Dynamic Crush Tests Research Articles

Assessment of vehicle roof crush test protocols using FE models: inverted drop tests versus updated FMVSS No. 216

Inverted drop test is a dynamic roof crush test which is simple, realistic, reliable and easily implemented. It can produce repeatable roof impacts that can be used to compare one test run with another and has long been used by the automotive industry and researchers to test roof integrity. However, practical full-scale vehicle roof crush tests are always very costly, especially for finding out the impact orientation for the worst structural behaviour. Computer simulation can provide an effective solution, since it is highly repeatable, and under different environmental conditions permits the variation of parameters to evaluate sensitivity. A full-scale Finite Element model of Ford Fiesta that was originally modelled in parts by Ford Motor Company using Radioss code was translated into LS-DYNA3D and refined through extensive employment of better elements and spotwelds formulation. The inverted drop-test simulation, therefore, was made using a combination of different pitch and roll angles in the search of the worst-case rollover condition. These parametric studies show the critical vehicle orientation at roof impact that causes the highest amount of roof crush to be 10° pitch angle and 12.5° roll angle. This is similar to the test conditions employed in the experimental test using a Renault Clio. The results obtained from simulating these two different vehicles show the existence of some design problems, i.e., a very weak roof that is supported by weak roof rails and weak reinforcing plates. Furthermore, the inverted drop-test simulation results depict clearly the differences between static roof crush tests based on FMVSS No. 216 that is loaded along a fixed orientation and only reflects the roof strength, rather than the pillar's strengths, response in that direction. The dynamic test in that sense is more realistic and closer in nature to a number of recorded real-world accidents.

Dynamic crush tests of energy-absorbing laminated composite plates

For the first time, dynamic crush data of edgewise-loaded composite plates are presented. A crush test fixture for flat composite specimens, initially developed to measure quasi-static crush response, has been adapted for use in a drop tower to measure dynamic crush response. The influence on energy absorption of stacking sequence, trigger mechanism and thickness was evaluated for three material systems: APC-2 (graphite/thermoplastic), AS-4/3502 (graphite/epoxy) and a hybrid AS-4—Kevlar 49/3502. Energy absorption of APC-2 plates crushed under quasi-static loading conditions is significantly higher than for the other two material systems. There was dramatic reduction in energy absorption for APC-2 plates crushed at dynamic loading rates (5 to 7 ms 1), with only slight reductions for the others.

Correction of Distortions in Dynamic Crush Test Data Due to Load Cell Inertia Effects

The application of deconvolution techniques to the results obtained in the dynamic collapse of tubes in axial compression is described. It is shown that low pass filtering techniques are not adequate to obtain complete information on the crush characteristics. Data distortion caused by load cell resonance can be corrected by deconvolution provided that a notch filter is used to reduce the amplitude of the resonance response prior to deconvolution.