Case Study: Leyland Trucks, Ltd

MSC Software | CASE STUDY Case Study: Leyland Trucks, Ltd. Building Better Trucks - Simulation at Leyland Trucks Expands Analysis, Cuts Design Time, and Reduces Physical Prototypes Overview Leyland Trucks Ltd., a wholly owned subsidiary of PACCAR Inc., has become the company’s established center for light- and medium-size truck design, development, and manufacture, producing trucks from six to 44 tonnes for each of PACCAR’s established international brands – Kenworth, Peterbilt, DAF, and Foden. Leyland has been using MSC Software solutions for quite some time, including MSC Nastran for 10 years and Adams since 1997. Like many companies, they started using simulation software for discrete components, then assemblies, and ultimately for the dynamic simulation of assemblies. According to Dr. Jim Henderson, senior engineer, dynamics, at Leyland Trucks, “Technology has reached a point now where it would be impossible to do the variety of load case checks and dynamic simulations any other way than using advanced simulation software.” “My job is about solving problems in the real world. Adams is powerful and flexible enough to let me model exactly what I need.” James Patterson, PhD. Principal Vehical Systems Engineer Keeping Up with Design Changes speed, tractor alignment, and trailer height (legs can sink into loose ground) have a The basic truck ladder chassis is a Key Highlights: critical impact on the operation. Being able to relatively simple structure. Because of simulate the whole process provides accurate the need to provide a variety of different load cases for improving traditional lead-up body configurations, it is unlikely that ramp designs by finite element techniques. Product: Adams trucks will ever move to the more unitary, integrated construction commonly used for Industry: Automotive cars. Consequently, the essential design Simulating Difficult Manoeuvers configuration of the truck has been very Tilt table simulations improve safety when Benefits: similar since the 1900s. But as design operating tipper-bodied vehicles on sloping • Find critical operating technology has improved, the details of the or uneven surfaces. For instance, simulation conditions by performing truck have evolved almost beyond recognition. can run through a situation in which the dynamic simulations For instance, new materials have been full payload is inside the vehicle body, the • Replace the extremely introduced in recent years, leading to global body is elevated to its full extent, and the initiatives to reduce weight through the use vehicle is tilted incrementally until its first expensive and time- of these advanced high-strength steels. wheel lifts. It is extremely expensive and consuming physical tests Other design details are changing – trucks time-consuming to perform this test physically with fast and accurate are now using disc brakes rather than because it requires both a real vehicle simulation drums – and Leyland engineers must balance and the use of a tilt table. By contrast, the • Reduce the design cycle from incorporating these details while improving simulation is quick, accurate, and allows rapid quality and still keeping costs under control. 6 years to 4 years comparison of alternative configurations. Before adopting Adams, Leyland engineers From analysis of a lane-change manoeuvre, validated their designs using standard Leyland Trucks dynamics engineers static load cases and traditional finite discovered that on a recent vehicle, a element analysis, which would approximate Each truck is significantly different from military concept truck, rollover could only some of the situations they now simulate the previous one, so there are very few be achieved using an unrealistically high dynamically. “For instance, in cornering opportunities to modify and reuse previous payload centre of gravity and extreme situations, we would use a set of static loads physical prototypes. One of the critical speed in excess of 60 mph. Because of to simulate cornering at specific ‘G’ loads or areas for trucks is the cab. Because of the the potential danger, this is not a test that accelerations,” says Henderson. “However, greater design sophistication demanded by would ever be carried out physically, so in those days engineering judgement played truck users, cab design and development Leyland’s engineers appreciate being able a much greater part in trying to identify the is becoming prohibitively expensive. This to determine the ultimate performance worst cases. Now that we have the ability to often leads to collaborative ventures simulate a variety of different manoeuvres characteristics of the vehicles they design between several manufacturers. dynamically, a fuller set of load cases can without having to take physical risks. Ride comfort is important for the driver and be simulated, so we have a better chance of Detailed procedures such as cab tilt that for delicate payloads such as computers. finding the less obvious but critical conditions.” could not be properly analysed before can With Adams, Leyland