Development of a multiaxial fatigue theory by considering constraint effects on small mixed-mode cracks |
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| Institution: | 1. Department of Mechanical Engineering and Applied Mechanics, The University of Michigan, Ann Arbor, MI 48109, USA;1. College of Mechanical Engineering & Applied Electronics Technology, Beijing University of Technology, Beijing 100124, China;2. Department of Engineering Mechanics, AML, Tsinghua University, Beijing 100084, China;3. Department of Mechanical Engineering, University of South Carolina, 300 Main Street Columbia, SC 29208, USA;1. College of Energy & Power Engineering, Nanjing University of Aeronautics and Astronautics, Jiangsu, 210016, PR China;2. Aero-engine Thermal Environment and Structure Key Laboratory of Ministry of Industry and Information Technology, Nanjing University of Aeronautics and Astronautics, Jiangsu, 210016, PR China;3. State Key Laboratory of Mechanics and Control of Mechanical Structures, Nanjing University of Aero-nautics and Astronautics, Jiangsu, 210016, PR China;4. AECC Hunan Aviation Powerplant Research Institute, Hunan, 412002, PR China;1. Department of Materials Science & Engineering, Seoul National University of Science and Technology, Seoul 139-743, Republic of Korea;2. Display Research Center, Samsung Display Co., Ltd., Giheung-gu, Yongin-city, Gyeonggi-do, Korea |
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| Abstract: | The effects of the transverse strain (the normal strain in the crack-line direction) on the near-tip fields of small shallow surface cracks (Case A cracks) in power-law hardening materials are investigated by finite element analyses. The small Case A cracks are under plane stress, general yielding, and mixed mode I and II conditions. Constant effective stress contours representing the intense straining zones near the tip, deformed crack-tip profiles and near-tip mode mixity factors are presented for different transverse strains in the crack-line direction. Based on the concept of characterization of fatigue crack growth by the cyclic J-integral, the effects of the transverse strain on J are investigated. The results suggest that the fatigue life prediction based on multiaxial fatigue theories and the critical plane approach should include the constraint effects due to the transverse strain. Consequently, the concept of constant fatigue life contour on the Γ-plane in multiaxial fatigue theories is generalized to the constant fatigue life surface in the Γ-space where the shear strain and the two normal strains are the three axes. Finally, a damage parameter as a function of the shear strain and the two normal strains is proposed for evaluation of fatigue damage under multiaxial loading conditions. |
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