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Effect of Austempering on Plastic Behavior of Some Austempered Ductile Iron Alloys
Jönköping University, School of Engineering, JTH. Research area Materials and manufacturing – Casting.ORCID iD: 0000-0003-2671-9825
Vestascastings Guldsmedshyttan AB.
Jönköping University, School of Engineering, JTH. Research area Materials and manufacturing – Casting.
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.

Place, publisher, year, edition, pages
2011. Vol. 42, no 13, 3999-4007 p.
Keyword [en]
Casting, Austempered Ductile Iron, ADI, plastic behavior
National Category
Metallurgy and Metallic Materials
Identifiers
URN: urn:nbn:se:hj:diva-16747DOI: 10.1007/s11661-011-0796-7OAI: oai:DiVA.org:hj-16747DiVA: diva2:457638
Available from: 2011-11-18 Created: 2011-11-18 Last updated: 2017-12-08Bibliographically approved
In thesis
1. Microstructure-based Mechanical Behaviour in Structural Analyses of Cast Components
Open this publication in new window or tab >>Microstructure-based Mechanical Behaviour in Structural Analyses of Cast Components
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
Component behaviour, Structural analysis, Mechanical behaviour, Casting process simulation, Finite element method simulation
National Category
Mechanical Engineering Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:hj:diva-19127 (URN)978-91-87289-01-9 (ISBN)
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
2. Simulation of Microstructure-based Mechanical Behaviour of Cast Components
Open this publication in new window or tab >>Simulation of Microstructure-based Mechanical Behaviour of Cast Components
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

In the process of developing cast iron and cast aluminium components, a high level of co-operation between product development and production is of great importance. From an engineering standpoint, this co-operation is limited early in the product development phase by e.g. a lack of established methods for the consideration of local variations in the mechanical behaviour of a finished component.

This thesis aims to increase the possibilities for co-operation between product development and production during the product realisation process by introducing and studying the use of predicted local mechanical behaviour in structural analyses of cast components. A literature review of existing simulation methods and a work on characterisation of mechanical behaviour from microstructural features have been performed to identify important knowledge gaps. A simulation strategy has been formulated which is able to predict local mechanical behaviour throughout the entire component, and to incorporate this into a Finite Element Method (FEM) simulation of the structural behaviour of the component. In the simulation strategy, componentspecific microstructure-based mechanical behaviour is predicted using a casting process simulation. A computer program was developed to create FEM material definitions which capture the local variations in mechanical behaviour throughout the component. Using a material reduction technique, the local mechanical behaviour can be incorporated without increasing the FEM simulation time.

The relevance of the simulation strategy was experimentally verified on cast aluminium samples, where the strain field was observed using Digital Image Correlation (DIC). It was found that the local variations in mechanical behaviour cause a stress-strain distribution that deviates from that predicted by a homogeneous material description, indicating the importance of calculating with and including such variations in material behaviour in FEM simulations. Numerical investigations demonstrate the strategy’s relevance for predicting the behaviour of cast aluminium and ductile iron components.

Place, publisher, year, edition, pages
School of Engineering, Jönköping University, 2014. 51 p.
Series
JTH Dissertation Series, 3
Keyword
Component behaviour, structural analysis, mechanical behaviour, casting process simulation, Finite Element Method (FEM) simulation
National Category
Metallurgy and Metallic Materials Applied Mechanics
Identifiers
urn:nbn:se:hj:diva-23695 (URN)978-91-87289-04-0 (ISBN)
Public defence
2014-05-09, E1405, Tekniska Högskolan, Gjuterigatan 5, Jönköping, 10:00 (English)
Opponent
Supervisors
Available from: 2014-04-14 Created: 2014-04-11 Last updated: 2014-04-14Bibliographically approved

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Olofsson, JakobSvensson, Ingvar L.
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