Possibility Of Shear Band Formation Research Articles

A two-step approach to predict shear band development with crystal plasticity finite element method (CPFEM)

A two-step approach is proposed to investigate the shear band formation in cold-rolled aluminum alloy sheet during plane strain tension, compression and simple shear tests. In the first step, a finite element model with only one element using Taylor type polycrystal plasticity model is applied to compute the stress-strain curve of the deformation. In the second step, a full scale mesoscopic simulation is applied for a further study of the details of the shear band development for cases with higher possibility of shear band formation as judged from the results in step 1. Systematic studies show that the hardening/softening features of stress-strain curves obtained by one-element method well agree with the extent of macroscale shear bands development in mesoscopic scale simulation: softening or flat stress-strain curves correspond to the formation of severe macroscale shear band in mesoscopic scale simulation, and the stronger the softening is, the more severe the macroscale shear band is, whereas no macroscale shear band is developed when the curves exhibit continuous and obvious hardening. Therefore, when it is needed to investigate probability and features of shear band formation in many samples or loading modes, e.g. loading along different directions, people can use the first step to efficiently estimate the possibility of macroscale shear band development for all the cases concerned, and then apply the full scale mesoscopic simulation only for those cases where stress-strain curves exhibit little hardening or softening features. Our calculations show that the computation efficiency can be substantially improved by the two-step approach.

Evaluate the effect of laser shock peening on plasticity of Zr-based bulk metallic glass

Abstract The effect of laser shock peening (LSP) on mechanical properties, especially the plasticity of a typical Zr-based bulk metallic glass (BMG) had been investigated. The surface treatment introduced by successive laser pulses facilitated the formation of shear bands and promoted the plastic deformation of BMG. Experimental investigations of the bending deformation behavior were performed by three-point bending test at room temperature. It was found that the LSP pretreatment could improve the plasticity. The shear bands in fracture surface of laser peened sample were increased which could be observed by SEM. Logarithmic strain and stress distributions during bending deformation were predicted by finite element analysis. The high level of strain concentration in peened sample represented the increasing possibility of shear band formation which was beneficial to enhance plasticity. Corresponding with the strain distribution, the stress in peened sample was also increased which would enhance the ability of resisting a larger bending load force. Besides, simulation results clearly showed the logarithmic strain evolution of the beams with different laser irradiated regions throughout the bending process. The results indicated that the larger the laser irradiated region was, the better the plasticity of BMG would be.

Investigations of shear banding in an anisotropic hypoplastic material

This paper focuses on the analysis of shear band formation in a cohesionless and initially transversely isotropic granular material based on a hypoplastic continuum approach. The constitutive equation for the evolution of the stress is formulated with a non-linear tensor-valued function depending on the current void ratio, the Cauchy stress, the rate of deformation and a structure tensor for anisotropy effects. The possibility of shear band formation in biaxial, plane strain compression is analyzed and the sensitivity of the shear band orientation to the slenderness of the specimen is discussed.

Sommarî

A two-step approach is proposed to investigate the shear band formation in cold-rolled aluminum alloy sheet during plane strain tension, compression and simple shear tests. In the first step, a finite element model with only one element using Taylor type polycrystal plasticity model is applied to compute the stress-strain curve of the deformation. In the second step, a full scale mesoscopic simulation is applied for a further study of the details of the shear band development for cases with higher possibility of shear band formation as judged from the results in step 1. Systematic studies show that the hardening/softening features of stress-strain curves obtained by one-element method well agree with the extent of macroscale shear bands development in mesoscopic scale simulation: softening or flat stress-strain curves correspond to the formation of severe macroscale shear band in mesoscopic scale simulation, and the stronger the softening is, the more severe the macroscale shear band is, whereas no macroscale shear band is developed when the curves exhibit continuous and obvious hardening. Therefore, when it is needed to investigate probability and features of shear band formation in many samples or loading modes, e.g. loading along different directions, people can use the first step to efficiently estimate the possibility of macroscale shear band development for all the cases concerned, and then apply the full scale mesoscopic simulation only for those cases where stress-strain curves exhibit little hardening or softening features. Our calculations show that the computation efficiency can be substantially improved by the two-step approach.