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دسترسی آزاد مقاله
1 - Fitness for Service Approach (FFS) in Fatigue Life Prediction for a Spherical Pressure Vessel Containing Cracks
J Jamali E Mohamadi T NaraghiDuring the pressure vessels' operating life several flaws are likely to grow in long term operations under cyclic loading. It is therefore essential to take practical and predictive measures to prevent catastrophic events to take place. Fitness for service (FFS) is one چکیده کاملDuring the pressure vessels' operating life several flaws are likely to grow in long term operations under cyclic loading. It is therefore essential to take practical and predictive measures to prevent catastrophic events to take place. Fitness for service (FFS) is one safety procedure that is used to deal with maintenance of components in the petroleum industry. In this method, proposed in Codes of practices such as API 579 and BSI 7910, in certain cases, an overly conservative safety prediction is obtained when applied to the operation of pressure vessel containing surface fatigue crack growth. By using improved analytical techniques as well as nonlinear finite element methods critical cracks lengths may be derived more accurately thus reducing conservatism. In this paper, a specific pressure vessel analyzed for fitness for service which sees fatigue crack growth rate is assessed using analytical and numerical stress intensity factors. The estimated fatigue life is compared with both methods. It is found that both approaches give similar predictions within a range of scatter assuming that the fatigue properties used are the same in both cases. However, it can be said that the numerical approach gave the more conservative predictions suggesting a detailed analysis is always preferable in FFS examinations. پرونده مقاله -
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2 - Three-Dimensional Stress Analysis for Semi-Elliptical Cracks in the Connection of Cylinder-Hemispherical Head for Thick-Walled Cylindrical Pressure Vessels
H Eskandari M Ghanbari F MirzadehThese pressure vessels are made by different type of heads. One of them is hemi-spherical head. The area of geometrical discontinuity, like the connection of the cylinder to its hemi-spherical head, are the most susceptible areas for crack initiation along their welds. چکیده کاملThese pressure vessels are made by different type of heads. One of them is hemi-spherical head. The area of geometrical discontinuity, like the connection of the cylinder to its hemi-spherical head, are the most susceptible areas for crack initiation along their welds. So it is worthwhile to consider cracks located at this connection. The purpose of this article is to investigate the effect of variation of stress field and geometry of problem on distribution of Stress Intensity Factor (SIF) for a semi-elliptical surface crack which is located at the connection of cylinder to its hemispherical head. The three dimensional finite element analysis is performed by employing singular elements along the crack front. The ratio of crack depth to crack length (a/c) ranged from 0.3 to 1.2; the ratio of crack depth to wall thickness (a/t)ranged from 0.2 to 0.8; and the cylinder geometry parameter of vesselranged from 1.2 to 2. For better comparison the results are normalized and reported in non-dimensional formats. The results show that the crack configuration, vessel thickness and radius have significant influence on the stress intensity factor distribution along the crack front. Also For a fixed and the maximum value of SIF occur in the cylindrical part and approximately near the deepest point of crack; not on the deepest point of crack depth and this may be due to changing stress field in this connection. The stress intensity factors are presented in suitable curves for various geometrical configurations providing useful tool for the fracture mechanics design of cracked pressure vessels. پرونده مقاله -
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3 - Analytical and Numerical Investigation of FGM Pressure Vessel Reinforced by Laminated Composite Materials
A.R Ghasemi A Kazemian M MoradiIn this research, the analytical and numerical investigation of a cylindrical shell made of functionally graded materials (FGMs) reinforced by laminated composite subjected to internal pressure is presented. Using the infinitesimal theory of elasticity, the analytical s چکیده کاملIn this research, the analytical and numerical investigation of a cylindrical shell made of functionally graded materials (FGMs) reinforced by laminated composite subjected to internal pressure is presented. Using the infinitesimal theory of elasticity, the analytical solution of stress and strain in vessels made of FGMs is studied first. It is assumed that the elasticity modulus follows a power law distribution in the thickness direction and Poisson's ratio considered to be constant for simplicity. The results of the finite element method using ABAQUS software for in-homogeneity constant in the range of -2 to 2 have been compared with the analytical results. The comparison represents good coincidence between analytical and numerical results and confirms the accuracy of stress and strain solutions presented for vessel made of FGMs. The stress and strain solutions in laminated composite vessels are then investigated. Finally, modeling of FGM vessel reinforced by composite laminates with different lay-up is taken into consideration. The obtained results demonstrate that in the cylindrical shell reinforced by laminated composites, the maximum stress is considerably less than the maximum stress in the pressure vessels made of just composites or FGMs. پرونده مقاله -
دسترسی آزاد مقاله
4 - A Semi-analytical Approach to Elastic-plastic Stress Analysis of FGM Pressure Vessels
A.T Kalali S Hadidi-MoudAn analytical method for predicting elastic–plastic stress distribution in a cylindrical pressure vessel has been presented. The vessel material was a ceramic/metal functionally graded material, i.e. a particle–reinforcement composite. It was assumed that th چکیده کاملAn analytical method for predicting elastic–plastic stress distribution in a cylindrical pressure vessel has been presented. The vessel material was a ceramic/metal functionally graded material, i.e. a particle–reinforcement composite. It was assumed that the material’s plastic deformation follows an isotropic strain-hardening rule based on the von-Mises yield criterion, and that the vessel was under plane-stress conditions. The mechanical properties of the graded layer were modelled by the modified rule of mixtures. By assuming small strains, Hencky’s stress–strain relation was used to obtain the governing differential equations for the plastic region. A numerical method for solving those differential equations was then proposed that enabledthe prediction of stress state within the structure. Selected finite element results were also presented to establish supporting evidence for the validation of the proposed analytical modelling approach. Similar analyses were performed and solutions for spherical pressure made of FGMs were also provided. پرونده مقاله -
دسترسی آزاد مقاله
5 - Semi Analytical Analysis of FGM Thick-Walled Cylindrical Pressure Vessel with Longitudinal Variation of Elastic Modulus under Internal Pressure
M Shariati H Sadeghi M Ghannad H GharooniIn this paper, a numerical analysis of stresses and displacements in FGM thick-walled cylindrical pressure vessel under internal pressure has been presented. The elastic modulus is assumed to be varying along the longitude of the pressure vessel with an exponential func چکیده کاملIn this paper, a numerical analysis of stresses and displacements in FGM thick-walled cylindrical pressure vessel under internal pressure has been presented. The elastic modulus is assumed to be varying along the longitude of the pressure vessel with an exponential function continuously. The Poisson’s ratio is assumed to be constant. Whereas most of the previous studies about FGM thick-walled pressure vessels are on the basis of changing material properties along the radial direction, in this research, elastic analysis of cylindrical pressure vessel with exponential variations of elastic modulus along the longitudinal direction, under internal pressure, have been investigated. For the analysis of the vessel, the stiffness matrix of the cylindrical pressure vessel has been extracted by the usage of Galerkin Method and the numerical solution for axisymmetric cylindrical pressure vessel under internal pressure have been presented. Following that, displacements and stress distributions depending on inhomogeneity constant of FGM vessel along the longitudinal direction of elastic modulus, are illustrated and compared with those of the homogeneous case. The values which have been used in this study are arbitrary chosen to demonstrate the effect of inhomogeneity on displacements and stress distributions. Finally, the results are compared with the findings of finite element method (FEM). پرونده مقاله -
دسترسی آزاد مقاله
6 - A Novel Finite-Element-Based Algorithm for Damage Detection in the Pressure Vessels Using the Wavelet Approach
