Damage Evolution Due to Extremely Low-Cycle Fatigue for Inconel 718 Alloy

Abstract

This paper evaluates the damage evolution process under extremely low-cycle fatigue (ELCF). The study explores the damage behavior under different stress states. The influence of the multiaxial state of stress on the metal’s life is determined. Two different stress states were examined: (a) axisymmetric and (b) plane-strain. The study is based on the modified Mohr–Coulomb (MMC) ductile fracture criterion that was extended to cover the ELCF regime in a previous research study. Four distinctive geometries are designed to study the effect of different stress states on ELCF life and damage evolution. The damage model is calibrated for life prediction to agree with the ELCF experimental results. The investigation of the damage evolution behavior is dependent on equivalent plastic strain, stress triaxiality, Lode angle, and cyclic loading effect. The damage evolution is extracted from Abaqus finite element simulations and plotted versus the equivalent plastic strain. The damage accumulation shows nonlinear evolution behavior under cyclic loading conditions. SEM images were taken to further study the microscopic failure mechanisms of ELCF.

Feasibility Study on Strain-Based Seismic Design Criteria for Nuclear Components

“…When metal components experience very high plastic strain cyclic loading, the ductile fracture failure mechanism takes place as part of the very low cycle fatigue failure [7]. In this high plastic strain condition, material ductility dominantly depends on the stress triaxiality described in Section 2.3.…”

“…At very low-reversing dynamic loads, it has been studied that the failure mode is almost the same as a ductile fracture [7]. Therefore, as a predictable seismic failure mode, the ductile fracture needs to be considered when the earthquake levels are very high and contain relatively low cycle frequency contents.…”

Fatigue Design and Defects in Metals and Alloys

“…Twelve research articles have been published in this Special Issue of Metals. The subjects are multidisciplinary, including (i) the effect of microstructural defects on the high and very high cycle fatigue strength of metallic materials [1][2][3][4][5], (ii) probabilistic fatigue prognosis incorporating the size of defects and control volume [2,4,6], (iii) the effects of plasticity, high temperature, and aggressive environment on the fatigue response [7][8][9], (iv) thermo-chemo-mechanical treatments to mitigate the detrimental effect of defects on the fatigue strength [10,11], and (v) non-destructive techniques to detect fatigue critical defects [12].…”

The Numerical Analysis of the In-Plane Constraint Influence on the Behavior of the Crack Subjected to Cyclic Loading

“…In contrast to previously cited papers in [ 22 ] the authors tried to explain the influence of geometry on fatigue behavior in a low-cycle range with stress triaxiality and Lode parameter. Application of parameters describing the state of stress instead of a probabilistic approach was a promising direction since in fatigue analyses there were no attempts to introduce a parameter that could quantitatively describe the influence of the size and shape of the applied specimen.…”