Mechanics of Advanced Composite StructuresMechanics of Advanced Composite Structures
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Feed provided by Mechanics of Advanced Composite Structures. Click to visit.Investigation of Hardness, Morphology and Structural Analysis of NiCrBSi Composite Coating on ...
https://macs.semnan.ac.ir/article_3625_455.html
High velocity oxy-fuel (HVOF) is one of the emerging technologies among the thermal spraying techniques, for producing uniform and dense coatings, having high hardness and very low porosity. A NiCrBSi alloy coating was prepared with approximately 400µm thick, on the A516 steel by means of HVOF and was analyzed with regard to its detailed microstructures, phase formation, thickness, roughness and microhardness. The obtained coating was crack-free, mechanically bonded to the substrate and had very low porosity. A microhardness tester was used so as to determine the mechanical properties of the coating. The microstructure of the coating and its phase transformations was characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD) and energy dispersive spectroscopy (EDS), respectively. The major crystalline phases involve Cr3NiB6, Ni31Si12, Ni4B3, Ni3B compounds and Ni-γ solid solution. Also, amorphous phase was obtained in the coating. The results indicated that coating microhardness values were in the range of 700-800 Hv and a uniform distribution of different elements was observed.Thu, 31 Oct 2019 20:30:00 +0100Fluid-Structure Interaction of Vibrating Composite Piezoelectric Plates using exponential shear ...
https://macs.semnan.ac.ir/article_3645_0.html
In this paper fluid-structure interaction of vibrating composite piezoelectric plates is investigated. Since the plate is assumed to be moderately thick, rotary inertia effects and transverse shear deformation effects are considered by using exponential shear deformation theory. Fluid velocity potential is obtained using the Laplace equation and fluid boundary conditions and wet dynamic modal functions of the plate are expanded in terms of finite Fourier series to satisfy compatibility along the interface between plate and fluid. The electric potential is assumed to have a cosine distribution along the thickness of the plate in order to satisfy the Maxwell equation. After deriving the governing equations using Hamilton’s principle, the natural frequencies of the fluid-structure system with simply supported boundary condition are calculated using the Galerkin method. The model is compared with the available results in the literature and then the effects of different variables such as depth of fluid, the width of fluid, plate thickness and aspect ratio on natural frequencies and mode shapes are illustrated.Thu, 24 Jan 2019 20:30:00 +0100Transient Thermal Stresses Analysis in a FPGM Cylinder
https://macs.semnan.ac.ir/article_3774_455.html
The present study aims to investigate the analysis of stress, strain, displacement, and electrical potential of a thick hollow cylinder made of FGPM under mechanical and thermal loads. Distribution of mechanical property of material is considered along the shell stick through the power distribution function. Thermal loads have been taken to signify the difference of temperature between outer and inner surfaces for each type of mechanical property. After extracting and solving the differential equations in transient state and the observation of mechanical and thermal boundary conditions, governing functions are obtained through the following parameters: thermal conduction non-homogeneous parameters, thermal linear distribution coefficient, elastic stiffness constant, piezo-electric coefficient, and dielectric constants.Thu, 31 Oct 2019 20:30:00 +0100Elasto-Thermodiffusive Response in a Two-Dimensional Transversely Isotropic Medium
https://macs.semnan.ac.ir/article_3289_455.html
The present article investigates the elasto-thermodiffusive interactions in a transversely isotropic elastic medium in the context of thermoelasticity with one relaxation time parameter and two relation time parameters. The resulting non-dimensional coupled equations are applied to a specific problem of a half-space in which the surface is free of tractions and is subjected to time-dependent thermal and chemical loadings. The analytical expressions for the displacement components, stresses, temperature, strain, mass diffusion, and chemical potential are obtained in the physical domain by employing the normal mode analysis as a tool. These expressions are calculated for a copper-like material and the results are depicted graphically. A comparative study of a diffusive medium and a thermoelastic medium show that diffusion has a significant effect on the thermophysical quantities. Furthermore, in the absence of the effect of thermodiffusion, the results agree with the existing literature.Thu, 31 Oct 2019 20:30:00 +0100Discrepancies Between Free Vibration of FML and Composite Cylindrical Shells Reinforced by CNTs
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In this study, discrepancies between the free vibration of fiber-metal laminate (FML) and composite cylindrical shells reinforced by carbon nanotubes (CNTs) based on Love’s first approximation shell theory have been considered by beam modal function model. The representative volume elements consist of three and four phases for composite and FML structures, respectively, which include fiber, CNTs, polymer matrix and metal for FML cylindrical shells while the metal section is ignored for composite cylindrical shells. The modulus of carbon nanotubes reinforced composites cylindrical shell could be defined based on rule of mixture. In addition, the fiber phase can be reinforced by the obtained matrix using the extended rule of mixture. The frequencies of FML and composite cylindrical shells reinforced by CNTs have been compared to each other for different materials, lay-ups, boundary conditions, axial and circumferential wave numbers.Thu, 31 Oct 2019 20:30:00 +0100Analytical Approach for Thermo-electro-mechanical Vibration of Piezoelectric Nanoplates Resting ...
