Mechanics of Advanced Composite StructuresMechanics of Advanced Composite Structures
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Feed provided by Mechanics of Advanced Composite Structures. Click to visit.Stress Analysis of FGM Rotating Disk Subjected to Mechanical and Thermal Loads In Aircraft Gas ...
https://macs.semnan.ac.ir/article_3787_493.html
Pursuant to the high usage of rotating the 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 casued this design and analysis to be as a special significance. These disks are subjected to mechanical and thermal loads. In this article, four methods, variable material properties (VMP), Galerkin, Runge-Kutta with two different rules compute the amount of displacement, stress, and strain of a rotary disk, which has been applied from a functionally graded material (FGM). The problem in dissimilar 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 acquired through every four methods are closed together and can be applied to analyse the problems of this type. 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. Through applying the results can get most optimal design of the (FGM) disk.Tue, 31 Mar 2020 19:30:00 +0100Thermal Buckling and Thermal Induced free Vibration Analysis of Perforated Composite Plates: a ...
https://macs.semnan.ac.ir/article_4028_493.html
This artcile is concerned with thermal buckling and thermal induced free vibration analyses of PCPs (perforated composite plates) with simply supported edges applying a mathematical model. The stiffness and density of PCP are 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. In order to inspect the structural behaviour of PCPs subjected to initial thermal loads, many parametric studies have been carried out. Results indicated that the presence of perforations has a significant effect on thermal buckling and thermal induced fundamental frequency.Tue, 31 Mar 2020 19:30:00 +0100Investigation of Nonlinear Behavior of Composite Bracing Structures with Concrete Columns and ...
https://macs.semnan.ac.ir/article_3953_493.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.Tue, 31 Mar 2020 19:30:00 +0100Effects of Horizontal Deficiency Location on the Structural Behaviors of Steel SHS Short ...
https://macs.semnan.ac.ir/article_4280_493.html
Several deficient steel structural members require to be strengthened all over the world. In this article, horizontal defects were generated at three locations (top, middle, and bottom) on the middle element and the middle of the side element. Consequently, the effects of the location of such defects on axial behavior of Carbon Fiber Reinforced Polymer (CFRP) strengthened steel Square Hollow Section (SHS) tubular short columns were examined. To this end, a total of 13 steel columns were experimentally examined. The same specimens were simulated applying ABAQUS V.6.14. The samples were no defect (control), 6 non-strengthened columns with defects at different locations, and 6 strengthened specimens with defects. The results indicated that horizontal defects caused a significant decrease in load bearing capacity and initial performance. The damage located at the middle and the middle of the corner elements caused the most reductions on load bearing capacity by 16% and 17%, compared to the control, respectively. The defects on the side element led to greater destruction and bearing capacity decline compared to the middle defects. As a result of axial loading, the area of horizontal defects experienced local buckling, lateral rupture, and axial deformation boost. Carbon Fiber played a key role in ductility and strength increase around the defect by covering it. Applying four CFRP layers declined the stress concentration, delaying the local buckling as a result of high confining strength. The fiber increased bearing capacity by 64% and 37% for the middle and the corner elements, compared to the control.Tue, 31 Mar 2020 19:30:00 +0100Vibration Characteristics of Functionally Graded Micro-Beam Carrying an Attached Mass
https://macs.semnan.ac.ir/article_4040_493.html
In this article, in reference to the modified couple stress theory and Euler-Bernoulli beam theory, the free lateral vibration response of a micro-beam carrying a moveable attached mass is investigated. This is a decent model for biological and biomedical applications beneficial to the early-stage diagnosis 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 supposed to show variations through-thickness of the beam in consonance to the power of law. Rayleigh-Ritz method is applied in order to explore the natural frequencies of the first three vibration modes. In order to manifest the accuracy of the proposed method, the results are established and juxtaposed with technical literature. Influences of the material length-scale parameter that captures the size-dependency, ratio of the mass of the beam to the mass of the attached mass and power index of the graded material consequent to the vibrational behavior of the system are contemplated. This technical research denotes the value of the material gradation besides to the inertia of an attached mass in the dynamic behavior of the bio-micro-systems. As a result, the adoption of suitable power index, mass ratio and position of the attached mass lead to the superior design of bio-micro-systems persuading early-stage diagnostics.Tue, 31 Mar 2020 19:30:00 +0100Fluid-Structure Interaction of Vibrating Composite Piezoelectric Plates Using Exponential Shear ...
