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This study aims to explain the characterization of cyclic behavior of a tube made of functionally graded material (FGM) under different combinations of internal pressure and cyclic through-thickness temperature gradients.

The normality rule, nonlinear kinematic hardening Chaboche model and Von Mises yield criterion were used to model the constitutive behavior of an FG tube in the incremental form. The material properties and hardening parameters of the Chaboche model vary according to the power-law function in the radial direction. The backward Euler integration scheme combined with return mapping algorithm which relies on the solution of a nonlinear equation performs the numerical procedure. The algorithm is implemented within the user subroutine UMAT in ABAQUS/standard.

The published works on FG components considering only the mechanical and physical properties as a function of spatial coordinate and nonlinear kinematic hardening parameters have not been considered to be changed continuously from one surface to another. Motivated by this, the present paper has deliberately been targeted to tackle this kind of problem to simulate the cyclic behavior of an FG tube as accurately as possible. In addition, to classify various behaviors the FG tube under cyclic thermomechanical loadings, Bree’s interaction diagram as an essential tool in designing of the FG pressure vessels in many engineering sectors is presented.

Provides a detailed description of the FG parameters of Chaboche kinematic hardening parameters in the adopted constitutive equations. In this paper, the significant effects of internal pressure values, kinematic hardening models and also FG inhomogeneity index related to the hardening rule parameters on plastic deformation of the FG tube are illustrated. Finally, the various cyclic behaviors of the FG tube under different combinations of thermomechanical loading are fully explored.

The purpose of this paper is to highlight the performance of the Chaboche model in relation to the database identification, tests with imposed deformations were conducted at room temperature on 304L stainless steel specimens.

The first two tests were performed in tension-compression between ±0.005 and ±0.01; in the third test, each cycle is composed of the combination of a compression tensile cycle between ±0.01 followed by a torsion cycle between ±0.01723 (non-proportional path), and the last, uniaxial ratcheting test with a mean stress between 250 MPa and −150 MPa. Several identifications of a Chaboche-type model were then performed by considering databases composed of one or more of the cited tests. On the basis of these identifications, the simulations of a large number of ratchet tests in particular were carried out.

The results present the effect of the optimized parameters on the prediction of the behavior of materials which is reported in the graphs, Optimizations 1 and 2 of first and second tests and Optimization 4 of the third test giving a good prediction of the increasing/decreasing pre-deformation amplitude.

The quality of the model's predictions strongly depends on the richness of the database used for the identification of the parameters.

The purpose of this paper is to suggest an implicit integration method for updating the constitutive relationships in the newly proposed anisotropic egg-shaped elastoplastic (AESE) model and to apply it in ABAQUS.

The implicit integration algorithm based on the Newton–Raphson method and the closest point projection scheme containing an elastic predictor and plastic corrector are implemented in the AESE model. Then, the integration code for this model is incorporated into the commercial finite element software ABAQUS through the user material subroutine (UMAT) interface to simulate undrained monotonic triaxial tests for various saturated soft clays under different consolidation conditions.

The comparison between the simulated results from ABAQUS and the experimental results demonstrates the satisfactory performance of this implicit integration algorithm in terms of effectiveness and robustness and the ability of the proposed model to predict the characteristics of soft clay.

The rotational hardening rule in the AESE model together with the implicit integration algorithm cannot be considered.

The singularity problem existing in most elastoplastic models is eliminated by the closed, smooth and flexible anisotropic egg-shaped yield surface form in the AESE model. In addition, this notion leads to an efficient implicit integration algorithm for updating the highly nonlinear constitutive equations for unsaturated soft clay.

The feasibility of advanced viscoplastic models for non‐linear boundary element analysis of metallic structural components with dependence on thermomechanical history is investigated. Several numerical examples are presented using the boundary element implementation of two different internal state variable viscoplastic models to the solution of time‐dependent inelastic problems arising in creeping metallic structural components under the combined action of high temperature loading gradients and quasi‐static mechanical loading conditions. To demonstrate the efficiency of the implemented viscoplastic models, the results obtained using the direct boundary element methodology are compared with those obtained by both analytical and finite element solution as well as, for different numerical results of plane strain thermoviscoplastic deformation problems under general thermomechanical loading.

