Fatigue Under Out-of-Phase Biaxial Stresses of Different Frequencies

摘要: An analysis of fatigue under out-of-phase biaxial stresses of different frequencies shows that the stress conditions on the critical shear plane are of a nonconstant amplitude nature. A general expression for the allowable principal stresses to give long life fatigue is derived in terms of the uniaxial fatigue strength and the principal stress amplitude ratio, the expression being independent of both phase angle and frequency ratio. A test system to subject thin-wall cylinders to these stress conditions is described, and the results of tests under a range of out-of-phase angles and frequency ratios are given and discussed in relation to the derived theory. It is suggested that the maximum shear stress criterion of failure can be adapted for use in designing for such complex stress conditions.