Influence of Load Modes on the Characteristics of Severe Plastic Deformation Based on Crystal Plasticity Finite Element Method

A three-dimensional Voronoi polycrystal model with 125 grains was developed for analyzing the heterogeneous phenomena and microplasticity in polycrystalline solids. Using the crystal plasticity, finite element method, the role of the load modes in the response characteristics of severe plastic deformation was investigated. Among the tested load modes, uniaxial tension and plane compression are responsible for the presence of the shear band, while pure shear leads to uniform strain distribution, and simple shear leads to the concentration of deformation. The higher shear strain was achieved by torsion, followed by simple shear. At the start-up of the sliding system, torsion and pure shear have the strongest influence, while the effects of uniaxial compression and plane compression are relatively small. After experiencing the same strain, simple shear causes lower damage than torsion. In terms of the texture, after tensile strain, polycrystalline pure aluminum shows the texture of <111>//ND, after compression, the texture type is {110}//ND, and after torsion deformation, the texture type is <111>//TD. Under small strain, plane compression includes copper texture, brass texture, and S-texture. Under high strain, the {111} <211> (annealed) texture was found in simple shear deformation. Experimental observation verified the high accuracy of the simulation results based on the excellent agreement between experiment and simulations for the stress–strain curve and texture evolution, and slip bands. Based on the principle of maximum cumulative plastic strain and minimum damage, simple shear is determined to be the optimal fine grain mode in the SPD process.