https://macs.semnan.ac.ir/article_3645_493.html
In this article 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 deliberated by applying exponential shear deformation theory. Fluid velocity potential is acquired 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 with 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 applying Hamilton’s principle, the natural frequencies of the fluid-structure system with simply supported boundary conditions are computed using the Galerkin method. The model is compared to the available results in the literature, and consequently 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 displayed.Tue, 31 Mar 2020 19:30:00 +0100Mechanical Characterization and Wear Behavior of Nano TiO2 Particulates Reinforced Al7075 Alloy ...
https://macs.semnan.ac.ir/article_4031_493.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 are inspected. The Al7075 alloy and nano TiO2 particle composites were provided by melt stir system. After the preparation, the prepared composites were analyzed by SEM, EDS, and XRD for inquiring the microstructures and chemical elements. Furthermore, mechanical and wear behavior of as cast Al7075 alloy and Al7075 -5 and 10 wt. % of nano TiO2 composites were examined. Mechanical properties like hardness, UTS, yield quality, and ductility were assessed pursuant to ASTM measures. Pin on disc contraption was applied in order 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. Moreover, there was an expansion in the volumetric wear misfortune concerning the load, speed and sliding distance for all the readied materials. In order to inspect the fractography and dissimilar wear mechanisms for various test conditions of different compositions, tensile fractured surfaces and the worn surface morphology were analyzed by scanning electron microscope.Tue, 31 Mar 2020 19:30:00 +0100A Novel Method for Considering Interlayer Effects between Graphene Nanoribbons and Elastic ...
https://macs.semnan.ac.ir/article_3891_493.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.Tue, 31 Mar 2020 19:30:00 +0100Influence of Hygrothermal Environment and FG Material on Natural Frequency and Parametric ...
https://macs.semnan.ac.ir/article_4032_493.html
In this article, vibration characteristics and the parametric instability of functionally graded material (FGM) plates with cyclic loading in a hygrothermal field are discussed. The plate element is modeled 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 applying 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 applied 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 the 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.Tue, 31 Mar 2020 19:30:00 +0100Failure Pressure Prediction of Semi Spherical GFRP Shells in Thermal Environment
https://macs.semnan.ac.ir/article_3789_493.html
In this article 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 deliberated by applying exponential shear deformation theory. Fluid velocity potential is acquired 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 with 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 applying Hamilton’s principle, the natural frequencies of the fluid-structure system with simply supported boundary conditions are computed using the Galerkin method. The model is compared to the available results in the literature, and consequently 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 displayed.Tue, 31 Mar 2020 19:30:00 +0100Nonlinear Magneto-Nonlocal Vibration Analysis of Coupled Piezoelectric Micro-Plates Reinforced ...
https://macs.semnan.ac.ir/article_3964_493.html
The aim of this article is to analyze nonlinear electro-magneto vibration of a double-piezoelectric composite microplate-system (DPCMPS) pursuant to the nonlocal piezoelasticity theory. The two microplates are assumed to be connected by an enclosing elastic medium, which is simulated by the 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 compute the mechanical properties of composite. Applying nonlinear strain-displacement relations and contemplating charge equation for coupling between electrical and mechanical fields, the motion equations are derived in consonance to the energy method and Hamilton's principle. These equations can't be solved analytically as a result of their nonlinear terms. Hence, the 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 conditions. The frequency ratio of DPCMPS is inspected 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 reveal that with increasing volume fraction of the CNTs, the frequency of the structure increases. This study might be beneficial for the design and smart control of nano/micro devices such as MEMS and NEMS.Tue, 31 Mar 2020 19:30:00 +0100Elastic analysis of Shrink-fitted Thick FGM Cylinders Based on Linear Plane Elasticity Theory
https://macs.semnan.ac.ir/article_4026_493.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 FG circular cylinders walls.Tue, 31 Mar 2020 19:30:00 +0100A Comparative Study on the Microstructure and Mechanical Properties of Al-Si-Cu/1wt %NCP ...
