Fretting Corrosion(擦過腐食)概説
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When two pieces of material, pressed together by an external static load, (for example, bolted flanges, riveted lap-joints, press-fits such as a gear or bearing on a shaft) are subjected to a transverse cyclic loading, so that one contacting face is relatively displaced cyclically parallel to the other face, in the presence of high contact stress, wear on the mating surfaces occurs. If the magnitude of the displacement is less than about 0.003 inches, the wear is termed "fretting". Fretting occurs by contacting asperities on the mating surfaces continually welding together then breaking. That leads to surface pitting and the transfer of metal particles from one surface to another. In addition, the small fragments of metal which are broken off oxidize, forming oxide particles which, for most engineering metals, are harder than the mated parts. These particles become trapped between the mating surfaces and cause abrasive damage and scoring. Briefly, the characteristics of fretting are: