جستجوی مقالات مرتبط با کلیدواژه "orthotropic" در نشریات گروه "مکانیک"
تکرار جستجوی کلیدواژه «orthotropic» در نشریات گروه «فنی و مهندسی»-
In the present investigation the reflection and transmission phenomenon of plane waves between two half spaces elastic and orthotropic piezothermoelastic with two-temperature theory is discussed. A piezothermoelastic solid half space is assumed to be loaded with an elastic half space. Due to the phenomenon, four qausi waves are obtained; quasi longitudinal (qP) wave, quasi transverse (qS) wave, quasi thermal (qT) wave and electric potential wave (eP). It is found that the amplitude ratios of various reflected and refracted waves are functions of angle of incidence, frequency of incident wave and are influenced by the piezothermoelastic properties of media. The energy ratios are computed numerically using amplitude ratios for a particular model of graphite and cadmium selenide (CdSe). The variations of energy ratios with angle of incidence are shown graphically depicting the effect of two-temperature. The conservation of energy across the interface is justified. A particular case of interest is also deduced from the present investigation.Keywords: Reflection, Piezothermoelastic, Energy ratios, Transmission, Orthotropic, Amplitude ratios
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In this article, the anti-plane deformation of an orthotropic sector with multiple defects is studied analytically. The solution of a Volterra-type screw dislocation problem in a sector is first obtained by means of a finite Fourier cosine transform. The closed form solution is then derived for displacement and stress fields over the sector domain. Next, the distributed dislocation method is employed to obtain integral equations of the sector with cracks and cavities under anti-plane traction. These equations are of Cauchy singular kind, which are solved numerically by generalizing a numerical method available in the literature by means of expanding the continuous integrands of integral equations with different weight functions in terms of Chebyshoff and Jacobi polynomials. A set of examples are presented to demonstrate the applicability of the proposed solution procedure. The geometric and force singularities of stress fields in the sector are also studied and compared to the earlier reports in the literature.
Keywords: Anti-plane, Sector, Orthotropic, Stress intensity factor, Hoop stress -
A mathematical model is presented to investigate the effects of sandiness, irregular boundary interfaces, heterogeneity and viscoelasticity on the phase velocity of Love waves. Geometry of the problem is consisting of an initially stressed viscoelastic layer with corrugated irregular boundaries, which is sandwiched between heterogeneous orthotropic semi-infinite half-space with initial stress and pre-stressed dry sandy half-space. Heterogeneity arises in the upper half-space is due to trigonometric variation in elastic parameters of the orthotropic medium. Inclusion of the concept of corrugated irregular viscoelastic layer clamped between two dissimilar half-spaces under different physical circumstances such as initial stress and heterogeneity brings a novelty to the existing literature related to the study of Love wave. Dispersion equation for Love wave is obtained in closed form. The obtained dispersion relation is found to be in well agreement with classical Love wave equation. Numerical example and graphical illustrations are made to demonstrate notable effect of initial stress, internal friction, wave number and amplitude of corrugations on the phase velocity of Love waves.Keywords: Corrugation, Orthotropic, Heterogeneity, Phase velocity, Initial stress
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The occurrence of SH wave propagation under the effect of a point source in an orthotropic substratum lying over a heterogeneous orthotropic half space is deliberated in the prospect of a devastating earthquake. The quadratic alteration is acknowledged for density and shear modulus which is hypothesized to be a function of depth. The method of Green's function and transformation technique contributes to obtain the dispersion equation and dispersion curves. An effort has been accomplished to demonstrate the classical equation of Love wave followed from dispersion equation. “Mathematica” software is applied to depict the graphics. Graphics are designed to show the effect of heterogeneous parameters corresponding to density and shear modulus. Dispersion equation is obtained considering the case that the displacement and stress are continuous at the interface. The present work is an attempt to express the behavior of SH wave in an orthotropic medium under the effect of point source.Keywords: Orthotropic, SH wave, Green's function, Transformation technique, Point source
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Abstract: The solution to problem of an orthotropic long cylinder subjected to torsional loading is first obtained by means of separation valuables. The cylinder is twisted by two lateral shear tractions and the ends of the cylinder surface of the cylinder are stress-free. First, the domain under consideration is weakened by an axisymmetric rotational Somigliana ring dislocation. The dislocation solution is employed to derive a set of Cauchy singular integral equations for the analysis of multiple axisymmetric planner cracks. The numerical solution to these integral equations is used to determine the stress intensity factors (SIFs) for the tips of the concentric planar cracks A preliminary comparison between results of this study and those available in the literature is performed to confirm the validity of the proposed technique. Several examples of multiple concentric planner cracks are solved and displayed graphically. Furthermore, Configuration of the cracks and the interaction between cracks is studied.Keywords: Rotational Somigliana ring dislocation, Torsion, long cylinder, orthotropic, Axisymmetric cracks, Dislocation density
