Fumitaka Motomura

Accurate Solutions of Stress Intensity Factors of Standard Fracture Test Specimens

Practically exact solutions of stress intensity factor for several two-dimensional standard specimens were calculated and shown in numeric tables. The solutions were confirmed to converge until 6 significant figures through a systematical computation of discretization analysis. The convergence analyses were carried out by using a general purpose program based on a body force method.

Simulation of Propagation and Localization of Minute Cracks Near a Mode II Crack Tip under Compressive Stresses

The failure behavior of brittle solids under compressive stresses is discussed. It is known that the failure mode of brittle solids under compressive stresses depends strongly upon specimen geometry and loading conditions. A plate specimen often exhibits a split-type fracture characterized by mode I cracks that propagate almost parallel to the direction of compression. On the other hand, a pseudo-mode II fracture in which the failure plane is inclined from the axis of compression can be observed in a compression test of a cylindrical specimen. In the uniaxial compression test of plate-type mortar and PMMA specimens, the macroscopic fracture was dominated by the appearance of mode-I wing cracks and their propagation. However, in a neighborhood of an artificial crack tip, a considerable damage zone was also observed. In order to investigate the mechanism for a formation of damage zone, numerical analyses base on the linear elastic fracture mechanics were carried out. It was found that the damage zone is composed of an echelon of mode I micro-surface cracks and the inclination of the damage zone is about 30° from the axis of compression.

Finite Element Analysis for Optimal Heating Condition in Thermal Stress Cleaving of Brittle Materials Using Laser Irradiation

An optimal condition of thermal stress cleaving was investigated by assuming the element-by-element temperature rise situation using finite element method. The obtained thermal stress cleaving condition is found to be optimal for the symmetrical cleaving of a rectangular plate.