The recently developed Translational Energy Criteria (TEC) for predicting head injury severity was used to analyze three types of theoretical pulses represented by triangular, half-sine, and trapezoidal pulses as shown in Figure 1. These pulses were used as an input force to-a lumped parameter model represented by the Translational Head Injury Model (THIM) of the human head in the TEC analysis. The effects of impact duration, pulse shape and magnitude on the dynamic responses of the THIM model were studied in detail. Pulse durations ranging from 2. to 20. msec were analyzed in order to study the full range of all normally observed human head impacts (rigid or padded). An input force pulse amplitude of 1000. lb, was used in all analyses except where the effects of impact force magnitude were evaluated. Variations of the peak force, F(t), and acceleration, A,(t), with respect to pulse duration at two constant energy levels were studied. Energy constants which represent head injury severity equivalent to AIS scale of 2 and 4 were evaluated in detail for impacts in both the A-P and L-R directions.

The analysis of the effects of the impact force duration on the dynamic responses of the head model indicates that for pulse duration between 5. to 20. msec, the energy function of the TEC increases as the pulse duration increases when all other variables are kept constant. This is consistent with the general conclusion that a harder impact (higher magnitude and/or longer duration impact) causes a more severe head injury. For shorter duration impact, the TEC shows that skull fracture is predominant. In addition, the TEC results indicate that the pulse shape with highest input momentum has the highest energy value, thus predicting the most serious head injury. The effects of pulse amplitude on the energy function is determined to be a square relationship. Therefore, a higher magnitude impact will result in a more severe head injury when all other variables are unchanged. The variational studies indicate that results from one TEC energy level may be used at other energy levels through proper parametric adjustments.