Fatigue crack growth thresholds measurements in structural materials

摘要

Fatigue crack growth thresholds and da/dN-data at low (Delta)k(sub I)- values (< 10 MPa(m)(sup 1/2)) have been determined for type 304 stainless steel, nickel-base weld metal Alloy 182, nickel-base metal Alloy 600, and low-alloy steel in air at ambient temperature and in high-temperature water and steam. The stainless alloys have been tested in water with 0.2 ppm O2 at 288 deg C and the low-alloy steel in steam at 286 deg C. The fatigue crack growth threshold was defined as the (Delta)K(sub I)-value resulting in a crack growth rate of 10 to the -7 power mm per cycle. The measured fatigue crack growth the material and the environment. A relatively inexpensive and time-saving method for measuring fatigue crack growth thresholds, and fatigue crack growth rates at low (Delta)K(sub I)-values, has been used in the tests. The method is a (Delta)K(sub I)-decreasing test with constant K(sub I)(sup Max). 11 refs., 4 figs., 4 tables.