Optimization of Vehicle Structures under Uncertainties

Abstract

Cover: Schematic illustration of robustness analysis. The histograms indicate the variations in input parameter ‫ݔ‬ and the output parameter ݂ respectively.The front cover picture is reproduced by courtesy of Volvo Car Corporation and illustrates a side impact simulation.Printed by: LiU-Tryck, Linköping, Sweden, 2017 ISBN 978-91-7685-630-7 ISSN 0345-7524 Distributed by: Linköping University Department of Management and Engineering SE-581 83 Linköping, Sweden © 2017 Sandeep ShettyNo part of this publication may be reproduced, stored in a retrieval system, or be transmitted, in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without prior permission of the author. Advancements in simulation tools and computer power have made it possible to incorporate simulation-based structural optimization in the automotive product development process. However, deterministic optimization without considering uncertainties such as variations in material properties, geometry or loading conditions might result in unreliable optimum designs.In this thesis, the capability of some established approaches to perform design optimization under uncertainties is assessed, and new improved methods are developed. In particular, vehicle structural problems which involve computationally expensive Finite Element (FE) simulations, are addressed.The first paper focuses on the evaluation of robustness, given some variation in input parameters, the capabilities of three well-known metamodels are evaluated. In the second paper, a comparative study of deterministic, reliability-based and robust design optimization approaches is performed. It is found that the overall accuracy of the single-stage (global) metamodels, which are used in the above study, is acceptable for deterministic optimization. However, the accuracy of performance variation prediction (local sensitivity) must be improved. In the third paper, a decoupled reliability-based design optimization (RBDO) approach is presented. In this approach, metamodels are employed for the deterministic optimization only while the uncertainty analysis is performed using FE simulations in order to ensure its accuracy.In the fifth paper, two new sequential sampling strategies are introduced that aim to improve the accuracy of the metamodels efficiently in critical regions. The capabilities of the methods presented are illustrated using analytical examples and a vehicle structural application.It is important to accurately represent physical variations in material properties since these might exert a major influence on the results. In previous work these variations have been treated in a simplified manner and the consequences of these simplifications have been poorly understood. In the fourth paper, the accuracy of several simple methods in representing the real material variation has been studied. It is shown that a scaling of the nominal stress-strain curve based on the Rm scatter is the best choice of the evaluated choices, when limited material data is avail...

El software de simulación como herramienta para el análisis de estructuras metálicas automotrices

“…Hui Gao subraya aún más el papel de la tecnología de simulación en el software estructural, destacando su creciente importancia debido a los avances en la tecnología informática (Gao, 2017). Sandeep Shetty y Simone Vizzini destacaron la necesidad de realizar análisis dinámicos detallados y utilizar la sub estructuración dinámica para gestionar modelos grandes de manera eficiente, reduciendo el tiempo de simulación y manteniendo la precisión (Shetty, 2017;Vizzini, 2014). Por último, P. R. Marur y S. Srinivas presentaron una técnica de análisis por elementos finitos de orden reducido para predecir el comportamiento en caso de colisión, lo que demuestra la tendencia hacia métodos de análisis más eficientes y localizados (Marur & Srinivas, 2008).…”

Metamodel-Based Multidisciplinary Design Optimization of Automotive Structures

“…The primary aim of the project is to find suitable methods for implementing large-scale robust and multidisciplinary design optimization of automotive structures within current product development. Methods for dealing with optimization under uncertainties are covered by Shetty (2017). This thesis focuses on topics associated with simultaneous optimization of aspects related to different disciplines or load cases.…”