N Haghshenas A.H Ghorbanpour Arani A Javanbakht M KarimiIn this investigation a suitable algorithm for the detection of cracks in the pressure vessels is presented. The equations of motion for the vessel are obtained and transferred into the wavelet space in a simplified form resulted from time and position approximations. T چکیده کاملIn this investigation a suitable algorithm for the detection of cracks in the pressure vessels is presented. The equations of motion for the vessel are obtained and transferred into the wavelet space in a simplified form resulted from time and position approximations. The locations of cracks are randomly distributed in different regions of the structure to cover the whole geometry of the pressure vessel. Furthermore, the pressure vessel is installed vertically with a fixed end at the bottom of each of its four leg supports. Then, the results are transferred to the wavelet space using Daubechies wavelet families. From the comparison of the displacement results associated with the intact and damaged vessels, it can be clearly seen that the crack location can be accurately detected noting the alteration in the wavelet output diagrams .The results of the crack detection show that with the proper selection of the wavelet type, the wavelet based finite element method is a suitable and nondestructive method as well as a powerful numerical tool for the detection of cracks and other discontinuities in the pressure vessels. The results of this investigation can be used in the marine and aerospace industries as well as power stations. پرونده مقاله -
دسترسی آزاد مقاله
7 - Fracture Analysis of Externally Semi-Elliptical Crack in a Spherical Pressure Vessel with Hoop-Wrapped Composite
H Eskandari Gh Rashed F MirzadeIn this paper the effect of composite hoop-wrapped on stress intensity factor for semi-elliptical external crack which located in spherical pressure vessel, were investigated through the Finite Element Analysis. In order to find the effect of some parameters such as com چکیده کاملIn this paper the effect of composite hoop-wrapped on stress intensity factor for semi-elliptical external crack which located in spherical pressure vessel, were investigated through the Finite Element Analysis. In order to find the effect of some parameters such as composite thickness and width, internal pressure and crack geometry, comparisons between different cases were done and discussed in detail. The result show that repairing crack with composite hoop-wrapped, can significantly reduce the stress intensity factor along the crack front. پرونده مقاله -
دسترسی آزاد مقاله
8 - Constrained Multi-Objective Optimization Problems in Mechanical Engineering Design Using Bees Algorithm
A Mirzakhani Nafchi A MoradiMany real-world search and optimization problems involve inequality and/or equality constraints and are thus posed as constrained optimization problems. In trying to solve constrained optimization problems using classical optimization methods, this paper presents a Mult چکیده کاملMany real-world search and optimization problems involve inequality and/or equality constraints and are thus posed as constrained optimization problems. In trying to solve constrained optimization problems using classical optimization methods, this paper presents a Multi-Objective Bees Algorithm (MOBA) for solving the multi-objective optimal of mechanical engineering problems design. In the present study, a satellite heat pipe design, a space truss design and pressure vessel problems are considered. Multi-objective optimization using the bees algorithm which is a new multi-object obtain a set of geometric design parameters, leads to optimum solve. This method is developed in order to obtain a set of geometric design parameters leading to minimum heat pipe mass and the maximum thermal conductance. Hence, a set of geometric design parameters, lead to minimum pressure total cost and maximum pressure vessel volume. Numerical results reveal that the proposed algorithm can find better solutions when compared to other heuristic or deterministic methods and is a powerful search algorithm for various engineering optimization problems. پرونده مقاله -
دسترسی آزاد مقاله
9 - Time-Dependent Hygro-Thermal Creep Analysis of Pressurized FGM Rotating Thick Cylindrical Shells Subjected to Uniform Magnetic Field
A Bakhshizadeh M Zamani Nejad M Davoudi KashkoliTime-dependent creep analysis is presented for the calculation of stresses and displacements of axisymmetric thick-walled cylindrical pressure vessels made of functionally graded material (FGM). For the purpose of time-dependent stress analysis in an FGM pressure vessel چکیده کاملTime-dependent creep analysis is presented for the calculation of stresses and displacements of axisymmetric thick-walled cylindrical pressure vessels made of functionally graded material (FGM). For the purpose of time-dependent stress analysis in an FGM pressure vessel, material creep behavior and the solutions of the stresses at a time equal to zero (i.e. the initial stress state) are needed. This corresponds to the solution of the problem considering linear elastic behavior of the material. Therefore, using equations of equilibrium, stress–strain and strain–displacement, a differential equation for displacement is obtained and subsequently the initial elastic stresses at a time equal to zero are calculated. Assuming that the Magneto-hygro-thermoelastic creep response of the material is governed by Norton’s law, using the rate form of constitutive differential equation, the displacement rate is obtained and then the stress rates are calculated. Once the stress rates are known, the stresses at any time are calculated iteratively. The analytical solution is obtained for the plane strain condition. The pressure, inner radius and outer radius are considered to be constant and the magnetic field is uniform. Material properties are considered as power law function of the radius of the cylinder and the poisson’s ratio as constant. Following this, profiles are plotted for different values of material exponent for the radial, circumferential and effective stresses as a function of radial direction and time. The in-homogeneity exponent have significant influence on the distributions of the creep stresses. پرونده مقاله -
