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Head Injury Criterion (HIC)

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Overview

An industry standard, the Head Injury Criterion (HIC) is a measure of the maximum weighted integral of resultant translational acceleration over any 15 ms or 36 ms duration of an impact event.  It is based on the integral of head acceleration measured at the Head CG.  Historically, HIC is based on the Wayne State Tolerance Curve (WSTC) and is calculated according to Equation 1.  Both HIC15 and HIC36 have been implemented into Metriks.
Equation 1

    \[HIC = max{\left[ {\frac{1}{{({t_2} - {t_1})}}\int\limits_{{t_1}}^{{t_2}} {a(t)dt} } \right]^{2.5}}({t_2} - {t_1})\]

 
Panel Descriptions
3D Representation of Sensor Location and Local Coordinate System Used for ProcessingSummary Tables with Risk of AIS 2+ Injury and Peak Acceleration Information
Time-History Plot of Resultant Head Acceleration and Time Clips for HIC-15 and HIC-36Injury Risk Curve for HIC-15 and HIC-36

Output Overview

Sensor TypeNodout
Sensory IDDefault: Node ID 1990001
Local Coordinate SystemDefault: LCS ID 1900001

Calculation Methods

  • Obtain resultant head acceleration from head CG (see Head Acceleration Summary)
  • Calculate HIC according to
     

        \[HIC = max{\left[ {\frac{1}{{({t_2} - {t_1})}}\int\limits_{{t_1}}^{{t_2}} {a(t)dt} } \right]^{2.5}}({t_2} - {t_1})\]

    where t_1 and t_2 are any two arbitrary times during the head CG resultant acceleration pulse a(t).

     This calculation is performed to obtain both HIC 15 and HIC 36.  Note that to speed the calculation of HIC, the acceleration time-history traced can be down-sampled.  By default, the GHBMC head acceleration is output at frequency of 10 kHz.  To speed calculations, the default GHBMC trace is down-sampled to 1 kHz.  This value can be modified in the Calculation Settings.
  • Obtain risk of AIS2+ head injury by plugging calculated HIC scores into Equation 2 below:

 

Equation 2
The probability of skull fracture ( {AIS \ge 2} ) is given by the formula,

    \[p(fracture) = N\left( {\frac{{\ln (HIC) - \mu }}{\sigma }} \right)\]

where N() is the cumulative normal distribution, \mu = 6.96352 and \sigma = 0.84664

References

[1] Eppinger, R., Kleinberger, M., Kuppa, S., Saul, R., & Sun, E. (1998). Development of improved injury criteria for the assessment of advanced automotive restraint systems. [2] Hertz (1993) A Note on the Head Injury Criteria (HIC) as a Predictor of the Risk of Skull Fracture. 37th Annual Proceedings of the Association for the Advancement of Automotive Medicine.