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.

The purpose of this paper is to examine the mechanical behaviour of additively manufactured Ti-6Al-4V under cyclic loading. Using as-built selective laser melting (SLM) Ti-6Al-4V in engineering applications requires a detailed understanding of its elastoplastic behaviour. This preliminary study intends to create a better understanding on the cyclic plasticity phenomena exhibited by this material under symmetric and asymmetric strain-controlled cyclic loading.

This paper investigates experimentally the cyclic elastoplastic behaviour of as-built SLM Ti-6Al-4V under symmetric and asymmetric strain-controlled loading histories and compares it to that of wrought Ti-6Al-4V. Moreover, a plasticity model has been customised to simulate effectively the mechanical behaviour of the as-built SLM Ti-6Al-4V. This model is formulated to account for the SLM Ti-6Al-4V-specific characteristics, under the strain-controlled experiments.

The elastoplastic behaviour of the as-built SLM Ti-6Al-4V has been compared to that of the wrought material, enabling characterisation of the cyclic transient phenomena under symmetric and asymmetric strain-controlled loadings. The test results have identified a difference in the strain-controlled cyclic phenomena in the as-build SLM Ti-6Al-4V when compared to its wrought counterpart, because of a difference in their microstructure. The plasticity model offers accurate simulation of the observed experimental behaviour in the SLM material.

Further investigation through a more extensive test campaign involving a wider set of strain-controlled loading cases, including multiaxial (biaxial) histories, is required for a more complete characterisation of the material performance.

The present investigation offers an advancement in the knowledge of cyclic transient effects exhibited by a typical α’ martensite SLM Ti-6Al-4V under symmetric and asymmetric strain-controlled tests. The research data and findings reported are among the very few reported so far in the literature.

This paper aims to investigate with strain-rate controlled uniaxial cyclic compression tests the softening behavior of concrete and its elastic stiffness degradation with increasing plastic straining.

Such tests at ambient temperature show that concrete exhibits the phenomenon of elastic stiffness degradation, which can be captured by damage-plasticity models.

The experimentally derived evolutions of the elastic stiffness with plastic strain confirm the suitability of the damage-plasticity modeling concept for concrete in compression at elevated temperatures and provide novel calibration data.

Temperature-dependent concrete models implementing this modeling concept are often used presently in structural fire engineering, despite the lack of experiment-based validation data.

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.

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.

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.

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.

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.

The stress analysis of structures subjected to cyclic loading requires stress—strain relations simple enough to be usable efficiently in computer program and yet adequate to describe the essential features of the plastic behaviour of the material reasonably well. The constitutive equation for cyclic plasticity incorporating the motion of the centre of the loading surface is proposed. Using the modified plastic work, the dependency of the loading history of materials is taken into account. The Ramberg—Osgood law which is applied to each stress—strain loop from the current centre of the loading surface plays an important role. This computer simulation for stress—strain relation of cyclic loading is justified from the point of view of several kinds of experiments on type 304 austenitic stainless steel.

The paper aims to shed some light on the effect of the notch/crack‐tip stresses and their role on the cyclic plasticity and crack growth behavior in compression‐compression fatigue.

Compression precracking was studied using 2D finite element analysis for CT specimen. The final crack length and the shape of the crack front were compared with those obtained experimentally.

It has been found that cyclic plasticity and stress redistribution govern the observed fatigue crack growth behavior in compression‐compression precracking. Only the internal stress corresponding to P_max shows a significant redistribution with the crack extension whereas the stress corresponding P_min is not affected by the increase of crack length.

This results are limited to Mode I cracking.

It supports that two thresholds, ΔK^th and K_max^th, govern the fatigue crack behavior. When the contribution from the internal tensile stress is not big enough to make K_max exceed K_max^th the crack will self arrest.

It has been found that cyclic plasticity and stress redistribution govern the observed fatigue crack growth behavior in compression‐compression precracking. The comparison of the numerical results with experimental data in terms of final crack length and crack front shape indicated a fair agreement.