Sawaran singh, N.S.,
Ali, A.B.,
Abed hussein, M.,
Mohammed, J.K.,
Kharraji, O.,
Pirmoradian, M.,
Hashemian, M.,
Salahshour, S. Case Studies in Chemical and Environmental Engineering (26660164)11
This study aims to explore the dynamic instability of micro and nano-sized Timoshenko beams as they are traversed by sequentially moving nanoparticles. The beams, characterized by a rectangular cross-section and homogeneity, are situated within a Pasternak foundation, which provides a supportive elastic medium. The research investigation determines nanoparticle inertia effects at velocity while establishing motion equations through Hamilton's principle. The model unites nonlinear von Kàrmàn strain-displacement kinematics with strain gradient theory and Gurtin-Murdoch small-scale accounting. The system's behavior gets analyzed through the implementation of Galerkin method which derives time-periodic motion equations. The incremental harmonic balance approach develops stability boundary maps that separate stable and unstable regions through which analysts can examine parameter spaces containing moving particle mass and velocity values. This study evaluates how different parameters like beam diameters together with small-scale characteristics and elastic medium constants and residual stress and axial compressive forces affect the stability diagram. The analysis demonstrates that stability parameters become substantially modified when researchers include length scale characteristics along with surface effects. The outcome reveals that axial compressive forces reduce stability yet environmental effects strengthen the stability of small-scale beams which leads to transition curve movements towards faster moving particles velocities. This study contributes fundamental knowledge about dynamic instability effects in small-scale beams which will help future advances in nanotechnology and materials science. © 2025 The Authors
Ali, A.B.,
Hussein, R.A.,
Sawaran singh, N.S.,
Salahshour, S.,
Pirmoradian, M.,
Mohammad sajadi s., S.M.,
Deriszadeh, A. International Journal of Thermofluids (26662027)26
This work examines the impact of different pressure levels (1 to 5 bar) and magnetic field frequencies (0.01 to 0.05 ps⁻¹) on the thermal behavior of sodium sulfate/magnesium chloride hexahydrate as a phase change material inside iron nanochannels, using molecular dynamics simulation. The system's kinetic and potential energies converge to 39.79 eV and -7204.99 eV, indicating the stability of the nanostructures. The impact of pressure and magnetic field frequency on heat flow, maximum temperature, and charge/discharge times was examined. Increasing the pressure from 1 to 5 bar reduced the heat flux and maximum temperature to 1509 W/m² and 391.18 K, respectively. Simultaneously, the charge duration extendes to 3.99 ns, whilst the discharge duration decreases to 4.30 ns. Moreover, increasing the magnetic field frequency from 0.01 to 0.05 ps⁻¹ results in a decrease in maximum temperature and heat flux, which fell to 415.67 K and 1566 W/m², respectively. The charge time decreases to 3.87 ns and the discharge time to 4.50 ns little owing to the increase in frequency. © 2025 The Author(s)
Sawaran singh, N.S.,
Hassan, W.H.,
Ameen ahmed, Z.M.,
Al-zahy, Y.M.A.,
Salahshour, S.,
Pirmoradian, M. Case Studies in Chemical and Environmental Engineering (26660164)11
This study presents an investigation into the vibration resonance of Mindlin piezoelectric polymeric nanoplates under electromechanical loading, particularly in the presence of a rotating nanoparticle. The novelty of this research lies in the application of non-local piezoelasticity, which effectively incorporates the influence of small-scale factors on the resonance behavior of the nanoplate. By employing a variational approach to derive the governing equations, this work advances the understanding of how various parameters such as the non-local parameter, dimensions of the nanoplate, excitation voltage, and mass of the nanoparticle affect resonance frequencies. The Galerkin method is utilized to solve the partial differential equations governing the dynamics of the piezoelectric polymeric nanoplate, marking a significant methodological contribution to the field. The incremental harmonic balance approach is then applied to estimate the system's resonance frequencies, with numerical simulations confirming their existence. This research not only elucidates the complex interactions affecting resonance behavior but also highlights the potential for optimizing the design of nanostructures in various applications, including sensors and energy-harvesting devices. The findings suggest that increasing the non-local parameter softens the nanoplate's rigidity, leading to decreased resonance frequencies, while modifications in dimensions and applied voltages can enhance these frequencies. Overall, this study lays the groundwork for future explorations into the dynamic behavior of piezoelectric materials, emphasizing the importance of small-scale effects in nanotechnology applications. © 2025 The Authors
Abdolvand, R.,
Yoosefzadeh, S.,
Jaffar, H.A.,
Abdul-redha, H.K.,
Akbari, O.A.,
Ahmadi, G.,
Salahshour, S.,
Pirmoradian, M. International Journal of Thermofluids (26662027)26
Improving the thermal performance of equipment on large and small scales is one of the most important issues in engineering. In this numerical study, the flow and combined convection heat transfer in a two-dimensional (2D) sinusoidal cavity affected by the movement of indirect hot fluid flow are investigated using the finite volume method. By using water/silver nanofluid in volume fractions (φ) of 0 to 0.06 and using fractal surfaces in a 2D cavity with a lid-driven cap in Richardson numbers (Ri) 0 to10, an attempt is made to increase the heat transfer efficiency of the sinusoidal hot surface. The results of this research show that due to the increase in the convective heat transfer coefficient resulted from the strengthening of the fluid velocity, a significant decrease in the temperature of the hot surface is achieved. At Ri = 10, due to the slower movement of the cap and the full compliance of the fluid with the sinusoidal surface, the heat penetration in the fluid layers increases and the temperature graphs become more uniform. The flow circulation between the two hot and cold sources is affected by the density gradients in the cooling fluid and the movement of the cap can create a different temperature distribution. The fluid temperature distribution is also dependent on moving areas in the cavity. The placement of fluid on fractal surfaces is associated with extreme velocity changes. Due to the presence of viscosity and the formation of the velocity boundary layer, this behavior also affects the movement of the fluid layers to the solid surface areas. The highest value of the Nusselt number (Nu) is gained during fluid contact with a cold lid-driven cap on the left side of the cavity. As the fluid moves further on the surfaces of the moving cavity, the hot fluid gradually exchanges its energy with the cavity cover and the fluid cools down. The presence of solid nanoparticles in a higher φ has a significant effect on reducing the temperature of the hot surface, which is due to the increase in the thermal conductivity of the cooling fluid. Compared to the base fluid, this behavior at φ = 0.06 has created a higher thermal efficiency increase of about 15 %. The lowest shear stress is related to the areas of fluid separation on the curved surface. In all investigated cases, the increase of φ can increase the average shear stress between 35 % and 43 % in different Ri. © 2024
Huaguang li, ,
Ali, A.B.,
Hussein, R.A.,
Sawaran singh, N.S.,
Abdullaeva, B.,
Ahmad, Z.,
Salahshour, S.,
Baghoolizadeh, M.,
Pirmoradian, M. Case Studies in Thermal Engineering (2214157X)69
Background: Because of their enhanced thermophysical characteristics, namely greater thermal conductivity, viscosity control, and long-term stability than traditional nanofluids, hybrid nanofluids drew interest. Such properties make them suitable candidates for many industrial applications such as solar systems and thermal management. However, knowing the thermophysical properties of these materials accurately is difficult because of the complexities of nanoparticles and the interaction with the base fluid. This paper utilizes machine learning methods to predict the thermophysical properties of water/ethylene glycol mixture-based hybrid nanofluids containing reduced silver-graphene oxide.Method: ology: This study aimed to predict Viscosity (DV), Thermal Conductivity (TC) and Density (D) by three machine learning algorithms including multiple linear regression (MLR), Multiple Polynomial Regression (MPR) and Gaussian Process Regression (GPR). A 5 × 28 dataset was used for training and testing the network, with 80 % of the data used for training the network and 20 % for testing the network. Evaluating the performance of algorithms is based on the evaluation indices of Correlation coefficient (R), Root Mean Square Error (RMSE), Mean Absolute Error (MAE) and Standard Deviation (STD). In addition, optimization is done by the Non- dominated Sorting Genetic Algorithm-II (NSGA-II) algorithm and the impact results of different mutation and combination rates are examined. Results: The MPR algorithm yielded the lowest MoD values (0.07 % and − 0.06 %) and the highest prediction accuracy among the models tested (R = 0.9999, RMSD = 2.726 × 10− 4, STD = 0.0219). Furthermore, NSGA-II optimization results revealed that the temperature and concentration of nanoparticles could effectively increase the thermal conductivity, while too high concentration could also increase viscosity. Finally, through the TOPSIS method, the best point was chosen giving a blend of ideal thermophysical properties. This signifies that machine learning methods can be successfully employed for the prediction and optimization of hybrid nanofluid characteristics. © 2025 The Authors.
