Anomalous Mechanical Behavior in Stationary Small Crack Tips about EAC for Nickel-Base Alloy

Abstract The crack tip mechanical characteristic and crack propagation rates are influenced by crack length, but the current research of environmentally assisted cracking (EAC) focuses on long crack, and small crack is usually ignored. The mechanical characteristics of small crack tips for single-edge crack panel specimens during the EAC in high temperature water were studied. The specimens were made of nickel-base alloy and the finite element method (FEM) was adopted. The results show that the stress and the strain are much higher for small crack compared to long crack, and this leads to a higher crack propagation tendency of small crack. A corrected method has been introduced to calculate the plastic zone size of small crack. The Irwin correction method can improve the accuracy of J integral of long crack, but errors still exist for small crack. So the numerical method with elastic plastic fracture method has been recommended to calculated J integral for small crack under larger load condition considering the lack of mature theoretical guidance about the small crack. The crack propagation process of the EAC of structure materials serviced in nuclear power plants is suggested to divide into small crack propagation and long crack propagation owing to their anomalous mechanical behaviors.