scholarly journals Molecular Dynamics Simulation Study of the Mechanical Properties of Nanocrystalline Body-Centered Cubic Iron

Surfaces ◽  
2020 ◽  
Vol 3 (3) ◽  
pp. 381-391
Author(s):  
Jan Herman ◽  
Marko Govednik ◽  
Sandeep P. Patil ◽  
Bernd Markert
Keyword(s):  
Mechanical Properties ◽  
Molecular Dynamics ◽  
Strain Rate ◽  
Tensile Tests ◽  
Dynamics Simulation ◽  
Uniaxial Tensile ◽  
Body Centered Cubic ◽  
Bcc Iron ◽  
Average Grain Size ◽  
Study Results

In the present work, the mechanical properties of nanocrystalline body-centered cubic (BCC) iron with an average grain size of 10 Å were investigated using molecular dynamics (MD) simulations. The structure has one layer of crystal grains, which means such a model could represent a structure with directional crystallization. A series of uniaxial tensile tests with different strain rates and temperatures was performed until the full rupture of the model. Moreover, tensile tests of the models with a void at the center and shear tests were carried out. In the tensile test simulations, peak stress and average values of flow stress increase with strain rate. However, the strain rate does not affect the elasticity modulus. Due to the presence of void, stress concentrations in structure have been observed, which leads to dislocation pile-up and grain boundary slips at lower strains. Furthermore, the model with the void reaches lower values of peak stresses as well as stress overshoot compared to the no void model. The study results provide a better understanding of the mechanical response of nanocrystalline BCC iron under various loadings.

scholarly journals Insight Into the Strengthening Mechanism of the Al-Induced Cross-Linked Calcium Aluminosilicate Hydrate Gel: A Molecular Dynamics Study

2021 ◽  
Vol 7 ◽  
Author(s):  
Gaozhan Zhang ◽  
Yang Li ◽  
Jun Yang ◽  
Qingjun Ding ◽  
Daosheng Sun
Keyword(s):  
Mechanical Properties ◽  
Molecular Dynamics ◽  
Coupling Effect ◽  
Failure Process ◽  
Three Dimensional ◽  
Tensile Tests ◽  
Strengthening Mechanism ◽  
Dynamics Simulation ◽  
Uniaxial Tensile ◽  
Calcium Aluminosilicate

Understanding and controlling the mechanical properties of calcium aluminosilicate hydrate (C-A-S-H) gel is essential to the performance improvement of cementing materials. This study characterizes the mechanical properties and failure mechanism of cross-linked C-A-S-H that have Al/Si ratios ranging from 0 to 0.20 by employing the reactive molecular dynamics simulation. In these constructed C-A-S-H models, the Al-induced cross-linking effect on the aluminosilicate chains is well reproduced. With the incorporation of aluminate species, layered C-S-H structure gradually transforms into three-dimensional C-A-S-H. The uniaxial tensile tests show that Al-induced cross-links significantly increase the cohesive force and stiffness of C-A-S-H along both y- and z-directions. In the C-A-S-H model with the Al/Si ratio equal to 0.2, in which all the bridging sites are cross-linked, the toughness along y-direction significantly improves the interlayer mechanical properties compared to those within the layers. The deformation mechanism of the C-A-S-H structure is also studied. Results show that the depolymerization of the calcium aluminosilicate skeleton is the main route to uptake the loading energy. Both the increase of y- and z-directional strength of the structure can be related to the increasing polymerization of aluminosilicate chains along that direction. This demonstrates the important role of aluminosilicate chains in resisting the external tensile loading. Besides, during the failure process in C-A-S-H elongation, the hydrolysis reactions of calcium silicate skeleton are caused by the coupling effect of loading and interlayer water “attack.” While the Al-O-Si bond breakage results from the protonation of bridging oxygen atom, the hydrolytic reaction of Si-O-Si is initiated by five-coordinate silicon formation. Both pathways weaken the bridging bond and thus result in the breakage of T-O-Si, where T is Al or Si.

