Dynamic Crack Branching in Soda-Lime Glass: An Optical Investigation Using Digital Gradient Sensing
Transparent brittle materials such as soda-lime glass (SLG) with relatively low fracture toughness and high stiffness pose unique challenges for performing full-field optical measurement of deformations and stresses to characterize their fracture behavior. The current work builds on authors’ previous report wherein the feasibility of Digital Gradient Sensing (DGS) was demonstrated for measuring stress wave induced crack-tip deformations in SLG. In this study, ultrahigh-speed photography (>1 million frames per sec) was used in conjunction with DGS and a Hopkinson pressure bar to load V-notched SLG plates to investigate the crack branching phenomenon. The experimental parameters were controlled such that a single mode-I crack that initiated at the V-notch tip propagated through the glass plate before branching into two prominent mixed-mode daughter cracks. The optical measurements of angular deflection fields that represent stress gradients in two orthogonal in-plane directions were obtained. Using higher order finite-difference based least-squares integration (HFLI) scheme, stress invariant fields (σxx + σyy) were evaluated near dynamically propagating crack-tip throughout the branching process.
KeywordsDigital gradient sensing Crack branching Soda-lime glass Dynamic fracture Hopkinson bar
The authors would like to thank the U.S. Army Research Office for supporting this research through grants W911NF-16-1-0093 and W911NF-15-1-0357 (DURIP).
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