Pedestrian Impact Testing: Modelling the Effect of Head-form Mass and Speed

Pedestrian impact testing is used to assess the relative level of protection from a vehicle to a pedestrian in the event of a collision. Testing is conducted as part of new car assessment programs (Euro NCAP, ANCAP), and for compliance with regulations in Europe and Japan. A key component of pedestrian impact testing is the head-form test, in which a dummy head-form is fired into the front of the vehicle in free flight, at specific locations typically on the bonnet or windscreen. The acceleration of the head-form is measured and is used to assess the relative level of protection at that location through calculation of the Head Injury Criterion (HIC). Alternative protocols specify different test head-form masses and speeds. This paper presents a model of the acceleration response of the head-form in any given test condition. Given a test with a known result, the model can be used to estimate the outcome of a test on the same structure using a different head-form mass and/or speed. The model is a non-linear damped Hertz model of contact. Validation data showed that the model estimates the HIC to within 10% of that obtained from test results. Simulation of a series of generic impact scenarios was conducted under the conditions of the Australasian New Car Assessment Program (ANCAP) and the draft Global Technical Regulation (GTR) on pedestrian protection, which stipulates a different head-form mass and speed. The results indicate a large discrepancy exists between performance in an ANCAP test and performance under the GTR, such that a structure that would pass the GTR may be rated very poorly under the ANCAP test.