ADMT Journal
http://admt.iaumajlesi.ac.ir/
ADMT Journalendaily1Tue, 01 Mar 2022 00:00:00 +0330Tue, 01 Mar 2022 00:00:00 +0330Numerical and Experimental Static Bending Analysis of Composite Sandwich Panels with Grid-Stiffened Cores Before and After Transverse Impact Loading
http://admt.iaumajlesi.ac.ir/article_687311.html
Nowadays grid structures are considered as one of the most useful composites because of their various applications. Since grid structures are vulnerable to impact loads, they should be investigated under such loadings. The present paper studies the low-velocity impact loading of sandwich panels with grid-stiffened cores using both experimental and numerical simulations. In addition to the impact behaviour and the resultant damage of the sandwich panels, the behaviour of these structures under three-point bending was studied before and after the impact loading. The results were provided for impact and bending loadings separately. Then the effect of impact loadings on bending strength was investigated and it was found that the impact loading decreases the bending strength. A consistency between numerical and experimental results was also observed, which confirms the applicability of the Finite Element Method (FEM) in simulating the behaviour of such structures under impact and bending loads, while saving lots of time, efforts and costs.Micro Electropolishing of the MEMS Metallic Structures Fabricated by the Micro WEDM Process
http://admt.iaumajlesi.ac.ir/article_689636.html
In this study, the micro electro-polishing method was employed to improve the surface quality of microbeams machined by the micro WEDM method and to remove the recast layer. This approach changes the dimensions of the microbeams, as a result of the electrochemical corrosion, in addition to the elimination of the recast layer. To diminish the impact of this process on the dimensional deviation of the fabricated microbeams, the influence of the micro electro-polishing process parameters such as voltage, duration, cathode diameter, and electrolyte composition on the dimensional deviation of microbeams was studied using the Taguchi method. The optimum values of process parameters were determined by the S/N ratios analysis, and the order of parameters importance was determined through analysis of variance of the S/N ratios. It was found that the optimal levels of the process parameters are voltage of 2 V, process duration of 20 s, cathode diameter of 50 mm, and electrolyte composition of 25-5-40 ml (sulfuric-phosphoric-water) within the range of experiments. By using the optimum values of the parameters, the dimensional deviations were found to be 5.23 times lower compared to the average of the results.&nbsp; The importance of process parameters was found to follow this order: electropolishing duration, electrolyte composition, cathode diameter, and process voltage.Bending and Vibration Analysis of a Mindlin Rectangular Nanoplate using Modified Couple Stress Theory and Navier's Solution
http://admt.iaumajlesi.ac.ir/article_687318.html
In this paper, a Mindlin rectangular nanoplate model is developed for the bending and vibration analysis of a graphene nanoplate based on a modified couple stress theory. In order to consider the small scale effects, the modified couple stress theory, with one length scale parameter, is used. In modified couple stress theory, strain energy density is a function of strain tensor, curvature tensor, stress tensor and symmetric part of couple stress tensor. After obtaining the strain and kinetic energy, external work and substituting them in the Hamilton&rsquo;s principle, the main and auxiliary equations of the nanoplate are obtained. Then, by manipulating the boundary conditions the governing equations are solved using Navier approach for bending and vibration of the nanoplate. The bending rates and dimensionless bending values under uniform surface traction and sinusoidal load and different mode frequencies are all obtained for various plate's dimensional ratios and material length scale to thickness ratios. The effect of material length scale, length, width and thickness of the nanoplate on the bending and vibration ratios are investigated and the results are presented and discussed in details.The Application of the Extended Isogeometric Analysis (XIGA) with K-Refinement Approach for the Prediction of Fatigue Life in Linear Elastic Fracture Mechanic
http://admt.iaumajlesi.ac.ir/article_687319.html
