Journal of Computational Applied MechanicsJournal of Computational Applied Mechanics
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Feed provided by Journal of Computational Applied Mechanics. Click to visit.Transverse Sensing of Simply Supported Truncated Conical Shells
https://jcamech.ut.ac.ir/article_64204_8741.html
Modal signals of transverse sensing of truncated conical shells with simply supported boundary condition at both ends are investigated. The embedded piezoelectric layer on the surface of conical shell is used as sensors and output voltages of them in considered modes are calculated. The Governing sensing signal displacement equations are derived based on the Kirchhoff theory, thin-shell assumption, piezoelectric direct effect, the Gauss theory and the open circuit assumption. A conical shell with fully covered piezoelectric layer is considered as a case study and the layer is segmented into 400 patches. Modal voltages of the considered model are calculated and evaluated. The ideal locations for sensor patches are in the middle of conical shell surface in the longitudinal direction and locations near the ends of the conical shell are not recommended. The longitudinal membrane strain signal has a leading role on the total signal in comparison with other strain signal components. The output signals of the sensor can be used as a controller input for later active vibration control or structural health monitoring.Fri, 30 Nov 2018 20:30:00 +0100Investigation on Instability of Rayleigh-Benard Convection Using Lattice Boltzmann Method with ...
https://jcamech.ut.ac.ir/article_64208_8741.html
In this study, the effects of Prandtl number on the primary and secondary instability of the Rayleigh-Benard convection problem has been investigated using the lattice Boltzmann method. Two different cases as Pr=5.8 and 0.7 representing the fluid in liquid and gas conditions are examined. A body forces scheme of the lattice Boltzmann method was presented. Two types of boundary conditions in the presence of body forces are analyzed by the moment method and applied to a Poiseuille flow. Characteristic velocity was set in such a way that the compressibility effects are negligible. The calculations show that the increment of Prandtl number from 0.7 to 5.8 causes to create a secondary instability and onset of the oscillation in the flow field. Results show that at Pr=5.8, when the Rayleigh number is increased, a periodic solution appeared at Ra=48,000. It is observed that the dimensionless frequency ratio for Ra= 105 with Pr=5.8 is around 0.0065. The maximum Nusselt number for Ra = 105 with Pr=5.8 are estimated to be 5.4942.Fri, 30 Nov 2018 20:30:00 +0100Elasto-plastic solution for thick-walled spherical vessels with an inner FGM layer
https://jcamech.ut.ac.ir/article_63365_0.html
Purely elastic, partially and fully plastic stress states in a thick-walled spherical pressure vessel with an inner functionally graded material (FG) coating subjected to internal and external pressures are developed analytically in this paper. The modulus of elasticity and the uniaxial yield limit of the FG coating layer are considered to vary nonlinearly through the thickness. Using Tresca’s yield criterion and ideal plastic material behavior, the plastic model is established. Under pressure loading, the scenario in which the plastic deformation starts from inner surface of FG coating layer is taken into account. Having increased the pressure loading, it is assumed that the FG coating layer becomes fully plastic and the yielding commences subsequently at the inner surface of homogenous part. Essentially, the variation of FG parameters in the radial direction is properly adjusted in order to achieve the stated yielding scenario. Furthermore, axisymmetric finite element model is performed to validate the accuracy of the analytical results. It is concluded that the elastic and plastic response of the spherical pressure vessel are influenced by grading parameters and coating behavior.Mon, 09 Oct 2017 20:30:00 +0100The effect of boundary conditions on the accuracy and stability of the numerical solution of ...
https://jcamech.ut.ac.ir/article_68329_8741.html
The aim of this study is to investigate the effect of boundary conditions on the accuracy and stability of the numerical solution of fluid flows in the context of single relaxation time Lattice Boltzmann method (SRT-LBM). The fluid flows are simulated using regularized, no-slip, Zou-He and bounce back boundary conditions for straight surfaces in a lid driven cavity and the two-dimensional flow in a channel. The solutions for all types of the boundary conditions show good agreement with numerical references and exact solutions. The cavity pressure contours at low relaxation time show drastic perturbations for Zou-He boundary condition, whereas, the perturbation is ignorable for regularized boundary condition. At High Reynolds number, severe velocity gradients are major reason for numerical instabilities. Therefore, regularized boundary condition, which considers the velocity gradient in its calculation, has better numerical stability comparing the Zou-He boundary condition. Overall, the selection of appropriate boundary condition depends on the flow regime and Geometry. The proper boundary conditions at low Reynolds numbers are Zou-He and bounce back boundary conditions, and at high Reynolds numbers, regularized and no-slip boundary conditions are recommended.Fri, 30 Nov 2018 20:30:00 +0100Free Vibration Analysis of BNNT with Different Cross-Sections via Nonlocal FEM
https://jcamech.ut.ac.ir/article_68033_8741.html
In the present study, free vibration behaviors of of carbon nanotube (CNT) and boron nitride nanotube (BNNT) have been investigated via Eringen’s nonlocal continuum theory. Size effect has been considered via nonlocal continuum theory. Nanotubes have become popular in the world of science thanks to their characteristic properties. In this study, free vibrations of Boron Nitride Nanotube (BNNT) and Carbon Nanotube (CNT) are calculated using the Nonlocal Elasticity Theory. Frequency values are found via both analytical and finite element method (FEM). Galerkin weighted residual method is used to obtain the finite element equations. BNNT and CNT are modeled as Euler - Bernoulli Beam and solutions are gained by using four different cross-section geometries with three boundary conditions. Selected geometries are circle, rectangle, triangle, and square. Frequency values are given in tables and graphs. The effect of cross-section, boundary conditions and length scale parameter on frequencies has been investigated in detail for BNNT.Fri, 30 Nov 2018 20:30:00 +0100Nonlinear stability of rotating two superposed magnetized fluids with the technique of the ...
https://jcamech.ut.ac.ir/article_68655_8741.html
In the present work, the Rayleigh-Taylor instability of two rotating superposed magnetized fluids within the presence of a vertical or a horizontal magnetic flux has been investigated. The nonlinear theory is applied, by solving the equation of motion and uses the acceptable nonlinear boundary conditions. However, the nonlinear characteristic equation within the elevation parameter is obtained. This equation features a transcendental integro-Duffing kind. The homotopy perturbation technique has been applied by exploitation the parameter growth technique that results in constructing the nonlinear frequency. Stability conditions are derived from the frequency equation. It's illustrated that the rotation parameter plays a helpful result. It's shown that the stability behavior within the extremely uniform rotating fluids equivalents to the system while not rotation. A periodic solution for the elevation function has been performed. Numerical calculations area unit created for linear analysis furthermore the nonlinear scope. Moreover, the elevation function has been premeditated versus the time parameter. The strategy adopted here is vital and powerful for solving nonlinear generator systems with a really high nonlinearity arising in nonlinear science and engineering.Fri, 30 Nov 2018 20:30:00 +0100Heat Transfer Study of Convective-Radiative Fin under the influence of Magnetic Field using ...
