Journal of Computational Applied MechanicsJournal of Computational Applied Mechanics
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https://jcamech.ut.ac.ir/
Feed provided by Journal of Computational Applied Mechanics. Click to visit.Numerical and Economic Study of Performance of Centrifugal Pump as Turbine
https://jcamech.ut.ac.ir/article_63159_8114.html
In this paper, performance of centrifugal pump as turbine (PAT) is investigated numerically. Three different specific speeds are considered and three pumps are designed using diagrams from catalogues and CFturbo V.9 software. Next, models are analyzed by Ansys CFX 16 software and results are compared with those of CFturbo software. Also, a mesh study analysis for one case is performed in order to show the effect of grid size on the solution. In addition, three different flow rates of 75%, 100%, and 125% of best efficiency point (BEP) are considered for extracting head-flow rate diagrams and comparing results of CFX and CFturbo software. In next step, using relations between pump and turbine modes (PAT formulations) and by changing boundary conditions in CFX, turbine mode is investigated and efficiency is compared with pump mode. Finally, by an economic analysis a comparison between PATs and turbines with same nominal output powers are performed to distinguish which case is more profitable. Results showed that PATs have lower payback time in comparison with turbines with equal output power (in low capacities), although they have lower efficiencies.Thu, 30 Nov 2017 20:30:00 +0100Design and Fabrication of a Portable 1-DOF Robotic Device for Indentation Tests
https://jcamech.ut.ac.ir/article_63272_0.html
There are many tactile devices for indentation examinations to measure mechanical properties of tissue. The purpose of this paper is to develop a portable indentation robotic device to show its usability for measuring the mechanical properties of a healthy abdominal tissue. These measurements will help to develop suitable mathematical models representing abdominal tissue. A 1-DOF portable robotic device has been designed to be placed on the patient’s body. The device presses sensor plate on the abdomen. Force and position sensors measure the indentation force and displacement, respectively. Due to tissue time-dependent behavior, linear viscoelastic models with three, five and seven parameters have been selected for mathematical modeling. Nonlinear Least Squares (NLS) method is adopted to fit viscoelastic models with experimental data obtained from stress relaxation tests. Using Finite Prediction Error (FPE) criterion, viscoelastic model with five parameters has been selected as the optimal model. The results of the present paper can be used in abdominal tissue simulators to facilitate teaching palpation examinations.Mon, 02 Oct 2017 20:30:00 +0100Accelerating high-order WENO schemes using two heterogeneous GPUs
https://jcamech.ut.ac.ir/article_63189_8114.html
A double-GPU code is developed to accelerate WENO schemes. The test problem is a compressible viscous flow. The convective terms are discretized using third- to ninth-order WENO schemes and the viscous terms are discretized by the standard fourth-order central scheme. The code written in CUDA programming language is developed by modifying a single-GPU code. The OpenMP library is used for parallel execution of the code on both the GPUs. Data transfer between GPUs which is the main issue in developing the code, is carried out by defining halo points for numerical grids and by using a CUDA built-in function. The code is executed on a PC equipped with two heterogeneous GPUs. The computational times of different schemes are obtained and the speedups with respect to the single-GPU code are reported for different number of grid points. Furthermore, the developed code is analyzed by CUDA profiling tools. The analyze helps to further increase the code performance.Thu, 30 Nov 2017 20:30:00 +0100Modeling SMA actuated systems based on Bouc-Wen hysteresis model and feed-forward neural network
https://jcamech.ut.ac.ir/article_63273_0.html
Despite the fact that shape-memory alloy (SMA) has several mechanical advantages as it continues being used as an actuator in engineering applications, using it still remains as a challenge since it shows both non-linear and hysteretic behavior. To improve the efficiency of SMA application, it is required to do research not only on modeling it, but also on control hysteresis behavior of these materials which are the fundamentals of several research opportunities in this area. Having considered these requirements, we have introduced a mathematical model to describe the hysteresis behavior of a mechanical system attached to SMA wire actuators using Bouc-Wen hysteresis model and feed-forward neural network. Due to inability of linear mass-spring-damper equations of classic Bouc-wen model to explain the hysteresis behavior of SMA actuators, in this paper we have applied changes in the mentioned equations of classic Bouc-Wen model to describe hysteresis loops of model. We also have used flexibility of the neural network systems to describe Bouc-Wen output in the main equation. Parameters of the developed model have been trained for a real mechanical system using simulation data after selecting proper configuration for the selected neural network. Finally, we have checked the accuracy of our model by applying two different series of validation data. The result shows the acceptable accuracy of the developed model.Mon, 02 Oct 2017 20:30:00 +0100Simulation of Stresses Induced by Heat and Mass Transfer in Drying Process of Clay-like Material
https://jcamech.ut.ac.ir/article_63274_8114.html
Drying represents one of the oldest unit operations employed in industrial processes. Drying is viewed as a process of simultaneous heat and mass transfer. Porous Clay-like material undergoes stresses due to non-uniform distribution of temperature and moisture induced by heat and mass transfer respectively. The aim of this work is to simulate the stresses induced by heat and mass transfer during drying. A mathematical model to simulate the convective drying of a porous material like clay has been developed. The problem investigated involves highly coupled equations considering heat, mass, and mechanical aspects. The particularity of the model is that it takes into account the strong coupling between mass transport, heat transport and mechanical behavior of the material. The variables of coupling are the solid deformation, moisture content and temperature of porous medium. A numerical solution is sought to foresee the variation of moisture content, temperature, shrinkage, heat transfer induced stresses and mass transfer induced stresses during drying. The solution developed as a model is capable of predicting the quality of the product through a failure criterion. The model is validated through the comparison of simulated and experimental data. Simulation results show that the heat transfer induced stresses are significantly less important in compression with the mass transfer induced stresses and can be neglected in modeling of drying process.Thu, 30 Nov 2017 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 +0100A new approach for nonlinear vibration analysis of thin and moderately thick rectangular plates ...
