۱Fuzzy Finite Element Analysis of Structures
نویسنده(ها): ،
اطلاعات انتشار: ششمین کنفرانس بین المللی مهندسی عمران، سال
تعداد صفحات: ۸
Fuzzy finite element analysis of structures is applied to the problems, uncertain parameters. In this article fuzzy numbers are used for uncertain parameters and fuzzy finite element method is formulated for static analysis using fuzzy analysis. Interval analysis is used to solve the system of linear interval equations and a modified interval search procedure is used to reduce overestimations. For verification of the proposed modified procedure static analysis of a bar structure is treated with fuzzy finite element method.<\div>

۲STRESS CONCENTRATION PHENOMENA IN THE VICINITY OF CYLINDER–TO–CYLINDER INTERSECTION REGIONS
نویسنده(ها):
اطلاعات انتشار: ششمین کنفرانس بین المللی مهندسی عمران، سال
تعداد صفحات: ۸
Intersecting cylindrical shells are frequently encountered in various types of engineering structures. Despite their common occurrence, reliable and accurate analytical methods have not been generally available. To contribute to the understanding of the stress concentration phenomena and possible solutions for them, finite element analyses are carried out for shells with holes, shells with reinforced holes and cylinder–to–cylinder intersections. The overall agreement between the finite element predictions and experimental results is a very good one. It has been shown that by using the finite element method together with a "mesh generation" technique, both computational efficiency and minimum user time can be retained.<\div>

۳A Finite Element Formulation Based on 3D Degenerated Shell Element for Analysis of Functionally Graded Shells
نویسنده(ها): ،
اطلاعات انتشار: ششمین کنفرانس بین المللی مهندسی عمران، سال
تعداد صفحات: ۸
A finite element formulation based on the 3–D degenerated shell element with 40 degrees of freedom is derived for the analysis of the thermoelastic behavior of functionally graded shells. The element accounts for the varying elastic and thermal properties through the thickness by an integration through–the–thickness routine. The nonlinear heat transfer equation governing the through–the–thickness thermal distribution is treated using the Rayleigh–Ritz method. Two examples of functionally graded structures are examined. The effect of the volume fraction of the constituent materials and the order of the Rayleigh–Ritz trial function to solve the nonlinear heat equation are also investigated<\div>

۴Finite Element Analyses of Masonry Shear Walls
نویسنده(ها): ،
اطلاعات انتشار: دومین کنگره ملی مهندسی عمران، سال
تعداد صفحات: ۹
In this paper examples of Finite Element analyses of un–reinforced single leaf clay brick\concrete block masonry shear walls with or without opening, under a non–proportional confined vertical and monotonic lateral loadings are presented. In the FE detailed modelling of these structures, full units (bricks\blocks) are modelled with two conventional 8–noded continuum elements, while 6–noded continuum elements– instead of mortar joints– are used to capture masonry failure mechanisms in the 2D plane–strain analyses. Brick–mortar interface characteristics act in the mortar element material plasticity algorithm which includes softening for cohesion parameter of the shear mode. In case of crack modelling in the unit elements, a simple plasticity material model was used. The above numerical solution algorithm which includes the effective parameters in the masonry response, provided great abilities for the FEM to trace entire response of the masonry shear walls in their path loads (up to and beyond the peak load until total degradation of strength), crack pattern and deformation, and also the failure process, all in a good and reasonable estimate of the experimental results.<\div>