https://macs.semnan.ac.ir/article_4029_493.html
In this article, microstructural characteristics and mechanical properties of Al-Si-Cu/NCP composites 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. Consequently, the effect of a T6 heat treatment, which contained solutioning at 490 ºC for 5 hrs, quenching, and aging process at 200ºC for 2 hrs, on tribological behavior and compression properties of nanocomposites was inspected. The microstructural observation was conducted by optical microscopy (OM) and the field emission scanning electron microscopy (FESEM). The acquired results demonstrated that nano-clay particles were distributed in the aluminum matrix. The range of Vickers hardness values was 123 to 158 VHN for nanocomposites. The wear resistance of nanocomposites enhanced when the stirring time and temperature increased to 4 mins and 800 ºC, respectively. The best compressive mechanical properties correlated 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 reduced the ultimate compressive strength.Tue, 31 Mar 2020 19:30:00 +0100Semi Analytical Transient Dynamic Analysis of Composite Adhesive Single-lap Joints
https://macs.semnan.ac.ir/article_4027_493.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 approach has the capability of choosing arbitrary loadings and boundary conditions. In this model, adherends are assumed to be orthotropic plates that pursuant to the classical lamination theory. Stacking sequences can be either symmetric or asymmetric. The adhesive layer is homogenous and isotropic material and modelled as continuously distributed normal and shear springs. By applying constitutive, kinematics, and equations of motions, sets of governing differential equations for each inside and outside of overlap zones are acquired. 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 computed. The developed results are successfully compared with the experimental research presented in available literates. It is observed that the time variations of adhesive peel and shear stress diagrams are asymmetric for the case of symmetric applied load with high variation rate. Moreover, it is reported that although the magnitude of applied transverse shear force is reduced to 10% of applied axial force, however a significant increase of 40% in the maximum peel stress attained.Tue, 31 Mar 2020 19:30:00 +0100Thermoelastic Analysis of a Functionally Graded Simple Blade Using First-Order Shear ...
https://macs.semnan.ac.ir/article_4030_493.html
In this article, the thermo-elastic behavior of a functionally graded simple blade subjected to the mechanical and thermal loadings is presented, applying a semi-analytical method and a variable thickness cantilever beam model. A specific temperature gradient is employed between the root and the edges of the beam. It is assumed that the mechanical and thermal properties are longitudinal direction dependent pursuant to volume percent of reinforcement. The approach is composed of several steps, including adoption of first-order shear deformation theory, applying beam division accompanying the longitudinal direction, imposing global boundary conditions, and deliberating the continuity conditions. As a result, longitudinal and transverse displacements, and consequently longitudinal, shear and effective stresses are acquired. The analysis is performed for three different distributions of reinforcement particles and pure matrix. Minimum effective and shear stresses distribution belong to the blade with 0% reinforcement at root and 40% reinforcement at tip surface. It has also been discovered that application of reinforcement particles have reasonable effect on the longitudinal and transverse deflections.Tue, 31 Mar 2020 19:30:00 +0100An Investigation of Stress and Deformation Behavior of Functionally Graded Timoshenko Beams ...
https://macs.semnan.ac.ir/article_3794_493.html
A functionally graded material beam with generalized boundary conditions is contemplated in the present study in order to examine the deformation and stress behavior under thermal and thermo-mechanical load. Three discrete combinations of functionally graded materials have been deliberate in including a wide range of materials and material properties. The variation of material properties has been taken along the height of the beam cross-section as per power law formulation. The formulation has been derived, applying the principle of virtual work in order to acquire governing equations for FG Timoshenko beams. The development of governing equations is made through applying a unique method of unified formulation (Li [16]) in which the displacement variables are arranged in the form of aindependent variable that subsequently reduces the equations to a single fourth order differential equation similar to the equation given by classical beam theoryand 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 formulation employed in this research has been generalized for various loading conditions, and in the present work, thermal and thermo-mechanical load has been pondered where temperature has been varied in accordance with 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.Tue, 31 Mar 2020 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 +0100Size-dependent nonlinear dynamics of a non-uniform piezoelectric microbeam based on the strain ...
