Characteristic distance as a material's structure parameter in the theory of fracture emanating from notches and cracks

摘要

The most typical for engineering materials micromechanism is discussed of fracture involving the coalescence process between the main crack and microcrack nucleated ahead of main crack. The appropriate criteria for mathematical description of such process are described. The direct fractographic results are presented proving the existence of the characteristic distance during the materials fracture process. Some experimental results are presented characterising the fracture toughness of two pipe-line steels and three nodular graphite cast irons. The anisotropy of pipe-line steels is related to their structural anisotropy affected the characteristic distance difference with respect to the different crack propagation directions. Role of graphite nodules is discussed as a main factor governing the fracture toughness of nodular cast irons.