECHANISED TIG WELDING the straight cylindrical centre sec- tion to which two deep-drawn ends are welded. If the ends are butt joined to the centre without any backing to prevent the prob- lems associated with moisture retention, automatic TIG welding can be used to make an easy connection. It is also possible to support the weld pool by supply- Manual TIG Welding Fully Mechanised TIG ing the argon from inside the Welding reservoir. EUROPEAN ALUMINIUM ASSOCIATION ALUMINIUM IN COMMERCIAL VEHICLES CHAPTER VIII 111
2.3. TIG welding with AC 2.4. TIG welding with 2.5. Edge preparation for DC, reverse polarity TIG welding It is especially well suited for butt and corner welds on pieces in In this process the arc length is In EN ISO 9692-3 this information the thickness range 1-6 mm. Full below 1 mm, ideally 0.5 mm, is given comprehensively, so that penetration welds can be made which means that it is mainly we just indicate a few examples without backing bar. Tack welds used for machine welding. For for typical joints in vehicle manu - must not be removed before exe - manual operation only short facturing (Table VIII.1, p. 115). cuting the seam weld. Changes lengths can be executed in prac - in weld direction are easy to fol - tice. One such application is To avoid sharp notches, especial - low with the torch and do not stitch welding of assemblies ly at the root of the weld, all require any dressing. The process before the seam welding. The edges must be carefully de- can also be used to smooth the small cross section of these burred before welding. Instead surface of a MIG weld. stitches is such that they are of grinding discs, milling tools The welding speed is lower than completely molten up while lay - should be used, because residues for MIG weld and, for work ing the first pass of MIG weld of the disc on the surface can pieces thicker than 6 mm, pre - over it and don’t need to be cause porosity in the weld. heating is required. The slow reduced in cross section by welding speed is also responsible mechanical means. for a wider heat affected zone 2.6. Choice of filler wire and greater distortion of the The oxide film removal is weaker or rod assemblies. with this process so it is neces - For fillet welds extreme care is sary to reduce the oxide layer by See section 3.8 needed to achieve full penetra - mechanical means before weld - tion without lack of fusion at the ing. root. 2.7. Selection of Welding In the tank and silo production, process double side TIG welding of butt welds in vertical upwards posi - See section 3.9 tion leads to excellent quality, provided the two operators con - trol the process well. 112 EUROPEAN ALUMINIUM ASSOCIATION ALUMINIUM IN COMMERCIAL VEHICLES CHAPTER VIII
3. MIG welding (Metal Inert Gas)
With MIG welding the alumini - polarity (i.e. minus to the work - 3.1. Manual MIG welding um alloy wire is both the elec - piece) to ensure removal of the trode and the filler material. It oxide film and the fusion of the In its manual version, MIG is cer - uncoils automatically from a reel wire electrode at the same time. tainly the most common weld - to the welding tool (gun or torch) ing process used in the commer - as it is used up. The welding Several MIG processes do exist... cial vehicle industry, producing energy is supplied by a DC power high quality welds at an attrac - source (smoothed current). tive quality/cost ratio. Connection is made with reverse As the filler wire, that is the con - sumable electrode, is always automatically fed from a reel, the FIGURE VIII.3 manual MIG welding is also PRINCIPLE OF MIG WELDING known as "semi-automatic MIG welding".
Manual MIG welding is used for ‰ all welds of a complex nature Wire Transport Rolls where the dimensions and thick - Wire Electrode ‰ ness of the products are compat - Contact Nozzle ible with the MIG process and ‰ (for Current) when automation is not consid - Welding Shielding Gas ‰ Power ered to be profitable. Nozzle ‰ Source If we consider the example of a tank consisting in sheets rolled ‰ ‰ and welded to form cylindrical
Arc ‰ sections, we can see that the lon - Workpiece gitudinal weld can be made by Weld Seam automatic MIG while the circular welds which join the sections to one another are usually made manually on a turntable in two opposing passes. The choice between manual or automatic MIG will depend largely on accessibility. EUROPEAN ALUMINIUM ASSOCIATION ALUMINIUM IN COMMERCIAL VEHICLES CHAPTER VIII 113
3.2. Automatic MIG 3.3. Smooth current MIG Thin gauge material below 3 mm welding Welding is difficult to weld with this process because of the high Here, the welding torch is auto - This fast and economical process energy of the arc. If no other matically guided. allows depositing a great quanti - equipment is available, then a This is normally used for very ty of filler metal per unit of time. thin gauge filler wire may be long straight welds where an The energy input is such that used with reduced energy input, automatic system is profitable. A butt welds can only be produced but then the wire feed can cause good example is fabrication of with the use of a backing bar, instability of the process even if a chassis side members consisting either integrated into the shape push-pull equipment is used. of two “T” sections welded to of the extrusion or as temporary If the preassembly of structures is either edge of a central plate removable feature in stainless carried out with stitches in the which forms the web of the steel, copper or even aluminium. MIG process, these short runs built-up beam. The two welds Due to the relatively high weld - must have a similar cross section would normally be made auto - ing speed, the heat affected as the first weld pass and be matically and at the same time to zone 1 is narrower than with TIG some 100 mm long to be sound. avoid problems of deformation. welding and thus the distortion Before production welding, these Automatic welding is also pre - of the assemblies is less. stitches must be reduced in cross ferred where an attractive section by mechanical means (no appearance is desirable, e.g. for disc grinders), so that they can stiffening channel welded to the be molten up with the weld pass 1. The extent of the heat affected zone side panels of vehicle bodies. and do not leave imperfections and the strength in the heat affected Here the appearance and size of zone are given in EN 1999-1-1. near the root. the weld bead can be repeated to achieve the impression of con - sistency. Finally, automatic welding - both TIG and MIG - provides a repeat - able welding quality provided of course that the welding parame - ters are fully defined to begin with.
Welding of side panels for tippers (Menci) 114 EUROPEAN ALUMINIUM ASSOCIATION ALUMINIUM IN COMMERCIAL VEHICLES CHAPTER VIII
Welding of a truck door
3.4. Pulsed current MIG The pulsed MIG process is limited the previously described “current welding to thin products of 2 < t ≤ 5 mm pulsation” in order to improve the and to vertical fillet welds. arc stability. This “wire pulsation” An improvement of the MIG This process makes it possible to induces a double pulsation to cur - proc ess has been achieved by weld thin gauge material with rent signal and consequently to superimposing a pulsed current standard filler wire. As the weld the heat input. For T-joint of dis - over the main current, the object pool can be better controlled, similar gauges, the heat input dis - being to maintain a low average butt welds up to 5 mm thickness tribution is difficult to maintain current level without sacrificing can be executed without backing constant with classical pulsed cur - arc stability. bar. Furthermore it is very helpful rent. This double pulsation of cur - The filler metal is transferred to for welding in the vertical and rent insures the concentration of the weld pool every time the cur - the over head position. The opti - heat input at the exact location of rent is high (i.e. one drop of metal mal machine setting is more the joint. per pulse). The "cold times" demanding than for standard when the current is low ensure MIG because there are much 3.6. CMT – Cold Metal that arc stability is maintained. more parameters to be defined. Transfer The width of the heat affected There are three operating modes: zone is analogue to the one for For MIG welding gauges lower • synergetic mode : only the standard MIG as is also the than 1 mm, the CMT process rate of uncoiling has to be regu - amount of distortion of the work (Cold Metal Transfer) could be lated. The voltage and frequency pieces. used. When detecting a short- are regulated by electronic logic For welding over stitches see circuit, this process retracts the circuits; remark under 3.3 above. wire so as to help detach the • manual mode : all the weld - droplet. The thermal input is ing parameters are adjustable; 3.5. Wire pulsation immediatly reduced and the • programme mode : each short-circuit current is kept small. parameter can be stored for For gauges between 1 and 3 mm, use according to production a complementary option “the requirements. wire pulsation” could be added to EUROPEAN ALUMINIUM ASSOCIATION ALUMINIUM IN COMMERCIAL VEHICLES CHAPTER VIII 115
3.7. Edge preparation for Just the most frequent examples For more details please consult MIG welding are given in the Table VIII.1 EN ISO 9692-3.
