Modeling Dislocation-Mediated Hydrogen Transport and Trapping in Fcc Metals

2021 ◽  
pp. 1-54
Author(s):  
Theodore Zirkle ◽  
Luke Costello ◽  
Ting Zhu ◽  
David L. McDowell
Keyword(s):  
Transport Model ◽  
Constitutive Relations ◽  
Crack Tip ◽  
Lattice Diffusion ◽  
Hydrogen Transport ◽  
Crack Tip Field ◽  
Coupled Diffusion ◽  
Crystal Plasticity Model ◽  
Physically Based ◽  
Material Ductility

Abstract The diffusion of hydrogen in metals is of interest due to the deleterious influence of hydrogen on material ductility and fracture resistance. It is becoming increasingly clear that hydrogen transport couples significantly with dislocation activity. In this work, we employ a coupled diffusion-crystal plasticity model to incorporate hydrogen transport associated with dislocation sweeping and pipe diffusion in addition to standard lattice diffusion. Moreover, we consider generation of vacancies via plastic deformation and stabilization of vacancies via trapping of hydrogen. The proposed hydrogen transport model is implemented in a physically-based crystal viscoplasticity framework to model the interaction of dislocation substructure and hydrogen migration. In this study, focus is placed on hydrogen transport and trapping within the intense deformation field of a crack tip plastic zone. We discuss the implications of the model results in terms of constitutive relations that incorporate hydrogen effects on crack tip field behavior and enable exploration of hydrogen embrittlement mechanisms.

Numerical Simulation of Hydrogen Transport at a Crack Tip in a Pipeline Steel

2006 ◽  
Author(s):  
Mohsen Dadfarnia ◽  
Petros Sofronis ◽  
Ian Robertson ◽  
Brian P. Somerday ◽  
Govindarajan Muralidharan ◽  
...  
Keyword(s):  
Distribution System ◽  
Large Scale ◽  
Pipeline Steel ◽  
Rapid Assessment ◽  
Crack Tip ◽  
Hydrogen Transport ◽  
Natural Gas Pipeline ◽  
Central Production ◽  
Materials Used ◽  
Pressure Hydrogen

The technology of large scale hydrogen transmission from central production facilities to refueling stations and stationary power sites is at present undeveloped. Among the problems which confront the implementation of this technology is the deleterious effect of hydrogen on structural material properties, in particular at gas pressure of 1000 psi which is the desirable transmission pressure suggested by economic studies for efficient transport. In this paper, a hydrogen transport methodology for the calculation of hydrogen accumulation ahead of a crack tip in a pipeline steel is outlined. The approach accounts for stress-driven transient diffusion of hydrogen and trapping at microstructural defects whose density may evolve dynamically with deformation. The results are used to discuss a lifetime prediction methodology for failure of materials used for pipelines and welds exposed to high-pressure hydrogen. Development of such predictive capability and strategies is of paramount importance to the rapid assessment of using the natural-gas pipeline distribution system for hydrogen transport and of the susceptibility of new alloys tailored for use in the new hydrogen economy.

Mismatch Effect on the Mixed Mode Type Creep Crack within Weldment

2016 ◽  
Vol 853 ◽  
pp. 281-285
Author(s):  
Jun Hui Zhang ◽  
Yan Wei Dai
Keyword(s):  
Mixed Mode ◽  
Stress Triaxiality ◽  
Crack Tip ◽  
Crack Tip Field ◽  
Creep Crack ◽  
Loading Mode ◽  
The Difference ◽  
Engineering Practices ◽  
Mismatch Effect ◽  
Transient And Steady State

Creep crack within weldments are very common in engineering practices, and the cracking location in these welding structures always appears at the HAZ location. The mismatch effect on the mixed mode creep crack is still not clear in these available literatures. The aim of this paper is to investigate the mismatch influence on the creep crack of mixed mode thoroughly. A mixed mode creep crack within HAZ is established in this paper. The leading factor that dominates the creep crack tip field under mixed loading mode is studied. The influences of mismatch effect on mode mixity, stress distribution and stress triaxiality are proposed. The difference of mixed mode creep crack and normal mode I or mode II creep crack are compared. The influence of mixity factor on the transient and steady state creep of crack tip are also analyzed.