https://jcamech.ut.ac.ir/article_64207_8741.html
The development and production of high performance equipment necessitate the use of passive cooling technology. In this paper, heat transfer study of convective-radiative straight fin with temperature-dependent thermal conductivity under the influence of magnetic field is carried out using Legendre wavelet collocation method. The numerical solution is used to investigate the effects of magnetic, convective and radiative parameters on the thermal performance of the fin. From the results, it is established that increase in magnetic, convective and radiative parameters increase the rate of heat transfer from the fin and consequently improve the thermal performance of the fin. The results obtained are compared with the results established results in literature and good agreements are found. The analysis can help in enhancing the understanding and analysis of the problem. Also, they can provide platform for improvement in the design of extended surfaces in heat transfer equipment under the influence of magnetic field.Fri, 30 Nov 2018 20:30:00 +0100Behavioral Optimization of Pseudo-Neutral Hole in Hyperelastic Membranes Using Functionally ...
https://jcamech.ut.ac.ir/article_68773_8741.html
Structures consisting of cables and membranes have been of interest to engineers due to their higher ratio of strength to weight and lower cost compared to other structures. One of the challenges in such structures is presence of holes in membranes, which leads to non-uniform stress and strain distributions, even under uniform far-field deformations. One of the approaches suggested for controlling this non-uniformity is reinforcing the hole edge using a cable, such that stretch changes near the hole are minimized compared to that of the far field in the membrane. In this study, considering an optimization problem, it is illustrated that for different geometries and stretch ratios in a biaxial loading of the membrane, a suitable cable of varying stiffness can be chosen such that stretch non-uniformity in the membrane is minimum, thus presenting a state of a pseudo-neutral hole in the membrane. The presented form of parametric functionally graded cable and the optimization problem solved for a couple of hole shapes show that the cable can induce a state of close to uniform stretch distribution for certain values of far field stretch ratios, it also proves effective for a range of such a ratio. Relative non-uniformity indices as low as 2 percent are achieved from optimization.Fri, 30 Nov 2018 20:30:00 +0100Prediction and optimization of load and torque in ring rolling process through development of ...
https://jcamech.ut.ac.ir/article_65485_8741.html
Developing artificial neural network (ANN), a model to make a correct prediction of required force and torque in ring rolling process is developed for the first time. Moreover, an optimal state of process for specific range of input parameters is obtained using Genetic Algorithm (GA) and Particle Swarm Optimization (PSO) methods. Radii of main roll and mandrel, rotational speed of main roll, pressing velocity of mandrel and blank size are considered as input parameters. Furthermore, the required load and torque in ring rolling process are taken into account as process outputs. Various three dimensional finite element simulations are performed for different sets of process variables to achieve preliminary data for training and validation of the neural network. Besides, the finite element model is approved via comparison with the experimental results of the other investigators. The Back Propagation (BP) algorithm is considered to develop Levenberg–Marquardt feed-forward network. Additionally, Model responses analysis is carried out to improve the understanding of the behavior of the ANN model. It is concluded that results of ANN predictions have an appropriate conformity with those from simulation and experiments. Moreover, GA and PSO methods have been implemented to obtain the optimal state of process while their outcomes have been also compared.Fri, 30 Nov 2018 20:30:00 +0100Longitudinal Magnetic Field Effect on Torsional Vibration of Carbon Nanotubes
https://jcamech.ut.ac.ir/article_68656_8741.html
Torsional dynamic analysis of carbon nanotubes under the effect of longitudinal magnetic field is carried out in the present study. Torque effect of an axial magnetic field on a carbon nanotube has been defined using Maxwell’s relation. Nonlocal governing equation and boundary conditions for carbon nanotubes are obtained by using Hamilton’s minimum energy principle. Eringen’s nonlocal stress gradient elasticity theory is used in the formulation. Fourth order nonlocal equation of motion is solved by utilizing differential quadrature method. Clamped-clamped and clamped-free nonlocal boundary conditions are considered. Nonlocal and axial magnetic field effects on torsional vibration of carbon nanotubes are investigated. The magnetic field has significant effects on the dynamics of carbon nanotubes and may lead to torsional buckling. Critical torsional buckling load reduces with nonlocal effects. Nonlocality shows softening effect on carbon nanotube’s lattice structure. Present results can be used in the design and analysis of nanoelectromechanical products like nano-motors.Fri, 30 Nov 2018 20:30:00 +0100Thermal simulation of two-phase flow in under-balanced drilling operation with oil and gas ...
https://jcamech.ut.ac.ir/article_65810_8741.html
The accurate prediction of wellbore temperature distribution helps to accurately estimate well pressure profile and bottom-hole pressure (BHP) which is important in the under-balanced drilling (UBD) operation. In this paper effect of temperature variation due to heat transfer of drilling fluid with the formation and also oil and gas production from the reservoir into the annulus in under-balanced drilling condition were investigated. Gas-liquid two-phase flow model considering thermal interaction with the formation is used to numerically simulate a well with real dimensions. Based on drilling fluids flow and heat transfer characteristics in wells, conservations of mass and momentum and energy equations have been developed to compute BHP and wellbore temperature and pressure profile. After temperature and pressure validation of the numerical model, the effect of heat transfer between drilling fluid inside the well and the formation was considered on the pressure distribution and bottom-hole pressure. The results of two-phase flow, considering thermal effect gives better results compared to two-phase flow with geothermal temperature distribution analysis and better accuracy in comparison with other models.Fri, 30 Nov 2018 20:30:00 +0100Evaluation of Thermo-mechanical stress in work rolls of ring rolling mill under thermal and ...
https://jcamech.ut.ac.ir/article_65484_8741.html
The defect in work rolls directly influence the forming cost and the final shape of the product. The researchers tend to investigate the thermo-mechanical stress in work roll of rolling machines. These stresses may reduce the roll life. Since the investigation of the thermo-mechanical stress in work roll with real-conditions is complex, comprehensive studies by means of numerical methods are available in numerous literature. However, simulating the thermo-mechanical stress is time-consuming. So, most researchers desire to simplify the geometry and boundary conditions in order to reduce simulation cost. This paper proposes an integrated finite element model to study the thermo-mechanical behavior of work rolls during hot ring rolling process. Various methods were simulated and advantages and disadvantages of each method were discussed. Due to complexities of ring rolling process, the presented model was used in flat rolling in order to verify model integrity. After that work rolls of ring rolling mill subjected to partial boundary conditions are investigated. The results of thermal and thermo-mechanical simulations show stresses in the contact region of work rolls are rather different. However, they expressed the same results in other regions. Based on the obtained results, it is revealed that the effect of mechanical loads in the equivalent stresses should be considered and the location of equivalent maximum stress is below the surface.Fri, 30 Nov 2018 20:30:00 +0100A two dimensional Simulation of crack propagation using Adaptive Finite Element Analysis
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Finite element method (FEM) is one of the most famous methods which has many applications in varies studies such as the study of crack propagation in engineering structures. However, unless extremely fine meshes are employed, problem arises in accurately modelling the singular stress field in the singular element area around the crack tip. In the present study, the crack growth simulation has been numerically simulated by using the dens mesh finite element source code program using Visual FORTRAN language. This code includes the mesh generator based on the advancing front method as well as all the pre and post process for the crack growth simulation under linear elastic fracture mechanics theory. The stress state at a crack tip has been described by the stress intensity factor which is related to the rate of crack growth. The displacement extrapolation technique is employed to obtain crack tip singular stresses and the stress intensity factors values. The crack direction is predicted using the maximum circumferential theory. Verification of the predicted stress intensity factors and crack path direction are validated with relevant experimental data and numerical results obtained by other researchers with good agreements.Fri, 30 Nov 2018 20:30:00 +0100ON MAXWELL'S STRESS FUNCTIONS FOR SOLVING THREE DIMENSIONAL ELASTICITY PROBLEMS IN THE THEORY ...
