Effect of Groove Geometry on Rolling Contact Fatigue of PEEK Thrust Bearings in Water

Abstract

Bearings have been used in various environments. Recently, small and light-weight bearings are developed in order to downsize mechanical components. Polymer bearings, such as PEEK (Poly-Ether-Ether-Ketone), PTFE (Poly-Tetra Fluoro-Ethylene) and PPS (Poly-Phenylene-Sulfide-Resin), are designed because of advantages of light weight, high corrosion resistance and self-lubricating. However, industrial design standards of these bearings have not been established yet, i.e., the relation between working conditions, shape, geometry, and lives of bearing components under RCF (Rolling Contact Fatigue) is not fully understood as well as crack propagation, wear and/or failure. In this study, we focused on the manufacture process of groove curvature decreasing contact stress, and observed cracks and flaking failures on groove surfaces and cross sections. Based on these observations, we investigated the relation between the groove geometry and lives of all-PEEK thrust bearings in water.

Influence of Groove Roughness on Crack Initiation of PEEK Thrust Bearing in Water

“…5 shows the relation between load and Ra. Load values of no-failure data in this figure were referred from Orito's study [12]. All Ra data were newly measured in the present study.…”

“…Orito et al performed the RCF tests of PEEK specimens whose groove radius were 1.0, 1.8, 2.4 and 4.8 times as large as the ball diameters, and sorted the wear loss and the condition of failure in water. They found the groove shape did not affect the wear losses and the load condition of fracture in 1.8, 2.4 and 4.8 times specimens [12]. In the present works, in order to find the failure conditions of PEEK thrust bearing and evaluate the surface texture, the RCF tests of PEEK thrust bearing in water were carried out.…”

“…The thrust load and the rotating speed were 2500N and 1200rpm, respectively. In Orito's work [12], some data were plotted as R=1.0, but these data were newly defined as R=1.2 basing on detail observation surface profile in the present study. The present load value of 2500N was selected from the newly defined data.…”

Weibull Distribution to Evaluate the Reliability of PEEK Thrust Bearings under Rolling Contact Fatigue in Water

“…Bearings manufacturers have been turning to other materials, including engineering plastic polymers. Though not as strong as steel, polymers as materials have excellent properties [3,4]. Mechanical equipment use is diversifying into new fields, so market demands now exist for machines in areas previously unknown, including pumps, food processing, and medical.…”

“…Failure fatigue of PEEK bearings in water conditions is not fully understood, but the main reason is cracking and flaking. Understanding failure mechanisms will come from further investigating relationships between loads and rotation speeds [3].…”