Testing the Validity and Limitations of the Severity Index 700901
The head acceleration pulses obtained from monkey concussion, cadaver skull fracture (t = 0.002 sec), and football helmet experiments (0.006< t< 0.011 sec) have been subjected to injury hazard assessment by the Severity Index method. Although not directly applicable, the method correlates well with degree of monkey concussion. The range of Severity Indices for acceleration pulses obtained during impact to nine cadavers, all of which produced a linear fracture, was 540-1760 (1000 is danger to life) with a median value of 910. The helmet experiments showed good correlation between the Severity Index and the Wayne State University tolerance curve. These helmet tests also showed that a kinematics chart with curves of velocity change, stopping distance, average head acceleration, and time, with a superimposed Wayne State tolerance curve, can be useful in injury assessment.
The Vienna mathematical model of Slattenschek and Tauffkirchen proposed as an alternative method of hazard assessment to the Severity Index was tested with the football helmet data. Displacement response of the model increases relative to severity of impact and is in good agreement with predictions by the authors.
It is shown that the Severity Index method does not apply to a metal head form.