曲げ荷重下での三次元表面き裂のJ-積分の弾塑性評価式

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A J-integral equation, J = f_σ・H・f_W・f_θ・πa/Q/E', at surface and maximum depth point of a three dimensional surface crack under bending loads at elevated temperature for elastic-plastic analyses was developed. In this equation, the applied load and the crack shape are introduced to the J-integral value, and the fatigue crack growth behavior can be simulated precisely. The parameter f_σ is the function of applied load; H is the function of aspect ratio a/c and the ratio of crack depth to plate thickness a/t; f_w is the function of the ratio of crack length to plate width c/W; f_θ is the function of radiation angle to identify position along the elliptic crack front θ; Q is that of complete elliptic integral of the second kind E(k); E' is an equivalent elastic modulus. The equation is based on the finite element analysis completed by the authors with the surface cracked large plate specimen a few years ago. This new equation can be used to develop analyses given by the finite element method for 3-D semi-elliptical surface cracks in finite elastic-plastic plate, such as the wall of a main vessel of a fast breeder reactor, subjected to bending loads. A wide range of configuration parameters is included in the equation. The aspect ratios, a/c, ranged from 0 to 1, the ratios of crack depth to plate thickness, a/t, ranged from 0 to 0.7, and c/W ⪇ 0.8. The values of the J-integral computed by the equation were compared with those from the finite element analyses. The comparison showed that the mean errors were within ±3.9%. We also developed a method for using the J-integral equation to simulate the 3-D surface fatigue crack growth, and how the fatigue crack grows under bending loads at elevated temperature for SUS 304 steels at 550℃ and SUS 316 FR steel at 600℃. The curves of crack aspect ratio, a/c, vs. the ratio of crack depth to plate thickness, a/t, by the proposed method describe the experimental data well.
社団法人日本機械学会の論文
2003-04-25

曲げ荷重下での三次元表面き裂のJ-積分の弾塑性評価式

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