Crashworthiness of automotive steel midrails: Thickness and material sensitivity

The automotive midrail is the main load carrying/energy absorbing component in a frontal vehicle crash. Three separate midrails, from three different manufacturers, each of a different size class of vehicle, and each with different crush modes, were found to exhibit the same sensitivity to variations in material thickness and stress-strain properties. From the results it was determined that a general design guideline for crashworthiness could be stated as: For every 10% change in thickness there is approximately a 14% change in energy absorption capability for a crushing midrail, while for every 10% change in material strength there is approximately a 7·3% change in energy absorption capability. The proposed design guideline can be used to help determine suitable modifications to make a structure more crashworthy and, additionally, to determine how manufacturing variations may affect the crashworthiness of a vehicle.