A Cyclic-Plasticity-Based Mechanistic Approach for Fatigue Evaluation of 316 Stainless Steel Under Arbitrary Loading

Abstract

In this paper, a cyclic-plasticity-based fully mechanistic fatigue modeling approach is presented. This is based on time-dependent stress–strain evolution of the material over the entire fatigue life rather than just based on the end of live information typically used for empirical S∼N curve-based fatigue evaluation approaches. Previously, we presented constant amplitude fatigue test based related material models for 316 stainless steel (SS) base, 508 low alloy steel base, and 316 SS-316 SS weld which are used in nuclear reactor components such as pressure vessels, nozzles, and surge line pipes. However, we found that constant amplitude fatigue data-based models have limitation in capturing the stress–strain evolution under arbitrary fatigue loading. To address the aforementioned limitation, in this paper, we present a more advanced approach that can be used for modeling the cyclic stress–strain evolution and fatigue life not only under constant amplitude but also under any arbitrary (random/variable) fatigue loading. The related material model and analytical model results are presented for 316 SS base metal. Two methodologies (either based on time/cycle or based on accumulated plastic strain energy (APSE)) to track the material parameters at a given time/cycle are discussed and associated analytical model results are presented. From the material model and analytical cyclic plasticity model results, it is found that the proposed cyclic plasticity model can predict all the important stages of material behavior during the entire fatigue life of the specimens with more than 90% accuracy.

Finite Element Based Full-Life Cyclic Stress Analysis of 316 Grade Nuclear Reactor Stainless Steel Under Constant, Variable, and Random Fatigue Loading

“…Note that the subscript v is used to demonstrate that the material parameters are not constant as they are in the case of conventional cyclic plasticity model, rather they are variable and can be function of time or fatigue cycle/block or any other physical state (e.g., APSE). The complete details of the model development and time-dependent material parameter estimation technique are discussed elsewhere [15,20].…”

“…A user subroutine was developed to enable the use of time-or APSE-dependent material properties in the implementation of the evolutionary cyclic plasticity model into ABAQUS. The time-or APSE-dependent material properties such as elastic modulus, yield stress, and kinematic hardening for 316 SS can be found elsewhere [20].…”

“…The details of this work and related results are discussed in Refs. [15,20]. The next step is validation of the evolution cyclic plasticity model through analytical and 3D-FE modeling of the specimen.…”

“…Results from the analytical modeling of 316 SS specimens under uniaxial fatigue loading are presented in Ref. [20]. The 3D-FE modeling results of the fatigue specimens are discussed in Sec.…”

“…Use of field variable-dependent material modeling will allow to take into account the temperature-dependent material behavior during FE simulation of large nuclear components. Based on the evolutionary cyclic plasticity material model, a fully mechanistic fatigue modeling approach for 316 stainless steel was presented in a recent paper [20]. Material parameters as functions of time or accumulated plastic strain energy (APSE) were considered.…”