Frictional Oscillations in Wet and Dry Elastomeric Sliding

The focus of this experimental study was the wet and dry sliding of elastomeric materials used in automotive applications. The study used an elastomeric hemisphere loaded normally against a flat counterface. The elastomeric specimens were natural rubber with 5 and 50 phr (parts per hundred rubber) carbon black. The tests were performed both in the wet and dry states. The results were compared to the classic predictions of oscillatory behavior based upon the friction (velocity) relationship. In the dry tests, oscillatory behavior was observed in regions of zero or slightly positive slope of the maximum coefficient of friction. In the wet tests oscillations were present in regions of negative slope of the maximum friction (velocity) curve.