Graish, M.S.,
Ali, A.B.,
Al-zahiwat, M.M.,
Alardhi, S.M.,
Baghoolizadeh, M.,
Salahshour, S.,
Pirmoradian, M. Case Studies in Chemical and Environmental Engineering (26660164)11
Viscosity is a crucial parameter for heat transfer systems, governing pumping power, Rayleigh number, and Reynolds number; thus, viscosity prediction for hybrid nanofluids is important. Although some studies have employed ML algorithms for predicting viscosity, limited ML algorithms or specific nanofluid types were examined in previous studies, disregarding the complexities involved in the rheological behavior of a complex nanofluid system such as non-Newtonian hybrid nanofluids. To overcome this limitation, this study offers a practical contribution by utilizing 20 different machine-learning models to predict the viscosity of iron-CuO/water-ethylene glycol non-Newtonian hybrid nanofluids. The influences of the input variables: solid volume fraction (SVF), temperature, and shear rate on viscosity prediction are systematically assessed. We evaluate the prediction accuracy and reliability of algorithms using ten performance metrics including RMSE, MAE, R2 and NSE. Multivariate Polynomial Regression (MPR) outperforms the other algorithms, which is evident in the highest correlation coefficient (R2 = 0.992) and lowest error metrics. At the other end, is the Extreme Learning Machine (ELM), which turns out to be the worst performer. A unique contribution of this paper is that we extract a mathematical equation from the MPR model that allows for straightforward calculation of viscosity, avoiding non-trivial ML computations. This simplicity aids in practical applications and increases usefulness for engineers and researchers alike. Using advanced data visualization techniques (heatmaps, box plots, KDE plots and Taylor diagrams), the relationships between input variables and viscosity as well as the model performance are explored. These results give a better understanding of the non-Newtonian hybrid nanofluid behavior and a solid predictor of design-efficient heat transfer systems. © 2025 The Authors
Motallebi, M.A.,
Hashemian, M.,
Eftekhari, S.A.,
Toghraie, D.,
Pirmoradian, M. Propulsion and Power Research (2212540X)14(1)pp. 110-132
In the presented paper, the size-dependent flutter analysis of a nanobeam made of metal-ceramic functionally graded (FG) materials subjected to supersonic fluid flow is examined. The volume fractions of metal and ceramic vary along both longitudinal and thickness directions. The size effects are modeled based on the nonlocal strain gradient theory (NSGT) and the surface effects are included according to the Gurtin-Murdoch surface elasticity theory. The mathematical modeling of nanobeam is performed in the framework of Reddy's third-order shear deformation beam theory (TSDBT), and the aerodynamic pressure is modeled according to the linear approximation of the piston theory. The governing equations and boundary conditions are obtained utilizing Hamilton's principle and are solved approximately via the differential quadrature method (DQM). Convergence and precision of the presented work are proved and the effects of several parameters on the flutter boundaries are inspected such as material gradation indexes, nonlocal and strain gradient parameters, thickness-to-length ratio, and incorporation of surface effects. It is discovered that the incorporation of the surface effects has a remarkable impact on the flutter boundaries of nanobeams and increases both critical aerodynamic pressure and flutter frequency of the nanobeam. The aim of this work is to examine how the aeroelastic stability characteristics of an FG nanobeam can be affected by the nonlocal and strain gradient parameters and the variations in the volume fractions of the metal and ceramic in the longitudinal and thickness directions. © 2025 The Authors
Omar, I.,
Marhoon, T.,
Babadoust, S.,
Najm, A.S.,
Pirmoradian, M.,
Salahshour, S.,
Mohammad sajadi s., S.M. Results in Engineering (25901230)25
This work examines the buckling behavior of functionally graded porous nanoplates embedded in elastic media. Size effects are added to the nanoplate constitutive equations using nonlocal strain gradient theory. The four-variable refined plate theory is employed for nanoplate modeling. This theory assures stress-free conditions on both sides of the nanoplate and has less uncertainty than high-order shear deformation theories. It is postulated that the nanoplate experiences in-plane compressive loads, which may have both linear and nonlinear distributions. Additionally, uniform and non-uniform porosity distributions are considered. The governing partial differential equations are extracted using the notion of the minimal total potential energy. Following this, the Galerkin method is employed to solve these equations utilizing trigonometric shape functions. Simple, clamped, and combined boundary conditions for nanoplate edges are studied. Once the governing algebraic equations were extracted, the critical buckling load of the nanoplate is determined. To conduct a validation study, the obtained data are juxtaposed with the findings of previous studies, revealing a notable level of concurrence. After the critical buckling load has been ascertained, an inquiry is undertaken to assess the influence of various parameters including nonlocal and length scale parameters, boundary conditions, porosity distribution type, in-plane loading type, geometric dimensions of the nanoplate, and stiffness of the elastic environment, on the static stability of nanoplates. © 2024
Gao, X.,
Abbas, W.N.,
Al-zahy, Y.M.A.,
Al-bahrani, M.,
Kumar, N.,
Hanoon, Z.A.,
Salahshour, S.,
Pirmoradian, M. Physica A: Statistical Mechanics and its Applications (03784371)653
Most studies considered metal matrix nanocomposites (NCs) because of their excellent mechanical and electrical properties. In recent years, external electric fields (EEFs) in the aforementioned NCs were identified as a crucial role in modulating mechanical behavior. The EEF may affect strength, hardness, ductility, and fracture toughness. The explanation for these changes is the interaction of EEF with the nanoparticles in the metal matrix. In the present study, the effects of various EEF values on the mechanical properties of Al/Cu/Al three-layer NCs (TLNCs) were assessed using the molecular dynamics (MD) modeling method and LAMMPS software. MD findings predicted that the EEF reduced the physical stability and mechanical strength of modeled samples. Physically, this performance resulted from a decrease in attraction force among distinct particles inside the computing box in the presence of EEF. The proposed samples' ultimate tensile strength (UTS) and Young's modulus (YM) decreased to 2.587 GPa and 20.19 GPa, respectively, when the EEF value increased to 0.05 V/Å. Finally, it was determined that EEF is a crucial parameter in the mechanical development of MMNC structures and should be used in mechanical bacterial design in industrial applications. © 2024 Elsevier B.V.