Molecular Dynamics Study on Uniaxial Compression Transformation of Magnesium Alloy

NANO ◽  
2021 ◽  
pp. 2150118
Author(s):  
Qianhua Yang ◽  
Chun Xue ◽  
Zhibing Chu ◽  
Yugui Li ◽  
Lifeng Ma
Keyword(s):  
Mechanical Properties ◽  
Molecular Dynamics ◽  
Phase Transformation ◽  
Magnesium Alloy ◽  
Strain Rate ◽  
Uniaxial Compression ◽  
Dynamics Simulation ◽  
Basic Knowledge ◽  
Transformation Mechanism ◽  
Different Temperatures

As a new method of calculating materials, molecular dynamics simulation can effectively reproduce the mechanical behavior of materials at the atomic level. In this paper, through the construction of the AZ31 magnesium alloy model, the uniaxial compression deformation of magnesium alloy at different temperatures and strain rate is simulated by molecular dynamics method, the mechanical properties and microstructure changes of magnesium alloy are analyzed, the phase transformation mechanism of magnesium alloy under uniaxial compression is revealed, and the effects of temperature and strain rate on the phase transformation of magnesium alloy are explored at the nanometer scale. It provides a theoretical basis and necessary basic knowledge for the design and development of Mg-based nanostructured alloys with excellent mechanical properties.

Recycling without Melting: An Alternative Approach to Aluminum Scrap Recovery

2016 ◽  
Vol 682 ◽  
pp. 284-289 ◽  
Author(s):  
Mateusz Wędrychowicz ◽  
Łukasz Wzorek ◽  
Tomasz Tokarski ◽  
Piotr Noga ◽  
Jakub Wiewióra
Keyword(s):  
Mechanical Properties ◽  
Hot Extrusion ◽  
Tensile Tests ◽  
Charge Material ◽  
Machining Process ◽  
Uniaxial Tensile ◽  
Recycling Process ◽  
Aluminum Chips ◽  
Study Results ◽  
A Charge

Method of scrap recovery by hot extrusion in a contrast to traditional aluminum recycling process distinguishes itself with a low energy consumption and high recovery efficiency. Additionally, this type of recycling allows to recover materials even from highly fragmented forms of metal like chips, foils or filings by omitting melting procedure. In the present study results of 413.0 aluminum chips plastic consolidation will be presented. Chips after machining process were used as a charge material for the entire recycling process. In order to determined the best emulsion elimination method, three separate processes such as centrifugation, annealing and pressing were carried out. In result dry, wet and cleaned chips in a form of cylindrical billets were hot extruded into longitudinal square cross-section profiles. Mechanical properties were examined by uniaxial tensile tests while microstructure observations were performed by means of scanning electron microscopy. It has been showed that emulsion elimination by annealing gives the best results while at the same time all extruded materials revealed no significant differences in mechanical properties.

scholarly journals Investigation on the Tensile Behavior of Graphene-Aluminum Nano-Laminated Composites by Molecular Dynamics Simulation

2019 ◽  
Vol 804 ◽  
pp. 1-6
Author(s):  
Jia Qi Zhu ◽  
Qing Sheng Yang ◽  
Xia Liu
Keyword(s):  
Molecular Dynamics ◽  
Tensile Strength ◽  
Young’S Modulus ◽  
Young's Modulus ◽  
Laminated Composite ◽  
High Strength ◽  
Tensile Tests ◽  
Dynamics Simulation ◽  
Uniaxial Tensile ◽  
Al Composite

Graphene-aluminum (Gr/Al) composite laminated by aluminum (Al) and graphene sheets alternately has excellent mechanical properties thanks to the high strength, high Young’s modulus and the two-dimensional atomic structure of graphene. In this study, the uniaxial tensile properties of Gr/Al nano-laminated composite are studied by molecular dynamics (MD) method. It is found that the thickness of Al layer has a significant effect on the tensile strength and Yang’s modulus of the Gr/Al composite. Composite with a smaller thickness of Al layer shows better properties. Graphene not only block propagation of dislocations, but bear most of the loads, resulting in higher Young's modulus, tensile strength and failure strain of the composites than those of pure Al. The simulation of temperature-effect shows that the Gr/Al composite is difficult to arise plastic deformation at low temperature, which lead to a higher strength and modulus of the composite. In addition, the effect of graphene stacking on the properties of composites is investigated. Through tensile tests at the vertical and parallel interfaces, it is found that graphene stacking may lead to a reduced performance of the composite.