https://jcamech.ut.ac.ir/article_63295_8114.html
In this study, a hybrid method is proposed to investigate the nonlinear vibrations of pre- and post-buckled rectangular plates for the first time. This is an answer to an existing need to develope a fast and precise numerical model which can handle the nonlinear vibrations of buckled plates under different boundary conditions and plate shapes. The method uses the differential quadrature element, arc-length, harmonic balance and direct iterative methods. The governing differential equations of plate vibration have been extracted considering shear deformations and the initial geometric imperfection. The solution is assumed to be the sum of the static and dynamic parts which upon inserting them into the governing equations, convert them into two sets of nonlinear differential equations for static and dynamic behaviors of the plate. First, the static solution is calculated using a combination of the differential quadrature element method and an arc-length strategy. Then, putting the first step solutions into the dynamic nonlinear differential equations, the nonlinear frequencies and modal shapes of the plate are extracted using the harmonic balance and direct iterative methods. Comparing the obtained solutions with those published in the literature confirms the accuracy and the precision of the proposed method. The results show that an increase in the nonlinear vibration amplitude increases the nonlinear frequencies.Thu, 30 Nov 2017 20:30:00 +0100Effect of nano-structuration and compounding of YSZ APS TBCs with different thickness on ...
https://jcamech.ut.ac.ir/article_63368_0.html
Effect of nano-structuration and compounding of YSZ APS TBCs investigated on coating behavior in thermal shock conditions. The coatings were applied on Inconel 738 discs with three different thickness per powder. In order to harmonize the results from the samples, performance factor is defined as a criterion that in the starting of the activity has an amount of about 100 and is reduced after the damage begins. The results revealed that the growth of damage in the YSZ class is almost linear, and this behavior is observed in all samples. The thick TGO in this class shows its high oxygen permeability, and the type of damage indicates that its location is near the TGO region. The nano-structured YSZ class has a very good performance and through an interesting phenomenon, the slope of the damage growth diagrams is decreasing with time. The obvious thing about the CSZ class microstructure is the presence of horizontal and vertical cracks and its dense structure. In this class, the main location of damage is through the coating and after the beginning of damage, its curve has grown with a high rate. The best performance among all samples belongs to the nano-structured YSZ, which due to the presence of nano-zones, has a higher toughness and ability to endure more cycles.Mon, 09 Oct 2017 20:30:00 +0100Performance Improvements of a Centrifugal Pump with Different Impellers using Polymer Additive
https://jcamech.ut.ac.ir/article_63338_8114.html
In this study, the performance of a centrifugal pump is investigated by adding polyacrylamide (PAM) polymer over the working fluid which is tap water in this case. PAM is a long chain polymer that leads to reduce the wall shear stress and drag in a turbulent fluid. Three different blade profiles including radial, straight backward and circular backward have been examined. For this purpose, a centrifugal pump test rig consists of reservoir, pump-motor, volumetric measuring tank, pressure gauges, speed control, and motor dynamometer has been used. Different concentrations of PAM polymer solution are prepared in the range of 80-240 ppm of PAM. The results show that the maximum amount of relative efficiency is approximately 3% for the radial propeller, 13% for the straight backward propeller, and 18% for the circular backward which is occurs at 160 ppm of PAM. It is found that this increase is more pronounced in the case of circular backward impeller. Moreover, in the case of radial blade profile, it is observed that in spite of efficiency increase, the head decreases at low flow rate with adding PAM.Thu, 30 Nov 2017 20:30:00 +0100Dynamics of Nonlinear rectangular plates subjected to an orbiting mass based on shear ...
