Effect of Change of Spur Gear Tooth Parameters on Bending and Contact Stresses

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Addis Ababa University


The bending and surface stress of the gear tooth is considered to be one of the main contributors for the failure of the gear in a gear set. After the investigation of shot peening to increase the tooth bending strength and surface durability in gears, the surface roughness generated during shot peening leads to macro and micropitting is now considered the dominant restriction on gear life and performance. Thus, analysis of stresses has become popular as an area of research on gears to minimize or to reduce the failures and for optimal design of gears. This thesis investigated the effect of tooth parameters monitoring the stresses induced on spur gear by optimizing face width, root fillet radius, and number of teeth relative to weight of spur gear set. The involute profile of Spur gear has been modeled and the simulation was carried out for the bending and contact stresses. To estimate bending and contact stresses, 3D models were generated by modeling software CATIA V5r16, simulation was done by finite element software package ANSYS 12.0, and optimization was done using Design Expert Dx7 numerical optimization method. Analytical method of calculating gear bending stresses uses Lewis and AGMA bending equation. For contact stresses Hertz contact equation are used. The Study was conducted by varying the face width, number of teeth and root fillet radius to find its effect on the bending and contact stress of spur gear. It was therefore observed that the maximum bending stress and contact stress decreases with increasing face width, number of teeth and root fillet radius relative to spur gear set weight. Using the Design expert software Dx7 the optimal points were selected at face width 37.24mm, root fillet radius 3mm, and number of teeth 22.At these value contact stress was reduced from 389.31Mpa to 294.56Mpa (24.34%) and bending stress was reduced from 105.14Mpa to 49.65Mpa (52.80%).So that, it is recommendable to use optimal values of tooth parameters during design work to reduce stresses. It means stress reduction results in better tooth root load capacity, micropitting resistance, prolongs gear service life.



Mechanical Design Stream