非比例負荷における多軸低サイクル疲労強度特性の材料依存性

概要

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This study describes the evaluation of material dependence of multiaxial low cycle fatigue to develop a suitable strain parameter for life prediction under non-proportional loading. Strain controlled multiaxial low cycle fatigue tests using 4 types of proportional and non-proportional strain histories were carried out on SUS316NG and SGV410 hollow cylinder specimens at room temperature. The reduction of low cycle fatigue life due to non-proportional loading was discussed relating to an additional hardening and crack initiation and propagation behaviors, and the applicability of the nonproportional strain proposed by the authors was also discussed. Fatigue lives decreased down to 1/5 by the non-proportional loading depending on strain history for SUS316NG and SGV410 steels, whereas the degree of additional hardening was different, which suggested that another factor like difference of crystal structure should be taken into account for the life prediction under non-proportional loading.