The application of the new mean strain criterion (nmsc)

The mean strain criterion (msc) is now over ten years old. This head injury criterion was formulated on many head impacts to subhuman primates and then extrapolated to humans by dimensional analysis. Also, the connection between force-time input for the primates and acceleration-time input for dummies was made without justification. Add to this a recent interest in having a head injury criterion which predicts AIS numbers 0 through 6 and it becomes of interest to rework the msc into a new criterion. This study, based on the msc concept, inputs the head impact force from cadaver head impacts into the msc mechanical impedance two-mass head models to generate a new criterion, "the new mean strain criterion" (nmsc). This was done by remodeling the old msc head impedance model for four directions. The model system equations were then solved to obtain the model input force and the model output deflection. The deflection was then used to obtain the human equivalent strain and strain rate, and thus, the potential for injury. The results show that given a force-time trace for humans or an acceleration-time trace for dummies, the nmsc is useful in predicting the potential for injury during a translational head impact. (Author/TRRL)