TABLE VIII.1 EDGE PREPARATION
Process Welding Weld Thickness Preparation Remarks position bead
TIG All positions One side only 0.8 < t <1.5 A slight peak formed by the edges limits deformation
TIG Horizontal One side only 0.8 < t < 5 Chamfered card, stainless steel support, clamped weld
TIG All positions One side only 1.5 < t < 5 Tack-welded free edges back-weld possible
80° Tack-welded free edges. TIG All positions One side only 4 < t < 6 Angle same principle but with offset bevel 2mm 1mm MIG All positions One side only 2.5 < t < 6 Back-weld necessary after with back-weld gouging to base of 1mm first pass
MIG All positions One side only 2.5 < t < 6 Stainless steel support
e e MIG All positions One side only 2.5 < t < 6
MIG Horizontal One side only 6 < t < 25 80° Back-weld necessary after and overhead* with back-weld gouging to base of first pass. 2mm 1mm Clearance: 1.5 mm max. 80° MIG Horizontal One side only 4 < t < 25 Ribbed stainless and vertical* steel support 1mm
* X-shaped bevels are preferred for components 6 mm < t < 25 mm to restrict deformation due to welding. 116 EUROPEAN ALUMINIUM ASSOCIATION ALUMINIUM IN COMMERCIAL VEHICLES CHAPTER VIII
TABLE VIII.2 CHOICE OF FILLER METALS AS A FUNCTION OF THE ALLOY COMBINATION
Each combination has three possible choices - indicated where the lines intersect - depending on the selected criterion: Optimum mechanical properties: top line – Optimum resistance to corrosion: middle line – Optimum weld - ability: bottom line The filler metal indicated is: 4 : series 4xxx ’ 4043A, 4045, 4047A – 5 : series 5xxx ’ 5356, 5183, 5556A
Alloy A Wrought 5 5000 Series 5 (a) Mg < 3% 4 - 5 (b) Wrought 55 5000 Series 55 Mg > 3% (a) 55 Wrought 5 - 4 5 - 4 5 - 4 6000 Series 55 5 44 4 Wrought 5 - 4 5 - 4 5 - 4 5 - 4 7000 Series 55 5 without copper 44 4 Cast 4 (e) 5 - 4 (e) 444 (d) Si > 7% 4 5 4 4 (c) 44 4 4 Wrought Wrought Wrought Wrought Cast Alloy B 5000 Series 5000 Series 6000 Series 7000 Series Si > 7% Mg < 3% Mg > 3% without copper (c)
(a) 5000 series alloys with more than 3.5% Mg are sensitive to intergranular corrosion when exposed to temperatures over 65°C and when used in certain aggressive environments (see section 2.2.6 in Chapter XI). (b) 5000 series alloys with less than 3% Mg and 3000 series alloys that contain magnesium may be sensitive to hot cracking. (c) The mechanical performance of the weld depends on the internal soundness of the castings. Gassed materials and injection mouldings are considered to be non-weldable. (d) The percentage of silicon in the filler wire must be as near as possible to that in the casting. (e) The welding of aluminium-silicon castings (40000 series) to 5000 series alloys should be avoided where possible as Mg2Si inter - metallics form in the weldment and weaken the joint. EUROPEAN ALUMINIUM ASSOCIATION ALUMINIUM IN COMMERCIAL VEHICLES CHAPTER VIII 117
3.8. Choice of filler wire or rod
Most of the alloys listed in of the best suited weld consum - The weld consumables should be Chapter V are weldable and also able, we distinguish between dif - stored in their sealed package combinations of these alloys are ferent requirements for the weld: and once a package is open, it possible. Welding consumables optimal strength, good corrosion should be kept in a dry atmos - are not available in exactly the resistance and weldability. A phere, because humidity on the same chemical composition as choice must be made according surface of the wire or rod causes the base metal to be joined. to the relative importance of porosity in the weld. If open reels There are wires and rods in the these three requirements. of filler wire are exposed to 4XXX and 5XXX series, namely ambient climatic conditions for a 4043A, 4045, 4047A, 5183, longer period (months), it is rec - 5356 and 5556A in the market ommended to dry them in a (see also ISO 18273). In the Table warming box at approx. 80 ° C for VIII.2 , with the recommendation one night before use.
3.9. Selection of welding process
TABLE VIII.3 SELECTION OF WELDING PROCESS
Process TIG MIG Atmosphere Inert Inert Electrode Refractory Consumable Current A.C. D.C. Smooth Pulsed Pulsed Pulsed Special effect Wire pulsation Cold Metal Transfer Suitability Thickness range (mm) 0.8 ≤ t ≤ 5 0.2 ≤ t ≤ 10 3 ≤ t 2 ≤ t 1 ≤ t ≤ 5 t ≤ 1 Manual yes no yes yes difficult no Automatic yes yes yes yes yes yes Industrial robot no no yes yes yes yes 118 EUROPEAN ALUMINIUM ASSOCIATION ALUMINIUM IN COMMERCIAL VEHICLES CHAPTER VIII
4. Plasma MIG welding
This process combines the high of the torch and the work piece, The process is well suited for melting capacity of the MIG the MIG arc is in the centre of applications with high require - process with the nearly ideal the plasma arc. Both arcs have ments for tightness and surface shape of the plasma arc and its the same polarity where the high aspect. It is possible to carry out very good gas shield for the kinetic energy of the plasma arc butt welds of up to 10 mm thick - welding pool. The result is an destroys the oxide layer on the ness in one pass with the edge extremely good quality of welds, work piece. Mechanical removal preparation in V. The welding especially the absence of porosi - of the oxide layer can be dis - speed is higher than for MIG ty. The plasma arc is maintained pensed with. welding. between the plasma ring nozzle
5. Laser welding
Laser welding of aluminium room, where during operation of The achievable welding speeds alloys is developing rapidly paral - the equipment, nobody without are up to 12m/min with thick - lel with the development of ever adequate eye protection has ness of around 1mm and still growing power of laser sources. access. The sensor which emits 1-3 m/min with thicknesses
There are on one side CO 2 lasers the signals necessary for the between 1.5 and 3 mm. of up to 20 KW and more and motion control of the laser beam Compared with standard arc Nd:Y AG lasers of 6 KW and must be very effective for not welding, laser welding allows the more. With the CO 2 laser, the ori - being disturbed by reflections. production of components with entation of the beam is limited, The process is mainly used for reduced geometrical distortions whereas with the Nd:Y AG laser thin gauge materials (1 – 4 mm) and residual stresses, as well as optical fibres allow to bring the and the pieces to be joined must narrower heat affected zone, a laser beam directly to the weld fit perfectly as is the case e.g. in direct consequence of the high zone. This gives high flexibility the production of tailored blanks work speed and thus the low especially for robot welding. The for the car industry. heat input. high reflectivity of aluminium The laser welding process is makes it necessary to install the preferably used with filler wire laser equipment in a separate for aluminium alloys. EUROPEAN ALUMINIUM ASSOCIATION ALUMINIUM IN COMMERCIAL VEHICLES CHAPTER VIII 119
Laser welding
6. Laser MIG welding
The combination of a standard The laser beam runs ahead of the one pass, where the require - arc welding process with the MIG arc but both focus on the ments for fit up of the pieces to laser welding process allows to same point of the metal surface. be joined is less stringent than benefit from the advantages of The shielding gas is provided by for pure laser welds. both processes, which are good the MIG torch. Preferably a mix - The same safety measures as for process stability, high welding ture of helium (70%) and argon laser welding must be applied. speed and enhanced bridging (30%) is used. This process is capacity. ideal for continuous automatic welds up to 10 mm thickness in 120 EUROPEAN ALUMINIUM ASSOCIATION ALUMINIUM IN COMMERCIAL VEHICLES CHAPTER VIII
7. Resistance welding
This technique is very common in For this reason, we do not give Interested readers should refer to the automotive industry and not details here. the Aluminium Automotive Manual: so widespread in the Commercial www.eaa.net/aam Vehicles industry.
