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1

A new method for identification of cyclic plasticity model parameters

Suchocki Cyprian, Kowalewski Zbigniew

Archives of Civil and Mechanical Engineering

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2022

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Vol. 22, no. 2

art. no. e69, 1--14

EN

In this study, a new method for determining the material parameters of cyclic plasticity is presented. The method can be applied to evaluate the model parameters from any loading histories measured experimentally. The experimental data require basic processing only to be utilized. The method can be applied to calibrate the parameters of different elastoplastic models such as the Chaboche-Rousselier (Ch–R) constitutive equation or other model formulations which use different rules of isotropic hardening. The developed method was utilized to evaluate the material parameters of copper for a selected group of constitutive models. It is shown that among the considered model formulations a very good description of the mechanical properties of copper is achieved for the Ch-R model with two Voce terms used for simulating the isotropic hardening and two backstress variables utilized for capturing the kinematic hardening behavior. Furthermore, it is demonstrated that a model calibrated using the cyclic tension/compression data is able to properly capture the material response in torsion. Similarly, when the constitutive parameters are determined using the cyclic torsion data the model is able to properly reproduce the material behavior in tension/compression. It is concluded that for the considered type of constitutive equations the material parameters can be identified from a single mechanical test. The proposed methodology was validated using the relations derived analytically.

2

An Identification of the Material Hardening Parameters for Cyclic Loading - Experimental and Numerical Studies

Skrzat A., Wójcik M.

Archives of Metallurgy and Materials

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2020

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Vol. 65, iss. 2

779--786

EN

This paper presents the results of experimental studies and numerical simulations of the ratcheting for the PA6 aluminum. In the initial determination of the material hardening parameters, the samples were subjected to the symmetrical strain-controlled cyclic tension-compression test. The experimental stress-strain curve was compared with the numerical one obtained for non-linear Frederick-Armstrong and Voce models. For better fitting of both curves, the optimization procedure based on the least-square method and the fuzzy logic was applied. After establishing the hardening parameters, numerical simulations of the ratcheting were made. The boundary value problem was solved by means of discrete analysis. The data (force and displacement) obtained in numerical computations were used to control the ratchetting experiment. The results of experiments and numerical calculations were compared. Good convergence proves the reliability of the determination of material hardening data.

3

The application of Chaboche model in uniaxial ratcheting simulations

Wójcik Marta, Skrzat A.

Advances in Manufacturing Science and Technology

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2020

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Vol. 44, nr 2

57--61

EN

This article presents the application of Chaboche nonlinear kinematic hardening model in simulations of uniaxial ratcheting. First, the symmetrical strain-controlled cyclic tension/compression tests for PA6 aluminum samples were done. Using the experimental stress–strain curve, initial material hardening parameters were determined by the ABAQUS software. The experimental curve was compared with the numerical one. For better fitting of both curves, the optimization procedure based on the least-square method was applied. Using the determined hardening parameters, numerical simulations of the ratcheting were done by the finite element analysis software. Numerical results were then compared with the experimental data obtained in the stress-controlled cyclic loading test.

4

Characterization of the cyclic-plastic behaviour of flexible structures by applying the Chaboche model

Archives of Civil and Mechanical Engineering

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2017

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Vol. 17, no. 4

761--775

EN

During seismic events, the gravity loads may cause a reduction of the lateral stiffness of structures; inelastic deformations combined with horizontal loads (P-Δ effect) can bring to a state of dynamic instability that obviously influences building safety. Especially for flexible structures, the P-Δ effect amplifies structural deformations and resultants stresses, and thus may represent a source of sideway collapse. Since this type of collapse is the result of progressive accumulation of plastic deformation on structural components, the specific objective of this works is to study this effect on a three floor metallic frame (made of aluminium alloy). A non-linear finite element (FE) model of the frame has been developed to study the dynamic non-linear behaviour of the structure, and compare it with the experimental results obtained from a scaled model of the real structure. The FE model, where a simple isotropic hardening behaviour was assumed for the material, was not able to reproduce the real behaviour of the structure. Rather, the correct description of the cyclic plastic behaviour of the material was essential for the numerical analysis of the structure. The characterization of the non-linear behaviour of the material was made by cyclic tension–compression tests on material specimen, from which the coefficients of Chaboche's model were properly calibrated. In this way, the finite element model of the structure provided results in optimum agreement with the experimental ones, and was able to predict the lateral collapse very well.

5

Comparison of two models of numerical simulation of low cycle fatigue of a plastic material with small rigid inclusions

Temis J M, Azmetov K Kh, Fleming W J

Journal of Theoretical and Applied Mechanics

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2013

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Vol. 51 nr 2

463--474

EN

Theory of Cells and a numerical FE method based on strain cyclic plasticity, damage model and technology of died elements were used for a prediction of the fatigue life of a metal matrix composite material. Results of calculations were compared with experimental fatigue data. It was shown that the predicted fatigue life of MMC using the method of cells was in close agreement with the experimental results for life outside of low cycle fatigue regime of 1000 cycles or less. The results obtained from the mathematical simulation procedure show that the failure occurs in several steps – the process of damage accumulation in the material and the process of crack growth. The results of prediction of time of the composite material full fracture are in good agreement with experimental data. The comparison show that both the numerical method and the theory of cells can be used to predict fatigue life of MMC to within an acceptable degree of accuracy.

PL

W pracy zastosowano teorię komórkową i numeryczną metodę elementów skończonych opartą na odkształceniowo cyklicznej plastyczności, wprowadzono model zniszczenia oraz uwzględniono technologię wytłaczania do określenia trwałości zmęczeniowej kompozytów metalowo-ceramicznych. Wyniki obliczeń porównano z badaniami doświadczalnymi. Zaobserwowano, że wyniki teoretyczne uzyskane z zastosowaniem teorii komórkowej były w zgodzie z eksperymentem dla niskocyklowego obciążenia zmęczeniowego, tj. dla 1000 cykli i poniżej. Rezultaty otrzymane w drodze symulacji numerycznych modelu matematycznego wskazały, że zniszczenie zmęczeniowe przebiega w kilku etapach – w wyniku akumulacji uszkodzeń i wskutek wzrostu szczeliny. Obliczenia czasu do pełnego pęknięcia kompozytu pokryły się z wynikami doświadczalnymi w dobrym stopniu. Po porównaniu efektywności metody numerycznej oraz teorii komórkowej stwierdzono w podsumowaniu, że obydwie metody mogą być stosowane do wyznaczania trwałości zmęczeniowej metalowo-ceramicznych materiałów kompozytowych z uzyskaniem zadawalającej dokładności.