Atomistic Study of Deformation and Failure Behavior in Nanocrystalline Mg

MRS Advances ◽  
2016 ◽  
Vol 1 (58) ◽  
pp. 3859-3864 ◽  
Author(s):  
Garvit Agarwal ◽  
Gabriel Paun ◽  
Ramakrishna R. Valisetty ◽  
Raju Namburu ◽  
Arunachalam M. Rajendran ◽  
...  
Keyword(s):  
Grain Size ◽  
Large Scale ◽  
Md Simulations ◽  
Uniaxial Tensile ◽  
Failure Behavior ◽  
Deformation And Failure ◽  
Uniaxial Tensile Stress ◽  
Atomistic Study ◽  
Eam Potential ◽  
Critical Grain Size

ABSTRACTLarge scale molecular dynamics (MD) simulations are carried out to investigate the failure response of nanocrystalline Mg using the EAM potential under conditions of uniaxial tensile stress and uniaxial tensile strain loading. The MD simulations are carried out at a strain rate of 109s-1 for grain sizes in the range of 10 nm to 30 nm. The effect of grain size on the strength of the metal is investigated and the critical grain size for transition to inverse Hall-Petch regime is identified.

scholarly journals Molecular Dynamics Study on Deformation Mechanism of Grain Boundaries in Magnesium Crystal: Based on Coincidence Site Lattice Theory

2018 ◽  
Vol 2018 ◽  
pp. 1-10 ◽  
Author(s):  
Ken-ichi Saitoh ◽  
Kohei Kuramitsu ◽  
Tomohiro Sato ◽  
Masanori Takuma ◽  
Yoshimasa Takahashi
Keyword(s):  
Molecular Dynamics ◽  
Deformation Mechanism ◽  
Coincidence Site Lattice ◽  
Md Simulations ◽  
Uniaxial Tensile ◽  
High Angle ◽  
Site Lattice ◽  
Embedded Atom ◽  
Significant Difference ◽  
Eam Potential

As for magnesium (Mg) alloys, it has been noted that they are inferior to plastic deformation, but improvement in the mechanical properties by further refinement of grain size has been recently suggested. It means the importance of atomistic view of polycrystalline interface of Mg crystal. In this study, to discuss the deformation mechanism of polycrystalline Mg, atomistic grain boundary (GB) models by using coincidence site lattice (CSL) theory are constructed and are simulated for their relaxed and deformatted structures. First, GB structures in which the axis of rotation is in [11¯00] direction are relaxed at 10 Kelvin, and the GB energies are evaluated. Then, the deformation mechanism of each GB model under uniaxial tensile loading is observed by using the molecular dynamics (MD) method. The present MD simulations are based on embedded atom method (EAM) potential for Mg crystal. As a result, we were able to observe atomistically a variety of GB structures and to recognize significant difference in deformation mechanism between low-angle GBs and high-angle GBs. A close scrutiny is made on phenomena of dislocation emission processes peculiar to each atomistic local structure in high-angle GBs.

scholarly journals Material Selection and Process Configuration for Free-Form, Voluminous and Textile-Based Multi-Material-Design by the Example of a Bucket Seat

2017 ◽  
Vol 742 ◽  
pp. 302-309 ◽  
Author(s):  
Jonas Stiller ◽  
Kay Schäfer ◽  
Frank Helbig ◽  
Jürgen Tröltzsch ◽  
Daisy Nestler ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Large Scale ◽  
Material Selection ◽  
Hybrid Composites ◽  
Material Design ◽  
Free Form ◽  
Failure Behavior ◽  
Scale Production ◽  
Structure Property ◽  
Deformation And Failure

Hybrid textile-based composites possess an enormous potential for energy and resource efficient large-scale production, with freedom in and high specific mechanical properties. This paper covers the connection of available and established production processes for textiles in a differential process chain for the manufacturing of complex shaped and elastic sandwich components. The technology enables both stiffness and comfort through elasticity.OLU-Preg®-organic sheets, polyurethane foam cores and 3D-spacer fabrics form the targeted properties of demonstrator models. This article refers to the demonstrator part “bucket seat”. To show the benefit of complex composite material, the lightweight and mechanical properties of the sandwich structures are tested in several variations of core and comfort shapes. Absolute and specific improvements of performance are shown in static and dynamic examinations. An Analysis of coupling effects, deformation and failure behavior of the multi-material design (MMD) complete the scientific approach of the structure-property relationships of hybrid composites.

