Converting post-crash deformation into energy equivalent speed (EES): Toward an objective measure of crash severity

Abstract

In this paper, an objective method for the conversion of post-crash vehicle deformation to crash energy is presented. While the crash severity assessment for standard crash test configurations is relatively robust, bias in real-world crash reconstruction is a well-known problem. A method to reduce the bias in crash severity reconstruction is constructed by focusing on post-crash deformation, the principle direction of force ( PDOF), and vehicle type ( VT) only. The analysis was restricted to 12 PDOF and six VT. A voxel model, onto which the depth information of the post-crash deformations was mapped, was constructed for every PDOF and VT. Standardized crash tests were used to normalize the deformation energy assigned to each voxel. The plastic deformation energy was computed by integrating this energy across all deformed voxels. This energy is expressed as the “energy equivalent speed” ( EES). The method allows for a retrospective calculation of the EES from deformations. Thus, objective EES values can be computed for crash databases like CISS or GIDAS and even for legacy databases like NASSCDS. The results from the EES model will become part of the standard GIDAS database. The EES model was tested using a car-to-car crash test, a 40% offset frontal-frontal collision of an Audi Q7 against a Fiat 500.