https://jcamech.ut.ac.ir/article_63386_0.html
In this paper, transverse and longitudinal vibration of nonlinear plate under exciting of orbiting mass is considered based on first-order shear deformation theory. The nonlinear governing equation of motion are discretized by the finite element method in combination with Newmark’s time integration scheme under von Karman strain-displacement assumptions. For validation of method and formulation of solution, a simply supported beam-plate under a moving force is considered and compared with existing results in the literature. The effects of nonlinearity, mass ratios, different geometric parameters, orbiting radius and angular velocity on dynamic response of plate are studied. This study present the importance of nonlinear analysis of rectangular plate under orbiting mass due to large deformation. In this paper, transverse and longitudinal vibration of nonlinear plate under exciting of orbiting mass is considered based on first-order shear deformation theory. The nonlinear governing equation of motion are discretized by the finite element method in combination with Newmark’s time integration scheme under von Karman strain-displacement assumptions. For validation of method and formulation of solution, a simply supported beam-plate under a moving force is considered and compared with existing results in the literature. The effects of nonlinearity, mass ratios, different geometric parameters, orbiting radius and angular velocity on dynamic response of plate are studied. This study present the importance of nonlinear analysis of rectangular plate under orbiting mass due to large deformation.Mon, 09 Oct 2017 20:30:00 +0100Simulation of the Mode I fracture of concrete beam with cohesive models
https://jcamech.ut.ac.ir/article_63339_8114.html
Crack propagation modeling in quasi-brittle materials such as concrete is essential for improving the reliability and load-bearing capacity assessment. Crack propagation explains many failure characteristics of concrete structures using the fracture mechanics approach. This approach could better explain the softening behavior of concrete structures. A great effort has been made in developing numerical models; however, some models involve complex expressions with too many parameters, and the results are in some cases inaccurate. In this investigation, a numerical approach is developed to model the fracture process zone (FPZ). Based on the modified crack closure integral (MCCI) method, a new nonlinear spring is proposed to be placed between the interfacial node pairs to model crack propagation. A new strain energy release rates for Mode I is calculated as a function of opening in the softening part. Two benchmark beams are simulated by the ABAQUS software for the accuracy of cohesive zone model. The model decreases complexity of predicting crack propagation. It is observed that the cohesive zone model is robust, accurate and able to model the crack growth in the concrete beam. The prediction of the crack path is close to the experimental results (up to 90%). The peak loads had approximately 7.7% difference compared with the previous experimental loads. The accuracy of displacement in the present study is 15.9% compared with previously model at the same load intensity.Thu, 30 Nov 2017 20:30:00 +0100Numerical and Neural Network Modeling and control of an Aircraft Propeller
https://jcamech.ut.ac.ir/article_64203_0.html
In this paper, parametric and numerical model of the DC motor, connected to aircraft propellers are extracted. This model is required for controlling trust and velocity of the propellers, and consequently, an aircraft. As a result, both of torque and speed of the propeller can be controlled simultaneously which increases the kinematic and kinetic performance of the aircraft. Parametric model of the motor is derived by conducting standard tests such as locked rotor test and step and sine wave input one. In order to derive a neural network and numerical model, a set of sinusoidal, triangular, and random step signals are applied as the input to the motor and its speed is recorded as an output. Neural network of the motor is extracted by using these datasets and considering a multilayer perceptron (MLP) neural network structure with Levenberg-Marquardt training method. Results of the numerical model and parametric model are compared and validated by experimental implementations. The superiority of the proposed method is also shown respect to traditional PID algorithm.Tue, 19 Dec 2017 20:30:00 +0100Prediction of Temperature distribution in Straight Fin with variable Thermal Conductivity and ...
https://jcamech.ut.ac.ir/article_63383_8114.html
Due to increasing applications of extended surfaces as passive methods of cooling, study of thermal behaviors and development of mathematical solutions to nonlinear thermal models of extended surfaces have been the subjects of research in cooling technology over the years. In the thermal analysis of fin, various methods have been applied to solve the nonlinear thermal models. This paper focuses on the application of Legendre wavelet collocation method to the prediction of temperature distribution in longitudinal rectangular fin with temperature-dependent thermal conductivity and internal heat generation. The numerical approximations by the method are used to carry out parametric studies of the effects of the model parameters on the temperature distribution in the fin. The results show that the thermal performance of the fin is favoured at low values of thermogeometric parameter and internal heat generation decreases the performance of the fin. The results can serve as verification of the solutions of other methods of analysis of the component.Thu, 30 Nov 2017 20:30:00 +0100Transverse Sensing of Simply Supported Truncated Conical Shells
https://jcamech.ut.ac.ir/article_64204_0.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.Tue, 19 Dec 2017 20:30:00 +0100Analysis of Flow of Nanofluid through a Porous Channel with Expanding or Contracting Walls ...
