Development and investigation on transmission efficiency of functionally graded material-based polybutylene terephthalate spur gears

Abstract

Application of polymer composite gears is increasing due to their superior properties. They have lower inertia, less weight, and run much quieter than their metal counterparts. In the present work, functionally graded material-based glass fiber reinforced polybutylene terephthalate gears are fabricated with a novel horizontal centrifugal casting technique using an injection molding machine. Conventional technique is used to fabricate homogeneous polybutylene terephthalate gears. Polybutylene terephthalate reinforced with 15 and 30 wt% glass fibers is used to fabricate gears. Unfilled polybutylene terephthalate gear is also manufactured for comparative study. Gradation in functionally graded material gear is verified by scanning electron microscope analysis, and Shore D hardness is measured in three different locations of the fabricated functionally graded material gears. Gradation in functionally graded material gear is also verified by ignition loss test method. Continuous gradation is observed in functionally graded material gear by scanning electron microscope and confirmed by hardness test and ignition loss test. The objective of present work is to investigate and compare the transmission efficiency of homogeneous and functionally graded material gears during operation. A polymer gear test rig is used for the experimental work. Experiments are conducted at various torque and speed combinations for 0.2 million cycles. Life span of fabricated gear is also tested for 10 million cycles. The range of the torque is 0.8–2.6 N m and the range for rotational speed is 500–1400 r/min. The transmission efficiency of the fabricated gears is found to be sensitive to the operating torque.