MADYMO Modeling of the IHRA Head-form Impactor

The International Harmonization Research Activities Pedestrian Safety Working Group (IHRA PSWG) has proposed design requirements for two head-forms for vehicle hood (bonnet) impact testing. This paper discusses the development of MADYMO models representing the IHRA adult and child head-forms, validation of the models against laboratory drop tests, and assessment of the effect of IHRA geometric and mass constraints on the model response by conducting a parameter sensitivity analysis. The models consist of a multibody rigid sphere covered with a finite element modeled vinyl skin.

The most important part in developing the MADYMO head-form models was to experimentally determine the material properties of the energy-absorbing portion of the head-form (vinyl skin) and incorporate these properties into MADYMO using a suitable material model. Three material models (linear isotropic, viscoelastic, hyperelastic) were examined. It was determined that the vinyl material behaved as a hyperelastic material when comparing MADYMO simulation results with laboratory certification test results. The MADYMO model of the IHRA adult head-form was validated with laboratory head-form drop tests from four different heights. Parameter sensitivity analysis was conducted by varying the head-form parameters within their respective IHRA tolerances. Because of physical limitations of locating accelerometers near the head-form center of gravity, this analysis was much more easily accomplished using a MADYMO model. It was found that the peak acceleration was well within the IHRA-specified range for both the adult and child head-forms when the mass and geometric parameters were varied within the IHRA tolerances.