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The governing equations of three dimensional elasticity problems include the six Beltrami-Michell stress compatibility equations, the three differential equations of equilibrium, and the six material constitutive relations; and these are usually solved subject to the boundary conditions. The system of fifteen differential equations is usually difficult to solve, and simplified methods are usually used to achieve a solution. Stress-based formulation and displacement-based formulation methods are two common simplified methods for solving elasticity problems.This work adopted a stress-based formulation for a three dimensional elasticity problem. In this work, the Maxwell's stress functions for solving three dimensional problems of elasticity theory were derived from fundamental principles. It was shown that the three Maxwell stress functions identically satisfy all the three differential equations of static equilibrium when body forces were ignored. It was further shown that the three Maxwell stress functions are solutions to the six Beltrami-Michell stress compatibility equations if the Maxwell stress functions are potential functions. It was also shown that the Airy's stress functions for two dimensional elasticity problems are special cases of the Maxwell stress functions.Fri, 30 Nov 2018 20:30:00 +0100Investigation of energy consumption reduction in multistage compression process and its solutions
https://jcamech.ut.ac.ir/article_64489_0.html
During hot seasons the inlet temperature of Nitrogen increases, as a result compressor consumes more power for compressing a specific mass ratio of fluid and consequently total energy consumption of the compressor increases as well. In this research, a three stage centrifugal compressor with intercooler was modeled thermodynamically in order to decreases the energy consumption of the compressor. In each compressor, isentropic efficiency, outlet temperature of the Nitrogen gas and power compression was investigated. The effect of inlet Nitrogen temperature and cooling water temperature on intercoolers’ efficiency were investigated. In this study, Nitrogen gas is considered as an ideal gas. It is found that, in each compressor any growth in inlet temperature of the Nitrogen gas will result in linear increase in the outlet temperature of the Nitrogen gas and power compression furthermore, it is observed that increasing the temperature of Nitrogen gas has the most negative effect on efficiency and power compression of the first compressor in comparison to the second and the third compressor consequently, it will result in a 10 percent decrease in special power compression specially during summer time. According to the results, it is figured out that any growth in inlet Nitrogen temperature causes a smooth decline in isentropic and Power Compression of the first, second and third compressors besides increasing the temperature of the Nitrogen gas increases the isentropic efficiency up to 3 Percent and increasing the cooling water temperature decreases the intercooler efficiency up to 7 Percent.Mon, 08 Jan 2018 20:30:00 +0100Internal heat source in a temperature dependent thermoelastic half space with microtemperatures
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A two dimensional deformation due to internal heat source in a thermoelastic solid with microtemperatures under the dependence of modulus of elasticity and thermal conductivity on reference temperature has been studied. A mechanical force of constant magnitude is applied at the free surface of thermoelastic half space. The normal modes technique has been applied to obtain the exact expressions for the components of normal displacement, microtemperature, normal force stress, temperature distribution, heat flux moment tensor and tangential couple stress for thermoelastic solid with microtemperatures. The effect of internal heat source, thermal conductivity and microrotation on the derived components have been derived analytically. The graphical results are shown in the presence and absence of thermal conductivity and microrotation to show the appreciable effect of rotation and temperature on the quantities. The problem may also be extended to show the effect of different types of mechanical and thermal sources applied in the medium.Fri, 30 Nov 2018 20:30:00 +0100Modelling of the Dynamics of an immersed body in a microchannel with stenosis using the ...
https://jcamech.ut.ac.ir/article_64549_0.html
In the present study, the combination of lattice Boltzmann and immersed boundary methods is used to simulate the motion and deformation of a flexible body. Deformation of the body is studied in microchannel with stenosis and the effect of the flexibility changes on its deformation is investigated. The obtained results in the present manuscript show that by increasing the elasticity modulus, the deformation of the body and its speed decrease. In this case, the flow pressure around the body increase. When the body is initially located outside the microchannel center, tank-treading motion occurs due to the difference in velocity of the shear layers. In addition, with a decrease in the size of microchannel stenosis, the body is less deformed and goes faster and reaches to the end of the microchannel in less time. The faster or slower movement of the biological membranes than the normal state causes the proper exchange of materials between the membrane wall and the surrounding flow and that disturbs its most important duty i.e. the exchange of materials with tissues. The analysis in this study shows that the results of the simulation are in good agreement with the available results and demonstrates the efficiency of the combination of lattice Boltzmann and immersed boundary methods to simulate the dynamic behavior of biological membranes, red blood cells and deformable particles inside the flow.Wed, 10 Jan 2018 20:30:00 +0100Impeller and volute design and optimization of the centrifugal pump with low specific speed in ...
https://jcamech.ut.ac.ir/article_64656_8741.html
Now a day centrifugal pumps are vital components of industries. Certainly, one of the most important specifications of centrifugal pumps are the performance curves. In the present work, performance curves of a centrifugal pumps are obtained by Computational fluid dynamics (CFD) and as an outcome, CFD results compare by practical curves. At the first step impeller and volute are designed with two standards and at the end former design completed by automatic design process using CFturbo software. For this purpose, full 3D-RANS equations in coupled with SST turbulence model are solved for several flow rate between 20% and 140% of the operation condition by means of a commercial code, CFX. This simulation is defined by means of the multi-reference frame technique in which the impeller is situated in the rotating reference frame, and the volute is in the fixed reference frame. Proposed simulation is based on a steady state flow, non-Newtonian, incompressible and constant property condition. Operation point is simulated to get the total head and then non-operation points are simulated to obtain performance curves. Practical curves and numerical ones are in good agreement, so numerical approach could be a perfect way to make centrifugal pump design better and easier. Indeed pump simulation with CFD approach can increase our knowledge about pump behavior such as consumption energy, trimming process and saving energy before we have any activities on the pump so the predictions have bettering and excise about any process on the pump.Fri, 30 Nov 2018 20:30:00 +0100Fatigue and Anisotropic behaviours of cold rolled AA1200 Aluminium Alloy
https://jcamech.ut.ac.ir/article_65822_8741.html
This study examines the fatigue and anisotropy behaviour of cold rolled AA1200 aluminium alloy for light weight automotive connecting rod application. Aluminium (Al) 1200 ingots were melted at temperature of 680 0C (after one hour of heating) cast in sand mould and cast samples homogenized for 6 hrs at 480 0C. The cold rolling process was carried out after homogenisation for 10, 20, 30, 40 and 50% thickness reductions. The samples were characterised in 00, 150, 300, 450, 600, 750 and 900 to the rolling direction. The results show that degree of deformation increase linearly with mean stress, stress range, stress ratio, stress amplitude, thickness and area ratio for all the reductions and directions examined. Area and thickness ratio increases linearly with deformation at higher inclination (> 150). The fatigue life obtained in this work shows life cycles at different degrees of deformation: 7.5 x 104 cycles at 10% reduction, 1.3 x105 cycles at 20% reduction, 4.3 x 104 cycles at 30% reduction; 2.6 x 105 cycles at 40% reduction and 1.09 x 105 cycles at 50% reduction). The results of this study provide evidence that systemic controlled cold deformation can potentially be used to significantly enhance the fatigue life of AA1200 aluminium alloy components subjected to cyclic loadings.Fri, 30 Nov 2018 20:30:00 +0100Effects of Casting Speed and Runner Angle on Macrosegregation of Aluminium-Copper Alloy.