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In this paper, a numerical solution has been developed for hollow circular cylinders made up of orthotropic material which is subjected to twist using micro polar theory. The effect of twisting moment and material internal length on hollow thick-walled circular cylinder made up of micro polar orthotropic material is investigated. Finite difference method has been used to exhibit the influence of shear moduli and material internal length on shear stresses and couple stresses. It is found that the effect of small characteristic length on shear stresses is negligible and couple stresses present its significance when characteristic length is large in solid particle. The behavior of couple stresses are nonlinear for large internal length while for small internal length couple stresses are linear in nature except near the free boundaries. Torsion in hollow cylinder made up of micro polar orthotropic play vital role in the presence of cracks and holes. Therefore, torsional analysis of hollow cylinder plays important role in the field of biomechanics.Keywords: Elastic, Orthotropic, Micro polar, Characteristics length, Twist, Couple stress
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In this paper the radial deformation and the corresponding stresses in a functionally graded orthotropic hollow cylinder with the variation in thickness and density according to power law and rotating about its axis under pressure is investigated by using Seth's transition theory. The material of the cylinder is assumed to be non-homogeneous and orthotropic. This theory helps to achieve better agreement between experimental and theoretical results. Results has been mentioned analytically and numerically. From the analysis, it has been concluded that cylinder made up of orthotropic material whose thickness increases radially and density decreases radially is on the safer side of the design as circumferential stresses are high for cylinder made up of isotropic material as compared to orthotropic material. This paper is based on elastic-plastic behavior which plays important role in practical design of structures for safety factor.Keywords: Elastic, plastic, Orthotropic, Pressure, Functionally graded material, Cylinder.
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The present investigation analysis a problem of reflection and transmission at an interface of two micropolar orthotropic piezothermoelastic media. The basic equations and constitutive relations for micropolar orthotropic piezothermoelastic media for G-L theory are derived. The expressions for amplitude ratios corresponding to reflected and transmitted waves are derived analytically. The effect of angle of incidence, frequency, micropolarity, thermopiezoelectric interactions on the reflected and transmitted waves are studied numerically for a specific model. Some special cases of interest one are also deduced.Keywords: Orthotropic, Micropolar, Piezothermoelastic, Amplitude ratios, Angle of incidence
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In this paper, static and free vibrations behaviors of the orthotropic functionally graded material (FGM) plates resting on the two-parameter elastic foundation are analyzed by the a mesh-free method based on the first order shear deformation plate theory (FSDT). The mesh-free method is based on moving least squares (MLS) shape functions and essential boundary conditions are imposed by transfer function method. The orthotropic FGM plates are made of two orthotropic materials and their volume fractions are varied smoothly along the plate thickness. The convergence of the method is demonstrated and to validate the results, comparisons are made with finite element method (FEM) and the others available solutions for both homogeneous and FGM plates then numerical examples are provided to investigate the effects of material distributions, elastic foundation coefficients, geometrical dimensions, applied force and boundary conditions on the static and vibrational characteristics of the orthotropic FGM plates.Keywords: Static, Free vibration, FGM plate, Orthotropic, Mesh, free
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بسیاری از اشیاء مادی، مانند پارچه و کاغذ، به صورت ورقه های نازکی به نام «غشاء» تولید می شوند. از آنجا که این مواد در مقابل خمش و فشار مقاومتی نشان نمی دهند در معرض چین خوردگی قرار دارند. اغلب این غشاها دارای خواص ارتوتروپ هستند؛ یعنی در جهات متفاوت خواص آنها تفاوت دارد. در این تحقیق به دنبال بررسی تاثیر خواص ارتوتروپیک ورق بر چین خوردگی آن هستیم. بدین منظور ضمن معرفی شیوه های مختلف تحلیل نظری و شبیه سازی رایانه یی با انتخاب یک مسئله ی عمومی درمورد بارگذاری غشاء ارتوتروپ، تاثیر عوامل مختلف بر چین خوردگی غشاء مطالعه می شود. روش تحلیلی مورد استناد در رویکرد نظری، مبتنی بر تحلیل غشایی رادمن است. در این تحقیق اثر میزان انحراف راستای بار از امتداد محورهای مادی غشاء، میزان کشیدگی و نسبت خواص ارتجاعی راستاهای اصلی غشاء بر دامنه ی چین، تعداد، عمق و راستای آن ها بررسی و نهایتا، نتایج در قالب تعدادی نمودار ارائه شده است.
