Effect of metal and polymer mating gears on the bending fatigue performance of asymmetric polymer gears

Abstract

The material of the mating gear influences the fatigue life of polymer gears. The bending fatigue characteristics of polyamide 66 asymmetric gears (34°/20° and 20°/34°) corresponding to steel–polymer and polymer–polymer material combinations were investigated. The performance of symmetric gear pairs (20°/20°) was determined to serve as a comparison. Quasi-static numerical simulations were performed in a finite element analysis tool to predict root bending stress, load sharing ratio, and tooth deflection. The bending fatigue strength of steel–polymer and polymer–polymer pairs of each test configuration was determined using bending fatigue tests. The load sharing ratio and root bending stress of polymer–polymer pairs decreased substantially compared to steel–polymer pairs. The extent of deflection-induced load sharing was greater in polymer–polymer pairs. The bending fatigue life of polymer–polymer pairs was lower than that of steel–polymer pairs owing to the higher operating temperature. In polymer–polymer pairs, polymer driving and driven gears increased the heat generated and diminished the heat dissipation to the environment. In steel–polymer and polymer–polymer pairs, the configuration with the highest bending fatigue strength was 34°/20° and 20°/34°, respectively. This divergence was caused by the increase in temperature difference between the two configurations for polymer–polymer pairs. Analysis of hysteresis loops indicated that the loop area was higher for polymer–polymer pairs, signifying the increased amount of dissipated energy. No noticeable variation was observed between the failure modes of steel–polymer and polymer–polymer pairs despite the significant difference in the operating temperatures. The bending stress and operating temperature were the dominant factors affecting the performance of steel–polymer and polymer–polymer gear pairs, respectively.

A review on materials and performance characteristics of polymer gears

“…Steel-polymer exhibits highest bending fatigue strength for 34°/20° configuration whereas polymer-polymer exhibits for 20°/34° configuration. 197 It has been examined from the experimental set-up of three-point loading on a single polymer gear tooth of asymmetry and symmetry profile that when pressure angle increases from 20° to 32°, single tooth stiffness increases by approximately by 10.8%. 198 The value of Lewis form factor for asymmetric teeth is described in terms of the coefficient of asymmetry and teeth number.…”

Influence of tooth asymmetry and mating gear material on the tooth deflection characteristics of polymer gears

“…Multi-pair contact models 7 developed in ABAQUS/Standard were employed to predict the tooth deflection characteristics. To approximate the actual conditions, contact-based models were preferred over point-load models.…”

“…4,5 To determine if the transmission error behavior of the asymmetric polymer gear is superior as compared to the symmetric gear, it is essential to evaluate the mesh stiffness. Since the mating gear material affects the life of polymer gears, 6,7 the investigation must consider metal-polymer and polymer-polymer engagements.…”

Dynamic response analysis of functionally graded gears

“…The design and performance of lightweight polymer and polymer composite gears have also been studied extensively in the literature, but their application is limited to low power transmission applications only. [16][17][18][19][20][21][22][23] Bi-metal and hybrid gears provide an appreciable weight reduction and performance comparable to steel gears. But the drawback of these gears is the problem of delamination and the presence of high-stress concentration on the joining interface due to abrupt changes in the material properties.…”

“…The design and performance of lightweight polymer and polymer composite gears have also been studied extensively in the literature, but their application is limited to low power transmission applications only. 16–23…”