残留応力場における2段繰返し変動荷重下の下限界近傍疲労き裂進展挙動

概要

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In order to make clear the effect of residual stress on fatigue crack growth behavior, fatigue crack growth tests under constant amplitude and repeated tow-step loadings were carried out on SM50A steel in the near threshold region by using the specimens with or without longitudinal residual stress. The crack length and crack opening point were measured by the unloading elastic compliance method. The results obtained are as follows. (1) Under varying loadings, a fatigue crack was found to grow in the residual stess field even when the low lefel effective stress intensity range (ΔK_<eff>)_L was less than (ΔK_<eff>)_<th>. (2) However, the fatigue crack growth rate under low level load (da/dn)^*_l was influenced by the number of cycles of low level load N_L. When N_L was rather large, the crack growth increment Δa_L became saturated and the averaged growth rate decreased. (3) The modified Miner type linear accumulation law of crack growth in terms of ΔK_<eff> was confirmed to give a conservative estimation of near threshold fatigue crack growth rate under varying loadings even in the residual stress field.
社団法人日本材料学会の論文
1989-10-15