The fatigue and fracture behavior of nickel-based superalloy Inconel 718 was investigated up to the very high cycle regime under rotary bending tests at room temperature. It was found that this superalloy can still fr...The fatigue and fracture behavior of nickel-based superalloy Inconel 718 was investigated up to the very high cycle regime under rotary bending tests at room temperature. It was found that this superalloy can still fracture after exceeding 107 cycles. Fractographic analysis revealed that there was a transition from fatigue crack initiation at multi-sites to single initiation with decreasing stress levels. The fracture surface can be divided into four areas according to the appearance, associated with fracture mechanics analysis of the corresponding stress intensity factors. The fracture mechanism dominant in each area was disclosed by scanning electron microscope examination and analyzed in comparison with those obtained from the crack growth tests. Subsequently, life prediction modeling was proposed by estimating the crack initiation and propagation stage respectively. It was found that Chan (2003)'s model for initiation life and the Paris law for growth life can provide comparable predictions against the experimental life.展开更多
In order to predict the mechanism of the formation and propagation of rolling contact fatigue cracks in Hadfield steel railway crossings(HSRC),the residual strain,microstructure,crystal orientation,and microhardness s...In order to predict the mechanism of the formation and propagation of rolling contact fatigue cracks in Hadfield steel railway crossings(HSRC),the residual strain,microstructure,crystal orientation,and microhardness surrounding fatigue cracks were investigated.Results show that the formation and propagation of fatigue cracks in HSRC have no correlation with the crystal orientation and boundaries of grains.The hardness and residual strain in the field around the fatigue crack are lower than those in other regions.The compressive strain around the fatigue crack is released after crack propagates,which reduces the hardness around the fatigue crack.Deformation twins and dislocations play a key role in the work hardening of HSRC.展开更多
基金Project supported by the National Natural Science Foundation of China (Nos 10872105 and 51071094)the Mitsubishi Heavy Industries, Ltd, Japan
文摘The fatigue and fracture behavior of nickel-based superalloy Inconel 718 was investigated up to the very high cycle regime under rotary bending tests at room temperature. It was found that this superalloy can still fracture after exceeding 107 cycles. Fractographic analysis revealed that there was a transition from fatigue crack initiation at multi-sites to single initiation with decreasing stress levels. The fracture surface can be divided into four areas according to the appearance, associated with fracture mechanics analysis of the corresponding stress intensity factors. The fracture mechanism dominant in each area was disclosed by scanning electron microscope examination and analyzed in comparison with those obtained from the crack growth tests. Subsequently, life prediction modeling was proposed by estimating the crack initiation and propagation stage respectively. It was found that Chan (2003)'s model for initiation life and the Paris law for growth life can provide comparable predictions against the experimental life.
基金supported by the National Science Foundation for Distinguished Young Scholars(Grant No.50925522)
文摘In order to predict the mechanism of the formation and propagation of rolling contact fatigue cracks in Hadfield steel railway crossings(HSRC),the residual strain,microstructure,crystal orientation,and microhardness surrounding fatigue cracks were investigated.Results show that the formation and propagation of fatigue cracks in HSRC have no correlation with the crystal orientation and boundaries of grains.The hardness and residual strain in the field around the fatigue crack are lower than those in other regions.The compressive strain around the fatigue crack is released after crack propagates,which reduces the hardness around the fatigue crack.Deformation twins and dislocations play a key role in the work hardening of HSRC.
