Effect of Range of Stress on Fatigue of 76S-T61 Aluminum Alloy Under Combined Stresses Which Produce Yielding

Fatigue test data under bending, torsion, and combined bending and torsion are presented for mean stresses from zero to values which cause substantial yielding. The mean nominal stresses in the bending and the torsion tests were corrected for the effect of the nonlinear distribution of stress resulting from yielding. Static tests in tension, compression, bending, and torsion also are described. The applicability of several theories of failure are compared with these test data. The role of anisotropy of the material, mechanism of crack formation, mean stress, and maximum stress are discussed.