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Low Cycle Fatigue Behavior of Gray Cast Iron Used for Engine |
YUAN Yongli1 HE Guoqiu1** FAN Kangle1 LIU Xiaoshan1 ZHU Minhao2 |
1. School of Materials Science and Engineering, Tongji University, Shanghai Key Laboratory for R&D and Application of Metallic Functional Materials, Shanghai 201804
2. Nation Traction Power Laboratory, Southwest Jiaotong University, Chengdu 610031 |
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Cite this article:
YUAN Yongli, HE Guoqiu, FAN Kangle, LIU Xiaoshan, ZHU Minhao. Low Cycle Fatigue Behavior of Gray Cast Iron Used for Engine. Chinese Journal of Materials Research, 2013, 27(5): 469-476.
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Abstract Low cycle fatigue (LCF) behaviors of grey cast iron used for cylinder were investigated at room temperature (RT), 150℃ and 250℃. Tensile stress-strain curves, cyclic stress-strain curves and fatigue life curves were obtained. The results show that Young’s Modulus, proof strength and ultimate tensile strength of grey cast iron decreased with increasing temperature, while the elongation increased. Cyclic hardening/softening exhibited cyclic hardening initially, then softening and fracture at lower strain amplitudes, while it exhibited cyclic softening and fracture directly without cyclic hardening at 150℃, 250℃ and higher strain amplitudes. Fatigue life decreased with the increase of temperature and was lowest at 150℃. LCF cracks initiated predominantly at the flake graphite tip, near-surface defects such as inclusions and voids, and crack would propagate along graphite. Heterogeneous inclusions contributed crack deflection and bifurcation which would decrease the propagating rate. Crack propagation was mainly characterized by fan shaped cleavage plane, secondary cracks, fatigue striation and some dimples, which indicated the fractural mechanism is intergranular and quasi-cleavage cracks.
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