۵بررسی اثر وضعیت ناپیوستگی ها بر اندرکنش سد قوسی با پی سنگی
اطلاعات انتشار: چهارمین کنفرانس سد‌سازی ایران، سال
تعداد صفحات: ۱۳
در این تحقیق، تاثیر پارامترها ی ژئوتکنین ی بر اندرکنش سد دو قوس ی با تکیه گاه و پی سنگی بررسی شده است. پارامترهای مورد بررس ی قرار گرفته عبارت بودن د از : زاویه ناپیوستگی، فاصله لایه ها و تعداد درزه ها ، که متغیر سوم بدلیل پیچیدگی در مدل کردن بصورت یک حالت خاص بررس ی شده است . در کلیه حالتها امتدا د ٣ لایه ها مواز ی با محور رودخانه بود و کلیه زاویه ها ی لایه بندی ممکن با این امتداد با گام پانزده درجه مورد بررسی قرار گرفت. برای تحلیل مدلها از برنامه ANSYS استفاده شده است. در مجموع، در این پژوهش ۵۷ مدل با بیش از ۲۱۰ هزار المان هشت گره ی ( بدون المانها ی مرزی ناپیوستگی) با حدود یک گیگا بایت فایلهای اطلاعات ی مختلف ایجاد شده اند و بیش از پنج هزار خط برنامه برا ی ایجاد مدلها و تحلیل و بررسی نتایج آنها، محاسبه ضرایب اطمینان، ترسیم منحن ی ها و کانتورهای مربوطه و … نوشته شده است. نتایج بدست آمده، اطلاعات ارزشمندی را در زمینه لایه بندی مناسب و نامناسب در تکیه گاه و پی مشخص می سازند و کلیه این نتایج، منطقی و قابل انتظار و منطبق بر اصول مکانیک سنگ هستند.

۶Nonlinear Finite Element Analysis of RC Shear Walls with Diagonal Web Reinforcement
نویسنده(ها): ،
اطلاعات انتشار: هفتمین کنگره بین المللی مهندسی عمران، سال
تعداد صفحات: ۸
Shear walls are used extensively in high–and medium–rise buildings to resist lateral loads induced by earthquake. The seismic performance of many buildings is , therefore, closely, involved to the behavior of the reinforced concrete shear walls. Shear failure of a shear wall during an earthquake has been documented by the results of laboratory tests. Walls display pinched histeresis curves and may exhibit a sudden loss in lateral load capacity due to web crushing. Nevertheless, most design procedures for shear walls ignore due to web crushing . Nevertheless , most design procedures for shear walls ignore these key aspects of the nonlinear response. In this paper, nonlinear finite element method is used to study the behavior of reinforced concrete shear walls subjected to lateral load. The analytical models used in this paper were developed specifically to study the push–over response of reinforced concrete shear walls, and may be used to investigate the influence of web reinforcement on laterally loaded shear walls. Material models for concrete and reinforcing steel that are capable of reproducing the features of nonlinear response of walls are also discussed . The models ore validated by comparing the analytical results with the experimental results of shear walls tested by Vecchio and Palermo. Emphasis is placed on selecting web reinforcement to minimize the likelihood of shear failure. Diagonal reinforcement in the web is identified as an efficient means of limiting shear distortion and reducing the likelihood of shear failures in shear walls.<\div>

۷THE URFTM ASONRDYA M, THREEDIMENSIONAL STABILITY ANALYSES, MONITORING AND COMPARISON OF RESULTS
نویسنده(ها):
اطلاعات انتشار: اولین کنفرانس مکانیک سنگ ایران، سال
تعداد صفحات: ۱۶
The masonry dam of the Urft reservoir was built from 1900 to 1904. An examination of the dam's stability according to today's standards gave
reason to drive inspection galleries in the dam, to carry out in–situ tests in order to determine the characteristics of dam and underlying rock and to install an extensive measuring programme. Based on the test and monitoring results, a three–dimensional model was elaborated and
calibrated, which made it possible to proof the dam's stability under consideration of the three–dimensional load–carrying action of the dam.<\div>

۸Numerical Pile Driving Analysis for Non–Uniform Piles
نویسنده(ها): ،
اطلاعات انتشار: هفتمین همایش بین المللی سواحل، بنادر و سازه های دریایی، سال
تعداد صفحات: ۹
This paper focuses on the effect of pile shape in the penetration of pile and magnitude of stress in pile body. For this purpose, concrete tapered piles of the same volume and length is considered. All piles have conic shape with different slopes along the shaft. In all analyses, the hammer impact is modeled using a single function which obtains from current literatures. The subsoil is assumed as normally consolidated clay. The soil is assumed to be saturated and undrained. Linear elastic behavior is assumed for the pile whereas the Mohr–Coloumb failure criterion is considered for clay. Interface elements are used to allow the slip between the pile and the soil. To ensure the correctness of the constructed numerical pile driving models, the results obtained from this proposed model is compared with numerical data obtained from an available sophisticated analysis. Parametric studies have been carried out to determine the influence of contributing factors such as tapered angle and soil stratification on pile driving phenomenon. The effect of taper angle on permanent pile penetration and driving stresses will be presented.<\div>

