3.4       Evaluation Methods And Applications Of Injury Criteria

Within each of the body part injury criteria sections, methods for evaluating the injury criteria have been discussed, both in terms of physical testing and computer simulations.

Anthropomorphic Test Devices (ATD’s), crash test dummies, or computer simulations of them, are the methods used for assessing injury criteria.  The two main reasons.

• Accurate reproduction of human body kinematics in impact situations, both with and without restraint systems, producing the correct impact locations, impact velocity and subsequent loads
  
  
• Repeatable kinematics, impact velocities and impact loads, which are critical in the design and validation of restraint and other occupant protection systems.

As the human body has different biomechanical characteristics in frontal, lateral and rear impact directions, specific ATD’s have been developed for each impact direction.  Also to reflect the range of sizes in the human population, different types of dummy have now been produced in different sizes.  Table 44 in Appendix 1, shows the main current ATD’s in use, along with some still under development.

Instrumentation installed into the specific body part of the ATD is used to measure the parameter defined in the injury criteria.  For example, a triaxial arrangement of accelerometers mounted at the centre of gravity of the HIII head is used to evaluate the Head Injury Criterion (HIC).  Appendix 1, Table 45 details the complete list of the occupant body part injury criteria is shown, followed by the criteria in Table 46 Appendix 1, which can be evaluated using current instrumentation systems in the current range of ATD’s.  For completeness the instrumentation signal analysis requirements are also given.  All these injury criteria can also be assessed in the various computer models of the dummies whether these are in MADYMO or dynamic finite element codes (DYNA-3D).

In the evaluation technique developed to assess the occupant protection performance of rail vehicle interiors, occupant injury severity is predicted using the potential impact velocity and the characteristics of the impacted object.  Therefore, each injury criteria tolerance level has to be represented as an impact velocity.  In Table 47, Appendix 1, the injury criteria tolerance levels have been converted into an impact velocity into a blunt rigid object.  Most of these are crude estimates based on the authors experience and knowledge of ATD’s, in crash and sled testing. Further work with both computer simulations and physical tests are required to validate these impact velocities.