https://jcamech.ut.ac.ir/article_63377_8114.html
In this work, we applied Chebychev spectral collocation method to analyze the unsteady two-dimensional flow of nanofluid in a porous channel through expanding or contracting walls with large injection or suction. The solutions are used to study the effects of various parameters on the flow of the nanofluid in the porous channel. From the analysis, It was established that increase in expansion ratio and Reynolds number decreases the axial velocity at the center of the channel during the expansion while the axial velocity increases near the surface of the channel during contraction. Moreover, it was also established that an increase in injection rate leads to a higher axial velocity near the center and the lower axial velocity near the wall. On the verification of the results, it is shown that the results obtained from Chebychev spectral collocation method are in good agreement when compared to the results obtained using other numerical methods.Thu, 30 Nov 2017 20:30:00 +0100Surface hardness improvement in high efficiency deep grinding process by optimization of ...
https://jcamech.ut.ac.ir/article_64205_0.html
The grinding is one of the most important methods that directly affects tolerances in dimensions, quality and finished surface of products. One of the major problems in the material removal processes specially grinding is the heat generation during the process and the residual tensile stress in the surfaces of product. Therefore, optimization of High Efficiency Deep Grinding (HEDG) process is the main goal of this study to reduce the generated heat and residual tensile stress and increase strength and surface hardness of AISI1045 annealed steel. To this end, the effects of main parameters e.g. depth of cut, wheel speed, workpiece speed and cross feed on surface hardness has been investigated. The experimental results demonstrated the reduction in surface temperature and increase in hardness as optimum conditions are applied to the grinding process. Moreover, the experimental results were validated by comparing with other experimental results and analyzing of surface microhardness, surface temperature and normal and tangential forces.Tue, 19 Dec 2017 20:30:00 +0100Applications of higher order shear deformation theories on stress distribution in a five layer ...
https://jcamech.ut.ac.ir/article_63354_8114.html
In this paper, layerwise theory (LT) along with the first, second and third-order shear deformation theories (FSDT, SSDT and TSDT) are used to determine the stress distribution in a simply supported square sandwich plate subjected to a uniformly distributed load. Two functionally graded (FG) face sheets encapsulate an elastomeric core while two epoxy adhesive layers adhere the core to the face sheets. The sandwich plate is assumed to be symmetric with respect to its core mid-plane. First, second and third-order shear deformation theories are used to model shear distribution in the adhesive layers as well as others. Results obtained from the three theories are compared with those of finite element solution. Results indicate that finite element analysis (FEA) and LT based on the first, second and third-order shear deformation theories give almost the same estimations on planar stresses. Moreover, the out-of-plane shear stresses obtained by FEA, are slightly different from those of LT based on FSDT. The differences are decreased on using LT based on SSDT or TSDT. Additionally, SSDT and TSDT predict almost the same distribution for the two planer stress and out-of-plane shear stress components along the face sheet thickness. Furthermore, third-order shear deformation theory seems to be more appropriate for prediction of out-of-plane shear stress at lower values of a/h ratio.Thu, 30 Nov 2017 20:30:00 +0100Strongly Stable Multi-time Stepping Method with the Option of Controlling Amplitude Decay in ...
https://jcamech.ut.ac.ir/article_64206_0.html
Recently, multi-time stepping methods have become very popular among scientist due to their high stability in problems with critical conditions. One important shortcoming of these methods backs to their high amount of uncontrolled amplitude decay. This study proposes a new multi-time stepping method in which the time step is split into two sub-steps. The first sub-step is solved using the well-known Newmark method and for the second sub-step an extended version of Newmark method is applied. In fact, similarity in basic formulas of the mentioned methods makes it available to control the amount of amplitude decay in responses obtained by the proposed method; in other words, the amplitude decay in the proposed method is controlled through constant parameters of the two methods applied on each sub-step. The precision assessment of the proposed method is performed using numerical approaches and revealed the minor period elongation error of the proposed method in comparison with other existing methods. In addition to this, the unconditional stability region of constant parameters is also determined through computation of spectral radius of the proposed method. Finally, practical assessment of the proposed method is performed through several numerical examples.Tue, 19 Dec 2017 20:30:00 +0100Incremental explosive analysis and its application to performance-based assessment of stiffened ...
https://jcamech.ut.ac.ir/article_63353_8114.html
In this paper, the dynamic behavior of square plates with various thicknesses and stiffening configurations subjected to underwater explosion (UNDEX) are evaluated through a relatively novel approach which is called Incremental Explosive Analysis (IEA). The IEA estimates the different limit-states and deterministic assessment of plats’ behavior, considering uncertainty of loading conditions and dynamic nature of explosive loading. In this new approach, intensity parameter of explosive loading is enhanced in an incremental manner and response of the target plate is recorded for every depth-stand-off loading condition. Then, the multi IEA curves are derived from several simulation results. The fractiles method is employed to summarize large amount of IEA curves’ data in a predictive mode. In addition, some summarized damage probability indicators such as fragility curves are extracted that provide useful information for quantitative damage analysis of plates in UNDEX loading. Results show that the IEA is a promising method for performance-based assessment of marine structures subjected to UNDEX loading.Thu, 30 Nov 2017 20:30:00 +0100Heat Transfer Study of Convective-Radiative Fin under the influence of Magnetic Field using ...
