疲労き裂進展の下限界に及ぼす荷重履歴の影響

概要

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The effects of loading history on threshold stress intensity range (ΔK_<th>) were investigated in a low alloy steel SFVQ1A (A508-3) and a low carbon steel S10C. A single overload and multiple overloads were chosen as loading history. Crack growth and crack closure following the loading histories were measured at load ratios of 0.05 and 0.07. Threshold values were determined as a fatigue limit of preloaded specimens. The ΔK_<th> values increased with increasing overload stress intensity factor (K_h). For a given K_h value, multiple overloads produced much larger increase in ΔK_<th> than a single overload and threshold values expressed by maximum stress intensity factor (K_<max,th>) were almost constant, independent of stress ratio. The results obtained were discussed in terms of crack closure behavior, and a method was proposed to evaluate the threshold value based on plasticity-induced crack closure.
社団法人日本機械学会の論文
1987-03-25