https://macs.semnan.ac.ir/article_4242_0.html
The nonlinear dynamics of an electrostatically actuated non-uniform microbeam equipped with a damping film and a piezoelectric layer is studied. The nonlinear behaviour of the system is modelled using von Karman geometrical strain terms. The strain gradient theory was utilized and the Hamilton principle was applied to obtain equations of motion and boundary conditions. Then the equations were reduced by the Galerkin method and they are solved by multiple scale methods. The size-dependent responses for primary, super-harmonic and sub-harmonic resonance were studied. The influences of beam width, thickness, and distance between electrodes on resonant frequency response along with nonlinearity of system were examined. The results showed that the static behavior and compulsory vibration of microbeams were strongly dependent on size. Also, The results demonstrated that along with the reducing effect of size, the hardness of the microbeam increases, which implies that if the thickness of the beam is smaller, then it results in the "hardening" of the system.Thu, 06 Feb 2020 20:30:00 +0100Strengthening of deficient steel sections using CFRP composite under combined loading
https://macs.semnan.ac.ir/article_4300_0.html
These days, strengthening of steel sections using carbon fiber reinforced polymer (CFRP) has attracted the attention of many researchers. For various reasons, the structures may be placed under combined loads. The deficiency in steel members may be created due to the errors caused by construction, fatigue cracking, and others. This study investigates the behaviors of deficient square hollow section (SHS) steel members strengthened by CFRP sheets under two types of the combined loads. To study the effect of CFRP strengthening on the structural behaviors of the deficient steel members, 17 specimens, 12 of which were strengthened using CFRP sheets, were analyzed. To analyze the steel members, 3D (three dimensional) modeling and nonlinear static analysis methods were applied, using ANSYS software. The results showed that CFRP strengthening has an impact on raising the ultimate capacity of deficient steel members and can recover the strength lost due to deficiency, and the impact CFRP strengthening on rising and recovering the ultimate capacity of the steel members under loading scenario 2 was more than the steel members under scenario 1.Sat, 21 Mar 2020 19:30:00 +0100Graphene Based Polymer Nano-composites- A Review
https://macs.semnan.ac.ir/article_4301_0.html
The sixth element of Periodic Table, Carbon, is a remarkable element due to its ability of cate-nation for combining with itself and other chemical elements of the periodic table. Nowadays, different types of carbon nano-fillers are employed widely as a reinforcement phase in poly-mer composites such as fullerenes, carbon nanotubes, graphene nano-platelets, and graphite platelets. Herein, the aspect ratio and distinctive electronic, thermal, and mechanical proper-ties of graphene make it a distinguished candidate for the wide range of applications in nano-science and nano-technology, especially in reinforcing polymers in industrial applications. In this review, not only the general properties but also the synthesize methods, intercalation, and exfoliation of the nano-particle in polymers have been studied. Also, the effect of this par-ticle on the mechanical, thermal, and electrical properties of the mentioned materials has been investigated. It was demonstrated that filling graphene platelets in the polymer materials improve their mechanical, thermal, and electrical properties.Sat, 21 Mar 2020 19:30:00 +0100Damage Detection in Concret Filled Tube Column Based on Exper-imentally Modal Data and Wavelet ...
https://macs.semnan.ac.ir/article_4302_0.html
Damage detection in Concrete-Filled Tubes (CFST) and its application in special structures such as high rise buildings, towers and bridges is important. CFST columns are widely considered by researchers and engineers due to the simultaneous utilization of steel and concrete proper-ties. Hence, any damage to this structural element may result in more serious and irreparable damages. Accordingly, identification of a particular type of damage that may be due to the buck-ling of a steel tube plate has been performed in this study. Since the buckled part in the column goes out of the system or its bearing capacity significantly decreases, in order to simulate the damage in this study, a part of the CFST column steel wall was cut off and since it's more likely to occur in the middle of the column, damage has been located in the middle of the column. After making the specimen and performing the test, the modal data has been extracted and has been called in MATLAB software and analyzed with the aid of the wavelet transform tool. The results show that the frequency is reduced and the mode shape of the specimens does not match com-pletely before and after the damage (Modal Assurance Criteria(MAC)), which indicates the dam-age in the specimen. To identify the location of the damage, the mode shape obtained from the modal experimentally has been given to the wavelet transform as the input signal and Daubechies (Db) wavelet has been applied that correctly identifies the location of the damage.Sat, 21 Mar 2020 19:30:00 +0100Mechanical Behavior and Optimization of Functionally Graded Hollow Cylinder with an Elliptic Hole
https://macs.semnan.ac.ir/article_4303_0.html
This paper presents a numerical solution and optimization for a functionally graded material cylinder with an elliptic hole subjected to mechanical pressure. To obtain the governing equa-tions, an elliptic cylindrical coordinate is used. The material properties are considered to vary with power-law function along the elliptic cylindrical direction. For solved the equations, the differential quadrature method is used. The results show that the inconsistency in shape of the hole in the cylindrical vessel can affect the results expected and the stresses in thickness of cylinder are changed. Then, by using von-Misses stress along the thickness, the optimal values for various material inhomogeneity and the geometry of the cylinder investigated. The results show that with low values of the functionally graded material index, the geometry of the cyl-inder has more effect on von Misses stress. Also with high values for the material index, the values for von Misses stress converge together and the material inhomogeneity has less effect on stress. The results show that for various geometries for the cylinder and holes, the best value for material homogeneity to occur the optimum value for von Misses stress is changed. The presented results verified with those reported in previous publications.Sat, 21 Mar 2020 19:30:00 +0100Buckling analysis of functionally graded cylindrical shells under mechanical and thermal loads ...
