Abstract:Evaluating the effect of porosity and ambient temperature on mechanical characteristics and thermal conductivity is vital for practical application and fundamental material property. Here we report that ambient temperature and porosity greatly influence fracture behavior and material properties. With the existence of the pore, the most significant stresses will be concentrated around the pore position during the uniaxial and biaxial processes, making fracture easier to occur than when tensing the perfect sheet… Show more
“…10 e. It is worthy to note that the thermal conductivity decrease with increasing temperature. This trend is consistent with our previous studies 58 , 59 that have been studied for other 2D materials. This can be explained as follows: based on the principle of thermal conductivity 60 , the thermal conductivity can be expressed by the following expression: Figure 10 ( a , b ) The relation between the thermal conductivity and the length of the monolayer MoS 2 membrane in the armchair and zigzag directions at various temperatures.…”
For practical application, determining the thermal and mechanical characterization of nanoporous two-dimensional MoS2 membranes is critical. To understand the influences of the temperature and porosity on the mechanical properties of single-layer MoS2 membrane, uniaxial and biaxial tensions were conducted using molecular dynamics simulations. It was found that Young’s modulus, ultimate strength, and fracture strain reduce with the temperature increases. At the same time, porosity effects were found to cause a decrease in the ultimate strength, fracture strain, and Young’s modulus of MoS2 membranes. Because the pore exists, the most considerable stresses will be concentrated around the pore site throughout uniaxial and biaxial tensile tests, increasing the possibility of fracture compared to tensing the pristine membrane. Moreover, this article investigates the impacts of temperature, porosity, and length size on the thermal conductivity of MoS2 membrane using the non-equilibrium molecular dynamics (NEMD) method. The results show that the thermal conductivity of the MoS2 membrane is strongly dependent on the temperature, porosity, and length size. Specifically, the thermal conductivity decreases as the temperature increases, and the thermal conductivity reduces as the porosity density increases. Interestingly, the thermal and mechanical properties of the pristine MoS2 membrane are similar in armchair and zigzag directions.
“…10 e. It is worthy to note that the thermal conductivity decrease with increasing temperature. This trend is consistent with our previous studies 58 , 59 that have been studied for other 2D materials. This can be explained as follows: based on the principle of thermal conductivity 60 , the thermal conductivity can be expressed by the following expression: Figure 10 ( a , b ) The relation between the thermal conductivity and the length of the monolayer MoS 2 membrane in the armchair and zigzag directions at various temperatures.…”
For practical application, determining the thermal and mechanical characterization of nanoporous two-dimensional MoS2 membranes is critical. To understand the influences of the temperature and porosity on the mechanical properties of single-layer MoS2 membrane, uniaxial and biaxial tensions were conducted using molecular dynamics simulations. It was found that Young’s modulus, ultimate strength, and fracture strain reduce with the temperature increases. At the same time, porosity effects were found to cause a decrease in the ultimate strength, fracture strain, and Young’s modulus of MoS2 membranes. Because the pore exists, the most considerable stresses will be concentrated around the pore site throughout uniaxial and biaxial tensile tests, increasing the possibility of fracture compared to tensing the pristine membrane. Moreover, this article investigates the impacts of temperature, porosity, and length size on the thermal conductivity of MoS2 membrane using the non-equilibrium molecular dynamics (NEMD) method. The results show that the thermal conductivity of the MoS2 membrane is strongly dependent on the temperature, porosity, and length size. Specifically, the thermal conductivity decreases as the temperature increases, and the thermal conductivity reduces as the porosity density increases. Interestingly, the thermal and mechanical properties of the pristine MoS2 membrane are similar in armchair and zigzag directions.
“…The corresponding reduced modulus values are 18.2, 16.5, 11.5, and 13.6 GPa for the same temperature range. These observations align with previous reports [52].…”
Section: Effect Of Substrate Temperaturesupporting
The mechanical properties and deformation behavior of CoCrNiAl medium entropy alloy (MEA) subjected to indentation by an indenter tooltip on the substrate are explored using molecular dynamics (MD) simulation. The study investigates the effects of alloy compositions, temperature variations, and ultra vibration (UV) on parameters, such as total force, shear strain, shear stress, hardness, reduced modulus, substrate temperature, phase transformation, dislocation length, and elastic recovery. The findings indicate that higher alloy compositions result in increased total force, hardness, and reduced modulus, with Ni-rich compositions demonstrating superior mechanical strength. Conversely, increasing alloy compositions lead to reduced von Mises stress (VMS), phase transformation, dislocation distribution, and dislocation length due to the larger atomic size of Ni compared to other primary elements. At elevated substrate temperatures, atoms exhibit larger vibration amplitudes and interatomic separations, leading to weaker atomic bonding and decreased contact force, rendering the substrate softer at higher temperatures. Additionally, higher initial substrate temperatures enhance atom kinetic energy and thermal vibrations, leading to reduced material hardness and increased VMS levels. Increasing vibration frequency enlarges the indentation area on the substrate's surface, concentrating shear strain and VMS with vibration frequency. Higher vibration amplitude and frequency amplify force, shear strain, VMS, substrate temperature, and dislocation distribution. Conversely, lower vibration amplitude and frequency result in a smaller average elastic recovery ratio. Moreover, increased amplitude and frequency values yield an amorphous-dominated indentation region and increased proportions of HCP and BCC structures. Furthermore, this study also takes into account the evaluation of a material's ability to recover elastically during the indentation process, which is a fundamental material property.
“…The interaction of atoms in samples is described by the embedded atoms method (EAM) potential, which was first proposed by Daw and Baskes in 1984 [26]. EAM potential is employed due to its advantage in metal and alloys' defect evolution and mechanical response [27][28][29][30]. Recently, the interaction between atoms in the CoCuFeNiPd HEA samples was given by Chen et al [12] and successfully applied in prior examinations through further testing [11,13].…”
The effects of sample structure and tool geometry are studied under cutting simulation to verify the deformation, removal mechanisms, and subsurface defection of lamellar twined CoCuFeNiPd alloys. These findings suggest that the twin boundary spacing and twin inclination angle (β) are the main determinants of surface wear characteristics and cutting-induced surface harm. The maximum cutting force achieved with TBS = 8a and β =900. The high friction coefficient with the sample has TBS = 8a and β = 900, showing that the tool's moving in the substrate is strongly restricted. Furthermore, the surface topography is not sensitive to the TBS and β. The best-machined surface is achieved with TBS = 3a and 4a under twin inclinations of 0 and 300. The effect of edge radius (R), rake angle (γ), and clearance angle (α) on the deformation behavior is examined. The negative of γ, small α, or larger R results in a higher cutting force, a worse subsurface, and a lower cutting pile-up height. With a positive γ, a large α or small R has a larger average friction coefficient, which implies a higher resistance rate. The tool with a smaller R or positive γ can improve the machined surface's smoothness.
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