۹Moment gradient loading Nonlinear behavior of castellated beams subjected to moment gradient loading
نویسنده(ها): ،
اطلاعات انتشار: سیزدهمین کنفرانس دانشجویان مهندسی عمران سراسر کشور، سال
تعداد صفحات: ۸
Since now, lots of experimental and numerical studies have been done to investigate nonlinear behavior of I–shaped steel beams but there is noclear understanding of inelastic behavior of castellated steel beams. This paper presents nonlinear behavior of such beams under moment
gradient loading and investigates the effect of beam length on overall response of this type of beams. For this purpose several refined 3–D finite element (FE) models subjected to moment gradient loading developed using solid elements, and their overall behavior is studied. The models have variable length and different bracing conditions. Analyzing the models under mentioned loading showed a reduction in ultimate rotation capacity for castellated beams respect to plane–webbed beams for longer beams. Also results of analyses showed that in bracing length near to plastic bracing space local instability of flanges occurs earlier than local buckling of web posts so due to full bracing of top and bottom flanges yields a greater ductility and moment capacity.<\div>

۱۰NONLINEAR BEHAVIOR OF CASTELLATED BEAMS SUBJECTED TO MOMENT GRADIENT LOADING
نویسنده(ها): ، ،
اطلاعات انتشار: پنجمین کنفرانس بین المللی زلزله شناسی و مهندسی زلزله، سال
تعداد صفحات: ۴
Since now, lots of experimental and numerical studies have been done to investigate nonlinear behavior of I–shaped steel beams but there is noclear understanding of inelastic behavior of castellated steel beams. This paper presents nonlinear behavior of such beams under moment gradient loading and investigates the effect of beam length on overall response of this type of beams. For this purpose several refined 3–D finite
element (FE) models subjected to moment gradient loading developed using solid elements, and their overall behavior is studied. The models have variable length and different bracing conditions. Analyzing the models under mentioned loading showed a reduction in ultimate rotation capacity for castellated beams respect to plane–webbed beams for longer beams. Also results of analyses showed that in bracing length near to plastic bracing space local instability of flanges occurs earlier than local buckling of web posts so due to full bracing of top and bottom flanges yields a greater ductility and moment capacity.<\div>

۱۱Electric Field Calculations in Rod–plane Gap Using Hyperbolic Approximation and Finite Element Method: a Comparison
نویسنده(ها): ،
اطلاعات انتشار: بیستمین کنفرانس بین المللی برق، سال
تعداد صفحات: ۷
In order to understand the behavior of arc inception and its transient propagation till complete breakdown across an insulator it is necessary to find out the maximum electric strength, max E , at the arc tip in an air gap and investigate the relationship of the dimensions of this particular geometry to max E . The most widely used model is a rod–plane one. Because of the strong non–uniformity of the field distribution it is mpossible to derive an equation by using conventional electromagnetic methods such as Laplace’s equation to find max E . In fact, there is only one well–known method, Roy’s equation, which is commonly used for a rod–plane system to calculate max E , i.e. by solving Laplace’s equation based on a parabolic approximation. In this paper, the validity of the results obtained by Roy’s equation is discussed and its results are compared with those obtained by finite element methods. It will also allow obtaining a better spectrum of the rod electrode system field istribution.<\div>

۱۲Finite Element Approach for Improving End Effect Model in Linear Induction Machines
نویسنده(ها): ،
اطلاعات انتشار: پانزدهیمن کنفرانس مهندسی برق ایران، سال
تعداد صفحات: ۶
methodfor modrfying special kind of end tlffect coefficient in equivalent circziit of Linear Induction Machine (LIM) is presented. Finite Element (FE) Model ofa LIM is analyzed to evaluate analytic studies and reszllts. The Finite Element model is constrzlcted by the windings voltages as input source. ,41so, relative velocity of primary and secondary is considered for calczrlations. Different jirnction of end effect in low–speed and high–speed LIMs is the basis for niodificution of LIIM eqzlivalen t circuit. It is shown that, the phenomenon of air–gap tht–zrst prohrction at synchronous speed in low–speed type of linear itiduction motor will be calculated by new equivalent circziif.<\div>

