Comparison of Single Cycle Overload Effect on Al-Li 2091-T81 Plate and 2091-T83 Sheet.

摘要

Previous researchers have established that for identical fatigue test conditions fatigue crack growth rate in aluminum-lithium alloy 2091 plate is far slower than in sheet, due to the development of a coarser fracture surface in the plate producing crack tip shielding resulting in a reduced effective crack driving parameter. Based on these results one would anticipate the plate material to exhibit a greater number of post-overload delay cycles than the sheet. This study was undertaken to quantify the effect of a single tensile overload fatigue cycle on the crack velocity of both product forms. The test procedure consisted of shedding the dynamic loads to a stress intensity range where a single 60 percent overload fatigue cycle was applied, followed by resumption of the pre-overload loading conditions.