三维线接触微动界面疲劳寿命预测及断裂行为研究

Fatigue Life Prediction and Fracture Behavior Study of Fretting Interface at Three-dimensional Line Contact

工程机械中常用的连接结构由两个或多个零件紧密配合而成,在运行过程中接触的零件相互挤压的同时伴随有小幅相对滑动,易发生微动疲劳。微动疲劳主要分为疲劳裂纹萌生、疲劳裂纹扩展和快速断裂三个阶段,连接结构中的零件断裂可引起严重事故。现有的研究主要基于经过简化的二维平面应变模型,为了更清楚地了解微动疲劳的断裂机制,首先建立了微动条件下的三维线接触有限元模型,然后基于临界平面法分析了裂纹萌生寿命、位置和角度,最后基于线弹性断裂力学模拟了三维疲劳裂纹扩展过程。结果表明:在微动载荷的作用下,裂纹以一定倾斜角度在接触区域边缘处萌生,先沿着萌生方向逐渐扩展,当疲劳裂纹扩展至一定深度时,在循环体应力作用下,其方向逐渐变为垂直于接触表面,最终使试件断裂。裂纹萌生阶段的寿命远大于扩展阶段的寿命,占微动疲劳寿命的70%~80%。计算得到的疲劳寿命与文献中微动试验的寿命结果在2倍的分散带内,验证了该方法的有效性。该仿真分析方法可为连接结构的抗微动疲劳设计提供理论基础。

The connection structure commonly used in construction machinery is made up of two or more parts that are closely matched.During the operation,the parts in contact with each other are squeezed against each other and accompanied by a small relative sliding,which is prone to fretting fatigue.Fretting fatigue is mainly divided into three stages:fatigue crack initiation,fatigue crack propagation and rapid fracture.The fracture of parts in the connecting structure can cause serious accidents.The existing research is mainly based on the simplified two-dimensional plane strain model.In order to understand the fracture mechanism of fretting fatigue more clearly,a three-dimensional line contact finite element model under fretting conditions is first established.Then,the crack initiation life,location and angle were determined based on the critical plane method.Lastly,the three-dimensional fatigue crack propagation process was simulated according to the linear elastic fracture mechanics.The results show that the crack initiates at the trailing of the contact area at a certain inclination angle and firstly expands along the initiation direction.When the fatigue crack propagates to a certain depth,its growth path gradually becomes perpendicular to the contact surface under the action of the cyclic body stress,eventually breaking the test piece.The life of the crack initiation stage is much longer than that of the propagation stage,accounting for about 70%-80%of the fretting fatigue life.The calculated fatigue life is within a double dispersion band of the life results reported in the literature,which verifies the effectiveness of the method.The developed method can provide a theoretical basis for the anti-fretting fatigue design of the connection structure.