Fatigue Life Assessment Based on Crack Growth Behavior in Reduced Activation Ferritic/Martensitic Steel

Abstract

Crack growth behavior under low cycle fatigue in reduced activation ferritic/martensitic steel, F82H IEA-heat (Fe-8Cr-2W-0.2V-0.02Ta), was investigated to improve the fatigue life assessment method of fusion reactor structural material. Low cycle fatigue test was carried out at room temperature in air at a total strain range of 0.4-1.5% using an hourglass-type miniature fatigue specimen. The relationship between the surface crack length and life fraction was described using one equation independent of the total strain range. Therefore, the fatigue life and residual life could be estimated using the surface crack length. Moreover, the microcrack initiation life could be estimated using the total strain range if there was a one-to-one correspondence between the total strain range and number of cycles to failure. The crack growth rate could be estimated using the total strain range and surface crack length by introducing the concept of the normalized crack growth rate.

Fatigue crack growth in miniature specimens: The equivalence of ∆K-correlation and that based on the change in net-section strain energy density

“…Fatigue crack growth (FCG) experiments with miniature specimens are of interest with respect to the characterization of small-volume materials. Miniature specimens are used to evaluate biomaterials 1 , the variability of properties in small components 2 , and to evaluate the effects of irradiation of materials in nuclear applications 3 , 4 . Because of the size limitation, it is often not possible to strictly adhere to ASTM standard specimens 5 for fatigue crack growth testing.…”

High Temperature Fatigue Life Evaluation Using Small Specimen

“…The specimen utilized for this technology is a round-bar specimen with a test section diameter of around 1 mm. In the room temperature low cycle fatigue tests, this specimen produced the same fatigue life as the recommended specimen in the test standards, while the small hourglass-shaped specimen, which has been utilized for the material irradiation tests for about a decade [4][5][6][7][8][9][10], was clarified to show the different fatigue life from that.…”