fatigue strength and related characteristics of aircraft jointsⅡ-fatigue characteristics of sheet and riveted joints of 0.040-INCH 24S-T, 75S-T, AND R303-T275 ALUMINUM ALLOYS

摘要

The results of a series of fatigue tests of aluminum-alloy sheet materials and of simple riveted joints in these materials are presented. The materials tested were 24S-T Alclad, 24S-T bare, 75S-T Alclad, R303-T275 clad, and R303-T275 bare. All sheets were of the 0-O4O-inch gage.nUnnotched sheet specimens, specimens notched by a drilled hole, and specimens with scratches were tested in direct-stress fatigue. It was found that:n(1) Bare materials notched or unnotched had greater fatigue strengths at long lifetimes than corresponding clad materialsn(2) The 75S-T Alclad and the R303-T275 clad although stronger statically than the 24S-T Alclad were generally somewhat weaker in long-life fatiguen(3) Although shallow scratches did not affect the fatigue strengths of the clad materials scratches deeper than the minimum depth of cladding were detrimental.