Friction — Identical Metals

Coefficients of Kinetic Shding Friction for Pairs of Identical Metal Alloys... 

Inasmuch as friction conditions determine the flow characteristics of a powder, coarser powder particles of spherical shape flow fastest and powder particles of identical diameter but irregular shape flow more slowly. Finer particles may start to flow, but stop after a short time. Tapping is needed in order to start the flow again. Very fine powders (fine powder particles to coarser ones may increase the apparent density, but usually decreases the flow quality. Metal powders having a thin oxide film may flow well. When the oxide film is removed and the friction between the particles therefore increases, these powders may flow poorly. 

Modtilus Measurements Another SCC test technique is the use of changes of modulus as a measure of the damping capacity of a metal. It is known that a sample of a given test material containing cracks will have a lower effec tive modulus than does a sample of identical material free of cracks. The technique provides a rapid and reliable evaluation of the susceptibility of a sample material to SCC in a specific environment. The so-called internal friction test concept can also be used to detect and probe nucleation and progress of cracking and the mechanisms controlling it. 

Listed below are coefficients of kinetic sliding friction for plastics and other non-metals in identical pairs and on steel. 

Coefficients of fiiction of light conveyor belts are determined according to European standards.A metallic test panel under load, which generates together with the panel a normal force of 50 N, is pulled on the surface of a test piece. Forces required to initiate movement and maintaining it are recorded and results used for calculation of static and dynamic coefficients of friction. ISO, and the identical British standard, contain method of determination of frictional proper-... 

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