This study investigates the fatigue life of a cracked plate subjected to cyclic load under linear elastic fracture mechanics, using a numerical method of extended isogeometric analysis (XIGA) with a K-refinement approach. XIGA is applied to simulate discontinuity problems without meshing and without the necessity for element boundaries to be aligned to crack faces. In this method, the crack faces are simulated by discontinuous Heaviside functions, whereas the singularity in the stress field at the crack tip is simulated by crack tip enrichment functions. The stress intensity factors for the cracks are numerically calculated using the interaction integral method. Paris law of fatigue crack growth is utilized for predicting the fatigue life of a cracked plate. In the standard finite element analysis, there is no refinement method similar to k-refinement. The effect of the k-refinement on the accuracy of the values stress intensity factor and fatigue life is investigated. To achieve this, the order of Non-uniform rational B-Splines (NURBS) basic function is considered as linear, quadratic, and cubic. It is observed that as NURBS orders are increased in k-refinement, results are improved, and the error is lower compared with the analytical solution. The results show that values of stress intensity factor and fatigue life obtained using XIGA are more accurate compared to those obtained by the finite element method. In addition, and they are closer to the results of the analytical solution, and the XIGA method is more efficient.Modeling and Simulation of 6DOF Robot Manipulators with Tactile Position-Force Control
http://admt.iaumajlesi.ac.ir/article_687315.html
In this paper, a joint position-force controller is used to control a 6R general-purpose robot manipulator. The manipulator comes into interaction with a spherical object in a numerically simulated environment. A controller has been implemented using the MATLAB Simulink software which uses the Simmechanics second-generation toolbox. A useful numerical contact model is used for modelling the interaction between the manipulator&rsquo;s end-effector and the environment which generates the interaction feedback forces. The control algorithm presented in this paper is developed in the Cartesian space and the original control algorithm was modified to satisfy the desired input position in the base coordinate frame. The control algorithm was verified using a virtual environment, before hardware implementation. The novelty of the controller is determining the input tactile forces for the robot without actually causing a collision between the end-effector and the object in the environment which can lead to fracture and damage to the environment or the manipulator. The modeling process of interaction with the spherical environment was investigated using Simmechanics to model precise mechanical characteristics of manipulator that are unknown to the designers and provide a great advantage in the simulation for them. The considered position and tactile force were tracked successfully with good accuracy. The results show that the proposed manipulator system controls the position and force with more than 95% accuracy and the accuracy of desired tracing trajectory is 99%.Characterization of DLC Thin Films Deposited by DC-Pulsed PACVD using Methane Precursor
http://admt.iaumajlesi.ac.ir/article_689935.html
In this work, Diamond Like Carbon (DLC) thin films were deposited on aluminum alloy 6061 by Plasma-Assisted Chemical Vapor Deposition (PACVD). Nitiding prior to coated leads to appropriate hardness gradient and it can greatly improve the mechanical properties of the coatings. The composition, crystalline structure and phase of the films were investigated by Grazing Incidence X-ray Diffraction (GIXRD). Atomic Force Microscopy (AFM) and Scanning Electron Microscopy (SEM) were employed to observe the morphology and structure of the film. The DLC layer exhibited a columnar structure. The adhesion force between the film and the aluminum alloy 6061 was 30.8 Mpa. The DLC film was determined by the pull of test. The hardness of the DLC film was 12.75 Gpa. The improvement of the adhesion DLC was attributed to a less gradient hardness configuration. In addition, the mean friction coefficient of the films was about 0.2 determined by nanoindentation test. According to the results, the high and unique hardness of this coating leads to increase of the wear resistance and thus the useful life of parts.Modelling and Control of Mutation Dynamics of the Cancer Cells Employing Chemotherapy
http://admt.iaumajlesi.ac.ir/article_687317.html
In this paper, the analytic model of the mutation dynamics related to the cancer cells which is under the control of chemotherapy is developed and its corresponding metastasis is controlled using chemotherapy method.&nbsp; The progress of a cancer tumours is contributed to two main factors including metastasis and mutation. It is observed that controlling the metastasis dynamic without considering the mutation phenomenon is doomed to fail. In this paper, the mathematical model of the cancer dynamic is improved considering the mutation of the stem cells and the effect of chemotherapy injection as the corresponding controlling signal is investigated in the extracted state space. Controlling the cancer growth and its mutation process is accomplished here using PID controller and State Feedback Control (SVFC) method. It is shown that by the aid of the proposed model of this paper, not only the number of the cancer cells can be converted to zero, but also the mutation process can be blocked since the feedback of the mutated cells are also engaged in the state space of the system. Verification of the model is conducted by the aid of simulation in the MATLAB and comparing the results with previous studies.Effect of CaCO3 Nanoparticles on Vibrational Damping Behavior and Static Mechanical Properties of Polypropylene Composite Plates: An Experimental Investigation
