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Optimization of Vehicle Structures under Uncertainties
Linköping University, Department of Management and Engineering, Solid Mechanics. Linköping University, The Institute of Technology.
2014 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

New emission targets, increased safety requirements and competition in the global market have led the automotive industry to focus more on developing efficient, optimised vehicle structures. Consequently, the use of simulation-based design in vehicle engineering has increased significantly in recent years. Advancements in computational power and efficient algorithms have made the simulation-based design process faster and more efficient and also made it possible to include structural optimisation. However, optimised design using classical (deterministic) optimisation techniques might not achieve the desired performance in real life due to uncertainties in input parameters such as variation in material properties, geometrical parameters, loading conditions, etc. Consequently it is necessary to consider these variations in the optimisation process in order to create a robust and reliable design. However, the incorporation of uncertainties into the design optimisation of a full-scale vehicle model tends to be computationally expensive so approximation models have often been utilised to minimise  computational effort.

In this thesis, different approaches to evaluate robustness and to perform non-deterministic optimisation have been studied. Primary focus was on robust design and reliability-based optimisation methods. These methods were verified using a complex vehicle engineering application. The first part of the study involves evaluation of robustness analysis methods and a comparative study has been performed between FE-based robustness analysis and metamodel-based robustness analysis. Furthermore, different metamodelling techniques were also compared with respect to performance. An approach to handle the fracture risk factors using metamodels is also presented. In the second part of the study, an approach to perform multiobjective reliability-based optimisation and robust design optimisation is presented and verified using a vehicle side impact crashworthiness application. The importance of a non-deterministic optimisation approach as compared to a deterministic approach is illustrated by comparing the results from non-deterministic optimisation with those from deterministic optimisation. The approaches presented in the study were found to be suitable for applications related to vehicle structures.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2014. , 30 p.
Series
Linköping Studies in Science and Technology. Thesis, ISSN 0280-7971 ; 1643
Keyword [en]
Multiobjective optimisation; robustness analysis; robust design optimisation; reliability-based optimisation; crashworthiness; metamodel
National Category
Engineering and Technology
Identifiers
URN: urn:nbn:se:liu:diva-103692ISBN: 978-91-7519-420-2 (print)OAI: oai:DiVA.org:liu-103692DiVA: diva2:690298
Supervisors
Available from: 2014-01-23 Created: 2014-01-23 Last updated: 2014-01-23Bibliographically approved
List of papers
1. Robustness study of a hat profile beam made of boron steel subjected to three point bending
Open this publication in new window or tab >>Robustness study of a hat profile beam made of boron steel subjected to three point bending
2016 (English)In: International Journal of Vehicle Systems Modelling and Testing, ISSN 1745-6436, E-ISSN 1745-6444, no 3, 252-270 p.Article in journal (Refereed) Published
Abstract [en]

It is essential to account for variations in the manufacturing process and in loading conditions when improving the robustness and reliability of a product’s design. A finite element study of the robustness of a hat profile beam made from boron steel subjected to a three point bending load is presented, and an approach to incorporate the variations investigated is demonstrated. Fracture risk factors and the maximum deflection of the beam are the measured responses. Spatial variation of the sheet thickness is considered in the forming simulations, along with other input variations. Stress-strain relations from tensile tests have been used in the robustness analyses to represent the variation in material properties. Furthermore, validations of four metamodels have been performed. Both the responses measured were found to be sensitive to input variations. Separate metamodels were created for each risk prone zone in order to improve the performance of the metamodels for risk factor responses.

Place, publisher, year, edition, pages
Bucks: InderScience Publishers, 2016
Keyword
Robustness analysis; Monte Carlo analysis; metamodel; boron steel; fracture risk factor
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-103690 (URN)10.1504/IJVSMT.2016.080880 (DOI)
Available from: 2014-01-23 Created: 2014-01-23 Last updated: 2017-12-06Bibliographically approved
2. Multiobjective reliability-based and robust design optimisation for crashworthiness of a vehicle side impact
Open this publication in new window or tab >>Multiobjective reliability-based and robust design optimisation for crashworthiness of a vehicle side impact
2015 (English)In: International Journal of Vehicle Design, ISSN 0143-3369, E-ISSN 1741-5314, Vol. 67, no 4, 347-367 p.Article in journal (Refereed) Published
Abstract [en]

Optimisation of vehicle design is necessary to meet increased safety requirements, new emission regulations, and to deal with competition in the global market, etc. However, optimised design using classical optimisation techniques with deterministic models might not meet the desired performance level or might fail in extreme events in real life owing to uncertainties in the design parameters and loading conditions. Consequently, it is essential to account for uncertainties in a systematic manner to generate a robust and reliable design. In this paper, an approach to perform multiobjective, reliability-based, and robust design optimisation is presented using a vehicle side impact crashworthiness application. Metamodels have been used in the optimisation process to decrease computational effort. Variations in material properties, thicknesses, loading conditions, and B-pillar heat-affected zone material strength have been considered for the stochastic optimisation. A comparative study of deterministic, reliability-based, and robust optimisation approaches is performed.

Place, publisher, year, edition, pages
InderScience Publishers, 2015
Keyword
Multiobjective optimisation; robust optimisation; reliabilitybased optimisation; crashworthiness; Monte Carlo analysis; metamodel; boron steel; fracture risk factor
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-103691 (URN)10.1504/IJVD.2015.070410 (DOI)000359461500002 ()
Available from: 2014-01-23 Created: 2014-01-23 Last updated: 2017-12-06Bibliographically approved

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Shetty, Sandeep

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