Calculation Of Mesh Stiffness For Faulty Gears And Analysis Of System Dynamic Characteristics

For gear systems operating in harsh environments,failures such as tooth root cracks,surface pitting,and gear tooth breakage are prone to occur.These failures can lead to significant economic losses or pose risks of safety accidents.Therefore,it is necessary to investigate the dynamic characteristics of gear systems under faulty conditions to provide theoretical support for engineering applications.In this thesis,a gear pair in a certain mechanical enclosed power transmission test rig is chosen as the research object.The time-varying mesh stiffness of the gear is calculated for three different conditions: healthy state,tooth root crack fault,and tooth tip chipping fault.Based on this,a dynamic model of the gear system is constructed.The influence of system parameters on the gear’s motion state of gear system at different rotational speeds is explored.Additionally,the dynamic response of the system is investigated under different types and severities of gear faults.The main research content and work are summarized as follows:(1)A calculation model for the mesh stiffness of healthy gears is established based on the energy method.The correctness of the proposed model is validated using the SIMPACK software solver.By establishing calculation models for gear mesh stiffness with crack faults and tooth tip chipping faults,the mesh stiffness of gears is calculated for different crack depths and dimensions of the chipped tooth portion.Furthermore,the influence of parameters such as the number of gear teeth,module,pressure angle,tooth tip height coefficient,and shaft hole diameter on the mesh stiffness is investigated using the calculation model for the mesh stiffness of healthy gears.(2)A dynamic model of the gear system,considering the coupling of bending and torsion,is established using the lumped mass method.In the modeling process,the influences of factors such as mesh stiffness,transmission error,and tooth backlash are considered,and key dynamic parameters of the gear system were calculated.Based on this gear system model,bifurcation diagrams of the system were obtained for different tooth flank clearances,damping ratios,and bearing support stiffness,and the effects of key parameters such as tooth flank clearance,damping ratio,and bearing support stiffness on the dynamic characteristics of the system were studied.(3)Based on the calculated mesh stiffness of gears with tooth root crack and tooth tip chipping,the dynamic response of the gear system under these two fault conditions is solved using the standard fourth-order Runge-Kutta method.The effects of gear fault types and fault severity on the dynamic characteristics of the system are studied.Additionally,based on the dynamic response results,the sensitivity of different indicators to the severity of the faults is analyzed from a fault diagnosis perspective.