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Microstructure-based Mechanical Behaviour in Structural Analyses of Cast Components
Jönköping University, School of Engineering, JTH. Research area Materials and manufacturing – Casting.ORCID iD: 0000-0003-2671-9825
2012 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

In the process of developing cast iron and cast aluminium components, the co-operation between product development and production is important. On the engineering level, this co-operation is limited already in the product development phase e.g. by the lack of established methods to consider the mechanical behaviour of the completed component.

This thesis aims to increase the possibilities for co-operation in the product realisation process between product development and production by enabling the use of predicted local mechanical behaviour in structural analyses of cast components. A literature review on existing simulation methods and a work on characterization of mechanical behaviour from microstructural features are performed to identify important knowledge gaps. A simulation strategy is formulated that is able to predict local mechanical behaviour throughout the entire component and incorporate the behaviour into a Finite Element Method (FEM) simulation of the structural behaviour of the component. In the simulation strategy, the component specific microstructure-based mechanical behaviour is predicted using a casting process simulation. A computer program is developed to create FEM material definitions that capture the local variations in mechanical behaviour throughout the component.

The relevance of the simulation strategy is demonstrated for a ductile iron component. It is found that the local variations in mechanical behaviour result in a stress-strain distribution in the component that a homogeneous material description fails to express. Residual stresses affect the mechanical behaviour at low loads. At higher loads, however, the accuracy of the simulation is determined by the local variations in mechanical behaviour. Using a material reduction technique, the local mechanical behaviour can be incorporated without increasing the FEM simulation time. 

Place, publisher, year, edition, pages
Jönköping: School of Engineering, Jönköping University , 2012. , 42 p.
Series
JTH Dissertation Series, 1
Keyword [en]
Component behaviour, Structural analysis, Mechanical behaviour, Casting process simulation, Finite element method simulation
National Category
Mechanical Engineering Metallurgy and Metallic Materials
Identifiers
URN: urn:nbn:se:hj:diva-19127ISBN: 978-91-87289-01-9 (print)OAI: oai:DiVA.org:hj-19127DiVA: diva2:543691
Presentation
2012-08-31, Jönköpings Tekniska Högskola, E1405 Gjuterisalen, Gjuterigatan 5, Jönköping, 10:00 (Swedish)
Opponent
Supervisors
Available from: 2012-08-09 Created: 2012-08-08 Last updated: 2016-01-18Bibliographically approved
List of papers
1. Simulation of mechanical behaviour of cast aluminium components
Open this publication in new window or tab >>Simulation of mechanical behaviour of cast aluminium components
2012 (English)In: International Journal of Cast Metals Research, ISSN 1364-0461, E-ISSN 1743-1336, Vol. 25, no 6, 319-327 p.Article, review/survey (Refereed) Published
Abstract [en]

A literature review on methods to consider the mechanical behaviour of cast aluminium alloys in finite element method (FEM) simulations of cast aluminium components has been performed. The mechanical behaviour is related to several microstructural parameters achieved during the casting process. Three different methods to consider these microstructural parameters are introduced. One method predicts the mechanical behaviour of the component using casting process simulation software. The other two methods implement numerical models for the mechanical behaviour of cast aluminium into the FEM simulation. Applications of the methods are shown, including combinations with statistical methods and geometry optimisation methods. The methods are compared, and their different strengths and drawbacks are discussed.

National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:hj:diva-19105 (URN)
Available from: 2012-08-06 Created: 2012-08-06 Last updated: 2017-12-07Bibliographically approved
2. Effect of Austempering on Plastic Behavior of Some Austempered Ductile Iron Alloys
Open this publication in new window or tab >>Effect of Austempering on Plastic Behavior of Some Austempered Ductile Iron Alloys
2011 (English)In: Metallurgical and Materials Transactions. A, ISSN 1073-5623, E-ISSN 1543-1940, Vol. 42, no 13, 3999-4007 p.Article in journal (Refereed) Published
Abstract [en]

A numerical description relating microstructure to elastic and plastic deformation behavior would make it possible to simulate the mechanical behavior of complex cast components with tailored material properties. Limited work and data have however been published regarding the connection between microstructure and plastic behavior of austempered ductile irons (ADI). In the current work the effects of austempering temperature and austempering time on the strength coefficient and the strain hardening exponent of the Hollomon equation have been investigated for two ADI alloys. The results show that the plastic behavior is highly dependent on the combination of austempering temperature and austempering time. It was found that as the austempering temperature increases both the strength coefficient and the strain hardening exponent initially decrease, but after reaching a minimum at the critical austempering temperature they show a plateau or an increase. The effect of the austempering time on the plastic behavior depends on the austempering temperature. At low austempering temperatures the strength coefficient and the strain hardening exponent decrease with increased austempering time, whereas at higher austempering temperatures they show little time dependence. These relations are explained by the microstructural transformations that take place during the austempering heat treatment.

Keyword
Casting, Austempered Ductile Iron, ADI, plastic behavior
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:hj:diva-16747 (URN)10.1007/s11661-011-0796-7 (DOI)
Available from: 2011-11-18 Created: 2011-11-18 Last updated: 2017-12-08Bibliographically approved
3. Incorporating predicted local mechanical behaviour of cast components into finite element simulations
Open this publication in new window or tab >>Incorporating predicted local mechanical behaviour of cast components into finite element simulations
2012 (English)In: Materials & Design, ISSN 0261-3069, Vol. 34, 494-500 p.Article in journal (Refereed) Published
Abstract [en]

A software which enables the incorporation of local variations in both elastic and plastic mechanical behaviour predicted by a casting process simulation into a Finite Element Method (FEM) simulation is presented. The software uses a piecewise linearization of the Hollomon or the Ludwigson equation to characterise plastic mechanical behaviour of the material on an element level throughout a component. The accuracy obtained in the linearization is investigated, and the performance of the software is studied using different input parameters. The applicability of the software is verified and demonstrated on a ductile iron component, and a simulation strategy for cast components denoted a closed chain of simulations for cast components is discussed.

