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The significance of polymer gears to transmit power and motion is increasing continuously due to their inherent characteristics. Polymer gears have established themselves as attractive alternatives to traditional metal gears in plethora applications. They are light in weight, have lower inertia, and run noiseless than their metal counterparts. This article presents a comprehensive review of the research on polymer spur gears operating under low (0–8 Nm) and moderate (>8 and ≤17 Nm) loading conditions. Different polymers and polymer composites used till date for the fabrication of such gears are included along with different operating conditions. Various design features of polymer gears and tooth modification techniques for the improvement of the performance and durability of these gears have also been included in this review. The aspects of the modeling and simulation studies of the polymer gears are also emphasized in this paper for completeness of the review. The concept of hybrid gears is discussed along with their tribological properties. Various methods of manufacturing of polymer gears and their failure modes are discussed so as to make the article useful for researchers.

This article presents the comparison of mechanical and dry sliding wear peculiarity of zinc oxide (ZnO)-filled polyester composites, fabricated by two different techniques. These two techniques are simple mechanical stirring and vertical centrifugal casting. ZnO filled polyester based homogeneous composites are fabricated by simple mechanical stirring technique whereas composites fabricated by vertical centrifugal casting technique are functionally graded materials (FGMs). Dry sliding wear tests are performed over a range of sliding velocity (1.57-3.66 m/s), normal load (10-30 N), filler content (0-20 wt%), and sliding distance (1000-3000 m) using a pin-on-disc apparatus. This study establishes that the FGMs exhibit superior mechanical properties (except tensile strength) and wear resistance as compared with homogeneous composites. Among all the fabricated composites, FGMs filled with 20 wt% ZnO filler has maximum hardness and flexural strength i.e. 70 HRL and 39 MPa, respectively. Compressive and impact strength is maximum for 10 wt% ZnO filled FGMs with 36 MPa and 1.3 J, respectively. The tensile strength of homogeneous composites is 21.7% higher as compared with FGMs for 10 wt% of ZnO filler loading. FGM filled with 20 wt% of ZnO filler has minimum specific wear rate of 0.33 3 10 25 mm 3

In this research work, short glass fiber has been used to fabricate polyester-based homogeneous composites and their functionally graded material. Vertical centrifugal casting technique and simple mechanical stirring is used for fabricating functionally graded materials and homogeneous composites, respectytively. Wear tests are conducted over a range of sliding velocities (1.57–3.66 m/s), normal load (10–30 N), fiber contents (0–6 wt%), and sliding distances (1–3 km). Friction and wear characteristics of developed materials are successfully analyzed using Taguchi design of experiment scheme and analysis of variance (ANOVA). Artificial neural network approach is also applied to the friction and wear data for subsequent validation. Out of all samples fabricated it is found that 6 wt% short glass fiber polyester-based functionally graded materials exhibit lowest specific wear rate. Additions of short glass fiber in polyester-based functionally graded materials have an incisive effect on tensile and flexural strength in comparison to homogeneous composites. The morphology of worn composite specimens has been examined by scanning electron microscopy to understand about dominant wear mechanisms.

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