渐开线直齿轮弹流润滑条件下的多轴疲劳寿命预估

Multi-Axial Fatigue Lifetime Model for Involute Gear under EHL Lubrication Conditions

本文中基于弹流润滑分析和次表面应力建立了渐开线直齿轮多轴疲劳寿命计算模型.相对于传统的单轴疲劳模型,考虑了齿轮固定点的应力历史和材料属性对疲劳寿命的影响,并可以得到齿轮在完整啮合过程中的寿命分布.首先建立齿轮的有限长弹流计算模型,得到齿轮啮合过程中的油膜压力和油膜厚度,再根据油膜压力计算出次表面的应力分布;通过分析齿轮计算区域随啮合过程移动的关系,得到固定点的应力历史,再根据基于应力历史的多轴疲劳寿命模型对齿轮的完整啮合过程进行寿命预估.计算分析了不同粗糙度幅值对轮齿各点寿命大小和分布的影响.研究表明:齿面粗糙度对疲劳寿命的影响显著,随着粗糙度幅值的增大,表层下最大应力向齿面移动,导致低疲劳寿命区向齿面发展且逐步扩展到整个单齿啮合区;而表面粗糙度降低到一定程度则对疲劳寿命的影响变得不明显.

This study presents a multi-axial fatigue model to predict fatigue lifetime of involute spur gear considering the elastohydrodynamic lubrication conditions and subsurface stress distributions. The proposed model considered the effect of both the stress history of certain point under tooth surface and material properties, and obtained the fatigue lifetime distribution of entire gear contacts. Firstly, the finite line-contact elastohydrodynamic lubrication model of the involute spur gear was established and the pressure distribution, oil film thickness and subsurface stress were obtained. Then, by analyzing the relationship between the movement of computational domain and the process of gear contact, the stress history of certain point in tooth was obtained. Finally, the gear fatigue lifetime of complete meshing process were predicted with multi-axial fatigue model based on the stress history. The results show that tooth surface roughness had a significant effect on gear fatigue lifetime. With the increase of the amplitude of surface roughness, subsurface maximum stress moved to the teeth surface, which resulted in the development of low fatigue lifetime region to the teeth surface and further extension to the entire single tooth meshing area; however, it had little effect on gear fatigue lifetime if the surface roughness reduced to a certain extent.