各種金属材料の切欠き部の低サイクル疲労特性

概要

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The fatigue cracks commonly initiate at the notched components under repeated loadings. So, the estimation of low-cycle fatigue life for the notched components is significantly important in the design of structures. In this study, the low-cycle fatigue tests were carried out using the smooth round bar specimens and the notched plate ones with the stress concentration factors K_t = 2A3, 3.26 and 4.25. The strains at the notch root were measured over the fatigue tests. The materials used are the copper alloy C 6161 P-O and the aluminum alloy A 7075-T 651. On the basis of test results, the relationships between the fatigue strength reduction factor K_f and the elastic-plastic strain concentration factor K_ε were obtained as K_ε<2: K_f=K, and K_ε≧2: K_f=1.25/K_ε^<0.68>. The relationship among the elastic stress concentration factor K_t, the elastic-plastic strain concentration factor K_ε and elastic-plastic stress concentration factor K_σ in the plastic region containing the tensile strength σ_B and the yield stress σ_y was proposed as (K_t-l) <σ_y/σ_B=0.34[(K_ε-1) (K_σ-l)]^<0.72>. Then, the fatigue life on the notched components was considered using these equations.
2007-08-25