Targeting the acceleration-time response of vehicle structures under crash impact using equivalent dynamic loads

Abstract

This work introduces an optimization procedure derived from the targeting force-displacement response (TFDR) method to improve the crashworthiness of full-size vehicle structures. The proposed method aims at targeting the vehicle’s acceleration-time response (ATR) under a crash event using topometry (thickness) optimization. In contrast to the original TFDR method, the proposed targeting method uses a moving coordinate system (MCS) that allows addressing fully dynamic crash models with initial velocity. By setting a proper target ATR curve, the proposed method can improve several crashworthiness indicators including specific energy absorption, maximum deceleration, dynamic penetration, and crash load efficiency. The result of the topometry optimization could be a guideline for the further design. In the proposed method, the nonlinear optimization problem is discretized into a series of analytical subproblems using equivalent dynamic load (EDL). In each iteration, the dynamic response from an explicit dynamic finite element (FE) analysis is utilized to define and solve a subproblem. To demonstrate the proposed iterative method, the baseline FE model of a Dodge Grand Caravan vehicle, obtained from the US National Highway Traffic Safety Administration (NHTSA) website, is optimized. The results show the effectiveness of the algorithm finding the element thickness distribution to make the acceleration-time response of the vehicle’s center of gravity (VCG) gradually approach a target curve. The proposed EDL algorithm finds a converged solution using less than 15 crash simulations. This makes it possible to solve problems involving full-size vehicle FE models.