https://macs.semnan.ac.ir/article_3646_455.html
In the present work, thermo-electro vibration of the piezoelectric nanoplates resting on the elastic foundations using nonlocal elasticity theory are considered. In-plane and transverse displacements of the nanoplate have been approximated by six different modified shear deformation plate theories considering transverse shear deformation effects and rotary inertia. Moreover, two new distributions of transverse shear stress along the thickness of the nanoplate were introduced for the first time. The equations of motion were derived by implementing Hamilton’s principle and solved using analytical method for various boundary conditions including SSSS, CSSS, CSCS, CCSS and CCCC. Based on a comparison with the previously published results, the accuracy of the results was confirmed. Finally, the effects of different parameters such as boundary conditions, variations of the thickness to length ratio, aspect ratio, increasing temperature, external voltage, foundation coefficients and length scale on the natural frequency of the plate were shown and discussed in details.Thu, 31 Oct 2019 20:30:00 +0100Vibration Analysis of Circular Single-Layer Graphene Sheet Using Finite Element Method
https://macs.semnan.ac.ir/article_3796_455.html
Graphene sheets are combined of Honeycombs lattice carbon-carbon bonds which have high natural frequencies, high strength, and high conductivity. Due to important applications of the graphene sheets particularly at higher frequencies, the study of their dynamic behavior is important in this frequency range. From Molecular Dynamics (MD) point of view as the dimensions of graphene sheet incline, the number of atoms increases, and as a result, its modeling becomes more time-consuming. Besides the experimental methods in small dimensions are difficult to conduct and not economical. In this research Finite Element Method (FEM) is used for frequency analysis of graphene sheets in various dimensions in order to study the capability of FEM in simulating the dynamic behavior of graphene sheets at small scales. In this research, the objective function is to find the minimum size of the sheet in which both methods have good convergence. Also, the time-consuming for the simulation is investigated. The time-consuming for analysis in the Finite Element Method is less than other methods, including Molecular Dynamics (MD), Generalized Differential Quadrature (GDQ), etc. Also, The results indicated that for circular single-layer graphene sheets simulation, using Finite Element Method (FEM) is in good agreement with the results obtained from the Molecular Dynamics (MD) simulation, in the radius more than 100 nm. In this research, the ABAQUS has been used for Finite Element Method (FEM) simulation.Thu, 31 Oct 2019 20:30:00 +0100Effect of Aging on Fracture Toughness of Al6061-Graphite Particulate Composites
https://macs.semnan.ac.ir/article_3784_455.html
This article presents the investigative work conducted on the fracture toughness and microstructure of Al6061-9% graphite particulate composites. The requisite specimens for the fracture toughness testing were compact tension ones prepared using stir casting technique. The Al6061-9% graphite particulate metal matrix composite has been heat treated in the underaged condition. It is observed from the results that as aging time increases, the fracture toughness increases. This gain in fracture toughness is with the loss of ductility. Examination of the fractured surface of Al6061-graphite is done using a scanning electron microscope (SEM) which shows the brittle fracture of the composite.Thu, 31 Oct 2019 20:30:00 +0100Nonlocal Analysis of Longitudinal Dynamic Behavior of Nanobars with Surface Energy Effect
https://macs.semnan.ac.ir/article_3779_455.html
Due to considerable stored energy in surfaces of nano-scales in comparison with the stored energy in their bulk, considering the surface energy is necessary for the analysis of various behaviors of nano-scales for more precise design and manufacturing. In this article, the longitudinal dynamic behavior of nanobars in the presence of the surface energy parameters is studied. To this end, the longitudinal dynamic behavior of nanobars is modeled based on the simple theory. To consider the effects of the surface energy parameters, the surface elasticity theory is used. In addition, the nonlocal elasticity theory is implemented to capture the size effect. Then, the governing equation of motion and corresponding boundary conditions are derived from Hamilton’s principle. The governing equation becomes the inhomogeneous cause of considering the surface energy parameters while in none of the previous researches like the investigation of transverse vibration of nanobeams and torsional vibration of nanobars, the surface energy parameters would not cause inhomogeneity of the governing equation. Due to inhomogeneity of the governing equation, the homogeneous case is firstly solved, and frequencies and mode shapes of nanobar are obtained for fixed-fixed and fixed-free boundary conditions. Then, using the modal analysis method and Duhamel’s integral, the inhomogeneous governing equation of motion is solved, and the overall dynamic response of nanobar is reported.Mon, 29 Nov 1999 20:30:00 +0100The Role of Natural Additives on the Wear and Friction Proper-ties of Nanocomposites for ...
