Formation of carbon Cottrell atmospheres and their effect on the stress field around an edge dislocation

2017 ◽  
Vol 129 ◽  
pp. 16-19 ◽  
Author(s):  
Osamu Waseda ◽  
Roberto GA Veiga ◽  
Julien Morthomas ◽  
Patrice Chantrenne ◽  
Charlotte S. Becquart ◽  
...  
2017 ◽  
Vol 2017 ◽  
pp. 1-7 ◽  
Author(s):  
Burak Bal

The effects of relaxation stress on the hydrogen concentration in Niobium- (Nb-) H media were investigated by iterative numerical modeling approach. To calculate the transformation strain, relaxation stress, and corresponding relaxed hydrogen concentration around an edge dislocation, a new third-order polynomial formulation was utilized in the model. With the aid of this polynomial, hydrogen induced relaxation stress never exceeds the dislocation stress, which indicates that the total stress field never turns to compressive state and diverges the results. The current model calculates the hydrogen concentration not only in the vicinity of an edge dislocation but also far away from the dislocation. Furthermore, the effect of relaxation stress on the interaction energy was also captured in the model. Overall, the current findings shed light on the complicated hydrogen embrittlement mechanisms of metallic materials by demonstrating that hydrogen induced relaxation has a significant effect on the hydrogen atom concentration and the interaction energy between the existing internal stress field and the solute hydrogen atom.


1993 ◽  
Vol 60 (3) ◽  
pp. 743-748 ◽  
Author(s):  
P. Kelly ◽  
D. A. Hills ◽  
D. Nowell

Solutions are found for the state of stress obtaining along the interface between two bonded quarter planes, induced by an edge dislocation located at an arbitrary point on the interface. Explicit asymptotic expressions are given for the stress at points close to the free surfaces.


Metals ◽  
2019 ◽  
Vol 9 (10) ◽  
pp. 1040 ◽  
Author(s):  
Hoang-Thien Luu ◽  
Roberto G. A. Veiga ◽  
Nina Gunkelmann

It has long been known that iron undergoes a phase transformation from body-centered cubic/ α structure to the metastable hexagonal close-packed/ ε phase under high pressure. However, the interplay of line and planar defects in the parent material with the transformation process is still not fully understood. We investigated the role of twins, dislocations, and Cottrell atmospheres in changing the crystalline iron structure during this phase transformation by using Monte Carlo methods and classical molecular dynamics simulations. Our results confirm that embryos of ε -Fe nucleate at twins under hydrostatic compression. The nucleation of the hcp phase is observed for single crystals containing an edge dislocation. We observe that the buckling of the dislocation can help to nucleate the dense phase. The crystal orientations between the initial structure α -Fe and ε -Fe in these simulations are 110 b c c | | 0001 h c p . The presence of Cottrell atmospheres surrounding an edge dislocation in bcc iron retards the development of the hcp phase.


2021 ◽  
Vol 2021 (3) ◽  
pp. 24-37
Author(s):  
M. I. Lugovy ◽  
◽  
D. G. Verbylo ◽  
M. P. Brodnikovskyy ◽  
◽  
...  

The formation of stochastic shear stress field in the glide plane in the substitutional solid solution was investigated by computer simulation. If the atoms in the crystal lattice nodes of the substitutional solid solution are considered as a kind of point defects in the virtual solvent medium, the shear stress distribution in the glide plane can be calculated based on the interaction of edge dislocation and such defects. For concentrated solid solutions, the shear stress will be a normally distributed random value with zero mathematical expectation. The standard deviation of this distribution will be the greater the greater the effective distortion of crystalline lattice of the alloy. In the case of dilute solid solution, where one of the components has a predominant content, the simulation gives shear stress distribution in the glide plane, where large peaks are separated from each other by wide areas of near-zero stresses. Thus, there are separate discrete obstacles in the form of large stress peaks for the edge dislocation in the glide plane in dilute solid solution, and the space between the peaks is practically stress-free. The average distance between large peaks correlates with the average distance between the atoms of those components that are few in solution, if total atomic fraction of these components is considered. Thus, the proposed modeling gives a very realistic shear stress distribution in the glide plane for concentrated and dilute substitutional solid solutions with fcc and bcc structures. This can be useful in further modeling the yield strength in multicomponent alloys. Keywords: dislocation, distorsion, shear stresses.


2019 ◽  
Vol 36 (1) ◽  
pp. 55-72 ◽  
Author(s):  
S. C. Tseng ◽  
C. K. Chao ◽  
F. M. Chen

ABSTRACTThe stress field induced by an edge dislocation or a point force located near a coated triangle-like hole in an infinite plate is provided in this paper. Based on the method of analytical continuation and the technique of conformal mapping in conjunction with the alternation technique, a series solution for the displacement and stresses in the coating layer and the matrix is obtained analytically. Examples for the interaction between an edge dislocation and a coated triangle-like hole for various material constant combinations, coating thicknesses and shape factors are discussed. The analysis discovers that the so-called trapping mechanism of dislocations is more likely to exist near a coated triangle-like hole. The result shows that the dislocation will first be repelled by the coating layer and then attracted by a hole when the coating layer is slightly stiffer than the matrix. However, when the coating layer is sufficiently thin, the dislocation will always be attracted by a hole even the coating layer is stiffer than the matrix.


Sign in / Sign up

Export Citation Format

Share Document