Fatigue Strength of ASME SA 106-B Welded Steel Pipes in 288C Air Environments.

摘要

Fatigue life tests were performed on 102-mm girth butt welded SA 106-B steel pipes in 288 C air under axial loading with a load ratio (R) of -1.00. The fatigue strength was determined to have an extrapolated value of 66.9 MP a (9.7 ksi), and the fatigue strength reduction factor (K (sub f)) was determined to be 3.47. Crack initiation usually occurred at the notch located at the internal weld fusion line on the inside diameter of each pipe, at the point of weld bead overlay. In all cases, the fatigue crack progressed on a plane normal to the pipe axis. The presence and relative number of secondary initiation sites, observed at internal weld fusion line locations around the pipe circumference, appeared to be a function of applied stress amplitude. ASME Section III analysis of the data, using the procedures given in NB-3228.5 and NB-3653.5, resulted in alternating stress (S (sub alt)) values which were conservative when compared to the ASME Section III mean data line for carbon steels. The results of the study successfully provide baseline data for comparison with proposed fatigue life tests of girth butt welded pipes containing 288 C PWR environments at 13.8 MP a, under axial loading at a cyclic frequency of 0.017 Hz.