http://admt.iaumajlesi.ac.ir/article_689939.html
In this research, the effect of CaCO3 nanoparticles was experimentally investigated on vibrational damping behavior and static mechanical properties of polypropylene (PP). Hammer tests along with modal analysis were carried out to evaluate the forced vibration behavior of composite plates under &nbsp;one edge clamped support conditions while tensile tests were performed to assess the static mechanical properties. A comparison of the results showed an increment in the static mechanical properties of nanocomposites by increasing the nanoparticles content in the PP matrix. Composite with 10 wt.% nanoparticles showed the highest rise in Young&rsquo;s modulus (39.71 %) compared to pure PP. An increment in Young&rsquo;s modulus and stiffness led to an increasing trend in the damped natural frequencies of the nanocomposites so that the composite with 10 wt. % nanoparticles showed the highest damped natural frequency augmentation (23.6 %, 36.78 %, and 252.62 %) compared to pure PP in the first three modes. In addition, an enhancement in the nanoparticles content of the PP matrix led to an increasing trend in damping ratios of the nanocomposites such that the composite with 10 wt. % nanoparticles in the first mode (28.99 %) and composite with 7.5 wt. % nanoparticles in the second and third modes (418.66 % and 9.93 %) showed the highest rise in damping ratio compared to pure PP. Increasing damping ratios can be due to the proper dispersion of nanoparticles in the matrix and consequently energy dissipation of the stick-slip mechanism between the matrix and nanoparticles. Moreover, high nanoparticle contents had destructive effects on both the static and dynamic behavior of the composites.Evaluating the Effect of the Second Invariant of Deformation Tensor in The Axial and Azimuthal Shear Deformations
http://admt.iaumajlesi.ac.ir/article_687299.html
The purpose of the present paper is to investigate the effect of the second invariant of the deformation tensor on the axial and azimuthal shear deformation of an incompressible hyperelastic solid with various strain energy functions. To this end, the axial shear deformation of an incompressible cylinder with the modified Gent-Thomas, Gent-Thomas, Gent-Gent, and Carroll strain energies subjected to an axial shear traction is considered, where the displacement field is determined analytically for the first three models and numerically for the fourth model. The phenomenon of strain hardening at large elastic deformations, predicted either by the limiting chain extensibility condition for the modified Gent-Thomas and Gent-Gent models or phenomenologically by the Carroll model, is observed and it is shown that the second invariant of deformation increases the strain hardening experienced by such materials. Next, the azimuthal shear deformation of an incompressible annular wedge with the modified Gent-Thomas, Gent-Thomas, Gent-Gent, and Carroll models is considered, where the annular wedge is subjected to a controllable azimuthal shear deformation and the angular displacement is determined analytically for all the above models. Again, the second invariant of the deformation tensor is shown to have a significant effect on the azimuthal shear deformation as reflected in the increase of the strain hardening of the material in such deformation. In addition, the annular wedge with the modified Gent-Thomas and Carroll models is shown to have a higher resistance in azimuthal shear deformation than the other models mentioned above.Weld Distortion and Residual Stresses in Aluminum Hollow Section T-Joint
http://admt.iaumajlesi.ac.ir/article_689943.html
Welding is known as one of the most popular attaching methods for different hollow section components. However, local concentrated heating, distortion, and residual stresses at welded joints are unavoidable. In this article, the welding simulation for rectangular hollow (RHS) sections for the front axle carrier of the new BMW series-7 is discussed and weld distortion and residual stresses in its aluminum T-joint for one proposed sequence are investigated. Comparisons of the results of this paper for this recommended sequence with experimental results in some references show good agreement and indicate that characteristics of the welding distortions are fully forecasted. In the following of this paper, the Finite Element Method (FEM) is used to offer a better sequence with smaller weld distortion and residual stresses. Weld distortion and residual stresses are highly influenced by welding strategy. In the proposed strategy, the needed time to perform the welding process decreased, and the total weld distortion and residual stresses decreased by 24% and 4%, respectively.Numerical Simulation of Hot Forging Process of KIA Car Brake’s Output Shaft
http://admt.iaumajlesi.ac.ir/article_689937.html
