Influence of Addendum Modification Factor on Root Stresses in Normal Contact Ratio Asymmetric Spur Gears

Document Type : Research Paper


1 Mechanical Engineering Department, Motilal Nehru National Institute of Technology, Allahabad, India

2 Research Scholar Department of Mechanical Engineering, Pondicherry Engineering college, Pondicherry, India


Tooth root crack is considered as one of the crucial causes of failure in the gearing system and it occurs at the tooth root due to an excessive bending stress developed in the root region. The modern power transmission gear drives demand high bending load capacity, increased contact load capacity, low weight, reduced noise and longer life. These subsequent conditions are satisfied by the aid of precisely designed asymmetric tooth profile which turns out to be a suitable alternate for symmetric spur gears in applications like aerospace, automotive, gear pump and wind turbine industries. In all step up and step down gear drives (gear ratio > 1), the pinion (smaller in size) is treated as a vulnerable one than gear (larger in size) which is primarily due to the development of maximum root stress in the pinion tooth. This paper presents an idea to improve the bending load capacity of asymmetric spur gear drive system by achieving the same stresses between the asymmetric pinion and gear fillet regions which can be accomplished by providing an appropriate addendum modification. For this modified addendum the pinion and gear teeth proportion equations have been derived. In addition, the addendum modification factors required for a balanced maximum fillet stress condition has been determined through FEM for different parameters like drive side pressure angle, number of teeth and gear ratio. The bending load capacity of the simulated addendum modified asymmetric spur gear drives were observed to be prevalent (very nearly 7%) to that of uncorrected asymmetric gear drives.


Main Subjects

[1] Buckingham E., 1988, Analytical Mechanics of Gears, Dover Publications, Inc.
[2] Kapelevich A., 2000, Geometry and design of involute spur gears with asymmetric teeth, Mechanism and Machine Theory 35: 117-130.
[3] Muni D.V., kumar V.S., Muthuveerappan G., 2007, Optimization of asymmetric spur gear drives for maximum bending strength using direct gear design method, Mechanics based design of structures and machines 35: 127-145.
[4] Yang S.C., 2007, Study on internal gear with asymmetric involute teeth, Mechanism and Machine Theory 42: 974-994.
[5] Muni D.V., Muthuveerappan G., 2009, A comprehensive study on the asymmetric internal spur gear drives through direct and conventional gear design, Mechanics Based Design of Structures and Machines 37: 431-461.
[6] Karat F., Ekwaro-Osire S., Cavdar K., Babalik F.C., 2008, Dynamic analysis of involute spur gears with asymmetric teeth, International Journal of Mechanical Sciences 50: 1598-1610.
[7] Costopoulos Th., Spitas V., 2009, Reduction of gear fillet stresses using one side asymmetric teeth, Mechanism and Machine Theory 44: 1524-1534.
[8] Alipiev O., 2011, Geometric design of involute spur gear drives with symmetric and asymmetric teeth using the realized potential method, Mechanism and Machine Theory 46: 10-32.
[9] Sekar P., Muthuveerappan G., 2014, Load sharing based maximum fillet stress analysis of asymmetric helical gear designed through direct design method, Mechanism and Machine Theory 80: 84-102.
[10] Mohan N.A., Senthilvelan S., 2014, Preliminary bending fatigue performance evaluation of asymmetric composite gears, Mechanism and Machine Theory 78: 92-104.
[11] Marimuthu P., Muthuveerappan G., 2016, Design of asymmetric normal contact ratio spur gear drive through direct design to enhance the load carrying capacity, Mechanism and Machine Theory 95: 22-34.
[12] Marimuthu P., Muthuveerappan G., 2016, Investigation of load carrying capacity of asymmetric high contact ratio spur gear based on load sharing using direct gear design approach, Mechanism and Machine Theory 96: 52-74.
[13] Thomas B., Sankaranarayanasamy K., Ramachandra S., Kumar S., 2018, Search method applied for gear tooth bending stress prediction in normal contact ratio asymmetric spur gears, Proceedings of the Institution of Mechanical Engineers Part C Journal of Mechanical Engineering Science.
[14] Shuai M., Shuai M., Geoguang J., Jiabai G., 2018, Design principle and modeling method of asymmetric involute internal helical gears, Proceedings of the Institution of Mechanical Engineers Part C Journal of Mechanical Engineering Science.