8. FSW - Friction Stir Welding
rotational speed along the con - • Low distortion, even in long tact line between the two parts welds to be joined. The friction of the • Excellent mechanical proper - tool in the metal supplies the ties as proven by fatigue, tensile needed energy to heat the local and bend tests zone to the desired temperature. • No fume Through the rotation and the • No porosity translation of the tool the mate - • No spatter rial in the weld zone is plastically • Low shrinkage Friction Stir Welding deformed to create the weld. • Can operate in all positions The process can be used for butt • Energy efficient welds, overlap welds, T – sec - • No consumable tool ( one tool This is an innovative process tions and corner welds. For each typically can be used for up to which had been developed by of these joint geometries specific 1000 m of weld length in 6000 TWI Ltd (The Welding Institute) tool designs are necessary. The series alloys) and is protected by patents in process can be used in all posi - • No filler wire Europe, USA and Australia. tions i.e. horizontal, vertical, • No gas shielding Anyone using the process needs overhead and orbital. • No welder certification a license from TWI. • Some tolerance to imperfect The process operates in the solid The process can be used for weld preparations – thin oxide phase of the metal below the welds up to 50 mm thickness layers can be accepted melting point of the alloy. A tool from one side and up to 100 mm • No grinding, brushing or pick - in the form of a finger with a from two sides. Advantages are: ling required in mass production shoulder is rotated and moved • High productivity, i.e. low cost into the metal with a defined potential EUROPEAN ALUMINIUM ASSOCIATION ALUMINIUM IN COMMERCIAL VEHICLES CHAPTER VIII 121
Friction stir welded taillift profiles
The limitations of the FSW process • The relatively high investment Up to now the dimensionally biggest are continuously reduced by inten - requires a high degree of equipment can cope with work sive research and development. repeatability in order to material - pieces up to 20 m long. However, the main limitations of ize the cost saving potential the FSW process are at present: • Work pieces must be rigidly clamped. • Backing bar required (except where self-reacting tool or direct - ly opposed tools are used). • Keyhole at the end of each weld. • Cannot make joints which require metal deposition (e.g. fil - let welds). 122 EUROPEAN ALUMINIUM ASSOCIATION ALUMINIUM IN COMMERCIAL VEHICLES CHAPTER VIII
9. Surface preparation before welding
For quality welds it is recom - The metal to be welded must be degreased using a solvent such mended to machine the edges dry and without contamination as acetone or industry alcohol. (see section 3.7) of sheet to be of any grease or other products Avoid trichlorethylen, which welded after water jet, plasma or that evaporate under the action transforms under the effect of laser cutting to remove this of the arc. To achieve this clean the arc into the poisonous gas rough surface with a thick oxide surface, the pieces to be welded phosgene. When the solvent on layer and also with micro cracks should be brought into the work - the surface has evaporated, a in order to avoid weld defects shop two days before produc - further cleaning with a stainless such as cracks and oxide inclu - tion. This will allow condensation steel wire brush (hand-operated sions. The same should be done that might occur when the tem - or rotary) is recommended. for plate with thickness over 10 perature in the storage area is mm that has been sheared. lower than in the workshop to Outdoor welding is not advis - There is a great risk of cracks in dry off. able. If it cannot be avoided, the the short transverse direction, welding environment must be where a removal of 2 mm via Immediately before welding, the screened off. milling or routing is adequate. edges to be joined and their sur - roundings must be properly
Welding of tipper body (SCHMITZ) EUROPEAN ALUMINIUM ASSOCIATION ALUMINIUM IN COMMERCIAL VEHICLES CHAPTER VIII 123
10. Quality control
Quality control enables manufac - The level of acceptable defects is • the technical and financial turers to judge the quality of the determined by: impact of the failure of the weld - products they fabricate and more • the types and directions of ed structure, specifically to grade the quality load (static and dynamic), • the possibility of routine oper - of a welded joint against an • the levels and variations in ational inspection and control. acceptable level of defined stress, defects. • possible hazards to personnel,
10.1. Approval procedures 10.2. Inspecting welded joints
The procedures are either con - The type of inspection carried An inspection plan must be tractual between client and sup - out on welded joints will natural - made containing: plier or self-regulated by the fab - ly depend on the work rate of • extent of inspection before ricator. Welders must be certified the weldments. welding and qualified in accordance with In the fabrication shop it is possi - • extent of inspection and NDT EN ISO 9606-2. Welding proce - ble to perform the following • NDT methods to be used dure specification must be in non-destructive tests (NDT) in • acceptance criteria (quality level) accordance with EN ISO 15609- addition to visual inspection: in accordance with EN ISO 10042 1, EN ISO 15612, EN ISO 15613 • dye penetration tests are valu - and EN ISO15614-2. able for detecting leaks and Test specimens must be submit - emergent cracks, ted for tensile or bending tests. • weld shape tests (geometrical Bending tests are important shape), because they: • radiography, used to detect • detect bonding that is hard to internal defects (porosity, cracks, identify in non-destructive testing, inclusions) in butt joints, • help achieve a good balance • ultrasonic tests of parameters with a view to pre - It may also be prudent to per - venting these defects. form some destructive tests on reference specimens. 124 EUROPEAN ALUMINIUM ASSOCIATION ALUMINIUM IN COMMERCIAL VEHICLES CHAPTER VIII
10.3. Weld defects & approval criteria
Weld defects and quality levels is given in EN ISO 6520-1 which • Group 400: Lack of fusion and are given in EN ISO 10042. lists 6 groups of imperfections: penetration Guidance for choice of quality • Group 100: Cracks • Group 500: Defects of shape level is given in EN 1090-3. • Group 200: Cavities and worm - • Group 600: Sundry defects An international nomenclature of holes defects has been established and • Group 300: Solid inclusions
TABLE VIII.4 LISTS SOME COMMON WELD DEFECTS AND THEIR CAUSES
N° Type of Defect Likely Cause Photos of Imperfections
101 Cracks Base alloy unsuitable Poor choice of filler metal Incorrect welding sequence Excessive clamping Sudden cooling
104 Crater cracks Pass finished with sudden arc cutoff Defect 101 2012 Irregular wormholes Work inadequately degreased Work and/or filler wire dirty or wet Insufficient protection by inert gas (low gas flow or leak in the system) Pass begun on cold component High arc voltage Weld cooled too quickly
2014 Aligned wormholes Incomplete penetration (double pass) Defect 104 Temperature gradient between backing and work too abrupt Excessive gap between edges of the joint
300 Solid inclusions Dirty metal (oxides, brush hairs)
303 Oxide inclusions Poor gas shielding
Metal stored in poor conditions Defect Castings 2012 EUROPEAN ALUMINIUM ASSOCIATION ALUMINIUM IN COMMERCIAL VEHICLES CHAPTER VIII 125
N° Type of Defect Likely Cause Photos of Imperfections
3041 Tungsten inclusions Electrode diameter too small (TIG) Poor handling by welder Excessive current density Poor quality of tungsten electrode
402 Incomplete penetration Inadequate cleaning (presence of oxide) Incorrect bevel preparation on thick work Defect 300 (too tight, excessive shoulder) Gap between workpieces too small (or incon-sistent) Low current, especially at the start of the seam Welding speed too fast High arc voltage Defect 402 4011 Lack of fusion High arc voltage on edges Low current, especially at the start of the seam Work cold (difference in thickness between materials to be welded)
502 Excessive thickness Poor power control (poor U/I match) Defect 402 Welding speed too slow Poor edge preparation on thick work Insufficient starting current
507 Misalignment Work positioned incorrectly Incorrect welding sequence
508 Angle defect Excessive welding power Defect 502 Incorrect welding sequence
509 Collapse Wire speed too fast Torch speed too slow Poor torch guidance
602 Splatter (or beads) Incorrect arc control Problem in electrical contact to ground Defect 507 126 EUROPEAN ALUMINIUM ASSOCIATION ALUMINIUM IN COMMERCIAL VEHICLES CHAPTER VIII
11. Design and prevention of deformation
11.1. Causes tank and by which the bulkhead 11.2. Solutions of deformation is welded to it. This approach should prevent the problem of There are a number of solutions In machine welded structures, punching due to the weld con - to the above problems: deformation can be caused by: tracting and should minimise deformation (Figure VIII.4). 11.2.1. Use of extrusions 11.1.1. The direction Similarly, where the body of a of the welds tank has to be stiffened, it is It is worthwhile using extrusions essential to place a support plate in the fabrication of chassis as It is a well known fact that a bead between the stiffener and the this can help to: contracts most at the end of the skin of the tank to prevent defor - • position assemblies in less weld, which is why the greatest mation by the effect of punching stressed areas, deformation occurs in the end due to weld contraction (Figure • make welds that eliminate zones. So far as possible therefore VIII.5). In the absence of a sup - deformation. it is essential to orient the weld port plate the tank would towards the outside of the work - deform under the effect of sub - piece so as to release as much sequent dynamic stresses. stress as possible. Otherwise, with FIGURE VIII.4 the weld facing the middle of the UPSTAND WELDING component, the contraction stresses are “trapped” and defor - mation will be greater as a result. The end of the weld must be fin - ished to prevent any danger of cracking on the end crater.
11.1.2. The effect of punching
This is normally due to design
error. If we take the example of a bulkhead inside a tank, it is ‰ essential that the bulkhead, which is either deep-drawn or Upstand spun, has a down flanging rest - ing flat against the body of the EUROPEAN ALUMINIUM ASSOCIATION ALUMINIUM IN COMMERCIAL VEHICLES CHAPTER VIII 127
Chassis side members for 11.2.2. End stops 11.2.3. Predeforming instance are usually fabricated from two extrusions forming the These must be positioned so as Some weld deformations can be two flanges of the member and to allow free elongation of the offset by predeforming the areas a sheet for the web. assemblies during welding. to be welded in such a way that The assembly shown in Figure "Compressing" a weld, i.e. pre - the assembled components VIII.6 can be automatically MIG venting its elongation, greatly "come right" after welding. welded with two welding torch - exaggerates contraction and If the metal is only predeformed es operating simultaneously. hence subsequent deformation. in the elastic zone by clamping, Both methods of butt joining are the results can be very erratic, possible, i.e. with the side mem - and it is therefore advisable to ber positioned vertically or hori - predeform by bending the metal zontally. The choice of position in the plastic zone. In this way, will be dictated chiefly by the the results will be predictable design of the welding bench. and repeatable. When the side member is hori - zontal a support will be needed to counteract angular deflection.
