Effect of high hydrostatic pressure on the external friction coefficient

Experiments are carried out to determine the molecular and mechanical components of the specific friction force under the effect of hydrostatic pressure of up to 140 MPa. The molecular component of the friction coefficient declines by up to two times under the effect of the hydrostatic pressure in various fluids. It is found that the combined influence of the temperature and hydrostatic pressure on the mechanical properties and the contact pressure leads to considerable variations in the deformation component of the static friction coefficient in plastic contact at temperatures of up to 200°C and under pressures of up to 140 MPa. The dependence of the hardness of structural materials on the hydrostatic pressure is analyzed to predict the effect of the latter on the deformation component of friction. It is shown that with increasing pressure within the above range the hardness grows in proportion to the square of the pressure and is inversely proportional to the initial hardness. The formula for calculating the dependence of the indentation depth of a spherical indenter in elastic contact on the hydrostatic pressure is derived.