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Article
Publication date: 1 February 1986

H. Burlet and G. Cailletaud

A formulation of non‐linear kinematic hardening in plasticity is given, with a short description of the model properties under cyclic loading. A resolution algorithm based…

Abstract

A formulation of non‐linear kinematic hardening in plasticity is given, with a short description of the model properties under cyclic loading. A resolution algorithm based on the initial stress method is implemented in a two‐dimensional finite element code (ZEBULON). The procedure is tested on examples including mechanical and thermal loading. Some remarks are made on the maximum increment size, the relative efficiency of ‘radial return’ and ‘secant stiffness method’ is discussed. Finally, the possibilities of the model concerning ratchetting, cyclic hardening and softening are shown.

Details

Engineering Computations, vol. 3 no. 2
Type: Research Article
ISSN: 0264-4401

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Article
Publication date: 27 September 2011

Mohammad Rezaiee‐Pajand, Cyrus Nasirai and Mehrzad Sharifian

The purpose of this paper is to present a new effective integration method for cyclic plasticity models.

Abstract

Purpose

The purpose of this paper is to present a new effective integration method for cyclic plasticity models.

Design/methodology/approach

By defining an integrating factor and an augmented stress vector, the system of differential equations of the constitutive model is converted into a nonlinear dynamical system, which could be solved by an exponential map algorithm.

Findings

The numerical tests show the robustness and high efficiency of the proposed integration scheme.

Research limitations/implications

The von‐Mises yield criterion in the regime of small deformation is assumed. In addition, the model obeys a general nonlinear kinematic hardening and an exponential isotropic hardening.

Practical implications

Integrating the constitutive equations in order to update the material state is one of the most important steps in a nonlinear finite element analysis. The accuracy of the integration method could directly influence the result of the elastoplastic analyses.

Originality/value

The paper deals with integrating the constitutive equations in a nonlinear finite element analysis. This subject could be interesting for the academy as well as industry. The proposed exponential‐based integration method is more efficient than the classical strategies.

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Article
Publication date: 1 March 1989

Eddy Pramono and Kaspar Willam

Numerical solutions in computational plasticity are severely challenged when concrete and geomaterials are considered with non‐regular yield surfaces, strain‐softening and…

Abstract

Numerical solutions in computational plasticity are severely challenged when concrete and geomaterials are considered with non‐regular yield surfaces, strain‐softening and non‐associated flow. There are two aspects that are of immediate concern within load steps which are truly finite: first, the iterative corrector must assure that the equilibrium stress state and the plastic process variables do satisfy multiple yield conditions with corners, Fi(σ, q) = 0, at discrete stages of the solution process. To this end, a reliable return mapping algorithm is required which minimizes the error of the plastic return step. Second, the solution of non‐linear equations of motion on the global structural level must account for limit points and premature bifurcation of the equilibrium path. The current paper is mainly concerned with the implicit integration of elasto‐plastic hardening/softening relations considering non‐associated flow and the presence of composite yield conditions with corners.

Details

Engineering Computations, vol. 6 no. 3
Type: Research Article
ISSN: 0264-4401

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Article
Publication date: 1 April 1989

Eduardo N. Dvorkin, Alberto M. Cuitiño and Gustavo Gioia

A concrete material model is presented. The model is based on non‐associated plasticity for the pre‐failure and ductile post‐failure regimes and fracture (smeared crack…

Abstract

A concrete material model is presented. The model is based on non‐associated plasticity for the pre‐failure and ductile post‐failure regimes and fracture (smeared crack approach) for the brittle post‐failure regime. The implementation of the constitutive model in the 2‐D elements of a general purpose non‐linear incremental finite element code is discussed. Some important numerical features of the implementation are the implicit integration of the stress/strain relation and the use of an efficient symmetric stiffness formulation for the equilibrium iterations.

Details

Engineering Computations, vol. 6 no. 4
Type: Research Article
ISSN: 0264-4401

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Article
Publication date: 5 March 2018

Dylan Agius, Mladenko Kajtaz, Kyriakos I. Kourousis, Chris Wallbrink and Weiping Hu

This study presents the improvements of the multicomponent Armstrong–Frederick model with multiplier (MAFM) performance through a numerical optimisation methodology…

Abstract

Purpose

This study presents the improvements of the multicomponent Armstrong–Frederick model with multiplier (MAFM) performance through a numerical optimisation methodology available in a commercial software. Moreover, this study explores the application of a multiobjective optimisation technique for the determination of the parameters of the constitutive models using uniaxial experimental data gathered from aluminium alloy 7075-T6 specimens. This approach aims to improve the overall accuracy of stress–strain response, for not only symmetric strain-controlled loading but also asymmetrically strain- and stress-controlled loading.

