Lightweight Door Ring Solution in Car Body Development
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Research Article – IJAAT – 2017 – 22 International Journal of Advances on Automotive and Technology http://dx.doi.org/10.15659/ijaat.17.07.529 Promech Corp. Press, Istanbul, Turkey Manuscript Received October 14, 2016; Accepted May 15, 2017. Vol.1, No. 3, pp. 131-136, July, 2017 This paper was recommended for publication in revised form by Co-Editor Yasin Karagoz LIGHTWEIGHT DOOR RING SOLUTION IN CAR BODY DEVELOPMENT *Evren Altınok Hakan Kayserili TOFAŞ, Turkish Automotive Company TOFAŞ, Turkish Automotive Company R&D Center R&D Center Bursa, Turkey Bursa, Turkey Ahmet Mert Serkan A. Altınel TOFAŞ, Turkish Automotive TOFAŞ, Turkish Automotive Company R&D Center Company R&D Center Bursa, Turkey Bursa, Turkey Keywords: Car Door Ring, Hot Stamping, Boron Alloyed Steel, A-Pillar, B-Pillar, Rocker, Body Light Weight, Frontal Crash, Lateral Crash Phone: +90 224 261 03 50, Fax: +90 224 261 0408 E-mail address: [email protected] ABSTRACT manufacturers in order to reduce CO2 emission that causes Lightweighting has become a target for car manufacturers greenhouse effect, the main reason for climate change. To in order to reduce CO2 emission that causes greenhouse effect, lessen vehicle load is aimed to increase fuel efficiency, provide the main reason for climate change. 40% of average weight occupant protection and environmental factors. distribution of a vehicle arises from the parts that belong to the The statistics show that fuel consumption may decrease 6- body. With a door ring design developed differently from 8% if the lightweight effect of full vehicle reaches 10% [1]. As standard methods, around 3 kg/vehicle weight reduction was the automotive structure possess about 40% weight of full achieved. Rocker which currently a couple of part was vehicle, the weight reduction in body structure is one key way converted to single part and the number of operation applied in to achieve fuel efficiency, harmful emissions reduction and raw production line was reduced. By this means the structure was material saving [2]. Moreover, crashworthiness is the other made more rigid. B-Pillar was designed as a lightweight part important issue that focuses on occupant protection to reduce suitable for the system. The weight reduction was obtained by the number of fatal injuries. The body is the suitable place to optimizing the parts without compromising vehicle safety reinforce structures to reduce effect of crashes. Hence, the objectives and by changing the loading method for welding ability of the vehicle to absorb energy comes into prominence process. By supporting designs with virtual analysis design for body design. Using resisting materials in design, providing validation was conducted. structural rigidity are the basis studies to increase stability for accidents. Especially the door ring that absorb energy in lateral crash must be designed without compromising vehicle safety objectives. INTRODUCTION The door ring (in Fig.1) is designed with three crucial parts Environmental problems that are increasing day by day which are A-Pillar that supports the windshield, B-Pillar that canalize the most of industrial areas like automotive industry to play a key role providing strength to the midsection of the new researches. Lightweighting has become a target for car 131 vehicle and Rocker that is located along the sides of the vehicle between front and rear wheel. In this paper, a new door ring was designed by developing differently from standard methods for a stronger and lightweight body structure. As a result, around 3 kg per vehicle weight reduction was achieved and new door ring design was verified by supporting with numerical analysis. The new door ring design method was developed according to FCA (Fiat Chrysler Automobiles) product development FIG.2 – PRODUCT DEVELOPMENT PROCESS process (Fig.2). The relevant process consists of four main phases which are concept, definition, execution, industrialization. RESULTS AND DISCUSSION Design Optimization The design of the door ring that is known as a life cage of the vehicles in side impact and the loading method of the door ring was developed in order to be more competitive without compromising vehicle performance. Problem Description and Alternative Solution: The standard door ring design is shown in Fig. 3. As can be seen in the figure, the standard design includes three important parts which are A-Pillar, B-Pillar and Rocker. FIG.1 – A-PILLAR, B-PILLAR, ROCKER PANEL IN A CAR BODY DESIGN FIG.3 – STANDARD DESIGN The new design was started in execution phase that includes technical development and tooling development process. In main design activities of technical development Gas metal arc welding (GMAW) is supposed to be applied stage that are packaging controls, virtual validations, on the back side of the door ring in order to avoid visual manufacturing feasibility and process simulations were made by pollution in the standard design. In addition