Hussein, S.A.,
Omar, I.,
Saddam, A.B.,
Baghoolizadeh, M.,
Salahshour, S.,
Pirmoradian, M. International Journal of Thermofluids (26662027)24
While machine learning has become the new way of analyzing data, neutral networks form the basis of this revolutionary technology. In this work, we shall employ the power of neural networks to analyze and demystify the processes in nanofluids. By combining the precision of neural networks with the optimization capabilities of genetic algorithms, we aim to create a more accurate and efficient prediction model for MWCNT-alumina/water-ethylene glycol (80:20) hybrid antifreeze. Our approach entails using an MLP neural network and several training functions (LM, GD, BFGS, BN) with an adjustable number of neurons. The inputs of the network are φ (solid volume fraction or ϕ), temperature (T), and shear rate (γ), and the output is μnf of MWCNT-alumina/water-ethylene glycol (80:20) hybrid anti-freeze. To improve the accuracy of the final model, we use genetic optimization to make final adjustments to the parameters of the neural network. Utilizing the detailed analysis of the primary characteristics of these algorithms, we conclude that the BFGS function is the best to obtain neural network training. Steady performance achieved by this function—0.99828 of the R-value and RMSE value significantly equal to 0.213—illustrates good stability and accuracy of the suggested model. This work contributes to progressing the existing knowledge about the behavior of nanofluids and can stimulate further improvement in heat transfer and energy utilization. © 2024 The Author(s)
Hashemian, M.,
Jasim, D.J.,
Mohammad sajadi s., S.M.,
Khanahmadi, R.,
Pirmoradian, M.,
Salahshour, S. Heliyon (24058440)10(9)
This research studied the dynamic stability of the Euler-Bernoulli nanobeam considering the nonlocal strain gradient theory (NSGT) and surface effects. The nanobeam rests on the Pasternak foundation and a sequence of inertial nanoparticles passes above the nanobeam continuously at a fixed velocity. Surface effects have been utilized using the Gurtin-Murdoch theory. Final governing equations have been gathered implementing the energy method and Hamilton's principle alongside NSGT. Dynamic instability regions (DIRs) are drawn in the plane of mass-velocity coordinates of nanoparticles based on the incremental harmonic balance method (IHBM). A parametric study shows the effects of NSGT parameters and Pasternak foundation constants on the nanobeam's DIRs. In addition, the results exhibit the importance of 2T-period DIRs in comparison to T-period ones. According to the results, the Winkler spring constant is more effective than the Pasternak shear constant on the DIR movement of nanobeam. So, a 4 times increase of Winkler and Pasternak constants results in 102 % and 10 % of DIR movement towards higher velocity regions, respectively. Furthermore, the effect of increasing nonlocal and material length scale parameters on the DIR movement are in the same order regarding the magnitude but opposite considering the motion direction. Unlike nonlocal parameter, an increase in material length scale parameter shifts the DIR to the more stable region. © 2024 The Authors
Mottaghi, A.,
Mokhtarian, A.,
Hashemian, M.,
Pirmoradian, M.,
Salahshour, S. Forces in Mechanics (26663597)17
This research investigates the free vibrational behavior of a functionally graded porous (FGP) nanoplate resting on an elastic Pasternak foundation in a hygrothermal environment. The nanoplate is modeled based on the nonlocal strain gradient theory (NSGT) and considering several plate theories including the CPT (classical plate theory), the FSDT (first-order shear deformation theory), and the TSDT (third-order shear deformation theory). Several patterns are investigated for the dispersion of pores, and the surface effects are incorporated to enhance the precision of the model. The governing equations and boundary conditions are derived via Hamilton's principle and an exact solution is provided via the Navier method. The impacts of several parameters on the natural frequencies are inspected such as length scale and nonlocal parameters, surface effects, porosity parameter, hygrothermal environment, and coefficients of the foundation. The results show that the impact of the porosity parameter on the natural frequencies of nanoplates is significantly dependent on the porosity distribution pattern. It is discovered that by increasing the porosity parameter from 0 to 0.6, the relative changes of natural frequencies vary from a decrease of 30 % to an increase of 6 %. © 2024 The Author(s)
Ali, A.B.,
Al-zahiwat, M.M.,
Fadhil, D.A.,
Nemah, A.K.,
Salahshour, S.,
Pirmoradian, M. International Journal of Thermofluids (26662027)23
Fossil fuels cause global warming and create greenhouse gases that cause irreparable environmental damage. On the other hand, because the combustion reactions are not completely done, dangerous compounds, such as nitrogen or carbon monoxide are produced which are very toxic and dangerous. As a result, innovative methods were implemented in combustion processes. One such method is to use a catalyst during the combustion process. This study used a molecular dynamics method to examine how the concentration of CuO[sbnd]CeO2 catalyst affected air-methane combustion in a helical microchannel. The results show that the maximum (Max) values of density (Dens), velocity (Velo), and temperature (Temp) in the excess oxygen (EO) state were 0.142 atoms per second, 0.35 Å/ps, and 1089 K, respectively, when the atomic ratio of CuO[sbnd]CeO2 increased from 1 % to 4 %. Subsequently, these values exhibited a declining trend. Also, the values of heat flux (HF), thermal conductivity, and combustion efficiency in 4 % catalyst reached the max values of 2038 W/m2, 1.15 W/m·K and 88 %. The results related to the max values of Dens, Velo, and Temp for the oxygen deficiency state had a similar trend and increased to the max values of 0.103 atom/Å3, 0.41 Å/ps, and 1024 K in 4 % catalyst, and then decreased by increasing the catalyst ratio of CuO[sbnd]CeO2 and reaching 10 %. The thermal behavior of nanostructure was more optimal in the deficient oxygen medium. © 2024 The Author(s)
Baghoolizadeh, M.,
Pirmoradian, M.,
Mohammad sajadi s., S.M.,
Salahshour, S.,
Baghaei, S. Tribology International (0301679X)195
Genetic algorithms and machine learning methods can accurately anticipate hybrid nanofluids' complicated rheology. Scientists and engineers can understand hybrid materials by using genetic algorithms to optimize and machine learning to discover complicated relationships between input variables and rheological responses. As a continuation of the author's previous research on the rheological properties of a nano-lubricant based on engine oil and hybrid nanoparticles, this study uses machine learning and genetic algorithms to theoretically assess the dynamic viscosity of the MWCNT-MgO/oil SAE 50 hybrid nanofluid and identify optimal properties. MLR, D-Tree, Ridge, PLR, SVM, Lasso, ECR, GPR, and MPR are used for regression analysis. Best multi-objective issue solutions are represented by the Pareto front. The NSGA-II algorithm determines the Pareto front. The MPR and NSGA-II algorithms provide a Pareto front with the most precise optimal spot boundaries. The Weighted Sum Method (WSM) simplifies multi-objective problems into single-objective problems, making optimal solutions easier to find. The results show that the maximum margin of deviation for μnf and τ is − 2.5615 and − 5.239, respectively. According to the Taylor chart, the best μnf mode for R, RMSE and STD is equal to 0.9983, 7.6639, 130.0056. Also, these values for τ are equal to 0.9996, 15.4515, and 516.0219. © 2024 Elsevier Ltd
Song, X.,
Baghoolizadeh, M.,
Alizadeh, A.,
Jasim, D.J.,
Basem, A.,
Sultan, A.J.,
Salahshour, S.,
Pirmoradian, M. International Communications in Heat and Mass Transfer (07351933)156
