Optical Measurement of High-Rate Dynamic Vehicle Roof Deformation during Rollover

The goals of this study were to examine the dynamic force-deformation and kinematic response of a late model van subjected to an inverted drop test and to evaluate the accuracy of three-dimensional multi-point roof deformation measurements made by an optical system mounted inside the vehicle. The inverted drop test was performed using a dynamic rollover test system (Kerrigan et al., 2011 SAE) with an initial vehicle pitch of −5 degrees, a roll of +155 degrees and a vertical velocity of 2.7 m/s at initial contact. Measurements from the optical system, which was composed of two high speed imagers and a commercial optical processing software were compared to deformation measurements made by two sets of three string potentiometers. The optical and potentiometer measurements reported similar deformations: peak resultant deformations varied by 0.7 mm and 3 ms at the top of the A-pillar, and 1.7 mm and 2 ms at the top of the B-pillar. The top of the vehicle B-pillar sustained peak resultant deformation of 146.2 mm 116 ms after contact, and unloaded to 77.1 mm (47% of peak) at 291 ms. Peak reaction forces at contact were approximately 100 kN, and the force-deflection response between the drop test and the IIHS roof crush test on the same make and model vehicle showed comparable dynamic and quasi-static stiffness. The results presented in this study showed that the optical system can be used to measure dynamic roof deformations, in three dimensions, at high rates, across a large area of the vehicle structure, from inside a vehicle subjected to rollover crash test.