The Effect of Stiffness Coefficients on Output Variables in EDSMAC4 Simulations

Numerous studies have validated EDSMAC4 as an effective method of reconstructing automobile collisions; however, little has been done to investigate the effect of varying stiffness coefficients on the results of accident reconstruction and simulation analyses. When comparing simulations to staged collisions, the stiffness coefficients are frequently well defined; however, this is not always the case in real world accidents. Six vehicle-to-vehicle test impacts were modeled using EDSMAC4. Stiffness coefficients for the vehicles were obtained from test data of exemplar vehicles. After modeling the impacts with the base stiffness level, the stiffness coefficients were modified for both vehicles either plus (+) or minus (−) 25%. The impacts were re-run and the predicted vehicle damage (maximum crush and pattern), impact severity (Delta-V), peak acceleration, impact duration, post impact trajectory, and impact force was compared. The results indicate that, depending on the impact configuration, a ±25% change in stiffness coefficient may result in a significant change in the predicted peak acceleration, peak force, maximum crush, and post-impact travel. However, Delta-V was found to be very robust with regard to variation in stiffness coefficients. These findings indicate the importance of understanding the sensitivity of each output parameter when interpreting simulation model results.