FIGURE VIII.5 FIGURE VIII.6 WELDING WITH SUPPORT PLATE FABRICATING A CHASSIS MEMBER
‰ ‰
Horizontal (flat)
Vertical (flat)
‰ ‰ EEUROPEAN ALUMINIUM ASSOCIATION CHAPTER IX
OTHER JOINING TECHNIQUES
1. ADHESIVE BONDING ...... 130 1.1. Definition ...... 130 1.2. Advantages and disadvantages ...... 131 1.3. Types of adhesives ...... 131 1.4. Application of adhesives ...... 132 1.5. Creep and ageing ...... 133 2. SCREWING AND BOLT FASTENING ...... 133 3. RIVETING ...... 133 4. SNAP-LOCK & CLIPPING ...... 135 130 E UROPEAN ALUMINIUM ASSOCIATION ALUMINIUM IN COMMERCIAL VEHICLES CHAPTER IX
1. Adhesive bonding
1.1. Definition FIGURE IX.1 PRINCIPLE OF ADHESIVE BONDING Adhesive bonding is defined as a process of joining parts using a ADHESION non-metallic substance (adhe- Physical attraction forces Chemical bonding Mechanical interlocking sive) which undergoes a physical between adhesive and between adhesive between adhesive and metal surface molecules and metal or chemical hardening and by surface roughness of atoms the parts to be joined thus leading to a joining of the parts through surface forces (adhesion) and internal forces (cohesion).
Adhesion can be physical attrac- tion between the adhesive and the metal surface, real chemical bonding between the adhesive molecules and the metal atoms or mechanical interlocking between the adhesive and the surface roughness of the metal. Cohesion is the inner strength of the adhesive itself as a result of physical and/or chemical COHESION Physical and/or chemical interaction forces between the components between the adhesive molecules of the adhesive. Source: Talat lectures EUROPEAN ALUMINIUM ASSOCIATION ALUMINIUM IN COMMERCIAL VEHICLES CHAPTER IX 131
1.2. Advantages and disadvantages
Advantages Disadvantages
1. Load distributed uniformly at right 1. Influence of time on process properties angle to loading direction 2. Pre-treatment of joined surfaces 2. Microstructure unaffected necessary
3. Distortion-free joining 3. Limited form stability
4. Different materials can be joined 4. Process parameters must be held in narrow ranges 5. Very thin parts can be joined 5. Change of the properties in time 6. Weight saving (ageing of the adhesive) 7. Heat-sensitive materials can be joined 6. Complicated control of process 8. Metals with different electrochemical 7. Low peeling strength potentials can be joined (insulating effect of adhesive) 8. Low adhesive layer strength requires large joining areas 9. High strength joining in combination with other methods (screwing, 9. Limited repair possibilities welding…) 10. Difficult strength calculation 10. High fatigue strength and good vibration damping
Source: Talat lectures 1.3. Types of adhesives
Combination of adhesive bonding Adhesives can be divided into 3 sub - reaction. Thermoplastics like and mechanical joining (e.g. rivet - groups depending on their forming polyamides and polysulfones as ing or bolting) can eliminate some reaction and polymer structure: well as duromers like phenol of the above-listed disadvantages. • Polymerisation: An exothermic formaldehyde resins, urea resins, process in which monomers link melamine resins and polymides, are together to form macromolecules all produced by polycondensation. (polymers). Thermo plastics like • Polyaddition: During this methylacrylates, polyvinyl chlo - process the hydrogen atoms are rides, polyvinyl acetates and rub - rearranged. Very common adhe - ber polymers belong to this group sives for metal bonding like • Polycondensation: Water is pro - epoxy resins and polyurethanes duced as a result of the chemical are produced by polyaddition. 132 EUROPEAN ALUMINIUM ASSOCIATION ALUMINIUM IN COMMERCIAL VEHICLES CHAPTER IX
Prototype floor section made of bonded sheets and extruded stiffeners
1.4. Application of adhesives
As adhesive bonding is working by surface forces, prerequisites for a well functioning adhesive joint are a) the choice of an appropriate adhesive for the materials to be Patented by Alcan combined b) the existence of a suitable material surface The joint construction should be 1.5. Creep and ageing related to the adhesion process A suitable surface means, that and its requirements for large The durability of adhesive joints the surface area must be large bonding areas. Peeling and depends on factors such as prop - enough to transfer the applied cleaving forces on adhesive er pre-treatment, chemical com - forces and that it is capable to joints must be avoided and position of the adhesive and ensure a proper bonding. This bending forces should be service conditions like stresses, can be achieved through a reduced to a minimum. temperature, humidity and expo - suitable pre-treatment. Any The adhesive can be applied sure to ultraviolet radiation (poly - residues of dirt like moisture, manually (e.g. with the use of mers are sensitive to this kind of oils, dust etc. must be removed cartridges) or for larger areas radiation and tend to lose their prior to application of the adhe - with automated machines. The mechanical properties). sive. This can be done by chem - bonding should take place in a The ageing of bonded joints can ical means with the use of dry and well ventilated and be caused by creep under stress detergents, degreasers or etch - dust-free workshop. (creep can be defined as time- ing agents or mechanically by The work must be done in strict dependent increase in the grinding. In any case the surface compliance with the manufactur - length of visco-elastic sub - must be absolutely clean before er s rules. The production param - stances subject to a constant gluing. It might be favourable to eters such as resin/hardener ratio, tensile load). use a primer for better wetting duration and pressure component Adhesive joints should therefore of the metal surface by the fit up during adhesive curing, curing be inspected regularly to pre - adhesive as well. temperature, etc. must be con - vent damages and to enable trolled properly. repair prior to a possible failure. EUROPEAN ALUMINIUM ASSOCIATION ALUMINIUM IN COMMERCIAL VEHICLES CHAPTER IX 133
2. Screwing and bolt fastening
Bolting creates a joint which can steel and aluminium (e.g. the result of the calculation of the be opened and closed as many connection between chassis and applied stresses. In the combina - times as necessary. It is besides tank or tipper body). Special tion of steel screws with alumini - welding the most conventional precautions should be taken to um plates, the risk of galvanic method for joining metals. In avoid galvanic corrosion, please corrosion must be consid ered: contradiction to welding, differ - refer to Chapter XI. insulating gaskets should be ent metals can be joined. In placed around the contact area commercial vehicles this is most The choice of the fastening between both metals. likely the connection between geometry will depend on the
3. Riveting
Riveting is today a widespread • Optical appearance: Machine Conventional can be sorted into joining method in different sec - riveting can be combined with a three families: tors of industry, including com - plastic capping of the rivet • Lockbolts which visually look mercial vehicle construction. As • It does not require skilled like they create the same type of it is a very safe and easy-to- operators connection as a conventional apply technique, riveting has • Mixed joints are possible: dif - bolt, but unlike conventional become a very common method ferent metals, plastics, sandwich nuts and bolts; they will not for joining assemblies e.g. in the or honeycomb panels work loose, even during construction of the bodies of extreme vibration. They can only refrigerated trailers. Rivets can be divided into be used when both sides of the 2 main subcategories: self pierc - joint are accessible. Lockbolts Machine riveting has a lot of ing rivets and conventional riv - consist of a pin which is inserted advantages: ets which require holes that in the hole and a collar which is • High-speed: Machine riveting must be drilled prior to riveting. placed on the pin from the allows fast operations with the use opposite end. The tool is placed of pneumatic or hydraulic tools over the fastener pintail and • Ease of control: the clamping activated, the pin head pulls force is always guaranteed by against the material, the tool the system as it is less than the anvil then push’s the collar force needed to snap the rivet against the joint, at this stage 134 EUROPEAN ALUMINIUM ASSOCIATION ALUMINIUM IN COMMERCIAL VEHICLES CHAPTER IX
FIGURE IX.2 LOCKBOLTS
the initial clamp is generated. The tool then swages the collar into the pin. The pintail then breaks and the installation is complete (Figure IX.2). Lockbolt strength FIGURE IX.3 characteristics BLIND RIVET Clamp force or pre-load: dur - ing the installation process, as the tool engages and pulls on the pintail, the joint is pulled together before the conical shaped cavity of the nose assembly is forced down the collar, progressively locking (swaging) it into the grooves of the harder pin. The pin and FIGURE IX.4 swaged collar together form the installed fastener. SELF-PIERCING RIVET The squeezing action reduces the diameter of the collar, increasing its length, which in turn stretches the pin, generat - ing a clamp force over the joint. Shear strength of lockbolts varies according to the materi - al strength and minimal diam - eter of the fastener. By increas - • Blind rivets , which are used rivet part of the bolt is pierced ing the diameter or the grade when only one side is accessible. through the metal sheet. The of material, the shear strength Blind rivets are characterised by further closing motion of the of the fastener can be breaking off of the rivet stem tool, together with the specially increased. after fastening the connection shaped counter die causes the The tensile strength of lock - by deformation of the rivet rivet head to be formed in such bolts is dependent on the (therefore they are often called a way that the pierced sheet is shear resistance of the collar “breakstem rivets”). (Figure IX.3) covered over in the joining material and the number of • Self piercing rivets do not region. (Figure IX.4). grooves it fills. require previous drilling. The EUROPEAN ALUMINIUM ASSOCIATION ALUMINIUM IN COMMERCIAL VEHICLES CHAPTER IX 135
4. Snap-lock & clipping
The Snap-Lock is a design which FIGURE IX.5 uses serrated components mak- CLIPPING PRINCIPLE ing assembly easy and quick.