https://jcamech.ut.ac.ir/article_64207_0.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.Tue, 19 Dec 2017 20:30:00 +0100Analysis of Heat transfer in Porous Fin with Temperature-dependent Thermal Conductivity and ...
https://jcamech.ut.ac.ir/article_63384_8114.html
In this work, analysis of heat transfer in porous fin with temperature-dependent thermal conductivity and internal heat generation is carried out using Chebychev spectral collocation method. The numerical solutions are used to investigate the influence of various parameters on the thermal performance of the porous fin. The results show that increase in convective parameter, porosity parameter, Nusselt, Darcy and Rayleigh numbers and thickness-length ratio of the fin, the rate of heat transfer from the base of the fin increases and consequently improve the efficiency of the fin. However, the rate of heat transfer from the base of the fin increases with decrease in thermal conductivity material. Also, from the parametric studies, an optimum value is reached beyond which further increase in porosity, Nusselt, Darcy and Rayleigh numbers, thermal conductivity ratio and thickness-length ratio has no significant influence on the rate of heat transfer. It is established that the temperature predictions in the fin using the Chebychev spectral collocation method are in excellent agreement with the results of homotopy perturbation method and that of numerical methods using Runge-Kutta coupled with shooting method.Thu, 30 Nov 2017 20:30:00 +0100Investigation on Instability of Rayleigh-Benard Convection Using Lattice Boltzmann Method with ...
https://jcamech.ut.ac.ir/article_64208_0.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.Tue, 19 Dec 2017 20:30:00 +0100A novel computational procedure based on league championship algorithm for solving an inverse ...
https://jcamech.ut.ac.ir/article_63340_8114.html
Inverse heat conduction problems, which are one of the most important groups of problems, are often ill-posed and complicated problems, and their optimization process has lots of local extrema. This paper provides a novel computational procedure based on finite differences method and league championship algorithm to solve a one-dimensional inverse heat conduction problem. At the beginning, we use the Crank-Nicolson semi-implicit finite difference scheme to discretize the problem domain and solve the direct problem which is a second-order method in time and unconditionally stable. The consistency, stability and convergence of the method are investigated. Then we employ a new optimization method known as league championship algorithm to estimate the unknown boundary condition from some measured temperature on the line. League championship algorithm is a recently proposed probabilistic algorithm for optimization in continuous environments, which tries to simulate a championship environment wherein several teams with different abilities play in an artificial league for several weeks or iterations. To confirm the efficiency and accuracy of the proposed approach, we give some examples for the engineering applications. Results show an excellent agreement between the solution of the proposed numerical algorithm and the exact solution.Thu, 30 Nov 2017 20:30:00 +0100Performance, Thermal Stability and Optimum Design Analyses of Rectangular Fin with ...
https://jcamech.ut.ac.ir/article_64209_0.html
In this study, we analysed the thermal performance, thermal stability and optimum design analyses of a longitudinal, rectangular fin with temperature-dependent, thermal properties and internal heat generation under multi-boiling heat transfer using Haar wavelet collocation method. The effects of the key and controlling parameters on the thermal performance of the fin are investigated. The thermal stability criteria and optimum design parameter were established. From the investigation, the study reveals that the performance of the fin is enhanced as the boiling condition parameter or the exponent decreases. It is also established that the optimum fin length (at which Q/ζ reaches a maximum value) increases as the non-linear thermal conductivity term β, increases. Furthermore, the study shows that the optimum value of M can be obtained based on the value of the non-linear term. The computational results obtained in this study were compared with established numerical solutions and is found to be in good agreement with the standard numerical solutions.Tue, 19 Dec 2017 20:30:00 +0100Power Series -Aftertreatment Technique for Nonlinear Cubic Duffing and Double-Well Duffing ...
