Finite Element Analysis to find bending stress analysis of the worm wheel of Winching Machine Gear Box

Mechanical Engineering

The worm and worm wheel is used in winch machine gearbox. During operation it was observed that the worm wheel fails due to load coming on the teeth. The failure starts at the central thickness of tooth and continues up to the root of the tooth. At the initial stage of failure, the tooth was going in plastic deformation and then crack was occurring at the central thickness. The failure occurred once within operational period of about 15 days. So the industry had to replace the worm wheel which was not cost effective. The material of worm is hardened steel, and the material of the wheel is phosphor bronze PB2 having approximate composition in percentages as (Cu = 85, Sn = 12, Zn = 0.3, Pb = 0.5, P = 0.4 and other = 2). The calculation of stresses of worm wheel at tooth thickness is a three-dimensional problem. Thus we can analyze the stress pattern by using 3D Photoelasticity techniques and finite Element analysis technique. Breakage is the ultimate type of gear failure. Bending loads on gear teeth usually cause the highest stresses at the root fillets and at the tooth profile/root fillet junctions. A gear tooth is a cantilever plate with tensile stresses on the contact side of the tooth and compressive stress on the opposite side. If the tensile stresses at the critical location are allowed to exceed the endurance strength of the tooth material, fatigue cracks will eventually develop and with continued operation, will ultimately progress to the point where the tooth will break away from the rim material.

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