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Finite element based robustness study of a truck cab subjected to impact loading
Linköping University, Department of Management and Engineering, Solid Mechanics. Linköping University, The Institute of Technology. (Hållfasthetslära)
Linköping University, Department of Management and Engineering, Solid Mechanics. Linköping University, The Institute of Technology.
Linköping University, Department of Management and Engineering, Solid Mechanics. Linköping University, The Institute of Technology.
Linköping University, Department of Management and Engineering, Solid Mechanics. Linköping University, The Institute of Technology.
2009 (English)In: International Journal of Crashworthiness, ISSN 1358-8265, Vol. 14, no 2, 111-124 p.Article in journal (Refereed) Published
Abstract [en]

Optimised designs have a tendency of being sensitive to variations. It is therefore of great importance to analyse this sensitivity to assure that a design is robust, i.e. sufficiently insensitive to variations. To analyse robustness, variations are introduced in model parameters and their influences on simulation responses are studied. This is usually achieved using the Monte Carlo method. Though, due to the large number of simulations needed, the Monte Carlo method is very costly for problems requiring a long computing time. Therefore, in this work a meta model-based Monte Carlo method is used to evaluate the robustness of a vehicle structure. That is, the Monte Carlo analysis is performed on a surface approximation of the true response, over the domain of interest. The methodology used is to first identify the variables that influence the response the most, referred to as a screening, using simple linear response surfaces. This is followed by a more detailed sensitivity analysis using only the identified variables and a quadratic response surface, thereby incorporating second order effects. A truck cab model exposed to a pendulum impact load is used as an evaluation of this method, and the important variables and their influence on the response are identified. The effect of including results from forming simulations is also evaluated using the truck cab model. Variations are introduced before forming simulations, thereby taking forming effects into account in the sensitivity analysis. The method was found to be a good tool to identify important dispersion variables and to give an approximate result of the total dispersion, all with a reasonable amount of simulations.

Place, publisher, year, edition, pages
Taylor & Francis , 2009. Vol. 14, no 2, 111-124 p.
Keyword [en]
Monte Carlo, meta model, robust design, response surface method, sensitivity analysis, robustness
National Category
Applied Mechanics
Identifiers
URN: urn:nbn:se:liu:diva-15474DOI: 10.1080/13588260802412992OAI: oai:DiVA.org:liu-15474DiVA: diva2:115638
Projects
ROBDES
Note
On the day of the defence date the status of this article was: Accepted.Available from: 2008-11-11 Created: 2008-11-11 Last updated: 2011-09-19Bibliographically approved
In thesis
1. Robust design: Accounting for uncertainties in engineering
Open this publication in new window or tab >>Robust design: Accounting for uncertainties in engineering
2008 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis concerns optimization of structures considering various uncertainties. The overall objective is to find methods to create solutions that are optimal both in the sense of handling the typical load case and minimising the variability of the response, i.e. robust optimal designs.

Traditionally optimized structures may show a tendency of being sensitive to small perturbations in the design or loading conditions, which of course are inevitable. To create robust designs, it is necessary to account for all conceivable variations (or at least the influencing ones) in the design process.

The thesis is divided in two parts. The first part serves as a theoretical background to the second part, the two appended articles. This first part includes the concept of robust design, basic statistics, optimization theory and meta modelling.

The first appended paper is an application of existing methods on a large industrial example problem. A sensitivity analysis is performed on a Scania truck cab subjected to impact loading in order to identify the most influencing variables on the crash responses.

The second paper presents a new method that may be used in robust optimizations, that is, optimizations that account for variations and uncertainties. The method is demonstrated on both an analytical example and a Finite Element example of an aluminium extrusion subjected to axial crushing.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2008. 34 p.
Series
Linköping Studies in Science and Technology. Thesis, ISSN 0280-7971 ; 1389
Keyword
Robust optimisation, robust design, robustness, meta model, sensitivity analysis
National Category
Applied Mechanics
Identifiers
urn:nbn:se:liu:diva-15479 (URN)LIU–TEK–LIC–2008:47 (Local ID)978-91-7393-743-6 (ISBN)LIU–TEK–LIC–2008:47 (Archive number)LIU–TEK–LIC–2008:47 (OAI)
Presentation
ACAS, Campus Valla, Linköpings Universitet, Linköping (Swedish)
Opponent
Supervisors
Projects
ROBDES
Available from: 2009-04-03 Created: 2008-11-11 Last updated: 2009-05-07Bibliographically approved
2. Optimization and robustness of structural product families
Open this publication in new window or tab >>Optimization and robustness of structural product families
2009 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis concerns structural optimization of product families and robustness. The overall objective is to find a method for performing structural optimization of product families subjected to multiple crash load cases and to ensure a robust behavior.

A product family is a family of products where every product variant, or family member, shares at least one component with at least one other product in the family. Structural optimization of such a family is complex and for expensive function evaluations, e.g. crash simulations, the computing time to solve the problem with traditional methods gets unrealistically long. Therefore, a new optimization algorithm for product families is presented, called the critical constraint method (CCM), that reduces the number of required evaluations by only considering the active constraints in the optimal solution.

