A Comparison Between Head Impact Response of Hybrid III and THOR-NT Dummy Heads in FMVSS201 Tests

Abstract

The impact response of the forehead of both the Hybrid III dummy and THOR dummy was designed to the same human surrogate data. Therefore, when the forehead of either dummy is impacted with the same initial conditions, the acceleration response and consequently the head impact criterion HIC should be similar. If the THOR dummy is used in the FMVSS 201 free motion headform tests, then when it strikes the interior trim of the vehicle, as prescribed by the FMVSS 201 procedure, the acceleration response should be similar to that of the Hybrid III, as long as only the forehead engages the vehicle interior. To compare and contrast the response of the two dummy heads under FMVSS 201 testing, a design of experiments (DOE), that is a function of seven variables, is utilized to develop a mathematical model of the Head Impact Response. These independent parameters include five trim manufacturing process variables that relate to the interior that the dummy head hits in 201 testing: mold temperature, melt temperature, packing pressure, hold pressure, and injection speed. Two operational variables were also considered: free motion Headform approach angle and the dummy head drop calibration. An incomplete block design approach is utilized in order to significantly reduce the number of experiments. The DOE approach determines the response in the form of the Head Impact Criterion (HIC) with respect to the seven variables at 99% confidence level. The results describe the response data of both dummy heads. The response data of the dummy heads is described. Results indicate that the Hybrid III dummy head and the THOR dummy head have significantly different response characteristics in terms of magnitude of response, variation to different input conditions, repeatability, HIC values, and acceleration time history.