Journal of Computational Applied MechanicsJournal of Computational Applied Mechanics
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Feed provided by Journal of Computational Applied Mechanics. Click to visit.Numerical study and genetic algorithm optimization of hot extrusion process to produce ...
http://jcamech.ut.ac.ir/article_60705_7900.html
Rectangular waveguide (WR) is one of the earliest types of transmission lines. Rectangular waveguide can be produced by hot extrusion process. In this paper, the hot extrusion process of CuZn5 rectangular waveguide was investigated by Finite Element Method (FEM). In addition, Genetic Algorithm method (GA) was used to optimize the die geometry and process conditions to achieve the lowest magnitude of extrusion force. Die geometry was introduced in terms of die length and billet hole diameter under various frictional conditions. It was found that die length and billet hole diameter had contradictory effects on the extrusion force. The optimum die length of l=40cm was obtained for µ=0.025 and that of l=20cm was achieved for µ=0.05, 0.075 and 0.1. Moreover, the optimum billet hole diameter of d=3cm was obtained for all frictional conditions. The experimental procedure was carried out to verify the accuracy of results. The extrusion force of 1600 T was obtained from experiment for the friction coefficient of µ≈0.1. The estimated force of such a condition with GA is 1577 T which has a good agreement with experimental result.Wed, 30 Nov 2016 20:30:00 +0100Forced vibration of piezoelectric nanowires based on nonlocal elasticity theory
http://jcamech.ut.ac.ir/article_60706_7900.html
In this paper, a numerical solution procedure is presented for the forced vibration of a piezoelectric nanowire under thermo-electro-mechanical loads based on the nonlocal elasticity theory within the framework of Timoshenko beam theory. Using Hamilton’s principle, the nonlocal governing differential equations are derived. The governing equations and the related boundary conditions are discretized by using the differential quadrature method (DQM). The numerical results are obtained for both free and forced vibration of piezoelectric nanowires. The effects of the nonlocal parameter together with the other parameters such as temperature change, length and external electric voltage on the size-dependent forced vibration of the piezoelectric nanowires are studied. It is shown that the nonlocal effect (small scale effect) plays a prominent role in the forced vibration of piezoelectric nanowires and this effect cannot be neglected for small external characteristic lengths. As the nonlocal parameter increases, the distribution of electric potential becomes more non-uniform across the thickness of the nanowire. Furthermore, it is observed that the amplitude of piezoelectric nanowires increases with increasing nonlocal parameter. This means that the stiffness of piezoelectric nanowires reduces with increasing the effect of small scale.Wed, 30 Nov 2016 20:30:00 +0100Analysis of the dynamic behavior of the vehicle occupant in the irregular terrain
http://jcamech.ut.ac.ir/article_60707_7900.html
Many people experience vibration effects on whole- body throughout their lives frequently. Meanwhile,The main category are exposed with this problem drivers of vehicles such as tractor and lorry, that more than other people in the society are affected by this power and unfortunately most physical injury and the emergence of a variety of diseases caused by vibrations exerted on the body can be seen in this category of society. Vibrating energy absorbed is exposed whole-body caused by vibration hazard in the vertically on body and biodynamics responses from body in speed 2.37 to 5.14 meters per second can transporte by vehicle seat on occupant body, so the vibration energy transferred to a seated human body, the real component reflects the energy dissipated in the biological structure per unit of time, whereas the imaginary component reflects the energy stored/released by the system. In this paper the human body is modelled as a series/parallel 4 DOF dynamic models of system and use Lagrange equation for calculate head and neck equation.. The hybrid model is analysed by Matlab software for vertical vibration responses and vibration energy absorption.it is shown improvement seat vehicle cause ,drastically ameliorate the tolerance to high-intensity vibrations in the 0.8 Hz range by reducing the maximum amplitude ratios and relative displacements of the body parts to 0.031 and 0.20 mm, respectively and also body parts "acceleration levels" too much below the ISO "exposure limit" curveWed, 30 Nov 2016 20:30:00 +0100Analysis of Euler-Bernoulli nanobeams: A mechanical-based solution
http://jcamech.ut.ac.ir/article_60708_7900.html
The accuracy and efficiency of the elements proposed by Finite Element Method (FEM) considerably depend on the interpolating functions namely shape functions used to formulate the displacement field within the element. In the present study, novel functions, namely Basic Displacements Functions (BDFs), are introduced and exploited for Structural analysis of nanobeams using finite element method based on Eringen’s Nonlocal elasticity and Euler-Bernoulli beam theory. BDFs are obtained through solving the governing differential equation of motion of nanobeams using the power series method. Unlike the conventional methods which are almost categorized as displacement-based methods, the flexibility basis of the method ensures true satisfaction of equilibrium equations at any interior point of the element. Accordingly, shape functions and structural matrices are achieved in terms of BDFs by application of merely mechanical principles. In order to evaluate the competency and accuracy of the proposed method with different boundary conditions, several numerical examples with various boundary conditions are scrutinized. Carrying out several numerical examples, the results in stability analysis, free longitudinal vibration and free transverse vibration show a complete accordance with those in literature.Wed, 30 Nov 2016 20:30:00 +0100The effect of static magnetic field on hemodynamic properties of blood flow containing magnetic ...