https://jcamech.ut.ac.ir/article_63385_8114.html
Modeling of large amplitude of structures such as slender, flexible cantilever beam and fluid-structure resting on nonlinear elastic foundations or subjected to stretching effects often lead to strongly nonlinear models of Duffing equations which are not amendable to exact analytical methods. In this work, explicit analytical solutions to the large amplitude nonlinear oscillation systems of cubic Duffing and double-well Duffing oscillators are provided using power series-aftertreatment technique. The developed analytical solutions are valid for both small and large amplitudes of oscillation. The accuracy and explicitness of the analytical solutions are carried out to establish the validity of the method. Good agreements are established between the solution of the new method and established exact analytical solution. The developed analytical solutions in this work can serve as a starting point for a better understanding of the relationship between the physical quantities of the problems as it provides continuous physical insights into the problems than pure numerical or computation methods.Thu, 30 Nov 2017 20:30:00 +0100On the thermal conductivity of carbon nanotube/polypropylene nanocomposites by finite element method
https://jcamech.ut.ac.ir/article_64210_0.html
In this paper, finite element method is used to obtain thermal conductivity coefficients of single-walled carbon nanotube reinforced polypropylene. For this purpose, the two-dimensional representative volume elements are modeled. The effect of different parameters such as nanotube dispersion pattern, nanotube volume percentage in polymer matrix, interphase thickness between nanotube and surrounded matrix and nanotube aspect ratio on the thermal conductivity coefficient of nanotube/polypropylene nanocomposite are investigated. For the dispersion pattern, three different algorithms, including random dispersion, regular dispersion along the temperature difference and regular dispersion perpendicular to the temperature difference are employed. Furthermore, the temperature is considered in the range of 0℃ to 200℃. The nanotube volume percentage in the polymer matrix is selected as 1%, 3% and 5%. It is shown that the polypropylene matrix reinforced by regular distribution of nanotubes directed parallel to the temperature difference leads to the largest thermal conductivity coefficients. Besides, the nanocomposites with larger volume percentages of carbon nanotubes possess larger thermal conductivity coefficients.Tue, 19 Dec 2017 20:30:00 +0100Multi-objective Optimization of web profile of railway wheel using Bi-directional Evolutionary ...
https://jcamech.ut.ac.ir/article_63341_8114.html
In this paper, multi-objective optimization of railway wheel web profile using bidirectional evolutionary structural optimization (BESO) algorithm is investigated. Using a finite element software, static analysis of the wheel based on a standard load case, and its modal analysis for finding the fundamental natural frequency is performed. The von Mises stress and critical frequency as the problem objectives are combined using different weight factors in order to find the sensitivity number in the method, which specifies which elements to be omitted and which to be added. The iterative process is continued until convergence to an a priori specified material volume. The resulted web profiles show that when the stress is important, material removal is from the middle part of the web, while for frequency as the important objective, the removal is from near the rim part of the web. The suggested profile, corresponding to equal weight factor for the objectives, has a better volume and stress state compared to a standard web profile, and has a more uniform stress distribution. However, higher natural frequency, compared to that of the standard profile, are obtained for larger frequency weight factors, although with a bigger volume. In the end, considering manufacturability of the wheel, the jagged profile resulted from BESO is replaced with a fitted smooth curve and performing the finite element analysis on it. It is seen that there is an improvement in the obtained objectives for the smoothened profile, with no significant change in volume.Thu, 30 Nov 2017 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 +0100On the Analysis of Laminar Flow of Viscous Fluid through a Porous Channel with ...
https://jcamech.ut.ac.ir/article_63371_8114.html
The vast biological and industrial applications of laminar flow of viscous fluid through a porous channel with contracting or expanding permeable wall have attest to the importance of studying the flow process. In this paper, two-dimensional flow of viscous fluid in a porous channel through slowly expanding or contracting walls with injection or suction is analyzed using variation parameter method. From the parametric studies using the developed approximate analytical solutions, it is shown that increase in the Reynolds number of the flow process leads to decrease in the axial velocity at the center of the channel during the expansion. The axial velocity increases slightly near the surface of the channel when the wall contracts at the same rate. Also, as the wall expansion ratio increases, the velocity at the center decreases but it increases near the wall. The results of the approximate analytical solution are verified by numerical solution using shooting method coupled with Runge-Kutta method. The results of the variation parameter method are in excellent agreement with the results obtained using numerical method.Thu, 30 Nov 2017 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 +0100Analysis and Optimization using Renewable Energies to Get Net-Zero Energy Building for Warm Climate
https://jcamech.ut.ac.ir/article_63296_8114.html
Due to low energy price, economic optimization of consumption has no justification for users in Iran. Nowadays, the issue of ending fossil fuels, production of greenhouse gases and the main role of building in consumption of considerable amount of energy has drawn the focus of global researches to a new concept called net zero energy building. In this study, modeling, simulation and energy analysis have been used for considered building in Zahedan weather condition which has a dry and warm climate to draw the related equations and perform analysis. Multi-Objective optimization has been performed for simultaneous reduction of total energy consumption and total cost where the main decision making variables including thermal comfort, cooling, heating and lighting systems and other variables have been influential. The comparison of an ordinary optimized building and the intended optimized building which uses renewable energy resources indicates that it is possible to get to net zero energy building in addition to selling surplus 2 MWh electrical energy to electricity grid with simultaneous use of solar and wind renewable energies.Thu, 30 Nov 2017 20:30:00 +0100Effect of the asymmetrical rolling process on the micro hardness and microstructure of brass wire
https://jcamech.ut.ac.ir/article_64550_0.html
Current experimental investigation deals with the effects of asymmetrical rolling parameters on the inhomogeneity, microstructure, mechanical, and geometrical properties of rolled brass wire. Toward this end, a roll machine with three different roll radii ratios was set up. The asymmetrical conditions are arranged using three different sets of rolls with different diameters that result into different reductions. Investigating the effects of the inhomogeneous structure of unrolled brass wire on the output radius, total width, and width of the rolled part (in the z direction) are the aim of this study. Furthermore, the influences of three unlike roll radius ratios on the grain size, inhomogeneity and mechanical properties of the rolled brass wire are considered. In addition, the micro-Vickers measurements on the rolled brass wire are performed. It is shown that the regions near to faster roll with greater strain quantities have higher values of hardness compared to the other areas.Wed, 10 Jan 2018 20:30:00 +0100A new virtual leader-following consensus protocol to internal and string stability analysis of ...
