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In evaluating appearance of anodized aluminum, the most important kinds of glossiness are commonly termed distinctness of image, bloom, and haziness. To obtain a simple, meaningful set of quantitative numbers, the various kinds of glosses are related to specific portions of a goniophotometric curve. The technique is applicable to mirror-like metal finishes, to etched and patterned metal surfaces, and to ceramic and paint coatings. This method agrees well with visual ratings, is sensitive to minimum visually detectable differences within products, and provides a means for numerically classifying different products without need for material standards for calibration.

Data are presented to show the various factors that affect the fatigue strength of aluminum. For metallurgical size test specimens, the fatigue strength is affected by the alloy, temper, metallurgical condition, shape of specimen, surface condition, type of loading, product, stress concentration, residual stress, and temperature. However, these variables generally do not have a great effect on the fatigue strength of service parts containing stress raisers. Thus, for long fatigue life, good design and attention to details are generally more important than choice of alloy.

ALUMINUM-TIN alloys which promise to be excellent bearing materials are the result of an intensive research and development program carried out by the authors. After testing a number of aluminum alloys for antiscoring qualities, fatigue resistance, and mechanical stability in operation, they concluded that the optimum bearing characteristics are found in alloys having a plastic, low-melting phase and a relatively hard phase uniformly distributed throughout an aluminum solid solution matrix of moderate hardness. Tin, affording ease in alloying and resistance to corrosion in lubricating oils, furnishes the best plastic constituent. Pure aluminum-tin alloys do not possess the strength needed in highly stressed bearings. The addition of silicon forms a hard constituent which increases strength markedly. Antiscuffing qualities are improved also, although ductility is reduced.