3次元屈折表面き裂の応力拡大係数の解析

抄録

The analysis of stress intensity factors K_I, K_II and K_III by the body force method was developed for a three dimensional bent surface crack which consists of plural crack planes. The stress intensity factors for various types of bent rectangular cracks at the surface of a semi-infinite body were numerically calculated.
The stress intensity factor K_θ which prescribes the stress field of the tangential stress σ_θ in the polar coordinate system (r, θ) at the crack tip was analyzed. The validity of Murakami's approximate formula: K_θmax≈0.650σ₀√π√area_P (area_P: crack area projected onto the plane perpendicular to the maximum remote principal stress σ₀) proposed for an arbitrarily shaped single plane surface crack was examined for various bent surface cracks. It was confirmed that Murakami's formula can be applied to most of bent cracks without loss of accuracy except for strongly bent V-shaped and L-shaped cracks. Furthermore, if one assumes a small amount of crack growth at the tip of strongly bent V-shaped and L-shaped cracks to the direction perpendicular to σ_θmax, Murakami's formula can be applied widely without loss of accuracy.