https://jcamech.ut.ac.ir/article_66042_8741.html
Abstract During the solidification of binary metal alloys, chemical heterogeneities at product scale over a long distance range (1cm-1m) develop and this has detrimental effect on the resulting mechanical properties of cast products. Macrosegregation is of great concern to alloy manufacturers and end users as this problem persist. In this study, the use of process parameters namely casting speed and runner angle to reduce macro-segregation in aluminum-copper-zinc binary alloy solidification is reported. The results from optical microscope, scanning electron microscope and energy dispersive spectrometry show that these parameters significantly influenced the development, size and volume of macro-segregation. The combination of parameters namely the pouring height between 96 mm/s, 100mm/s, and runner angles between 1200, 1500 produced less segregations with improved mechanical properties within standard specification. The tensile strength (110 MPa), modulus of elasticity (6800 MPa) and 2.5 % elongation obtained in this study are within standard (88- 124 MPa), 7100 MPa and (1-25 %) respectively for this class of alloy.Fri, 30 Nov 2018 20:30:00 +0100Finite Element Investigation and comparing different models of wrist prosthesis
https://jcamech.ut.ac.ir/article_64655_0.html
Joint replacement surgery in the wrist is less common than other replacement, but can be an option if you have painful arthritis that does not respond to other treatments. In wrist joint replacement surgery, the damaged parts of the wrist bones are removed and replaced with artificial components, called a wrist prosthesis. If the cartilage is worn away or damaged by injury, infection, or disease, the bones themselves will rub against each other, wearing out the ends of the bones. This causes a painful, arthritic condition. Osteoarthritis, the most common form of arthritis, results from a gradual wearing away of the cartilage covering on bones. Rheumatoid arthritis is a chronic inflammatory disease of the joints that results in pain, stiffness and swelling. Rheumatoid arthritis usually affects several joints on both the right and left sides of the body. Both forms of arthritis may affect the strength of the fingers and hand, making it difficult to grip or pinch.Wed, 17 Jan 2018 20:30:00 +0100Dynamic behaviour of concrete containing aggregate resonant frequency
https://jcamech.ut.ac.ir/article_68967_8741.html
The need to design blast resistant civilian structures has arisen due to aggressor attacks on many civilian structures around the world. Achieving vibration and wave attenuation with locally resonant metamaterials has attracted a great deal of consideration due to their frequency dependent negative effective mass density. In this paper, metaconcrete, a new material with exceptional properties is formed. The aggregates in concrete are substituted with spherical inclusions consisting of a heavy metal core coated with a soft outer layer. The physics of the metamaterial was first established, and mass in mass-spring and effective mass system were shown to be equivalent. Then the engineered aggregate was tuned so that band gap was activated due to resonant oscillations of the replaced aggregate. In the numerical experiment conducted, the resonant behaviour causes the wave to be forbidden in the targeted frequencies. The proposed metaconcrete could be very useful in various civil engineering applications where vibration suspension and wave attenuation ability are in high demand.Fri, 30 Nov 2018 20:30:00 +0100Magneto-mechanical Stimulation of Bone Marrow Mesenchymal Stromal Cells for Chondrogenic ...
https://jcamech.ut.ac.ir/article_68968_8741.html
Mechanical interaction of cells and their surroundings are prominent in mechanically active tissues such as cartilage. Chondrocytes regulate their growth, matrix synthesis, metabolism, and differentiation in response to mechanical loadings. Cells sense and respond to applied physical forces through mechanosensors such as integrin receptors. Herein, we examine the role of mechanical stimulation of integrins in regards to their mechanotransduction ability to promote chondrogenesis. For this purpose, magnetic nanoparticles were chemically bonded to cell membrane mechanoreceptors and stimulated. Histological results showed the endocytosis of nanoparticles over the experimental period, pointing out the inefficient mechanical stimulation of the mechanoreceptors. Moreover, gene expression analysis only showed significant upregulation for SOX9, whereas type II collagen and aggrecan gene expression were not significantly different from the control group. Our results suggest that magneto-mechanical stimulation studies using magnetic nanoparticles should not only focus on the mechanical aspects, but also the interaction of magnetic nanoparticles with intracellular machinery should be investigated as well.Fri, 30 Nov 2018 20:30:00 +0100Comparison between the frequencies of FML and composite cylindrical shells using beam modal ...
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A comparison between the vibration of fiber-metal laminate (FML) and composite cylindrical shells has been studied in this manuscript. Love’s first approximation shell theory has been applied to obtain Strain-displacement relations. In addition, beam modal function model has been used to analyze the cylindrical shell with different boundary conditions. In this manuscript, the frequencies of FML and composite cylindrical shells have been compared to each other for different materials, lay-ups, boundary conditions, axial and circumferential wave numbers. The most commercially available FMLs are CARALL (carbon reinforced aluminium laminate), and GLARE (glass reinforced aluminium laminate), which are studied in this research. The results showed although the frequencies of carbon/epoxy are greater than glass/epoxy for all of the n, this process is not constant for FML. Also, with increasing the n, the frequencies of FML cylindrical shells are converged more faster than the composite one. Moreover, the frequencies of both boundary conditions are converged with increasing n for both FML and composite cylindrical shells.Wed, 17 Jan 2018 20:30:00 +0100Magneto-Thermo mechanical vibration analysis of FG nanoplate embedded on Visco Pasternak foundation
https://jcamech.ut.ac.ir/article_69009_8741.html
In this study, the vibration behavior of functional graded (FG) circular and annular nanoplate embedded in Visco-Pasternak foundation and coupled with temperature change is studied. It is assumed that a uniform radial magnetic field acts on the top surface of the plate and the magnetic permeability coefficient of the plate along its thickness are assumed to vary according to the volume distribution function. The effect of in-plane pre-load and temperature change are investigated on the vibration frequencies of FG nanoplate. The FG nanoplate is coupled by an enclosing viscoelastic medium which is simulated as a Visco- Pasternak foundation. By using the modified strain gradient theory (MSGT) and the modified couple stress theory (MCST), the governing equation is derived for FG circular and annular nanoplate. The DQM and the Galerkin method are utilized to solve the governing equation to obtain the frequency vibration. The effects of the size dependent, the in-plane pre-load, the temperature change, the magnetic field, the power index parameter, the elastic medium and the boundary conditions on the natural frequencies are investigated. The temperature change plays an important role in the mechanical behavior of the FG circular and annular nanoplate. According to the results, the application of radial magnetic field to the top surface of the plate changes the state of stress in both tangential and radial direction. The present analysis results can be used for the design of the next generation of nano-devices that make use of the thermal vibration properties of the nanoplate.Fri, 30 Nov 2018 20:30:00 +0100Modified mathematical model for variable fill fluid coupling
https://jcamech.ut.ac.ir/article_69047_8741.html
Variable fill fluid couplings are used in the speed control units. Also, variation in coupling oil volume is used in adapting one size of coupling to a wider range of power transmission applications. Available model for the partially filled fluid couplings, has a good performance for couplings with fixed amount of oil but their performance will be degraded if they are used for the variable fill couplings. In this paper, the current model for partially filled fluid couplings is modified to have better performance for variable fill couplings. For this purpose, the circulation loss calculation is modified and also, the effect of oil temperature variations and blade thickness are included in the model. The effect of these modification on the model performance are investigated in couple of simulations. Comparing the simulation results with the available experimental data shows that the suggested modifications can improve the model performance very well.Fri, 30 Nov 2018 20:30:00 +0100A review on stress distribution, strength and failure of bolted composite joints
https://jcamech.ut.ac.ir/article_69010_8741.html
