scholarly journals Nanoindentation of γ-TiAl with Different Crystal Surfaces by Molecular Dynamics Simulations

Materials ◽  
2019 ◽  
Vol 12 (5) ◽  
pp. 770 ◽  
Author(s):  
Xiaocui Fan ◽  
Zhiyuan Rui ◽  
Hui Cao ◽  
Rong Fu ◽  
Ruicheng Feng ◽  
...  

The periodicity and density of atomic arrangement vary with the crystal orientation, which results in different deformation mechanisms and mechanical properties of γ-TiAl. In this paper, the anisotropic characteristics for γ-TiAl with (100), ( 1 ¯ 10 ) and (111) surfaces during nanoindentation at 300 K have been investigated by molecular dynamics simulations. It is found that there is no obvious pop-in event in all load-depth curves when the initial plastic deformation of γ-TiAl samples occurs, because the dislocation nucleates before the first load-drop; while a peak appears in both the unloading curves of the ( 1 ¯ 10 ) and (111) samples due to the release of energy. Stacking faults, twin boundaries and vacancies are formed in all samples; however, interstitials are formed in the (100) sample, a stacking fault tetrahedron is formed in the (111) sample; and two prismatic dislocation loops with different activities are formed in the ( 1 ¯ 10 ) and (111) samples, respectively. It is also concluded that the values of the critical load, strain energy, hardness and elastic modulus for the (111) sample are the maximum, and for the (100) sample are the minimum. Furthermore, the orientation dependence of the elastic modulus is greater than the hardness and critical load.

2012 ◽  
Vol 27 (2) ◽  
pp. 282-286 ◽  
Author(s):  
Jukka Ketoja ◽  
Sami Paavilainen ◽  
James Liam McWhirter ◽  
Tomasz Róg ◽  
Juha Järvinen ◽  
...  

Abstract We have carried out atomistic molecular dynamics simulations to study the mechanical properties of cellulose nanofibrils in water and ethanol. The studied elementary fibrils consisted of regions having 34 or 36 cellulose chains whose cross-sectional diameter across the fibril was roughly 3.4 nm. The models used in simulations included both crystalline and non-crystalline regions, where the latter were designed to describe the essentials parts of amorphous cellulose nanofibrils. We examined different numbers of connecting chains between the crystallites, and found out that the elastic constants, inelastic deformations, and strength of the fibril depend on this number. For example, the elastic modulus for the whole fibril can be estimated to increase by 4 GPa for each additional connecting chain.


2000 ◽  
Vol 84 (23) ◽  
pp. 5351-5354 ◽  
Author(s):  
Timothy C. Germann ◽  
Brad Lee Holian ◽  
Peter S. Lomdahl ◽  
Ramon Ravelo

2011 ◽  
Vol 465 ◽  
pp. 89-92 ◽  
Author(s):  
J. Guénolé ◽  
Julien Godet ◽  
Sandrine Brochard

We have performed molecular dynamics simulations on silicon nanowires (Si-NW) with [001] axis and square section. The forces are modeled by well-tested semi-empirical potentials. First we investigated the edge reconstruction of Si nanowires. Then, we studied the behavior of the NW when submitted to compression stresses along its axis. At low temperature (300K), we observed the formation of dislocation loops with a Burgers vector 1/2 [10-1]. These dislocations slip in the unexpected {101} planes having the largest Schmid factor.


2010 ◽  
Vol 152-153 ◽  
pp. 1180-1183
Author(s):  
Yun Jun Chen ◽  
Yi Sun ◽  
Zhi Wei Cui

In this paper, we investigate the mechanical properties of ceria and gadolinia doped ceria by molecular dynamics simulations. The doped concentrations and temperature dependence of yield stress and elastic modulus have been evaluated via uniaxial compression. Simulation results reveal that such properties decrease dramatically with higher temperature and doped content. In addition, the attenuated effect of doped content is more significant than that of temperature.


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