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Introduction
A bushing is an independent plain bearing inserted into a housing to provide a bearing surface for rotary applications, such as heavy construction machinery, transportation machinery, engineering machinery and gear pumps. A bushing can reduce the coefficient of friction during mechanical transmission (Colbert et al., 2010; Neale, 1995; Dickrell and Sawyer, 2004). Both bushings and bearings carry the load of pins. The structure of a bearing is of the split type, which has a relative motion between the inner and outer surfaces of the bearing. On the contrary, the structure of a bushing is integrated, and there is a relative motion between the pin and the bushing when it rotates. Bushings are used to fix the pin and reduce the wear of the pin; they can be used in bad working environments as well. Commonly used designs include solid (sleeve and flanged), split and clenched bushings. A sleeve, split or clenched bushing is only a sleeve of material with an inner diameter (ID), outer diameter (OD) and length. The difference between the three types of bushings is that a solid sleeve bushing is solid throughout, a split bushing has a cut along its length and a clenched bushing is similar to a split bushing but with a clench (or clinch) across the cut. A flanged bushing is similar to a sleeve bushing but with a flange at one end extending radially outward from the OD. The flange is used to locate the bushing positively during installation or to provide a thrust-bearing surface (Srivasrava and Pathak, 1996; Prasad, 2012; Spicer et al., 2001).
The surfaces of the pin and bushing are subjected to permanent deformation because of the extrusion pressure of the bushing and the effects of the composite mechanical force when operated for a long duration. However, the deformability is related to the clearance available for a clearance fit. The gap will widen because of wear if appropriate measures are not taken on time.
Lubrication is crucial in a pin and bushing system. Prchlik and Sampath (2007) researched the effects of a thermally sprayed coating on the friction and wear response. Colbert et al. (2010) analyzed the factors that significantly influence the friction of a polytetrafluoroethylene bushing using pin-on-flat tribometers. Khonsari...