Statistical Analysis of Traction Measurements with Rolling, Sliding, and Spin

Abstract

Traction measurements, like any other physical testing, contain variability associated with the test rig, test samples, and data acquisition systems. These natural sources of variation increased when simulating contacts with spin velocity in the most common rolling and sliding test conditions. Averaging the results within one test sequence with spinning, rolling, and sliding velocities did not always reflect the expected results from the entire population of possible measured values. To be confident in the conclusions that were drawn from the traction testing, it was important to repeat the test sequence several times and apply statistics for defining error bands around the expected traction values. To allow for easy application of error bands, simplified equations were curve fit to the data from the numerical routines. By making use of error bands, an easy determination of the test repeatability can be discerned, and quantified comparisons between data sets can be made with a higher degree of confidence.

Keywords:

• Friction Elastohydrodynamic (Traction)
• Friction Testing

ACKNOWLEDGMENTS

The author thanks The Timken Company for permission to publish this work. Also, the author thanks Mr. Mark Frank of The Timken Company for conducting the experiments used within this study as well as Dr. Luc Houpert and Mr. Michael Hoeprich of The Timken Company for their insightful discussions on this topic.

Presented at the 59th STLE Annual Meeting in Toronto, Ontario, Canada May 17-20, 2004

Final manuscript approved March 4, 2004

Review led by Robert Errichello