https://macs.semnan.ac.ir/article_4304_0.html
Using dynamic relaxation method, nonlinear mechanical and thermal buckling behaviors of functionally graded cylindrical shells is studied based on first-order shear deformation theory (FSDT). It is assumed that material properties of the constituent components of the FG shell vary continuously along the thickness direction based on simple power-law and Mori-Tanaka distribution methods separately. The axial compressive load and thermal gradient are applied to the shell incrementally so that in each load step the incremental form of governing equations are solved by the DR method combined with the finite difference (FD) discretization method to obtain the critical buckling load. After convergence of the code in the first increment, the latter load step is added to the former so that the program is repeated again. Then, the critical buckling load is achieved from the mechanical/ thermal load-displacement curves. In order to validate the present method, the results are compared with other papers and Abaqus finite element results. Finally, effects of different boundary conditions, grading index, rule of mixture, radius-to-thickness ratio and length-to-radius ratio are investigated on the mechanical and thermal buckling loads.Sat, 21 Mar 2020 19:30:00 +0100Dynamic Mechanical and Thermal Behavior of ABS/ Nano Silica Composite
https://macs.semnan.ac.ir/article_4305_0.html
In the present work an experimental study was carried out to study vibration behavior of ABS based Nano composite reinforced by Nano-silica particles. Twin extruder methodology was used here to fabricate the Nano composite samples regarding silica content as variable parameter. The samples were fabricated to be investigated by 3 points bending test in dynamic mechanical and thermal analysis machine. To identify parametric influence, number of 12 experiments has been carried out and the obtained results were discussed according to scanning electron microscopy (SEM) images of the samples cross section. It is found from the results that by increase of silica content up to 2%, the static and dynamic strength of fabricated Nano-composite is significantly enhanced. However, by further increase of silica content it is found that the fabricated sample shows brittle behavior causing reduction of strength properties. It is also found from the results that increase of silica content causes reduction in damping behavior of fabricated composites.Sat, 21 Mar 2020 19:30:00 +0100Buckling analysis of FML cylindrical shells under combined axial and torsional loading
https://macs.semnan.ac.ir/article_4306_0.html
Generally, in-served cylindrical shells usually buckle not merely under one of the basic loads, i.e., axial compression, lateral pressure, and torsion, but under a combination of them. The buckling behavior of fiber-metal laminate (FML) cylindrical shells under combined axial and torsional loading is studied in this paper. The Kirchhoff Love-type assumption is employed to study the axial buckling load. Then, an extended finite element (FE) model is presented and results are compared. A number of consequential parameters such as lay-up arrangement, metal type and metal volume fraction are employed and enhancement of buckling behavior of the shell is studied. Finally, the interaction of axial /torsional loading is analyzed and discussed. The results showed that as the metal volume fraction rises to 15%, the endurable buckling load increases almost 43% than the state there is no metal layer. The numerical results show that increasing the metal volume percentage leads to a decrease in buckling performance of the structure under axial loading.Sat, 21 Mar 2020 19:30:00 +0100Geometrically Nonlinear Analysis of Laminated Composite Plates subjected to Uniform Distributed ...
https://macs.semnan.ac.ir/article_4307_0.html
This paper presents a finite element method (FEM) for linear and geometrically nonlinear behaviors of cross ply square laminated composite plates subjected to uniform distributed load (UDL) with simply supported boundary conditions (SS-BCs). The original MATLAB codes are written to achieve finite element (FE) solution for bending of the plate. In geometrically nonlinear analysis, changes in geometry takes place when large deflection exist consequently provide nonlinear changes in the material stiffness and this effect on constitutive and equilibrium equations. The Von Karman form nonlinear strain displacement relations and a new inverse trigonometric shear deformation hypothesis are used for deriving the FE model. Here in-plane displacements make a use of an inverse trigonometric shape function to account the effect of transverse shear deformation. This hypothesis fulfills the traction free BCs and disrupts the necessity of shear correction factor (SCF). Overall plate is discretized using eight-noded isoparametric serendipity element. The equilibrium governing equations associated boundary conditions are obtained by using the principle of virtual work (PVW). The numerical results are obtained for central deflections, in-plane stresses and transverse shear stresses for different stacking sequences of cross ply laminates. The results are also computed by FE software ABAQUS for few cases. The obtained results show worthy agreement with previously published results. The results recommend the potential use of new FE model for linear and nonlinear deformations of composite plates.Sat, 21 Mar 2020 19:30:00 +0100Finite Element Modelling for Buckling Analysis of Tapered Axially Functionally Graded ...