https://jcamech.ut.ac.ir/article_64168_8114.html
In this paper, a new virtual leader following consensus protocol is introduced to perform the internal and string stability analysis of longitudinal platoon of vehicles under generic network topology. In all previous studies on multi-agent systems with generic network topology, the control parameters are strictly dependent on eigenvalues of network matrices (adjacency or Laplacian). Since some of these eigenvalues are complex, the stability analysis with the presented methods is very hard or even impossible for large scale or time-varying networks. A new approach is introduced in this paper to decouple the large dimension closed-loop dynamics to individual third-order linear differential equations. A new spacing policy function assuring safety and increasing the traffic capacity is introduced to adjust the inter-vehicle spacing. The stable regions of communication and parasitic delays are calculated by employing the cluster treatment characteristic roots (CTCR) method. In addition to internal stability, it will be shown that the presented approach guarantees the string stability of generic vehicular networks. The most important privilege of the presented method compared with the previous approaches, is that the control gains are independent on network structure. This new finding, simplifies the stability analysis and control design specially for large scale platoons and time-varying networks. Several simulation results are provided to show the effectiveness of the proposed approaches.Thu, 30 Nov 2017 20:30:00 +0100Modelling of Suddenly Expanded Flow Process in Supersonic Mach Regime using Design of ...
https://jcamech.ut.ac.ir/article_64593_0.html
The present work is an attempt to model, analyze, and control the flow at the base of an abruptly expanded circular duct by using design of experiments (DOE) and response surface methodology (RSM). Tiny-jets in the form of orifice were positioned at an interval of 900, 6.5 mm from the primary axis of the main jet of the nozzle. Experiments were conducted to measure two responses namely, base pressure without the use of micro jets or active control (WoC) and base pressure with the use of micro jets or active control (WC). Mach number (M), nozzle pressure ratio (NPR), area ratio (AR) and length to diameter ratio (L/D) were considered as input variables (parameters), which control the outputs (i.e. base pressure). Non-linear regression models based on central composite design (CCD) and Box-Behnken design (BBD) have been developed in order to facilitate the input-output relationships. Moreover, the significance of main, square and interaction terms of the developed models have been tested by performing analysis of variance (ANOVA). The ANOVA and significance test results and their respective correlation coefficient values indicate that both the CCD and BBD regression models are statistically adequate for both the base pressure responses of without control and with control respectively. The performances of the nonlinear models have been validated for accuracy prediction by use of 15 test cases. The performance of BBD model is found to be better in forecasting base pressure for both cases of without control and with control when compared to the CCD model.Sat, 13 Jan 2018 20:30:00 +0100A review of functionally graded thick cylindrical and conical shells
https://jcamech.ut.ac.ir/article_64074_8114.html
Thick shells have attracted much attention in recent years as intelligent and functional graded materials because of their unique properties. In this review paper, some critical issues and problems in the development of thick shells made from Functionally graded piezoelectric material (FGPM) are discussed. This review has been conducted on various types of methods which are available for thick shell analysis and mainly focuses on elasticity theories, shear deformation theory, simplified theories and mixed theories since they were widely used in the modeling of FG thick shells. It is expected that this comprehensive study will be very beneficial to everyone involved or interested in the shell models.Thu, 30 Nov 2017 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 +0100Impeller and volute design and optimization of the centrifugal pump with low specific speed in ...
https://jcamech.ut.ac.ir/article_64656_0.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.Wed, 17 Jan 2018 20:30:00 +0100Comparison between the frequencies of FML and composite cylindrical shells using beam modal ...
https://jcamech.ut.ac.ir/article_64657_0.html
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 +0100An Investigation on the Effects of Optimum Forming Parameters in Hydromechanical Deep Drawing ...