INVESTIGATIONS ON THE DYNAMIC NEAR-CRACK-TIP FIELD USING THE GRID METHOD

1988 ◽  
Vol 49 (C3) ◽  
pp. C3-307-C3-312
Author(s):  
K. KUSSMAUL ◽  
T. DEMLER ◽  
A. KLENK
Keyword(s):  
Crack Tip ◽  
Grid Method ◽  
Crack Tip Field

Recent Progress in the 3D Experimentation and Simulation of Nanoindents

2007 ◽  
Vol 550 ◽  
pp. 199-204
Author(s):  
N. Zaafarani ◽  
Franz Roters ◽  
Dierk Raabe
Keyword(s):  
Cross Section ◽  
Focused Ion Beam ◽  
Ion Beam ◽  
Physically Based Model ◽  
Rotation Direction ◽  
Crystal Rotation ◽  
Crystal Plasticity Model ◽  
Physically Based ◽  
Set Up ◽  
Rotation Map

This work studies the rotations of a (111) Cu single crystal due to the application of a conical nanoindent. With the aid of a joint high-resolution field emission SEM-EBSD set-up coupled with serial sectioning in a focused ion beam (FIB) system in the form of a cross-beam 3D crystal orientation microscope (3D EBSD) a 3D rotation map underneath the indent could be extracted. When analyzing the rotation directions in the cross section planes (11-2) perpendicular to the (111) surface plane below the indenter tip we observe multiple transition regimes with steep orientation gradients and changes in rotation direction. A phenomenological and a physically-based 3D elastic-viscoplastic crystal plasticity model are implemented in two finite element simulations adopting the geometry and boundary conditions of the experiment. While the phenomenological model predicts the general rotation trend it fails to describe the fine details of the rotation patterning with the frequent changes in sign observed in the experiment. The physically-based model, which is a dislocation density based constitutive model, succeeded to precisely predict the crystal rotation map compared with the experiment. Both simulations over-emphasize the magnitude of the rotation field near the indenter relative to that measured directly below the indenter tip. However, out of the two models the physically-based model reveals better crystal rotation angles

scholarly journals Mixed-mode crack tip fields in a polycrystalline aluminum alloy

2019 ◽  
Vol 300 ◽  
pp. 11004 ◽  
Author(s):  
Marcel Wicke ◽  
Angelika Brueckner-Foit
Keyword(s):  
Mixed Mode ◽  
Crack Tip ◽  
Strain Partitioning ◽  
Crack Tip Field ◽  
Polycrystalline Aluminum ◽  
Digital Twin ◽  
Crack Tip Fields ◽  
Mixed Mode Crack ◽  
Threshold Regime ◽  
Near Threshold

Carefully performed experiments with long cracks in the near-threshold regime have shown that the crack tip field of these cracks significantly deviate from the expected mode-I butterfly-shaped ones and resemble strongly to mixed-mode crack tip fields. A simulation study using a crystal plasticity (CP) approach has been utilized in order to understand this phenomenon. To this end, a digital twin of an aluminum sample fatigued in the near-threshold regime was generated with the help of electron backscatter diffraction (EBSD) and X-ray tomography. Once set-up, the digital twin was loaded in uniaxial tension using the fast spectral solver implemented in the Düsseldorf Advanced Material Simulation Kit (DAMASK). The versatility of this experimental-computational approach for studying the strain partitioning at the crack tip is demonstrated in this work.

The Influence of Crystallographic Orientations of Grains on Microstructurally Small Cracks Using Crystal Plasticity and Random Grain Structure

2006 ◽  
Author(s):  
I. Simonovski ◽  
L. Cizelj
Keyword(s):  
Crystal Plasticity ◽  
Crack Tip ◽  
Maximum Load ◽  
Grain Structure ◽  
Crystal Plasticity Model ◽  
Grain Orientations ◽  
Small Cracks ◽  
Crack Tip Opening ◽  
Soft Grains ◽  
Crystallographic Orientations

A plane-strain finite element crystal plasticity model of microstructurally small stationary crack emanating at a surface grain in a 316L stainless steel is proposed. The model consisting of 212 randomly shaped, sized and oriented grains is loaded monotonically in uniaxial tension to a maximum load of 1.12Rp0.2 (280 MPa). The influence that a random grain structure imposes on a Stage I crack is assessed by calculating the crack tip opening (CTOD) and sliding displacements (CTSD), considering also different crystallographic orientations. It is shown that certain crystallographic orientations result in a cluster of soft grains around the crack-containing grain. In these cases the crack tip can become apart of the localized strain, resulting in a large CTOD value. This effect, resulting from the overall grain orientations and sizes, can have a greater impact on the CTOD than the local grain orientation. On the other hand, when a localized soft response is formed away from the crack, the localized strain does not affect the crack tip directly, resulting in a small CTOD value. The resulting difference in CTOD can be up to a factor of 4, depending upon the crystallographic set. Grains as far as 6xCracklength significantly influence that crack tip parameters. It was also found the a larger crack-containing grain tends to increase the CTOD.

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