ABSTRACT
According to this model by Strandberg, the height of the wear surface element above the floor surface when a shoe vertically descends in a fluid film depends on the viscosity of the fluid, the contact area between the surfaces, the vertical load, and the descending time. The lubricant drainage time for a specified fluid viscosity, normal load and fluid film thickness becomes four times longer when the contact area is doubled. A long drainage time, on the contrary, increases the actual risk of slipping, because the time available to prevent a forward slip after heel contact is very short, only a few tenths of a second (Strandberg and Lanshammar, 1981). Hence, adequate frictional forces may not be produced between the shoe heel and a smooth lubricated walking surface quickly enough to prevent slipping and falling.
