形状不連続部付平板の非貫通型欠陥に対する曲げ疲労寿命予測 : 第1報 : 疲労き裂の形状変化とその表現式について

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Bending fatigue tests were performed using plates with transverse (grooves, fillets and protuberances) and through-thickness geometrical discontinuity (holes and grooves) in addition to plain plates. Shape change in fatigue crack growing from surface and corner flaws was investigated and the equation for expression of crack shape was proposed. The conclusions are summarized as follows : (1) Shape change in part-through fatigue crack growing in a plate with geometrical discontinuity was classified into equilibrated and non-equilibrated growth in the same way as shape change in fatigue surface crack growing in plain plate. (2) The equation for expression of the fatigue crack shape for the equilibrated growth was induced by simplification of the stress-field where fatigue crack grew ; for plain plate, b/α=1-b/t, for transverse geometrical discontinuity plate, b/α=1-(b/t)^<1/K_t,> and, for through-thickness geometrical discontinuity plate, [numerical formula] (3) The equation for expression of the fatigue crack shape for the non-equilibrated growth was induced by considering the relation between the initial flaw shape and the equilibrated growth crack shape ; for plain plate, [numerical formula] for transverse geometrical discontinuity plate, [numerical formula] and, for through-thickness gecurletrical discontinuity plate, [numerical formula] (4) Standard deviations of calculated values of b/ from measurements was 0.064 for plain plates Specimens. 0.111 for transverse geometrical discontinuity plate specimens and 0.066 for through-thickness geometrical discontinuity plate specimens. It was found that the equations proposed showed comparable order of accuracy in estimation. where, , _0 : Crack/initial flaw half length b, b_0 : Crack/initial flaw depth t : Thickness : Root radius of geometrical discontinuity K_t : Stress concentration factor C_i : Coefficients of polynominal approximation on stress-distribution m,n : Constants a,b : Constants on initial flaw shape
社団法人日本船舶海洋工学会の論文

形状不連続部付平板の非貫通型欠陥に対する曲げ疲労寿命予測 : 第1報 : 疲労き裂の形状変化とその表現式について

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