Publication Date: 2024
Archives of Computational Methods in Engineering (1134-3060)31(4)pp. 2417-2429
The main features of superalloys are included good stability and strength at high temperatures (excellent mechanical strength), creep resistance at high temperatures, resistance to corrosion and oxidation at high operating temperatures, and resistance to thermal deformation at high operating temperatures. Superalloys have different properties, meaning that each alloy has its unique chemical and mechanical properties, so it is necessary to find the physical, mechanical, and chemical properties of superalloys. There are several ways to do this: The experimental method, computational and analytical method, and molecular dynamics simulation method. In this research, Mechanical properties of superalloys have been studied using molecular dynamics simulation. Tensile-pressure behavior of the superalloys, dislocations, hardness behavior, elastic-plastic behavior, crack growth, fatigue properties, and creep behavior have been considered. Eventually, some challenges and future work will be discussed. © The Author(s) under exclusive licence to International Center for Numerical Methods in Engineering (CIMNE) 2023.
Publication Date: 2023
Materials Today Communications (23524928)37
Al-Mg alloy is widely used in various industries due to its practicality. It is crucial to achieve the highest possible tensile properties for this alloy. In this study, first, Zn nanoparticles were combined with the aluminum-magnesium alloy to modify their tensile properties. Then, a mixture design of experiment was utilized to find the best combination of Al-Mg-Zn alloy, which was validated through molecular dynamics simulation. Mechanical tests were also conducted on Al-1%Mg-1%Zn alloy at different temperatures and strain rates. The results suggested that when the temperature increases, the tensile properties decrease, while with higher strain rates they increase. Furthermore, four machine learning-based algorithms including Generalized Linear Model (GLM), Artificial Neural Network (ANN), Decision Tree (DT), and Random Forest (RF) were compared to determine the simplest and the most accurate one for the prediction of mechanical properties of Al-Mg-Zn alloy and due to the highest values of correlation coefficient, the ANN algorithm was found as the most accurate one for the prediction of mechanical properties. The GLM algorithm was also known as an appropriate algorithm to predict the mechanical properties. However, the DT and RF algorithms had low prediction precisions. Therefore, the parameters that were influential in the prediction precision of DT and RF algorithms were changed, and the best value of each parameter was obtained. It was found that the DT algorithm with a maximum depth of 6 has the highest precision prediction of mechanical properties. Furthermore, the RF algorithm had the highest accuracy for the prediction of mechanical properties with No. of trees = 4 and maximum depth = 4. © 2023
Publication Date: 2023
Computational Particle Mechanics (21964386)10(1)pp. 143-153
Nowadays, various methods are being formed on new composites and nanocomposite compounds. Investigating the properties of nanocomposites and finding their optimal properties pave the way for a better use of them. In this study, first, mechanical molecular dynamics method is used to investigate mechanical properties of aluminum/carbon nanotubes (Al-CNT) nanocomposite, then, the effect of temperature change, strain rate, and chirality of nanotubes on the elastic modulus and ultimate stress of nanocomposite have been investigated. However, in order to simultaneously investigate these three parameters on the properties of nanocomposite and to find an optimal point for the elastic modulus and ultimate stress, the experimental design method for optimization was used. Derringer method was used to determine optimal parameters for simultaneous optimization of two response variables, namely elastic modulus and ultimate stress. It can be concluded that the optimal conditions occur simultaneously at 50 K, strain rate 0.01, and chirality (5,5), in which the value of the elastic modulus is 156 GPa and the ultimate strain value is 13.7 GPa and simultaneous minimum value of elastic modulus and ultimate stress occur at 650 K, strain rate 0.0205, chirality (3,3), in which the value of elastic module is 94 GPa and the ultimate strain value is 6.44 GPa. © 2022, The Author(s) under exclusive licence to OWZ.
Publication Date: 2022
Silicon (18769918)14(10)pp. 5527-5534
The mechanical properties of nanostructures are a researcher’s favorite topics. In the meantime, the mechanical and physical properties of the two dimensional structures and the nanotubes have attracted greater attention due to their wide application. Si (Si) nanotubes are structures consisting of Si atoms that are arranged as honeycombs. This structure has created some special properties in Si nanotubes. In this paper, Young’s modulus values and stress strain diagrams of Si nanotubes are investigated using molecular dynamics method and the Tersoff potential. Then, the changes effect of size and dimension was investigated for a closer look. For this purpose, the effect of nanotube diameter, length, and chirality shift from zigzag to armchair were studied. The results showed that the fracture stress of nanotube decreased with increasing the length of Si nanotube. It was also shown that the armchair structure was stronger than the zigzag. The effect of diameter change on the mechanical properties was also investigated and it was observed that no specific order could be found between the diameter changes with the Si nanotube strength. The results were in good agreement with other studies. © 2021, Springer Nature B.V.
