Use of Repeated Crash-Tests to Determine Local Longitudinal and Shear Stiffness of the Vehicle Front with Crush

Crash-test-data on local longitudinal and shear stiffness of the vehicle front is needed to estimate impact severity from car deformation in offset or pole impacts, and to predict vehicle acceleration and compartment intrusion in car-to-car crashes. Repeated full frontal crash-tests were carried out with a load-cell barrier to determine the local longitudinal stiffness with increasing crush. Repeated off-set tests were run to determine shear stiffness. Two single high-speed tests (full frontal and offset) were carried out and compared to the repeated tests to determine the rate sensitivity of the front structure. Four repetitions at 33.4 km/h provided equivalent energy absorption to a single 66.7 km/h test, when rebound was considered. Power-train inertial effects were estimated from highspeed tests with and without power-train.

Speed effects averaged 2% per [m/s] for crush up to power-train impact, and post-crash measurements were a reasonable estimate of front-structure stiffness. Power-train inertia significantly increased the barrier force in the high-speed crashes. The repeated tests provide local longitudinal and shear stiffness estimates of the vehicle front structure with deformation in an effective and inexpensive way. The results are useful data for compatibility and accident reconstruction purposes, especially in cases of non-distributed frontal crush. The test method also assesses mass and stiffness aggressivity.