Keyword
Casting, Mechanical, Plastic behaviour
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:hj:diva-16743 (URN)10.1016/j.matdes.2011.08.029 (DOI)
Available from: 2011-11-18 Created: 2011-11-18 Last updated: 2017-08-14Bibliographically approved
4. Casting and stress-strain simulations of a cast ductile iron component using microstructure based mechanical behavior
Open this publication in new window or tab >>Casting and stress-strain simulations of a cast ductile iron component using microstructure based mechanical behavior
2012 (English)In: IOP Conference Series: Materials Science and Engineering, Volume 33: MCWASP XIII: International Conference on Modeling of Casting, Welding and Advanced Solidification Processes / [ed] Andreas Ludwig, Menghuai Wu and Abdellah Kharicha, London: IOP Publishing , 2012Conference paper, Published paper (Refereed)
Abstract [en]

The industrial demand for increased component performance with concurrent reductions in component weight, development times and verifications using physical prototypes drives the need to use the full potential of casting and Finite Element Method (FEM) simulations to correctly predict the mechanical behavior of cast components in service. The mechanical behavior of the component is determined by the casting process, and factors as component geometry and casting process parameters are known to affect solidification and microstructure formation throughout the component and cause local variations in mechanical behavior as well as residual stresses. Though residual stresses are known to be an important factor in the mechanical behavior of the component, the importance of local mechanical behavior is not well established and the material is typically considered homogeneous throughout the component. This paper deals with the influence of solidification and solid state transformation on microstructure formation and the effect of local microstructure variations on the mechanical behavior of the cast component in service. The current work aims to investigate the coupling between simulation of solidification, microstructure and local variations in mechanical behavior and stress-strain simulation. This is done by performing several simulations of a ductile iron component using a recently developed simulation strategy, a closed chain of simulations for cast components, able to predict and describe the local variations in not only elastic but also plastic behavior throughout the component by using microstructural parameters determined by simulations of microstructural evolution in the component during the casting process. In addition the residual stresses are considered. The results show that the FEM simulation results are significantly affected by including microstructure based mechanical behavior. When the applied load is low and the component is subjected to stress levels well below the yield strength of the material, the residual stresses highly affects the simulation results while the effect of local material behavior is low. As the applied load increases and the stress level in the component approaches and passes the yield strength, the effect of residual stresses diminishes while the effect of local mechanical behavior increases. In particular the predicted strain level is heavily affected by the use of local mechanical behavior. It is proposed that it is important to include both local mechanical behavior and residual stresses in stress-strain simulations to predict the true mechanical behavior of the component.

Place, publisher, year, edition, pages
London: IOP Publishing, 2012
Series
IOP Conference Series, ISSN 1757-8981 ; 33
Keyword
Casting, Component behaviour, Ductile iron, Mechanical behaviour, Plastic behaviour
National Category
Metallurgy and Metallic Materials Mechanical Engineering
Identifiers
urn:nbn:se:hj:diva-19107 (URN)10.1088/1757-899X/33/1/012051 (DOI)
Conference
MCWASP XIII: International Conference on Modeling of Casting, Welding and Advanced Solidification Processes, Schladming, Austria, 17-22, June 2012
Projects
CompCAST
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xAvailable from: 2012-08-06 Created: 2012-08-06 Last updated: 2017-08-14Bibliographically approved
5. The effects of local variations in mechanical behaviour – Numerical investigation of a ductile iron component
Open this publication in new window or tab >>The effects of local variations in mechanical behaviour – Numerical investigation of a ductile iron component
2012 (English)In: Materials & design, ISSN 0264-1275, E-ISSN 1873-4197, Vol. 43, 264-271 p.Article in journal (Refereed) Published
Abstract [en]

The effects of incorporating local mechanical behaviour into a structural analysis of a cast ductile iron component are investigated. A recently presented simulation strategy, the closed chain of simulations for cast components, is applied to incorporate local behaviour predicted by a casting process simulation into a Finite Element Method (FEM) structural analysis, and the effects of the strategy on predicted component behaviour and simulation time are evaluated. The results are compared to using a homogeneous material description. A material reduction method is investigated, and the effects of material reduction and number of linearization points are evaluated.

The results show that local mechanical behaviour may significantly affect the predicted behaviour of the component, and a homogeneous material description fails to express the stress-strain distribution caused by the local variations in mechanical behaviour in the component. The material reduction method is able to accurately describe this effect while only slightly increasing the simulation time. It is proposed that local variations in mechanical behaviour are important to consider in structural analyses of the mechanical behaviour of ductile iron components.

Keyword
Casting, Component behaviour, Ductile iron, Mechanical behaviour, Plastic behaviour
National Category
Mechanical Engineering Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:hj:diva-19110 (URN)10.1016/j.matdes.2012.07.006 (DOI)
Projects
CompCAST
Available from: 2012-08-06 Created: 2012-08-06 Last updated: 2017-12-07Bibliographically approved

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