Analysis of stress simulation : a case study for the evaluation of a homologation test procedure for the design of rear underrun protection

Abstract

Accidents between a passenger vehicle and a heavy weight vehicle (HWV) stand out as one of the most dangerous ones. These often result in fatal injuries or the death of the passengers, due to higher dimension and weight differences. One possible accident situation is the underrunning of a smaller vehicle with the rear end of a heavy truck. To avoid these types of accidents important parameters have to be considered when designing the frame of the vehicles or the implementation of safety equipment. Front, side and rear underrun protections (RUP) are all examples of safety equipment that avoid the slippage of smaller vehicles beneath heavy truck frames. In Europe, the legal requirements of these are all fixed in regulations imposed by the United Nations Economic Commission of Europe (UNECE). Within the framework of this work, we will specifically analyse the regulation number R58 (revision 2), which contains all technical specifications for RUPs and all steps to a numerical test. Using a Finite Element (FE) analysis tool like ANSYS Mechanical, we will develop a computer model from scratch to simulate stress distribution of a RUP. The model is to be based on the test procedures specified in the R58 and the design of the RUP will be provided by the company “Laboratorio T´ecnico de Reformas S.A” (LTR). The main objective of this work is to provide the company with a simulative software which calculates accurate results, comparable to a real physical test. We will also check the strength resistance of the provided RUPs design and if this is capable of withstanding regulative loads. Our results concluded that this was not the case: the utilized screws, which served as union components for the RUP, fail before reaching maximum load. However, after some physical tests performed by the manufacturer, their RUP was also not able to withstand applied forces. The computational and physical results are subsequently similar. In order to verify the accuracy of the simulative program, further ten designs were tested with the same conditions as the first one. After observing promising results, the Entidad Nacional de Acreditaci´on (ENAC) approved the software for further usage and so the homologation procedure can be started.