In this study, analytical models considering different material and geometry for ‎both single and double-lap bolted joints were reviewed for better understand how to ‎select the proper model for a particular application. The survey indicades that the ‎analytic models selected for the adhesively single or double bolted lap joints, as well ‎as T, scarf, and stepped joints, with linear material properties are mostly two ‎dimensional and the studies on stress distribution and/or failure of the joint are ‎performed either experimentally, analytically or by finite element method. The results ‎seem to be generally accurate and adequate. Additionally, it was shown that any ‎increase in the bolt-hole clearance leads to an increase in bolt rotation, as well as a ‎decrease in bolt-hole contact area, and hence, a reduction in joint stiffness. Moreover, ‎studies on hybrid joints have revealed that the proper choice of adhesive material in ‎conjunction with bolts or rivets in a joint, allows for significant increase in the static ‎and fatigue strength compared to similar pure bonded joints. Additionally, the results ‎on hybrid scarf joints showed that it is vital to place fasteners closer to the ends of the ‎overlap to suppress the peak peeling stresses and hence, delay the effects of early ‎crack initiation in the adhesive layer...Fri, 30 Nov 2018 20:30:00 +0100Numerical simulation of the effect of particle size on the erosion damage in ball valves of ...
https://jcamech.ut.ac.ir/article_64776_0.html
Ball valve is one of valves that have many applications in industry especially in gas delivery systems. This kind of valve is categorized in the on - off flow control valve. This study aims to investigate unusual application of ball valve to control fluid flow in industry and its destructive effect including erosion of ball and body of valve. Simulation of industrial ball valve is done using ANSYS Fluent software and effect of erosion on it is investigated in different working conditions. In this article, working condition is performed regarding 2 different concentrations for suspended particles as well as four positions of ball in different angles. We assess the effect of increased particle diameter on the rate of erosion for three diameters (3.86e-6 m , 267.45e-6 m and 531.03e-6 m) in four conditions of valve (25%, 50%, 75% and 100%) and two different concentrations of particle (3% and 6%). It is shown that rate of erosion is increased with increased particle diameters in 25%, 50% and 75% open state of valve. On the contrary, the results show that opposite rule governs complete open state. Furthermore, it is demonstrated that increase in particle diameter decreases the area of erosion in four conditions of valve.Fri, 26 Jan 2018 20:30:00 +0100Size-dependent on vibration and flexural sensitivity of atomic force microscope
https://jcamech.ut.ac.ir/article_65215_0.html
In this paper, the free vibration behaviors and the flexural sensitivity of atomic force microscope cantilevers with small-scale effects are investigated. To study the small-scale effects on natural frequencies and flexural sensitivity, the consistent couple stress theory is applied. In this theory, the couple stress is assumed skew-symmetric. Unlike the classical beam theory, the new model contains a material-length-scale parameter and can capture the size effect. For this purpose, the Euler–Bernoulli beam theory is used to develop the AFM cantilever. The tip interacts with the sample that is modeled by a spring with constant of k. The equation of motion is obtained through a variational formulation based on Hamilton’s principle. In addition, the analytical expressions for the natural frequency and sensitivity are also derived. At the end, some numerical results are selected to study the effects of material-length scale parameter and dimensionless thickness on the natural frequency and flexural sensitivity.Thu, 15 Feb 2018 20:30:00 +0100Numerical Simulation of the Effect of Valve Opening and Particle Concentration on the Erosion ...
https://jcamech.ut.ac.ir/article_65701_0.html
Ball valve is one of valves that have many applications in industry especially in gas delivery systems. This kind of valve is categorized in the on- off flow control valve. This study aims to investigate unusual application of ball valve to control fluid flow in the oil and gas industry and its destructive effect including erosion of ball and body of valve. Simulation of industrial ball valve is done using ANSYS Fluent software and effect of erosion on it is investigated in different working conditions. In this study, working condition is performed regarding 3 different concentrations for suspended particles as well as four positions of ball in different angles. It is shown that rate of erosion for 25% open state of valve is increased to about 15000 times of complete open state of valve, and rate of erosion is increased to about 3500 times for half open state (50% open state); and rate of erosion is increased to about 220 times for 75% open state of valve.Tue, 24 Apr 2018 19:30:00 +0100Hydrodynamic investigation of multiple rising bubbles using lattice Boltzmann method
https://jcamech.ut.ac.ir/article_65702_0.html
Hydrodynamics of multiple rising bubbles as a fundamental two-phase phenomenon is studied numerically by lattice Boltzmann method and using Lee two-phase model. Lee model based on Cahn-Hilliard diffuse interface approach uses potential form of intermolecular forces and isotropic finite difference discretization. This approach is able to avoid parasitic currents and leads to a stable procedure to simulate two-phase flows. Deformation and coalescence of bubbles depend on a balance between surface tension forces, gravity forces, inertia forces and viscous forces. A simulation code is developed and validated by analysis of some basic problems such as bubble relaxation, merging bubbles, merging droplets and single rising bubble. Also, the results of two rising bubbles as the simplest interaction problem of rising bubbles have been calculated and presented. As the main results, square and lozenge initial configuration of nine rising bubbles are studied at Eotvos numbers of 2, 10 and 50. Two-phase flow behavior of multiple rising bubbles at same configurations is discussed and the effect of Eotvos number is also presented. Finally, velocity field of nine rising bubbles is presented and discussed with details.Tue, 24 Apr 2018 19:30:00 +0100Solving Single Phase Fluid Flow Instability Equations Using Chebyshev Tau- QZ Polynomial
https://jcamech.ut.ac.ir/article_65771_0.html
In this article the instability of single phase flow in a circular pipe from laminar to turbulence regime has been investigated. To this end, after finding boundary conditions and equation related to instability of flow in cylindrical coordination system, which is called eigenvalue Orr Sommerfeld equation, the solution method for these equation has been investigated. In this article Chebyshev polynomial Tau-QZ algorithm has been selected for the solution technique to solve the Orr Sommerfeld equation because in this method some of complex terms in the instability equation in cylindrical coordination will be appeared. After finding Orr Sommerfeld parameters related to Chebyshev polynomial Tau-QZ algorithm the solution have been done for Re=5000 and Re=1000, then the results had been compared with the results of valid references where other methods had been used in them. It have been observed that the use of Chebyshev Tau-QZ algorithm has higher accuracy concerning the results and it also has a higher accurate technique to solve the Orr Sommerfeld instability equations in cylindrical coordination system.Fri, 27 Apr 2018 19:30:00 +0100Attractor Based Analysis of Centrally Cracked Plate Subjected to Chaotic Excitation
https://jcamech.ut.ac.ir/article_66038_0.html
The presence of part-through cracks with limited length is one of the prevalent defects in the plate structures. Due to the slight effect of this type of damages on the frequency response of the plates, conventional vibration-based damage assessment could be a challenging task. In this study for the first time, a recently developed state-space method which is based on the chaotic excitation is implemented and nonlinear prediction error (NPE) is proposed as a geometrical feature to analyze the chaotic attractor of a centrally cracked plate. For this purpose using line spring method (LSM) a nonlinear multi-degree of freedom model of part through cracked rectangular plate is developed. Tuning of Lorenz type chaotic signal is conducted by crossing of the Lyapunov exponents’ spectrums of nonlinear model of the plate and chaotic signal and in the next step by varying the tuning parameter to find a span in which a tangible sensitivity in the NPE could be observable. Damage characteristics such as length, depth and angle of crack are altered and variation of proposed feature is scrutinized. Results show that by implementation of the tuned chaotic signal, tangible sensitivity and also near to monotonic behavior of NPE versus damage intensity are achievable. Finally, the superiority of the proposed method is examined through the comparison with the frequency-based method.Thu, 22 Feb 2018 20:30:00 +0100A wave-based computational method for free vibration and buckling analysis of rectangular Reddy ...