https://macs.semnan.ac.ir/article_3783_455.html
In the present study, the effect of banana peel and bagasse particle additives on the friction and wear behavior of multi-ingredient friction material nanocomposites have been investigated. In order to develop optimized properties of friction nanocomposite, the type and content of natural additives were changed beside the constant amount of other constituents such as alumina nanoparticle and other functional ingredients. The microstructural investigation and wear test were performed. The results showed as the natural additive content increases, the density of nanocomposite, and the hardness decrease. The highest hardness and friction values and the lowest specific wear rate would be achieved for a composite sample with 5 wt. % of baggase additive.Thu, 31 Oct 2019 20:30:00 +0100Thermoelastic Analysis of Compressor Spool in Turbojet Engine and Redesign it Using ...
https://macs.semnan.ac.ir/article_3786_455.html
In this article, an exact analysis of compressors spool in a turbojet engine has been investigated. The spool is modeled as a rotating thick-walled hollow circular cylinder with free-clamp ends. It is subjected to centrifugal load due to its constant rotational speed, uniform internal and external radial loads and arbitrary thermal gradients. The analysis is initially investigated for the homogeneous state. Then FGM state is investigated to improve the safety factor of the spool. In order to calculate the safety factor, Von-Mises criterion has been used. In FGM state, thermoelastic properties of material would vary in radial direction. The function of these properties changes is assumed exponential. To obtain the highest safety factor, the numerical optimization method has been used and the optimal results have been compared with the homogeneous state. To drive the relations for free-clamp ends boundary condition, at first spool is considered clamp-clamp ends. Then, the effect of releasing one of the ends has been calculated and finally, using the principle of superposition, the results for clamp-free ends state has been investigated. In addition, the effect of changing the non-homogeneous coefficients, spool rotating speed, radial loads and thickness on the safety factor are investigated. Increasing the thickness and radial loads would lead to a change in the optimal coefficient and would result in reducing the safety factor of optimum state. The results showed that utilization of FGM state with optimal coefficient could significantly increase the safety factor and reduce displacements. Furthermore, increasing the rotation speed and radial loads would result in a change in the optimal non-homogeneous coefficient and reduce its equivalent safety factor.Thu, 31 Oct 2019 20:30:00 +0100Investigation of Tensile Characteristics of an Epoxy Matrix Com-posite with Uni-Directional and ...
https://macs.semnan.ac.ir/article_3777_455.html
Using natural hemp fibers to reinforce the tensile characteristics of polymer matrix composites is investigated in this article. The fibers were applied to the epoxy matrix in unidirectional and hybrid tissue forms. After preparation of standard tensile stress test specimens via manual layup, the standard tensile test was done. Young’s modulus, ultimate tensile stress, and the amount of absorbed energy before fracture were obtained experimentally. A comparison is performed with respect to fibers posture. In all cases, the tissue fiber samples gave a higher strength in comparison with the unidirectional laminated fibers. An analytical model is finally presented to estimate the elasticity modulus of the tissue reinforced composites.Thu, 31 Oct 2019 20:30:00 +0100Sintered Steel Composites Reinforced with Ceramic Nanoparticles: Fabrication, Characteristics ...
https://macs.semnan.ac.ir/article_3775_455.html
Steel composites reinforced with alumina nanoparticles were prepared by powder metallurgy process. Samples containing two different amounts of carbon (0.35 and 0.55 wt.%) and 0-5 wt.% Al2O3 nanoparticles were fabricated by mixing, compacting and sintering of diffusion bonded Distaloy AE powder. The density, hardness and wear tests were performed on the prepared samples. Furthermore, the microstructures and worn surfaces were analyzed by optical and scanning electron microscope (SEM), respectively. The wear tests were carried out in forces of 30, 40 and 50 kN and 1000 m distance in dry condition and ambient temperature. The results showed that increasing the alumina nanoparticles would reduce the density (~ 10.8 and 9.6 % for 0.35 and 0.55 wt.% C, respectively) and would increase the hardness (~ 14.1 and 7.2 % for 0.35 and 0.55 wt.% C, respectively) of sintered samples. With increasing carbon content, the amount of lost material and the rate of wear decrease. The lost volume increases with increasing wear distance and applied force. Addition of reinforcement to the steel matrix, improves the wear resistance up to 3 wt.% alumina nanoparticles. This increase in the samples varies between 30% to 73%. More increasing of alumina (5 wt.%) decreases the wear resistant of samples. The wear mechanisms including oxidation in low forces that convert to adhesive and abrasive with increasing applied force. The wear curves indicate that as the wear distance increases, the lost volume increases, while the wear rate decreases.Thu, 31 Oct 2019 20:30:00 +0100A New Three-Dimensional Refined Higher-Order Theory for Free Vibration Analysis of Composite ...
