Abstract
We present and compare three elastoplastic models currently used for deformation of metallic glasses, namely, a von Mises model, a modified von Mises model with hydrostatic stress effect included, and a Drucker-Prager model. The constitutive models are formulated in conjunction with the free volume theory for plastic deformation and are implemented numerically with finite element method. We show through a series of case studies that by considering explicitly the volume dilatation during plastic deformation, the Drucker-Prager model can produce the two salient features widely observed in experiments, namely, the strength differential effect and deviation of the shear band inclination angle under tension and compression, whereas the von Mises and modified von Mises models are unable to. We also explore shear band formation using the three constitutive models. Based on the study, we discuss the free volume theory and its possible limitations in the constitutive models for metallic glasses.
Highlights
Metallic glass, called amorphous alloy, is a relatively new material characterized by the random, disordered atomic arrangement which is different from the ordered crystalline structure of metals and Metals 2012, 2 alloys
One is the strength differential (SD) effect and the second the deviation of shear band inclination angles (SBIA) in uniaxial tension and compression. These results suggest that hydrostatic stress and/or normal stress should affect the deformation of metallic glasses, which are quite different from the von Mises criterion where volumetric effect, or hydrostatic stress and normal stress, does not play a major role
The reason of shear banding is believed to be a result of the volume dilatation, which has been elaborated in detail in the free volume theory [8]
Summary
Called amorphous alloy, is a relatively new material characterized by the random, disordered atomic arrangement which is different from the ordered crystalline structure of metals and Metals 2012, 2 alloys. One is the strength differential (SD) effect and the second the deviation of shear band inclination angles (SBIA) in uniaxial tension and compression These results suggest that hydrostatic stress (or volume strain) and/or normal stress should affect the deformation of metallic glasses, which are quite different from the von Mises criterion where volumetric effect, or hydrostatic stress and normal stress, does not play a major role. We implement the constitutive models in the finite element method to simulate the deformation process under plane strain condition From these models, we simulate shear banding as the main inhomogeneous deformation phenomenon and examine in detail the evolution of mechanical properties and free volume behaviors.
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