Research On Meshing And Vibration Characteristics Of Gear System With Crack And Spalling

Gear transmission system is the most important and reliable mechanical transmission,and it has an irreplaceable role.The reliability and the vibration performance of gear system have a direct influence on the noise and the lifetime of the whole machine.When the crack and the spalling appear in the gear,they may cause inestimable casualty and property losses.Thus,it is important to carry out a research on the gear meshing characteristic and the vibration characteristic of the gear transimission system considering the gear crack and spalling.In this paper,taking spur gear pair as the research object firstly,a spatial non-penetrating crack analytical model is established considering the effects of extended tooth contact and revise of the fillet-foundation stiffness.Simultaneously,taking the widely used of the helical gear into consideration,the analytical mesh stiffness calculation model for cracked or spalled helical gear pair is established.Moreover,the effects of different crack forms and different spalling size are considered.A distributed dynamic model of a helical gear is established,and the vibration characteristics of the cracked and spalled gear systems are analyzed.The main contents of the study are as follows:(1)Considering the effects of extended tooth contact and revise of the fillet-foundation stiffness,a spatial non-penetrating crack analytical model is established.Simultaneously,a spatial non-penetrating crack FE model is established,which is used to verify the correctness of the analytical model and analyze the equivalent stress,displacement and contact pressure under different crack forms through the powerful post-processing function in ANSYS.(2)Based on above foundation,the meshing characteristics of cracked helical gear are analyzed.An analytical model is established to quickly calculate the time-varing mesh stiffness(TVMS),contact stress and gear tooth root-bending stress.In addition,the corresponding FE model is established to verify the correctness of the analytical model.Because of the helical meshing force condition,the crack on the helical gear is along the dirction of contact line,so the crack propagation path is a spatial curve.The healthy helical gear analytical model is established firstly,and then the cracked helical gear analytical model is established.The corresponding FE models are established to verify the availablity of the analytical model.Contact stress and tooth root bending stress are the important component of the meshing characteristic,which are analyzed by the analytical method and the FE method.(3)Based on the slice method,an analytical mesh stiffness calculation model for spalled gear pair is proposed.And the the corresponding FE model is established to verify the correctness of the analytical model.At the same time,the effects of the spalling on contact stress and gear tooth root bending stress are analyzed,which are used to assess the carrying capacity of the gear.The effects of different parameters of spalling on meshing characteristic are studied,and the effects of multi-spalling on meshing characteristic are analyzed.(4)Distributed dynamic model of a helical gear is established,considering the the effects of the axis and bearing.TVMS of the cracked or spalled gear pair is introduced into the dynamic model,and the time-domain spectrum,frequency domain spectrum and instantaneous energy are used to analyze the effects of crack and spalling on vibration characteristics.The relationship between fault and the vibration response is found to provide theoretical basis for fault diagnosis.