SEAT DESIGN DIFFERENCES AS A RESULT OF THE VARIETY OF GLOBAL WHIPLASH TEST PROCEDURES

摘要

Whiplash injuries still are a major vehicle safety issue. Even though the medical community has still not agreed on the question of whether whiplash is a low severity physical injury or merely a physical complaint, the development of testing-procedures were delayed due to the high economic costs. In years past, the procedure development to test for whiplash performance was mainly driven by insurance institutes. Later it was adopted by several national and regional NCAP-Programs and other complete car evaluation programs before finally being adopted by national legislation. Meanwhile, the automotive industry developed different measures to improve seat safety. This paper summarizes the technical solutions for seats with good whiplash performance that manufacturers have in their cars today. It also describes in particular the differences that can be derived from differences in testing procedures. The market-specific differences between these solutions directly tie back to different national and regional rating procedures. Starting with the IIWPG-initiative, a significant number of different test criteria and procedures have been developed. By now, most of these criteria and procedures have been integrated in complete car safety ratings. Additionally, the test equipment necessary to evaluate whiplash performance has been developed in parallel with the procedures. This brings up three major influences in procedure definition. First, the definition of criteria from the correlation of robust dummy behavior in specific seats to the data accumulated about the performance of the same seats in accidents. Second, the derivation of criteria from biomechanical injury mechanism while assuming a dummy with sufficient biofidelity. Third the accumulation of measurable dummy-performances to a cumulative low-level force on the dummy's spine. As a result of these different evaluation development processes, the different testing procedures deliver extreme rating differences for the same seat. Thus, the common goal of increasing whiplash performance for human passengers lead to different evaluation schemes and even contradictory criteria being used. At present there are test criteria that have to be actively declined to achieve an increased overall rating according to a different testing procedure. Regarding these conceptual procedure differences, the actual test proceduresfocus on different results. As a result of these different testing procedures, vehicle manufacturers optimized their seat design based on different criteria. It is important to note that local tests have the strongest effect on design details and optimization differences. Accordingly, many North American seat designs focus mainly on the reduction of head to head-restraint contact time in the test environment. In the meantime, Asian seat designs focus on neck-force minimization during the tests of head to head-restraint contact while the European manufacturers' seat designs focus on robustness with respect to differences in the test pulses. The common agreed-upon goal has to be one single testing procedure that correlates with accident data and can be reproduced with existing test-equipment.