Abstract
Polymer gears are used extensively in various applications. However, durability issues have been emerging because of friction at gear tooth contact areas. To extend the lifetime of polymer gears, a low-frictional coating has been considered as a possible strategy. In this study, a finite element simulation method was performed to investigate the contact stress between a pair of coated polymer gears. The simulation included various friction coefficients (COFs) for studying the effects of friction during the operation. Numerical results revealed that the friction causes the contact stress to shift over the roll angle, which is attributed to the direction of the sliding friction based on a free-body diagram. We also investigated the effects of coating and found that a thin coating has little effect on the bulk deformation behavior of the gear. Moreover, the stress distribution in the coating at the pitch point was investigated as the COF increased. Under zero friction, three notable stress regions were observed: 1) the center of the surface, 2) the end of the contact, and 3) the overall contact area. As COF was increased in the micro-slip region of the contact interface, both tensile and compressive stresses in the coating increased. This study provides significant aid to engineers for understanding the stress response of the coating applied to polymer gears to achieve an optimal design.
Highlights
The weight reduction of mechanical components is a crucial requirement for reducing energy consumption and satisfying environmental regulations [1,2,3]
A polyether ether ketone (PEEK) composite polymer and Diamond-like carbon (DLC) were chosen as the gear and coating material, respectively, to investigate the contact stress of a hard coating applied to a polymer gear
H at the pitch point calculated by American Gear Manufacturers Association (AGMA) and International Standards Organization (ISO) 6336 is approximately 184.3 and 163.8 MPa, respectively
Summary
The weight reduction of mechanical components is a crucial requirement for reducing energy consumption and satisfying environmental regulations [1,2,3]. A fundamental study on the contact stress during the operation of a coated polymer gear considering friction is still lacking Rating standards, such as those used by the International Standards Organization (ISO) and the American Gear Manufacturers Association (AGMA), are often used to calculate the contact stress of gears in the industry [23, 24]. Polymers have a significantly lower elastic modulus than metals; deflections of gear teeth must be considered to obtain an accurate estimation [25] Another limitation is that the standards do not consider friction effects when evaluating the contact stress [24]. Stress analysis of the coating was performed at the pitch point with a range of COF values
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