| Gear transmission is a universal transmission mechanism in mechanical transmission,and it has been widely used in engineering field.The performance and efficiency are greatly depending on the integrity of the gear structure.Most of the existing literatures don't study the dynamic response of fault gear system,and great progress has been made in the research.However,the dynamic behavior analysis of gear with fault defects isn't thorough enough.Therefore,the study of the influence of the gear fault on the dynamic response from the simulation point of view is of great significance to the gear fault monitoring,identification and diagnosis of the gear system.In this paper,the influence of the tooth root crack on the gear system is analyzed and a spur gear transmission system is studied.By establishing the finite element model of the gear pair with cracks and the fatigue crack growth model of the gear,this paper researches coupling relationship between fatigue crack propagation and the contact dynamic load of the tooth.The main work carried out as follows:(1)By extracting the PHILSM value of the crack path of the fatigue crack propagation model of the gear,the structure of the crack is completed,and the finite element model of the crack gear pair is established.The simulation results show that the existence of the crack reduces the meshing stiffness of the tooth and the contact dynamic load of the tooth,which leads to the change of the dynamic response.(2)Through the extended finite element(XFEM)method,the fatigue damage evolution parameters are obtained,and the fatigue crack propagation model of the gear is established.Through the finite element model of cracked gear pair,the amplitude variation curve of meshing contact load is obtained,and the changing process of the contact position along the tooth profile is deduced through the tooth profile normal method.The DLOAD subprogram is applied to realize the boundary condition of meshing dynamic load.The crack growth trajectory is simulated,and then the PHILSM value is extracted for the next step crack surface configuration of the finite element model of the gear pair with cracks.(3)The contact load obtained from the finite element model of the cracked gear pair is established to relate to the fatigue crack growth model of the gear,and The relationship between the PHILSM value obtained through the fatigue crack propagation model of the tooth and the finite element model of the cracked gear pair is established.Then the interaction between dynamic response of gear and fatigue crack propagation is analysised.It is found that the mesh stiffness and contact dynamic load of the tooth root are smaller after the crack occurs at the root part,and the effect is more obvious with the expansion of fatigue crack.The crack direction of gear tooth root extends to the direction of flange,extending to the root of tooth at the late stage of expansion,which generally presents the trend of tooth root extension towards the other side of gear. |
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