https://jcamech.ut.ac.ir/article_66040_0.html
In this paper, the wave propagation method is combined with nonlocal elasticity theory to analyze the buckling and free vibration of rectangular Reddy nanoplate. Wave propagation is one of the powerful methods for analyzing the vibration and buckling of structures. It is assumed that the plate has two opposite edges simply supported while the other two edges may be simply supported or clamped. It is the first time that the wave propagation method is used for thick nanoplates. In this study, firstly the matrices of propagation and reflection are derived. Then, these matrices are combined to provide an exact method for obtaining the natural frequencies and critical buckling loads which can be useful for future studies. It is observed that obtained results of the wave propagation method are in good agreement with the obtained values by literature. At the end the obtained results are presented to evaluate the influence of different parameters such as nonlocal parameter, aspect ratio and thickness to length ratio of nanoplate.Tue, 22 May 2018 19:30:00 +0100Minimization of Entransy Dissipations of a Finned Shell and Tube Heat Exchanger
https://jcamech.ut.ac.ir/article_66041_0.html
Improving heat transfer and performance in a radial, finned, shell and tube heat exchanger is studied in this study. According to the second law of thermodynamics, the most irreversibilities of convective heat transfer processes are due to fluid friction and heat transfer via finite temperature difference. Entransy dissipations are due to the irreversibilities of convective heat transfer. Therefore, the number of entrancy dissipation is considered as the optimization objective. Thirteen optimization variables are considered, such as the number of tubes, tube diameter, tube length, fin height, fin thickness, the number of fins per inch length of tube and baffle spacing ratio. The “Delaware modified” technique is used to determine heat transfer coefficients and the shell-side pressure drop. In this technique, the baffle cut is 20 percent. The results show that using genetic algorithm the optimization can be improve the heat transfer by 13 percent and performance of heat exchanger increased by 18 percent. In order to show the accuracy of the algorithm the results compared to the particle swarm optimization.Tue, 22 May 2018 19:30:00 +0100Static and dynamic axial crushing of prismatic thin-walled metal columns
https://jcamech.ut.ac.ir/article_67381_0.html
In this paper, a novel approach is proposed to investigate the progressive collapse damage of prismatic thin walled metal columns with different regular cross sections, under the action of axial quasi-static and impact loads. The present work mainly focuses on implementation of some important factors which have been neglected in other studies. These factors include the effect of reducing impactor velocity and inertia effect during collapse, a mixed collapse mode for crushing mechanism, and consideration of a realistic elasto-plastic model for material. Taking all these factors into account, the analysis led to some parametric algebraic equations without a possible general solution in terms of collapse variables. Consequently, a new theoretical approach was proposed based on previously offered Super Folding Element (SFE) theory, to obtain the closed form explicit relations for the static and dynamic mean crushing forces and collapse variables. The proposed approach considers an analytic-numeric discretization procedure to solve these equations. To evaluate the results, a detailed finite element analysis on square mild steel models was conducted under an axial impact load, using LS-DYNA and ANSYS software programs. Comparison of the experimental results that are available in the literature with those of finite element analysis, shows the applicability of this approach in predicting the collapse behavior in such structures.Sun, 02 Sep 2018 19:30:00 +0100A preconditioned solver for sharp resolution of multiphase flows at all Mach numbers
https://jcamech.ut.ac.ir/article_68327_0.html
A preconditioned five-equation two-phase model coupled with an interface sharpening technique is introduced for simulation of a wide range of multiphase flows with both high and low Mach regimes. Harten-Lax-van Leer-Contact (HLLC) Riemann solver is implemented for solving the discretized equations while tangent of hyperbola for interface capturing (THINC) interface sharpening method is applied to reduce the excessive diffusion of the method at the interface. In this work, preconditioning technique is used in a system of equations including viscous and capillary effects. Several one- and two-dimensional test cases are used to evaluate the performance and accuracy of this method. Numerical results demonstrate the efficiency of preconditioning in low Mach number flows. Comparisons between results of preconditioned and conventional system highlight the necessity of using preconditioning technique to reproduce main characteristics of low-speed flow regimes. Additionally, preconditioned systems transform to the conventional systems at high Mach number flows thus exhibiting the same level of accuracy as the standard flow solver. Therefore, the preconditioned compressible two-phase method can be used as an all-speed two-phase flow solver accounting for capillary and viscous stresses.Tue, 13 Nov 2018 20:30:00 +0100Micro-cantilevered MEMS Biosensor for Detection of Malaria Protozoan Parasites
https://jcamech.ut.ac.ir/article_69964_0.html
In this paper, the presented work aims to provide a designed model based on Finite element method for detection of Malaria protozoan parasites. Micro-cantilevers are next generation highly efficient biosensors for detection and prevention of any disease. Here, an E-shaped model for micro cantilevered biosensor is designed using COMSOL Multiphysics specifically for detection of Malaria. Microcantilever materials viz Au, Cu, Si and Pt are used for sensing Malaria protozoan with proper optimization of device structure. The studies were carried out for stress developed and displacement occurred due to force applied through these protozoan biomolecules and varying beam length. Further, the designed structure was analyzed for different beam materials available for biosensor and it was found that Au is best suitable material for detection of malaria protozoan parasites since it has best sensitivity profile among presented materials. The results were also verified through analytical approach and it was found that both results obtained through simulation and analytical methods do closely agree with each other.Sat, 23 Feb 2019 20:30:00 +0100Rotating magneto-thermoelastic rod with finite length due to moving heat sources via ...
