Correlations among dynamic stress intensity factor, crack velocity and acceleration in brittle fracture

Dynamic fracture in PMMA was studied to determine the correlations among dynamic stress intensity factor K_ID, crack velocity a and acceleration a. Specimen geometry, a single-edge-cracked tensile plate with two circular holes, was employed to obtain the crack acceleration, deceleration and re-acceleration process in a single fracture event. K_ID was evaluated using the method of caustics in combination with a Cranz-Schardin high-speed camera and correlated with a and a. The behaviors of K_ID, a and a in a SEN specimen were also examined, and the following correlations were obtained: (1) K_ID was an increasing function of a, but their relation was not unique. (2) K_ID for a constant velocity a was larger when the crack was decelerated than when it was accelerated. (3) K_ID was dependent on both a and a, and K_ID for a = constant could be uniquely related to a.