Part I. Theory report for CREEP-PLAST computer program: analysis of two- dimensional problems under simultaneous creep and plasticity
Description: >Solution of the combined creep and plasticity problem is considered. Both creep theories, the equation-of-state and memory theories, are used within the framework of the finite-element computatioral method. Because of the limited creep data, which is available only for single-step simple extension experiments, the integral expansion in the memory theory formulation is limited to one nonlinear superposition integral. However, instead of using direct superposition as proposed earlier, the kernel function was derived as an integral transformation that reduced the time--temperature- stress relationship to a single quantity. The equationof-state formulation is based on the monotoric strain-hardening rule app1ied to the primary creep componert only. The uniaxial stress- strain law is first discussed with emphasis on the memory theory. Then the incremental stress- strain relations for the combined creep and plasticity problem are derived for both creep theories. The time--temperature- stress transformation is derived for a particular class of material that exhibits well- defined primary and secondary creep parts such as stainless steel. The properties of the resulting stress- strain integral are discussed in relation to the direct-superposition method. Finally, example analyses are given. (auth)
Date: January 1972
Creator: Rashid, Y. R.
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