Numerical study of pile-up in bulk metallic glass during spherical indentation

Abstract

Pile-up around indenter is usually observed during instrumented indentation tests on bulk metallic glass. Neglecting the pile-up effect may lead to errors in evaluating hardness, Young's modulus, stress-strain response, etc. Finite element analysis was employed to implement numerical simulation of spherical indentation tests on bulk metallic glass. A new model was proposed to describe the pile-up effect. By using this new model, the contact radius and hardness of Zr 41.2 Ti 13.8 Cu 12.5 Ni 10 Be 22.5 bulk metallic glass were obtained under several different indenter loads with pile-up, and the results agree well with the data generated by numerical simulation.bulk metallic glass, spherical indenter, pile-up, contact radius, hardness Due to the unique physical, mechanical, and chemical properties, bulk metallic glasses (BMGs) are considered to be a class of very promising structure materials and will be adopted for application in various fields, such as civil astronautics, civil aeronautics and defense [1][2][3][4][5] . However, inhomogeneous flow of metallic glasses at room temperature is generally associated with highly localized shear bands [6,7] . The formation and interaction of shear bands control the mechanical properties, such as ductility and fracture toughness. Recently, Wang et al. have shown that high density, frequent interacting and arresting events of shear bands can lead to super-plasticity of BMGs at room temperature [8] . However, when BMGs are loaded under an unconstrained condition, such as in uniaxial tension or simple shear, rather few of shear bands can be induced. Once the shear bands are formed, BMGs fail catastrophically within the main shear band and show little plasticity [9][10][11] , thus limiting the application of BMGs as engineering material. So, for the sake of perceiving the plastic instability behavior and applications in engineering, much effort has been devoted to the mechanism of formation and evolution of shear bands in BMGs [12][13][14][15][16][17][18]

Avalanches, loading and finite size effects in 2D amorphous plasticity: results from a finite element model

“…Such simulations are able to replicate the mechanical behaviour of BMGs at relevant temperature and stress conditions (hundreds of Kelvin and MPa) [13,14,16]. FEM models have also allowed for studying mechanical properties based on surface effects and external stress gradients such as indentation [22] or surface roughness under deformation [23] and are applicable in situations with non-trivial boundary conditions. Our eigenstrain-based FEM model implements the same algorithm as the scalar (reference) model and is set up in the spirit of continuum modelling of internal stresses of dislocation systems [24,25].…”

Contact geometry during indentation of a sphere into an elastoplastic half-space

“…Based on the analysis of the profiles of the unloaded crateres presented in [21,28,29,30], we make the assumption: the profile of the bulk of the unloaded hole for a r  is described by the expression (Fig. 3) (Fig.…”