https://macs.semnan.ac.ir/article_3776_455.html
A new closed form formulation of three-dimensional (3-D) refined higher-order shell theory (RHOST) to analyze the free vibration of composite circular cylindrical shells has been presented in this article. The shell is considered to be laminated with orthotropic layers and simply supported boundary conditions. The proposed theory is used to investigate the effects of the in-plane and rotary inertias as well as transverse normal and shear strains on the dynamic response of thick composite cylindrical shells. The trapezoidal shape factor of the shell element is incorporated to obtain accurate stress-resultants. Using Hamilton’s principle, the equations of motion are obtained and solved in terms of the Galerkin method. Numerical results for the natural frequencies are verified by making comparison with the 3-D exact elasticity iterative solutions in the literature. In addition, the validity of the results is further verified by ABAQUS. According to the results, for thick composite cylinders with large length-to-radius and orthotropic ratios, through thickness exact integration yields accurate stress-resultants for proper prediction of the natural frequencies.Thu, 31 Oct 2019 20:30:00 +0100Influence of Different Foaming Conditions on the Mechanical, Physical, and Structural ...
https://macs.semnan.ac.ir/article_3757_455.html
In this article, the effects of different foam production times and temperatures on the mechanical, physical, and structural properties of polypropylene (PP) foam has been investigated. The microcellular PP foams were carried out using supercritical carbon dioxide (sc-CO2) as a physical foaming agent in a batch process. The samples were placed in a pressure vessel and were saturated with sc-CO2 at room temperature (23 - 25 °C) and saturation pressure of 40 MPa for 35 hours. Then, samples were removed from the vessel after releasing the pressure and were immersed in a glycerin bath for different times of 90, 180, and 270 seconds and different temperatures of 155 °C, 165 °C, and 175 °C. The mechanical responses of samples, e.g., flexural, Izod impact, and dynamic mechanical thermal properties, and physical characterization containing water absorption and relative density, were studied. Scanning Electron Microscopy (SEM) was applied to investigate the surface morphology. The cell size, cell density, and cell structure of PP foams were investigated by morphological parameters. X-ray diffractometer was utilized to evaluate the interaction effect on the samples. Results showed that in the semi-crystalline polymers such as polypropylene, the foaming temperature must be higher than the melting temperature of PP. A simultaneous examination of mechanical, physical, and morphological test results as well as cell structure properties indicate that the best temperature and time conditions for producing PP foams are the temperature of 175 °C and time of 270 seconds, respectively. These optimum conditions could be used in the industrial production of PP foams.Thu, 31 Oct 2019 20:30:00 +0100Study on Compression and Flexural Behavior of ABS-SiO2 Poly-mer Matrix Composite Fabricated by ...
https://macs.semnan.ac.ir/article_3790_455.html
In the present work, an experimental study was done to prepare Acrylonitrile-Butadiene-Styrene matrix composite reinforced by Nano-silica particles. The hot extrusion method was utilized here to fabricate the composite specimens used for flexural and compression tests. In order to identify the effect of SiO2 content and extrusion temperature, 12 experiments have been carried out and the obtained results were discussed according to scanning electron microscopy (SEM) images of the sample cross section. In addition, crack propagation and barreling phenomenon were discussed by variation process factors. Obtained results revealed that addition of nano-SiO2 up to 3% would cause the improvement in both flexural and compression strengths while a further increase in reinforcement content causes reduction of composite strength. Furthermore, samples prepared at extrusion temperature of 210°C, have lower strength compared to those fabricated by 180°C temperature. Finally, it was found that increase in SiO2 content and decrease in extrusion temperature would increase the brittleness of composite.Thu, 31 Oct 2019 20:30:00 +0100Improving the Performance of the Sandwich Panel with the Corrugated Core Filled with Metal ...
https://macs.semnan.ac.ir/article_3780_455.html
A new type of composite structure with a metal foam is reinforced by the metal corrugated core, called metal-foam-filled sandwich panel with a corrugated or V-frame core, is modelled, simulated, and studied in this article. All types of samples with different relative densities of the foam are tested and analyzed under the drop hammer load. The sandwich panel included two aluminium face-sheet, aluminium foams, and aluminium corrugated or V-frame cores. Mathematical and finite element models were also been developed to predict the effects of the relative density of the foam and other geometric parameters on the energy absorption. In addition, the mathematical equations based on a mass-spring-damper problem with two degree-of-freedom (DOF) were derived to evaluate the kinetic and kinematic parameters of the sandwich panel, such as velocity, acceleration, contact force, and energy absorption. It was found that the models could represent the dynamic response of the sandwich panel. Finally, in order to improve the performance of the sandwich panel, an optimization method was utilized for finding the optimum parameters which play an important role.Thu, 31 Oct 2019 20:30:00 +0100Stress Analysis of FGM Rotating Disk Subjected to Mechanical and Thermal Loads in Aircraft Gas ...