The present study investigates the production process by closed die forging method of one of the sensitive and safe parts of KIA car brake, which is affected by various mechanical and thermal stresses in its operating conditions; therefore, in the present research, the application of this forming method in the Iranian automotive industry has been discussed. In this study, an attempt was made using finite element analysis in ABAQUS software to determine the maximum force required for forging this part. In addition, the influence of various parameters such as the temperature of the part during the forming process, the coefficient of friction between the part and the die, as well as the strain rate have been investigated. The results indicated that the friction coefficient has a significant effect on the maximum required force, and the maximum values of the load increase with increasing the friction coefficient; but the remarkable result is that the effect of this coefficient is negligible from a value onwards. This point is consistent with the observations in practice. Besides, a strong dependence of the results on the loading speed was observed, and the required force has increased with increasing loading speed for reasons such as the strain hardening phenomenon. Also, the force required for forging has decreased with increasing the temperature, which is due to reduced material strength. This reduction from 900&deg;C to 1000&deg;C is less than 2%, while it is approximately 40% from 1000&deg;C to 1100&deg;C, which is consistent with the experimental reports.Optimization of Location and Stiffness of an Intermediate Support to Maximize the First Natural Frequency of a Beam with Tip Mass-With Application
http://admt.iaumajlesi.ac.ir/article_689938.html
The optimal position and minimum stiffness of an intermediate support is implemented to maximize the fundamental natural frequency of a vibrating cantilever Euler-Bernoulli beam with tip mass. According to Courant&rsquo;s maximum-minimum theorem, maximum value of the first natural frequency of a beam with a single additional rigid internal support, is equal to the second natural frequency of the unsupported beam. In literature, for a cantilever beam without tip mass, the optimum position of intermediate support was reported as 0.7834L and minimum dimensionless stuffiness as 266.9. In this paper, the effect of tip mass ratio on optimum location and minimum stiffness is investigated. The Finite element method is employed. Cross sectional area is uniform and material is homogeneous and isotropic. Numerical results demonstrate that as tip mass ratio increases the optimal position moves toward the tip mass and minimum stiffness increases. For instance, for tip mass ratio 0.5, optimal position is 0.92L and minimum dimensionless stiffness is 284. Optimal position and minimum stiffness are presented for various range of mass ratio. In many applications, it is not possible to place intermediate support at optimal position; therefore, the minimum stiffness does not exist. In these cases, a tolerances zone is considered and related design curves are proposed. As a practical example, an agitator shaft is considered and end impeller is modeled as tip mass. The effectiveness of the proposed design curves in order to maximize natural frequency is shown. A design of an intermediate support is presented; in this example the fundamental frequency has increased as much as 300 percent without any change in shaft diameter.Dimensional and Geometrical Tolerance Analysis of Two Flexible Curved Sheet Metal Parts Assembly
http://admt.iaumajlesi.ac.ir/article_689941.html
Sheet metal assemblies are widely used in the automobile, aerospace, and shipbuilding industries. Sheet metals deform during the manufacturing and assembly process due to their high flexibility. Traditional tolerance analysis approaches were developed for rigid assemblies; however, new approaches of tolerance analysis and variation simulations have been proposed for flexible (compliant) assemblies using FEM. In this paper, a new method called Interactive Worst Case (IWC) is introduced for tolerance analysis of flexible assemblies, which demands a few FEM simulations and is based on traditional Worst Case (WC) method. IWC method guarantees that all the parts will assemble accurately and have proper function. The case study of this paper is two flexible sheets in the form of quarter cylinders, joined together by six spot welding to form a half-cylinder assembly. The accuracy of IWC is verified by comparing the results to uniform MIC. The results of MIC are also compared to the results of the Monte-Carlo simulation (MCS).&nbsp;Mechanical Properties of Materially and Geometrically Gradient Cellular Structures Manufactured with SLS 3D Printer Applicable as a Bone Implant
http://admt.iaumajlesi.ac.ir/article_689936.html
