Physics Models for Vehicle Crush during Frontal Fixed-Barrier Impacts

Abstract

New conceptual and mathematical (C&M) models are introduced for vehicle frontal longitudinal crush during head-on impacts with fixed rigid concrete barriers and walls to sort out a range of crash test variables. This initial step is a prerequisite for developing C&M models for vehicle crush that results during angular impacts with rigid barriers along low-volume roads and on the National Highway System. Hierarchical decomposition provides a framework for systematic use of such models to examine local failure modes and deformation mechanisms. The standard constant acceleration equations of motion and the characteristic average response of vehicle crush force provide an effective basis for analysis. This paper introduces a new method for defining start and stop times derived from crash test data for crush on the basis of the structural rather than the cosmetic portion of total vehicle crush. The model enables self-consistent calculations for a range of quantities of interest (QOI) for analyzing standard crash tests within roadside safety and vehicle crash safety. Even though portions of the baseline mathematical model may be applied regardless of the constitutive model of crush deformation used, a perfectly plastic constitutive model is selected for quantifying the QOI of existing crash test data to demonstrate the model's capabilities. Examples of the model's self-consistency and trend analysis are provided. The paper demonstrates that the baseline model reasonably predicts vehicle motion and QOI in relation to vehicle velocity at frontal impact and depth of structural crush over a wide range of vehicles and velocities. A theoretical basis is recommended for extending the model to include analysis of angular impacts.