Gadekar 1 USE OF SECONDARY ENERGY ABSORBING STRUCTURES FOR IMPROVED SELF PROTECTION PERFORMANCE – EXPERIENCES DURING THE DEVELOPMENT OF A CHASSIS BASED VEHICLE Ganesh Gadekar Anil Kumar C Ashok G Joshi Makarand Takle Tata Technologies Ltd. (Deputed to Tata Motors Ltd.) India Paper Number 11-0283 ABSTRACT Secondary Energy Absorbing Structures (SEAS) have been discussed in literature in the context of improving geometric compatibility between larger vehicles like SUVs and cars. While compatibility related work is still in a research phase, development of the vehicles for self protection remains a priority. Vehicles also have to be designed to meet set targets against consumer group tests like Euro NCAP. A Secondary Energy Absorbing Structure on a Crossover kind of vehicle was evaluated to see the effect on self protection. Through the evaluation it was realized the SEAS can actually be optimized for improving the self protection and lead to reduced weight of the chassis frame. This concept was optimized to achieve weight savings in EuroNCAP load case. This paper presents the results of evaluations, analysis of the reasons why SEAS is expected to lead to weight savings in a typical offset frontal crash along with the optimization work carried out for achieving weight savings. INTRODUCTION In case of crash scenario for effective occupant protection, the structural crash behavior of the vehicle has to fulfill requirements like controlled energy absorption, structural integrity of the passenger compartment, limited intrusions in passenger cell and so on. These crash safety requirements resulted in significant weight addition on passenger car structures over last decade. Figure 1 show the weight spiral for European compact cars [1] where vehicle weight has significantly increased due to stringent legal/consumer group safety requirements and change in customer demands for growing vehicle size and comfort. However, this increased vehicle mass adversely impacted vehicle fuel efficiently and CO2 emissions due to increased energy consumption. Figure 1. Weight spiral for European compact cars (Source: “Aluminium in Cars” Report by European Aluminium Association) Today various light materials are being getting evaluated to reduce the weights of vehicle structures example include Aluminum, Magnesium Titanium etc. However the required weight reduction is not going to realized only through substitution of heavy materials by lighter ones unless it supported by appropriate new design and manufacturing design concepts. In this paper the concept of secondary energy absorbing device (SEAS) is being proposed which helped to achieve light weight design for chassis frame for body over chassis type crossover vehicle. In past Secondary Energy Absorbing Structures (SEAS) have been discussed in literature in the context of improving geometric compatibility between larger vehicles like SUVs and cars [3]. However no standard procedure has been defined yet to evaluate the compatibility aspects. The occupant protection in test conditions like ODB64 and FF56 is still area of focus for crash safety engineers. In this study emphasis was put on achieving weight reduction through introduction of new design concepts rather than using high strength steels and advanced