Search Results

Helical gears in manual transmission are designed based on static loading. Sometimes these gears are subjected to impact during misuse events such as sudden engagement and disengagement of clutches, inappropriate shifting of gears, while vehicle is negotiating different maneuvers. These misuse events call for the need to consider the study the gear strength under impact loading in design phase. In this paper, attempt is made to evaluate stresses in the gear root under impact using the dynamic implicit algorithm available with commercial Finite element analysis (FEA) software Abaqus. Dynamic analysis is run for duration of few milliseconds to capture both impact and rebounding events. First gear pair, which is generally heavy loaded among all gear pairs, is considered for simulation. Initially, static analysis is performed for different pitch positions of one mesh to find out the most critical pitch position in which stresses in fillets reach their peak values.

Scuffing is an instantaneous failure which occurs when the meshed gear flanks undergo adhesive wear under extreme operating temperatures at medium- or high-speed conditions. It is one of the common failures in transmission gears, which tend to operate under long-duty cycle hours. The tip and the root regions often experience higher contact pressures because of the loading and surface curvature. These higher pressures, coupled with higher sliding velocities and heat generation, make the tip and root regions in the gear susceptible to scuffing. Gear geometry, material composition and lubricant properties influence scuffing. A balanced gear tooth design with lower sliding velocities is often chosen as an approach to avoid scuffing. However, in the current scenarios of transmissions with high power density requirements, achieving a balanced gear tooth design is rare. Lubricants with higher viscosity avoid scuffing, but have adverse effects on the transmission efficiency.