Effect of Coefficient of Asymmetry on Strength and Contact Ratio of Asymmetric Helical Gear

Abstract

A gear is a rotating machine part having cut teeth, which mesh with another toothed part in order to transmit torque. Gears may be spur, helical, bevel or worm in which Helical Gear is most common type of gear used in engineering applications. The increased in performance requirement such as high load carrying capacity, high speed, high reliability and long life leads to new design of gear. So as to fulfill above demand here we used a concept of asymmetric gear profile in which two different pressure angles are assign to two faces of gear tooth. In literature it shows that increased in drive side pressure angle shows improve in strength of spur gear. In this paper we find the effect of coefficient of asymmetry on strength and contact ratio of different helical gear pairs having gear ratio equal to one and transmit same power. All the gear pair are design in Cre-O parametric 2.0 and the analysis is carried out in ANSYS workbench 16.0. Results from numerical analysis shows that as coefficient of asymmetry and helix angle increases Von-Mises stress and total deformation decreases. To validate the results from numerical analysis experiment stress measurement is done using digital strain indicator in which a strain gauge (UFLA-1-350-23) is mounted at the root of the gear and strain is calculate for different loads. In further study we find the effect of coefficient of asymmetry on contact ratio of helical gear pairs, here it shows that decreased in coefficient of asymmetry leads to increased contact ratio.