Calculation of a lower bound ratchet limit part 1 – Theory, numerical implementation and verification

It is important to be able to calculate the ratchet limit of a component when performing integrity assessments of plant components. This paper details the addition of a lower bound ratchet limit calculation to the Linear Matching Method. The extension of Melan's theorem into the alternating plasticity region is explained, followed by its implementation into the Linear Matching Method calculation procedure. Finally, the convergence properties of this method are analysed by the analysis of a plate with a central hole subject to cyclic thermal and mechanical loading.

► A lower bound procedure for calculation of lower bound ratchet limits is presented.
► A theoretical extension to Melan's theorem is presented.
►  The numerical implementation into the Linear Matching Method is described.
► A benchmark problem is analysed to verify the method.