This paper aims to explore the utilization of machine learning techniques for the accurate prediction of rheological properties in a specific nanofluid system, ZnO(50 %)-MWCNTs (50 %)/Ethylene glycol (20 %)-water (80 %), designed for nano-refrigeration applications. The effective manipulation of the rheological behavior of nanofluids is pivotal for enhancing their heat transfer efficiency and overall performance. By harnessing the predictive power of machine learning, this study endeavors to unravel the intricate relationships governing the rheological characteristics of the nano-refrigerant, ultimately contributing to the development of advanced cooling solutions. The obtained results show that μnf of ZnO(50%)-MWCNTs (50%)/ Ethylene glycol(20%)-water(80%) nano-refrigerant is little affected by T, and even when T varies, this result does not alter much. Also, the lowest μnf occurs when it has the highest temperature and the lowest γ and φ. Finally, it was concluded that the best algorithm in terms of the Taylor diagram for μnf output is the MPR algorithm and the worst is the ECR algorithm and the pattern of γ changes shows that the ideal value of γ is the biggest when μnf levels fall in tandem with their growth. © 2024 Elsevier Ltd
Esfe, M.H.,
Esmaily, R.,
Khabaz, M.K.,
Alizadeh, A.,
Pirmoradian, M.,
Rahmanian, A.,
Toghraie, D. Tribology International (0301679X)178
In this study, a unique incorporated version is presented to enhance the dynamic viscosity of MWCNT- Al2O3 (40:60)/Oil 5W50 hybrid nanofluid (HNF) the usage of the 3 maximum vast and vital powerful parameters corresponding to temperatures, solid volume fractions (SVFs) and shear rates (SRs). An empirical relationship between energy consumption and these characteristics is presented. Thus, ANNs are used to develop a high-level data analysis model to predict the dynamic viscosity of MWCNT-Al2O3 (40:60)/Oil 5W50 HNF. A sensitivity analysis is employed to assess the importance of various parameters of MWCNT- Al2O3 (40:60)/Oil 5W50 HNF dynamic viscosity and the position of temperature, SVF and SR in simulation. It is found that the highest dynamic viscosity values are observed at temperatures below 5 °C. In addition, the dynamic viscosity is reduced by SR changes from 0 rpm to 800 rpm. Statistical analysis shows that the model performance is nearly equal, ranging between 0.98, 0.978, and 0.925, and that the errors are less than 2.6 % for the training, testing, and validation phases, respectively. Overall, it could be determined that the ANN simulation can generate the connection between the measured dynamic viscosity and anticipated dynamic viscosity of HNF. © 2022 Elsevier Ltd
This paper examines the design and fabrication of a soft robot that can connect to a virtual reality environment. This study's primary objective is to utilize these technologies concurrently and demonstrate their applicability in various applications, particularly rehabilitation. Therefore, the process of designing and modeling the soft robot is carried out, and an applied model is created using a 3D printer and silicon material, which is then installed on gloves. Using Unity software, a virtual reality environment is created in which programs, commands, and Arduino processors control the movements of the soft robot, allowing the user to move and pick up an object in a real environment while wearing gloves, and to adjust the amount of pressure and angle of its motion based on the size of each virtual object. During the system evaluation phase, a delay in the performance and reaction time of the soft robot installed on the gloves is observed. This delay is reduced by modifying the programming structure, resulting in optimal system functionality. This capability is used to create proper mobility conditions and rehabilitation for the majority of patients with wrist injuries resulting from strokes and accidents, and it may be effective in accelerating patients' recoveries. © 2023 The Authors
Rostamzadeh-renani, R.,
Baghoolizadeh, M.,
Mohammad sajadi s., S.M.,
Pirmoradian, M.,
Rostamzadeh-renani, M.,
Baghaei, S.,
Salahshour, S. Alexandria Engineering Journal (11100168)84pp. 184-203
For conducting an analysis of the experimental data, it is imperative to establish a mathematical correlation between the input and output variables. This entails executing a curve fitting or regression procedure on the data, for which numerous methodologies exist. Within the scope of present investigation, the design variables encompass the solid volume fraction (φ) and temperature. Thermal conductivity (TC) of MWCNT-CuO-CeO2 (20-40-40)/water hybrid nanofluid (HNF) is also the objective function. Ten different types of regressors are utilized for regression operations which are Multiple Linear Regression (MLR), Decision Tree (D-Tree), Multi-Layer Perceptron (MLP), Support Vector Machine (SVM), Extreme Learning Machine (ELM), Radial Basis Function (RBF), Adaptive Neuro-Fuzzy Inference System (ANFIS), Gaussian Process Regression (GPR), Multivariate Polynomial Regression (MPR) and Group Method of Data Handling (GMDH). Once the governing equations linking the design variables and the objective functions have been established, these equations can be employed to forecast the simulation data. By substituting the above input values into the equations, we can calculate the corresponding output values for the TC of the HNF. The results obtained from the MPR algorithm are compared to the experimental data. For the GPR, MLR, D-Tree, ELM, MPR, MLP, RBF, SVM, ANFIS, and GMDH algorithms, the maximum margin of error is found to be 0.031, 0.02579, 0.028946, 0.033889, 0.01568, 0.02515, 0.03485, 0.03, 0.0385, and 0.0178, respectively. Moreover, the kernel density estimation diagram indicates the gap between experimental data and data predicted by regression algorithms. Finally, it is evident that the MPR algorithm demonstrates to have a reduced residual dispersion, with the residuals approaching zero. © 2023 THE AUTHORS
Salarnia, M.,
Toghraie, D.,
Fazilati, M.A.,
Mehmandoust, B.,
Pirmoradian, M. Journal of the Taiwan Institute of Chemical Engineers (18761070)143
Background: Oscillating heat pipes (OHP) are equipment for heat transfer (HT) with a high heat transfer capacity which transfer heat from a heat source to a heat sink. One of the most significant factors affecting the performance of the heat pipes is the operating fluid contained inside them. Nanofluids (NFs), the fluids containing nanoparticles (NP), improve the thermal conductivity (TC), and HT over the base fluid. Methods: This study investigated the physical and thermal properties behaviors of water and Fe-Fe2O3-Fe3O4/water NFs in an OHP with copper (Cu) walls. In this approach, the molecular dynamics (MD) simulation was used. The current simulation was performed using LAMMPS software. By solving Newton's equation of motion, the trajectories of particles were simulated over time. Significant findings: After 10 ns, the numerical value of heat flux (HF) in the presence of water converged to 1354 W/m2. The maximum numerical density of simulated Fe-Fe2O3-Fe3O4/water NF in the OHP reached 0.016 atom/Å3, 0.021 atom/Å 3, and 0.022 atom/Å3 values, respectively. The numerical maximum velocity of simulated Fe-Fe2O3-Fe3O4 water NF in the OHP converged to 0.057 Å/ps, 0.051 Å/ps, and 0.044 Å/ps, respectively. The numerical maximum temperature of simulated Fe-Fe2O3-Fe3O4 /water NF in the OHP was 522.68 K, 483.48 K, and 452.77 K, respectively. The numerical values of HF of simulated Fe-Fe2O3-Fe3O4/water NF in the OHP increased by 1462 W/m2, 1505 W/m2, and 1561 W/m2, respectively. Finally, the above studies expect an optimal mechanism for HT in the practical applications to be provided. © 2023 Taiwan Institute of Chemical Engineers
Tribology International (0301679X)187