engineers can A full Adams truck model contains a flexible now be investigated with Adams simulations. simulate a variety of ride conditions body and chassis, springs, roll bars, axles, The virtual cab is lifted by a hydraulic ram on highways, secondary roads, pavé cab and engine suspension, the steering until the centre of gravity passes over its pivot surfaces (cobblestones) and also discrete mechanism, and any frequencydependent point, at which time the cab falls forward surface events such as potholes and rubber mounts. Extra detail, such as brakes, and the ram cylinder acts like a damper to speed bumps. Truck-specific factors propeller shafts, and out-of-balance engine slow and control the motion. The simulations that affect ride include cab suspension, forces can be included on an ‘as needed’ help to determine the ram forcerequirements, chassis flexibility, and payload, all of basis. Simulation also allows several identify potential panel interference, and which can be easily varied with Adams. aspects of the operation of crane-bodied ensure that locks locate correctly. Part of improving the ride of the vehicle vehicles to be better understood, such Typical vehicle handling analyses include involves softening the cab suspension. as vehicle stability on slopes and uneven steady-state cornering, lane changing, ‘J’ This results in a compliant ride, which surfaces, the need for stabilising legs, and turns, and straight-line braking. Adams initially may not be to all truck drivers’ the effects of loading and unloading. simulation allows rapid assessment of the taste, but after about a month or so they When an articulated vehicle is coupling the effect of minute changes in suspension, are generally reluctant to go back to trailer to the tractor, variables such as tractor wheelbase, tyres, or payload position. more traditional suspension systems. Speeding the Design Cycle simulation so that the LF vehicle, as well as such that tried-and-tested techniques take being finished in two-thirds of the time of its precedence. Also, there are a limited number Simulation represents a significant benefit predecessor, is of considerably better quality.” of people in CAE and many more in design. in terms of final design quality, as well as considerable time savings. A recent project Leyland engineers manipulate and analyse “From my own point of view, I would like named LF was completed two years faster significant amounts of data. One of their to see more people in the company using than the previous equivalent one – in a approaches is to test the vehicle on the track simulation, not just the CAE department,” four-year design cycle rather than six. As and then ‘drive’ the Adams model with the says Henderson. “It would be useful if measured accelerations. Consequently, the more simulation model- building could always when technology is brought to input files are quite large. The correlation be done outside the CAE department. bear on design, although it is possible to between the track testing and the Adams There is still quite a lot of repetitive and identify benefits, it is unfair to suggest that simulations is good. “Again, it’s difficult to unnecessary duplication of geometry the comparison is truly ‘like for like’ as quantify the quality of the correlation,” said generation, manipulation, and cleaning. To there are inevitable process changes as Henderson. “In a time-variant simulation improve this, CAD and CAE tools need a consequence of the new technology. you’re never going to match the rise and to be linked more closely together.” “There are definitely areas where modelling fall of any particular acceleration exactly, A prototype vehicle early in the development and simulation have helped,” says Henderson, but when you look at the results in the cycle can prove to be very expensive. “It’s fair “particularly along the lines of reducing the frequency domain you can see that the to say that the use of simulation software has amount of time wasted building physical spikes line up fairly well at the same kinds of eliminated at least one of these prototypes,” prototypes with real parts. In the past we frequency. This is more important to us than explains Henderson. “So the software has would test things, find that they didn’t getting the level exactly right because it’s certainly paid for itself on the first project. work, and modify them using trial-and-error. dependent on so many different variables.” My job is about solving problems in the real This was considerably unstructured and Design teams at Leyland Trucks are still world. Adams is powerful and flexible enough very much the opposite of the ‘design of focused on getting drawings or parts to let me model exactly what I need, without experiments’ approach we take today, to vary out – the design process hasn’t reached getting too deep into software issues.” things in a structured fashion to identify where the required level of maturity where it can the trends lie. There are far more benefits be simulation-driven.

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