Significance of Head-to-Knee impacts—A Comparison of Dummy and Cadaver Responses

Head-to-knee interaction of the right front passenger dummy can occur in some 30-35 MPH crash barrier tests. The biofidelity and significance of these interactions as related to predicting human response was addressed in this study. In a series of laboratory experiments an instrumented headform was dropped on the dummy knee to simulate the barrier interactions. These test results were then related to the human by dropping the same headform on the cadaver leg.

The instrumented headform was dropped from three heights to impact the Part 572 dummy knee at three velocities. Two impact sites and two impact angles were used. These test parameters bracketed the barrier conditions. Measurements from headform accelerometers permitted calculation of HIC value for comparison to barrier values. Comparable experiments were subsequently performed with three unembalmed cadaver subjects using the same headform and test procedures.

Impacts on the 90 degree flexed dummy knee at 6 and 7 m/s were found to correspond to the HIC vs impact velocity “window” of barrier test results(400-1400 HIC and 5.8-7.2 m/s). Identical tests on the knees of three unembalmed cadaver subjects produced HIC values averaging 45% of the dummy values.

Head-to-knee impact tests on cadaver subjects indicate a lack of biofidelity in the dummy lower leg structure for this type of impact. Assuming that head-to-knee interaction actually occurs in field accidents, values of HIC measured from dummy crash simulation experiments are likely to overestimate the severity of the interaction.