In the present study, using 15 machine learning algorithms (MLP, SVM, RBF, ELM, ANFIS, D-Tree, MLR, MPR, BPNN, BN, LM, GD, BFGS, XGB and GMDH), the rheological behavior of oil SAE40 based nano-lubricant in the presence of MWCNT and MgO nanoparticles was predicted. According to the review of several criteria and data analysis charts, it can be concluded that the best algorithm for predicting fluid properties in this article, which are μnf and torque, is equal to GMDH and MPR, respectively. Also, it can be seen that the data predicted by the machine learning algorithms were able to predict the experimental data very accurately. According to this correlation and the high accuracy of the algorithms, data analysis can be performed on the equations. After determining the range of input variables and specifying the objectives, optimization can be done by the NSGA-Ⅱ algorithm. Considering that the problem is multi-objective, it is not possible to find a point where both functions are at their minimum value. For this purpose, optimization provides a set of points to the user to choose the optimal point among them based on the need. © 2023 Elsevier Ltd
European Physical Journal Plus (21905444)137(6)
In today’s world, the phenomenon of heat transfer (HT) and change of phase occurs in a wide range of industrial processes. Therefore, the need for high heat intensity HT in a short time has been considered by many industries. Nanofluids (NFs) have attracted the attention of many researchers compared to fluids containing particles with micro dimensions of ordinary fluids because of their high thermal conductivity (TC) and HT. The use of NFs in the industry leads to the increased thermal performance of industrial equipment. In this study, the atomic behavior and thermal attributes of ammonia/copper nano-refrigerant (NR) for the first time in the attendance of an external electric field (EEF) in an aluminum nanochannel are investigated by the molecular dynamics simulation (MDS) procedure. This study discusses how effective and significant thermophysical attributes like density and TC are important for NFs to improve HT. The thermophysical conduct of the sample under study is examined by analyzing nanoparticles (NPs)’ density rate and concentration, condensate duration, and TC of the NF. Outcomes show that the rate of phases changed particles from gas to liquid in ammonia base fluid (BF) was 39%, and this change was estimated after 3.59 ns. The TC converges to 0.64 W/(m K) after 7 ns. Adding Cu NPs causes an enhancement in the TC of the sample. So, adding NPs of Cu with a 0.1% ratio leads to the increased rate of phases changed particles to 58% and decreases the duration of the phase-change process. Due to the high TC of the metal NPs, the TC of NF enhances to 0.76 W/(m K) with copper NPs. © 2022, The Author(s), under exclusive licence to Società Italiana di Fisica and Springer-Verlag GmbH Germany, part of Springer Nature.
Journal Of Molecular Modeling (16102940)28(6)
Generally, the addition of nanoparticles to a fluid significantly increases the thermal conductivity of structures. In the present study, the effect of nanoparticle volume ratio and initial temperature on ammonia/copper nano-refrigerant’s thermal behavior in an external electric field in an aluminum nanochannel was studied by molecular dynamics simulations. To study the thermal behavior of the structures, quantities such as particle phase-changed rates (condensation process), phase change duration, and thermal conductivity were investigated. Results show that with the addition of 5% copper to the base fluid, the rate of the phase-changed particles increases from 53 to 71% during 2.40 ns. Also, increasing the volume ratio of nanoparticles up to 5% leads to an increase in thermal conductivity from 0.76 to 0.86 W/mK. On the other hand, increasing the initial temperature up to 350 K reduces the phase-changed particles’ rate from 53 to 49% during 2.9 ns. The initial temperature increases from 300 to 350 K, and the thermal conductivity decreases from 0.76 to 0.73 W/mK. The results of this simulation are expected to improve the thermal performance of different nano-refrigerants. © 2022, The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.
Esfe, M.H.,
Hajian, M.,
Toghraie, D.,
Khabaz, M.K.,
Rahmanian, A.,
Pirmoradian, M.,
Rostamian, H. Egyptian Informatics Journal (11108665)23(3)pp. 427-436
In this study, the prediction of dynamic viscosity (µnf) of MWCNT-Al2O3 (30:70)/ Oil 5W50 hybrid nano-lubricant using Artificial Neural Network (ANN) is performed. The objective of the present research is to investigate the effect of temperature and solid volume fraction (SVF) to predict the shear rates (SR) and µnf using ANN. The feed-forward ANN consists of a multilayer perceptron network (MLP), which is capable of predicting µnf in connection with experimental data of temperature, SR and SVF. Sensitivity analysis is used to evaluate the importance and role of temperature, SR, and SVF in experimental µnf variations. ANN is generated and tested with experimental data sets and the results show that there was a good agreement between the actual and predicted ANN values. Moreover, the results of ANN simulation are compared with other data processing methods such as Support Vector Machine (SVM), Partial Least Squares (PLS), Principal Component Regression. In addition, the results of the residual value of ANN with seven neurons for µnf can be very small and close to the expected normal value. From this, it can be concluded that the given model can expect exact values. © 2022
Mechanics Based Design of Structures and Machines (15397742)50(12)pp. 4387-4408
The size-dependent sound transmission loss problem of an air-filled functionally graded material cylindrical shell subjected to a plane progressive sound wave with even and uneven porosity distributions was analytically studied using a nonlocal strain gradient and the first-order shear deformation theories. To simulate the heterogeneous material, the impressive material properties were supposed to be associated with the porosity volume fraction model, based on a power-law model. They were suggested to be constantly changeable along the thickness direction. The motion equations were extracted by Hamilton’s principle and then solved using the Fourier-Bessel series. The accuracy of the obtained formulation were strictly proved by comparing the data accessible in the literature. Parameter studies reveal the effects of material gradient index, size scale factors, porosity volume fraction, and incident angles on the variations in the amplitude of sound transmission loss through the nanoshell. © 2020 Taylor & Francis Group, LLC.
Moatallebi, M.A.,
Hashemian, M.,
Eftekhari, S.A.,
Toghraie, D.,
Pirmoradian, M. Waves in Random and Complex Media (discontinued) (17455049)
In the present work, a numerical investigation is provided for free vibrational and aeroelastic stability features of nanobeams made of Functionally Graded Material (FGM) resting on an elastic Pasternak foundation. The FGM nanobeam's mechanical properties are considered to differ based on power-law and exponential functions in the thickness direction. The effect of size is modeled in terms of the Gurtin-Murdoch surface elasticity theory and the Nonlocal Strain Gradient Theory (NSGT) is employed for incorporating the surface effects. Mathematical modeling of the FGM nanobeam is oriented by three various beam theories including Reddy's third-order Shear Deformation Beam Theory (TSDBT), Timoshenko beam theory (TBT), and Euler-Bernoulli Beam Theory (EBT), moreover, the aerodynamic pressure is determined in terms of the linear supersonic piston theory. It is concluded that when the surface effects are incorporated, the width-to-length ratio of the FGM nanobeam plays a sensible role in determining the natural frequencies; but it has no sensible effect on the flutter boundaries. Numerical results reveal that the importance of the surface effects increases as the values of thickness-to-length and width-to-length ratios decrease. © 2023 Informa UK Limited, trading as Taylor & Francis Group.
