Outline of collaborative research
In this study, to establish creep-fatigue life prediction approach of heat-resistance steels under multiaxial non-proportional loading, fatigue and creep-fatigue tests were systematically conducted via employing various loading paths. After tests, to investigate damage mechanism, post-examination using SEM, EBSD and TEM were carried out. Based on obtained results, it is known that both loading path and holding time affected creep-fatigue life of material. A creep-fatigue life prediction approach was proposed by considering non-proportional factors and stress triaxiality on the basis of strain energy density strain energy density exhaustion, by which creep-fatigue life was predicted within 2 factor lines. The predicted outcomes indicate the proposed has high accuracy. In addition, the SEM, EBSD and TEM observation results demonstrate that under uniaxial loading conditions, the main deformation mechanism is planer slip, pure fatigue loading only activate single slip system, whereas creep-fatigue loading leads to multi-slip activations. By contrary, under non-proportional loading conditions, deformation mechanism is changed to wavy slip, as manifested by cell structure, which is the main reason for additional hardening.
Papers, etc.
Peer-reviewed articles
- Le XU, Ji WANG, Run-Zi WANG, Lei HE, Takamoto ITOH, Hideo MIURA, Xian-Cheng ZHANG, Shan-Tung TU. On multiaxial creep–fatigue considering the non-proportional loading effect: Constitutive modeling, deformation mechanism, and life prediction. International Journal of Plasticity. 155 (2022) 103337.
- Le Xu, Run-Zi Wang, Lei He, Xian-Cheng Zhang, Shan-Tung Tu, Hideo Miura, Takamoto Itoh. Establishment of unified creep–fatigue life prediction under various temperatures and investigation of failure physical mechanism for Type 304 stainless steel. Fatigue Fract Eng Mater Struct. 2022; 45: 3086–3101.
- Le XU, Lei HE, Takaki KOJIMA, Takashi NOZAWA, Takamoto ITOH. Multiaxial creep-fatigue constitutive modeling and damage evaluation for type F82H steel under non-proportional loading conditions. International Journal of Fatigue 170 (2023) 107555.
- Le Xu, Run-Zi Wang, Yu-Chen Wang, Lei He, Takamoto Itoh, Ken Suzuki, Hideo Miura, Xian-Cheng Zhang. Microstructural evolutions and life evaluation of non-proportional creep-fatigue considering loading path and holding position effects. Materials Characterization. 204 (2023) 113209.
- Xin-Hao Zhang, Le Xu, Run-Zi Wang, Ti-Wen Lu, Lei He, Takamoto Itoh, Xian-Cheng Zhang. Multiaxial creep–fatigue failure mechanism and life prediction of a turbine blade based on a unified numerical solution approach. Fatigue Fract Eng Mater Struct. 2024;1–17.
- Yu-Chen Wang, Le Xu, Lei He, Lv-Yi Cheng, Shuai Chang, Shoto Yoshikawa, Shan-Tung Tu, Takamoto Itoh. Fatigue behaviors and life evaluation of AISI304 stainless steel under non-proportional multiaxial random loading. International Journal of Fatigue 186 (2024) 108417.
Symposia, seminars, etc.
International conference presentation
- Le XU, Run-Zi WANG, Lei HE, Takamoto ITOH. Modelling of Constitutive Behavior and Prediction of Multiaxial Creep-fatigue Damage Evolution under Non-proportional Loading at Elevated Temperature. 2021 International Symposium on Structural Integrity (ISSI-2021), Oct 8-11, Hangzhou, China.
- Lei He, Le Xu, Takamoto Itoh. Multiaxial creep-fatigue deformation modeling and damage evaluation considering non-proportional loading effect. 10th International Symposium on Functionalization and Applications of Soft/Hard Materials (Soft/Hard 2023), March 3-4, Shiga, Japan, 2023.
- Gaurav Raj, Kohei Suzuki, Lei He, Takamoto Itoh. Fatigue Strength Analysis of AISI 304 under Multiaxial Non-proportional Loading in High Cycle Region. 2024 International Symposium on Structural Integrity (ISSI-2024), Nov 5-5, Dongguan, China.
- Yu-Chen Wang, Le Xu, Lei He, Shoto Yoshikawa, Keisuke Yamashita, Shan-Tung Tu, Takamoto Itoh. Mean Strain Effects on Low Cycle Fatigue under Multiaxial Non-proportional Random Loading. 2024 International Symposium on Structural Integrity (ISSI-2024), Nov 5-5, Dongguan, China.
Future prospects/aspiration
In the future, in order to extend the research topic, creep-fatigue life prediction under multiaxial non-proportional loading will be performed, considering structural integrity and reliability via deep learning method.
Based on the achievements obtained thus far, clarification of creep-fatigue damage behavior under triaxial loading condition will be sought. After obtaining sufficient data, in-depth analysis and nano-scale simulation will be carried out through collaboration with Profs. at RU, ECUST and University of California, Berkeley.
