A Comparative Study of Crack Branching in Glass Using Photoelasticity, Digital Image Correlation and Digital Gradient Sensing Techniques

摘要

Fracture behavior of high-stiffness and low-toughness materials such as soda-lime glass typically involves crack branching, a phenomenon which has not been well-understood. Attempts to shed light on this issue via full-field optical investigation has been hampered by numerous spatio-temporal experimental challenges as crack speeds in these materials reach upwards of 1500 m/s accompanied by highly localized small deformations. In this work, three different optical techniques - transmission photoelasticity, 2D Digital Image Correlation (DIC) and transmission-mode Digital Gradient Sensing (DGS) - are separately implemented to comparatively assess their efficacy to study crack growth and branching in soda-lime glass plates. Each method is implemented in conjunction with ultrahigh-speed photography (1-2 Mfps), flash/pulse illumination and a modified-Hopkinson pressure bar on nominally identical wedge impact experiments. Visualization of results from these experiments along with preliminary observations on their pros and cons of each approach for this material system are presented.