CRACK-GROWTH IN SOLID WITH MANY INITIAL DEFECTS

Hydrogen-induced fracture of steel is characterized by the formation o f internal voids caused by hydrogen precipitation at an inclusion-matr ix interface, followed by the formation of microcrack array under the superposed action of internal hydrogen pressure and external forces. T he propagation of the hydrogen-induced fracture is considerably random and the fracture develops by stepwise linking of the microcracks. We present a new fracture model describing the patterns of crack growth b y hydrogen embrittlement to find a generic feature of delayed fracture . Crack growth in solid with many initial defects is studied by Monte Carlo simulation on a square lattice. By analyzing time-dependent clus ter size distribution of crack and its dynamic scaling, it is found th at the crack growth process has a fractal structure. ''Percolation of cracks'' which corresponds to macroscopic breakdown of materials is al so investigated.