Fatigue failure analysis of spur gear under moving load

Abstract

This paper is prepared to analyze the crack propagation by developing a pointed moving load condition. The moving load from lower point tooth contact (LPTC) to high point tooth contact (HPTC) is applied on the gear flank, where the maximum load is acted on the pitch-point of the tooth flank. Different models of gear, taking a three teeth sector model (TTSM), are developed for different backup ratio (BR) of 0.3, 0.5, 0.8, 1.5 & 3.3 and initiating the initial crack (IC) length of 0.1 mm, 0.25 mm & 0.5 mm at orientation of critical planes for shear model oriented at 180° at the root region of the tooth. The finite element analysis (FEA) software - ANSYS is used to study the problem statement. The arbitrary crack method is used to initiate the crack presence in gear flank. The Paris law method is applied in separating morphing and adaptive remeshing technology (SMART) crack growth setup in static structural module of ANSYS, which helps in evaluation of number of cycles with crack extension length. The number of life cycles, crack extension length and crack propagation path are analyzed and their graphs are plotted to analyze the situation. From current study, the effect of rim thickness on the life cycle is studied when the point load is applied movable from LPTC to HPTC. It is observed that by having thin rims, the number of cycles of gear increases, but its failure is catastrophic that it can fracture other parts, mounted with gear. Although, higher backup ratios or larger rims have lower number of life cycles, but it will never lead to the catastrophic failure of the gear.