(a) Purpose of Investigation.—To determine the effect of small holes, such as inspection holes, in reducing the effective tensile strength of aluminium alloy sheet, and to examine the efficiency of two types of reinforcement.n(b) Range of Investigation.—Tensile tests have been made on plates 10 inches and 13 inches wide cut from sheets of 16, 20 and 24 s.w.g. The series of test pieces comprised one set plain without holes, one set with a 3-inch diameter hole in the middle of the test length, one set with the same hole reinforced at the edge by a cover ring riveted on, and three sets with the hole reinforced by pressed flanges of three different depths.'.n(c) Conclusions.—The presence of the hole reduces the, tensile strength of the sheet in the transverse section through the hole only slightly, and the reduction is not appreciably affected by reinforcing the hole.
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