Issue 38

T. Morishita et alii, Frattura ed Integrità Strutturale, 38 (2016) 281-288; DOI: 10.3221/IGF-ESIS.38.38 281 Focussed on Multiaxial Fatigue and Fracture Creep-fatigue life evaluation of high chromium ferritic steel under non-proportional loading T. Morishita, Y. Murakami Graduate School of Science and Engineering, Ritsumeikan University, Japan gr0202xp@ed.ritsumei.ac.jp, rm0038kk@ed.ritsumei.ac.jp T. Itoh College of Science and Engineering, Ritsumeikan University, Japan itohtaka@fc.ritsumei.ac.jp H. Tanigawa National Institutes for Quantum and Radiological Science and Technology, Japan tanigawa.hiroyasu@qst.go.jp A BSTRACT . T Multiaxial creep-fatigue tests under non-proportional loading conditions with various strain rates were carried out using a hollow cylinder specimen of a high chromium ferritic steel at 823K in air to discuss the influence of non-proportional loading on failure life. Strain paths employed were a push-pull loading and a circle loading. The push-pull loading test is proportional strain path test. The circle loading test is non-proportional strain path test in which sinusoidal waveforms of axial and shear strains have 90 degree phase difference. The failure life is affected largely by the strain rate and the non-proportional loading. This paper presents a modified strain range for life evaluation considering the strain rate based on a non-proportional strain parameter proposed by authors. The strain range is a suitable parameter for life evaluation of tested material under non-proportional loading at high temperature. K EYWORDS . Life evaluation; Creep-fatigue; Multiaxial strain; Non- proportional loading; High chromium ferritic steel. Citation: Morishita, T., Murakami, Y., Itoh, T., Tanigawa, H., Creep-fatigue life evaluation of high chromium ferritic steel under non- proportional loading, Frattura ed Integrità Strutturale, 38 (2016) 281-288. Received: 30.07.2016 Accepted: 31.08.2016 Published: 01.10.2016 Copyright: © 2016 This is an open access article under the terms of the CC-BY 4.0, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. I NTRODUCTION n the blanket structure of a demonstration fusion reactor, the material receives severe cyclic loading conditions such as combined thermal and mechanical cyclic deformations. By the combination of thermal and mechanical loading, the non-proportional loading in which the principal stress and strain directions rotate in a cycle occurs. It has been I