https://jcamech.ut.ac.ir/article_69970_0.html
The article is concerned with a new nonlocal model based on Eringen’s nonlocal elasticity and generalized thermoelasticity. A study is made of the magneto-thermoelastic waves in an isotropic conducting thermoelastic finite rod subjected to moving heat sources permeated by a primary uniform magnetic field and rotating with a uniform angular velocity. The Laplace transform technique with respect to time is utilized. The inverse transforms to the physical domain are obtained in a numerical manner for the nonlocal thermal stress, temperature, and displacement distributions. Finally, some graphical presentations have been made to assess the effects of various parameters; nonlocal parameter, rotating, applied magnetic field as well as the speed of the heat source on the field variables. The results obtained in this work should be useful for researchers in nonlocal material science, low-temperature physicists, new materials designers, as well as to those who are working on the development of the theory of nonlocal thermoelasticity.Tue, 26 Feb 2019 20:30:00 +0100Dynamical stability of cantilevered pipe conveying fluid in the presence of linear dynamic ...
https://jcamech.ut.ac.ir/article_69971_0.html
When the velocity of fluid flow in a cantilevered pipe is successively increased, the system may become unstable and flutter instability would occur at a critical flow velocity. This paper is concerned with exploring the dynamical stability of a cantilevered fluid-conveying pipe with an additional linear dynamic vibration absorber (DVA) attachment. It is endeavoured to show that the stability of the pipe may be considerably enhanced due to the presence of DVA. The quasi-analytical results show that the energy transferred from the flowing fluid to the pipe may be partially transferred to the additional mass. In most cases, thus, the critical flow velocity at which the pipe becomes unstable would become larger, meanwhile the flutter instability of the DVA is not easy to achieve. In such a fluid-structure interaction system, it is also found that flutter instability may first occur in the mode of the DVA. The effects of damping coefficient, weight, location and spring stiffness of the DVA on the critical flow velocities and nonlinear oscillations of the system have also been analyzed.Tue, 26 Feb 2019 20:30:00 +0100Vibration of FG viscoelastic nanobeams due to a periodic heat flux via fractional derivative model
https://jcamech.ut.ac.ir/article_70476_0.html
In this work, the vibrations of viscoelastic functionally graded Euler–Bernoulli nanostructure beams are investigated using the fractional-order calculus. It is assumed that the functionally graded nanobeam (FGN) is due to a periodic heat flux. FGN can be considered as nonhomogenous composite structures; with continuous structural changes along the thick- ness of the nanobeam usually, it changes from ceramic at the bottom of the metal at the top. Based on the nonlocal model of Eringen, the complete analytical solution to the problem is established using the Laplace transform method. The effects of different parameters are illustrated graphically and discussed. The effects of fractional order, damping coefficient, and periodic frequency of the vibrational behavior of nanobeam was investigated and discussed. It also provides a conceptual idea of the FGN and its distinct advantages compared to other engineering materials. The results obtained in this work can be applied to identify of many nano-structures such as nano-electro mechanical systems (NEMS), nano-actuators, etc.Sat, 16 Mar 2019 20:30:00 +0100Nonlocal thermoelastic semi-infinite medium with variable thermal conductivity due to a laser ...
https://jcamech.ut.ac.ir/article_70477_0.html
In this article, the thermoelastic interactions in an isotropic and homogeneous semi-infinite medium with variable thermal conductivity caused by an ultrashort pulsed laser heating based on linear nonlocal theory of elasticity has been considered. We consider that the thermal conductivity of the material is dependent on the temperature. The surface of the surrounding plane of the medium is heated by an ultrashort pulse laser. Basic equations are solved along with the corresponding boundary conditions numerically by means of the Laplace transform technique. The influences of the rise time of the laser pulse, as well as nonlocal parameter on thermoelastic wave propagation in the medium, have also been investigated in detail. Presented numerical results, graphs and discussions in this work lead to some important deductions. The results obtained here will be useful for researchers in nonlocal material science, low-temperature physicists, new materials designers, as well as to those who are working on the development of the theory of nonlocal thermoelasticity.Sat, 13 Apr 2019 19:30:00 +0100Usage of the Variational Iteration Technique for Solving Fredholm Integro-Differential Equations
https://jcamech.ut.ac.ir/article_70478_0.html
Integral and integro-differential equations are one of the most useful mathematical tools in both pure and applied mathematics. In this article, we present a variational iteration method for solving Fredholm integro-differential equations. This study provides an analytical approximation to determine the behavior of the solution. To show the efficiency of the present method for our problems in comparison with the exact solution we report the absolute error. From the computational viewpoint, the variational iteration method is more efficient, convenient and easy to use. The method is very powerful and efficient in nding analytical as well as numerical solutions for wide classes of linear and nonlinear Fredholm integro-differential equations. Moreover, It proves the existence and uniqueness results and convergence of the solution of Fredholm integro-differential equations. Finally, some examples are included to demonstrate the validity and applicability of the proposed technique. The convergence theorem and the numerical results establish the precision and efficiency of the proposed technique.Wed, 27 Feb 2019 20:30:00 +0100Influence of taxol and CNTs on the stability analysis of protein microtubules
https://jcamech.ut.ac.ir/article_70479_0.html
Microtubules are used as targets for anticancer drugs due to their crucial role in the process of mitosis. Recent studies show that carbon nanotubes (CNTs) can be classified as microtubule-stabilizing agents as they interact with protein microtubules (MTs), leading to interference in the mitosis process. CNTs hold a substantial promising application in cancer therapy in conjunction with other cancer treatments such as radiotherapy and chemotherapy. In the current study, a size-dependent model is developed for the stability analysis of CNT-stabilized microtubules under radial and axial loads. A nonlocal shell theory with strain gradient effects is employed to take size influences into account. Moreover, Van der Waals interactions between CNTs and MTs are simulated. An excellent agreement is observed between the present model and reported data from experiments on protein MTs. In addition, the effects of taxol, as another stabilizing agent, on the stability of microtubules are studied. It is found that both nonlocal and strain gradient effects are essential to accurately obtain the stability capacity of MTs. Furthermore, CNTs have an increasing effect on the critical loads of microtubules while the critical loads reduce in the presence of taxol.Fri, 15 Mar 2019 20:30:00 +0100Design, Evaluation and Prototyping of a New Robotic Mechanism for Ultrasound Imaging
https://jcamech.ut.ac.ir/article_70504_0.html
This paper presents a new robotic mechanism for ultrasound imaging. The device is placed on a patient's body by an operator, and an ultrasound expert controls the motions of the device to obtain ultrasound images. The paper focuses on the robotic mechanism that performs ultrasound imaging. The design of the mechanism is based on two approaches to produce center of motion for an ultrasound probe. This center of motion which is located on the tip of the ultrasound probe helps to create clear ultrasound images. Detailed designs, kinematic relationships, prototyping and ultrasound imaging tests are presented. A novel cabling mechanism is developed to create the center of motion required for ultrasound imaging. The mechanism provides all four necessary motions for ultrasound imaging by using two actuators which significantly reduces the weight of the device to make it suitable for portable ultrasound applications. The device has been successfully used for ultrasound imaging of kidney, gallbladder, liver, ovary and uterus of volunteer patients.Sun, 07 Apr 2019 19:30:00 +0100Numerical study of the effect of the tip gap size and using a single circumferential groove on ...