http://jcamech.ut.ac.ir/article_60709_7900.html
The use of magnetic fields in targeted drug delivery, especially for treatment of cancers and tumoral regions, is one of the significant techniques in the field of modern methods of treatment. Considering that many vital biological tissues have been located deep in the body, then for targeted drug delivery and effective treatment in these tissues, it is required to bring therapeutic agent to the desired location and focus on that location. The purpose of this study is to evaluate the static magnetic field interaction with hemodynamic properties of blood flow containing a magnetic carrier substance as a bio magnetic fluid. The finite element method (FEM) is used for 2D numerical simulation of magnet with different tip shapes and evaluating of external static magnetic field and its effects on the blood flow with aforementioned properties. The results show that the static magnetic fields generated from magnets with different tip shapes have different effects on the distribution of the fluid velocity field. Furthermore it can be concluded that when magnetic field flux density is concentrated around the magnet tip, the intensity of these hemodynamic effects become more concentrated within the fluid and the location of the magnet tip on the tissue, though the hemodynamic variables have been changed.Wed, 30 Nov 2016 20:30:00 +0100Water thickness effect on the fin efficiency and heat transfer for partially wet-surface heat ...
http://jcamech.ut.ac.ir/article_60710_7900.html
Heat and mass transfer, in this paper, is considered in one-row heat exchanger, that fins are hotter than air flow and water is added to fins. Related governing equations are derived by analyzing a two-dimension model in a unique cell of a heat exchange. These equations are numerically solved by finite difference method. Heat transfer and efficiency under partially wet surface are calculated by changes in thickness of water layer on the fins and wet percentage region of fin with constant airflow characteristics. In this study, Lewis Number as unity and water vapor saturation as parabolic are assumed. Obtained results show that increasing in thickness of fin leads to increasing thermal resistance; therefore, efficiency of fin decreases. But thickness of water layer dose not play a significant role in fin efficiency when water layer covering the surface of fins is thin or it covers a small region of fins because thermal resistance of water is not comparable with thermal conductivity of fin material. But where thickness of water layer is comparable with fin pitch or more surface of fins is wetted, fin efficiency and heat transfer change obviously because of increasing thermal resistance and changing in air flow velocity that cause more decreasing in efficiency of fins.Wed, 30 Nov 2016 20:30:00 +0100Unsteady Magneto Hydro Dynamic Flow of a Second Order Fluid over an Oscillating Sheet with a ...
http://jcamech.ut.ac.ir/article_60711_7900.html
eUnsteady slip-flow of second grade non-Newtonian electrically conducting fluid over an oscillating sheet has been considered and solved numerically. A second-order slip velocity model is used to predict the flow characteristic over the wall. With the assumption of infinite length in the x-direction, the velocity of the fluid can be assumed as a function of y and t, hence, with proper change variable partial governing equations are converted to ordinary differential equations and resulting equations are solved numerically. Fourth-order finite difference scheme is used to solve the equations. The effects of the magnetic field applied on the surface, slip flow parameters, the frequency of oscillating, mass suction or injection and elastic second number on the velocity distribution are shown graphically and discussed. With the increase of slip flow parameter, unlike that of other parameters, the thickness of the fluid affected by the motion of boundary will decrease. It is also realized that both injection and suction of mass on the sheet, will increase the amplitude of velocity. Keywords: Unsteady Flow; MHD flow; second order fluid; slip parameters; Magneto Hydro Dynamic FlowWed, 30 Nov 2016 20:30:00 +0100Dynamic and Static Pull-in instability of electrostatically actuated nano/micro membranes under ...
http://jcamech.ut.ac.ir/article_60712_7900.html
In the current study the effect of Casimir force and squeezed film damping on the pull-in instability and dynamic behavior of electrostatically actuated nano and micro electromechanical systems is investigated separately. Linear elastic membrane theory is used to model the static and dynamic behavior of system for strip, annular and disk geometries. Squeezed film damping effect is modeled using nonlinear Reynolds equation. Both equation of motion and nonlinear Reynolds equation are first nondimensionalized then they are discretized and solved by means of finite element method. First static pull-in instability analysis is performed and validated by previous researches then dynamic pull-in values are investigated and compared with static pull-in parameters. In the next step the effect of squeezed film damping and ambient pressure and also Casimir force on the dynamic behavior of system is studied. Results shows significant effect of Casimir force and squeezed film damping on the system which is considerable for fabrication and design. Keywords: MEMS and NEMS, pull-in instability, squeezed film damping, Casimir force, linear elastic membrane, FEM Keywords: MEMS and NEMS, pull-in instability, squeezed film damping, Casimir force, linear elastic membrane, FEMWed, 30 Nov 2016 20:30:00 +0100Composite Adhesive-Bonded Joint Reinforcement by Incorporation of Nano-Alumina Particles
http://jcamech.ut.ac.ir/article_60713_7900.html
Adhesive bonding technology is being used in a variety of modern industries, including the automotive, aerospace, maritime, construction, defense and so on. On the other side, polymeric nano - composites attracted both academic and industrial interests in the past decades. The scope of this paper is experimental investigation on the effects of the addition of Alpha-alumina nanoparticles to the woven glass / epoxy composite and Araldite 2015 adhesive on the mechanical properties of the composite adhesive bonded joints. In this study, vacuum assisted resin transfer molding was used to fabricate experimental samples and to fabricate composite samples, 6 glass-fiber layers with a surface density of 200 g/m2 were used. The study of the influences of the addition of Alpha-alumina nanoparticles with different weight ratios to glass/epoxy composites suggests that the maximum values of the ultimate strength, elongation, toughness, and Young’s modulus belong to the samples with the weight ratios of 0.43, 1, 1, and 2.1%, respectively. The experimental results from the shear tensile test show that the incorporation of 0.74 wt% of nanoparticles to the adhesive increases the joint strength by about 14%.Wed, 30 Nov 2016 20:30:00 +0100Studying piezoelastic and piezomagnetoelastic configurations for different excitation ...
