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An apparatus has been developed to test the sliding friction and wear characteristics of various ceramic and other high-temperature material combinations, in the bare and solid lubricated modes, subjected to a wide spectrum of environmental conditions. In the friction tester, a cylindrical rod specimen is rotated while two stationary samples (rub shoes) are forced against the rotating surface from opposite sides under a wide range of loads, speeds, and temperatures. The friction contact surfaces can be heated to temperatures ranging from 25 to 871°C. Sliding contact speeds can be varied from 0.5 to 5.0 m/s and normal contact forces can be adjusted up to 200 N. The applied load can be either a steady-state force or a repetitive function (sinusoidal or other), with frequencies up to 50 Hz, thus simulating the actual loading conditions found in many types of machinery. Each stationary specimen can be readily changed to permit tests with flat, concave or convex cylindrical, and with spherical contact surfaces. The atmosphere surrounding the contact area can be purged either with standard air or an inert gas, such as dry nitrogen, helium, or argon. Unlike other high temperature testers, it does not require a large furnace, but uses a compact infrared quartz lamp heater. The apparatus has instrumentation to monitor the temperature, speeds, and combined wear depth on the stationary and rotating surfaces. Despite its versatility and many capabilities, the tester is relatively simple, constructed with readily available state-of-the-art components, and is easily operated. This paper describes the background leading to the development of the tester, its principles of operation, design details, and the results of mechanical and thermal tests validating the design concept.
friction tester, Tribotester, rub shoe pads, rolling contact fatigue (RCF) tester
Hughes Aircraft Company, EDSG, Mechanical Engineering Laboratory, El Segundo, CA