Design and Stress Analysis of Spur Gear Tooth Profile Modification for Improved Bending and Contact Strength

Spur gears are among the most widely used power transmission elements in mechanical systems, and their load-carrying capacity is governed primarily by bending stress at the tooth root and contact (Hertzian) stress at the meshing surface. This paper presents a comparative study of four spur gear tooth profile configurations standard involute, modified addendum, profile shifted, and high pressure angle for a gear pair transmitting 10 kW at 1440 rpm with a module of 4 mm. Bending and contact stresses were calculated using the Lewis equation and AGMA standard methods, and validated using finite element analysis (FEA) in ANSYS Mechanical. Results show that profile shifting of the pinion tooth (addendum modification coefficient +0.3) reduces maximum bending stress by 18.1 percent and contact stress by 8.3 percent compared to the standard involute profile, increasing the factor of safety against bending fatigue from 2.68 to 3.27. The FEA results agree with AGMA standard calculations within 1.8 percent across all load conditions studied, confirming the validity of the analytical approach for preliminary gear design verification.