https://macs.semnan.ac.ir/article_4308_0.html
In this study, an efficient finite element model with two degrees of freedom per node is devel-oped for buckling analysis of axially functionally graded (AFG) tapered Timoshenko beams resting on Winkler elastic foundation. For this, the shape functions are exactly acquired through solving the system of equilibrium equations of Timoshenko beam employing the power series expansions of displacement components. The element stiffness matrix is then formulated by applying the developed shape functions to the total potential energy along the element axis. It is demonstrated that the resulting shape functions, in comparison with Hermitian cubic interpolation functions, are proportional to the mechanical features of beam element including the geometrical properties, material characteristics, as well as the critical axial load. An exhaustive numerical example is implemented to clarify the efficiency and simplicity of the proposed mathematical methodology. Furthermore, the effects of end conditions, material gradient, Winkler parameter, tapering ratio, and aspect ratio on the critical buckling load of AFG tapered Timoshenko beam are studied in detail. The numerical outcomes reveal that the elastic foundation enhances the stability characteristics of axially non-homogeneous and homogeneous beams with constant or variable cross-section. Moreover, the results show that the influence of non-uniformity in the cross-section and axially inhomogeneity in material characteristics play significant roles in linear stability behavior of Timoshenko beams subjected to different boundary conditions.Sat, 21 Mar 2020 19:30:00 +0100Sensitivity Analysis of the Vibrating Laminated Composite Rectangular Plates in Interaction ...
https://macs.semnan.ac.ir/article_4309_0.html
This work is investigated the sensitivity analysis of the vibrating laminated composite rec-tangular plates in interaction with inviscid fluid using modify higher-order shear deformation plate theory. The EFAST method that is based on variance and it is independent of any as-sumption of linearity and uniformity between inputs and outputs is utilized for sensitivity analysis of laminated composite rectangular plates. Theoretical formulations, both for the laminated rectangular plates in interaction with inviscid, incompressible and irrotational fluid and the sensitivity analysis technique are summarized. A Cartesian coordinate system is used to describe governing equations of fluid-structure interaction. Hamilton's variational principle is used to derive the Eigen problem of the complex system. A numerical investiga-tion is carried out by using the Galerkin method and the boundary conditions of the plate are simply supported. A set of admissible displacement functions which satisfy identically the geometric boundary conditions are used to calculate the wet natural frequencies of the plate. In the numerical examples, the effect of the aspect ratio, thickness ratio and material or-thotropy orientation of the plate, depth ratio and width of the fluid on the fundamental natu-ral frequency of the vibrating laminated composite rectangular plates are examined and dis-cussed.Sat, 21 Mar 2020 19:30:00 +0100Molecular dynamics simulation of functional and hybrid epoxy based nanocomposites
https://macs.semnan.ac.ir/article_4310_0.html
In this paper, the effects of filler type, filler content, functionalization, and the use of hybrid nanofillers on nanocomposite mechanical properties are investigated. For this purpose, several nanocomposite types are modeled and analyzed using Molecular Dynamics method. In addition, crosslinking and nanofiller/matrix interface effects are considered. First thermoset epoxy resin with 75% crosslinking ratio between DGEBA resin and DETA hardener is simulated to determine pure resin properties. Then nanocomposites consisting of single walled carbon nanotubes (SWCNT), nanographene (NG), carbon nanoparticle (CNP), functional single walled carbon nanotubes (SWCNT-COOH), and functional nanographene (nanographene oxide) in thermoset epoxy are modeled and analyzed using Materials Studio software. In addition, filler weight fraction is increased from 2.5 to 10 percent in order to investigate the effects of filler content on nanocomposite mechanical properties. The results indicate that increasing nanofiller weight fraction from 0 to 7.5% results in an increase in nanocomposite elastic modulus for three non-functional nanofiller types. Moreover, functionalization improves nanocomposite properties as the highest increase in resin elastic modulus is obtained for the SWCNT-COOH reinforced epoxy for 7.5 weight percent filler contents. Also, agglomeration occurred at filler contents higher than 7.5 weight percent in the NG/epoxy and SWCNT/epoxy nanocomposites. Finally, the use of hybrid nanofillers reduced/prevented agglomeration for filler contents even up to 10 weight percent.Sat, 21 Mar 2020 19:30:00 +0100Elasto Dynamic Response Analysis of a Curved Composite Sandwich Beam Subjected to the Loading ...
