HIC(d) and Its Relation With Headform Rotational Acceleration in Vehicle Upper Interior Head Impact Safety Assessment 2008-01-0186

Upper interior head impact safety is an important consideration in vehicle design and is covered under FMVSS 201. This standard generally requires that HIC(d) should not exceed 1000 when a legitimate target in the upper interior of a vehicle is impacted with a featureless Hybrid III headform at a velocity of 15 mph (6.7 m/s). As HIC and therefore HIC(d) is based on translational deceleration experienced at the CG of a test headform, its applicability is often doubted in protection against injury that can be caused due to rotational acceleration of head during impact. A study is carried out here using an improved lumped parameter model (LPM) representing headform impact for cases in which moderate to significant headform rotation may be present primarily due to the geometric configuration of targets. The present LPM is an extension of an earlier work and its properties are arrived at using responses obtained from analyzing equivalent finite element models with the explicit LS-DYNA code. It is observed that compliance to FMVSS 201 requirement will generally imply low rotational acceleration although theoretically even for low HIC(d) values, the resultant contact angle can potentially cause headform peak rotational acceleration to be above a reported concussion threshold range.