۱۳Influence of initial stresses on cleavage fracture of pressure vessel containing a part circumferential surface crack
نویسنده(ها): ،
اطلاعات انتشار: سیزدهمین کنفرانس سالانه مهندسی مکانیک، سال
تعداد صفحات: ۶
One critical issue in the integrity assessment of pressurised vessels to be addressed is characterising the influence of initial residual stresses (arising from fabrication processes especially around welds, where the appearance of cracks is also a likely event) on cleavage fracture. Using a specific crack configuration, this paper explores the stress state at crack tip area under similar loading conditions with and without the presence of initial stresses as well as their interaction and compares the stress fields in the context of stress based statistical modelling of cleavage fracture toughness. A recently developed local stress based approach to failure probability prediction for cleavage fracture of ferritic steels is used to predict toughness distributions. It is found that the presence of initial residual stresses dramatically change the final fracture conditions.<\div>

۱۴The Effects of Nonlinear Bearings, Gyroscopic moment and Dependency of Stiffness and Damping Coefficients on Viibration Analysis of rotor systems
نویسنده(ها): ، ،
اطلاعات انتشار: سیزدهمین کنفرانس سالانه مهندسی مکانیک، سال
تعداد صفحات: ۸
The nonlinearity effects of oil film in bearings, gyroscopic effect, dependency of stiffness and damping coefficients on frequency are considered in modeling and vibration analysis of rotor systems. Once a computerized program is written based on finite element method. In this method four element types including element of shaft, disk, bearing and suspension are applied. The responses of systems are obtained based on linear theory and then, the program applies nonlinear effects and nonlinear model is also analyzed. Then linear and nonlinear responses of the system are compared with each other and also with the results of other papers. Separately gyroscopic damping and its effect in vibration analysis is investigated. Ultimately conclusions are presented.<\div>

۱۵Modeling Considerations and Material Properties Evaluation in Analysis of Polymer Carbon– Nanotubes by using of square representative volume elements
نویسنده(ها): ، ،
اطلاعات انتشار: سال
تعداد صفحات: ۱۷
This paper presents a computational modeling approach for predicting the mechanical behavior of polymer carbon nanotubes (CNT). The CNTs interaction with matrix material was modeled using continuum mechanics theory and finite element approach. The effective mechanical properties of CNT based composites are then evaluated using a 3–D nanoscale model and a square representative volume element based on continuum mechanics and by using the FEM. Some numerical examples have carried out to investigate the stress distribution and to demonstrate the load carrying capacities of the CNT. Having known the stress and strain distribution, the material properties of the CNT can be easily calculated from standard theory of elasticity. In order to show the validity of the calculated results, they were compared with those obtained from the simple rule of mixture and with the earlier results obtained from using the cylindrical KVEs.<\div>

۱۶Dynamic Analysis of Non–uniform Cross–Section Beam under Moving Mass Using Finite Element Method
نویسنده(ها): ، ،
اطلاعات انتشار: چهاردهمین کنفرانس سالانه مهندسی مکانیک، سال
تعداد صفحات: ۹
The analysis of a variable cross–section beam subjected to a moving concentrated force and mass is investigated. Finite element method with cubic Hermitian interpolation functions is used to model the structure based on Euler–Bernoulli beam and Wilson–Ө direct integration method is implemented to solve time dependent equations. Effects of cross–section area variation, boundary conditions, and moving mass inertia on the deflection, natural frequencies and longitudinal stresses of beam are investigated. Results indicates using a beam of parabolically varying thickness with constant mass can decrease maximum deflection and stresses along the beam while increasing natural frequencies of the beam. Effect of moving mass inertia at high velocity of moving load is also investigated and findings indicate effect of inertia is significant at high velocity.<\div>