Publication Date: 2022
Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science (20412983)236(23)pp. 11322-11329
Molecular dynamics simulation is among the most significant methods in nanoscale studies. This paper studied the effect of strain rate, temperature, and nanotube chirality on the stress-strain behavior of aluminum/silicon nanotubes (SiNTs) using molecular dynamics simulation. Ultimate tensile stress and Young’s modulus of the nanocomposite were evaluated using molecular dynamics simulation. According to the results, Young’s modulus of the nanocomposite decreased with increasing temperature. Also, Young’s modulus decreased by increasing the strain rate. Next, an experimental approach was used based on the Box–Behnken design. According to the input parameters and the experimental approach, the number of simulations in the software was 39 runs. Overall, it is concluded that the optimal conditions were created at a temperature of 50 K, a strain rate of 0.01/ps, and chirality of (5,5), leading to the elasticity modulus of 137 GPa and the ultimate tensile stress of 11.8 GPa. © IMechE 2022.
Publication Date: 2021
International Communications in Heat and Mass Transfer (07351933)129
One of the most important properties of nanomaterials is their thermal conductivity, which is particularly needed by researchers in electronic equipment. In this research, the thermal conductivity properties of carbon nanotubes were first investigated. Next, the thermal conductivity of silicon nanotubes was investigated using the molecular dynamics method. For this purpose, five important effects were investigated: the effect of changing the potential function, the effect of changing the length of the heat bath region, the effect of changing the length, the effect of changing diameter, and the effect of changing the temperature of the nanotube. The results indicated that by changing the potential function, the thermal conductivity was decreased. Additionally, the result demonstrated that by increasing the length of the heat bath region, the thermal conductivity of silicon nanotubes was decreased, while in carbon nanotubes, the thermal conductivity was increased. Also, in both carbon nanotubes and silicon nanotubes, increasing temperature between 100 K and 300 K decreased kappa coefficient. On the other hand, increasing diameters, increased the kappa coefficient. Finally, as the length of the nanotubes was increased, no significant change was observed in the kappa coefficient of silicon nanotubes, while in carbon nanotubes, the kappa coefficient was increased. © 2021 Elsevier Ltd
Publication Date: 2020
Proceedings of the Institution of Mechanical Engineers, Part N: Journal of Nanomaterials, Nanoengineering and Nanosystems (23977922)234(1-2)pp. 3-10
The two-dimensional nanostructures such as graphene, silicene, germanene, and stanene have attracted a lot of attention in recent years. Many studies have been done on graphene, but other two-dimensional structures have not yet been studied extensively. In this work, a molecular dynamics simulation of silicene was done and stress–strain curve of silicene was obtained. Then, the mechanical properties of silicene were investigated using the proposed structural molecular mechanics method. First, using the relations governing the force field and the Lifson–Wershel potential function and structural mechanics relations, the coefficients for the BEAM elements was determined, and a structural mechanics model for silicene was proposed. Then, a silicene sheet with 65 Å × 65 Å was modeled, and Young’s modulus of silicene was obtained. In addition, the natural frequencies and mode shapes of silicene were calculated using finite element method. The results are in good agreement with reports by other papers. © IMechE 2020.
Publication Date: 2020
Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science (20412983)234(2)pp. 635-642
Composite materials have become popular because of high mechanical properties and lightweight. Aluminum/carbon nanotube is one of the most important metal composite. In this research, mechanical properties of aluminum/carbon nanotube composite were obtained using molecular dynamics simulation. Then, effect of temperature on stress–strain curve of composite was studied. The results showed by increasing temperature, the Young’s modulus of composite was decreased. More specifically increasing the temperature from 150 K to 620 K, decrease the Young’s modulus to 11.7%. The ultimate stress of composite also decreased by increasing the temperature. A continuum model of composite was presented using finite element method. The results showed the role of carbon nanotube on strengthening of composite. © IMechE 2019.
