Experimental Determination of Limiting and Sliding Friction Forces for Purposes of Modeling Slips, Stumbles, and Falls

Estimates of the coefficients of limiting and sliding friction for two selected shoes and two pedestrian surfaces were obtained from two separate procedures. Data generated from a procedure in which a weighted shoe was pulled across the surfaces were compared with data generated from a subject wearing the same shoes who performed a sliding maneuver on the surfaces. The sliding maneuver produced a wider range of loading conditions and consistently higher values of the coefficients of friction than the pulling tests. It was concluded that the magnitudes of coefficients of friction vary with the rate of loading. Values of the coefficients of friction showed variability from one trial to the next under each loading condition examined. Therefore it is recommended that empirically determined estimates of coefficients of friction should include some measure of variability.