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) over dot 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) over dot and a. The behaviors of K-ID,(a) over dot and a in a SEN specimen were also examined, and the following correlations were obtained: (1) K-ID was an increasing function of (a) over dot, but their relation was not unique. (2) K-ID for a constant velocity (a) over dot was larger when the crack was decelerated than when it was accelerated. (3) K-ID was dependent on both (a) over dot and a, and K-ID for a=constant could be uniquely related to (a) over dot.