Dynamic Modeling Of Gear System With Fault And Calculation Of Mesh Stiffness With Cracked Tooth

The gear transmission systems are widely applied to transmit power, torque andhigh rotational speed, and change the direction of rotational motion. The performanceand efficiency are greatly depend on the integrity of the gear structure. Hence, healthmonitoring and fault detection in geared systems have gained much attention. Often,as a result of inappropriate operating conditions, application of heavy load beyond thedesigned capacity or end of fatigue life, gear faults frequently occur in practice. Whenfault happens, gear meshing characteristics, including mesh stiffness that is one of theimportant dynamic parameters, can be affected. This sudden change in mesh stiffnesscan induce shock vibration as the faulty gear tooth passes through the engagementzone. In this study, a finite element model representing the crack at the tooth root of aspur gear is developed. The theory is applied to investigate the effect of differentcrack sizes and the corresponding change in mesh stiffness. In addition, a lumpedparameter model is formulated to examine the effect of tooth fault on gear dynamicresponse.Considering the present background of gear failure mechanism and diagnosticmethods, this work studies the effect of the tooth root crack on the meshing stiffnessbased on the study of the time-varying meshing stiffness of the spur gear. The gearmeshing stiffness calculation model is established for crack associated with the pitchcircular and the effect of crack location on the teeth meshing stiffness is studied. A sixdegrees-of-freedom gear system dynamic model is established and the dynamicperformance of the fault gear under different working conditions are obtained.The main work carried out as follows:①The energy method is used to calculate the normal gear tooth root crack gearsof time varying mesh stiffness, and the depth of the crack on the tooth meshingstiffness is discussed. The finite element models of normal gear and gear with toothroot crack are established, the gear mesh stiffness and energy method are calculatedto verify the contrast; through the establishment of a more realistic curved tooth rootcrack gear finite element model, the linear assumption of the tooth root crack meshstiffness calculation error is analyzed.②The gear mesh stiffness calculation model for the crack associated with thepitch circular is established based on the analysis of the existing tooth root crackstiffness model. The gear meshing stiffness for pitch circle crack with different depths are calculated using this new model and the effect of pitch circle crack depthon the gear mesh stiffness is evaluated. The results are compared with that of thegear with tooth root crack. The finite element model of pitch circle crack isestablished and the meshing stiffness is calculated to verify the accuracy of the gearmeshing stiffness calculation model for pitch circle with crack.③A six degrees-of-freedom model of a single-stage spur gear dynamic systemisestablished and the fault excitation parameters are introduced. The dynamicresponses of the normal and fault gear under different operating conditions are solved.The time-domain and frequency domain analysis methods are applied to analyze thedynamic simulation results and the law of the impact between the fault and vibrationresponse are obtained. The gear fault test rig is designed and built and thesimulation results are compared with experimental results.