The Use of Notched Compact-Type Specimens for Crack Initiation Design Rules in High-Temperature Water Environments

作者：T. A. Prater, LF Coffin · 年份：1983 · DOI：10.1520/stp44823s · 被引用次数：10 · 研究领域：Material Properties and Failure Mechanisms、Engineering Diagnostics and Reliability、Structural Integrity and Reliability Analysis

This report describes the techniques used and results obtained for fatigue crack initiation of notched compact-type (CT) tests of SA333 Gr.6 carbon steel in air or in autoclaves mostly at 288°C (550°F), 1.05 kg/mm2 (1500 psi) oxygenated water conditions. The fatigue crack initiation life Ni was quantitatively determined from a cycle-by-cycle crack length measurement as the number of cycles of produce 7.6 × 10−2 mm (0.003 in.) of growth from the notch root. Results for several parameters of the experimental program (including temperature, environment, oxygen content, frequency of cycling, notch radius, R-value, and ΔK) are reported. A majority of the tests were run in 288°C (550°F) water at 8 ppm O2 with 5.1 × 10−2 mm (0.002 in.) notch radii, and showed a severe degradation in initiation life, especially at a frequency of 0.00021 Hz (0.0125 cpm), compared with 288°C (550°F) air tests. On the other hand, at 0.021 Hz (1.25 cpm) and 8 ppm O2, decreasing the temperature to 232°C (450°F) restored the life to that of air. Reducing the oxygen level to 0.2 ppm in 288°C (550°F) water was also beneficial. These latter two findings are preliminary because of limited testing. The test results were interpreted in terms of conventional procedures in which a notch root pseudostress amplitude Sa was calculated for each test and compared with the ASME fatigue data curve for carbon steel. The quantity Sa was obtained from the applied stress intensity range (ΔK) and Neuber notch analysis procedu...