Abstract: The stress concentration factor at the tip of central crack in a strip is evaluated in two steps of numerical analysis. In the first step, stress distribution around the small region, SR, which includes a crack‐tip, is analyzed under a given tension. In the second step, the small region is imaginatively magnified. And the local stress concentration factor, KSR, is evaluated for the SR under five types of load, which are selected to simulate the stress distribution around the SR referring the stress distribution clarified in the first step. Based on this method, the influence of a microscopic defect exists near a crack‐tip upon the magnitude of KSR is considered. When stress waves propagate in a cracked strip, the dynamic stress concentration factor, Kd, is defined as the ratio of maximum amplitude of a stress pulse to that of applied amplitude. The influence of microscopic defect exists near a crack‐tip upon the magnitude of Kd is evaluated. When a short crack exists on the line slightly separated from the line of central crack, the influences of the short crack upon the magnitudes of KSR, and Kd at the tip of the central crack are also considered.
