BIW Multidisciplinary Design Optimization (MDO) with Equivalent Static Load Method - Quick MDO Methodology

Abstract

Multidisciplinary Design Optimization (MDO) of an automobile body structure is a challenging task as it involves multiple, often conflicting requirements of safety, durability & NVH. Conventionally MDO process requires running large number of design of experiments (DOE) to explore the full design space and to build response surface for optimization. As the safety simulations are highly nonlinear in nature, they typically require significant amount of computational time and resources. Hence the conventional MDO approach is too expensive if too many design variables are simultaneously considered. In this paper, an alternative approach using Equivalent Static Load (ESL) method has been suggested for MDO which is quicker & accurate. The basic idea of the Equivalent Static Load-Method (ESL) is to divide the original nonlinear dynamic optimization problem into an iterative linear optimization and nonlinear analysis process. As the durability and NVH load cases are linear in nature, they can easily be combined with ESL method to solve a large scale MDO problem. In the present work, MDO has been performed on one of the production SUV BIW using ESL technique. Critical global load cases from safety, durability & NVH domains have been identified as constraints which have significant influence on the overall vehicle performance. Remaining vehicle load case requirements are broken down into local stiffness constraints and the MDO problem is solved using ESL technique with an objective of minimizing the mass through gauge optimization method (Sizing). Finally, the optimized solution has been verified by conducting the Crash/Durability & NVH simulations.