Static and dynamic roof crush simulation using LS-DYNA3D

Abstract

Quasi-static roof crush simulations based on FMVSS 216 have been carried out successfully on a small European car, and different loading conditions have been tested. Results show that bonded windscreens contribute at least 30% of roof strength based on FMVSS 216. This confirms experimental test results carried out by other researchers. Furthermore, results show that the roll and pitch angles are a function of roof strength and greatly influence the overall behaviour. For instance, with the same pitch angle, the roof strength greatly drops as the roll angle goes up from 15° to 45°; but the magnitude of roof strength drop is minimal as the pitch angle increases. While for the same roll angle, the roof strength is seen to decrease as the pitch angle increases from 0° to 10°; but it does not mean that the bigger the pitch angle, the weaker the roof strength becomes. In fact in the case of a 10° pitch angle, the roof strength exhibits worst results. The recommendations on the updated FMVSS 216 are a roll angle of 45° (not 25°) and a pitch angle of 10° (not 5°). These constitute more realistic test angles that replicate real world accident data. In addition to quasi-static virtual testing, some dynamic simulations are also carried out based on two dynamic test methodologies, namely the inverted car drop in a cylindrical ditch and on a flat ground. Results show severe roof damage to occur in the former test scenario despite both having same initial conditions. The paper has also defined corridors for the best design of a car roof.