to that GMAW design team. In addition to that the mathematic models were must be applied because of the Rocker which consists of two created in the CAD release level. In tooling development stage, parts (Fig.4). The same GMAW application must be used on the mathematic models were released by project team and the joint of A-Pillar and B-Pillar. previous design activities which are in technical development stage were continued in this stage too. Finally, in industrialization phase that is the final stage of development process, process verification, durability, VLO (vehicle layout controls), plant manufacturing process readiness, design validation and pre serial production were conducted by project team. 132 Conference Paper The necessity of GMAW usage was eliminated as producing a new single Rocker part. Instead of that, spot welding is adequate in order to join Rocker and B-Pillar before loading the door ring to the body. Hence, B-Pillar was optimized as removing unnecessary portions of part that is used for GMAW on B-Pillar (Fig. 6). FIG. 4– GMAW AREA ON THE DOOR RING FIG. 6 – SPOT WELDING AREA ON THE DOOR RING Each part of the door ring is loaded to the body separately. Therefore extra welding applications are required on joint The number of operation applied in production line was regions. Production process is extended due to many number of reduced whereby the new door ring is designed. Around 3 kg operation. The new design process was launched based on these per vehicle weight reduction was achieved due to form A- and problems eventually. The new door ring design can be seen in B-Pillar with hot stamping and due to remove unnecessary Fig. 5. portion of parts. The effect of hot stamping on weight reduction is an expected result. Hot stamping offers considerable potential for minimizing component weight by reducing sheet thickness and the number of components needed. Hot stamping technology can be used for A- and B-Pillar reinforcement roof rails, side wall members and beams for crash management structures [3]. Tolerancing and Loading to Body: In the standard design, single part tolerances are used so that each part of the door ring are loaded to the body separately. The parts cannot be loaded to the body that will be experienced in case of unsuitability of the new door ring tolerances. Loading simulations were made in order to determine proper tolerances. The tolerance studies are applied on the new door ring design can be seen in Fig. 7. Moreover, the tolerance values were validated as making loading simulations. FIG.5 – NEW DOOR RING DESIGN 133 FIG.7 – TOLERANCE STUDIES OF THE NEW DOOR RING DESIGN FIG.8 – SIDE IMPACT ANALYSIS IMAGE FOR EURO NCAP Optimization Process The goal of this study is to obtain more rigid and stronger The data which is taken after a car that is moved at 50km/h door ring design by reducing the reinforcement parts and is crashed to a stable testing vehicle were compared with without increasing overall weight. It is more important to know performance criteria. The deformation effect on B-Pillar that is the safety performance of the vehicle which parts are affected observed in side impact simulation is in Fig. 9. The data is by lateral crash. Structural and mechanical characteristic of obtained from the simulations results were determined in door ring is crucial for the safety performance of the vehicle. accordance with the criteria by the safety center of FIAT. The door ring should have good energy absorption characteristic and high mechanical properties in order to be protected safety door ring. Generally these characteristics are obtained by using functionally graded strength (FGS). FGS structures are found by optimizing all of the crashworthiness and its deviation by the time of the crash impact (peak forces, max-min acceleration of the deformation, max displacement of the related zone in safety cage etc.) [4]. In optimization process, stampability analysis, side impact simulations, NVH tests, chemical composition and micro structure analysis were made on the new door ring design and optimal door ring design solution was obtained successfully. Side Impact Simulations (Lateral Crash Tests): Research has shown that side impacts are relatively uncommon, but they represent a disproportionately high level of fatalities FIG.9 – SIDE IMPACT SIMULATION RESULTS FOR [5]. Euro NCAP- European New Car Assessment Programme EURO NCAP added a pole test to demonstrate passenger safety. Euro NCAP’s pole test has seen several updates, including the test dummy, NVH Tests: Recently, various structural and mechanism performance criteria and scoring [6]. The image of side impact analysis techniques have been applied to vehicle development analysis according to Euro NCAP standards can be seen in contributing to simplification of prototyping and reduction of Fig.8. labour time required for vehicle development [7]. Thus, the finite element model of the door ring that is designed for change of concept was created for NHV test that is one of these analysis techniques (Fig.10).