Experimental and analytic determining of the characteristics of deformation and side stiffness of a motor car body based on results of side-impact crash tests

Abstract

Front-to-side collisions of motor vehicles very often occur on Polish roads. Every fourth road accident may be defined as a collision of this kind between moving vehicles. The analysis of accident effects, including the accident reconstruction process, is usually based on results of measurements of post-accident vehicle deformation and on information about vehicle body stiffness. Unfortunately, the information about the characteristic curves that would represent the deformation of a car body side is hardly available.The objective of this study is to present a method of determining the characteristics of deformation and side stiffness of a motor car body based on crash test results. This objective was pursued with using results of NHTSA crash tests and of crash tests carried out at PIMOT. The analysis covered herein has been based on crash tests representing front-to-side collisions of motor cars, motorcycle impact against a car side, and frontal impact of a car against a barrier. Based on a combined analysis of the course of such experiments, mathematical models have been built that describe the dynamics of the deformation process in the vehicle contact zone. The model calculation results obtained with using results of measurements carried out during the crash tests have been worked out with using the linear regression method.Based on the experimental and analytic methods, curves were plotted that represented the impact force as a function of the deformation of individual car bodies and then the characteristics of car body side deformation were determined. The range of this deformation and the hazard arising from the side impact to vehicle occupants were also shown. A special aspect of this hazard has also been unveiled by the calculation results, according to which the side stiffness of a car body decreases with growing deformation depth. In the initial deformation phase, this stiffness is even by 35 % higher in comparison with that observed when the vehicle body side is deformed by more than 20 cm.