Design/methodology/approach

Experimental data from stress- and strain-controlled symmetric and asymmetric cyclic loadings have been used for this purpose. The analysis of the influence of the parameters on simulation accuracy has led to an adjustment scheme that can be used for focused optimisation of the MAFM model performance. The method was successfully used to provide a better understanding of the influence of each model parameter on the overall simulation accuracy.

Findings

The optimisation identified an important issue associated with competing ratcheting and mean stress relaxation objectives, highlighting the issues with arriving at a parameter set that can simulate ratcheting and mean stress relaxation for load cases not reaching at complete relaxation.

Practical implications

The study uses a strain-life fatigue application to demonstrate the importance of incorporating a technique such as the presented multiobjective optimisation method to arrive at robust parameters capable of accurately simulating a variety of transient cyclic phenomena.

Originality/value

The proposed methodology improves the accuracy of cyclic plasticity phenomena and strain-life fatigue simulations for engineering applications. This study is considered a valuable contribution for the engineering community, as it can act as starting point for further exploration of the benefits that can be obtained through material parameter optimisation methodologies for models of the MAFM class.

Details

Aircraft Engineering and Aerospace Technology, vol. 90 no. 2
Type: Research Article
ISSN: 1748-8842

Keywords

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Article
Publication date: 6 July 2015

Sanka Dilshan Ekanayake, D.S. Liyanapathirana and Chin Jian Leo

EPS geofoam has been widely used in embankment construction, slope stabilisation, retaining walls, bridge approaches and abutments. Nevertheless, the potential of EPS…

Abstract

Purpose

EPS geofoam has been widely used in embankment construction, slope stabilisation, retaining walls, bridge approaches and abutments. Nevertheless, the potential of EPS geofoam as an engineering material in geotechnical applications has not been fully realised yet. The purpose of this paper is to present the finite element formulation of a constitutive model based on the hardening plasticity, which has the ability to simulate short-term behaviour of EPS geofoam, to predict the mechanical behaviour of EPS geofoam and it is implemented in the finite element programme ABAQUS.

Design/methodology/approach

Finite element formulation is presented based on the explicit integration scheme.

Findings

The finite element formulation is verified using triaxial test data found in the literature (Wong and Leo, 2006 and Chun et al., 2004) for two varieties of EPS geofoam. Performance of the constitute model is compared with four other models found in the literature and results confirm that the constitutive model used in this study has the ability to simulate the short-term EPS geofoam behaviour with sufficient accuracy.

Research limitations/implications

This research is focused only on the short-term behaviour of EPS geofoam. Experimental studies will be carried out in future to incorporate effects of temperature and creep on the material behaviour.

Practical implications

This formulation will be applicable to finite element analysis of boundary value problems involving EPS geofoam (e.g. application of EPS geofoam in ground vibration isolation, retaining structures as compressible inclusions and stabilisation of slopes).

Originality/value

Finite element analysis of EPS geofoam applications are available in the literature using elastic perfectly plastic constitutive models. However, this is the first paper presenting a finite element application utilising a constitutive model specifically developed for EPS geofoam.

Details

Engineering Computations, vol. 32 no. 5
Type: Research Article
ISSN: 0264-4401

Keywords

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Article
Publication date: 1 March 1995

S. Oller, S. Botello, J. Miquel and E. Oñate

This paper shows a generalization of the classic isotropic plasticitytheory to be applied to orthotropic or anisotropic materials. This approachassumes the existence of a…

Abstract

This paper shows a generalization of the classic isotropic plasticity theory to be applied to orthotropic or anisotropic materials. This approach assumes the existence of a real anisotropic space, and other fictitious isotropic space where a mapped fictitious problem is solved. Both spaces are related by means of a linear transformation using a fourth order transformation tensor that contains all the information concerning the real anisotropic material. The paper describes the basis of the spaces transformation proposed and the expressions of the resulting secant and tangent constitutive equations. Also details of the numerical integration of the constitutive equation are provided. Examples of application showing the good performance of the model for analysis of orthotropic materials and fibre‐reinforced composites are given.

