Coefficients of static friction under statically and dynamically applied loads

Abstract

The coefficient of static friction under static loads with normal pressures of about 10,000 p.s.i. and under dynamically applied loads ranging from 10,000 to 20,000 p.s.i. were determined. The test apparatus was so arranged that dynamically applied normal and tangential loads are applied simultaneously. Results are given for combinations of steel rubbing on steel, titanium on steel, uranium on uranium, titanium on uranium, beryllium on uranium, and beryllium on titanium. Conclusions are that: (i) For certain combinations of metallic surfaces such as steel on steel and titanium on steel, the coefficient of static friction under a dynamically applied load is different from and less than the coefficient of friction under a static load; whereas for some other combinations of metals such as uranium on uranium, titanium on uranium, beryllium on uranium, and beryllium on titanium, the coefficient of static friction is essentially the same for static and dynamically applied loads. (ii) For some of the metals the coefficient of static friction was considerably changed by sliding under the applied loads. (iii) Titanium on steel shows a peculiarity not exhibited by any of the other metals tested. A small amount of slipping causes the kinetic coefficient of friction to rise above the previous static coefficient of friction.