Publication Date: 2020
International Journal of Geometric Methods in Modern Physics (17936977)17(2)
Numerous experiments on graphene, which is a 2D carbon material with excellent mechanical and electrical properties, have been carried out in recent years. By recognizing the properties of graphene, the researchers focused on other two-dimensional materials. Several studies have been done on graphene, but other two-dimensional structures have not yet been studied extensively. In this work, Germanene's simulation of molecular dynamics was performed and Germanene's stress-strain curve was obtained. The mechanical properties of Germanene have been investigated by practicing the proposed method of structural molecular mechanics. The two-step procedure was followed, where, in first step with the aid of the relations governing the force field and the Lifson-Wershel potential function and structural mechanics relations, the coefficients for the BEAM elements were found, and a structural mechanics model for Germanene was proposed. Then, a germanene sheet with 60 × 70 ? was modeled and Young's modulus of Germanene was obtained by molecular dynamics and proposed molecular mechanics methods. © 2020 World Scientific Publishing Company.
Publication Date: 2020
Journal of Nondestructive Evaluation (15734862)39(1)
Bearings are one of the most widely used components in the industry that are more vulnerable than other parts of machines. In this research, a precise method was developed for diagnosis bearing detection based on vibrating signals. Vibration signals were recorded from four common faults in the bearings at three speeds of 1800, 3900, and 6600 rpm. The vibration signals were transmitted by the fast Fourier transform to the frequency domain. A total of 24 features were extracted from frequency and time signals. The superior features are selected using the combination of genetic algorithm and artificial neural network. A support vector machine is used to intelligently detect ball bearing faults. The accuracy of the support vector machine with all extracted features in different revolutions showed that the highest accuracy for training and test data was obtained 78.86% and 69.33% respectively, at 1800 rpm. The results of reduction and selection of superior features showed that the highest accuracy of the support machine was obtained in the classification of ball bearing faults for training and test data 97.14% and 93.33%, respectively. The results show that the use of the feature selection method based on the genetic algorithm will increase the accuracy of the classification. © 2020, Springer Science+Business Media, LLC, part of Springer Nature.
Publication Date: 2019
International Journal of Geometric Methods in Modern Physics (17936977)16(6)
Microtubules (MTs), the intracellular structures, are made-up of polar polymers that are composed of α and β tubulins. The functions of MTs are shape the way for vesicles movement and asexual mitosis division. However, one of the main functions of MTs is stability of cells. Fewer geometrical methods are available in the literature to explore the molecular dynamics (MDs) of a MT, which is a difficult task due to its microscopic size and complex structure. A structural mechanics model with rather similar properties to MT can demonstrate the dynamics of MT. The first and most important step for this process is to obtain the interaction force between tubulins, and a mechanical model can be used to simulate the mechanical and dynamical properties of MTs by using meso-and macro-scale simulations. This work reports the interaction properties of β-α tubulin in MT. During this research, with the aid of the MD simulations, the interaction energy in β-α dimer is evaluated. The alpha-beta force-distance diagram is sketched with the aid of force and energy formulae. Thus, the graphical analysis supported the findings of this study. © 2019 World Scientific Publishing Company.
Publication Date: 2019
Scientia Iranica (23453605)26(3F)pp. 1973-1979
Graphene is a thin sheet with special properties and complicated mechanical behavior. It is important to study graphene experimentally and theoretically. Stone-Wales defects, cracks, and atom vacancy are popular defects in carbon allotropes, especially in graphene. In this paper, residual strain in graphene was discussed. At first, stress-strain curve of non-defected graphene sheet was obtained using molecular dynamics simulation, and effect of temperature on mechanical properties of graphene was obtained. Then, four different cracks at the center of graphene sheets were considered. Stress-strain curves of defected graphene sheets with different tension strain rates were plotted. The results showed that cracks would lead the graphene to fracture sooner. In addition, increasing temperature leads to a decrease in the Young's modulus of graphene and graphene fracture at lower strain. On the other hand, residual strain of non-defected and cracked graphene increased by increasing temperature from 200 K to 1200 K. It means that graphene is subject to more plasticity behavior in case of temperature increase. © 2019 Sharif University of Technology. All rights reserved.
Publication Date: 2018
Materials Physics and Mechanics (16052730)40(2)pp. 304-312
Microtubules are filamentous intracellular structures that are responsible for various kinds of movements in all eukaryotic cells. The dynamic assembly and disassembly of microtubules and the mechanical properties of these polymers are essential for many key cellular processes such as spermatogenesis and the processes of neurons. Mathematical and computational modeling, especially coupled mechanochemical modeling, has contributed a lot to understand their dynamics. However, it has remained a great challenge to reduce the critical discrepancies, which exist between the experimental observations and modeling results. During this research, the small scaling parameter of the nonlocal Euler-Bernoulli beam theory is analyzed to demonstrate the free vibration problem of microtubules. © 2018, Institute of Problems of Mechanical Engineering RAS.
