DYNAMIC PEDESTRIAN PROTECTION - INFLUENCE OF TOLERANCES OF THE HEAD IMPACT TIME (HIT) ON THE HEAD INJURY CRITERION (HIC) DURING DYNAMIC TESTING OF DEPLOYABLE BONNETS

摘要

Vehicle-pedestrian crashes are still a major threat to life. In these crashes, head injuries cause most of the pedestrian fatalities. To address this issue, car manufacturers have developed countermeasures such as deployable bonnets, and legislators and consumer ratings have introduced specific testing for such bonnets. Within the scope of deployable bonnet testing, one of the most complex test scenarios is dynamic testing. In dynamic testing, a head impactor impacts a bonnet while it is in its deployment phase. Generally, car manufacturers need to provide test result predictions within 10% accuracy in advance to consumer rating tests. If the predictions are outside of 10% accuracy, a correction factor is applied to all predictions, meaning that the test score will change considerably. For dynamic head impact testing, currently, no contact time tolerance is defined in the protocols. The present study investigates the relation between dynamic head impact test results and contact time with the aim to provide a contact time tolerance suggestion to consumer ratings. Eight physical tests and 18 finite element simulations were conducted dynamic head impact boundary conditions. The results showed a clear influence of the contact time on the test results. With a contact time difference of more than 4 ms, the results differed by more than 10%. For car manufacturers, increasing the prediction capability increases the planning security and thus adds to the motivation to further develop deployable bonnets. Therefore, introducing contact time tolerances into dynamic head impact testing protocols is highly recommended.