Showing papers by "R. Gnanamoorthy published in 2004"
TL;DR: In this article, the failure mechanisms of Nylon 66 gears were examined under optical and scanning electron microscopy to understand the damage mechanism, and different types of failures such as gear tooth wear, cracking at the tooth surface, tooth root cracking and severe tooth shape deformation were observed.
Abstract: Application of short fiber reinforced thermoplastic materials are limited to functionally less important components due to heterogeneous characteristics of material and incomplete understanding of failure mechanisms involved. Reinforcement not only affects mechanical and electrical properties but also the failure mechanisms. Gears used in power/motion transmission may fail in many ways. This paper discusses the various types of failures exhibited by unreinforced and fiber reinforced Nylon 66 gears. Injection molded unreinforced, glass reinforced and carbon reinforced Nylon 66 spur gears were tested in a power absorption type gear test rig. Failed gears were observed under optical and scanning electron microscope to understand the damage mechanism. Different types of failures such as gear tooth wear, cracking at the tooth surface, tooth root cracking and severe tooth shape deformation were observed. Material compositions and applied torque decides the type of failure mechanism. Low interfacial strength between fibers and matrix in the reinforced gears causes fiber pullout. Reinforced gears exhibited longer life compared with the unreinforced gears due to superior mechanical strength and thermal resistance.
83 citations
01 Jun 2004
TL;DR: In this article, the tribological behavior of polymer and polymer composite gears was investigated using a power absorption-type gear test rig, and both injection-moulded nylon 6 and glass-filled nylon 6 gears were tested at different speeds and loads.
Abstract: The tribological behaviour of polymer and polymer composite gears is reported in this paper. Gear tests were conducted using a power absorption-type gear test rig. Injection-moulded nylon 6 and glass-filled nylon 6 gears were tested at different speeds and loads. Gear rotational speed influences the tooth wear of unfilled and glass-filled nylon 6 injection-moulded gears due to the change in contact period of teeth in mesh. When the polymer-based gear drives a steel gear, the difference in the elastic moduli of the mating materials causes rotational lag during gear running. When the polymer gears transmit a higher torque, a higher amount of rotational lag causes an excessive wear in the dedendum region of the polymer gear. In the cases of both unfilled and glass-filled nylon 6 gears, at higher-torque test conditions, non-uniform wear on the gear tooth surface was observed. Glass-filled nylon 6 gears showed a better wear resistance than the unfilled nylon 6 gears due to the improved compressive stre...
30 citations
TL;DR: In this paper, the performance of carbon reinforced Nylon gears was evaluated in a power absorption type gear test rig and failed and worn out surfaces were observed using optical and scanning electron microscope.
Abstract: Reinforced polymers offer superior strength and modulus required in many load-bearing applications. Reinforced thermoplastic polymer gears are used in motion as well as power transmission applications. The performance of reinforced polymer gears needs to be thoroughly understood for widening their application. This paper describes results of the ongoing research on polymer composite gear performance. Unreinforced and 20% short carbon fiber reinforced Nylon granules were used for the development of gears using injection-molding process. Gear tests were conducted in a power absorption type gear test rig. Gears were tested at a constant rotational speed of 1000 rpm and at various torque levels up to 3 Nm. Test results showed the superior fatigue strength of carbon reinforced Nylon gears compared with the unreinforced Nylon gears. Improved thermal resistance, high strength and modulus contributed to the superior fatigue performance of carbon reinforced Nylon gear. Failed and worn out surfaces were observed using optical and scanning electron microscope. Three major gear failure modes were observed; excessive wear, severe deformation and tooth fracture. Fiber orientation, presence of fiber particles between contact surfaces and poor surface finish affects the wear resistance of carbon-reinforced gear.Copyright © 2004 by ASME
2 citations