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Comparative Analysis of Standardized Test Methods on Common Tribological Test Rigs

Jürgen Rigo and Pavel Kovačócy

Faculty of Materials Science and Technology, Slovak University of Technology in Bratislava, Trnava 917 24, Slovak Republic


Abstract: An important aspect of tribology is the mechanical-dynamic testing of lubricants and materials under stress and the interpretation of the results obtained therefrom. Widely-used test methods are often applied to analyze the performance of, for example, lubricants. However, this testing is often conducted using standard testing parameters with little or no correlation to the demands of real life applications. Therefore, test results determined with tribometers or in field tests should be evaluated carefully by considering the entire tribological system. Tribological test benches are suitable to investigate the lubricant formulations, combined with different materials at different moving types, temperatures and loads terms, in their frictional behavior and wear protection. As part of the previously implemented projects numerous testing procedures have already been developed for each test bench. The main objective of this research is the subsequent analysis of test results using different tribometers. This should lead to better identification and improved understanding of divergent results generated by different testing procedures. Test results will be validated using standardized test systems according to DIN and ASTM, respectively. It was found that different test methods, all of which are used for the evaluation of high pressure carrying capacity of lubricants for example, do not provide the same results. As an example, the comparability of the weld load determination (DIN 51350 Part 2) in the four-ball tester and the standard test method for measuring the extreme pressure properties of lubrication oils in the high frequency, linear oscillation tester (SRV®) according to ASTM D7421-11, should be mentioned. Here quite disparate rankings occur. It does not matter which test is used for characterization. The following tribometers are used: (1) Four ball tester (VKA); (2) High frequency, linear oscillation tester (SRV®); (3) Cross-cylinder tester (XCT). Several lubricant samples got tested strictly following the standard test methods. Variations of the test parameters and the test samples will also be carried out and presented in future publications.

Key words: Lubricants, base oil, additives, mechanical testing, tribological test rig.
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