Cellular structures are broadly used because of their exclusive properties in tissue engineering. This research proposes a new method, both in design and manufacturing, to engineer their mechanical properties considering gradient material and geometrical features and evaluate the possibility of using created structures as bone implants. Schwarz-primitive surface has been utilized to design cellular structures with different porosities and unit cell sizes. A total of 18 cellular structures were designed and fabricated using the SLS 3D printer with a new unconventional approach in adjusting the settings of the machine, and their mechanical properties were extracted. The structures' internal properties were evaluated using the FESEM. Comparing the mechanical compressive test results showed that adjustments in material and geometry improved mechanical properties (such as the compressive moduli, compressive strength, and yield strength). For instance, in 3 mm samples, the elastic modulus in material gradient and geometrical gradient structures is 20% and 73 % higher than the minimum values of the uniform structure. FESEM imaging revealed that adjusting the absorbed energy by powders (controlled by laser characteristics) leads to the formation of natural voids with diameters in the range of 6 to 144 &mu;m for the gradient structures. Evaluation of the designed structures showed that 6 of them (4 uniform porosity and 2 geometrically gradient) have mechanical behavior of the desired tissue. The research outcomes can assist in optimizing manufactured parts by SLS 3D printers with internal and external controlled properties to obtain more desirable mechanical characteristics, especially for tissue engineering applications.Analysis of time–varying mesh stiffness for the planetary gear system with analytical and finite element methods
http://admt.iaumajlesi.ac.ir/article_687312.html
In dynamic model of planetary gears, one of the key design parameters and one of the main sources of vibration is time&ndash;varying mesh stiffness of meshing gears. According to previous researches, the finite element method and analytical method are two techniques to estimate the mesh stiffness of meshing gears. In this work, in an innovation the periodically time&ndash;varying mesh stiffness of meshing gears is examined by both of finite element and analytical methods. The planetary gear set is modeled as a set of lumped masses and springs. Each element such as sun gear, carrier, ring gear and planets possesses three degrees of freedom and is considered as rigid body. The influence of effective parameters on the mesh stiffness of meshing gears and also numerical results of natural frequencies and vibration modes of the system are obtained. Based on the results, the influence of the higher pressure angles on the mesh stiffness of meshing gears is perceptible. By using the proposed mesh stiffness of meshing gears, for the system with numbers of odd and even equally and unequally spaced planets, natural frequencies and vibration modes are validated with a high accuracy.Frequency Analysis of Ring-Stiffened Composite Cylindrical Shells Using Experimental, Analytical and Finite Element Methods
http://admt.iaumajlesi.ac.ir/article_687313.html
In this paper, free vibration of laminated composite cylindrical shells reinforced with circumferential rings, are investigated with experimental, analytical and finite element methods and natural frequencies are obtained. The analysis is carried out for clamp-free and clamp-clamp boundary conditions and the results are compared with each other. To solve the problem, the equilibrium equations of motions are written according to the classical shells theory and after simplification, the structural stiffness and mass matrices and the frequency equation are derived using Galerkin method. The results obtained in this paper, are compared with the results available in the literatures, and the results of experimental and finite element methods and good agreement is observed.Fabrication, Testing and Analysis of Composite Lattice Panels Under Three-Point Bending Load
http://admt.iaumajlesi.ac.ir/article_687314.html
Thanks to their high strength-to-weight ratio, lightweightness, and excellent energy absorption, composite lattice panels can be used in the aerospace, marine, automotive, and other industries. These structures can be used as an alternative to string-reinforced structures, honeycomb (core) sandwich panels, and aluminum grid structures. In this paper, a composite lattice panel is first fabricated from glass/epoxy by hand lay-up method using a silicon rubber mold. In this method, a Kagome composite lattice panel with twelve layers of resin-impregnated fibers was fabricated during a continuous process. After fabrication, the test panel was shown under three-point bending and failure modes. Also, a numerical simulation of three-point bending was performed in ABAQUS software. Then, the simulation results were compared with those of the experimental test, indicating a good convergence between the experimental test results and the finite element ones up to the point of failure. Due to changes in directions of force, these structures have a high ability to withstand damage, and therefore, continue to withstand the load after the failure of one or more ribs. Also, there is no sudden and sharp drop in the load-bearing capacity of the structure despite the force being maximized, which can be attributed to the high energy absorption of such structures. Instead, the force decreases slowly with fluctuations, and the structure continues to absorb energy until final failure. Therefore, such lightweight structures can be used in applications where energy absorption is of great importance.Dynamic response of FGM plates under blast load
