分野別セミナー

Ductile fracture is, at room temperature, the most common mechanism of failure in metal. This fracture is divided into three stages: (1) void nucleation; (2) void growth; and (3) void coalescence. Beyond the last stage, the micro-crack is initiated. Many factors influence ductile fracture. One of them is hydrogen, where the presence of hydrogen reduces the strength of materials which in turn influences the ductile fracture. The main objective of this research is to conduct finite element simulation of the hydrogen effects on ductile fracture in a multi-scale context, which implies bridging the scale difference between adjacent simulation levels. To achieve this, the macroscopic and microscopic scale models of ductile fracture are studied simultaneously. To overcome this objective, the following subjects are studied. First, the finite element simulation of the hydrogen effects on the void growth process in a single void model which correlate to the macro scale tensile model. To correlate the macro- and micro-scale models, the displacements from the element at the center part of the tensile model are implemented as boundary conditions in the micro-scale void model. Second, the finite element simulation of the hydrogen effects on the void coalescence process within the multiple void array model in the square and diagonal void arrays which are spread on a notch tensile model. The last is the finite element simulation of the hydrogen effects on the micro-crack deformation. The results show the void growth and coalescence processes from the macro- and micro-scale, and the effects of hydrogen on these processes.