Influence of finite element model, load-sharing and load distribution on crack propagation path in spur gear drive

The tooth fracture is one of the main failure modes in spur gear drives which is due to the bending fatigue load acting on the spur gear tooth during power transmission. The fatigue load initiates the crack at the tooth root region and propagate along the least resistance path which leads to complete tooth/rim fracture. The crack propagation path is influenced by the magnitude of the stress intensity factor (SIF) and its location along the face width at the crack front. Generally, the prediction of crack propagation studies was carried out using a three-dimensional (3D) finite element (FE) model in literature with uniform / parabolic load distribution on the contact line along the face width. An attempt has been made to explore the finite element (FE) model and the load distribution on the SIF for the given crack size. Two different 3D models namely three teeth sector model (TTSM) and Single tooth sector model (STSM) are developed with the initial crack with the size of 1 mm at the location of maximum principal stress in the fillet region. The load is moved from lowest point of tooth contact (LPTC) to highest point of tooth contact (HPTC) in the case of STSM whereas in TTSM the loads are applied simultaneously to the leading and trailing teeth whenever there is a double pair contact established as per the gear kinematics. The results are compared with the published results and found that the STSM and TTSM predict a deeper crack propagation path. The results of the FE models are compared with the single tooth fatigue load test results and found that the simulation results with actual load distribution predicting almost similar crack path as that obtained from the experiment.