Experimental methods for the assessment of tribological hard contacts at the device, component, and surface scales.

摘要

Measurement techniques are applied to tribocomponents at three size scales. Device-level parameters are assessed in a displacement-controlled axial bearing test rig. Component-level testing is performed using a miniature radio telemeter embedded in a bearing roller. Contact pressure and temperature are measured with thin-film contact sensors fabricated on steel and glass disks and loaded in an optical EHL (elastohydrodynamic lubrication) test system.; Low crosstalk bearing torque measurements were made with a compliant fixed shaft and two RF (radio frequency) proximity sensors. Use of single components for multiple functions permitted the fabrication of a 5 by 9 by 1.5 millimeter sensor/telemeter weighing 80 milligrams. Data was transmitted using thermal frequency modulation of oscillator tank capacitance. Telemeter output sensitivity of the thermal frequency modulation technique at temperatures above 40°C was 15 KHz/MHz-°C. A comparative analysis of signal conditioner bandwidth, spatial averaging and capacitive coupling facilitates determination of the speed-limiting aspect of a thin-film contact sensor. Techniques for photolithographic patterning of zirconium, a material exhibiting a low pressure coefficient of resistance, have been developed.; Load increments up to 10% associated with component heating and with oil film development in tapered roller bearing contacts were measured using the axial bearing tester. Rapid thermal response to loss of lubricant of instrumented bearing rollers indicates great potential of the technology in condition monitoring. Pressure distributions measured in grease-lubricated contacts loaded to peak Hertz stress levels of 0.78 to 0.87 GPa were indicative of the base oils, with no thickener-induced broadening observed.