Contact And Thermal-Elastic Analysis Of Gears With Flank Modification

Gears play an essential role in the transmission of power and movement of mechanical system. Their transmission performance directly affects the service life, energy consumption, and noise and vibration of mechanical products. With rapid development of industry, high-speed and heavy load has become main tendency for mechanical transmission, which requires gears with higher contact fatigue strength, scuffing resistance and better transmission performance.Recently, surface modification has been used to improve the working performance of gears. Much superior compared with conventional lead profiles, logarithmic profile was first applied to spur gears modification by Bergseth. Inspired by this research, this thesis offered an in-depth analysis of logarithmic modification on the whole tooth surface for manufacturing of spur gears, and further on helical gears. Tooth contact and thermo-elastic analysis via Matlab were then carried out to evaluate the modification results of gear modification.Part 1 described the significance of gears with respect to modification and mechanical and thermal-elastic properties analysis, and reviewed the research progress of gear modification technique, tooth contact analysis and thermal-elastic analysis.Part 2 applied the logarithmical modification on spur gears and established the surface coordinate equation of logarithmic crowned tooth for manufacturing. On the basis of the contact mechanics model, corresponding Matlab programs were developed to calculate the distributions of contact stress and von Mises stress field inside the subsurface layer at any meshing position. The numerical results of some typical engaging locations were analyzed and compared.Part 3 applied the logarithmical modification on helical gears. In view of gears with low and high contact ratio, the contact line length was calculated respectively, based on which the surface coordinate equation of logarithmic crowned helical gears, the contact mechanics model and fatigue life model were established. Matlab Programs were developed to compute the relative fatigue life, the contact stress and the Mises stress field at any engaging position to reveal the influences the logarithmic modification has on the fatigue resistance of teeth surfaces.Part 4 established the heat conduction equation and the basic equations of thermo-elasticity with respect to spur gears with logarithmic modification. Thermo and thermo-elastic fields of spur gear at any meshing position were then obtained using the FFT and IFFT techniques, and their variations with torque and rotational speed were examined.Part 5 summarized the major work in this thesis and proposed other crucial issues that require future research endeavor.