http://admt.iaumajlesi.ac.ir/article_687316.html
The present study investigates the deformation of FGM plates under blast load. Hamilton's principle is used to obtain the dynamic equations. The two constituent phases, ceramic and metal, vary across the wall thickness according to a prescribed power law. Boundary conditions are assumed to be simply supported (SS). The type of explosive loading considered is a free in-air spherical air burst and creates a spherical shock wave which travels radially outward in all directions. For pressure-time of the explosion loading, Friedlander&rsquo;s exponential relation has been used. In order to determine the response analytically, the stress potential field function is considered. Using the Galerkin method, the final equations are obtained as nonlinear and nonhomogeneous second order differential equations. The effect of temperature including thermal stress resultants and different parameters on the dynamic response have been investigated. Results have been compared with references and validated. Results showd that the amplitude of center point deflection of the FGM plate is less than the pure metal plates when exposed to blast load, by increasing the volumetric index percentage of FGM, center point deflection is increased and in the FGM plates, deformation of symmetrical plates is smaller than the asymmetric plates. Also by applying the damping coefficient of the FGM plates, the amplitude of center point deflection is reduced, and by increasing the aspect ratio of the FGM plate, its center point deflection against explosion waves reduces and consideration the effects of thermal resultant forces and moments, center point deflection is increased.Leaching of metals from dental silveralloy wastes
http://admt.iaumajlesi.ac.ir/article_689944.html
Environmental issues of hazardous metal wastes as well as growing demand for metals has increased focus on the forthcoming provision of metals. Therefore, the recovery and recycling processes of precious metals from secondary resources have become more prominent in the last years. Silver is one of the precious metals which can be recovered from wastes such as electronic wastes, coin and medal production losses, photographic films, and dental filling materials known as amalgam, which has the highest silver content. The present paper investigates the acid leaching of metals from a waste sample of dental silver alloy generated during the melt spray process. The alloy constitutes is 42.13% Ag, 31.03% Sn, and 26.84 Cu. The phase composition of amalgam generally consists of Ag2Hg3, Ag3Sn, SnxHg, Cu6Sn5, and Cu3Sn. The effects of the system temperature (25-80&deg;C), nitric acid concentration as the leachate (13.75-65%), pulp density (33-200 g/l), and reaction time (0-240 min) on the dissolution recovery of silver, copper, and tin have been investigated. In the best case, we recovered 100% of silver and 98% of copper as soluble nitrates while tin was isolated as solid stannic oxide.Magnetic Field Effect on Ferro-Nanofluid Heat Transfer in a Shell and Tube Heat Exchanger with Seven Twisted Oval Tubes
http://admt.iaumajlesi.ac.ir/article_689945.html
This article investigates the effect of magnetic field on the performance of a special shell-and-tube heat exchanger using ferro-nanofluid. The heat exchanger comprises seven twisted oval tubes with triangular array mounted on a hexagonal cross section. Water/iron oxide nanofluid with a volume ratio of 4% is used as hot fluid in tubes and water is employed as cooling fluid in the shell. The flow regime is laminar and calculations are performed at different Reynolds numbers and various magnetic fields. The governing equations include continuum, momentum, energy, and magnetic field equations that are solved using a finite volume method. It is demonstrated that the wall temperature of the tubes at the output is lower when the magnetic field is present compared to the case in which the magnetic field is not applied. Applying the magnetic field to the ferro-nanofluid leads to an increase in the Nusselt Number by about two times, leading to an increase in thermal efficiency of the heat exchanger. Also, the effect of the magnetic field was quite different with respect to the geometry and position of the tubes relative to the flow field. The effect of increasing the Nu in the first half of the twisting of the tube is approximately equal to the rate of reduction in the second half of the tube, resulting in a reduction in the impact of the magnetic field intensity.Behaviour of Lightweight Smart Sandwich Panels Subjected to Tensile and Bending Loads- An Experimental Study
http://admt.iaumajlesi.ac.ir/article_689947.html