https://macs.semnan.ac.ir/article_3787_0.html
According to high usages of rotating disk in aircraft gas turbine engine, turbo pumps in oil and gas industries, steam and gas turbines in power plants, marine gas turbine and other industrial rotary machines designing and getting under the mechanical and thermal loading made this design and analysis to be as a special significance. These disks are subjected to mechanical and thermal loads. In this study, four methods, variable material properties (VMP), Galerkin, Runge-Kutta with two different rules calculate the amount of displacement, stress and strain of a rotary disk which has been used from a functional graded material (FGM). The problem in different states of loading and temperature dependence and independence of the properties has been resolved. Disk properties with the specified function of radius change. Mechanical loading conditions result from the centrifugal disk and blades mounted on it and the effects of shaft pressure and thermal stress caused by temperature difference in the shaft. The results obtained from each of the four methods are closed together and can be used to analyse the problems of this type. By Combining all loads the most radial stresses and environmental stresses respectively obtained in the center of the inner and outer radius and inner radius of the disk. By using the results can get most optimal design of the (FGM) disk.Thu, 25 Apr 2019 19:30:00 +0100Failure Pressure Prediction of Semi Spherical GFRP Shells in Thermal Environment
https://macs.semnan.ac.ir/article_3789_0.html
The pressure tests and temperature effects on the failure of composite pressure vessels is an expensive and time-consuming process. In this research, a new process has been designed in the laboratory scale to manufacture a portion of the composite vessel as a test specimen. The com-posite specimen is manufactured in a close mold and is tested in an apparatus that is able to control gas pressure up to 100 bars and temperature up to 150 Celsius. A spherical cap of com-posite is designed as a test specimen to be pressure tested up to failure at constant temperature. A closed mold has been also designed and fabricated to manufacture the test specimens. Testing apparatus consisting of three-part holder, gas tank, pressure controller and temperature con-troller is designed and fabricated for the failure tests. To examine proper function of the fabri-cated mold and testing apparatus, twelve small spherical cap of the GFRP test specimens manu-factured by the hand layup process considering [0/90/45/-45/90/0] arangment in the fabricat-ed mold. Burn off tests has shown a closed tolerance of fiber volume fraction for all specimens. The test specimens subjected to internal pressure at constant temperature up to failure. A nu-merical analysis of the GFRP spherical cap has been also run using ABAQUS software consider-ing Hashin failure criterion to determine the failure pressure at constant temprature. Both the experimental results and finite element calculation of failure pressure have shown to be close enough to trust the mold and testing apparatus. These results also showed that the failure pres-sure decreases as the temperature increases. The numerical results for prediction of the failure pressure however have shown to be greater than experimental values and an average difference of 16.5% has shown to be all four tests.Thu, 25 Apr 2019 19:30:00 +0100An Investigation of Stress and Deformation Behavior of Functionally Graded Timoshenko Beams ...
https://macs.semnan.ac.ir/article_3794_0.html
A functionally graded material beam with generalized boundary conditions is considered in the present work to study the deformation and stress behavior under thermal and thermo-mechanical load. Three discrete combinations of functionally graded materials have been con-sidered to include a wide range of materials and material property. The variation of material properties has been taken along the height of the beam cross-section as per power law formula-tion. The formulation has been derived using the principle of virtual work to obtain governing equations for FG Timoshenko beams. The development of governing equations is made using a unique method of unified formulation (Li [16]) in which the displacement variables are arranged in the form of a independent variable that subsequently reduces the equations to a single fourth order differential equation similar to the equation given by classical beam theory and is been extended to thermo-mechanical loading in the present work. The transverse shear stress/ strain for Timoshenko beams have been taken care of within this unified formulation. The for-mulation reported in this work has been generalized for various loading conditions and in the present work thermal and thermo-mechanical load has been considered where temperature has been varied along the beam height. Exact solutions of the fourth order differential equation for the deformation and stress have been obtained for three types of boundary conditions viz.- Clamped-Free (C-F), Simply Supported (S-S) and Propped Cantilever (C-S). The study has been extended to cover wide range of temperature distribution so as to include uniform, linear and non-linear temperature profiles. Deformation and stresses; axial stresses and transverse (shear) stresses, have been reported for different power law index values.Thu, 25 Apr 2019 19:30:00 +0100A novel method for considering interlayer effects between graphene nanoribbons and elastic ...
