Effect of displacement rate on the real area of contact and temperatures generated during frictional sliding of Tennessee sandstone

Summary

The real area of contact has been determined, and measurements of the maximum and average surface temperatures generated during frictional sliding along precut surfaces in Tennessee sand-stone have been made, through the use of thermodyes. Triaxial tests have been made at 50 MPa confining pressure and constant displacement rates of 10⁻² to 10⁻⁶ cm/sec, and displacements up to 0.4 om. At 0.2 cm of stable sliding, the maximum temperature decreases with decreasing nominal displacement rate from between 1150° to 1175°C at 10⁻² cm/sec to between 75° to 115°C at 10⁻³ cm/sec. The average temperature of the surface is between 75 and 115°C at 10⁻² cm/sec, but shows no rise from room temperature at 10⁻³ cm/sec. At 0.4 cm displacement, and in the stick-slip mode, as the nominal displacement rate decreases from 10⁻³ to 10⁻⁶ cm/sec, the maximum temperature decreases from between 1120° to 1150°C to between 1040° to 1065°C. The average surface temperature is 115° to 135°C at displacement rates from 2.6×10⁻³ to 10⁻⁴ cm/sec.

With a decrease in the displacement rate from 10⁻² to 10⁻⁶ cm/sec, the real area of contact increases from about 5 to 14 percent of the apparent area; the avergge area of asperity contact increases from 2.5 to 7.5×10⁻⁴ cm². Although fracture is the dominate mechanism during stick-up thermal softening and creep may also contribute to the unstable sliding process.