کلید واژگان: غشاء, ارتوتروپ, چین خوردگی, الگوی چین, روش رادمن, آباکوسEvery day, we use different objects in the shape of thin sheets or membranes. Papers, plastic bags, wrappings, and different kinds of textile, such as cloths, tents, and rugs, are among the best examples of membranes. Moreover, in most cases, the mechanical strength of these objects is their best characteristic. Safari or awning tents, parachutes and sports costumes are examples of membranes whose applications are somehow mechanically oriented. Yet, much more specifically, in many instances, the membranes are not isotropic. Good examples of these cases are polymeric synthetic cloths and thin rolled sheets of metal. One of the main aspects in the behavior of membranes is their wrinkling phenomenon. In fact, these objects cannot withstand different kinds of loadings, such as compressive and shear forces, as well as bending moments and, consequently, are very susceptible to a mode of failure known as wrinkling. There are different approaches to studying the mechanics of membranes. Many strategies used in these studies are based on the assumption of plane stress conditions. Obviously, these studies must assume that membranes cannot carry shear or compressive forces. One of the main approaches in this category is the Roddeman method. The method pointed out in the paper is used to analyze the wrinkling of an orthotropic membrane. Down to their structural composition under stretch forces, these types of membrane are more vulnerable than their isotropic relatives. The results obtained by using the theoretical approach of Roddeman are represented in the form of different tables, graphs and figures. In this analysis, both assumptions of small and large fields of deformation are used. The analytical modeling and solutions are supported by different simulations obtained using ABAQUS software. The results reveal how the change of loading direction can affect the orientation of the wrinkles. Moreover, the effects of load level and anisotropy on the depth of the wrinkles are studied.
Keywords: membrane, orthotropic, wrinkling, wrinkling pattern, Roddemans method, ABAQUS -
نشریه شبیه سازی و تحلیل تکنولوژی های نوین در مهندسی مکانیک، سال هفتم شماره 3 (زمستان 1393)، صص 35 -43تحلیل کمانشی پوسته های استوانه ای جدار نازک به دلیل فرآیند ساخت آن ها دارای اهمیت ویژه ای می باشند. برای افزایش استحکام کمانشی معمولا از تقویت کننده های طولی و عرضی استفاده می شود.در این مقاله با در نظر گرفتن یک پوسته استوانه ای جدار نازک تقویت شده با تقویت کننده های طولی و عرضی داخلی، تحت ترکیب نیروهای محوری و فشار جانبی، به بررسی تاثیر نسبت نیروی محوری به نیروی جانبی بر مقدار نیروی کمانش برای نسبت های مختلف ابعادی اعم از نسبت ضخامت به شعاع و نسبت طول به شعاع پوسته استوانه ای پرداختیم. نتایج تحلیلی بر مبنای معادلات پایداری خطی کلاسیک دانل برای پوسته های استوانه ای غیر همسانگرد، با نتایج برآمده از تحلیل المان محدود به وسیلهنرم افزارANSYSمقایسه شد.نتایج نشان می دهد روش تحلیلی دانل در محدوده ای از نسبت های ابعادی کارایی دارد. همچنین در اکثر نسبت های ابعادی،با افزایش نسبت نیروی محوری به نیروی محیطی، نیروی کمانش محوری افزایش و نیروی کمانش محیطی کاهش می یابد.