۱۷EFFECT OF PATCH CONNECTION METODES ON FRACTURE RESISTANCE OF CRACKED SHEETS
اطلاعات انتشار: چهاردهمین کنفرانس سالانه مهندسی مکانیک، سال
تعداد صفحات: ۸
Reliability enhancement of damaged structures through repairs is attracting considerable engineering challenge. Patch repairs to cracked metallic sheets have been accepted as a reliable and suitable technology and offer various advantages. From the available approaches, there are three more common types; adhesive bonded patch, riveted patch and edge welded one. Researchers have extensively investigated the first method, but the two last methods are more common in the industry. In this paper, the analyses of all common various patch connection methods have been performed and compared with each other using FE method. The results have been validated with an analytical method and existing approaches in literature. This investigation shows that adhesive bonded patch has the best performance.<\div>

۱۸FINITE ELEMENT MODELING OF CARBON NANO–TUBE BASED COMPOSITES
نویسنده(ها): ، ،
اطلاعات انتشار: سال
تعداد صفحات: ۸
This paper presents a computational modeling approach for predicting the mechanical behavior of polymer carbon nanotubes (CNT). The CNTs interaction with matrix material was modeled using continuum mechanics theory and finite element approach. Some numerical examples were carried out to investigate the stress distribution and to demonstrate the load carrying capacities of the CNT. Simulation results showed that the load carrying capacities of the CNTs in a matrix are significant, which are consistent with the observations in the experimental work reported in the literature. Effects of the caps at the ends of CNTs were also studied in detail<\div>

۱۹THE THREE–DIMENSIONAL FINITE ELEMENT ANALYSIS OF CONTACT AREA OF SYMMETRIC AND NON–SYMMETRIC LAMINATED COMPOSITE PINNED–JOINTS
نویسنده(ها): ، ،
اطلاعات انتشار: سال
تعداد صفحات: ۶
This paper presents analyses for computing and evaluating the behavior of the laminated composite plate at the contact area in single lap, mechanically fastened joints. The analyses involve three dimensional finite element models performed by ABAQUS 6.4– PR11 code to evaluate the stress distribution in contact surface, separation angle, the magnitude and location of maximum radial stress. Results are determined for
isotropic model and composite laminates with different layer configurations and attempts are made to validate the models with previous works. For cross ply and angle ply configurations only symmetric stacking sequences are used while for quasi–isotropic laminate both symmetric and non–symmetric models are generated. The variations of separation angles through the thickness are investigated and effects of different layer
configurations are discussed. In cross–ply laminate symmetric separation about bearing plane could be found while in quasi–isotropic and angle–ply laminates non–symmetric separation occurs. Also, the separation angle is less than 90° in symmetric laminates and greater than 90° in some plies of non–symmetric laminates.<\div>

۲۰COMPUTER SIMULATION OF A BONE REMODELING MODEL INCLUDING CELLULAR ACCOMMODATION EFFECT
نویسنده(ها): ، ، ،
اطلاعات انتشار: پانزدهمین کنفرانس سالانه مهندسی مکانیک، سال
تعداد صفحات: ۵
A regulatory mechanism for mechanical adaptation of trabecular bone proposed by Huiskes and collegues [1] is implemented and studied in a MATLAB code. In addition to simulating the Osteocyte mechanosensory role and separation of Osteoclast and Osteoblast activity as proposed in [1], we improved this theory by including effect of Turner’s cellular accommodation [2]. We obtained trabecular–like structures for different loading conditions. The model was able to predict stress shielding and also showed qualities of global mechanical optimality.<\div>

۲۱COUPLED ACOUSTIC STRUCTURE VIBRATION ANALYSIS OF A THIN CLAMPED FREE LAMINATED COMPOSITE CYLINDRICAL STORAGE TANK PARTIALLY FILLED WITH WATER
نویسنده(ها): ،
اطلاعات انتشار: پانزدهمین کنفرانس سالانه مهندسی مکانیک، سال
تعداد صفحات: ۶
Storage tanks and cylindrical shells containing fluid are widely used as structural components in various applications. The aim of this paper is computing and evaluating the vibration behavior of a partially fluidfilled laminated composite shell. The analyses involve three dimensional finite element models performed by ABAQUS 6.6–1 code to evaluate the natural frequencies and modes of vibration of the shell and investigate the
effects of contained fluid height on the natural frequencies and modes of vibration. Results are determined for isotropic shell first and attempts are
made to validate the model with previous experiments. Then, the problem is solved for partially fluid–filled laminated composite shell and natural frequencies and modes of vibration are extracted. The contained fluid affects the vibration behavior of the whole problem. It is shown that the fluid effect on the shell is significant and ignorance of the fluid effect will lead to large errors in vibration analysis of fluid–filled shells.<\div>

