Evaluation of contact fatigue life of a wind turbine carburized gear considering gradients of mechanical properties

2018 ◽  
Vol 28 (8) ◽  
pp. 1170-1190 ◽  
Author(s):  
Wei Wang ◽  
Huaiju Liu ◽  
Caichao Zhu ◽  
Zhangdong Sun

Case hardening processes such as carburizing are extensively applied in heavy-duty gears used in wind turbines, ships, high-speed rails, etc. Contact fatigue failure occurs commonly in engineering practice, thus reduces reliabilities of those machines. Rolling contact fatigue life of a carburized gear is influenced by factors such as the gradients of mechanical properties and profile of initial residual stress. In this regard, the study of contact fatigue life of carburized gears should be conducted with the consideration of those aspects. In this study, a finite element elastic–plastic contact model of a carburized gear is developed which takes the gradients of hardness and initial residual stress into account. Initial residual stress distribution and the hardness profile along the depth are obtained through experimental measurements. The effect of the hardness gradient is reflected by the gradients of yield strength and fatigue parameters. The modified Fatemi–Socie strain-life criterion is used to estimate the rolling contact fatigue life of the heavy-duty carburized gear. Numerical results reveal that according to the Fatemi–Socie fatigue life criterion, rolling contact fatigue failure of the carburized gear will first initiate at subsurface rather than surface. Compared with the un-carburized gear, the rolling contact fatigue lives of the carburized gear under all load conditions are significantly improved. Under heavy load conditions, the carburized layer significantly reduces the fatigue damage mainly due to the benefit to inhibit the accumulation of plasticity. Influence of the residual stress is also investigated. Under the nominal load condition, compared with the residual stress-free case, the existence of the tensile residual stress causes remarkable deterioration of the rolling contact fatigue life while the compressive residual stress with the same magnitude leads to a moderate growth of the rolling contact fatigue life. As the load becomes heavier when plasticity becomes notable, the influence of the initial residual stress on the life is somewhat weakened.

2018 ◽  
Vol 777 ◽  
pp. 366-371
Author(s):  
Takuto Yamada ◽  
Koshiro Mizobe ◽  
Katsuyuki Kida

A new surface treatment, wide peening cleaning (WPC), was developed to improve fatigue strength of steels using shot peening and sandblast technologies. The combination of induction heating (IH) and WPC is expected to introduce higher compressive stress on the steels than single IH or single WPC. We investigated effect of IH and WPC on rolling contact fatigue life of 13Cr-2Ni-2Mo stainless steel. Vickers hardness and residual stress measurements, and RCF life evaluation using the Weibull distribution were carried out. It was found that the residual stress was introduced by WPC near the surface to improve life fatigue


2016 ◽  
Vol 851 ◽  
pp. 346-351
Author(s):  
Li Hua Fu ◽  
Jian Yang ◽  
Yue Zhang ◽  
Hua Song ◽  
Wei Li

Wheel/rail rolling contact fatigue is one of the most complicated and urgent problems of the key techniques of railway system, and seriously influences the operational safety. A finite element (FE) model of wheel/rail rolling contact of curve negotiation is established based on the single-layer track dynamic model, which is considering the effect of rail straightening residual stress, the actual wheel tread and the elastic support of rail track bed. The nominal stress approach is applied to study the rail rolling contact fatigue life with two residual stress-state conditions. Results show that the distribution of rolling contact fatigue life on the surface of rail head presents obvious peaks and troughs with a specific wavelength in the longitudinal direction, which are approximately corresponding to the peaks and troughs of the contact force. Meanwhile, the rail rolling contact fatigue life firstly increases and then decreases while the running speed varying from 150 to 250 km/h, and decreases while the axle load varying from 13 to 17 tonnes which do not fully show a linear law.


2000 ◽  
Author(s):  
Salah R. Agha ◽  
C. Richard Liu

Abstract It was shown earlier [Agha and Liu, 1998, 1999, 2000] that different cutting conditions, within superfinish hard turning, would lead to significantly different rolling contact fatigue lives. In this study, residual stresses were measured. The rolling contact fatigue life was then modeled using a maximum modified equivalent stress that takes residual stresses into account. It is seen that the maximum modified equivalent stress is a better predictor than the maximum Hertzian stress, but, still not accurate, given the consistent repeatability of the tested workpieces [Agha and Liu, 2000]. The difference in the nature of residual stresses produced by grinding and hard turning is used to show why the inclusion of the maximum modified equivalent stress, its location and the volume at risk, improves the power of the model to predict the rolling contact fatigue lives of the hard turned surfaces. This model is the best up to date for predicting the fatigue life of a surface, especially when residual stress is a factor.


Author(s):  
Y. B. Guo ◽  
A. W. Warren

The characteristics of residual stress (RS) profiles and their effects on rolling contact fatigue life for precision turned and ground surfaces with a white layer (WL) are very controversial. The key findings of this study are: (a) The basic RS profiles by a sharp tool can be fundamentally changed by a turned WL but not a ground WL; (b) The hook shaped RS profile of a turned surface may have about 40% more fatigue life than a ground one; (c) The white layer may reduce fatigue life as much as 7–8 times despite the deep compressive RS in the subsurface.


1982 ◽  
Vol 104 (3) ◽  
pp. 330-334 ◽  
Author(s):  
A. H. Nahm

Accelerated rolling contact fatigue tests were conducted to study the effect of grain flow orientation on the rolling contact fatigue life of vacuum induction melted and vacuum arc remelted (VIM-VAR) AISI M-50. Cylindrical test bars were prepared from a billet with 0, 45, and 90 deg orientations relative to billet forging flow direction. Tests were run at a Hertzian stress of 4,826 MPa with a rolling speed of 12,500 rpm at room temperature, and lubricated with Type I (MIL-L-7808G) oil. It was observed that rolling contact fatigue life increased when grain flow line direction became more parallel to the rolling contact surface.


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