モードII負荷を受ける三次元き裂のCorner Point Singularity

概要

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The point where the front of a 3-D crack intersects a free surface is called"corner point". The ordinary crack tip stress singularity of γ^λ with λ=-0.5 has been well known in fracture mechanics. However, with regard to the stress singularity at the corner point there are several theories which have not been clearly accepted. This paper is concerned with the detailed analysis of the stress singularity at the corner point for a through crack and a semi-circular crack under Mode II loading. According to the theories by Benthem and others, not only K_<II>but also K_<III> has a non-zero value at a corner point which, however, contradicts the stress-free boundary condition of the free surface. The FEM analysis of the present study based on the careful meshing and accurate determination of singularity(λ)answers to this strange question on the corner point singularity. The answer is that although the value of K_<III> increases as the crack front approaches the corner point, the domain of non-zero value of K_<III> decreases infinitesimally and accordingly the influence of K_<III> can be ignored at the corner point. Similarly, the domain of the singular stress field with λ≐̸-0.5 and λ=-0.6〜-0.5 also decreases as the crack front approaches the corner point. These conclusions must be considered when the fracture criterion at a corner point under mixed-mode loading is discussed.
一般社団法人日本機械学会の論文
2000-12-25