Model and nonlinear dynamic characteristics analysis of screw-nut joint considering coupling effect of wear and vibration

Wear of rolling elements can produce a huge impact on the mechanical properties of screw-nut joint, and is one of primary causes resulting in the accuracy degradation or even failure of kinematic pairs. Many mechanical models have been constructed to investigate the vibration performance of rolling elements. But the wear influence is considered scarcely because of the complicacy of loading status and wear process. In this study, a novel wear prediction model can be proposed for screw-nut joint to overcome the above difficulty. An ultimate stiffness model can be constructed on basis of the wear model. The influences of running distance, external forces, preload, and structural parameters on wear performance are researched. A dynamic model of screw-nut joint with varying stiffness is constructed to carry out a detailed study on its vibration performance, particularly taking into account the coupling effect between wear and vibration. The influences of wear on the axial stiffness and vibration characteristics are studied based on the proposed model. Moreover, the change rules of axial stiffness and dynamic response under variable preloads are researched. The results indicate that the choice of parameters can produce an appreciable impact on the wear rate. The wear can result in the losses of stiffness and critical displacement of screw-nut joint. Although increasing the preload can improve the stiffness and the critical displacement, it also aggravates the wear degree. When the relative displacement between nut and screw is greater than the critical displacement, the balls with preload and axial force in opposite directions will be out of action, and the monotonic property of stiffness will also change. Due to the monotonicity of stiffness is not consistent before and after the critical displacement point, the amplitude-frequency curve presents a jumping phenomenon.