Thin-Walled Structures (02638231)169
In this study, using modified strain gradient theory (MSGT) and the first-order shear deformation assumption (FSDA) framework, wave propagation through air-filled double-walled functionally graded (FG) cylindrical microshells subjected to linear and non-linear thermal loadings are investigated. MSGT has the advantage of having up to three scale parameters and can successfully reproduce size effects. The power-law model is used to express the distribution of material characteristics over the thickness of each shell due to characteristics varying by temperature, and the application of Hamilton's principle results in deducing vibroacoustic equations in coupled relations. The size-dependent coupled vibroacoustic governing equations are solved using an analytical approach in conjunction with a double Fourier series, with the final result providing the appropriate Sound Transmission Loss (STL) equation. The developed solution's accuracy and precision are examined by comparing it to data available from previous studies. Parameter studies reveal the impacts of temperature distribution, functionally graded index, incident angles, acoustic cavity depth, and length scale parameter on STL through double-walled FG cylindrical microshells. © 2021
Computational Materials Science (09270256)199
In this computational work, the mechanical behavior of silicon (Si) samples in the presence of iron (Fe) nanoparticles is investigated by using the Molecular Dynamics (MD) method. Technically, in our simulations, Si sample and Fe nanoparticles are represented by Embedded Atom Model (EAM) for atomic interaction parameter. The MD simulation results on atomic structure's mechanical behavior have been reported by calculating some physical parameters such as potential energy (per atom), temperature, Young's modulus, and ultimate strength. The results indicate the atomic stability of the Si-Fe structure just after 5 ns. By inserting the Fe nanoparticles into the pristine Si sample, Young's modulus of the structure reaches 155.18 GPa, and its ultimate strength increases to 40.30 GPa. On the other hand, as the cross-sectional area of the simulated nanostructure increases, the atomic interaction between the Si sample and the Fe nanoparticles decreases. Therefore, the values of Young's modulus and the ultimate strength of the structure are decreased. Generally, the results of this simulation show Fe nanoparticles’ significant effect on the pristine Si sample's mechanical properties, which can be used for industrial applications. © 2021 Elsevier B.V.
Journal Of The Brazilian Society Of Mechanical Sciences And Engineering (16785878)43(3)
Nowadays, piezoelectric materials are used as smart nanostructures in many engineering applications. Polyvinylidene fluoride (PVDF) is one of the piezoelectric polymeric materials which has fascinated the attention of the scientific community due to its remarkable properties. In the present study, dynamic stability and the parametric resonance of a Mindlin PVDF nanoplate lying on an elastic medium under electromechanical loadings and a moving nanoparticle are investigated. First, Hamilton's principle is used to obtain the partial equations governing the transverse oscillations of the PVDF nanoplate. By utilizing the theory of nonlocal piezoelasticity, the small-scale effects are applied to the equations. Navier’s approach is employed to procure the solution for the simply supported nanoplate. Then, the boundaries of instability in the plane of parameters are obtained by applying the energy-rate method to the governing time-varying ODEs. The results demonstrate that the increase in the nonlocal parameter and reduction of the nanoparticle movement path decrease the dynamic stability of the PVDF nanoplate. Also, the nanoplate made of PVDF materials is dynamically more stable than the nanoplate made of PZT-4 piezoceramic materials. Moreover, the piezoelectric voltage can be used to control the parametric resonance conditions of nanostructures. The results of this study have the potential to be utilized in the accurate design of nanoscale piezoelectric mass sensors in nanoelectromechanical systems. © 2021, The Brazilian Society of Mechanical Sciences and Engineering.
Mechanics of Materials (01676636)145
This study addresses the dynamic stability of an Euler–Bernoulli nanobeam under time-dependent axial loading based on the nonlocal strain gradient theory (NSGT) and considering the surface stress effects. The studied nanobeam cross-section was rectangular, and simply-supported boundary conditions were assumed. Moreover, a uniform thermal gradient was applied to the nanobeam. The elastic medium was modeled based on the Pasternak theory. The strain–displacement relations were derived using the Von Kármán equations. The governing equations were obtained by the energy method and applying the Hamilton's principle. Furthermore, the Bolotin and Incremental Harmonic Balance (IHB) methods were used to solve the differential equations. This study investigates the impact of such parameters as the small-scale parameter, the material length scale, surface effects, elastic medium parameters, temperature variations, geometry, and the static loading factor on the Dynamic Instability Region (DIR). The results are suggestive of the shift of the DIR to lower frequency zone by increasing the small-scale Eringen's nonlocal theory parameter, whereas an increase in the material length scale from the strain gradient theory moves the region to higher frequencies. In case the said parameters are equal, the result conforms to the classical beam theory. In addition, assuming a Pasternak medium and taking into account the effects of surface stress (Young's modulus and the residual stress of the surface) shifts the DIR to higher frequencies, whereas applying a compressive static load moves the region to lower frequencies. Moreover, depending on the thermal expansion coefficient of the medium, temperature variations can also displace the DIR. © 2020 Elsevier Ltd
Journal Of The Brazilian Society Of Mechanical Sciences And Engineering (16785878)42(12)
The purpose of this work is to design and fabricate a balanced passive robotic arm with the capability of applying variable mass to the end-effector in order to upper limb rehabilitation. To achieve this purpose, the first step is associated with establishing a robot structural design in the CAD environment. The next step is focused on developing the kinematic model based on the degrees of freedom and joint range of motion of the lower legs. Thereafter, the potential energy functions are determined for the springs and weight of components applied in the mechanism. The genetic algorithm is employed as a proper optimization program to extract the system design parameters, including the spring stiffness coefficients and their placement positions within the system. A prototype is fabricated for a balanced robot, and the end-effector mass variations are utilized to develop an adjustable balance capability. To create balance in the system, several items are designed, consisting of a control panel, two electric motors, and an electronic processor. This situation provides an equivalent force equal to the weight of selected mass from the end-effector to the user’s hand. (It is done by a reverse process.) The actual mass required for robot balance is compared to the mass defined in the simulation environment. The evaluation results indicate that it is possible to create an optimized balance by using the simulation outputs. © 2020, The Brazilian Society of Mechanical Sciences and Engineering.
