Study on contact fatigue of a wind turbine gear pair considering surface roughness

Abstract

Contact fatigue issues become more and more crucial in gear industry as they significantly affect the reliability and service life of associated mechanical systems such as wind turbine gearboxes. The contact fatigue behavior is mostly determined by the mechanical properties of materials and stress fields near the contact area, which is further influenced by the lubrication and surface roughness due to pressure fluctuations. In this study, a numerical model incorporating the lubrication state, tooth surface roughness, residual stress, and mechanical properties of the material is developed to determine the contact fatigue behavior of a megawatt level wind turbine carburized gear. The variations of the hardness and residual stress along the depth were characterized by the Vickers hardness measurement and X-ray diffraction test, respectively. The elastohydrodynamic lubrication theory was applied to predict the contact pressure distribution, highlighting the influence of the surface roughness that stemed from the original measurement through an optical profiler. The stress histories of the studied material points during a complete contact loading cycle were fast calculated using the discreteconcrete fast Fourier transformation (DC-FFT) method. Modified Dang Van diagrams under different working conditions were determined to estimate the contact fatigue failure risk. The effect of the root mean square (RMS) value of the surface roughness on the failure risk at critical material points were discussed in detail. Results revealed that the surface roughness significantly increases the contact fatigue failure risk within a shallow area, and the maximum risk appears near the surface.

A Review on Micropitting Studies of Steel Gears

“…As for the results, Figure 9 illustrates the risk of the contact fatigue along the depth at the position where the maximum τ max is at peak value during the complete contact loading cycle within the calculation domain at the pitch point with different asperity conditions [63]. It reflects the fact that the increase of the surface roughness RMS makes the maximum index of the failure risk significantly rise, and its occurrence position gradually becomes shallower, reaching a depth of about 0.05 mm when the RMS rises to 0.5 µm, where the micropitting is apparently more likely to occur.…”

A Micropitting Study Considering Rough Sliding and Mild Wear

“…The development of deterministic elastohydrodynamic lubrication (EHL) models [12] and discrete convolution and fast Fourier transform (DC-FFT) algorithm [13] provides effective ways for better modelling of lubricated contact. The mixed EHL model developed by Zhu and Wang [14] is widely accepted in many EHL contact fatigue studies [15][16][17]. These models solve for the pressure and the stress through the EHL approach, then evaluate the fatigue performance using multiaxial fatigue criteria.…”

Roles of microstructure, inclusion, and surface roughness on rolling contact fatigue of a wind turbine gear

“…The ratio of the fatigue limits ( τ −1 / σ −1 ) is usually regarded as an empirical value for fatigue evaluation, lying in the range 0.57 to 0.8 for steels. And the fatigue performances of wind turbine gears and roller bearings have been successfully evaluated with setting the ratio to 0.577. The ratio in the Dang Van criteria is also set as 0.577 in this study.…”