https://macs.semnan.ac.ir/article_4422_0.html
In this paper the dynamic response of a simply - supported relatively thick composite sandwich curved beam under a moving mass is investigated. In contrast to previous works, the geometry of the beam is considered to be in a curved form. Moreover, the rotary inertia and the transverse shear deformation are also considered in the present analysis. The governing equations of the problem are derived using Hamilton's principle. Then, the obtained partial differential equations are transformed to ordinary differential equations with time varying coefficients, using the modal analysis method. Fourth order Runge-Kutta method is applied to solve the ordinary differential equations in an analytical – numerical form. The obtained results are validated by the results existed in the literature. Performing a thorough parametric study, the effects of some important parameters such as the mass and the velocity of the moving mass, the radius of the curvature of the beam, the core thickness to the total thickness ratio and the stacking sequences of the face sheets on the dynamic response are investigated. It is observed that increasing the mass and the velocity of the moving mass and the radius of the curvature of the beam, result in increase, decrease and increase of the dynamic deflection of the curved beam, respectively.Wed, 27 May 2020 19:30:00 +0100Active control of free and forced vibration of rotating laminated composite cylindrical shells ...
https://macs.semnan.ac.ir/article_4462_0.html
In this study, active control of free and forced vibration of rotating thin laminated composite cylindrical shells embedded with two magnetostrictive layers is investigated by means of classical shell theory. The shell is subjected to harmonic load which is exerted to inner surface of the shell in thickness direction. The velocity feedback control method is used in order to obtain the control law. The vibration equations of the rotating cylindrical shell are extracted by means of Hamilton principle while the effects of initial hoop tension, centrifugal and Coriolis accelerations are considered in the vibration equations. The differential equations of the rotating cylindrical shell are converted to ordinary differential equations by means of modified Galerkin method. The displacement of the shell is obtained using modal analysis. The free vibration results of this study are validated by comparison with the results of open literature. Also the validity of the forced vibration results is proved by comparison with the fourth order Runge-Kutta method's result. Finally, the effects of several parameters including circumferential wave number, rotational velocity, the whole orthotropic layers thickness, magnetostrictive layers thickness, length, the amplitude and exciting frequency of the load on the vibration characteristics of the rotating cylindrical shell are invesigated.Thu, 18 Jun 2020 19:30:00 +0100The Effect of Different Weighting Ratios, Length, and Thickness on Weighted Sum of the First ...
https://macs.semnan.ac.ir/article_4463_0.html
In this study, a weighted sum, consisting two non-dimensionalized quantities critical buckling force and natural frequency, is employed to maximize the objective function for a laminated composite circular cylindrical shell. The function is considered to find the optimum solutions as the goal. Orientation angels of fibers are mentioned in a well-known configuration as candidate design, and critical buckling force and natural frequency values are derived with the first order shear deformation theory. The composite shell is considered with 8 layers, also the boundary conditions are assumed to be fully simply support and to satisfy boundary conditions displacement and slope components are defined in form of double Fourier series. After combination of differential operators and Fourier series, eventually the matrix L is found and Galerkin method gains function values. For this purpose, a program based on MATLAB is employed for the process. Validations of numerical results show that the used method is moderately satisfactory and acceptable in predicting the critical buckling force and the natural frequency of the shell in comparison with other works. As the conclusion, the effect of different weighting ratios, shell length-to-radius ratios, and shell thickness-to-radius ratios on the optimal designs are investigated and the results are compared.Thu, 18 Jun 2020 19:30:00 +0100Assessment of hydrostatic stress and thermo piezoelectricity in a laminated multilayered ...
https://macs.semnan.ac.ir/article_4464_0.html
In this paper, we built a mathematical model to study the influence of the initial stress on the propagation of waves in a hollow infinite multilayered composite cylinder. The elastic cylinder assumed to be made of inner and outer thermo piezoelectric layer bonded together with Linear Elastic Material with Voids (LEMV) layer. The model described by the equations of elasticity, the effect of the initial stress and the framework of linearized, three-dimensional theory of thermo elasticity. The displacement components obtained by founding the analytical solutions of the motion’s equations. The frequency equations that include the interaction between the composite hollow cylinders are obtained by the perfect-slip boundary conditions using the Bessel function solutions. The numerical calculations carried out for the material PZT-5A and the computed non-dimensional frequency against various parameters are plotted as the dispersion curve by comparing LEMV with Carbon Fiber Reinforced Polymer (CFRP). From the graph,it is clear that those are analyzed in the presence of hydrostatic stress is compression and tension.Thu, 18 Jun 2020 19:30:00 +0100On the nonlinear dynamics of an energy harvesting device based on magnetostriction
https://macs.semnan.ac.ir/article_4465_0.html
In this paper a magnetostrictive material (MSM) based energy harvesting device is proposed. The device is made up of a steel beam laminated with Metglas 2605sc as the magnetostrictive material; the device undergoes mechanical strain due to the external base excitation. The mechanical strain yields in a magnetic field around the beam. A pickup coil is wounded around the beam which converts magnetic field into electrical current. The equation of motion is derived based on the nonlinear Euler-Bernolli beam theory in order to account for large deflections. Kirchhoff and Faraday's laws are also benefited to couple the mechanical, magnetic and electrical field. The equation is discretized based on Galerkin method and numerically integrated over the time. Energy conservation is examined and the response in the frequency domain is obtained. In the case of initial displacement in the absence of mechanical damping, vibration amplitude attenuates as the electrical current is induced in the pickup coil; this was attributed to the attenuation of the total mechanical energy of the beam as it was harvested from the pickup coil. The temporal response was fitted to that of a single degree of freedom mass-spring-damped and the equivalent damping ratio was determined. The attenuation rate was studied with different values of resistance and number of turns in pickup coil and the relation between these two factors was obtained in order to maximize the output electrical power.Thu, 18 Jun 2020 19:30:00 +0100Electro-Elastic Analysis of Finite Length FGPM Cylinders Subjected to Electromechanical Loading ...
