Computational Analysis of Fracture and Surface Deformation Mechanisms in Pre-Cracked Materials under Various Indentation Conditions
T.-H. Bui, Y.-S. Lu; Y.-S. Liao, and T.-H. Fang
Computers, Materials & Continuua, 87, 15 (2026).

ABSTRACT
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 & Aring;, the crack propagates
rapidly as the imprint depth increases from 0 to 7 & Aring;, grows steadily up
to 15 & Aring;, and then accelerates sharply between 15 and 20 & Aring;. 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 circle, the fracture strength reaches its maximum of 0.2% higher than that
of the uncracked sample-whereas at 0 circle, it reaches its minimum, still 53.8%
higher than that of the uncracked sample. 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.