Abstract
A crystal plasticity model accounting for damage evolution and ductile failure in a single crystal due to the presence of voids or micro-cracks is presented. An accurate, robust and computationally efficient single crystal implementation is extended and applied to model the behaviour of different aluminium alloys in the cast and homogenized condition and the extruded condition. A total of four different materials are investigated, in which the yield strength, work hardening, grain structure, crystallographic texture and tensile ductility are unique for each alloy. The coupled damage and single crystal plasticity model is used in three-dimensional polycrystalline finite element analyses of one smooth and two notched axisymmetric tensile specimens for each material. The tensile tests are analysed in Abaqus/Explicit, where each grain is explicitly modelled. An efficient procedure for calibrating the work-hardening parameters for single crystal plasticity models is proposed and used to determine the material parameters from the tension tests of the smooth tensile specimen with high accuracy. The capability of the proposed crystal plasticity model is demonstrated through comparison of finite element simulations and experimental tests. A good agreement is found between the experimental and numerical results, and the various shapes of the failed specimens are well predicted by the crystal plasticity finite element analyses. For one of the extruded aluminium alloys, a diamond-shaped fracture surface is observed in the experiments of the notched tensile specimens and also this unusual shape is captured by the crystal plasticity analyses.
Highlights
The process of ductile fracture includes nucleation, growth and coalescence of microscopic voids at second-phase particles or inclusions, and depends markedly on the local stress state and microstructural material characteristics in a complex way (Pineau et al, 2016)
For the cast and homogenized materials, the orientations are drawn from a “uniformODF” to generate a random texture for these materials, while for the extruded materials the measured texture, i.e., the orientation distribution function (ODF) is used to generate a set of orientations representing the texture for each alloy
The main reason is probably that the anisotropic work-hardening behaviour and plastic flow of this alloy has previously been found to significantly depend on the heat treatment in addition to the crystallographic texture (Khadyko et al, 2017), a feature that the work-hardening model used in the present study is unable to describe
Summary
The process of ductile fracture includes nucleation, growth and coalescence of microscopic voids at second-phase particles or inclusions, and depends markedly on the local stress state and microstructural material characteristics in a complex way (Pineau et al, 2016). Rousselier (2021) proposed a porous plasticity multiscale modelling framework In this framework, a conventional porous plasticity model is used where the work-hardening response of the matrix flow stress is determined by crystal plasticity combined with the self-consistent homogenization technique and the reduced texture methodology. A total of four different materials are considered, where each alloy display different yield strength, work hardening, grain structure, crystallographic texture and tensile ductility, and represent a majority of wrought aluminium alloys The results from these crystal plasticity finite element analyses are compared to the experimental tests of the different aluminium alloys presented in Thomesen (2019) and Thomesen et al (2020, 2021), and a good agreement is found between the numerical and experimental results. The proposed model’s ability to describe the behaviour of the distinctly different materials demonstrates its potential in finite element analyses of ductile polycrystalline materials
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