scholarly journals Molecular Dynamics Simulation on Mechanical and Piezoelectric Properties of Boron Nitride Honeycomb Structures

Nanomaterials ◽  
2019 ◽  
Vol 9 (7) ◽  
pp. 1044 ◽  
Author(s):  
Lu Xie ◽  
Tianhua Wang ◽  
Chenwei He ◽  
Zhihui Sun ◽  
Qing Peng
Keyword(s):  
Mechanical Properties ◽  
Molecular Dynamics ◽  
Boron Nitride ◽  
Strain Rate ◽  
Room Temperature ◽  
Piezoelectric Properties ◽  
Piezoelectric Effect ◽  
Failure Strain ◽  
Dynamics Simulation ◽  
Honeycomb Structures

Boron nitride honeycomb structure is a new three-dimensional material similar to carbon honeycomb, which has attracted a great deal of attention due to its special structure and properties. In this paper, the tensile mechanical properties of boron nitride honeycomb structures in the zigzag, armchair and axial directions are studied at room temperature by using molecular dynamics simulations. Effects of temperature and strain rate on mechanical properties are also discussed. According to the observed tensile mechanical properties, the piezoelectric effect in the zigzag direction was analyzed for boron nitride honeycomb structures. The obtained results showed that the failure strains of boron nitride honeycomb structures under tensile loading were up to 0.83, 0.78 and 0.55 in the armchair, zigzag and axial directions, respectively, at room temperature. These findings indicated that boron nitride honeycomb structures have excellent ductility at room temperature. Moreover, temperature had a significant effect on the mechanical and tensile mechanical properties of boron nitride honeycomb structures, which can be improved by lowering the temperature within a certain range. In addition, strain rate affected the maximum tensile strength and failure strain of boron nitride honeycomb structures. Furthermore, due to the unique polarization of boron nitride honeycomb structures, they possessed an excellent piezoelectric effect. The piezoelectric coefficient e obtained from molecular dynamics was 0.702   C / m 2 , which was lower than that of the monolayer boron nitride honeycomb structures, e = 0.79   C / m 2 . Such excellent piezoelectric properties and failure strain detected in boron nitride honeycomb structures suggest a broad prospect for the application of these new materials in novel nanodevices with ultrahigh tensile mechanical properties and ultralight-weight materials.

scholarly journals Molecular Dynamics Study on Mechanical Properties of Nanopolycrystalline Cu–Sn Alloy

Materials ◽  
2021 ◽  
Vol 14 (24) ◽  
pp. 7782
Author(s):  
Guodong Zhang ◽  
Junsheng Zhao ◽  
Pengfei Wang ◽  
Xiaoyu Li ◽  
Yudong Liu ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Molecular Dynamics ◽  
Tensile Strength ◽  
Elastic Modulus ◽  
Dislocation Density ◽  
Strain Rate ◽  
Dynamics Simulation ◽  
Experimental Characterization ◽  
Tensile Process ◽  
Strength And Ductility

Molecular dynamics simulation is one kinds of important methods to research the nanocrystalline materials which is difficult to be studied through experimental characterization. In order to study the effects of Sn content and strain rate on the mechanical properties of nanopolycrystalline Cu–Sn alloy, the tensile simulation of nanopolycrystalline Cu–Sn alloy was carried out by molecular dynamics in the present study. The results demonstrate that the addition of Sn reduces the ductility of Cu–Sn alloy. However, the elastic modulus and tensile strength of Cu–Sn alloy are improved with increasing the Sn content initially, but they will be reduced when the Sn content exceeds 4% and 8%, respectively. Then, strain rate ranges from 1 × 109 s−1 to 5 × 109 s−1 were applied to the Cu–7Sn alloy, the results show that the strain rate influence elastic modulus of nanopolycrystalline Cu–7Sn alloy weakly, but the tensile strength and ductility enhance obviously with increasing the strain rate. Finally, the microstructure evolution of nanopolycrystalline Cu–Sn alloy during the whole tensile process was studied. It is found that the dislocation density in the Cu–Sn alloy reduces with increasing the Sn content. However, high strain rate leads to stacking faults more easily to generate and high dislocation density in the Cu–7Sn alloy.

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