The Use of an Empirical Yield Surface Model in Predicting Shakedown Loads

Abstract

The Bleich/Melan Theorem permits shakedown loads to be calculated where the assumption of elastic/perfectly plastic material idealisation is realistic. For materials which demonstrate significant strain hardening characteristics an arbitrarily chosen proof-stress is often used in conjunction with this theorem. However, this technique will usually lead to an over-estimate of the shakedown load and the need exists for a more soundly based method of prediction. Any such method will require a re-statement of the Bleich/Melan Theorem to include strain-hardening effects. One such re-statement has been given together with a proof by Kraus and Rice (1) although this proof places considerable restrictions on the yield surface movements permitted. However, in this present work the Kraus and Rice Theorem is used together with an empirical yield surface model, to predict the shake-down pressures of three pressure vessel components manufactured from a strain-hardening material (stainless steel type 321).