Pirmoradian, M.,
Naeeni, H.A.,
Firouzbakht, M.,
Toghraie, D.,
Khabaz, M.K.,
Darabi, R. Computer Methods and Programs in Biomedicine (01692607)187
Background and Objective: The dental implant is one of the long term proper remedies to recover a missed tooth as a different prosthetic rehabilitation way. The finite element (FE) method and photoelasticity test are employed to achieve stress distribution and sensitivity in dental implants in order to obtain optimum length and thread pitch. Methods: The finite element method and experimental test are developed to evaluate stress distribution and sensitivity around dental implants. Three dimensional FE models of implant-abutment, cortical bone and cancellous bone are created by considering a variation of 0.6 to –1 mm on threads pitch while the implant lengths range from 8.5 mm to 13 mm. Then, axial and oblique forces are applied to the models to obtain the resultant stress contours. Results: The results indicate that the resultant von Mises stresses in the implant-abutment, cortical bones, and cancellous bones are different. The optimized setting for length and pitch is suggested according to maximum von Mises stress and sensitivity analysis. Conclusions: It is concluded that the present FE model accurately predicts stress distribution pattern in dental implants. The results indicate that sensitivity of length play a more significant role in comparison with thread pitch. The accuracy of FEM results in comparison with those of the photoelasticity test recommends applying computation methods in medical practice as great potential in terms of future studies. © 2019
Mechanics of Materials (01676636)148
In this study, the dynamic stability of a Timoshenko nanobeam under the intermittent movement of nanoparticles is investigated considering surface effects. Simply-supported boundary conditions are assumed for a rectangular cross-section beam. The elastic foundation is modeled as a Pasternak elastic foundation. Also, the role of the nanoparticle inertia is considered. The nanoparticles move over the beam continuously with a constant velocity, and the friction between particles, and the beam is ignored. Governing equations are derived by Hamilton's principle in conjunction with nonlocal and Gurtin-Murdoch theories. Dynamic stability analysis of the nanobeam under induced excitation of moving nanoparticles is carried out, and the stability and instability regions are derived by incremental harmonic balance method (IHBM). The stability of the system is described in the plane (mass-velocity). A detailed study is conducted to examine the effects of various parameters such as the small scale parameter, surface constants, Pasternak foundation coefficients, and nanoparticles inertia on the dynamic instability region (DIR) of the nanobeam. The results show that considering surface theory has a negligible effect on the DIR of the nanobeam under the intermittent passage of nanoparticles. Pasternak and Winkler spring constants increase the stiffness and stability of the nanobeam. Also, considering moving mass inertia and small scale parameter shifts the DIR to the lower frequency zone. © 2020 Elsevier Ltd
Physica A: Statistical Mechanics and its Applications (03784371)554
In this paper, the dynamic instability of double-walled carbon nanotubes (DWCNTs) enclosed by an elastic medium under parametric excitation of sequential moving nanoparticles has been analyzed. Using Hamilton's principle, the governing equations are derived based on the Euler–Bernoulli beam theory. All inertial terms of the moving nanoparticles are taken into account and small-scale effects are applied in the dynamic formulation based on the Eringen's nonlocal elastic theory. The incremental harmonic balance (IHB) technique is applied to estimate the parametric instability regions of the DWCNT carrying the moving nanoparticles. It is found that the stability of the system could be improved in some cases, such as taking into account the Van der Waals (vdW) effect, reducing the amplitude of axial oscillating force, enlarging the amplitude of the static axial tensile force and enhancing the stiffness of the elastic medium. The accuracy of the presented analyses is examined by comparing the results with those reported in the literature and very good agreement is observed. The results of this paper can be used in the design of advanced nano-electro-mechanical systems (NEMS) and nanodrug delivery systems, in which nanotubes act as the basic elements. © 2019 Elsevier B.V.
Mechanics of Materials (01676636)142
Parametric resonance is an important phenomenon that may be evinced in applying carbon nanotubes for the delivery of nanoparticles. This paper aims to investigate dynamics instability of double-walled carbon nanotubes (DWCNTs) surrounded by elastic medium and excited by a sequence of moving nanoparticles. The DWCNT is modeled as two Euler-Bernoulli beams interacting between them through van der Waals (vdW) forces. Based on Eringen's nonlocal elastic theory to consider the small-scale effects, the governing equations are derived by using Hamilton's principle. All inertial terms of the moving nanoparticles are taken into account. In addition, the van der Waals force between the constitutive atoms of the moving nanoparticle and those of the nanotube is considered. By utilization of the Galerkin method, the partial differential equations (PDEs) of motion are reduced to couple ordinary differential equations with time-varying coefficients describing a parametrically excited nanosystem. Then, an incremental harmonic balance (IHB) method is implemented to calculate the instability regions of the DWCNT. The results show that considering the vdW effects, increasing the amplitude of the static axial tensile force, reducing the amplitude of axial oscillating force, and increasing the stiffness of the elastic medium improve stability of the system. A comparison between the results with those reported in the literature is performed to verify the precision of the presented analyses. © 2019
Mechanics of Materials (01676636)141
Using an energy-based method, this paper sought to analyze dynamic stability and parametric resonance of single-layered graphene sheets (SLGSs) embedded in thermal environment and elastic medium while carrying a nanoparticle moving along an elliptical path. In order to present a realistic model, all inertial effects of the moving nanoparticle are taken into account in the dynamic formulation of the system. Equations governing the transverse vibrations of the embedded SLGS are obtained using the Hamilton's principle. Small-scale effects based on the Eringen's nonlocal elasticity theory are considered in deriving the motion equations. The equations governing the reduced model are calculated based on the Galerkin method. To calculate the instability boundaries, the energy-rate method is applied on the ordinary differential equations (ODEs) governing the system oscillations. The effects of nonlocal parameter, the nanoparticle motion path radii, SLGS length-to-width ratio, temperature change of the thermal environment, stiffness of the elastic medium and boundary conditions of SLGS on the parametric instability regions are examined. The results show that these parameters influence the system stability, so that a decrease in the nonlocal parameter, the SLGS length-to-width ratio and the nanoparticle motion path radii and also an increase in the stiffness coefficients of the elastic medium improve the system stability. The model presented in this paper is validated by comparing the observations with those published in previous studies. © 2019 Elsevier Ltd
Acta Mechanica Sinica/Lixue Xuebao (16143116)35(1)pp. 242-263
Parametric resonance is one of the most important issues in the study of dynamical behavior of structures. In this paper, dynamic instability of a moderately thick rectangular plate on an elastic foundation is investigated in the case of parametric and external resonances due to periodic passage of moving masses. The governing coupled partial differential equations (PDEs) of the system, with consideration of the first-order shear deformation theory (FSDT) or Mindlin plate theory, are presented and they are reduced to a set of ordinary differential equations (ODEs) with time-dependent coefficients using the Galerkin procedure. All inertial components of the moving masses are adopted in the dynamical formulation. Instability survey is carried out for three different loading trajectories considerably interested in many practical applications of the issue, i.e. rectilinear, diagonal and orbiting trajectories. In order to analyze the resonance conditions, the incremental harmonic balance (IHB) method is introduced to calculate instability boundaries, as well as external resonance curves in parameters plane. A comprehensive study is done to assess effects of thickness ratio and foundation stiffness on the resonance conditions. It is found that an increase in the plate’s thickness ratio leads to a reduction in values of critical parameters. Moreover, it is observed that increasing the foundation stiffness moves the instability regions and resonance curves to higher frequencies of the moving masses and also leads to further stability of the parametrically excited system at lower frequencies. Time response simulations done via Runge–Kutta method confirmed the results predicted by IHB method. © 2018, The Chinese Society of Theoretical and Applied Mechanics; Institute of Mechanics, Chinese Academy of Sciences and Springer-Verlag GmbH Germany, part of Springer Nature.
