Abstract:

ESDU 76014 details a method for constructing a constant amplitude S-N curve for a component from a knowledge of an S-N curve obtained by testing specimens of the same material with a similar surface finish and under similar environmental conditions. The procedure corrects firstly for the influence of any stress raiser in the test specimen, including any plasticity effects, and then constructs a zero mean stress (although any value could be used) S-N curve. That S-N curve is then finally corrected for any relative size differences between the test specimen and the required component to which the constructed curve is to be applied. A comprehensive worked example illustrates the use of the method. Also included is a method for representing the stress-strain curve of a material by a two-constant equation over the complete range beyond the limit of proportionality.