۲۲EFFECT OF FLUID SOLID INTERACTION IN AXISYMMETRIC CAROTID ARTERY STENOSIS
نویسنده(ها): ، ،
اطلاعات انتشار: پانزدهمین کنفرانس سالانه مهندسی مکانیک، سال
تعداد صفحات: ۷
High blood pressure, severe stenosis and stiffened plaque make fluid–structure interaction (FSI) plays an intensive role in simulating blood flow in stenotic arteries. This work is concerned with the study of plaque severity and stiffness effects on arterial hemodynamic parameters in models of atherosclerotic carotid arteries using fluid–solid interaction (FSI). The parameters include blood flows, pressure drop, wall shear stress, wall stress concentration and deformation. The investigation is done with the aid of finite element method for solving the structure and TDMA and SIMPLE methods in CFD for the fluid domain solution using ANSYS software. To overcome the software inconsistency in FSI mode, a new mathematical program is designed using incremental boundary iteration method. A linear elasticity approach is implemented in modeling the arterial wall and Navier– Stokes equations govern the fluid domain. Minimum structural deformation, high pressure drop and high shear stress at the throat of the stenosis, flow recirculation and low shear stress just distal to the stenoses were observed under physiological conditions.
Critical condition is determined due to severity variations which may lead to thrombus formation and possible plaque rupture. To illustrate the accuracy of proposed method, the results are compared with published experimental and numerical.<\div>

۲۳Numerical Solution of Film–mode Boiling on Straight Pin Fin by Finite element method
نویسنده(ها): ،
اطلاعات انتشار: نهمین کنگره ملی مهندسی شیمی ایران، سال
تعداد صفحات: ۱۲
In this study, Film mode boiling on a straight pin is theoretically investigated. Axial steady state temperature distributions and base heat flow along the fin under film mode are numerically evaluated by finite element method. The aim of this work is to study the application of finite element method for solving partial differential equation of steady state, one dimensional heat transfer in film mode boiling. However importance and great application of finite element method are declared when we investigate the comparison of the finite element and exact solution as will be shown in
follow.<\div>

۲۴Optimization of extruded preform dimensions for a T–shape hydroforming part based on response surface and finite element method
نویسنده(ها): ، ، ،
اطلاعات انتشار: شانزدهمین کنفرانس سالانه مهندسی مکانیک، سال
تعداد صفحات: ۷
Tube hydroforming has been widely applied to produce seamless joints in oil and gas industry. The finite element analysis is used as an effective tool for optimization of hydroforming process. In this paper, a T–shape tube hydroforming process is simulated using the finite element method. The simulation was verified by experiments performed on T–shape tube hydroforming. The internal pressure, material model and other important simulation parameters was obtained from experiments. By using design of experiment methodology number of experiments with different
thickness and length setting of initial tube were suggested. In order to avoid costly experiments, the finite element simulation was used. At last response surface methodology (RSM) were adopted to plot the results of the analysis. Since protrusion height, thickness reduction at protrusion region and thickness increase in central region of the product were important design parameters to control, the initial tube thickness and length was so optimized that the best possible product was achieved. Finally, a model using optimized initial tube was analyzed. The predicted amount of parameters was compared to those achieved from the analysis.The comparison showed a good agreement between the predicted and analyzed results.<\div>

۲۵Prediction of wall thickness in deep drawing process with neural network
نویسنده(ها): ، ،
اطلاعات انتشار: شانزدهمین کنفرانس سالانه مهندسی مکانیک، سال
تعداد صفحات: ۵
In this paper, the modeling of deep–drawing process using neural networks is established. The relationships between process parameters (punch radius, matrix radius, blank holder force) and part quality (wall thickness) are created, based on a neural network. Finite element analyses are conducted for combination of process parameters designed using statistical full factorial experimental design. A predictive model for wall thickness is created using Levenberg–Marquardt (LM) artificial neural network exploiting finite element analysis results. The results obtained are found to correlate well with experimental data.<\div>
نمایش نتایج ۱ تا ۲۵ از میان ۳۴۷ نتیجه