Computational Analysis of Fracture and Surface Deformation Mechanisms in Pre-Cracked Materials under Various Indentation Conditions

Context: The mechanical performance of exceedingly soft materials such as Ag is significantly influenced by various working conditions. Therefore, this study systematically investigates the effects of crack geometry, substrate crystal orientation, and indenter shape on crack propagation. The mechanical response of Ag is analyzed using the quasi-continuum (QC) method. A pre-crack with a predefined depth and angle was introduced to initiate fracture behavior. The results show that when the pre-crack height is 50 Å, the crack propagates rapidly as the imprint depth increases from 0 to 7 Å, grows steadily up to 15 Å, and then accelerates sharply between 15 and 20 Å. For other pre-crack heights, crack propagation occurs at a relatively faster rate. Substrates with [100], [010], and [001] crystal orientations promote crack extension, while the onset of plastic deformation (referred to as the yield point in this study) and the fracture strength both increase with increasing pre-crack height. The yield point, fracture strength, and stress intensity factors are highly sensitive to the pre-crack height. When the pre-crack angle is 90°, the fracture strength reaches its maximum of 0.2% higher than that of the uncracked sample-whereas at 0°, it reaches its minimum, still 53.8% higher than that of the uncracked sample. Methods: The sample model is conducted using AutoCAD software. The optimized quasi-continuum (QC) method is used to investigate the effects of different crack geometries, substrate crystal orientations, and indenter shapes on the crack extension of Ag material. Baskes and Dow (FBD) potential is borrowed to describe the interaction forces between Ag-Ag, Ni-Ag, and Ni-Ni.