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Session 1

Using CAE to evalute a structural foam design for increasing roof strength
In recent years, there has been increased discussion of the strength of vehicle roofs in rollover crashes. NHTSA recently revised the federal roof strength requirement and the IIHS has published an even more stringent roof strength goal. While working to increase roof strength, automakers are also working to reduce vehicle mass for improved fuel economy and other benefits. Developing technology to achieve both of these goals is challenging. This paper investigates the use of CAE to evaluate the addition of structural foam to an existing design to maintain or increase roof strength. A concept solution that combines nylon and structural foam material was developed and analyzed using an explicit finite element model and later tested on a body-in-white to evaluate the CAE predictions. The main evaluation method was the FMVSS 216 test procedure. Through CAE analysis and actual testing, the modifications were found to have increased roof strength. A performance target was set and a conceptual steel-only assembly was created in CAE to meet this target. The foam/steel assembly met the performance target but at a reduced weight compared to the steel-only assembly. These analyses demonstrated that CAE is useful for predicting the performance of foam/steel assemblies and that foam/steel assemblies can yield greater strength with lower mass than a steel-only assembly. Questions regarding field performance and the feasibility of mass-production must still be addressed.
Finite element dynamic simulation of whole rallying car structure: Towards better understanding of structural dynamics during side impacts
Side impact accidents against a tree or pole remain the most dangerous accident scenarios in rally cars. Statistical data shows that 52% of the fatalities between 2004 and 2009 concern crashes against a rigid pole by the track sides, whilst among those more than 60% were side impacts. Despite the present scientific efforts, rallying cars side impacts are still among the least understood primarily due to limited space between the occupant and door sill, evolving safety regulations and vehicle dynamics. In this study, finite element dynamic characteristics of the whole car were studied. The finite element model consisted of the whole car structure and 241 parts including the engines, tyres and the suspension members with 4 different element types and 7 material models. All structural parts were modelled as low-carbon steel with the piecewise-linear-plasticity material model (mat 24). The tyres were modelled with the Blatz-Ko rubber material (mat 07) whilst also rigid and other materials (mat 020, 01, 09, S01 and S02) were used to represent different parts of the model, as the suspension members, suspension links and the engine. A rollcage and two racing seats were modelled with four-node shell elements and the use of piecewise-linear-plasticity and composite-damage materials respectively. A semi-cylindrical pole of 200mm diameter was also designed and modelled as a rigid body. The model was used to first investigate the dynamics of the crash, and later run a wide range of simulations and parametric studies in the cage, the car’s floor and the seats. The important findings from the study are presented, conclusions drawn and scope for further development outlined.
Crashworthiness of an Electric Prototype Vehicle Series
The Shell Eco-marathon (SEM) is a challenge for student teams to develop energy-efficient vehicles and demonstrate the fuel efficiency of their prototypes. In Europe, this takes place at the Lausitz Ring in Germany. Since 2009, the Schluckspecht team has taken part in the Urban Concept category of the SEM. The specification of the vehicles which start in the Urban Concept Group requires resemblance to roadworthy cars. In the last quarter of 2009, the University of Applied Sciences Offenburg (FHO) where the team is located and the Fraunhofer Institute for High-Speed Dynamics, Ernst-Mach-Institut, EMI, Freiburg, set up a cooperation to improve safety of the prototype Schluckspecht City. Fraunhofer EMI deals with physical-technical aspects of high-speed, mechanical, and fluid-dynamic processes. This includes experimental and numerical analyses of crash, impact and penetration processes in a broad range of speeds from 10 m/s to 10,000 m/s, the response of structures to shock loads, dynamic material response and vehicle safety.
Roof Crush Resistance and Rollover Strength of a Paratransit Bus
Paratransit buses constitute a special group of vehicles in the US due to their smaller size, two-step assembly process, and their use for complementary services to the regular scheduled transit routes. Due to their uniqueness these buses lack national crashworthiness standards specifically dedicated to the paratransit fleet. Several states in the US adopted the quasi-static symmetric roof loading procedure according to the standard FMVSS 220 for testing the integrity of the paratransit buses. However, as many researchers point out, the dynamic rollover test according to UN-ECE Regulation 66 (ECE-R66), which was approved by more than forty countries in the world, (excluding the US), may provide more realistic assessment of the bus strength.