Papers by Author: Y. Imai

Abstract: The occurrence of small scale plasticity can be modeled physically by force doublets embedded in an elastic medium and therefore the plasticity problem can be treated by the superposition of elastic solutions. This idea for the treatment of an inelastic strain is reviewed and generalized to develop a versatile program for two-dimensional elastic-plastic problems based on Body Force Method. In the present study, a treatment of an elastic-perfect plastic body is discussed in detail. The increment of the density of force doublets, which has one to one correspondence to the increment of plastic strain, can be determined from Prandtl-Reuss equation. It was also found the Delaunay triangulation is useful and convenient for the automated elastic-plastic analysis.

Abstract: The influence of surface roughness in crack face on the behavior of crack growth is studied. Numerical results derived from two kinds of mechanical models representing the macroscopic and microscopic asperity supposed to exist in the face of an initial crack are compared. In macro-asperity model, the influence of location and size of single-triangular asperity on the stress intensity factor is evaluated. In this model, it is found that the mode-I stress singularity appears in certain circumstances even under overall compression. In micro-asperity model, influence of friction coefficient on the trajectory of crack path is discussed. There exists a tendency that a path of wing crack growth becomes more straight and parallel to axis of compression as the friction coefficient increases.