Factor causing scatter in dynamic certification test results for compliance with EEVC WG17 legform impactor standard

A pedestrian legform impactor is a tool for the evaluation of car front bumper aggressiveness when simulating a pedestrian leg hit by a car. The Transport Research Laboratory (TRL) developed a legform impactor in compliance with the European Enhanced Vehicle-safety Committee (EEVC)/ WG17 specifications. The Commission of the European Communities (EC) proposed a dynamic certification test for a legform impactor, however, the test results using the TRL legform impactors manufactured to date have indicated an extremely wide scatter, especially in the maximum lower leg acceleration. Thus, the objectives of the present research are to clarify the factor possibly causing this scatter in the lower leg acceleration of the TRL legform impactor in the setup of the dynamic certification test, and to propose a way to adjust lower leg acceleration so as to comply with the corridor proposed by the EC. The repeatability and reproducibility of the legform impactor products and different impact points of the ram in the setup for the dynamic certification test were thus investigated. High repeatability and reproducibility of the legform impactor products were observed. No difference was observed in the effect of different ram points of impact against a stationary legform impactor on the maximum lower leg acceleration. On the other hand, the lower leg acceleration was found to be greatly affected by humidity in the test apparatus. Therefore, the effect of humidity on the dynamic certification test setup was also investigated. The results indicated that the maximum lower leg acceleration increased drastically with higher humidity. Next, the relation between humidity and acceleration measured by a ram impacting a piece of confor™ foam was investigated using a simplified test rig, since such foam sheathes the metal part of the legform impactor in a dynamic certification test setup. A strong relation between the humidity and acceleration was found. Thus concluded that humidity is a key factor affecting lower leg acceleration, and that adjusting it will be one of the many ways the lower leg acceleration can be made to comply with the proposed EC corridor in the dynamic certification test.