Abstract The objective of this study was to assess the accuracy of using high-speed frontal barrier crash tests to predict the impact speed, i.e. equivalent barrier speed (EBS), of a lower-speed frontal barrier crash. Force-displacement (F-D) curves were produced by synchronizing the load cell barrier (LCB) data with the accelerometer data. Our analysis revealed that the F-D curves, including the rebound phase, for the same vehicle model at the same impact speed were generally similar. The test vehicle crush at the time of barrier separation, determined from the F-D curves, was on average 17±16% (N = 150) greater than the reported maximum hand-measured residual crush to the bumper cover. The EBS calculated from the F-D curves was on average 4±4% (N=158) greater than the reported EBS, indicating that using F-D curves derived from LCB data is a reliable method for calculating vehicle approach energy in a crash test. Our method of using F-D curves from high-speed tests to predict the EBS of a lower-speed barrier crash overestimated the EBS of actual lower- speed tests by an average of 21±9% (N = 129). Further work in developing and reining our method is needed to improve the accuracy of predicting a lower-speed EBS. Introduction One method of determining the severity of a collision is to calculate the deformation energy based on the vehicle crush and an estimate of the vehicle stiffness. Current methods estimate the vehicle stiffness using linear or non-linear crush coeficients. Linear crush coeficients assume constant vehicle stiffness and rely on measurements of residual crush, i.e. static crush, of crash test vehicles [1, 2, 3]. Several methods exist for determining non-linear crush coeficients. One method is to create a polynomial it of the square root of 2E/w and residual crush [4, 5, 6, 7]. In instances where there are no tests conducted at lower-speeds, the deformation energy is determined by integrating portions of the force-displacement (F-D) curve from a load cell barrier (LCB) crash test [7]. Another method for determining non-linear crush coeficients is by calculating a polynomial it of a pressure-displacement (P-D) curve [8]. P-D curves are generated from F-D curves of crash tests conducted at the highest available impact speed for the vehicle model. Methods that rely on linear crush coeficients or non-linear crush coeficients derived from F-D curves assume that barrier impacts at lower-speeds would mimic the F-D curve of a higher speed barrier impact. Our study investigates this assumption using an alternative prediction method that does not rely on crush coeficients or residual bumper cover crush measurements to estimate vehicle stiffness. Instead, our method shifts the rebound proile of a high-speed F-D curve to the same crush at barrier separation as that of an actual lower-speed F-D curve (see methods for more details). In other words, we assume that the separation velocity of a high-speed test is the same as that of a lower-speed test. Previous literature has shown similar rebound proiles for F-D curves for repeated impacts of increasing severity of the same vehicle [9]. Other literature has shown the same vehicle model exhibits similar separation velocities for a wide range of barrier impact speeds [10]. Since our prediction method directly compares F-D curves from high- and lower-speed tests, any errors in our lower-speed predictions would be directly correlated with differences in high- vs lower-speed F-D data. The National Highway Trafic Safety Administration (NHTSA) conducts many crash tests, and in addition to reporting the impact speed and residual crush data, they also record dynamic data from load cells on a rigid barrier and linear accelerometers mounted at various locations on the test vehicle. These accelerometer data can be double integrated to estimate the vehicle displacement and then synchronized with the load cell data to generate F-D curves, as outlined in detail by Gilbert et al [8]. In theory, the area under the F-D curve from LCB data is expected to equal the mechanical work done to the vehicle, i.e. the deformation energy dissipated by the vehicle, during the collision; however, previous literature has found this method will over-represent the energy dissipated in the crash [11]. We investigated the accuracy of the LCB data by comparing NHTSA’s reported EBS to the EBS calculated from the F-D curve so that readers could quickly identify which barrier impact speeds were used in the comparisons. Using Force-Displacement Data to Predict the EBS of Car into Barrier Impacts 2016-01-1483 Published 04/05/2016 Ross Hunter, Ryan Fix, Felix Lee, and David King MEA Forensic Engineers and Scientists CITATION: Hunter, R., Fix, R., Lee, F., and King, D., "Using Force-Displacement Data to Predict the EBS of Car into Barrier Impacts," SAE Technical Paper 2016-01-1483, 2016, doi:10.4271/2016-01-1483. Copyright © 2016 SAE International Downloaded from SAE International by Felix Lee, Friday, March 11, 2016