Traditionally optimized structures have a tendency of being sensitive to small variations in the design or loading conditions. As these kind of variations are inevitable, it is important to account for this sensitivity in the design process to ensure the robustness of the optimized design.

The thesis is divided in two parts. The first part serves as a theoretical background to the second part, the two appended articles. This first part includes introductions to the concepts of product families, optimization, meta modeling and robust design.

The first appended paper presents a new optimization algorithm for product families subjected to multiple crash loads. The method is compared to traditional methods and tested on two smaller product family examples.

The second paper is an application of an existing sensitivity analysis method on a large industrial application example. A sensitivity analysis is performed on a Scania truck cab subjected to an impact load in order to identify the most  influencing variables on the crash responses.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2009. 50 p.
Series
Linköping Studies in Science and Technology. Thesis, ISSN 0280-7971 ; 1403
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-17947 (URN)LIU-TEK-LIC-2009:11 (Local ID)978-91-7393-626-2 (ISBN)LIU-TEK-LIC-2009:11 (Archive number)LIU-TEK-LIC-2009:11 (OAI)
Presentation
2009-06-10, A-huset, Campus Valla, Linköpings universitet, Linköping, 10:00 (English)
Opponent
Supervisors
Available from: 2009-10-16 Created: 2009-04-27 Last updated: 2013-10-24Bibliographically approved
3. Robust optimisation of structures: Evaluation and incorporation of variations in simulation based design
Open this publication in new window or tab >>Robust optimisation of structures: Evaluation and incorporation of variations in simulation based design
2011 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis concerns the robustness of structures considering various uncertainties. The overall objective is to evaluate and develop simulation based design methods in order to find solutions that are optimal both in the sense of handling typical load cases and minimising the variability of the response, i.e. robust optimal designs. Conventionally optimised structures may show a tendency of being sensitive to small perturbations in the design or loading conditions. These variations are of course inevitable. To create robust designs, it is necessary to account for all conceivable variations (or at least the influencing ones) in the design process. The thesis is divided into two parts. The first part serves as a theoretical background for this work. It includes introductions to the concept of robust design, basic statistics, optimisation theory and metamodelling. The second part consists of five appended papers on the topic.

The first and third papers focuse on the evaluation of robustness, given some dispersions in the input data. Established existing methods are applied, and for paper three, comparisons with experimentally evaluated dispersions on a larger system are made.

The second and fourth paper introduce two new approaches to perform robust optimisation, i.e. optimisations where the mean performance and the robustness in the objectives are simultaneously optimised. These methods are demonstrated both on an analytical example and on a Finite Element model design example. The fifth paper studies the variations in mechanical properties between several different batches of the same steel grade. A material model is fitted to each batch of material, whereby dispersions seen in test specimens are transferred to material model parameter variations. The correlations between both test and material model parameters are studied.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2011. 39 p.
Series
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 1382
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-70199 (URN)978-91-7393-129-8 (ISBN)
Public defence
2011-09-23, C3, Hus C, Campus Valla, Linköpings universitet, Linköping, 10:15 (Swedish)
Opponent
Supervisors
Available from: 2011-08-24 Created: 2011-08-24 Last updated: 2011-09-07Bibliographically approved
4. Optimization and Robustness of Structural Product Families
Open this publication in new window or tab >>Optimization and Robustness of Structural Product Families
2011 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis concerns structural optimization and robustness evaluations, and new methods are presented that considerably reduce the computational cost of these evaluations.

Optimization is an effective tool in the design process and the interest from industry of its usage is quickly increasing. However, the usage would probably have grown faster if the required number of computationally costly finite element analyses could be reduced. Especially in the case of product family optimization, the problem size can easily get too large to be solved within a reasonable time. This is sometimes also true for robustness evaluations. To enable the usage of optimization and robustness evaluations also for large scale industrial problems, two new methods are here presented, which require a considerably smaller number of finite element analyses.

The first method concerns structural optimization of product families subjected to multiple crash load cases. Here, the number of required finite element analyses are considerably reduced by only considering the critical constraint in each iteration step.

The second method is an approach to approximate the variable sensibility based on the distribution of internal energy in a structure. The method can be used to evaluate the relative robustness of different design proposals or for structural optimization. Since the method is independent of the number of parameters and design variables the computational cost of such evaluations is drastically reduced for computationally large problems.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2011. 50 p.
Series
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 1397
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-70372 (URN)978-91-7393-072-7 (ISBN)
Public defence
2011-10-18, Planck, Fysikhuset, Campus Valla, Linköpings universitet, Linköping, 10:15 (English)
Opponent
Supervisors
Available from: 2011-09-05 Created: 2011-09-05 Last updated: 2011-09-19Bibliographically approved

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Lönn, DavidÖman, MichaelNilsson, LarsgunnarSimonsson, Kjell

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