The snap-lock design allows sid- ing to be notched and locked into place without face nailing.
Stresses are distributed over the entire length of the profile and not merely concentrated on the mechanical fixing point (rigidity).
Reefer floor assembled by bonding (Schmitz) EUROPEAN ALUMINIUM ASSOCIATION CHAPTER X
DECORATION AND FINISHING
1. FOREWORD ...... 138 2. POSSIBILITIES WITH ALUMINIUM ...... 138 3. MECHANICAL FINISHING ...... 139 3.1. Brushing ...... 139 3.2. Polishing / Buffing ...... 139 4. CHEMICAL DECORATION ...... 141 4.1. Anodizing ...... 141 4.2. Painting ...... 141 138 EUROPEAN ALUMINIUM ASSOCIATION ALUMINIUM IN COMMERCIAL VEHICLES CHAPTER X
1. Foreword
Although aluminium can be used is most likely to use different sur - tect it from severe atmospheric without any surface protection face treatment methods to opti - conditions and to give space for and keeps its natural beauty mise the attractiveness and opti - company logos or advertise - throughout a whole trailer life, it cal appearance of a trailer, to pro - ments.
Aluminium tanker (Trailor)
2. Possibilities with aluminium
There are several methods for softness of the surface and the - Polishing (or “buffing”) decoration and finishing of an existence of the oxide layer have • Chemical Finishing aluminium surface. Although all to be considered. - Anodising of the methods used for other - Painting materials are applicable, special There are 2 main methods of Today, painting is the most com - attention has to be paid to alu - decoration and finishing: mon way to decorate trucks and minium s characteristic proper - • Mechanical finishing trailers. ties. In each case, especially the - Brushing EUROPEAN ALUMINIUM ASSOCIATION ALUMINIUM IN COMMERCIAL VEHICLES CHAPTER X 139
3. Mechanical finishing
3.1. Brushing 3.2. Polishing / Buffing Mirror finished plates are fabri - cated in the rolling mill by the Brushing is a rather seldomly Polishing or buffing is a quite use of a special rolling routine used method for the decoration common method in the North with work rolls which have near - of trucks and trailers. It can American market to provide a ly no surface roughness. This mostly be seen on tankers for decorative surface finish. 3 main makes it a very demanding the transport of fluid goods. methods can be applied: process and great care must be Like polishing, brushing is based • Use of mirror-finished alumini - taken to secure a reliable and on abrasion effects between the um sheets and plates fabricated constant quality of the sheets. brush surface and the alumini - in the rolling mill um surface. Due to the brush • Polishing / buffing of mill finish Buffing or polishing of large being the harder part, alumini - sheets to the desired surface plates is done on automatic lines, um is removed from the surface appearance where the surface is polished by an abrasive effect. Brushing • Manual polishing with rotary polishers across the is done with rotary brushing whole width of the sheet at the tools or machines. Normally no The use of mirror-finished plates same time. The rotary polishers additional brushing compounds or the use of already buffed or have special pads on their sur - or chemicals will be used. polished sheets has the advan - face, which polish the aluminium tage, that the work on site is surface under the help of polish - Like for every surface treatment of reduced to the manual polishing ing compounds. The polishing aluminium, the part to be brushed of weld seams or places which compounds works as a slight has to be cleaned and degreased have been damaged during fab - abrasive and removes the top properly before applying the rication. Great care must be layer of the aluminium surface in brushing process. The cleaning is taken when handling or working the range of the surface rough - done to remove any dust, dirt, oil, with these sheets, as every little ness produced by the rolling mill. emulsion or other residues from trace of a mechanical defect As the result of polishing is very the rolling process prior to brush - caused by fabrication must be much depending on the type of ing and to prevent particles from manually polished. alloy and temper, the surface being squeezed into the surface hardness, the type of polishing during brushing. To secure a uni - paste and the machine setting form surface appearance, it is of (like rotational speed, pressure great advantage to use an auto - and type of pad), this is a method matic process with several brushes of “trial and error” to find the in one single station, which are right setting per specification. simultaneously controlled. 140 EUROPEAN ALUMINIUM ASSOCIATION ALUMINIUM IN COMMERCIAL VEHICLES CHAPTER X
ting abrasive paste. The pad should be a wool compounding type. Speed of the polisher must be limited to prevent burning of the surface. The polisher should be moved back and forth, up and Aluminium tank (LAG) down to ensure a uniform abra - sion of the surface. As the pad will suddenly turn black (caused by the polishing residue), great care must be taken to regularly clean or change the pad. After the rough first polish, the type of paste should be changed to one with lower abrasion. Before applying the final polishing step, it is useful to clean the surface again to remove the black residue, which might be trapped into the surface. The final result of manual polishing should be a mirror-like, uniform, swirl-mark, black speck- and bright sparkle- free surface. Aluminium tipper (Benalu)
To keep the mirror-like surface In any case, before polishing, the The same rules apply for manual throughout a long period, it aluminium plates should be polishing. This process is difficult makes sense to apply a clear coat degreased and cleaned to remove to apply and a large and exten - system, as exposure to normal any kind of dust and dirt to prevent sive experience is necessary to atmosphere would lead to a abrasive particles from being reach a satisfactory and repro - bleaching of the polished surface. ground into the aluminium surface. ducible result. After removal of surface dirt or oil, the manual process starts with a rotary pol - isher and the use of quick- cut - EUROPEAN ALUMINIUM ASSOCIATION ALUMINIUM IN COMMERCIAL VEHICLES CHAPTER X 141
4. Chemical decoration
4.1. Anodizing certain thicknesses of the oxide 4.2. Painting layer (in the range of 1000 times Anodizing is an electrochemical pro- of the natural oxide film). 4.2.1. Introduction cess to reinforce the natural oxide Anodising not only produces film on the aluminium surface. most frequently a silver- matt sur - Painting is the most usual way of face, but at the same time decoration for commercial vehi - Anodising is done in a sulphuric enables increasing hardness, cor - cles. Due to the natural oxide solution at a certain electric cur - rosion resistance and resistance to film on the aluminium surface, it rent. The natural oxide film is abrasion. The process is applied is of vital importance for a well thereby newly built and the discontinuously on components adherent and durable organic process can be controlled to reach like castings, extrusions and plates coating to apply an efficient sur - or continuously on coils. face preparation.