https://jcamech.ut.ac.ir/article_70505_0.html
The effect of the tip gap size on the performance of a multistage axial compressor was studied by means of computational fluid dynamics (CFD). It was found that the performance of the compressor was very sensitive to the size of the tip gap. By increasing the gap size, the stall margin value, the total pressure ratio and the compressor efficiency reduced considerably. The flow field at the tip region of the blades at the near-stall point showed that the size of the blockage grew with an increase in the gap size. Afterwards, the effect of various single circumferential grooves- having specified widths and depths at different placement positions- on the performance were investigated in the reference gap. The stall margin increased about 7% with negligible reduction of the peak efficiency using one of the grooves which placed next to the trailing edge of the first-stage rotor. Also, this groove increased the stall margin in other tip gap sizes. Investigation of the flow field of the tip region in the reference gap showed that when the groove was used, there was a reduction in the back-flow near the trailing edge of the first-stage rotor. Consequently, the stall occurred at a lower mass flow rate.Sun, 07 Apr 2019 19:30:00 +0100Dynamics, Stability Analysis and Control of a Mammal-Like Octopod Robot Driven by Different ...
https://jcamech.ut.ac.ir/article_70560_0.html
In this paper, we studied numerically both kinematic and dynamic models of a biologically inspired mammal-like octopod robot walking with a tetrapod gait. Three different nonlinear oscillators were used to drive the robot’s legs working as central pattern generators. In addition, also a new, relatively simple and efficient model was proposed and investigated. The introduced model of the gait generator allowed us to obtain better both kinematic and dynamic parameters of motion of the robot walking in different directions. By changing the length and the height of a single step of the robot, we introduced in a simple way the initial, rhythmic and terminal phases of the robot gait. For numerical research and to visualization of the walking process, we developed a simulation model of the investigated robot in Mathematica software. We computed displacement, velocity and acceleration of the center of the robot’s body, fluctuations in the zero moment point of the robot and the ground reaction forces acting on the feet of the robot. The obtained results indicated some advantages of the proposed central pattern generator regarding fluctuations in the robot’s body, the minimum value of dynamic stability margin as well as the minimum value of a friction coefficient which is necessary to avoid slipping between the ground and the robot’s feet during walking process. Eventually, the proposed model of gait also allowed us to control the vertical position of the robot during walking in different directions.Wed, 10 Apr 2019 19:30:00 +0100A Theoretical Study of Steady MHD mixed convection heat transfer flow for a horizontal circular ...
https://jcamech.ut.ac.ir/article_70806_0.html
In this study, an investigation is carried out for laminar steady mixed 2D magnetohydrodynamic (MHD) flow of micropolar Casson fluid with thermal radiation over a horizontal circular cylinder with constant surface temperature. In the present study, an investigation is carried out on the effects of physical parameters on Casson fluid non dimensional numbers. The governing nonlinear partial differential equations and the controlling boundary conditions are derived for this case study. Furthermore, these equations are solved numerically using finite difference technique known as Keller Box Method (KBM). The effects of non-dimensional governing parameters, namely Casson parameter, mixed convection parameter, magnetic parameter, radiation parameter on the Nusselt number and local friction coefficient, as well as temperature, velocity and angular velocity are discussed and shown graphically. It is noticed that the local skin friction and the local Nasselt number has decrement behaviors when increasing the values the Casson parameter. But the opposite happens when the mixed convection parameter λ increase. It is found that the results in this study are in good agreement with previous studies. This proves that calculations using KBM method and the chosen step size are accurate enough for this type of problems.Tue, 16 Apr 2019 19:30:00 +0100Vibration suppression analysis for laminated composite beams embedded actuating ...
https://jcamech.ut.ac.ir/article_70830_0.html
This paper presents the analysis of vibration control of a laminated composite beam that including magnetostrictive layers. The embedded magnetostrictive materials are common smart materials that used as actuators and sensors. The formulation of problem is presented based on the shear deformation beam theory. For vibration suppression, the velocity feedback control with constant gain distributed is considered. The (Navier's) method is applied to analyze the solution of vibration suppression of laminated beam with the simply-supported boundary conditions. The influence of lamination schemes, modes, number of smart layers at the structure, the control gain of the magnetic field intensity and smart layer position on suppress of the vibration are discussed. In addition, the controlled motion of some special laminated composite beam is tested. Some validation examples are discussed and comparisons with the corresponding results in the literature are made. Additional results are presented to serve as benchmarks for future comparisons with other investigators.Sat, 27 Apr 2019 19:30:00 +0100Stability analysis of stratified two-phase liquid-gas flow in a horizontal pipe
https://jcamech.ut.ac.ir/article_70883_0.html
This study aimed at linear stability analysis of the stratified two-phase liquid-gas flow in a horizontal pipe. First, equations governing the linear stability of flow in each phase and boundary conditions were obtained. The governing equations were eigenvalue Orr Sommerfeld equations which are difficult and stiff problems to solve. After obtaining the velocity profiles of the gas and liquid phases in the pipe, the instability equations for each phase with related boundary conditions were coupled and simultaneously solved by using the Chebyshev Tau - QZ polynomial method. The instability spectra for some points has been plotted and some curves about instability conditions the same as neutral stability curve which shown stable and unstable region respect to Reynolds number had been drown. According to the neutral stability curve for each phase, the liquid phase is more exposed to instability than the gas phase. The liquid phase was unstable in low Reynolds numbers and a large amplitude of the wave velocity α but gas was unstable in higher Reynolds number and small amplitude of α.Sun, 05 May 2019 19:30:00 +0100NUMERICAL INVESTIGATION OF THE PERFORMANCE OF FIBRE-GLASS/TALC FILLED EPOXY COMPOSITE AS ...
https://jcamech.ut.ac.ir/article_70942_0.html
This study investigates experimentally and numerically the performance of fibre-glass/talc filled epoxy as an insulator in domestic heating application. The epoxy composites with micro filler (talc) and fibre glass used in this investigation were cured at temperatures of 50°C, 75°C, 100°C, 125°C and 150°C at a constant holding time of 120 minutes. A total of 40 composite specimen were tested and investigated in this paper. Thermal properties of the different composites at their specific cured temperatures are determined using a kd2 pro thermal analyser. The thermo-physical properties measured are the thermal conductivity, volumetric heat capacity and density of the composites. A computational fluid dynamics tool (ANSYS 15.0) was used to model a domestic cooking pot and run various simulations using the thermo-physical properties of the composites to study how the Fibre reinforced polymer (FRP) composites perform when compared Bakelite as the heat insulator handles of the modelled pot. Results obtained showed that 10 of this composites at different cured temperature performed better than Bakelite, with the 2E composite cured at 125°C (125°C- 2E), being the best performing composite out of the 40 specimen investigated, having insulated about 30°C of heat compared to Bakelite with 24.4°C. It was observed that all the composites insulated heat above 20°C which is a considerable value for this form of domestic heating application, and thus fibreglass talc filled epoxy can be recommended for domestic heating insulation over existing material with advantageous qualities such as light weight, naturally occurring, cost effectiveness and availability.Wed, 08 May 2019 19:30:00 +0100