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Mean Stress를 고려한 11.7Cr-1.1M₀강의 고온저주기 피로특성에 관한 연구
홍상혁(Sanghyuk Hong),홍춘희(Chunhyi Hong),이현우(Hyunwoo Lee) 한국자동차공학회 2006 한국 자동차공학회논문집 Vol.14 No.3
The Low cycle fatigue behavior of 11.7Cr-1.1Mo heat-resisting steel has been investigated under strain-controlled conditions with mean stresses at room temperature and 300℃. For the tensile mean stress test, the initial high tensile mean stress generally relaxed to zero at room temperature, however, at 300℃ initial tensile mean stress relaxed to compressive mean stress. Low cycle fatigue lives under mean stress conditions are usually correlated using modifications to the strain-life approach. Based on the fatigue test results from different stain ratio of -1, 0, 0.5, and 0.75 at room temperature and 300℃, the fatigue damage of the steel was represented by using cyclic strain energy density. Total strain energy density considering mean stress indicated well better than not considering mean stress at 300℃. Predicted fatigue life using Smith-Watson-Topper's parameter correlated fairly well with the experimental life at 300℃.
Strain rate을 고려한 크롬몰리브덴강의 고온저주기 피로특성 연구
이현우(Hyunwoo Lee),홍상혁(Sanghyuk Hong) 한국자동차공학회 2004 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
Isothermal fatigue characteristics of Cr-Mo heat resisting steel were investigated at high temperature. Isothermal low cycle fatigue tests at 300℃, 400℃ and 500℃ were performed with strain rates of 4×10?³/s, 4×10?⁴/s, 4×10??/s using smooth cylindrical specimens. Regardless of strain level, cyclic softening behavior was observed. The differences in fatigue lives were dependent on the magnitudes of plastic strain and total strain ranges. Plastic strain ranges were increased by increasing temperature and this plastic strain ranges together with ultimate strength can be used as the temperature compensation parameters.