دسترسی آزاد مقاله
10 - Three-Dimensional Finite Element Analysis of Stress Intensity Factors in a Spherical Pressure Vessel with Functionally Graded Coating
H EskandariThis research pertains to the three-dimensional (3D) finite element analysis (FEA) of the stress intensity factors (SIFs) along the crack front in a spherical pressure vessel coated with functionally graded material (FGM). The vessel is subjected to internal pressure an چکیده کاملThis research pertains to the three-dimensional (3D) finite element analysis (FEA) of the stress intensity factors (SIFs) along the crack front in a spherical pressure vessel coated with functionally graded material (FGM). The vessel is subjected to internal pressure and thermal gradient. The exponential function is adopted for property of FGMs. SIFs are obtained for a wide variety of crack shapes and layer thickness. The reported results clearly show that the material gradation of coating and the crack configuration can significantly affect the variation of SIFs along the crack front. The results are given which are applicable for fatigue life assessment and fracture endurance of FGM coating spherical pressure vessel and can be used in design purposes. پرونده مقاله -
دسترسی آزاد مقاله
11 - Effect of Material Gradient on Stresses of Thick FGM Spherical Pressure Vessels with Exponentially-Varying Properties
Mohammad Nejad Mahboobeh GharibiUsing the Frobenius series method (FSM), an analytical solution is developed to obtain mechanical stresses of thick spherical pressure vessels made of functionally graded materials (FGMs). The cylinder pressure vessel is subjected to uniform internal pressure. The modul چکیده کاملUsing the Frobenius series method (FSM), an analytical solution is developed to obtain mechanical stresses of thick spherical pressure vessels made of functionally graded materials (FGMs). The cylinder pressure vessel is subjected to uniform internal pressure. The modulus of elasticity is graded along the radial direction according to power functions of the radial direction. It is assumed that Poisson’s ratio is constant across the cylinder thickness. Primarily, displacements and stresses is obtained as closed-form solutions. Next, the profiles are plotted for different values of inhomogeneity constant along the radial direction. Finally, the problem was solved, using the finite element method (FEM). The obtained results of finite element method were compared with those of the analytical method. The analytical solutions and the solutions carried out through the FEM show good agreement. The values used in this study are arbitrary chosen to demonstrate the effect of inhomogeneity on displacements, and stresses distributions. پرونده مقاله -
دسترسی آزاد مقاله
12 - Creep and Stress Redistribution Analysis of Thick-Wall FGM Spheres Subjected to Mechanical Load and Heat Flux – An Analytical Approach
Ali Ziaei-Asl Mohammad Reza Saviz Javad PourabdollahIn this paper, creep analysis of a thick-walled spherical pressure vessel made of Functionally Graded Material (FGM) under thermo-mechanical loadings has been investigated based on Bailey-Norton Law. Considering the nonlinearity of the creep behavior, there is no analyt چکیده کاملIn this paper, creep analysis of a thick-walled spherical pressure vessel made of Functionally Graded Material (FGM) under thermo-mechanical loadings has been investigated based on Bailey-Norton Law. Considering the nonlinearity of the creep behavior, there is no analytical solution that can accurately determine the stresses of an FGM as a function of time and thermal boundaries, thus in this paper, a new method based on the Taylor Series expansion of the creep strain rate is developed to solve the Beltrami-Michell equation by employing an asymptotic method. The resulting quantities are compared with the numerical ones and show good accuracy. The impacts of FGM constants and wall-thickness, and series order on the creep stress and strain distributions are evaluated. The results are depicted graphically and reveal that even for vessels with high wall thickness and FGM constants, the proposed method equipped with high orders of the Taylor series produces accurate results. Also, due to the agreement of both numerical and analytical methods, this method can be generalized to study the creep of other symmetric FGM structures. پرونده مقاله -
