Effect of Rim Thickness on Bending Stresses in Low Addendum Large Spur Gears

A finite element based approach is used for determining the effect of gear rim thickness on tooth bending stresses in low addendum large spur gears. These gears are used in cement plants, sugar mills, ball mills, coal mills, kilns, grinding mills, copper converters, and anode furnaces, etc. A program is developed using ANSYS Parametric Design Language (APDL) to generate 1, 3, and 5 tooth segments of a large spur gear. A controlled meshing approach is developed using free and mapped meshing capabilities of ANSYS to generate two-dimensional and three-dimensional finite element models of the gear tooth segments. The controlled meshing approach employed here has the following advantages: it prevents high stresses at load location, avoids too many elements in the low stressed region, and generates a fine mesh in the fillet regions of the loaded gear tooth. The finite element models are analyzed in the position of Highest Point of Single Tooth Contact (HPSTC). The two and three-dimensional models of 1, 3 and 5 tooth segments are analyzed by varying β, which is the ratio of rim thickness to tooth height of the gear. The effect of web on stresses is studied in the 3-D models. Equivalent (von Mises) and bending stresses are obtained for different values of β in various models. Using a program written in APDL the gear tooth profile and rim surface bending stresses are arranged in the form of tables using Microsoft Excel and plots are generated using the capabilities of MATLAB program. Maximum bending and maximum von Mises stress plots are generated for varying values of β in two and three-dimensional models. Also, plots are generated to compare maximum stresses in 1, 3 and 5 teeth models.

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