Properties of Deformation and Fracture of Type F82H Steel under Non-proportional Multiaxial Loading

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  • 非比例多軸負荷における核融合ブランケット構造材料F82Hの繰返し変形破壊特性

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<p>This paper discusses the properties of deformation and fracture of type F82H steel under non-proportional multiaxial loading. In this study, fatigue tests were carried out using a hollow cylinder specimen under three type loadings at 573 K in air. They are a push-pull loading, a reversed pure torsion (rev. torsion) loading and a circle loading. The push-pull loading and the rev. torsion loading tests are the proportional strain loading test. The circle loading test is the non-proportional strain loading test. The failure life in circle loading decreased compared with the failure lives in push-pull loading and rev. torsion loading. The failure life of type F82H steel is affected by strain path (non-proportionality). Interruption tests were also carried out to discuss cyclic deformation and failure behaviors by surface and microstructure observations and tensile tests. The sample of microstructure observation and tensile test were cut from specimen after interruption test. In surface observation, the microcracks were observed in early cycles in circle loading compared with push-pull loading and rev. torsion loading, and the number of microcracks in circle loading were the largest in the three strain paths. It is suggested that the decrease of failure life in circle loading is affected by the occurrence of microcracks in early cycles and the number of microcracks. In microstructure observation, the formation of dislocation was observed in early cycles, and the grain area decreased with increasing the number of cycle. In tensile tests, tensile strength tended to decrease, and reduction of tensile strength was remarkable in circle loading. It is suggested that this tendency is caused by softening.</p>

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