Publication Date: 2018
Journal of Nano Research (16619897)55pp. 22-31
Graphene is a thin sheet with special properties and complicated mechanical behavior. It's important to study graphene experimentally and theoretically. Stone-Wales defects, cracks and atom vacancy are popular defects in carbon allotropes especially in graphene. In this paper, effect of center cracks on graphene was discussed. At first, mechanical properties of non-defected graphene sheet was obtained using molecular dynamics simulation. Comparing result with theoretical and experimental studies showing good agreements and proofing the results. Then, 8 different cracks were considered in center of graphene sheets. Stress-strain curves of defected graphene sheets with different tension strain rates were plotted. The results showed that increasing crack length lead to decreasing Young's modulus of graphene from 905GPa to 697GPa. Also, fracture occurred in less tensile strain. In the following, structural molecular mechanics method was used to simulate cracked graphene sheets. The results showed good agreement between two methods. © 2018 Trans Tech Publications, Switzerland.
Publication Date: 2018
Advances in Mechanical Engineering (16878132)10(12)
In this study, an investigation of “the free vibrations of hollow circular plates’’ is reported. The study is based on elastic foundation and the results depicted are further extended to study the special case of “graphene sheets.’’ The first-order shear deformation theory is applied to study the elastic properties of the material. A hollow circular sheet is modeled and the vibrations are simulated with the aid of finite element method. The results obtained are in good agreement with the theoretical findings. After the validation, a model of graphene is presented. Graphene contains a layer of honeycomb carbon atoms. Inside a layer, each carbon atom C is attached to three other carbon atoms and produces a sheet of hexagonal array. A 25 nm × 25 nm graphene sheet is modeled and simulated using the validated technique, that is, via the first-order shear deformation theory. The key findings of this study are the vibrational frequencies and vibrational mode shapes. © The Author(s) 2018.
Publication Date: 2016
Journal of Solid Mechanics (discontinued) (20087683)8(4)pp. 781-787
This work is conducted to obtain mechanical properties of microtubule. For this aim, interaction energy in alpha-beta, beta-alpha, alpha-alpha, and beta-beta dimers was calculated using the molecular dynamic simulation. Force-distance diagrams for these dimers were obtained using the relation between potential energy and force. Afterwards, instead of each tubulin, one sphere with 55 KDa weight connecting to another tubulin with a nonlinear connection such as nonlinear spring could be considered. The mechanical model of microtubule was used to calculate Young's modulus based on finite element method. Obtained Young's modulus has good agreement with previous works. Also, natural frequency of microtubules was calculated based on finite element method. © 2016 IAU, Arak Branch. All rights reserved.
Publication Date: 2013
Journal of Computational and Theoretical Nanoscience (15461955)10(4)pp. 1033-1037
Two carbon nanotubes with different diameters can form a carbon nanotube junction, which can be applied to build some electromechanical devices such as semiconductors, nano-nuzzles, and nano-diffusers. In this research, two zigzag carbon nanotubes with chiral vector (5, 0) and (10, 0) were considered and their mechanical properties were obtained from the molecular mechanic approach. Then, Special algorithm was used to connect latter CNTs. To model this junction molecular mechanic approach was applied. In the next step, mechanical properties and natural frequencies of the connected carbon nanotubes were measured. In this research, it was found that there is a remarkable increase in Young modulus of carbon nanotube junction. Furthermore, natural frequencies of connected carbon nanotubes, plus primary carbon nanotubes were compared together. Moreover, considering the same boundary conditions with primary carbon nanotubes, it was revealed that connected carbon nanotubes have different vibration behaviors. Copyright © 2013 American Scientific Publishers All rights reserved.