https://macs.semnan.ac.ir/article_3891_0.html
A complete investigation on the free vibration of bilayer graphene nanoribbons (BLGNRs) mod-eled as sandwich beams taking into account tensile-compressive and shear effects of van der Waals (vdWs) interactions between adjacent graphene nanoribbons (GNRs) as well as between GNRs and polymer matrix is performed in this research. In this modeling, nanoribbon layers play role of sandwich beam layers and are modeled based upon Euler-Bernoulli theory. To consider effects of vdWs interactions between adjacent GNRs as well as between GNRs and polymer matrix, their equivalent tensile-compressive and shear moduli are considered and utilized in derivation of governing equations instead of employing conventional Winkler and Pasternak effects for elastic medium. The governing equations of motion are derived by considering the assumptions and employing sandwich beam theory, and natural frequencies are obtained by implementing harmonic differential quadrature method (HDQM). A detailed study is performed to examine the influences of the tensile-compressive and shear effects of vdWs interactions between adjacent GNRs as well as between GNRs and polymer matrix on the free vibration of BLGNRs.Sat, 29 Jun 2019 19:30:00 +0100Investigation of Nonlinear Behavior of Composite Bracing Structures with Concrete Columns and ...
https://macs.semnan.ac.ir/article_3953_0.html
The composite structural system (RCS) is a new type of moment frame, which is including a combination of concrete columns (RC) and steel beams (S). These structural systems have the advantages of both concrete and steel frames [1]. In previous research on composite structures, there are some studies regarding RCS composite conections, but there is no investigation about seismic resisting system for these systems in aspect of implementation and performance. In this paper, it is investigated about the seismic behavior of the RCS composite bracing frame. To achieve this objective, nonlinear analysis of RCS composite frames with and without bracing has been done using finite element method. The behavior factors of these frames have been calculated after analyzing frames. It can be seen based on the results of the analysis that braces increase the yielding strength, ultimate strength and stiffness of RCS composite frames. Also, the comparison of analytical and experimental results shows that the nonlinear behavior of RCS can be accurately predicted using finite element method.Sat, 27 Jul 2019 19:30:00 +0100Nonlinear Magneto-Nonlocal Vibration Analysis of Coupled Piezoelectric Micro-Plates Reinforced ...
https://macs.semnan.ac.ir/article_3964_0.html
The aim of the paper is to analyze nonlinear electro-magneto vibration of a double-piezoelectric composite microplate-system (DPCMPS) based on nonlocal piezoelasticity theory. The two mi-croplates are assumed to be connected by an enclosing elastic medium which is simulated by Pasternak foundation. Both of piezoelectric composite microplates are made of poly-vinylidene fluoride (PVDF) reinforced by agglomerated carbon nanotubes (CNTs). The Mori-Tanaka model is employed to calculate mechanical properties of composite. Using nonlinear strain-displacement relations and considering charge equation for coupling between electrical and mechanical fields, the motion equations are derived based on energy method and Hamilton's principle. These equa-tions can't be solved analytically due to their nonlinear terms. Hence, differential quadrature method (DQM) is employed to solve the governing differential equations for the case when all four ends are clamped supported and free electrical boundary condition. The frequency ratio of DPCMPS is investigated for three typical vibrational states, namely, out-of-phase, in-phase and the case when one microplate is fixed in the DPCMPS. A detailed parametric study is conducted to scrutinize the influences of the small scale coefficient, stiffness of the internal elastic medium, the volume fraction of the CNTs, agglomeration and magnetic field. The results indicate that with increasing volume fraction of the CNTs, the frequency of the structure increases. This study might be useful for the design and smart control of nano/micro devices such as MEMS and NEMS.Mon, 26 Aug 2019 19:30:00 +0100Study of High-cycle Fatigue Properties in Tibia Bovine Bones based on Reliability and ...
