METHODS FOR THE EVALUATION OF CREEP RELAXATION AND THE AMPLITUDE OF REVERSE PLASTIC STRAIN FOR BODIES SUBJECTED TO CYCLIC LOADING

摘要

An extension of the upper bound shakedown theorem to load histories in excess of shakedown has been applied in previous papers to the evaluation of a ratchet limit and the varying plastic strain magnitudes associated with a varying residual stress field by the Linear Matching Method. In the present paper, this technique is further applied to the evaluation of creep-reverse plasticity mechanism for bodies subjected to cyclic loading including creep effects. The accumulated creep strain, the varying flow stress and the corresponding varying residual stress field during a creep dwell time are evaluated. The elastic follow-up factors are calculated thereafter. In order to verify the applicability of the proposed method, a monotonic creep computation method based upon the rapid cycle solutions is introduced for comparison. A holed plate subjected to cyclic thermal load and constant mechanical load is assessed in detail as a typical example. The consistent solutions of the accumulated creep strains, the varying flow stresses and the elastic follow-up factors with creep dwell time by these different methods confirm the applicability of the proposed new methods.