Development of objective metrics to improve vehicle compatibility in frontal collisions

The objective of achieving vehicle crash compatibility is to minimize injury risks for all occupants involved in the collision. This research contributes to the existing knowledge on crash compatibility in frontal collisions with the aim of developing objective compatibility metrics. Researchers worldwide have proposed different laboratory crash tests to measure the aggressivity and partner-protection capability of a vehicle. These tests assess vehicle structures, mainly the front geometry and stiffness, based on numeric measures derived from the vehicle and barrier instrumentation. Limits on these numeric measures are proposed to improve structural interaction between two vehicles in frontal collisions to achieve crash compatibility.;This research investigates the potential of using an existing self-protection laboratory crash test to assess vehicle structures for partner-protection. The proposed laboratory crash test in this study, for improving compatibility in the vehicle fleet, is the current US Frontal New Car Assessment Program (NCAP) test. In this test, the vehicle impacts a planar rigid load cell barrier at 35 mph with full overlap. Two objective compatibility assessment metrics, one, to characterize the location of the primary load path and two, to characterize the stiffness of the frontal vehicle structure, were developed based on and building upon existing literature. These are the Average Height of Force 400 (AHOF400) and the Crush-Work Stiffness 400 (Kw400). The compatibility assessment metrics were restricted to be calculated only up to 400 mm of dynamic crush of the vehicle front-end. The reason for choosing this limit is because the vehicle design in this region can be better controlled to improve partner-protection without sacrificing its own self-protection.;AHOF400 is a measure of the vertical centroid of forces exerted on the barrier surface. Kw400 is a measure of the work required to crush 400 mm of a vehicle's front-end. Several studies in the past had concluded that there are large inherent errors in the AHOF measure. One of the main factors influencing the error in this measure was the size of the load cell on the barrier face. A load cell design which can measure force in the impact direction and moment about the lateral axis is proposed to eliminate the error source in the AHOF400 measure. Finite Element Simulations (FEM) with different vehicle types is conducted to justify the need for the proposed load cell design to accurately measure height of force.;A load cell wall configuration is proposed based on the results of a cost/benefit analysis and the harmonization potential with other proposed compatibility tests being discussed worldwide. To ensure the robustness of the compatibility assessment metrics, a sensitivity analysis was conducted by varying the impact speed and vehicle mass under nominal conditions.;The benefits of using the proposed objective compatibility assessment metrics were evaluated using FEM of vehicle-to-vehicle frontal collisions. The AHOF400 and Kw400 ratios between the two vehicles were varied to study their effects on structural interaction. The energy absorbed by the frontal structures and the occupant compartment of the vulnerable vehicle was characterized as a measure of structural interaction. The results from these simulations showed improved structural interaction and energy sharing when the AHOF400 and Kw400 ratios were lowered between the two vehicles.