http://jcamech.ut.ac.ir/article_60714_7900.html
Typically, two configurations are used for energy harvesting, with different advantages: piezoelastic and piezomagnetoelastic. Best performance of piezoelastic configuration is limited to its narrow bandwidth around the resonance frequency. If the excitation frequency slightly deviates from the resonance frequency, the power-out is severely reduced. To overcome this, the piezomagnetoelastic has been introduced. This configuration can be used in non-resonant frequency for the generation of high power. This paper investigates the effects of frequency on the two mentioned configurations. The results of the study indicate that at high frequency, piezomagnetoelastic operation is better than the piezoelastic; but at low frequencies, this configuration has weakness. Typically, two configurations are used for energy harvesting, with different advantages: piezoelastic and piezomagnetoelastic. Best performance of piezoelastic configuration is limited to its narrow bandwidth around the resonance frequency. If the excitation frequency slightly deviates from the resonance frequency, the power-out is severely reduced. To overcome this, the piezomagnetoelastic has been introduced. This configuration can be used in non-resonant frequency for the generation of high power. This paper investigates the effects of frequency on the two mentioned configurations. The results of the study indicate that at high frequency, piezomagnetoelastic operation is better than the piezoelastic; but at low frequencies, this configuration has weakness.Wed, 30 Nov 2016 20:30:00 +0100Shape Design Optimization of Unimorph Piezoelectric Cantilever Energy Harvester
http://jcamech.ut.ac.ir/article_60715_7900.html
The most promising method for micro scale energy scavenging is via vibration energy harvesting which converts mechanical energy to electrical energy by the effect of coupling between electric fields and mechanical variables. Using piezoelectric cantilevers is the most common method for vibration energy harvesting. Changing the shape of the cantilevers can lead to changing the generated output voltage and power. In this work vibration energy harvesting via piezoelectric resonant unimorph cantilevers is studied and new design for obtaining more efficient piezoelectric energy harvester is suggested. This study provides comprehensive analysis of the output voltage relationships and deducing a considerable precise rule of thumb for calculating resonance frequency in cantilever-type unimorph piezoelectric energy harvesters using Rayleigh method. The analytical formula, is then analyzed using MATLAB and MATHEMATICA as well as finite element methods and verified by FEM simulation in ABAQUS. The analytical data was found to be very close to simulation data. A key finding is that among all the unimorph trapezoidal V-shaped cantilever beams with uniform thickness, the triangular tapered cantilever, can lead to highest resonance frequency and by increasing the ratio of the trapezoidal bases, the resonance frequency decreases. Also the possible analytical relations for a triangular cantilever beam are evaluated and the nearest exponentially tapered shape to triangular cantilever is proposed. These new findings provide guidelines on system parameters that can be manipulated for more efficient performance in different ambient source conditions.Wed, 30 Nov 2016 20:30:00 +0100Active control vibration of circular and rectangular plate with Quantitative Feedback Theory Method
http://jcamech.ut.ac.ir/article_60718_7900.html
Natural vibration analysis of plates represents an important issue in engineering applications. In this paper, a new and simplify method for vibration analysis of circular and rectangular plates is presented. The design of an effective robust controller, which consistently attenuates transverse vibration of the plate caused by an external disturbance force, is given. The dynamics of the plate is modeled as a distributed parameter system. We have studied the control vibration of the plate using quantitative feedback theory method by determining the transfer functions between various factors of control system. In this method we have developed the general distributed parameter system method for uncertainty problem for simply supported rectangular plate and clamped circular plate. The quantitative feedback method is one of the robust control methods which is capable to solve problems despite structural and non-structural uncertainty. Quantitative Feedback Theory introduces the new technique to design one-point feedback controllers for distributed parameter systems. The results demonstrate that the control law provided a signiﬁcant reduction in the plate vibration. The numerical simulation of the designed controller demonstrates that the QFT controller can consistently attenuate the vibration compared to a passive system.Wed, 30 Nov 2016 20:30:00 +0100