FIGURE X.1 The structure of the anodic film is It is therefore not sufficient to STRUCTURE OF THE ANODISED LAYER determined by the process clean the bare aluminium surface parameters (type of bath, applied and to degrease it prior to paint current etc.) and consists of application. It is essential to Pore Sealed hexagonal cells. The center of the remove also the natural oxide cells cells includes a micro-pore with a layer, because it disturbs adhe -
‰ diameter of nanometers. These sion of the paint system. ‰ pores have to be sealed to close This can be done in 2 ways:
‰ them and to guarantee an excel - Chemical pre-treatment lent corrosion resistance. This is by etching (after degreasing done in boiling water under the or by a combine Cell wall use of sealants. (Figure X.1) degreasing/etching process) ‰ Degreasing of aluminium sur - Notch faces can be done with fluid
‰ degreasing solvents, supplied ‰ e.g. by paint producers. The objective of cleaning and
‰ degreasing are: Barrier layer (base of the Aluminium • to remove any kind of fatty or cell) oily residues, or traces of dirt and dust from the surface • to prevent electrostatic charging. EUROPEAN ALUMINIUM ASSOCIATION ALUMINIUM IN COMMERCIAL VEHICLES CHAPTER X 142
Cleaning before painting (LAG)
To apply a degreasing solvent acidic solutions with phosphoric machine. It is essential to use properly, it is necessary to wipe acid or nitric acid. Etching leaves iron-free blasting abrasives like the surface with a fresh mois - a rough and very moisture-sensi - non-recycled corundum, as iron tened cloth and then clean it tive surface behind. It is therefore can lead to corrosion problems 1. with a new, fresh and dry cloth. essential to rinse carefully with The rate of abrasion during blast - Aluminium has amphoteric prop - fresh water after etching (about ing is very low and well below erties, which means that it can 20 minutes). 0.1 mm and therefore in the be dissolved either in an acidic or same range as etching. alkaline environment. Etching of Mechanical treatment After grinding (which is also used commercial vehicles is normally by grinding or blasting to flatten the welding seams and done by applying the etching Grinding is to be done on a clean to plane out scratches) or blast - agent by spraying. Alkaline etch - and degreased surface to prevent ing it is necessary to remove ing agents are based on caustic oil being trapped into the alumini - traces of the abrasives by com - soda, silicates, phosphates, car - um, which could lead to adhesion pressed air and then to clean the bonates and sodium hydroxide. problems of the paint. The grain - surface again. The concentration of sodium ing of the grinding disk should hydroxide and the temperature have a grain size of 120-180. of the etching agent have a large Blasting allows a more uniform 1. The incrustation of iron particles on influence on the speed and rate treatment of the vehicle and the aluminium surface is a source of gal - vanic corrosion that will lead, in the of the etching process. Etching reaches areas which cannot be presence of moisture, to superficial can also be done on the base of reached by a manual grinding micro-pitting. EUROPEAN ALUMINIUM ASSOCIATION ALUMINIUM IN COMMERCIAL VEHICLES CHAPTER X 143
4.2.2. Application of the primer The final coating system can be sep - • Removal of unevenness with a arated into 2- or 3-layer systems filler; grinding of the filler layer The primer should be applied with or without the use of fillers and • Removal of dirt and dust by directly after the pre-treatment of basecoats. Fillers are needed to flat - wiping with a moisturized cloth the surface to prevent the rebuild - ten unevenness and/or to increase • Application of the 1st paint ing of the oxide film or to prevent thickness of the coating system. layer (basecoat or wet-in-wet any dust being attracted by the For preparation of the surface, the filler) in 2 steps with a combined vehicle during longer periods of primer layer has to be ground with layer thickness of 60-70 µm. waiting time. Primers (or “wash a smooth grinding disk (roughness Special attention should be paid primers”) are used as adhesive 300-400). Fillers have also to be to the area of stone chipping. agents to maintain the necessary ground before application of the • Application of the topcoat bonding forces between the sub - topcoat system. (clear-coat) in the desired colour strate (aluminium surface) and the The paint is normally applied with after max. 2 hrs. Final coating paint system. They are also work - spray guns. Drying times and tem - thickness 50 – 60 µm. ing as corrosion inhibitors, as they peratures have to be controlled. It • Drying of the top layer prevent water vapour diffusion might be necessary to apply an Extrusion profile systems used e.g. through the paint system from intermediate fine grinding of the in tipping trailers can be painted getting in contact with the alu - single paint layers. in 2 ways: either the trailer can be minium surface. Primers made of A typical painting procedure of a painted as a whole or the profiles epoxy- resins are a well suited silo tank trailer could be 2: can be painted individually and material for pre-treating alumini - • Etching / degreasing inside and then being assembled. The gener - um, but need a thoroughly treat - outside by spraying with an inhibit - al rules for decoration mentioned ed bare metal surface. The primer ed etching agent based on phos - above are also valid for these is normally applied by spray gun phoric acid types of constructions. and the thickness of the wash • Rinsing with fresh water for In any case it is essential for a suf - primer or reaction primer layer is about 20 minutes ficient and long lasting paint dec - about 10 μm. • Final assembly of the vehicle oration to apply a well conduct - • Grinding of the tank surface with ed preparation of the surface as 4.2.3. Final coating a manual grinding machine to mentioned before. Problems with remove small surface damages the paint decoration often are The application of the final coating • Cleaning and degreasing with not related to the paint or the system can be done in different degreasers or silicone removers aluminium itself, but more with ways, but is anyhow not specific for • Application of the wash primer an insufficient pre-treatment. aluminium. In any case, it is of vital onto the outer tank surface. Layer importance to use paint systems thickness 8-10 µm. with coordinated properties. The • Drying of the tank at room tem - 2. Koewius, Gross, Angehrn Aluminium - technical rules of the paint suppliers perature (20°C) or at elevated tem - Konstruktionen des Nutzfahrzeugbaus , have to be strictly obeyed. peratures up to 80°C Aluminium Verlag, Düsseldorf, 1990. EUROPEAN ALUMINIUM ASSOCIATION CHAPTER XI
CORROSION RESISTANCE
1. DEFINITION OF CORROSION ...... 146 2. CORROSION OF ALUMINIUM ...... 146 2.1. The natural oxide layer ...... 146 2.2. Types of aluminium corrosion in commercial vehicles ...... 147 2.3. Further references ...... 151 146 E UROPEAN ALUMINIUM ASSOCIATION ALUMINIUM IN COMMERCIAL VEHICLES CHAPTER XI
1. Definition of corrosion
Corrosion is a electrochemical to impairment of the function of Corrosion can occur locally (“pit- interaction between a metal and the metal, the environment, or ting”), or it can extend across a its environment which results in the technical system of which wide area to produce general changes in the properties of the these form a part (definition as deterioration. metal and which may often lead per EN ISO 8044).
2. Corrosion of aluminium
2.1. The natural oxide layer
A clean aluminium surface is very which are present in seawater or Vehicle manufacturers or fleet reactive and will react sponta- road salts. operators should contact the alu- neously with air or water to form Some alloying elements might minium supplier in any case of aluminium oxide. This oxide increase the corrosion resistance critical working conditions like builds a natural protective layer of the oxide layer, while others elevated temperatures or aggres- on each aluminium surface with can weaken it. sive loads. a thickness of around 1 – 10 nm. The oxide layer is chemically very FIGURE XI.1 stable, has a good adhesion to the metal surface, repairs itself and protects the aluminium from further corrosion. (Figure XI.1) Natural oxide The oxide layer can be destroyed layer (Al2O3) in strong acidic or alkaline envi- ronments or where aggressive ions are present. Aggressive ions can destroy the layer locally and Aluminium substrate lead to local corrosion attack (“pitting”). A typical case for this reaction is the contact between aluminium and chloride ions, EUROPEAN ALUMINIUM ASSOCIATION ALUMINIUM IN COMMERCIAL VEHICLES CHAPTER XI 147
Galvanic corrosion
2.2. Types of aluminium corrosion in commercial vehicles
Although highly resistant to cor - 2.2.1. Galvanic corrosion bination with other metals under rosion through its natural oxide the presence of an electrolyte film, the following types of corro - Galvanic or bimetallic corrosion (such as water). In an electro - sion can occur in commercial can occur when two different chemical reaction, the aluminium vehicle construction or operation: metals (or electroconductive is working as an anode and is • Galvanic corrosion non-metallic materials) are in dissolving, while the other metal • Crevice corrosion contact with each other in the retains its integrity. • Pitting corrosion presence of an electrolyte. The • Filiform corrosion reason for this type of corrosion In this case, the aluminium ions is the difference in the electro - react with the oxygen of the
chemical potential of the two water to alumina (Al 2O3), which metals. Aluminium is a very elec - builds a white layer on the alu - tronegative metal and therefore minium surface. special attention has to be paid when aluminium is used in com - 148 EUROPEAN ALUMINIUM ASSOCIATION ALUMINIUM IN COMMERCIAL VEHICLES CHAPTER XI
There are 3 main prerequisites for FIGURE XI.2 galvanic corrosion: PRINCIPLE OF A GALVANIC CELL BUILT WITH ALUMINIUM AS ANODE • 2 different metals with differ - ent electrochemical potential • presence of an electrolyte • contact between the 2 metals e- ® ® The electrolyte enables the flow Electron Flow of ions between the 2 metals. Anode Cathode This can happen if the metals are (Aluminium) (e.g. copper) wetted by the electrolyte (e.g. water containing salt) or emerged in the electrolyte. In commercial vehicles, this type of corrosion can occur where steel and aluminium parts are bolted, Electrolyte riveted or screwed together and where rainwater or road splash 3+ - 6H+ +6e- " 3H # water can come in contact with 2Al " 2Al +6e 2 the metal parts. (Figure XI.2)
To avoid direct contact between the 2 metals and to prevent FIGURE XI.3 entrapment of water, it is neces - sary to work with insulating PREVENTION OF GALVANIC CORROSION material (such as neoprene or other elastomers) between the
metals and to use sealing com - pounds to close constructive ‰ Aluminium gaps. (Figure XI.3) ‰
Sleeve and ‰ Gasket ( PVC, insulating elastomer) washers ‰ ‰
Bolt ‰ Other metal (Steel…) EUROPEAN ALUMINIUM ASSOCIATION ALUMINIUM IN COMMERCIAL VEHICLES CHAPTER XI 149
FIGURE XI.4 CREVICES AND HOW TO PREVENT THEM
Tight fastening of bolts and rivets necessary Sealing of access 2.2.2. Crevice corrosion to crevice
‰ Crevice corrosion occurs in small ‰ Possible constructive recesses. In a crevice ‰ crevice there will be the possibility for accumulation of moisture Sealing of the because of capillary forces and crevice itself deposits of aggressive media. Therefore, especially in the road water splash zone, constructive FIGURE XI.5 gaps should always be closed as PITTING CORROSION far as possible, as the penetrat- ing water might contain aggres- sive ions (e.g. from road salts).
