Abstract:Gears are subjected to different rotational speeds/frequencies during their service life. The effect of the rotational speed on the performance of a metal gear is insignificant; however, it affects the thickness of the lubricant film. Polymer gears generate hysteretic self-heating because of the viscoelastic behavior of the material, thereby limiting their performance and usage in applications. The injection molded polyamide 66 spur gears were loaded by ground steel gear at different torques and frequencies us… Show more
“…Generally, higher cycling frequencies are not recommended for polymer testing, as the internal heat generation weakens the strength of the material. 18,20 However, for tests entailing considerably longer durations, accelerated testing is warranted. As bending fatigue tests are typically time-consuming, a higher cycling frequency was deemed appropriate.…”
Section: Test Methodologymentioning
confidence: 99%
“…A concise account of the test rig is provided in this section, as the test rig components are comprehensively described elsewhere. 17,18 The system was powered by a servo motor (BALDOR, BDM -100C -3250), which was regulated by a servo drive (Motiflex). The loading and control systems are connected to the human machine interface, which allowed the user to set the torque and cycling frequency.…”
Section: Description Of Bending Fatigue Test Rigmentioning
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.
“…Generally, higher cycling frequencies are not recommended for polymer testing, as the internal heat generation weakens the strength of the material. 18,20 However, for tests entailing considerably longer durations, accelerated testing is warranted. As bending fatigue tests are typically time-consuming, a higher cycling frequency was deemed appropriate.…”
Section: Test Methodologymentioning
confidence: 99%
“…A concise account of the test rig is provided in this section, as the test rig components are comprehensively described elsewhere. 17,18 The system was powered by a servo motor (BALDOR, BDM -100C -3250), which was regulated by a servo drive (Motiflex). The loading and control systems are connected to the human machine interface, which allowed the user to set the torque and cycling frequency.…”
Section: Description Of Bending Fatigue Test Rigmentioning
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.
“…35 Polymer gears undergo hysteretic heating during bending fatigue tests. 28 The heat generated during the bending fatigue test and its influence on the fatigue performance was not quantified in this study. The operating temperature of polymer gears under service condition is substantially higher than the temperature rise caused by hysteretic heating during bending fatigue tests.…”
Section: Bending Fatigue Life Of Symmetric and Asymmetric Gearsmentioning
confidence: 97%
“…A detailed description of the test rig has been given elsewhere. 28 Figure 2.(a) Bending fatigue test rig; (b) human–machine interface device; (c) schematic of the test rig.…”
In this work, the bending fatigue strengths of injection-molded symmetric and asymmetric nylon 66 gears were evaluated experimentally, and the results were substantiated using numerical studies. The symmetric (20°/20°) and asymmetric (34°/20° and 20°/34°) configurations were subjected to bending fatigue tests under a load controlled mode. The bending stresses of the symmetric and asymmetric gears were predicted by quasi-static simulations using a commercial finite element analysis software. The form factor ([Formula: see text]) and the stress correction factor ([Formula: see text]) were computed using an adapted ISO method. The 34°/20° configuration exhibited the lowest bending stress and highest bending fatigue life among the tested configurations. The form factor exerted a decisive influence on the magnitude of the bending stress compared to the stress correction factor. For the considered loading conditions, deflection-induced load sharing occurred in the 20°/20° and 20°/34° configurations but was absent in the 34°/20° configuration. Failure analysis indicated that a high stress concentration caused multiple cracks in the fillets of asymmetric gears.
“…Kodeeswaran et al [9] attempted to evaluate the performance of unidirectional and bi-directional load polyamide gear. Results concluded that thermomechanical and root crack were detected in the case of bi-directional loading.…”
Polyamide, with its low friction coefficient, high heat resistance and good moldability, is a promising polymer to meet the rising demand for lightweight, durable gears. This paper considered injection-molded polyamide 66-polyamide 66 gear pair wear performance under unlubricated and wet lubricated condition. The experiment was conducted using in-house developed power absorption gear test rig. The torque of 1.8 Nm, rotational speed 800 rev/s and lubricant SAE 75W85 was considered during testing. During the test, gear tooth temperature under unlubricated condition and lubricant temperature under wet lubricant condition was measured and monitored. The net surface temperature on the gear surface and lubricant was observed as 370 K and 303.4 K, respectively. The transmission efficiency was increased by 5% compared to the unlubricated condition. Testing confirmed that the gear exhibited surface wear at both the face and flank region in unlubricated condition. While testing under wet lubricant condition, the wear was observed on the face of the gear. Simulation result confirmed that the deflection of test gear is significantly higher in double tooth contact region shared by the face side as compared to flank side of the driven (test) gear. That could be the possible reason for test tooth wear in the face region.
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