THE EFFECT OF REFLECTED STRESS WAVE ON CRACK PROPAGATION IN SILICON CRYSTAL

One of the accepted claim is that when dynamic crack propagates at high speed in brittle materials, the reflected stress wave is responsible for significant crack speed reduction. However, this assumption has not been fully verified yet experimentally, and in brittle single crystals in particular.

Experiments were performed using a unique experimental setup that was developed in our lab. The method consists of loading a brittle single crystal specimen adhered to an aluminum loading-frame by two thin layers of epoxy resin. Upon heating the assembly, the thermal expansion coefficient mismatch between the specimen and the loading frame used as the driving force for crack initiation and propagation. In-vivo measurements of the temperature, strains, and voltage (potential drop technique) during crack propagation were used to evaluate crack speed. Energy was evaluated by finite element analysis method.

Recently, crack propagation on the (110)[1-10] low energy cleavage system of silicon crystal at high crack speed regime (V~0.8C_R) showed a small effect of the reflected stress wave on crack speed compares to Freund equation of motion. We will present the experimental setup and findings including new experimental variables essential for evaluating the behavior at high crack speed.