کلید واژگان: المان محدود, اورتوتروپیک, پوسته های استوانه ای, کمانش, نسبت نیروی محوری به فشار جانبیBuckling analysis of thin cylindrical shells is very important due to their production process. Usually longitudinal and transversal stiffeners are used to increase the buckling stiffness. In this paper, considering a thin cylindrical shell with longitudinal and transversal ribs subjected to axial force and lateral pressure, the influence of different aspect of axial force to lateral pressure on buckling load is investigated for different ratios such as thickness to radius and length to radius. The analytical results based on Donnell’s classical linear stability equations for anisotropic cylindrical shells are compared with FEM results of ANSYS software. The results show that the analytical method of Donnell can be used for special aspect ratios. Furthermore, by increasing the axial to lateral load ratio, the axial buckling load is increased for most of the aspect ratios, while the lateral buckling load decreases.Keywords: FEM, cylindrical shells, Buckling, axial load to lateral pressure ratio, orthotropic -
این مقاله، تحلیل خطی و غیرخطی کمانش صفحات نسبتا ضخیم دایروی/حلقوی گرافن با خواص ارتوتروپیک بر پایه الاستیک تحت بار مکانیکی مورد بررسی قرار می گیرد. به کمک ری ا ، اصل کار مجازی، تئوری مرتبه اول برشی و کرنش های غیرخطی فون-کارمن، روابط حاکم برحسب جابجایی–ها بدست آمده و از روش مربعات دیفرانسیلی (DQ) همراه با توزیع غیریکنواخت نقاط (چیبشف-گوس-لوباتو) استفاده شده است. برای اعتبار سنجی، نتایج بدست آمده با نتایج کمانش در مراجعدیگر مقایسه شده و اثرات ضریب غیرموضعی، ضخامت، شعاع و پایه الاستیک، بر بارهای بی بعد کمانش مورد بررسی قرار گرفته است و همچنین نتایج تحلیل به روش تئوری غیر موضعی و موضعی با یکدیگر مقایسه شده اند. از نتایج مشاهده می شود که بار بی بعد کمانش صفحات گرافن با کاهش انعطاف پذیری از نظر شرط مرزی، با افزایش ضریب غیرموضعی، افزایش بیشتری می یابد و همچنین با افزایش شعاع صفحه، اختلاف نتایج تحلیل غیر موضعی و موضعی بیشتر می شود.
کلید واژگان: کمانش, صفحه دایروی, حلقوی, ارتوتروپیک, تئوری غیرموضعی الاستیسیته, روش مربعات دیفرانسیلیIn this paper، analysis of linear and nonlinear buckling of relatively thick orthotropic graphene sheets is carried out under mechanical load based on elasticity theories. With the help of nonlocal elasticity theory، the principle of virtual work، first order shear theory and Von-Karman nonlinear strain، the dominant relationship in terms of obtained displacements has been obtained، and the method of differential quadrature (DQ) with non-uniform distribution points (Chebyshev -Gauss-Lobato) has been used. To check the validity، the obtained results have been compared with other resources، and the effects of nonlocal coefficient، thickness، radius and elastic base on the dimensionless buckling loads were calculated and investigated. Moreover، the results of analysis using nonlocal and local theory were compared together. It can be noticed that the dimensionless buckling loads on graphene sheets increased more with a decrease in flexibility as far boundary condition is concerned. Additionally، with an increase in the sheet radius، the variation between nonlocal and local analysis results will be more.Keywords: Buckling, Graphene sheets, orthotropic, Nonlocal elasticity theories, Method of differential quadrature (DQ) -
In this paper, free vibration analysis of orthotropic functionally graded material (FGM) cylinders was carried out by a Mesh-Free method. In this analysis, moving least squares shape functions are used for approximation of displacement field in the weak form of equilibrium equation. Essential boundary conditions are imposed by transformation method. In this simulation, an axisymmetric model is used. The orthotropic FGM cylinders are assumed to be a mixture of two isotropic materials as fiber and matrix. The volume fraction of the fiber is changed in the radial direction. Consequently, mechanical properties of these cylinders are changed in the radial direction. Free vibration analysis of orthotropic FGM cylinders with any arbitrary combination of boundary conditions is possible by the proposed model. Natural frequencies obtained from the presented model are in good agreement with results of finite element simulation and other results from literature. Effects of various types of boundary conditions, geometrical parameters, and mechanical properties on the natural frequencies are studied.Keywords: FGM, Orthotropic, Mesh, free, Axisymmetric, Free vibration
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Iranian Journal of Mechanical Engineering Transactions of ISME, Volume:8 Issue: 2, Mar 2008, PP 26 -40This research presents a semi analytical solution of finitely long, simplysupported, orthotropic, piezoelectric, radially polarized, shellpanel under pressure and electrostatic excitation. The general solutionof the governing partial differential equations are obtained bythe method of separation of variables. The displacements and electricpotential are expanded in appropriate trigonometric Fourier seriesin the circumferential and axial coordinate to satisfy the boundaryconditions at the simply-supported circumferential and axialedges. The governing ordinary differential equations are solved bythe Galerkin finite element method. In this procedure, the quadraticshape function is used in each element. Numerical examples are providedfor typical external pressure on outer surface of a single layerpiezoelectric panel.Keywords: linear piezoelectric, finitely long, Cylindrical panel, orthotropic, radially polarized, simply-supported
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