جستجوی مقالات مرتبط با کلیدواژه "fem" در نشریات گروه "فنی و مهندسی"

This paper outlines the conceptual and numerical design process of a comminution equipment centered on particle breakdown through impact. The process is divided into four stages, starting with the generation of device concepts achieved by developing a needs matrix for an optimal machine. Subsequently, in the second stage, various equipment shape proposals were introduced and tested, with the selection of an optimal proposal determined through performance comparisons. For comparison purposes, simulations utilizing the discrete element method (DEM) were conducted, considering analyses of accumulated power from collisions and particle breakage. Once the optimized prototype was identified, a breakage simulation was conducted to measure the device's reduction ratio. In the third stage, the machine elements of the device were calculated. Finally, in the fourth stage, a series of simulations utilizing the finite element method (FEM) were carried out to perform structural and modal analyses of the final design. The evaluated variables identified in the simulations played a crucial role in optimizing the design, ultimately resulting in a device with a reduction ratio of 1:19.8 for limestone.

This study presents a new exponential higher-order shear deformation theory (NEHSDT) to examine the flexural analysis of multi-layered laminated composite plates. The novel parabolic shear deformation function is developed to analyze the bending response of laminated plates. A new shear deformation theory eliminates the need for shear correction factors. The present theory gives an exact parabolic distribution of transverse shear stress over the thickness and fulfills the traction-free boundary conditions on the outer surfaces of multi-layered laminated plates. The governing equations are solved using the finite element method. In this finite element method, a nine-nodded isoperimetric element with seven degrees of freedom per node is formed especially for this purpose. Illustrative examples are presented to demonstrate the predictive capability of the proposed finite element method. The presented numerical results are compared with the existing results to illustrate the correctness and robustness of the finite element method. The proposed analysis is accurate, converges rapidly, and is valid for thin and thick laminated plates based on comparisons with earlier higher-order shear deformation theories. In addition, the present results may be taken as the benchmark for further studies.

The forging process is a typical process to manufacture industrial parts that are subjected to fatigue stresses. The forged parts have equiaxial grains, and crack propagation occurs at a lower rate.  A part's mechanical properties stem from its manufacturing process and initial materials. One of the applications of the forging process is manufacturing different kinds of metallic prostheses such as hip prostheses, which are very privileged in medical and rehabilitating issues. Hip prostheses undergo various types of stress, i.e., fatigue stress, indicating its significance in manufacturing. Cold forging is a promising method to produce high-strength parts with high fatigue life. Titanium alloys are widely used in prostheses due to their corrosion resistance. This study investigates the feasibility of manufacturing hip prostheses via cold forging. To analyze the behavior of materials during the forging process, the FEM simulation by ABAQUS software is applied. The press force is a significant factor in achieving the final geometry in which raw material fills the forging die within one stroke. In addition, the strength of the die is noticeable during the forging process.

Sheet metal forming is one of the main processes of forming thin-walled plates to produce the semi-final and final parts with high precision. In the present work, a complete investigation of the forming operation of the jack bracket of the Kia Rio car has been conducted with the help of the Design of Experiment (DOE) method, numerical simulations, and experimental investigations. First, the Finite Element (FE) method performed a numerical simulation of the process, and the results were compared with experimental results. Then, 13 proposed simulations were performed through the Box-Behnken experimental design method to study the effect of process parameters. The Friction Coefficient (FC), the press speed, and the Blank Holder Force (BHF) were chosen as input parameters. The maximum strain, the maximum stress of the part and the maximum punch force were considered output parameters. The results indicated that punch speed had the most significant effect on the plastic strain, with a contribution of 61.63%, and also FC had the most impact on the maximum force, with a contribution of 58.69%. Moreover, the role of BHF in the mentioned outputs was not considerable, but it was significant (31.47%) in the investigation of stresses.

Temperature prediction is essential for assessing the state of stresses, strains, and material flow during friction stir welding (FSW). In this context, the thermal and mechanical behavior of the AA6063-T5 aluminum alloy was simulated in FSW. This research utilized the Finite Element Method (FEM) for thermal and mechanical simulations, employing Abaqus/Explicit software. The first simulation focused on the thermal model, implemented through coding in FORTRAN using the Schmidt-Hotel reference model, which investigates the temperature distribution of the alloy. The second simulation was mechanical in nature; it utilized the output results from the thermal simulation to examine the stresses resulting from the FSW process. The samples were made of the same material and were butt-jointed for the operation. A tool speed of 60 mm/min, a force of 4000 newtons, and a coefficient of friction of 0.4 were applied during this process. The parameters for thermal conductivity, specific heat, coefficient of expansion, and Young's modulus were defined as temperature-dependent. The results indicated that the temperature distribution diagram at a specific point along the welding path closely matched practical examples of the FSW process. The temperature distribution contours at the beginning, middle, and end of the welding path, as well as the temperature distribution across the cross-sectional surface of the weld in the middle of the piece, were consistent with the samples. Additionally, the diagram and contour of the longitudinal residual stress in the workpiece aligned well with the completed samples.

