Agilent 5991-4865EN Evaluation of Bearing Materials Using Nano-Scale Wear Testing - Application Note c201408 free download

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Keysight Technologies Evaluation of Bearing Materials Using Nano-Scale Wear Testing Application Note Introduction The most common materials for bearing fabrication are metals, such as low-carbon steel, stainless steel, chrome steel and high-speed steel. Polymeric materials are alternative candidates due to their self-lubrication ability, high impact durability, high corrosion resistance, low specific gravity, and high melting temperature. Polymers have therefore received widespread attention as new tribological materials for dry, aqueous and corrosive conditions. Among these polymeric materials, polytetrafluoroethylene (PTFE), polyether ether ketone (PEEK) and also their composites are often used in tribological applications. In fans used for cooling of computers and other electronics, it has been found that one of the main contributors to failure is degradation of the miniature ball bearings [1], with deterioration of the lubricant as the primary failure mechanism in these applications. Due to the criticality of ball bearings, diagnosis and prognosis of these failures have been of interest to the industry. There are several techniques to detect faults in ball bearings. In 2011 Oh, et al, found a correlation between acoustic emission (AE) features and bearing degradation in computer cooling fans [2]. More recently, in 2013 Kumar, et al [3] determined the failure mechanisms of polymeric bearings using the analysis of vibration, speed and acoustic emission data, together with characterization of the worn bearing surfaces and measurements of friction. The bearing materials tested in this work were previously evaluated [3] at a rotational speed of 4800rpm in a test fixture which supports a load of approximately 1.4N. Acoustic emissions from these bearings during the initial stages of the operation of the bearings were monitored to compare the performance of these materials. These prior results are shown in Figure 1. Throughout most of the AE test, and especially near the end, the steel bearings exhibited the fewest AE events, followed by the PEEK and the PTFE bearings. Thus, from the AE test, we would rank the materials in order of performance (from best to worst) as: bearing steel, PEEK, PTFE. However, AE testing requires a long time. Thus, the aim of the present work is to establish a rapid assessment tool for bearing materials, where indications of the performance of the material can be known in hours, rather than days. We hypothesize that the results of nano-indentation and nano-wear testing are related directly to the results of AE testing. Abstract Self-lubricating polymeric materials are attractive candidates to be used as bearing materials in lightly loaded applications. In this study, miniature ball bearings made of steel, polytetrafluoroethylene (PTF