Ductile-Brittle Behavior along Crack Front and T-Stress

2011 ◽  
Vol 465 ◽  
pp. 69-72
Author(s):  
Alena Uhnáková ◽  
Anna Machová ◽  
Petr Hora

We present new results of molecular dynamic (MD) simulations in 3D bcc iron crystals with embedded central through crack (001)[110] of Griffith type loaded in mode I. Two different sample geometries of the same crystallographic orientation were tested with negative and positive values of the T-stress, which change the ductile-brittle behavior along the crack front in 3D. This phenomenon is explained in the framework of stress analysis, both on the continuum and atomistic level.

2016 ◽  
Vol 258 ◽  
pp. 45-48 ◽  
Author(s):  
Vladimír Pelikán ◽  
Petr Hora ◽  
Anna Machová ◽  
Radek Kolman ◽  
Alena Uhnáková

We present new results of molecular dynamic (MD) simulations in 3D bcc iron crystals with edge cracks (001)[010] and (-110)[110] loaded in mode I. Different sample geometries of SEN type were tested with negative and positive values of T-stress according to continuum prediction by Fett.


2007 ◽  
Vol 567-568 ◽  
pp. 61-64 ◽  
Author(s):  
Alena Spielmannová ◽  
Anna Machová ◽  
Petr Hora

The paper presents results of molecular dynamic (MD) simulations in 3D bcc iron crystals with edge pre-existing cracks (001)[110] and (110) [110] (crack plane/crack front) loaded uni-axially in tension mode I at temperature of 300 K. The iron crystals in MD have the same orientation and similar geometry as in our recent fracture tests performed at room temperature on iron (3wt.%Si) single crystals [1].


2005 ◽  
Vol 482 ◽  
pp. 131-134
Author(s):  
V. Pelikán ◽  
Petr Hora ◽  
Anna Machová ◽  
Michal Landa

Results of several parallel molecular dynamics crack simulations in bcc iron crystals with up to 128 million atoms are presented. The crack (001)[010] of Griffith type is loaded in Mode I. We observe dislocation emission and twinning near the free sample surfaces and later plastically induced crack initiation.


2010 ◽  
Vol 77 (2) ◽  
pp. 184-192 ◽  
Author(s):  
J. Prahl ◽  
A. Machová ◽  
A. Spielmannová ◽  
M. Karlík ◽  
M. Landa ◽  
...  
Keyword(s):  
Mode I ◽  

2019 ◽  
Author(s):  
Dimitrios Kolokouris ◽  
Iris Kalenderoglou ◽  
Panagiotis Lagarias ◽  
Antonios Kolocouris

<p>We studied by molecular dynamic (MD) simulations systems including the inward<sub>closed</sub> state of influenza A M2 protein in complex with aminoadamantane drugs in membrane bilayers. We varied the M2 construct and performed MD simulations in M2TM or M2TM with amphipathic helices (M2AH). We also varied the lipid bilayer by changing either the lipid, DMPC or POPC, POPE or POPC/cholesterol (chol), or the lipids buffer size, 10x10 Å<sup>2 </sup>or 20x20 Å<sup>2</sup>. We aimed to suggest optimal system conditions for the computational description of this ion channel and related systems. Measures performed include quantities that are available experimentally and include: (a) the position of ligand, waters and chlorine anion inside the M2 pore, (b) the passage of waters from the outward Val27 gate of M2 S31N in complex with an aminoadamantane-aryl head blocker, (c) M2 orientation, (d) the AHs conformation and structure which is affected from interactions with lipids and chol and is important for membrane curvature and virus budding. In several cases we tested OPLS2005, which is routinely applied to describe drug-protein binding, and CHARMM36 which describes reliably protein conformation. We found that for the description of the ligands position inside the M2 pore, a 10x10 Å<sup>2</sup> lipids buffer in DMPC is needed when M2TM is used but 20x20 Å<sup>2</sup> lipids buffer of the softer POPC; when M2AH is used all 10x10 Å<sup>2</sup> lipid buffers with any of the tested lipids can be used. For the passage of waters at least M2AH with a 10x10 Å<sup>2</sup> lipid buffer is needed. The folding conformation of AHs which is defined from hydrogen bonding interactions with the bilayer and the complex with chol is described well with a 10x10 Å<sup>2</sup> lipids buffer and CHARMM36. </p>


Polymers ◽  
2021 ◽  
Vol 13 (4) ◽  
pp. 492
Author(s):  
Zhen Pei Chow ◽  
Zaini Ahmad ◽  
King Jye Wong ◽  
Seyed Saeid Rahimian Koloor ◽  
Michal Petrů

This paper aims to propose a temperature-dependent cohesive model to predict the delamination of dissimilar metal–composite material hybrid under Mode-I and Mode-II delamination. Commercial nonlinear finite element (FE) code LS-DYNA was used to simulate the material and cohesive model of hybrid aluminium–glass fibre-reinforced polymer (GFRP) laminate. For an accurate representation of the Mode-I and Mode-II delamination between aluminium and GFRP laminates, cohesive zone modelling with bilinear traction separation law was implemented. Cohesive zone properties at different temperatures were obtained by applying trends of experimental results from double cantilever beam and end notched flexural tests. Results from experimental tests were compared with simulation results at 30, 70 and 110 °C to verify the validity of the model. Mode-I and Mode-II FE models compared to experimental tests show a good correlation of 5.73% and 7.26% discrepancy, respectively. Crack front stress distribution at 30 °C is characterised by a smooth gradual decrease in Mode-I stress from the centre to the edge of the specimen. At 70 °C, the entire crack front reaches the maximum Mode-I stress with the exception of much lower stress build-up at the specimen’s edge. On the other hand, the Mode-II stress increases progressively from the centre to the edge at 30 °C. At 70 °C, uniform low stress is built up along the crack front with the exception of significantly higher stress concentrated only at the free edge. At 110 °C, the stress distribution for both modes transforms back to the similar profile, as observed in the 30 °C case.


2017 ◽  
Vol 17 (2) ◽  
pp. 363-378 ◽  
Author(s):  
Ayad Arab Kakei ◽  
Mainul Islam ◽  
Jinsong Leng ◽  
Jayantha A Epaarachchi

Mode I fracture analysis being employed to study delamination damage in fibre-reinforced composite structures under in-plane and out-of-plane load applications. However, due to the significantly low yield strength of the matrix material and the infinitesimal thickness of the interface matrix layer, the actual delamination process can be assumed as a partially plastic process (elasto-plastic). A simple elasto-plastic model based on the strain field in the vicinity of the crack front was developed for Mode I crack propagation. In this study, a double cantilever beam experiment has been performed to study the proposed process using a 0/90-glass woven cloth sample. A fibre Bragg grating sensor has embedded closer to the delamination to measure the strain at the vicinity of the crack front. Strain energy release rate was calculated according to ASTM D5528. The model predictions were comparable with the calculated values according to ASTM D5528. Subsequently, a finite element analysis on Abaqus was performed using ‘Cohesive Elements’ to study the proposed elasto-plastic behaviour. The finite element analysis results have shown a very good correlation with double cantilever beam experimental results, and therefore, it can be concluded that Mode I delamination process of an fibre-reinforced polymer composite can be monitored successfully using an integral approach of fibre Bragg grating sensors measurements and the prediction of a newly proposed elasto-plastic model for Mode I delamination process.


2017 ◽  
Vol 138 ◽  
pp. 315-322 ◽  
Author(s):  
Anna Machová ◽  
Alena Uhnáková ◽  
Petr Hora
Keyword(s):  
Mode I ◽  
T Stress ◽  

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