Journal of Mechanics (18118216)34(4)pp. 483-494
This study investigated the effects of considering surface and nonlocal energy parameters on the buckling analysis of double piezoelectric nanoplate (DPNP) embedded in elastic foundations and thermal environments. Both in-phase and out-of-phase modes of buckling and various boundary conditions are studied and compared with each other. The governing equations were derived by drawing on the principle of virtual work and then solved by employing the finite difference method. Finite difference solution was validated using Navier's method and journal references. A parametric study was also launched in order to investigate the effects of the external electric voltage, nonlocal parameters, different boundary conditions, elastic foundations and thermal environments on the surface effect of DPNP buckling. The obtained numerical results showed that the influence of surface stress on in-phase and out-of-phase modes of buckling of the DPNP was enhanced by augmenting the nonlocal parameters and external electric voltage; on the other hand, it was found to be decreased by increasing elastic foundations and temperature changes. In addition, the value of surface stress effects for the in-phase mode was higher than that of the out-of-phase one. Copyright © The Society of Theoretical and Applied Mechanics 2018.
Archive of Applied Mechanics (14320681)88(8)pp. 1411-1428
Elastodynamic behavior analysis of structures under moving loads is of great interest in most engineering fields. In this study, dynamic instability due to parametric and external resonances of simply supported thin rectangular plates on an elastic foundation under successive moving masses is investigated as a linear time-periodic problem. Effects of all components of moving mass inertia are considered in the analysis. The governing partial differential equation of motion is transformed to a set of ordinary differential equations using the Galerkin method. A comprehensive study of resonance conditions is carried out for two cases: (1) the masses move on a rectilinear path parallel to the longitudinal edges of the plate, and (2) a sequence of moving masses along the diagonal of the plate. Homotopy perturbation method (HPM) is employed as a semi-analytical method to obtain stable and unstable zones in a parameters space in additions to external resonance curves. In order to validate the HPM results, Floquet theory is applied to the state-space equations. A good agreement between two methods is observed. The results of this study are useful for the design of road pavements resting on foundation soil, slab-type bridges, airport pavements, and decks of ships on which aircrafts land. © 2018, Springer-Verlag GmbH Germany, part of Springer Nature.
International Journal of Mechanical Sciences (00207403)142pp. 191-215
This paper deals with the induced instability due to parametric resonance of rectangular plates traversed by inertial loads and lying on elastic foundations. The extended Hamilton's principle is employed to derive the partial differential equation associated with the transverse motion of the plate. Subsequently, this equation is transformed into a set of ordinary differential equations by the Galerkin method. Including vertical, centripetal and Coriolis acceleration terms related to the moving mass transition in the analysis leads to governing equations with time-varying mass, damping and stiffness coefficients. Particularly, the intermittent passage of masses along rectilinear paths, or the motion of an individual mass along an orbiting path, permits to subcategorize the problem as a parametrically excited system with periodic coefficients. By applying the incremental harmonic balance (IHB) method, the stability of the induced plate vibrations is investigated, revealing an emersion of instability tongues in the parameters plane. Semi-analytical results are provided for various boundary conditions of the plate which got verified through direct numerical simulations and other results reported in the literature. © 2018 Elsevier Ltd
Nonlinear Dynamics (0924090X)89(3)pp. 2141-2154
In this paper, the dynamic stability of a simply supported beam excited by the transition of circulating masses is investigated by preserving nonlinear terms in the analysis. The intermittent loading across the beam results in a time-varying periodic equation. The effects of convective mass acceleration besides large deformation beam theory are both considered in the derivation of governing equations which is performed through adopting a variable-mass-system approach. In order to deal with the coupling between longitudinal and transversal deflections, the inextensibility assumption is implicitly introduced into the Hamiltonian formulation to reduce the model order. An appropriate interpretation is presented in order to maintain this approximation reasonable. Different semi-analytical methods are implemented to find the domains of stability and instability of the problem in a parameter space. By accounting the non-autonomous form of the governing equations, a qualitative change in behavior due to nonlinear terms is demonstrated which has not been addressed in previous studies. © 2017, Springer Science+Business Media Dordrecht.
Acta Mechanica (16196937)227(4)pp. 1213-1224
The problem of an elastic beam under the periodic loading of successive moving masses is investigated as a pragmatic case for studying dynamic stability of linear time-varying systems. This model serves to highlight the odds of multi-solutions coexistence, a form of hidden instability which reveals dangerous as it may be precipitated by the slightest disturbance or variation in the model. Since no engineering model perfectly represents a physical system, such situations for which Floquet theory naively predicts stability are potentially inevitable. The harmonic balancing method is used in order to thoroughly explore the stability diagrams for detecting these instability gaps. Although this phenomenon has also been described in other physical systems, it has not been addressed for beam–moving mass systems. This result may find particular importance in applications involving self-induced vibrations of elastic structures and hence also appears of practical relevance. © 2016, Springer-Verlag Wien.
Acta Mechanica (16196937)226(4)pp. 1241-1253
A Timoshenko beam excited by a sequence of identical moving masses is studied as a time-varying problem. The effects of centripetal and Coriolis accelerations besides the vertical component of acceleration of the moving mass are considered. Using Galerkin procedure, the partial differential equations of motion which are derived by Hamilton’s principle are transformed to ordinary differential equations. The incremental harmonic balance method is implemented to determine the boundary curve of instability and other companion curves of resonance in the parameter plane. A new approach for identifying the conditions of resonance is investigated by presenting an intuitive definition of resonance for time-varying systems. The influence of employing different deformation theories on the critical parameter values of stability and resonance curves is studied. The validity of the instability and resonance curves is examined by numerical simulations and also ascertained through comparing with those reported in the literature. © 2014, Springer-Verlag Wien.
Journal of Vibroengineering (13928716)16(6)pp. 2779-2789
In this paper, the dynamic stability analysis of a simply supported beam excited by a sequence of moving masses is investigated. All components of the mass acceleration including the centripetal, the Coriolis and the vertical one are considered. The periodical traverse of masses across the beam results to a linear time-periodic problem. The Floquet theory and the Incremental Harmonic Balance (IHB) method are implemented to obtain the boundary between stable and unstable regions in the parameters plane. A new approach for identifying the conditions of resonance is investigated by presenting an intuitive definition of resonance for time-varying systems. This approach enables the IHB method to determine inherent curves of resonance conditions besides its ability to find the boundary curve separating the stable and unstable regions. Numerical simulations confirm the correctness of resulted curves. © JVE INTERNATIONAL LTD. JOURNAL OF VIBROENGINEERING 2014.
Carbon nanotubes are widely used in the design of nanosensors and actuators. Any defect in the manufactured nanotube plays an important role in the natural frequencies of these structures. In this paper, the effect of vacancy defects on the vibration of carbon nanotubes is investigated by using an atomistic modeling technique, called the molecular structural mechanics method. Vibration analysis is performed for armchair and zigzag nanotubes with cantilever boundary condition. The shift of the principal frequency of the nanotube with vacancy defect at different locations on the length is plotted. The results indicate that the frequency of the defective nanotube can be larger or smaller or equal to the frequency of perfect one. The results also show that with the reduction in the tube length, the variations of principal frequency are enhanced. However, the frequency variation is insensitive to the nanotube diameter. As the number of vacancy defects increases, shift in the natural frequency also increases as expected. © 2008 IEEE.