https://macs.semnan.ac.ir/article_4025_0.html
Bones are natural composites, which are consisted of mineral fibers, strengthen the organic matrix. They are exposed to both monotonic and cyclic loadings. Therefore, one failure mechanism could be fatigue phenomenon. In this article, the scatter-band and the reliability of tibia bovine bones were predicted in the load-controlled fatigue condition. The one-point rotary-bending fatigue machine was utilized to carry out standard tests at two different loading levels, 0.4 and 0.6 kg for three various loading frequencies, 10, 20 and 30 Hz for tibia bones. For scatter-band prediction, three confidence levels (85, 90, and 95%) were selected. lower/upper bands were drawn for a selected target function, including the ratio of logarithmic fatigue lifetimes to stress levels. For the reliability prediction, three different distribution functions were considered. Results showed by decreasing the confidence level, the scatter-band would be narrower. Besides, the failure probability generally increased at 0.6 kg of the loading level, when the loading frequency increased.Tue, 22 Oct 2019 20:30:00 +0100Elastic analysis of Shrink-fitted Thick FGM Cylinders Based on Linear Plane Elasticity Theory
https://macs.semnan.ac.ir/article_4026_0.html
Nowadays, functionally graded materials (FGM) are widely used in many industrial, aerospace and military fields. On the other hand, the interest in the use of shrink-fitted assemblies is increasing for designing composite tubes, high-pressure vessels, rectors and tanks. Although extensive researches exist on thick-walled cylindrical shells, not many researches have been done on shrink-fitted thick FGM cylinders. In this paper, an analytical formulation for shrink-fitted of axisymmetric thick-walled FGM cylinders based on the linear plane elasticity theory is presented. The stresses and displacement fields in thick cylindrical shells are calculated using the real, Repeated and complex roots of characteristic equation. The displacements and stresses resulted are depicted for a case study. The results show that the material composition variation had evident effects on shrink-fit pressure in the intersection area of two fitted tubes. The value of this pressure affects radial and hoop stress distribution in functionally graded circular cylinders walls.Wed, 23 Oct 2019 20:30:00 +0100Semi Analytical Transient Dynamic Analysis of Composite Adhesive Single-lap Joints
https://macs.semnan.ac.ir/article_4027_0.html
A novel semi analytical method is developed for transient analysis of single-lap adhesive joints with laminated composite adherends subjected to dynamical loads. The presented ap-proach has the capability of choosing arbitrary loadings and boundary conditions. In this model, adherends are assumed to be orthotropic plates that obeyed from the classical lamina-tion theory. Stacking sequences can be either symmetric or asymmetric. Adhesive layer is homogenous and isotropic material and modelled as continuously distributed normal and shear springs. By employing constitutive, kinematics and equations of motions, sets of gov-erning differential equations for each inside and outside of overlap zones are obtained. By solving these equations, the time dependent shear and peel stresses in adhesive layer as well as deflections, stress resultants and moment resultants in the adherends are determined. The developed results are successfully compared with the experimental research presented in available literates. It is seen that the time variations of adhesive peel and shear stress dia-grams are asymmetric for the case of symmetric applied load with high variation rate. Also it is observed that although the magnitude of applied transverse shear force is reduced to 10% of applied axial force, but a significant increase of 40% in the maximum peel stress is achieved.Sat, 26 Oct 2019 20:30:00 +0100Thermal Buckling and Thermal Induced Free Vibration Analysis of Perforated Composite Plates: A ...
https://macs.semnan.ac.ir/article_4028_0.html
This paper is concerned with thermal buckling and thermal induced free vibration analyses of PCPs (perforated composite plates) with simply supported edges using a mathematical model. The stiffness and density of PCP is defined locally using Heaviside distribution functions. The governing equations are derived based on CLPT. The present solution gives reasonable results in comparison with the few literatures. To investigate the structural behaviour of PCPs subjected to initial thermal loads, many parametric studies have been carried out. Results showed that the presence of perforations has significant effect on thermal buckling and thermal induced fundamental frequency.According to results, By increasing the E2/E1 and α2/α1 ratios, the critical temperature difference of orthotropic perforated plate is decreased. Using the same material properties, the PCP (R=50%) is 4 times more resistant for thermal buckling than the monolithic composite plate of the same weight. By increasing the E2/E1 ratio, the thermal induced fundamental frequency of the orthotropic perforated plate demonstrate ascending and •By increasing the E2/E1 ratio, the thermal induced fundamental frequency of the orthotropic perforated plate demonstrate ascending and descending behaviour before and after a specific intersection point.Sat, 26 Oct 2019 20:30:00 +0100A Comparative Study on the Microstructure and Mechanical Prop-erties of Al-Si-Cu/1wt %NCP ...
https://macs.semnan.ac.ir/article_4029_0.html
In this paper, microstructural characteristics and mechanical properties of Al-Si-Cu/NCP com-posites were evaluated. Reinforced nanocomposites with 1 wt% nano-clay were fabricated by the method of the stir casting. Stirring times and temperatures were variable parameters to produce specimens. Then, the effect of a T6 heat treatment which contained solutioning at 490 ºC for 5 hrs, quenching and aging process at 200 ºC for 2 hrs, on tribological behavior and compression properties of nanocomposites was investigated. The microstructural observa-tion was conducted by the optical microscopy (OM) and the field emission scanning electron microscopy (FESEM). The obtained results demonstrated that nano-clay particles were dis-tributed in the aluminum matrix. The range of Vickers hardness values was 123 to 158 VHN for nanocomposites. The wear resistance of nanocomposites increased when the stirring time and temperature increased to 4 mins and 800 ºC, respectively. The best compressive mechan-ical properties were related to the nanocomposite fabricated at 750 ºC and stirred for 2 mins. The higher stirring time and temperature resulted in the formation of AlSiFe intermetallic phase which decreased the ultimate compressive strength.Sat, 26 Oct 2019 20:30:00 +0100Thermoelastic analysis of a functionally graded simple blade using first-order shear ...
