Abstract
The paper demonstrates that the dry clutch friction plate wear rate, measured based on the plate mass difference method, exhibits a transient behavior after each change of friction interface temperature level. The effect is hypothesized to be caused by a temperature-dependent change in the moisture content/mass level in the friction material. To test this hypothesis, a series of synchronized characterization experiments have been conducted by using two friction plates, one for wear tests and the other for drying in an oven under the same temperature conditions. Based on the analysis of test results, a moisture content compensation procedure, which reduces the transient wear rate from being 100% to being 50% higher compared to stabilized wear rate, is proposed and verified. The gained insights are used to set recommendations on the organization of routine wear characterization experiments aimed at avoiding the effect of moisture content influence on the accuracy of wear measurement. The main recommendations are to minimize the number of temperature target level changes through proper design of the experiment, insert a run-in test after every long test pause, and execute a pre-heat, blind wear test at the beginning of each test day.
Highlights
Possible dry clutch wear rate transient effects related to the change of influential operating parameters have been investigated
While the change of torque and slip speed levels did not result in observable wear rate dynamics, the change of temperature level induced distinct wear rate transients, especially when switching to a high-temperature level
The very first wear rate value after the temperature level transition peaked to be approximately 100% higher compared to the stabilized wear rate for the given temperature level
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. It is shown in [23] that the second, mass-difference-based approach yields more reliable results for test procedures based on small worn volume increments, which are needed to characterize wear for a large set of operating parameters in a reasonable time frame [23] This is because the thickness measurement is sensitive to thermal expansion effects and piece-to-piece variation of the friction plate woven-spring compliance. The main contributions of the presented study are: (i) experimental analysis of air moisture influence on the accuracy of the dry clutch friction plate, mass difference-based wear rate measurement, and (ii) recommendation of wear test organization to mitigate the moisture influence
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