FATIGUE LIFE ANALYSES AND TESTS FOR THICK-WALL CYLINDERS INCLUDING EFFECTS OF OVERSTRAIN AND AXIAL GROOVES

A fracture mechanics-based fatigue life analysis was developed for overstrained, pressurized thick-wall cylinders with one or several semi-elliptical-shaped axial grooves at the inner diameter. The fatigue life for a crack initiating at the root of the groove was calculated for various cylinder, groove, and crack configurations and for different material yielding conditions. Comparisons were made with fatigue crack growth and laboratory life results from A723 thick-wall cylinders, in which cannon firing rests were first performed to produce axial erosion grooves; followed by cyclic hydraulic pressurization to failure in the laboratory. The life analysis, with an initial crack size based on the expected pre-existing defects, gave a good description of the crack growth and fatigue life of the tests for cylinders with and without grooves. General fatigue life calculations summarized important material and configurational effects on the fatigue life design of overstrained cylinders, including effects of material yield strength, cylinder diameter ratio, stress concentration factor, and initial crack size.