Pipeline systems under thermal loads are frequently used in different industries, such as the power plants and petrochemicals. Unlike the analytical method of elastic center, which is capable to analyze only one branch of pipeline with pipe members parallel to the coordinate system, the method of stiffness removes these limitations. In this article the stiffness method is introduced for the analysis of pipeline systems. Based on this method, the piping system may include any number of piping braches. The straight pipe elements in the branch may have any general orientation and the bend elements may have any arbitrary angle. The computer program designed based on this method may compute the nodal displacements at the ends of the straight or bend elements and present three components for loads and three components for moments. Once the free-body diagram of each piping elements with nodal forces and moments are drawn, then the engineering codes are employed to design the piping system for safe operation.

In this paper, we employ the finite element method based on non-uniform rational B-splines function approximation to solve the nonlinear Brinkman-Forcheimer-Darcy equation in a simply connected and bounded Lipschitz domain Ω. We provide both theoretical and numerical studies of the Dirichlet boundary problem. Utilizing a stream function formulation, we demonstrate the well-posedness of the weak form. Furthermore, we approximate the velocity and pressure fields by linearizing the nonlinear terms, resulting in an algebraic system. This Non-uniform rational B-splines method is more effective in terms of the exact representation of the geometry and the good approximation of the solution compared to the virtual element method. To validate the effectiveness of the non-uniform rational B-splines Finite Element Method, we conduct numerical simulations of fluid flow in porous media.

Due to the critical nature of seismic risk in metro tunnels, the seismic response of underground tunnels is a highly delicate topic. The seismic response of a sub-surface structure depends more on the properties of the surrounding ground and the induced earth deformation during an earthquake than on the structure's inertial properties. This paper examines the seismic response of a typical section of the underground tunnel of Delhi Metro Rail Corporation (DMRC) between Rajiv Square and Patel Square in New Delhi's Connaught Place. Three-dimensional elasto-plastic analysis of Delhi metro underground tunnels under the seismic loading has been performed by finite element method using the Plaxis 3D software. Additionally, the influence of various boundary conditions on the dynamic response of metro tunnels has been examined. A comparison of the three-dimensional analysis with the two-dimensional plane-strain analysis has also been made. Horizontal displacements were experienced maximum compared to the longitudinal and vertical displacements in the soil-tunnel system. In dynamic analysis, the absorbent boundary is much more effective in controlling the displacements and the induced acceleration than the elementary boundary or the free-field boundary.

Among all methods for ground improvement, stone columns have become more popular recently, owing to their simple construction and plentiful availability of raw materials. However, in relatively softer soils, ordinary stone columns (OSCs) experience significant bulging owing to the minimal confinement offered by the surrounding soil. This necessitates the introduction of reinforcements in the stone column, to enhance their strength in such circumstances. The subject of this investigation was the assessment of the behavior of horizontally reinforced stone columns (HRSCs), introduced in layered soil, under the raft foundation. The soil material included was idealised using an isotropic linearly elastic fully plastic model with a Mohr-Coulomb failure criterion. There are a total of six separate factors required by the Mohr-Coulomb criterion. These include cohesion (c), the soil's dry unit weight (γd), the Poisson ratio (μ), the angle of internal friction (φ), the angle of dilatancy (ψ), and the Young's modulus of elasticity (E). At the very beginning, the load-settlement response of unreinforced soil was evaluated followed by a comparative study between square and triangular arrangements of stone columns, at different spacings, under the raft, to arrive at the configuration that encounters minimal settlements and lateral deformations. Furthermore, circular discs of suitable geogrid material were introduced along the length of the stone column. The elastic behaviour of geogrids is governed by two properties: tensile modulus and yield strength. The load-settlement behavior and lateral deformations of the resulting reinforced stone columns, with OSCs were compared. Furthermore, the spacing between the circular discs of geogrids was kept at D/2, D, 2D, and 3D, where D is the diameter of the stone column. According to the findings of an investigation conducted using FEM software, the performance of a granular pile group that is laid out in the shape of a triangle encounters much less lateral deformation and settlement than the square arrangement. The results also show that the performance of HRSCs was way better than those of OSCs, under the same in-situ soil conditions.

