THE INFLUENCE OF LOAD MISALIGNMENT DURING UNIAXIAL LOW-CYCLE FATIGUE TESTING—II: APPLICATIONS

Abstract— Models for predicting scatter bands due to bending have been applied to four alloys, namely AISI 316L, Nimonic 101, 9 Cr-1 Mo, and IN 718. The alloys were tested extensively by 26 laboratories in an international round robin exercise sponsored by the Community Bureau of Reference (BCR) of the EC. After initially selecting data for analysis on the basis of their confirmed conformance to the ASTM bending criterion, it has been shown that in all four materials a major fraction of the data scatter could be attributed to bending. Furthermore, at the lowest strain range the predicted bending component represents the highest proportion of the experimental interlaboratory scatter. Many laboratories did not report any measure of bending and so could not be used in the initial analysis. However, a further interesting deduction from the models is that the entire BCR data-set can be encompassed within a scatter band based upon a bending criterion that is twice the allowable ASTM limit. Differences in the extent of scatter between materials at a given total strain range can be attributed to the gradient of the logarithmic plot of total strain range as a function of lifetime.