The corrosion rate of crevice cor- Alumina rosion is normally very low due to the corrosion product – alumina Alumina – being stable and building a seal- Corrosion ing of the crevice. (Figure XI.4) Attack ‰ CI-
CI-
‰ ‰ 2.2.3. Pitting corrosion ‰ CI-
Pitting corrosion is the most com- ‰ ‰ mon corrosion form seen on alu- minium, characterised by the development of small local pits in which have been ground, weld corrosion speed. (Figure XI.5) the surface. The diameter and the discontinuities etc.). The pits are depth of the pits varies and formed with a rapid increase in This slowdown in the rate of pit- depends on different parameters depth after initiation followed by ting corrosion explains the fact related to the aluminium itself a slower growth. This is due to that aluminium equipment can be (type of alloy, rate of cold working, the corrosion product - alumina – used for decades in certain envi- heat treatments) or to its environ- that is not soluble in water and ronments (country air, sea air, sea ment (presence of aggressive ions). therefore adheres to the surface water) without any protection. Pitting corrosion occurs on sites of the metal inside the pits. The where the natural oxide film is alumina then obstructs the direct In other words, pitting corrosion damaged or imperfect due to contact between the aluminium is quite normal and normaly diverse reasons like manufactur- surface and the corrosive medi- does not impact the durability of ing related circumstances (areas um and by this slows down the vehicles. 150 EUROPEAN ALUMINIUM ASSOCIATION ALUMINIUM IN COMMERCIAL VEHICLES CHAPTER XI
FIGURE XI.7 2.2.4. Constructive measures to prevent corrosion
Unsuitable solutions Some general rules shall be applied to prevent corrosion (in most cases to prevent any kind of water trap or areas where con- densation can occur): • Constructive gaps should be avoided or, if not possible, should Better solutions be sealed. (Figure XI.6) Run of FIGURE XI.6 Run of
Watertight seal
‰
• Water traps should be avoid- have a worm-like appearance ed. Assemblies should be con- and are readily visible. Filiform structed with the open side corrosion does not attack the downwards. (Figure XI.7) metal surface, but affects the • Weld discontinuities should, surface appearance. also with regard to other issues The mode of corrosion is quite like stress, fatigue etc., be strictly similar to pitting with the front of avoided. (Figure XI.8) the attack being supported by • Materials having different elec- moisture which penetrates the trochemical potential have to be surface layer and leads to oxygen separated from each other by concentrated areas and by thus coatings or insulating materials. acting as an anode. Filiform corro- FIGURE XI.8 sion is mainly an aesthetic effect, 2.2.5. Filiform corrosion but could lead in certain construc- Weld discontinuities tion parts to delaminating of the Filiform corrosion (also known as surface layer system.
‰ under-film corrosion) occurs To prevent this type of corrosion it ‰ under paint or enamel layers. It is of vital importance to follow the depends mostly on environmen- instructions of the paint supplier, tal conditions and the quality of especially with regard to a proper the surface treatment prior to surface treatment under the use painting. The corrosion filaments of a suitable primer system. EUROPEAN ALUMINIUM ASSOCIATION ALUMINIUM IN COMMERCIAL VEHICLES CHAPTER XI 151
Filiform corrosion coming from default in paint
2.2.6. 5000 series alloys and elevated temperatures • Manufacturing processes like As a general guideline, the use of forming and thermal joining alloys with a maximum of 3% of When held for long periods at (welding) might reduce resistance magnesium is strongly recom - elevated temperatures (between of final product to sensitization. mended where exposure for long 65°C and 200°C), aluminium- • The thermal load (i.e. temper - periods to temperatures in excess magnesium alloys containing ature multiplied by time of expo - of about 75°C occurs. When the more than 3% of magnesium sure) is more important than the use of 5000 alloys with higher undergo metallurgical changes temperature alone. For example, Mg content is desired, consulta - that can lead to intergranular if 65°C is often given as a limit in tion with the material producer is corrosion if the two conditions catalogues or manuals, it takes necessary and their applicability below are both satisfied: two years to sensitize a 5086 must be evaluated in detail, tak - • Precipitation of a continuous alloy at that temperature, while ing into account the thermal bead of Al 8Mg 5 intermetallic at 100°C, several months are exposure of the part during its compounds occurs along the necessary. The fastest sensitiza - total lifetime. grain boundaries (sensitization). tions are generally observed
These Al 8Mg 5 precipitations are between 130°C and 150°C. 2.2.7. Other forms of corrosion anodic to the bulk material. • Presence of an aggressive But even if a material is sensi - Other forms of corrosion do exist, medium, e.g. a saline solution on tized, corrosion will only happen but the alloys and tempers most the bare surface of the material. in aggressive environments, i.e. currently used in commercial when a corrosive electrolyte gets vehicles are not prone to these This phenomenon has been studied in contact with the metal surface. types of corrosion. many times with a view to gauging Experience has confirmed this. the influence of the following There are road tankers for heavy parameters for sensitization: fuel oil, which have seen 20 years • The magnesium content and the and more of service, running 8 to 2.3. Further references production process largely deter - 10 hours a day, which is at least mine the kinetics of sensitization of 50,000 hours of cumulative • Corrosion of aluminium , 5000 series material. Proper routes operation at 65-70°C. C. Vargel, ed. Elsevier to minimize susceptibility are well • www.corrosion-aluminium.com established at suppliers. EEUROPEAN ALUMINIUM ASSOCIATION CHAPTER X II
CLEANING OF ALUMINIUM COMMERCIAL VEHICLES
1. INTRODUCTION ...... 154 2. THE NATURE OF STAINS ...... 154 3. THE CHOICE OF DETERGENT ...... 155 4. APPLICATION OF THE DETERGENT ...... 155 154 EUROPEAN ALUMINIUM ASSOCIATION ALUMINIUM IN COMMERCIAL VEHICLES CHAPTER XII
Commercial vehicle cleaning station (Interservice Arras)
1. Introduction
Regular cleaning of a commercial In case of tank trailers, there are In general, cleaning of an alu - vehicle is a prerequisite to ensure often strict legal regulations con - minium vehicle is not different a long lifetime. Any kind of dirt is cerning the transport of food - from cleaning any other vehicle. removed, the optical attractive - stuff or there are other regula - It can be done on automatic ness is kept and critical parts like tions for strict cleaning when dif - washing lines as well as manual - wheels, axles, brakes and ferent chemicals are transported ly with the use of high pressure hydraulic systems can be better which might interfere with the spray guns, brushes and cloths. optically controlled. Corrosion is goods transported before. In prevented and damages due to some cases, aluminium cannot mechanical friction between be used as a construction materi - moving parts can be avoided. al due to the cleaning instruc - tions, which specify the use of strong aciduous or alkaline chemicals. EUROPEAN ALUMINIUM ASSOCIATION ALUMINIUM IN COMMERCIAL VEHICLES CHAPTER XII 155
2. The nature • Allow an efficient removal of • Physical aggressive dirt Stains are removed by decreasing of stains • Create a bright visual appear - the surface tension. Therefore deter - ance of the surface gents contain wetting elements Stains on commercial vehicles • Build up a protective film on • Mechanical may have the following origins: top of the paint Stains are removed by spraying • Road caused: dirt, salts, mud, • Be in compliance with specific with pressurised detergent or by water splash, tyre wear regulations abrasion when using brushes • Fuel caused: diesel exhaust, soot • Be biologically degradable • Temperature • Load caused: cement, asphalt, • Be harmless to the user Higher temperatures, or even chalk, residues of agricultural water steam, increase the clean - products etc. Detergents are a complex mix - ing effect by increasing the speed • Environmentally caused: effects ture of up to 20 ingredients to of the chemical reaction between of air pollution, dust enable diverse functions at the the detergent and the stain. same time: degreasing, slight All these elements, in connection etching, washing, conserving etc. Spraying should be done from with humidity, can lead to local bottom to top of the vehicle to corrosion and fading or destruc - prevent streaking. The residence tion of the paint layer. 4. Application time should be sufficient to dis - In this respect, residues of previ - solve the stains. The detergent ously transported goods prior to of the detergent should not dry on the vehicle sur - a new load might also be seen as face and washing should be fol - contamination and require inten - The cleaning of a vehicle should lowed by intensive rinsing with sive cleaning. not take place in direct sunlight. de-ionized water. Each detergent should be tested on a raw aluminium surface prior 3. The choice to first use. of detergent The detergent can be used either in automatic washing lines or can The detergent used for cleaning an be applied manually with the use aluminium vehicle must be com - of high pressure spray guns, patible with aluminium, means it brushes, cloths etc. Its main must not be too aggressive. cleaning effects are: • Chemical In general, a detergent has to: Some elements of the detergent • Have a strong effect on all dissolve the dirt or mineral salts kinds of dirt without attacking the surface EEUROPEAN ALUMINIUM ASSOCIATION CHAPTER XI II