In this research work, sandwich composite panels made by fiber metal laminate (FML) as the facesheets and polymer foams as the core material are investigated in tensile and bending loads. To change or enhance the behaviour of sandwich panels in tensile and bending loads, shape memory alloy wires with pseudoelastic behaviour are also embedded in between FML layers in facesheets. The shape memory wires are also pre-strained in the FML facesheets of sandwich panels. To study the tensile and flexural properties of sandwich panels with smart FML facesheets three types of sandwich panels are considered and made including panels without shape memory alloy wire, panels with shape memory wires with 0% tensile pre-strain, and panels with shape memory wires with 5% tensile pre-strain for the same cross section. By placing SMA wires in the FML, the strength and stiffness of the smart sandwich specimens are increased significantly in tensile and bending loads. But, the effect of pre-straining the SMA wires is more predominant on stiffness of the specimens. The tensile and flexural toughness or energy absorption is much higher in case of the specimen with 5% pre-strained SMA wires. At the expenses of adding the SMA wires in the sandwich structures, the densities of various specimens are changed by nearly 1% to 5% for various specimens, but a significant increase in mechanical properties such as the strength and particularly the stiffness and toughness were achieved by the present lightweight smart sandwich structures.Redesign and Accuracy Improvement of Disposable Infusion Pumps
http://admt.iaumajlesi.ac.ir/article_689948.html
Nowadays, disposable injection pumps are widely used in hospitals and home care settings to provide various therapies such as chemotherapy, antimicrobial, analgesic, and anesthetic treatments, as well as for postoperative pain control and chronic pain control. Since the accuracy of the injection is very important in infusion pumps based on the flow rate, it is therefore important to reduce the error in this device. In this study, the basic design principles of these pumps and the design problems of the sample appearance available in the market was investigated. Since one of the vital problems of this type of pump is their inaccuracy, because they are unable to inject a certain amount of drug for a certain period of time, so one of the main objectives of this study is to improve the accuracy of the injection. Pump Type Also, as this device is available to the patient for a long time at the time of injection, ease of use is one of the design goals. Finally, this paper ends with a design and prototype which is better in the shape of the device and a big improvement in the accuracy.Stability Enhancement of In-Wheel-Motor Drive Electric Vehicle Using Adaptive Sliding Mode Control
http://admt.iaumajlesi.ac.ir/article_689949.html
A multi-layer controller of direct yaw moment for electric vehicles is developed in this study. In the upper layer, the yaw moment are obtained using Adaptive Sliding Mode Control (ASMC) with adaptation gain to track the desired vehicle yaw rate. The corrective yaw moments are applied by four in-wheel electric motors. The lower layer controller consists of a torque distribution algorithm and in-wheel motor torque controllers as well. The proposed torque distribution algorithm is intended to distribute the reference torques of each in-wheel motor controller appropriately based on both total longitudinal force and corrective yaw moment. To elucidate the effectiveness and robustness and of the above control method, the simulation under various manoeuvres was carried out. A 7-DOF non-linear vehicle model is used for simulations and their results signify that the proposed control algorithm accomplishes a proper distribution of longitudinal force among four individual wheels, in turn, enhancing the yaw stability of the vehicle.Numerical study of the flow field and heat transfer of a non-Newtonian magnetic nanofluid in a vertical channel affected by a magnetic field
http://admt.iaumajlesi.ac.ir/article_689950.html
The present paper examines thermal and hydrodynamic behavior of the incompressible laminar flow of a non-Newtonian magnetic nanofluid in a vertical rectangular channel numerically using two-phase mixture model, Carreau model, and finite volume method. The non-uniform transverse magnetic field is created by an electric current-carrying wire located along the channel. The Schiller-Naumann model is employed to calculate the slip velocity between the solid and liquid phases. The flow pattern and nanofluid temperature is assessed by changing effective parameters such as Reynolds number, the magnetic field strength, flow rate, mean axial temperature, and channel heat transfer. It is observed that the transverse secondary flow increases by increasing the magnetic strength due to Kelvin force. The hot fluid is transferred more from the sidewall to the center of the channel and the cold fluid moves from the center of the channel towards the wall, leading to an increase in heat transfer. Also, at low Reynolds numbers, more fluctuations occur in the velocity profile due to the dominance of Kelvin force over inertial force.Investigation effect of adding a Styrene-butadiene rubber damper to a sled sample and extraction of its equivalent stiffness and damping
