Analysis Of Roughness Effect For Heavy-duty Gear Transmission

With the improvement of the level of economic development and technology, heavy-duty gear plays an increasingly important role in the mechanical transmission. Scholars done a lot of work at home and abroad in gear transmission mixed elastohydrodynamic lubrication research, but most of the research on light, medium load condition, in heavy-load gear transmission mixed lubrication research reports are in press.On tooth surface roughness effects, researchers often in a micro convex or tooth surface artificial hypothesis assumes that tooth surfaces are distributed in the rough waves sine (cosine), although this largely reduced the calculation difficulty, but with the physical distribution of tooth surface roughness has great discrepancy. As a result, in this paper, with the aid of Qingdao university of science and technology of roughness profile measuring instrument, first of all, have had more groups of specimens with different grain direction of surface roughness, and then using Fourier nonlinear transform fitting out surface roughness function and its superimposed to the oil film thickness equation, and gear drive mixed elastohydrodynamic lubrication model is established. Based on this model, while maintaining the premise roughness values fixed by changing the oil viscosity were76group numerical theoretically explores the impact of oil viscosity on transmission gear contact stress overloads; Later, by changing the rough numerical, respectively for tooth surface coarse grain direction is vertical and horizontal two cases, conducted a series of40contrast numerical calculation, further discusses the size and texture direction of tooth surface roughness oil film thickness and the influence of contact fatigue stress. This paper obtained the following conclusions:(1) With the current gear contact strength design based on Hertz compared distribution, rough tooth surface pressure distribution and the thickness of the oil film is volatile, sub-surface contact area show the obvious stress concentration. Roughness value is larger, the volatility and the degree of stress concentration is more acute, and the vertical texture intensity than transverse rough gear tooth surface rough tooth surface texture.(2) On the premise of other parameters are fixed, the contact stress of gear tooth and decreases as the lubricant viscosity. But viscosity when above a certain value, the contact stress of gear tooth hardly changes with oil viscosity.(3) When the rough texture of the longitudinal tooth surface average oil film thickness is smaller than the tooth surface smooth film thickness values; The average oil film thickness and transverse coarse texture gear tooth surface smooth rather than the corresponding value of contact. Tooth surface roughness value, the greater the rough and smooth and the greater the difference of tooth surface oil film thickness. For example, when the tooth face roughness of sigma >0.35(microns),for the same lubricating oil viscosity, lateral tooth surface texture roughness average oil film thickness of film thickness is bigger than vertical texture coarse gear tooth surface by more than10%.(4)As long as there is the presence of roughness,whether it is transverse texture or longitudinal sub-surface tooth contact area times the maximum shear stress is greater than the corresponding values of smooth contact. When the tooth face roughness of sigma0.06or less (microns),stress difference caused by different tooth surface texture is very small; When the sigma (microns)>0.06, the main shear stress between the maximum and the tooth surface roughness is almost a linear relationship; And for the same roughness value, transverse rough texture on the surface of the tooth contact stress of tooth surface stress value is less than the longitudinal rough texture.At the end of the article separately established the tooth contact stress and the lubricating oil viscosity and the quantitative relationship between the tooth surface roughness, and gives the transverse rough texture of tooth surface lubrication effect is better than the longitudinal rough texture on the surface of the tooth research conclusion.The innovation point of this article is based on the measured surface roughness data this paper discusses the overloading the roughness of the gear transmission effect, make the results more practical significance. Deficiency is larger when the roughness value when the numerical convergence.