Study of Impact Loading on Helical Gears using Finite Element Analysis 2013-01-1773

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. In the analysis, input shaft on which pinion is cut and driven gear are modeled and part of input shaft is included as stiffness matrix to reduce the computational time. Input shaft is constrained in all degrees of freedom and reactive torque is applied on driven gear wheel. Dynamic analysis is performed for critical pitch position obtained from static analysis. Variation of Stresses and tooth contact force with respect to time are evaluated from this analysis. In order to get smooth curves of results, results are obtained at very frequent time intervals. Further to quantify the intensity of impact, values of peak stresses during impact were compared against static stresses.