Noise Reduction in Two Wheeler Gears Using Austempered Ductile Iron 2003-32-0041

Gear noise can be attributed to several reasons such as gear design parameters, gear material used etc., Owing to design, spur gears during operation produce noise. A change in gear design to helical would reduce the noise, but at the cost of an increase in friction as in operation it produces an axial thrust. A more economic and effective way of noise reduction in gears would be to go in for a material, which has good damping characteristics in order to reduce the noise levels significantly.

A new member of the cast iron family, Austempered Ductile Iron (ADI), is a heat treated Spheroidal Graphite Iron(SGI). The microstructure exhibits ausferritic structure with a high volume of carbon-enriched austenite and nodular graphite. This offers the gear designer a combination of manufacturing flexibility, high strength, toughness, low weight, excellent fatigue strength and wear resistance. These properties are present along with good damping capacity and machinability. The contributions of the authors towards the development of ADI as one of the most suitable material for a two-wheeler automotive gear are presented in this paper. A specific gear was chosen for the study where noise reduction was of primary concern. ADI thus developed has been evaluated for mechanical properties like tensile strength, impact strength etc., Extensive metallographic examination and experiments has been done to substantiate that the graphite nodules in ADI cushions vibrations, as they are transmitted through the gear. The paper describes the work done to develop ADI from a commercial SGI. The experiments carried out on one of gear in the two-wheeler has shown reduction in gear noise level. The heat treatment cycle is being optimized to obtain the maximum level of noise reduction. This proves that ADI possess significant damping properties and helps in gear noise reduction.