https://macs.semnan.ac.ir/article_4466_0.html
In this study, an analytical solution is presented based on the voltage feedback control method for the two-dimensional electro-elastic static response of functionally graded piezoelectric material (FGPM) cylinders. Using first-order shear deformation theory as well as first-order electric potential theory and applying the energy method, a differential equations system is extracted, which is solved as a classical eigenvalue problem. The results show the significant impact of heterogeneity on the electromechanical behavior of the cylinders. Furthermore, control gain affects the electric potential and electromechanical behavior of the head where the voltage is applied. The present research also introduces an analytical solution with no limitation to specific conditions in cylinder heads and without any need for convergence check. Moreover, the results show that any changes in cylinder head conditions affect the behavior of FGPM cylinders. The results were compared with those from the finite element method (FEM), leading us to a reasonable agreement.Thu, 18 Jun 2020 19:30:00 +0100Buckling analysis of Nano composite plates based on combination of the incremental load ...
https://macs.semnan.ac.ir/article_4467_0.html
In this paper, a different method, incremental load technique in conjunction with dynamic relaxation (DR) method, is employed to analyze the buckling behavior of composite plates reinforced with functionally graded (FG) distributions of single-walled carbon nanotubes (SWCNTs) along the thickness direction. The properties of carbon-nanotubes reinforced composite (CNTRC) plate were determined through modified rule of mixture. The nonlinear governing relations are obtained incrementally in the form of partial differential equations (PDEs) based on first-order shear deformation theory (FSDT) and Von Karman nonlinear strain. In the proposed method, for finding the critical buckling load, the mechanical loads are applied to the CNTRC plate incrementally so that in each load step the incremental form of PDEs are solved by the DR method combined with the finite difference (FD) discretization technique. Finally, the critical buckling load is determined from the load-displacement curve. In order to verify the accuracy of the present method, the results are compared with those available in the literatures. Finally, a detailed parametric study is carried out and results demonstrate that the change of carbon nanotube volume fraction, plate width-to-thickness ratio, plate aspect ratio, boundary condition and loading condition have pronounced effects on the buckling strength of CNTRC plates. It is seen that for all types of loading, boundary conditions and both cases of with and without presence of elastic foundation the FG-X and FG-O have the highest and lowest values of buckling loads.Thu, 18 Jun 2020 19:30:00 +0100Experimental and Numerical Investigation on the Flexural Behavior of Composite-Reinforced ...
https://macs.semnan.ac.ir/article_4468_0.html
Top-hat hollow-section beams are widely used in passenger vehicle’s body-in-white structure because of their proper shape for the montage process and also crashworthiness advantages. Hollow section beams with top-hat cross-section are mostly employed in structures like B-pillar, rocker sill, and roof rail which are engaged in side impact collisions. In the present investigation, simplified top-hat beams are developed based on a conventional B-pillar with the aim of improving energy absorption characteristics. Reinforcements are conducted by employing fiber glass-epoxy composite material. Three types of reinforced beams are presented which are either improved by composite-laminating, or by installation of an extra composite-made internal reinforcement. Experimental tests are performed in quasi-static three-point bending condition and based on results, a FE simulation is developed using LS-Dyna explicit code. Specimens are compared based on peak load, total energy absorption (TEA) and specific energy absorption (SEA) amounts. Also, to illustrate the extent of improvements, a not-reinforced top-hat beam is experimentally subjected under three-point bending test. Results depict a significant difference between the performance of beams reinforced by different methods. Comparison between specimens, considering their respective load-displacement diagram and crashworthiness characteristics, show that applying composite laminates to inside surface of a hat-shaped beam would produce a beam with satisfying flexural behavior.Thu, 18 Jun 2020 19:30:00 +0100