http://admt.iaumajlesi.ac.ir/article_689951.html
Protection of sled systems from destructive vibrations is inevitably under attraction due to the importance of sled testing in the aerospace industry. A pair of SBR dampers were used between the slipper and the sled body to reduce vertical vibrations, so a design of the sled model was studied. Both equivalent stiffness and equivalent damping of the sled system were obtained to reduce the transmission of vibrations from slippers to the body. A combination of analytical, numerical, and experimental test methods was utilized and the results were validated. The stiffness values of 370500 and 391000 N&frasl;m were obtained from numerical and experimental measurements, respectively. Finally, by designing the sled model, first and second natural frequencies of 12.49 and 19.56 Hz and mode shapes of the sled system were obtained. The results show that the dampers used in the sled have an important role in reducing the transmission of vibrations to the sled body by withstanding the tension and pressure on the slippers.FA-ABC: A novel combination of firefly optimization algorithm and artificial bee colony for mathematical test functions and real-world problems
http://admt.iaumajlesi.ac.ir/article_689952.html
In this research study, an attempt is made to present a new optimization scheme by combination of the firefly algorithm and artificial bee colony (FA-ABC) to solve mathematical test functions and real-world problems as best as possible. In this regard, the main operators of the two meta-heuristic algorithms are employed and combined to utilize both advantages. The results are compared with those of five prominent well-known approaches on sixteen benchmark functions. Moreover, thermodynamic, economic and environmental modeling of a thermal power plant known as the CGAM problem is represented. The proposed FA-ABC algorithm is used to reduce the total cost and increase the efficiency of the system as shown in the Pareto front diagrams.A New Visual Servoing method for grasping and assembling objects Using Stereo Image Based Feedback
http://admt.iaumajlesi.ac.ir/article_689955.html
In this paper, an eye-in-hand stereo image-based visual serving controller for industrial 6 degrees of freedom manipulator robots is presented. The visual control algorithms mostly use the relationship between camera speed and changes in image features, to determine the end-effector movement path. One of the main problems of the classical IBVS method is the inability to estimate the distance of the object related to the camera, which requires peripheral equipment such as a laser rangefinder to estimate the depth. In this study, considered two cameras were mounted on the end-effector of a 6 DOF manipulator robot. The distance of the object to the camera is estimated by the equations associated with the epipolar plane, and the interaction matrix is updated at any time. For increasing response speed, the image interaction matrix was divided into two separate parts related to translational and rotational motion, and it was found that only the translational motion part is affected by distance. The control method separates the camera motion into three-stage based on pure rotation, pure translation, and hybrid motion, which has a better time response compared to the classical IBVS control methods. Additionally, a method for position prediction and trajectory estimation of the moving target in order to use in a real-time grasping task is proposed and developed using Recursive Least Square as the trajectory estimators in the image plane. The simulation results show that the proposed method increases the system response speed and improves the tracking performance.Mass and Stiffness Matrices and Frequencies of Simple Beam Elements Based on Real Shape Functions
http://admt.iaumajlesi.ac.ir/article_690965.html
In this research we investigate and compare the natural frequency values of simple beams and their mass and stiffness matrices of the two methods; classic shape functions and real shape functions, which are achieved by solving the beam motion equation and applying boundary conditions. The frequency values obtained from the two methods above are compared with the exact frequency values of two simple beam types with different support conditions to determine which method leads us to more accurate and acceptable frequencies for these beams. It can be seen that the percentage of frequency error obtained by the classical method is relatively high in the sample beams. Hence, the natural frequency value of the beams studied, using their exact shape functions, shows little error compared to the classical method with respect to the exact frequency value of these beams. It should be noted that the frequency error obtained from the classical method is greater in the elements with higher natural frequency. The importance of obtaining the exact natural frequency of an element will result in accurate dynamic responses and more appropriate analysis and design.