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FMVSS 223 and 224 set standards for “Rear Impact Protection” for trailers and semi-trailers with a gross weight rating greater than 10000 pounds. A limited amount of experimental data is available for evaluating the different performance attributes of rear impact guards. The crash tests are usually limited to fixed parameters such as impact speed, guard height, strength and energy absorption, etc. There also seems to be some misunderstanding of the interdependence of guard strength and energy absorption, and their combined effect on the guard's ability to limit underride while keeping occupant acceleration forces in a safe range. In this paper, we validated the Finite Element (FE) model of an existing rear impact guard against actual FMVSS 223 tests. We also modified a previously evaluated FE model of a 1990 Ford Taurus by updating its hood geometry and material properties.

The first objective of this paper was to evaluate a public domain finite element (FE) model of a 1990 Ford Taurus from the perspective of crush energy absorption. The validity of the FE model was examined by first comparing simulation results to several published full-frontal crash tests. Secondly, the suitability of the model for underride simulation was evaluated against two series of full-scale crash tests into vertically offset rigid barriers. Next, the evaluated FE model was used to pursue the main objective of this work, namely to develop an approach for estimating underride crush energy. The linear-spring methodology was adopted whereby the underride crush stiffness was determined by relating the residual upper radiator support deformation to crush energy. An underride crush stiffness estimation method was proposed based on modifying the full-frontal stiffness coefficients.