Measurement of stress intensity factor under mixed-mode loading by the method of caustics
Hirose Yukio; Shozu Masayuki; Kawagishi Yuichi; Sasaki Toshihiko; Hirashima Ken-ichi
Abstract:As one of optical methods, the method of caustics is useful for determining the stress intensity factor. In this paper, the method of caustics was applied to the specimens with an oblique crack. The results obtained are summarized as follows: (1) The method of caustics is a useful technique to determine the stress intensity factors K1 and K11 separately under mixed-mode loading. (2) The existing theory used for measurement of this method is effective only when the initial curve radius t0 is larger than the minimum initial curve radius t0min determined in this study. It is recognized that the value of t0min decreases as the ratio of KII to KI increases. (3) The 3-D stress field exists in the vicinity of crack tip, while the state of stress is nearly plane-strain deformation in the case of mode I loading. In the case of mixed-mode loading, the state of stress is approximately plane-stress deformation as the ratio of KII to KI increases. (4) A correction is proposed to obtain the values of K from caustic images in the case of t0 < t0min. Key Words:the method of caustics, stress intensity factor, mixed-mode loading, initial curve, three-dimensional stress field