The metallurgical properties and fatigue life of bearing steel processed by electric furnace (EAF), ladle refining (LF-VD), continous casting (CC) and electroslag remelting (ESR) have been investigated. The main resul...The metallurgical properties and fatigue life of bearing steel processed by electric furnace (EAF), ladle refining (LF-VD), continous casting (CC) and electroslag remelting (ESR) have been investigated. The main results obtained are as follows: (1) Due to low oxygen content and dispersion inclusions in steel, the fatigue Life of LF-VD-IC or CC is three times as high as that of EAF steel; (2) The oxygen content in steel produced by CC process is about 9.0x10(-6), the carbon segregation (C/C(0)) is from 0.92 to 1.10 and the fatigue life of CC steel is equal to that of ladle refining ingot casting steel; (3) Although the amount of inclusion and oxygen in ESR steel is higher than that of LF-VD-IC or CC steel, the fatigue life of ESR steel is higher than that of the latter because of its fine and well dispersed inclusions.展开更多
Sixteen operating conditions were determined by the standards JIS-7105 and JIS-7106. The strength under complex operating conditions was calculated with HyperWorks and the strength analysis confirmed eight dangerous p...Sixteen operating conditions were determined by the standards JIS-7105 and JIS-7106. The strength under complex operating conditions was calculated with HyperWorks and the strength analysis confirmed eight dangerous points of the metro bolster beam. Since the metro did not consider the impact of traffic lights and sudden road conditions, the load spectra at eight dangerous points were established by counting the running time,passenger flow,site layout,site quantity and turning situations. The fatigue life of the metro bolster beam was projected by the von Mises stress method and the critical plane method. The results of these two methods revealed that the maximum damage occurred at the dangerous point 7,and the fatigue life based on the critical plane method was shorter than that based on the von Mises stress method.Since the McDiarmid model considered the effect of the magnitude and direction of the normal stress and the amplitude of the shear stress,it is closer to the actual situations of the metro. Hence,the McDiarmid model based on the critical plane method is more reasonable,and the method of fatigue life prediction is also suitable to the metro bolster beam of other lines.展开更多
In this paper, ultrasonic （20 kHz） fatigue tests were performed on specimens of a high-strength steel in very high cycle fatigue （VHCF） regime. Experimental results showed that for most tested specimens failed in ...In this paper, ultrasonic （20 kHz） fatigue tests were performed on specimens of a high-strength steel in very high cycle fatigue （VHCF） regime. Experimental results showed that for most tested specimens failed in a VHCF regime, a fatigue crack originated from the interior of specimen with a fish-eye pattern, which contained a fine granular area （FGA） centered by an inclusion as the crack origin. Then, a two-parameter model is proposed to predict the fatigue life of high-strength steels with fish-eye mode failure in a VHCF regime, which takes into account the inclusion size and the FGA size. The model was verified by the data of present experiments and those in the literature. Furthermore, an analytic formula was obtained for estimating the equivalent crack growth rate within the FGA. The results also indicated that the stress intensity factor range at the front of the FGA varies within a small range, which is irrespective of stress amplitude and fatigue life.展开更多
The effects of inclusions in powder superalloy FGH96 on low-cycle fatigue life were studied, and a low-cycle crack initiation life prediction model based on the theory of damage mechanics was proposed. The damage char...The effects of inclusions in powder superalloy FGH96 on low-cycle fatigue life were studied, and a low-cycle crack initiation life prediction model based on the theory of damage mechanics was proposed. The damage characterization parameter was proposed after the construction of damage evolution equations. Fatigue tests of the powder superalloy specimens with and without inclusion were conducted at 530 and 600 ℃, and the model verification was carried out for specimens with elliptical, semi-elliptical, polygon and strip-shaped surface/subsurface inclusion. The stress analysis was performed by finite element simulation and the predicted life was calculated. The results showed a satisfying agreement between predicted and experimental life.展开更多
文摘The metallurgical properties and fatigue life of bearing steel processed by electric furnace (EAF), ladle refining (LF-VD), continous casting (CC) and electroslag remelting (ESR) have been investigated. The main results obtained are as follows: (1) Due to low oxygen content and dispersion inclusions in steel, the fatigue Life of LF-VD-IC or CC is three times as high as that of EAF steel; (2) The oxygen content in steel produced by CC process is about 9.0x10(-6), the carbon segregation (C/C(0)) is from 0.92 to 1.10 and the fatigue life of CC steel is equal to that of ladle refining ingot casting steel; (3) Although the amount of inclusion and oxygen in ESR steel is higher than that of LF-VD-IC or CC steel, the fatigue life of ESR steel is higher than that of the latter because of its fine and well dispersed inclusions.
基金National Key Technology Research and Development Program of China(No.2014BAF08B01)Collaborative Innovation Center of Major Machine Manufacturing in Liaoning,China
文摘Sixteen operating conditions were determined by the standards JIS-7105 and JIS-7106. The strength under complex operating conditions was calculated with HyperWorks and the strength analysis confirmed eight dangerous points of the metro bolster beam. Since the metro did not consider the impact of traffic lights and sudden road conditions, the load spectra at eight dangerous points were established by counting the running time,passenger flow,site layout,site quantity and turning situations. The fatigue life of the metro bolster beam was projected by the von Mises stress method and the critical plane method. The results of these two methods revealed that the maximum damage occurred at the dangerous point 7,and the fatigue life based on the critical plane method was shorter than that based on the von Mises stress method.Since the McDiarmid model considered the effect of the magnitude and direction of the normal stress and the amplitude of the shear stress,it is closer to the actual situations of the metro. Hence,the McDiarmid model based on the critical plane method is more reasonable,and the method of fatigue life prediction is also suitable to the metro bolster beam of other lines.
基金supported by the National Basic Research Program of China (Grant 2012CB937500)the National Natural Science Foundations of China (Grants 11172304 and 11202210)
文摘In this paper, ultrasonic （20 kHz） fatigue tests were performed on specimens of a high-strength steel in very high cycle fatigue （VHCF） regime. Experimental results showed that for most tested specimens failed in a VHCF regime, a fatigue crack originated from the interior of specimen with a fish-eye pattern, which contained a fine granular area （FGA） centered by an inclusion as the crack origin. Then, a two-parameter model is proposed to predict the fatigue life of high-strength steels with fish-eye mode failure in a VHCF regime, which takes into account the inclusion size and the FGA size. The model was verified by the data of present experiments and those in the literature. Furthermore, an analytic formula was obtained for estimating the equivalent crack growth rate within the FGA. The results also indicated that the stress intensity factor range at the front of the FGA varies within a small range, which is irrespective of stress amplitude and fatigue life.
基金sponsored by AECC Beijing Institute of Aeronautical Materialsfunded by National High-tech R&D Program of China (863 Program) (No. 2015AA034401)。
文摘The effects of inclusions in powder superalloy FGH96 on low-cycle fatigue life were studied, and a low-cycle crack initiation life prediction model based on the theory of damage mechanics was proposed. The damage characterization parameter was proposed after the construction of damage evolution equations. Fatigue tests of the powder superalloy specimens with and without inclusion were conducted at 530 and 600 ℃, and the model verification was carried out for specimens with elliptical, semi-elliptical, polygon and strip-shaped surface/subsurface inclusion. The stress analysis was performed by finite element simulation and the predicted life was calculated. The results showed a satisfying agreement between predicted and experimental life.