Short-range dislocation interactions using molecular dynamics: Annihilation of screw dislocations

1998 ◽  
Vol 13 (12) ◽  
pp. 3478-3484 ◽  
Author(s):  
S. Swaminarayan ◽  
R. LeSar ◽  
P. Lomdahl ◽  
D. Beazley
Keyword(s):  
Molecular Dynamics ◽  
Large Scale ◽  
Dislocation Dynamics ◽  
Annihilation Process ◽  
Screw Dislocations ◽  
Linear Elastic ◽  
Embedded Atom ◽  
Dynamics Simulations ◽  
Atomistic Study ◽  
Eam Potential

We present results of a large-scale atomistic study of the annihilation of oppositely signed screw dislocations in an fcc metal using molecular dynamics (MD) and an Embedded-Atom-Method (EAM) potential for Cu. The mechanisms of the annihilation process are studied in detail. From the simulation results, we determined the interaction energy between the dislocations as a function of separation. These results are compared with predictions from linear elasticity to examine the onset of non-linear-elastic interactions. The applicability of heuristic models for annihilation of dislocations in large-scale dislocation dynamics simulations is discussed in the light of these results.

Finite Element Modeling of a Mechanically Stabilized Earth Trial Wall

2021 ◽  
pp. 036119812110164
Author(s):  
Andrew Lees ◽  
Michael Dobie
Keyword(s):  
Finite Element ◽  
Shear Strength ◽  
Retaining Wall ◽  
Back Analysis ◽  
Soil Parameters ◽  
Failure Behavior ◽  
Valuable Insight ◽  
Deformation And Failure ◽  
First Case ◽  
Soil Shear Strength

Polymer geogrid reinforced soil retaining walls have become commonplace, with routine design generally carried out by limiting equilibrium methods. Finite element analysis (FEA) is becoming more widely used to assess the likely deformation behavior of these structures, although in many cases such analyses over-predict deformation compared with monitored structures. Back-analysis of unit tests and instrumented walls improves the techniques and models used in FEA to represent the soil fill, reinforcement and composite behavior caused by the stabilization effect of the geogrid apertures on the soil particles. This composite behavior is most representatively modeled as enhanced soil shear strength. The back-analysis of two test cases provides valuable insight into the benefits of this approach. In the first case, a unit cell was set up such that one side could yield thereby reaching the active earth pressure state. Using FEA a test without geogrid was modeled to help establish appropriate soil parameters. These parameters were then used to back-analyze a test with geogrid present. Simply using the tensile properties of the geogrid over-predicted the yield pressure but using an enhanced soil shear strength gave a satisfactory comparison with the measured result. In the second case a trial retaining wall was back-analyzed to investigate both deformation and failure, the failure induced by cutting the geogrid after construction using heated wires. The closest fit to the actual deformation and failure behavior was provided by using enhanced fill shear strength.

scholarly journals Investigation of Damage Evolution in Heterogeneous Rock Based on the Grain-Based Finite-Discrete Element Model

Materials ◽  
2021 ◽  
Vol 14 (14) ◽  
pp. 3969
Author(s):  
Shirui Zhang ◽  
Shili Qiu ◽  
Pengfei Kou ◽  
Shaojun Li ◽  
Ping Li ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Grain Size ◽  
Tensile Strength ◽  
Grain Orientation ◽  
Damage Evolution ◽  
Discrete Element ◽  
Uniaxial Tensile ◽  
Tensile Cracks ◽  
Rock Heterogeneity ◽  
Heterogeneous Rock

Granite exhibits obvious meso-geometric heterogeneity. To study the influence of grain size and preferred grain orientation on the damage evolution and mechanical properties of granite, as well as to reveal the inner link between grain size‚ preferred orientation, uniaxial tensile strength (UTS) and damage evolution, a series of Brazilian splitting tests were carried out based on the combined finite-discrete element method (FDEM), grain-based model (GBM) and inverse Monte Carlo (IMC) algorithm. The main conclusions are as follows: (1) Mineral grain significantly influences the crack propagation paths, and the GBM can capture the location of fracture section more accurately than the conventional model. (2) Shear cracks occur near the loading area, while tensile and tensile-shear mixed cracks occur far from the loading area. The applied stress must overcome the tensile strength of the grain interface contacts. (3) The UTS and the ratio of the number of intergrain tensile cracks to the number of intragrain tensile cracks are negatively related to the grain size. (4) With the increase of the preferred grain orientation, the UTS presents a “V-shaped” characteristic distribution. (5) During the whole process of splitting simulation, shear microcracks play the dominant role in energy release; particularly, they occur in later stage. This novel framework, which can reveal the control mechanism of brittle rock heterogeneity on continuous-discontinuous trans-scale fracture process and microscopic rock behaviour, provides an effective technology and numerical analysis method for characterizing rock meso-structure. Accordingly, the research results can provide a useful reference for the prediction of heterogeneous rock mechanical properties and the stability control of engineering rock masses.

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