https://jcamech.ut.ac.ir/article_64678_0.html
The present research work is concerned with the effects of optimum process variables in elevated temperature hydromechanical deep drawing of 5052 aluminium alloy. Punch workpiece and die workpiece friction coefficients together with the initial gap between the blank holder and matrix were considered as the process variables which, in optimization terminology, are called design parameters. Since both the maximum reduction in sheet thickness and the final product uniformity (thickness variation) are important in the hydromechanical deep drawing, they are selected as the objective functions for optimization. After conducting 27 finite element simulations of the operation and validation of the numerical results, a neural network was trained and combined with the genetic algorithm to obtain the optimum design parameters. The outcomes of this investigation have shown that these optimized process variables simultaneously resulted in the best values for both the objective functions, in comparison with all the conducted finite element analyses.Fri, 19 Jan 2018 20:30:00 +0100Free vibration and buckling analysis of third-order shear deformation plate theory using exact ...
https://jcamech.ut.ac.ir/article_64679_0.html
In this paper, wave propagation approach is used to analyze the free vibration and buckling analysis of thick rectangular plates based on higher order shear deformation plate theory. From wave viewpoint, vibrations can be considered as travelling waves along structures. Waves propagate in a waveguide and transmit and reflect at the boundaries. 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 plates. In this study, firstly the matrices of propagation and reflection are derived and by combining them, the characteristic equation of the plate is obtained. Comprehensive dimensionless natural frequencies and buckling loads results are presented for rectangular thick plates with different boundary conditions for various values of aspect ratio and thickness to length ratio. It is observed that obtained results of the wave propagation method are in good agreement with the obtained values by literature.Fri, 19 Jan 2018 20:30:00 +0100Modification of exponential based hyperelastic strain energy to consider free stress initial ...
https://jcamech.ut.ac.ir/article_64739_0.html
In this research, the exponential stretched based hyperelastic strain energy was modified to provide the unstressed initial configuration. To this end, as the first step, the model was calibrated by the experimental data to find the best material parameters. The fitting results indicated material stability in large deformations and basic loading modes. In the second step, the initial pseudo stress value (ISV) was eliminated from the hyperelastic strain energy using a function of the determinant of the deformation gradient. The modified and unmodified models were implemented in ABAQUS/VUMAT user subroutine and the deformation behavior of the natural rubber and the thermoplastic elastomer was predicted. The results obtained from the modified model represented a better agreement with the experimental data, in comparison to those gained by the unmodified model. In order to present the significance of the unstressed initial configuration in engineering applications, the stenting phenomenon in the atherosclerosis human artery was investigated. It was revealed that a uniform stress distribution could be achieved in the artery using the modified model, thereby reducing the possibility of tearing and restenosis.Thu, 25 Jan 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 +0100Variation of Parameters Method for Thermal Analysis of Straight Convective- Radiative Fins with ...
https://jcamech.ut.ac.ir/article_65076_0.html
In this study, thermal performance across straight convecting- radiating fin with temperature dependent thermal conductivity is considered. The variation of parameters (VPM) is adopted to analyze the nonlinear higher order differential equations arising due to thermal conductivity and heat transfer coefficient on temperature distribution. Pertinent parameters such as thermo geometric and radiation parameters effect on temperature profile are investigated. Result obtained illustrates that quantitative increase of thermo geometric parameter causes a significant increase in temperature distribution due to increase in ratio of convective to conduction heat transfer which influence is significant toward fin base while increasing radiation parameter leads to decrease in temperature distribution due to increasing heat transfer from fins surface to ambient environment . Comparative analysis of result obtained in study against literature proves to be in satisfactory agreement. Therefore study provides useful insight to fins operational performance in applications such as radiators, boilers, refrigeration devices, oil pipelines amongst others.Thu, 22 Feb 2018 20:30:00 +0100Free Vibration Analysis of Nanoplates Made of Functionally Graded Materials Based On Nonlocal ...
https://jcamech.ut.ac.ir/article_65214_0.html
In this paper, an analysis of free vibration in functionally graded nanoplate is presented. Third-order shear deformation plate theory is used to reach more accuracy in results. Small-scale effects are investigated using Eringen`s nonlocal theory. The governing equations of motion are obtained by Hamilton`s principle. It is assumed that the properties of nanoplates vary through their thicknesses according to a volume fraction power law distribution. The finite element method (FEM) is presented to model the functionally graded nanoplate and solve mathematical equations accurately. The finite element formulation for HSDT nanoplate is also presented. Natural frequencies of FG nanoplate with various boundary conditions are compared with available results in the literature. At the end some numerical results are presented to evaluate the influence of different parameters, such as power law index, nonlocal parameter, aspect ratio and aspect of length to thickness of nanoplate. In addition, all combinations of simply supported and clamped boundary conditions are considered.Wed, 31 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 +0100Evaluation of Thermo-mechanical stress in work rolls of ring rolling mill under thermal and ...
https://jcamech.ut.ac.ir/article_65484_0.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.Wed, 28 Feb 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_0.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.Tue, 06 Mar 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 +0100