Stress Intensity Factors of Brittle Crack during Propagation and on Arrest

Abstract

Quantitative evaluation of stress intensity factors a steel experienced during propagation and on arrest of a brittle crack was made by applying the X-ray fractography technique to the fracture surface of the compact specimens of a pressure vessel steel SA533B C1. 1. The stress intensity factor, which was determined along the crack path using the half value breadth of X-ray diffraction intensity curve obtained on the fracture surface, was found to decrease monotonically as the crack propagated, but to become undulating before arrest. It was shown, contrary to the general belief, the stress intensity factor for crack arrest was not necessarily the smallest, not even a minimum, of all those obtained for the crack propagation. The stress intensity factor for crack arrest was in good agreement with the crack arrest toughness KIa determined by the static analysis, while it was smaller than KID determined by the dynamic analysis.