Full Size Felt Roll Journal Fatigue Test, 1997 Engineering Conference Proceedings

A technique was developed to test full size felt roll journals under laboratory conditions of known stress and environment. Corrosion fatigue cracks initiating at corrosion damage such as pits can result in premature failure. Component lab testing in combination with finite element fracture mechanics modeling was used to characterize the rate ofjournal cracking in lieu of using fracture and fatigue data obtained using sub-sized samples. The 100 mm (4 inch) minimum diameter 17-4 PH-H 1100 journals used were pre-notched to simulate prior damage due to corrosion. Tests were conducted in lab air and aggressive whitewater environments under typical maximum mill loading conditions. Test results indicated that a 3 mm (0.125 inch) notch was insufficient to cause a crack to propagate in lab air. However, in a whitewater environment, the same notch and stress resulted in complete fracture in less than 3 x 10 6 cycles. Vibration monitoring methods were able to detect the onset of fracture. In addition, the fracture mechanics model used to aid in predicting crack propagation rates and remaining life matched the test results within 100,000 cycles.