A Study of High Speed Friction
MASSACHUSETTS INST OF TECH CAMBRIDGE SURFACE LAB
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A high speed friction and wear machine has been developed for operation in the 100-500 feet per second regime. Normal loads up to ten pounds are used with the upper limit determined by the force transducer. Signals corresponding to the frictional and normal forces are electronically divided to indicate the friction coefficient. All data is recorded on a high speed oscillograph. Wear of test materials is determined by weight loss measurement. Interfacial temperature measurements via thermoelectric effects and optical pyrometry can be made. The apparatus and associated instrumentation is described in detail. Results indicate a decreasing friction coefficient with increasing sliding speed. This is due to thermal softening, leading to the presence of low shear films at the interface. However, full hydrodynamic lubrication is not reached in the range of loads and velocities tested so the friction coefficient does not get below 0.14. The wear coefficient increases with sliding speed very rapidly. This is probably due to the change in hardness of the test materials at high temperatures. The following materials were tested against 4140 steel 70- 30 brass, gliding metal, copper, copper-16 lead, nylon, DQ3, Rulon A, vulcanized fiber, constantan, zinc, bismuth, Delrin, solder, grafite, iron, polycarbonate, polyethylene and woods metal.
- Test Facilities, Equipment and Methods