https://macs.semnan.ac.ir/article_4030_0.html
In this paper, thermo-elastic behavior of a functionally graded simple blade subjected to the mechanical and thermal loadings is presented using a semi-analytical method and a variable thickness cantilever beam model. A specific temperature gradient is applied between the root and the edges of the beam. It is assumed that the mechanical and thermal properties are longitudinal direction dependent based on volume percent of reinforcement. The approach is composed of several steps including adoption of first-order shear deformation theory, applying beam division along the longitudinal direction, imposing global boundary conditions and considering the continuity conditions. As a result, longitudinal and transverse displacements, and consequently longitudinal, shear and effective stresses are obtained. The analysis is performed for three different distributions of reinforcement particles and pure matrix. Minimum effective and shear stresses distribution belongs to the blade with 0% reinforcement at root and 40% reinforcement at tip surface. It has also been found that use of reinforcement particles have reasonable effect on the longitudinal and transverse deflections.Sat, 26 Oct 2019 20:30:00 +0100Mechanical Characterization and Wear Behavior of Nano TiO2 Particulates Reinforced Al7075 Alloy ...
https://macs.semnan.ac.ir/article_4031_0.html
In the current research work synthesis, characterization, mechanical and wear behavior of 5 and 10 wt. % of nano TiO2 particulates reinforced Al7075 alloy composites have been investigated. The Al7075 alloy and nano TiO2 particle composites were prepared by melt stir system. After the preparation, the prepared composites were examined by SEM, EDS and XRD for analyzing the microstructures and chemical elements. Further, mechanical and wear behavior of as cast Al7075 alloy and Al7075 -5 and 10 wt. % of nano TiO2 composites were studied. Mechanical properties like hardness, UTS, yield quality and ductility were assessed according to ASTM measures. Pin on disc contraption was utilized to lead the dry sliding wear tests. The analyses were led by differing loads and sliding speeds for a sliding distance of 3000 m. From the examination, it was discovered that the hardness, extreme strength and yield quality of composites were expanded because of nano TiO2 particles in the Al7075 amalgam grid. In nano TiO2 fortified composites the rate extension was diminished. Further, there was an expansion in the volumetric wear misfortune concerning the load, speed and sliding distance for all the readied materials. To study the fractography and different wear mechanisms for various test conditions of different compositions, tensile fractured surfaces and the worn surface morphology were analyzed by scanning electron microscope.Sat, 26 Oct 2019 20:30:00 +0100Influence of Hygrothermal environment and FG material on natural frequency and parametric ...
https://macs.semnan.ac.ir/article_4032_0.html
In this present work, vibration characteristics and the parametric instability of functionally graded material (FGM) plates with cyclic loading in a hygrothermal field are discussed. The plate element has been modelled in a finite element by applying the third-order shear deformation hypothesis. The mathematical formulation of the FGM plate is made with two material constituents by using the power rule to vary in association with the thickness path of the plate. Hamilton’s principle is employed to develop the arbitrary equation of motion, which is converted into periodic constants using the Mathieu Hill equation. The derived equation of movement with the help of Floquet’s theorem is used to generate the instability and stability separations of the FGM plate in the hygrothermal environment. The current proposed results are compared with existing literature results to assess its validity. The free vibration characteristics are reduced by the rise of moisture absorption and temperature of the FGM plates in the hygrothermal atmosphere. Hence, the influence of increased parameters increases the parametric instability of FGM plates. Temperature rise and moisture absorption regarding the parametric stability and the uncertainty region of the FGM plates are also observed.Sat, 26 Oct 2019 20:30:00 +0100Vibration characteristics of functionally graded micro-beam carrying an attached mass
https://macs.semnan.ac.ir/article_4040_0.html
In this paper based on the modified couple stress theory and Euler-Bernoulli beam theory, free lateral vibration response of a micro-beam carrying a moveable attached mass is report-ed. This is a decent model for biological and biomedical applications helping early-stage diag-nosis of diseases and malfunctions of human body organs and enzymes. The micro-cantilever beam is composed of functionally graded materials (FGMs). The material properties are sup-posed to have variations through thickness of the beam in accordance with the power of law. Rayleigh-Ritz method is employeed to find natural frequencies of the first three vibration modes. To demonstrate the accuracy of the proposed method, the results are established and compared with technical literature. Influences of the material length-scale parameter that captures the size-dependency, ratio of mass of the beam to mass of the attached mass and power index of the graded material upon the vibrational behaviour of the system are consid-ered. This technical research denotes the importance of the material gradation besides to the inertia of an attached mass in the dynamic behaviour of the bio-micro-systems. As a result, adoption of suitable power index, mass ratio and position of the attached mass leads to a bet-ter design of bio-micro-systems leading to early-stage diagnostics.Wed, 13 Nov 2019 20:30:00 +0100