低サイクル疲労における平均応力効果とサイクリッククリープ

概要

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In a nominal or engineering stress-controlled low-cycle fatigue test, cyclic strain-induced creep (C.C) often advances when a mean stress is imposed. To examine rigorously the effect of this C.C behaviour on fatigue strength, true stress-controlled low-cycle fatigue tests were conducted on a medium carbon steel under imposed either tensile or compressive mean stress. The effects of a cyclic stress-strain relationship and C.C behaviour-produced axial plastic strain (ε_m) on fatigue strength were examined. The following results were also examined from the viewpoint of microcrack initiation and propagation. The following results were obtained : (1) the cyclic plastic strain versus stress amplitude relation at the steady cyclic stress-strain state showed a power type relationship , irrespective of tensile or compressive mean stress. (2) An increase of ε_m per cycle at half of the fatigue life was expressed by a power law of maximum tensile or compressive stress. (3) A modified Manson-Coffin relation, inclusive of a parameter of mean stress, was proposed. (4) The effect of the C.C behaviour on the fatigue strength was estimated on the basis of a microcrack growth law-aided approach previously developed.
社団法人日本機械学会の論文
1988-05-25