Volume 18, Issue 1 (January 1990)
Effect of Compressive Underloads and Tensile Overloads on Fatigue Damage Accumulation in 2024-T351 Aluminum
Intermittent compressive underload and tensile overload tests were carried out on smooth specimens to determine the effect of large stress cycles on the fatigue damage of subsequent small cycles. A load interaction damage model, using a power-law relationship based on crack closure and damage concepts, accurately predicted the test results. The interaction damage was described by assuming that small fatigue cracks in smooth specimens have similar behavior to long cracks. The results indicate that small cycles below the constant amplitude fatigue limit can contribute significantly to damage accumulation, and that conservative damage summations can be made using a modified reference curve based on constant amplitude tests with a minimum stress on the order of the monotonic yield stress.