Publication Date: 2012
Materials and Design (0264-1275)34pp. 603-608
Elastomers, particularly rubbers, are viscoelastic polymers with low Young's modulus. In this research, carbon nanotubes were used in the rubber and a rubber-carbon nanotube composite was modeled by ABAQUS™ software. Due to hyperelastic behavior of the rubber, strain function energy was used for the modeling. A sample of rubber was tested and uniaxial, biaxial, as well as planar test data obtained in these tests were used to get an energy function. Polynomial and reduced polynomial form are two common methods to achieve strain energy function. In this paper, elasticity modulus and Poisson ratio were measured for a representative volume element (RVE) of composite. Rubber was also considered as an elastic material and its composite properties in this state compared by hyperelastic rubber matrix assumption. ABAQUS was used to create a three dimensional finite element model of a single long wavy nanotube with diameter of D which perfectly bonded to matrix material. Nanotube waviness was modeled by sinusoidal carbon nanotube shape. Results showed that mechanical properties of the rubber will extremely change by adding carbon nanotube. Furthermore, several volume fractions of carbon nanotube in rubber were modeled and it was shown that stiffness of nanocomposite increases by more volume fraction of carbon nanotubes. © 2011 Elsevier Ltd.
Publication Date: 2012
Micro and Nano Letters (17500443)7(4)pp. 380-383
Corrosion resistance of nanocrystalline 316L stainless steel was compared with a coarse-grained (CG) one using potentiodynamic polarisation and electrochemical impedance spectroscopy methods and electron microscopy. The results showed that the corrosion resistance of nanocrystalline 316L stainless steel was higher than CG stainless steel. It was attributed to unstable passive layer on CG 316L stainless steel, which could be removed in a corrosive medium. The lower grain size facilitated fast diffusion of Cr and formation of passive layer. Nanocrystalline 316L stainless steel showed a relatively stable current density in anodic potentials, which was related to the higher corrosion resistance of nanocrystalline 316L stainless steel. © 2012 The Institution of Engineering and Technology.
Publication Date: 2011
Micro and Nano Letters (17500443)6(6)pp. 402-404
Nanostructured thin film copper fabricated by electron beam-physical vapour deposition (EB-PVD) method has unique properties, which make it different from the other deposits. In this study, nanostructured copper deposits were produced by EB-PVD as well as pulse plating techniques. Transmission electron microscopy was used for investigating the morphology of the deposited film. Surface roughness of deposits was measured by DEKTAK profilometer. Furthermore, electrochemical impedance spectroscopy (EIS) and potentiodynamic polarisation methods were used to study the corrosive behaviour of the films. The surface morphology of corroded samples was obtained by scanning electron microscopy (SEM). Data obtained by polarisation, EIS and SEM suggested that corrosion resistance of EB-PVD deposit was higher than pulse plating deposit. This might be caused by its lower surface roughness and high purity owing to deposition in high vacuum. © 2011 The Institution of Engineering and Technology.
Elastomers, in particular rubbers, are used in a wide variety of products ranging from rubber hoses, isolation bearings, and shock absorbers to tires. Rubber has good properties and is thermal and electrical resistant. We used carbon nanotube in rubber and modeled this composite with ABAQUS software. Because of hyperelastic behavior of rubber we had to use a strain energy function for nanocomposites modeling. We tested a sample of rubber and gained uniaxial, biaxial and planar test data and then used this data to get a good strain energy function. Mooney-Rivlin form, Neo-Hookean form, Ogden form, Polynomial form, reduced polynomial form, Van der Waals form and etc, are some methods to get strain function energy. Modulus of elasticity and Poisson ratio and some other mechanical properties gained for a representative volume element (RVE) of composite in this work. We also considered rubber as an elastic material and gained mechanical properties of composite and then compared result for elastic and hyperelastic rubber matrix together.
Publication Date: 2010
Journal of Solid Mechanics (discontinued) (20087683)2(1)pp. 43-49
An elastomer is a polymer with the property of viscoelasticity, generally having notably low Young's modulus and high yield strain compared with other materials. Elastomers, in particular rubbers, are used in a wide variety of products ranging from rubber hoses, isolation bearings, and shock absorbers to tires. Rubber has good properties and is thermal and electrical resistant. We used carbon nanotube in rubber and modeled this composite with ABAQUS software. Because of hyperelastic behavior of rubber we had to use a strain energy function for nanocomposites modeling. A sample of rubber was tested and gained uniaxial, biaxial and planar test data and then the data used to get a good strain energy function. Mooney-Rivlin form, Neo-Hookean form, Ogden form, Polynomial form, reduced polynomial form, Van der Waals form etc, are some methods to get strain function energy. Modulus of elasticity and Poisson ratio and some other mechanical properties gained for a representative volume element (RVE) of composite in this work. We also considered rubber as an elastic material and gained mechanical properties of composite and then compared result for elastic and hyperelastic rubber matrix together. © 2010 IAU, Arak Branch.