Details

Engineering Computations, vol. 12 no. 3
Type: Research Article
ISSN: 0264-4401

Keywords

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Article
Publication date: 1 May 2003

A.R. Khoei, A. Bakhshiani and M. Mofid

In this paper, a new rate type endochronic constitutive model is introduced to describe deformations in the finite strain range. A new material dependent objective rate of…

Abstract

In this paper, a new rate type endochronic constitutive model is introduced to describe deformations in the finite strain range. A new material dependent objective rate of Cauchy stress is suggested based on the general form of spin tensors, defining objective stress rates. The endochronic constitutive equations are extended using the concept of corotational stress rates and additive decomposition of deformation rate. The constitutive relations are specialized for thin‐walled tubes under torsion and a procedure for solving the ordinary differential equations for cases of simple and pure torsion is developed. The axial effects for various materials, subjected to simple and pure torsion, are simulated and compared with experimental data. The results clearly indicate that the new combined rate endochronic model can be effectively used to describe the behavior of material in the finite strain range.

Details

Engineering Computations, vol. 20 no. 3
Type: Research Article
ISSN: 0264-4401

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Article
Publication date: 19 March 2020

Fauziana Lamin, Ahmad Kamal Ariffin Mohd Ihsan, Intan Fadhlina Mohamed and Cheeranan Krutsuwan Nuphairode

This paper aims to evaluate the validity of bilinear hardening model to represent the stress flow of high-pressure torsion (HPT)-strengthened lightweight material, AA2024.

Abstract

Purpose

This paper aims to evaluate the validity of bilinear hardening model to represent the stress flow of high-pressure torsion (HPT)-strengthened lightweight material, AA2024.

Design/methodology/approach

Finite-element HPT simulation was performed by applying a simultaneous prescribed displacement on the axial and rotational axis that is equivalent to 4 GPa pressure and 30° torsion. The material behaviour incorporates plasticity attributes with a bilinear constitutive equation that consists of elastic and tangent modulus.

Findings

As a result, the von Mises stress generated from the simulation is in good agreement with the experiment, indicating that the assumptions of plasticity properties applied for the FEM simulation model are acceptable. The model verification confirms the anticipated plasticity parameters’ effect on the generated von Mises stress. The disc centre also evidenced an insignificant stress increment due to the limited shear straining.

Research limitations/implications

A reliable hardening model would assist in understanding the stress flow associated with mechanical properties enhancement.

Practical implications

The bilinear hardening model exhibits a satisfactory stress estimation. It simplifies the ideal strain variable hardening procedures and lessens the total computation time that is valuable in solving severe plastic deformation problems.

Originality/value

An integration of well-defined input parameters, concerning the hardening behaviour and the plasticity properties, contributes to the establishment of a validated HPT simulation model, particularly for AA2024. This study also proved that perfectly plastic behaviour is inappropriate to represent hardening in the HPT-strengthened materials due to the remarkable stress deviation from the experimental data.

Details

International Journal of Structural Integrity, vol. 11 no. 4
Type: Research Article
ISSN: 1757-9864

Keywords

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Article
Publication date: 4 July 2016

Chuan Liu, Ying Luo, Min Yang and Qiang Fu

The purpose of this paper is to clarify the effect of material hardening model and lump-pass method on the thermal-elastic-plastic (TEP) finite element (FE) simulation of…

Abstract

Purpose

The purpose of this paper is to clarify the effect of material hardening model and lump-pass method on the thermal-elastic-plastic (TEP) finite element (FE) simulation of residual stress induced by multi-pass welding of materials with cyclic plasticity.

Design/methodology/approach

Nickel-base alloy and stainless steel, which are used in J-type weld for manufacturing the nuclear reactor pressure head, can easily harden during multi-pass welding. The J-weld welding experiment is carried out and the temperature cycle and residual stress are measured to validate the TEP simulation. Thermal-mechanical sequence coupling method is employed to get the welding residual stress. The lumped-pass model and pass-by-pass FE model are built and two materials hardening models, kinematic hardening model and mixed hardening model, are adopted during the simulations. The effects of material hardening models and lumped-pass method on the residual stress in J-weld are distinguished.

Findings

Based on the kinematic hardening model, the stresses simulated with the lumped-pass FE model are almost consistent with those obtained by the pass-by-pass FE model; while with the mixed hardening material model, the lumped-pass method has great effect on the simulated stress.

Practical implications

A computation with mixed isotropic-kinematic material seems not to be the appropriate solution when using the lumped-pass method to save the computation time.

Originality/value

In the simulation of multi-pass welding residual stress involved in materials with cyclic plasticity, the material hardening model should be carefully considered. The kinematic hardening model with lump-pass FE model can be used to get better simulation results with less computation time. The results give a direction for welding residual stress simulation for the large structure such as the reactor pressure vessel.

Details

Engineering Computations, vol. 33 no. 5
Type: Research Article
ISSN: 0264-4401

Keywords

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