Deformation Behaviors and Fracture Characteristics in Plate Containing Two Collinear Notches

A series of research so far carried out, has clarified that among various kinds of multiple notches existing in steel structures, the collinear notch has the largest influence upon brittle fracture initiations. In this research, therefore, the collinear notch is taken up as the subject of study, and examination is made on deformation behaviors ahead of notch tip and on fracture characteristics by elastic-plastic analysis based on the finite element method (FEM) and by experiments.The results are summarized as follows : (1) A crack opening displacement (COD) obtained by FEM is approximately equal to the theoretical value by E. Smith and a measured value by Moire method, which enables the coefficient of interaction effects of notches to be estimated by FEM.(2) When notches are contiguous very closely to each other, fracture stress is decreased and at the same time the critical COD is decreased. Therefore the concept of COD is not simply applicable to that case. The reason for the occurrence of such phenomenon is clarified through examination of the relation between the plastic strain in notch tip zone and the COD which are respectively calculated by FEM.