The paper presents a method for investigating the bending stress at the critical section of ‘Asymmetric Involute Spur Gear’. Profiles of an asymmetric gear tooth on drive side and coast side have different pressure angles. The method ISO/TC- 60 has been used to theoretically calculate the bending stress at the critical section of this gear. The determination of the tooth form factor, stress concentration factor, critical section parameters and contact ratio have been accomplished for each set of gear. The gears with different pressure angles have been modeled by using CATIA V-5 R15 software to carry out FE analysis using ANSYS 14.5 software. A 3D photoelasticity method has been used to experimentally find out the stress at the critical section of symmetric involute spur gear and asymmetric involute spur gear. A comparative analysis between theoretical method, FE method and experimental method to determine bending strength of asymmetric involute spur gear has been carried out. The percentage increase in bending strength of the asymmetric gear has been estimated. The weight comparison between symmetric and asymmetric spur gear has been carried out for different combinations of pressure angle, module and number of teeth. A substantial weight reduction has been achieved by using asymmetric spur gear instead of symmetric spur gear.

Gears are wheels having peripheral teeth around its circumference that engage with another wheel to transmit the motion and hence power. Nowadays, gear design has become a complex and pervasive subject. The process of gear design aims at higher power transmission with a driving system having smaller overall dimensions that can be constructed with optimum cost, low vibration, noise and durability. It is very necessary to revisit the new gear designs in order to enhance the performance requirements like load carrying capacity, endurance strength, speed, etc.

The gears are invariably designed to satisfy two main criteria: first is the root bending stress resistance which is analog to the cantilever effect of tangential load on gear tooth; and the second one is the flank Hertzian stress resistance which is the resistance of the tooth flanks against the surface rupture when transmitting the tangential load. Figure 1 shows the failure of gear either by bending stresses or contact stresses.

Mechanical Engineering Journal, Asymmetric gear, Finite element method, Photoelasticity, Stress freezing, Parametric analysis.