Investigation of the effects of gear tooth faults and damages on the dynamic behavior of non-standard gears

Gear faults and damages must be detected at an early stage. In this thesis, numerical methods have been developed for detecting cracks in standard and nonstandard gears in early stages. In this study, firstly standard and non-standard gear geometries are formed for four different rim thickness and four different pressure angles. Then, the static stress analysis was carried out to determine the starting points of the cracks and the maximum point of the stress was determined as the starting point of the cracks. Fatigue crack propagation analyzes were performed for gears whose crack starting point are determined. In this way, the direction of propagation of the crack was determined for different rim thicknesses. In addition, the number of cycles and da/dN graphs were obtained for all cases depending on the amount of crack propagation. Single tooth stiffnesses and mesh stiffnesses at each point on the involute curve were calculated using finite element analysis for different crack amounts for %0, %25, %50, %75 and %100. In order to detect the failures based on the amount of crack propagation, a six-degree non-linear dynamic model was prepared in MATLAB environment. As a result of finite element analysis, mesh stiffness and other gear parameters are given as input to dynamic model. By analyzing the gears in dynamic model with different crack amounts, different rim and pressure angles, dynamic transmission error and variation of vibration values on the bearings are obtained. The obtained dynamic transmission error and vibration signals are evaluated with the help of statistical error indicators and different fault ranges are determined for different standard and non-standard gears.