دسترسی آزاد مقاله
13 - Effect of Different FGM Models on Creep Analysis of Thick-walled Cylindrical Pressure Vessel
Fakher Abdolkhani Mohammad Hashemian Farshid Aghadavoudi Nabard HabibiThick-walled cylindrical vessels are used widely in petrochemical and power plants. New additive manufacturing technology has made it possible to make FGMs. This research studies the creep analysis in the cylindrical FGM pressure vessel by considering three models and y چکیده کاملThick-walled cylindrical vessels are used widely in petrochemical and power plants. New additive manufacturing technology has made it possible to make FGMs. This research studies the creep analysis in the cylindrical FGM pressure vessel by considering three models and yield criteria. Also, the governing equations were extracted by considering the FGM models, and for determining creep stresses, the partial differential equations, were solved. Norton's equation is used to determine creep strain rates. The advantage of the exponential model is that in the inner radius for all n radial and circumferential creep strains rates have a constant value that is maintained by increasing the internal pressure up to 400 MPa. The graphs are smooth, and their values tend to zero in the outer radius. The changes of creep strain rate in terms of n in different internal pressures for the exponential model in the inner radius of the vessel show that increasing n from -4 to 0, these parameters have a reduction to the form of an exponential function, and the slope of the graph has the highest value at 360 MPa. پرونده مقاله -
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14 - Seismic Evaluation and Strengthening of Vertical and Horizontal Pressure Vessels in a Refining Complex
Hossein Kazem Mahmood MinavandPressure vessels are one of the most important equipment in the refining of the crude oil. For this reason, these equipment must be resist against the loads resulting from the earthquake.Pressure vessels are found in different units of refineries and in different vertic چکیده کاملPressure vessels are one of the most important equipment in the refining of the crude oil. For this reason, these equipment must be resist against the loads resulting from the earthquake.Pressure vessels are found in different units of refineries and in different vertical and horizontal shapes. These equipment are locating on different foundation and their seismic behavior are quite different. For seismic study of pressure vessels, at first this equipment must be screened and categorized in order to find their real behavior. The selected sample should be a sample that in comparing to others must have critical condition in terms of seismic vulnerabilities.According to the qualitative studying, mechanical specifications such as dimensions, temperature, weight, and the dimensions of the foundation will be determined.After analytical modeling and calculations the amount of vessel vulnerabilities will be found. All the modeling is done with the SAP2000 and SAFE2000 softwares. For modal and spectrum dynamic analysis shell elements and frame elements is used.After analysis is done, the stresses and the displacement in the body of vessel and also stresses in pedestal and bolts will be determined and then compared to the allowable values. At the end those elements which have no adequate strength, will be retrofitted and all drawing and details will be presented. پرونده مقاله -
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15 - Comprehensive overview of creep deformation of thick-walled FGM pressure vessels
مصطفی امیدی بیدگلیToday, the use of functional graded materials in various industries has received much attention. One of the fields of application of FGM materials in the construction of thick-walled tanks. Thick-walled tanks, due to their high pressure and temperature, need to be made چکیده کاملToday, the use of functional graded materials in various industries has received much attention. One of the fields of application of FGM materials in the construction of thick-walled tanks. Thick-walled tanks, due to their high pressure and temperature, need to be made of higher strength materials such as FGM materials and reinforced to increase load bearing, which is one of the best reinforcement methods using autofertilization process. It enters the plastic area from the tank under a certain load and causes residual stress after applying the process in the tank.On the other hand, the creep phenomenon eventually leads to creep rupture, which occurs either by a soft mechanism that occurs in the form of two large strains or by the brittleness of the material.The purpose of studying the creep rupture of reservoirs is to study their creep failure during their expected service life. In this article, while expressing the relevant concepts, a comprehensive review of research in this field is provided پرونده مقاله
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