REPAIR OF ALUMINIUM COMMERCIAL VEHICLES
1. FOREWORD ...... 158 2. EXECUTION OF REPAIR ...... 159 3. REPAIR OF ALUMINIUM CHASSIS ...... 159 4. MIG AND TIG WELD REPAIRS ...... 160 4.1. Choice of alloy ...... 160 4.2. Preparations ...... 160 4.3. Welding ...... 161 158 EUROPEAN ALUMINIUM ASSOCIATION ALUMINIUM IN COMMERCIAL VEHICLES CHAPTER XIII
Inside view of a repaired aluminium tank (Feldbinder)
1. Foreword
Repair of commercial vehicles never just be “over-welded”. European Pressure Vessel should be done with the same This method does not reflect a Regulation 97/23/EU. This care as new construction. In reasonable way of repair. Any requires additional testing general, all rules, materials and parts, which have been cut out methods for repairs and supervi - methods used for new construc - due to damages, must always be sion by certified supervision tion should also be applied for replaced with the same type of bodies (like TÜV). repair causes. alloy as originally used. This has Repair should therefore be car - Repair is a case-to-case decision, to be applied to ensure a safe ried out by the manufacturer of whether small damaged parts and constant stress deviation the original vehicle or in certi - can be repaired without dis- across the vehicle and to prevent fied repair workshops: qualified assembling the structure or a weakening of the construction. welders, working methods whether damaged components It has to be taken into consider - according to state-of-the-art (plates, extrusions) must be cut ation, that especially tankers or technologies, suitable work out and replaced completely. silo trailers are regarded as pres - organisation, etc. are necessary. In any case, damages should surized vessels under the EUROPEAN ALUMINIUM ASSOCIATION ALUMINIUM IN COMMERCIAL VEHICLES CHAPTER XIII 159
Outside view of a repaired aluminium tank (Feldbinder)
2. Execution of repair 3. Repair of aluminium A sophisticated repair of an alu - the repair zone minium commercial vehicle • Fixing of the replacement part chassis should be done according to the to the vehicle; if necessary addi - following procedures: tional forming to the vehicle The case of aluminium chassis • Identification of the damage contour to prevent too much deserves a particular attention, - How much metal has been stress during welding as a non-professional repair may destructed? • Joining of the replacement lead to a deterioration of both - Any further damages which part to the vehicle structure by the static capacity and fatigue could not be seen during first suitable welding methods. strength. inspection? • Visual control of the weld quality • Cut out of damaged compo - • If necessary or mandatory To avoid this kind of problems, nents (pressure vessels), then non- please read Chapter VI, section • Identification of originally destructive testing (ultrasonic, x- 8, dedicated to fatigue. used material specification ray) of the weld seam • Order of replacement material • Grinding or flattening of the Beginning with fatigue theory, according to detected specification weld seam that chapter also illustrates how • Order of suitable welding • Repair of the coating good practices for perforating filler wire (according to norms or • Final control; it might be and welding can secure long specific regulations) required to let all steps of repair lifespan to vehicle. • Pre-cut of replacement part be checked by a supervisory under consideration of the ther - organisation. mal shrinking during welding • Pre-form replacement materi - al if necessary • Removal of original coating in 160 EUROPEAN ALUMINIUM ASSOCIATION ALUMINIUM IN COMMERCIAL VEHICLES CHAPTER XIII
Welding of silo body (Feldbinder)
4. MIG and TIG weld repairs
A road vehicle can sustain dam - cleaning, degassing, with 4.2. Preparations age and will need to be repaired. explosimeter checks, dust Repairing a commercial vehicle removal etc. as necessary. This is the most important phase made from aluminium alloys is as it will determine the quality no more difficult than repairing a 4.1. Choice of alloy and strength of the repair: steel vehicle, but should be done • for cutting out, preference according to a strict procedure in The alloy of the semi-finished should be given to the plasma a properly equipped workshop products used for the repair torch or a carbide cutting wheel by skilled operatives under the work must be the same as (or rather than a high speed steel supervision of an official body compatible with) the original (HSS) wheel or abrasive wheels and/or classification society if the alloys as indicated in the manu - that might introduce inclusions vehicle's duty calls for this. facturer's manual. into the weld seam, • very carefully grind the area to No repair work should com - be welded to remove all traces of mence without knowing the type paint and various residues, of freight (liquid, powder etc.) • carefully degrease with suit - which the vehicle has been used able agent to carry and before taking the appropriate safety precautions: EUROPEAN ALUMINIUM ASSOCIATION ALUMINIUM IN COMMERCIAL VEHICLES CHAPTER XIII 161
4.3. Welding • pay particular attention to the Compact TIG welding machines weld direction. The purpose of weighing less than 20 kg are The rules for repairing are basi - this is to limit deformation and now available on the market cally as described in Chapter VII minimize the risk of hot cracking. capable of delivering a welding for forming and as described in Volume contraction in the weld current of around 160 A. These this chapter for welding. When bead is approximately 6 % machines are easy to carry and carrying out repairs it is essential between the fluid state and the are ideal for small, localized to: solid state at ambient tempera - repairs. • hold the components, e.g. ture. It is this phenomenon For minor repairs such as a tank, chassis etc., securely in which causes the risk of cracking, breach in the skin of a tank, the their relative positions. Clamps • change the path of welds in patch must be perfectly matched should be adjusted to allow order to avoid going back over an to the shape of the breach but expansion however, as too much original weld (Figure XIII.1), should be slightly enlarged by restriction could aggravate the • perform any necessary tests, e.g. hammering to compensate for adverse effects of contraction. It radiography, dye penetration etc., contraction following welding. is also useful to mark areas of the • chose the right welding Without this precaution the structure likely to suffer maxi - process (TIG or MIG). TIG weld - residual stress might well cause mum stress, referring to the ing is preferable for minor repairs systematic cracking. This phe - manufacturer's design calcula - where access from behind is not nomenon is more pronounced tions if these are available, possible as it is easier to use and the smaller the patch. • support built-up parts to con - allows better penetration control trol clearances, than MIG welding.
FIGURE XIII.1 WELD REPAIR
New weld ‰ ACKNOWLEDGEMENTS Main writers: Jürg Zehnder, Reinhard Pritzlaff, Steinar Lundberg, Bernard Gilmont.
Project team: Asmund Broli, Roald Pedersen, Benoît Lancrenon, Michele Triboldi, Dietrich Wieser, Ralf Balduck, Klaus Vieregge.
Sponsoring companies: Alcan Engineered Products, Alcoa Europe, Aleris Europe, AMAG, Elval, Hydro Aluminium, Metra, Novelis, Sapa
The project team is particularly grateful to Alcan Engineered Products for having authorized to use some texts, tables and figures coming from the following publications:
• Aluminium in Commercial Vehicles, Pechiney-Rhenalu
• Aluminium and the Sea, Alcan Aerospace, Transportation and Industry
PHOTO AND TABLE CREDITS
Page Company or brand Photographer or source Page Company or brand Photographer or source 1 Benalu Benalu 48 Menci Bernard Gilmont 4 Menci EAA library 48 Alcoa Europe Alcoa Europe 6, 8 Airbus Airbus 54 Brabant Alucast Bernard Gilmont 9 Hydro Aluminium Hydro Aluminium 75 Alcoa Europe Alcoa Europe 9 Babcock Babcock 76, 81 Benalu Benalu 10 Alstom, SNCF Alstom, SNCF 82 Aluminium-Verlag Aluminium-Verlag 11 Mercedes 86 Schrader Schrader 11 Hydro Aluminium Hydro Aluminium 87 Stas Stas 12 Aluminium-Verlag Aluminium-Verlag 88 Schmitz Schmitz 12 Alusuisse Alcan Engineered Products 89 Menci Menci 12 Trailor Trailor 90, 105 König Ursula Berndsen 16 Benalu Benalu 95 SAG Alutech SAG Alutech 17 Tang Fahrzeugbau GmbH Tang Fahrzeugbau GmbH 97, 98, 99 Benalu Bernard Gilmont 19 All American Marine All American Marine 100 Sapa Sapa 20, 36 Stas Stas, IRTE 108 Stas Stas 21 Alcan, Alcoa, Brabant Alucast Alcan, Alcoa, Bernard Gilmont 110 SAG Alutech SAG Alutech 23 Alcan Engineered Products Alcan Engineered Products 112 Menci Bernard Gilmont 24 Galloo Recycling Bernard Gilmont 114 Sachsenring Ursula Berndsen 25 ATM, PVC Transports Patrick Van Crombrugghe 26 Menci Bernard Gilmont 119 Alcan Engineered Products Alcan Engineered Products 26 Alcoa Wheel Products Europe Alcoa Wheel Products Europe 120 Sapa Sapa 27 Benalu Benalu 121 Hydro Aluminium Hydro Aluminium 28 Pezzaioli Pezzaioli 122 Schmitz Schmitz 30 Alcoa Europe Alcoa Europe 128, 132 Alcan Engineered Products Bernard Gilmont 31 Stas Stas 135 Alcan Engineered Products Alcan Rhenalu Issoire 32 Benalu Benalu 138 Trailor Trailor 33 Leciñena Leciñena 140 LAG LAG 34 Menci Menci 140 Benalu Benalu 37 Schrader Schrader 142 LAG LAG 40, 43 Alcan Engineered Products Alcan Engineered Products 152, 155 Interservice, Arras Christian Vargel 44, 45, 47 Various aluminium plants EAA library 156, 158, 159, 162 Feldbinder Feldbinder
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