Comparison of Crack Detection Performance of Low and High Contact Ratio Spur Gears

Abstract

This paper discusses the possible early crack detectability performances of low contact ratio (LCR) and high contact ratio (HCR) spur gears. CAD models of the LCR and HCR gears are created using the rack cutter type tool. Static bending stress analyses are performed to define the starting point of the cracks and crack propagation analyses are conducted to define the realistic crack paths. Using the healthy and cracked gear geometries, the single tooth stiffness (STS) and the time-varying mesh stiffness (TVMS) of the LCR and HCR gears are calculated numerically. A six degrees of freedom dynamic model of the single-stage gear system is proposed. Dynamic force variation of the LCR and HCR gears are calculated by using the dynamic model. Statistical failure indicators, which are kurtosis, RMS, crest factor, mean, standard deviation, and variance, are used for the determination of the crack in the early stage. The results show that all statistical indicators increase with the increase in the crack length. The statistical indicators increase more for LCR gears than for HCR gears. Although HCR gears have many advantages over LCR gears, it has been determined that their crack detection capacity is lower than that of LCR gears.

Keywords

• dynamic analysis
• LCR and HCR gears
• mesh stiffness
• crack propagation
• gear health diagnostics and monitoring