Reproducibility of Pop-Ins in Fracture Test of Heterogeneous Welds and Numerical Assessment of Crack Arrest

Abstract

Abstract For the occurrence of a “pop-in,” which represents the initiation, propagation, and arrest of a brittle crack in a three-point bending test, the evaluated fracture toughness may be very small. To experimentally verify whether the pop-in occurring at the specimen level is even included in the actual structure, the purpose of this study was to first induce pop-ins in a three-point bending test. It was possible to reproduce a pop-in at a local brittle zone (LBZ) by preparing heterogeneous weld specimens and considering the temperature dependence of the toughness of each welding material. Furthermore, a crack propagation analysis by the nodal release method was conducted. The crack opening stress including dynamic effects was compared before and after the pop-in. Because of the initiation of brittle cracks in the LBZ, the high-stress area shifted from the center with low toughness to the edge with high toughness. Decrease in the crack opening stress was determined as a factor contributing to the crack arrest.