Fatigue Crack Initiation Simulation in Pure Iron Polycrystalline Aggregate

Abstract

A numerical study was conducted to evaluate the fatigue crack initiation stage in pure α-iron. A two-dimensional synthetic polycrystalline aggregate was generated with Voronoi tessellation to represent the microstructure. Low-cycle fatigue experiments under fully reversed strain-controlled loading were conducted for different strain amplitudes. The stable stress-strain hysteresis loops were used to calibrate a non-linear kinematic hardening model for metal plasticity suitable for cyclic simulations. An existing procedure based on the Tanaka-Mura model for fatigue crack initiation was extended to body-centered cubic lattice to account for two orthogonal slip systems as potential crack locations. This procedure was applied for fully reversed fatigue simulations with various stress amplitudes ranging from low-cycle to high-cycle fatigue regime. The effect of the stress level on the crack morphology and the fatigue crack initiation life was evaluated. Finally the applicability and limitations of the proposed procedure was discussed.

Simulation-based Understanding of the Critical Resolved Shear Stress Relevance for the Fatigue Performance of Metallic Materials

“…slip band length) d, the average shear stress range Δτ on the slip band, the shear modulus G, the crack initiation energy Wc, Poisson's ratio ν, and the CRSS [10][11][12][13][14]. A more extended and detailed description of the implementation of the TM equation into FEM-based modelling and simulation of the crack initiation process has been reported in publications of the authors of this study in [5,[10][11][12][15][16][17][18] and by other researchers, too, in [13,14,19,20].…”

Development of a Method for Evaluating Microstructurally Small Fatigue Crack Initiation and Growth by Using an Automatic System for <i>In Situ</i> Observation in Conjunction with a Digital-Image Correlation Technique

“…Hide-aki NISHIKAWA* and Yoshiyuki FURUYA some researchers have recently developed methods that utilize the crystal plasticity finite-element method. 9,10) On the other hand, methods based on the continuum mechanics theory are more effective for the evaluation of mechanically small cracks. The effectiveness of elastic-plastic fracture mechanics in calculating the crack-opening stress by using the Dugdale model has been reported.…”

Data Assimilation in the Welding Process for Analysis of Weld Toe Geometry and Heat Source Model

“…The problem in such fracture mechanics-based methods is that they require an assumption of initial crack size to calculate stress intensity factor, and do not explicitly consider the effects of microstructure. To overcome these limitations, microstructure-based fatigue modeling has recently been developed with micromechanics, 9,10) crystal plasticity, [11][12][13] and data-driven approaches, 14) and these techniques have been applied for fatigue life prediction of welded joints. 14,15) A common problem in these numerical calculations is the preparation of the input variables such as weld toe geometries, heat source parameters in welding simulation, crystal plasticity parameters, and crack initiation criterion, which are difficult to measure directly by experiment.…”