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Experiments and numerical simulations of Lueders bands and Portevin–Le Chatelier effect in aluminium alloy AW5083

Mucha M., Rose L., Wcisło B., Menzel A., Pamin J.

Archives of Mechanics

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2023

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Vol. 75, nr 3

301--336

EN

This work is focused on the modelling of experimental behaviour of a bone-shape sample made of aluminium alloy AW5083 under tension. This behaviour involves propagating instabilities, namely Lueders bands and the Portevin–Le Chatelier effect. A series of experiments was performed at room temperature for three loading rates, showing the instabilities and failure. In the paper a large strain thermovisco-plasticity model is proposed and used for finite element simulations. This model contains initial softening and a hardening function based on the Estrin–McCormick concept to represent serrations and travelling shear bands. The issues of instability sources and regularisation are considered. The predictive capabilities of the model are examined. The proposed models are able to reproduce both Lueders bands and the PLC effect. Simulation results show good agreement with experiments regarding force–displacement diagrams and temperature levels.

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Simulation of Lueders bands using regularized large strain elasto-plasticity

Mucha M., Wcisło B., Pamin J.

Archives of Mechanics

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2021

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Vol. 73, nr 1

83--117

EN

This paper deals with the numerical simulation of an instability phenomenon called Lueders bands with two regularized material models: viscoplasticity and gradient-enhanced plasticity. The models are based on large strain kinematics and temperature-dependence is incorporated. The Huber–Mises–Hencky yield condition and multi-branch hardening are employed. After a brief presentation of the constitutive description, test computations are performed using AceGen and AceFEM symbolic packages for Wolfram Mathematica. The first benchmark is a rectangular tensile plate in plane strain isothermal conditions. For the viscoplastic model, simulation results for different values of viscosity, loading duration and enforced displacement are compared. For the gradient model different internal lengths are used. Mesh sensitivity of the results and the influence of boundary conditions are also examined. Next to the Lueders-type response to a softening-hardening yield strength function, an additional softening stage leading to failure is also considered. The second example concerns a bone-shape sample under tension, for which, next to mesh sensitivity and the effect of regularization, the influence of heat conduction on simulation results is evaluated.

3

Simulation of propagative instability in shear using gradient-enhanced and viscoplastic model

Mucha Marzena, Wcisło Balbina, Pamin Jerzy

Computer Methods in Materials Science

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2019

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Vol. 19, No. 2

57--63

EN

The research presented in this paper is focused on simulation of a propagative instability called Lueders bands using large strain plasticity with Huber-Mises-Hencky yield function. Two types of regularization are used: gradient-enhanced plasticity and viscoplasticity. Regularization is needed to avoid mesh sensitivity associated with the classical continuum description. A special sample is used to study Lueders band propagation in shear, its shape is motivated by experiments. The gradient-enhanced model used in computation provides a more reliable regularization than the viscoplastic model.

PL

W artykule zaprezentowano symulacje numeryczne propagujących się pasm lokalizacji odkształcenia nazywanych pasmami Luedersa wykorzystując model dużych deformacji z funkcją plastyczności Hubera-Mises-Hencky'ego. Użyto dwóch typów regularyzacji, gradientowej plastyczności oraz lepkoplastyczności. Regularyzacja jest niezbędna celem uniknięcia zależności wyników od gęstości siatki elementów skończonych. Do przeprowadzania obliczeń w warunkach czystego ścinania została użyta specjalna próbka, której kształt motywowany jest eksperymentami. Model gradientowy wykazał lepsze możliwości regularyzacyjne niż model lepkoplastyczny.