The Research On Pitting Failure Mechanism And Vibration Response Of Gear

The gear transmission system has the advantages of an accurate transmission ratio,a long service life,high transmission efficiency,and reliable operation.It is widely applied in fields of automotive,aerospace,and marine.Due to poor lubrication,overload,manufacturing errors,and installation errors,the gear is prone to pitting,cracking,and other failures.The maintenance after failure is difficult,so it is important to conduct early fault diagnosis for the gearbox.Gear pitting failure is one of the main forms of gearbox failure,and the study of pitting failure can provide a theoretical basis for gearbox fault diagnosis.In this paper,the mechanism of tooth surface pitting is analyzed,and the vibration response of the gear system under pitting failure is studied with the gear transmission system as the research object.The main research contents of this paper are as follows:Firstly,the mechanism of fatigue pitting is studied.A simplified contact model of the gear pair is established,the contact pressure distribution of the gear teeth is analyzed by elasto-hydro-dynamic lubrication theory,and the process of micro-pitting formed by tooth cracks is investigated based on the extended finite element method.The pitting pattern obtained from the simulation is compared with the experimental pitting pattern to verify the validity of the crack expansion model.Secondly,for the pitting failure of spur gears,an irregularly shaped pitting model is proposed based on the pitting shape obtained from the finite element simulation result and the experimental result,and the pitting model has an uneven bottom feature.Based on the potential energy method,the equations for calculating the time-varying meshing stiffness of gears under pitting failure are derived based on the improved transition curve and considering the inter-tooth coupling effect during gear meshing.And a randomly distributed tooth surface pitting evolution model is established to evaluate the effect of slight pitting to severe pitting failure on the meshing stiffness.The finite element method is also adopted to verify the validity of the proposed model.Then,considering the advantages of smooth transmission,low noise,and high load carrying capacity of helical gears,the slicing method is adopted to investigate the pitting failure of helical gears.The helical gear is sliced along the tooth width,assuming that the slices are small enough to treat each slice as a spur gear to calculate the time-varying mesh stiffness,and then the mesh stiffness of the helical gear is obtained by integration.Finally,the vibration response of the gear system under pitting failure is analyzed.A multi-degree-of-freedom dynamics model with stiffness-damping coupling is developed for both spur gears and helical gears,taking into account friction,transmission errors,and other factors.The mesh stiffness at different degrees of pitting failure is brought into the set of dynamics equations,and the vibration acceleration response of the gear pair is solved to analyze the time and frequency domain characteristics of the fault signal.The experimental fault signals are applied to verify the simulated signals and test the validity of the gear dynamics model.Different statistical indicators are adopted to study the time-domain signals,and the most fault-sensitive indicator is selected as the evaluation indicator.