This study aimed to investigate the influence of rotational and traverse speeds on the friction stir welding (FSW) of aerospace-grade aluminum alloys. To achieve this, a thermo-mechanically coupled 3D finite element analysis (FEM) was employed to analyze the impact of these speeds on temperature and strain. Additionally, tensile tests were conducted on welded joints fabricated using varying tool rotational and traverse speeds to examine the effects of welding speed on the tensile properties of the specimens. The results revealed that high welding speeds had a detrimental effect on the mechanical properties of the weld samples. Samples produced using an optimal rotational speed of 1200 rpm and a traverse speed of 40 mm exhibited a tensile strength of 346 MPa, which accounts for approximately 64% of the strength seen in the base material.

Conical machines with a unique conical rotor and stator design have several advantages over electrical machines with traditional designs. The conical shape allows for greater torque and efficiency, which makes these machines ideal for use in heavy machinery and industrial equipment. Besides, their compactness in comparison with traditional machines makes them easier to integrate into manufacturing processes.  Furthermore, since magnetic gears (MGs) have provided a solution to overcoming mechanical challenges and disadvantages of mechanical gears, their development has become a hot research topic in the last few years. Due to asymmetric geometry and special flux paths, the analysis should be modeled in 3-D finite element tools. In this paper, a hybrid structure, named conical MG, is introduced in order to benefit simultaneously from the advantages of radial flux and axial flux structures of MG. This topology can provide more contact surface of permanent magnets (PMs) and, thus, increase the torque density, with a proper design and the optimization of dimensions. The proper shaping of the PMs and providing the correct structure of MG can lead to a high impact on the output characteristics of the system. This design improves the transmission torque by forming the magnetic fields in air gaps. To compare the proposed topology, the optimal design of the model is compared with the conventional radial flux structure using the genetic algorithm and 3-D finite element method to obtain maximum torque density. The results are compared and the superiority of the proposed model is proved.

Nowadays, the use of bimetallic laminates with special capabilities and features is increasing and has experienced high growth. These properties include high mechanical properties, corrosion resistance, light weight, resistance to noted good abrasion and thermal stability. In the midst of the technologies of multilayer composite materials Accumulative Press Bonding (APB) is one of the most common techniques for the production of multilayer composites. One of the most important aims for this choice is the press pressure, which can create a strong and suitable mechanical connection between Produced metal layer components. In this study, the Accumulative Press Bonding method has been used to produce aluminum and copper composites and the process modeling has been done by ABAQUS finite element analysis software. In this paper, the effect of Press parameters such as strain and number of layers on the distribution stress of forming this type of composites has been investigated. Shear stress among the layers reached to about 4MPa for samples with eight layers which is a good condition to generation a successful bonding.  With increasing thickness, the stress applied on the layers has also increased. Maximum stress also increases significantly. As the thickness decreases, the interlayer shear stresses also increase. With increasing percentage of thickness decrease, the amount of sinking of the layers in each other has greater than before, which has led to the crushing of copper layers along the entire length of the sample. During the process, as the number of passes increases, the volume of virgin material in the direction of the press rises, which leads to increased compaction and better adhesion of the layers to each other.

In this article, free and forced vibration analyses of 3D printed FG sandwich beam based on higher order beam theory is investigated. The core and face sheets of sandwich beam are integrally fabricated by 3D printer. Therefore, ignoring the delamination between face sheets and core is a correct assumption. Three different cells are considered for the core including Re- entrant auxetic cell, anti-tetrachiral auxetic cell and conventional honeycomb cell. These cells are arranged along the thickness of structure based on cell thickness in four various patterns. The effective mechanical properties of cells are estimated by analytical relations. Finite element methods and Lagrange equations are employed for obtaining the effective stiffness and mass matrices of the sandwich beam. Finally, the influences of various parameters including various types of cells, various patterns of cell along the thickness of structure, thickness coefficient, the geometry of cells such as the interior angle and dimensions of cells on natural frequencies and transient deflection of structure have been studied. The results denote that the arrangement of cells along the thickness plays an important role on the vibration response of structure. On the other hand, for uniform thickness distribution of cells, Re –entrant auxetic cell has higher natural frequencies than other cells while in FG arrangements of cells, anti-tetrachiral cell with pattern A has higher natural frequencies than Re-entrant auxetic cell.

In this article, shear buckling analysis of functionally graded porous annular sector plate reinforced with graphene nanoplatelets (GPLs) are investigated for the first time. The plate is consisting of a layered model with uniform or non-uniform dispersion of graphene platelets in a metallic matrix including open-cell interior pores. The extended rule of mixture and the modified Halpin-Tsai models and are employed to obtain the effective mechanical properties of the porous nanocomposite plate. Three different porosity distributions in conjunction with five patterns for dispersion of GPL nanofiller are considered through the thickness of plate. Governing equations derived according to the principle of minimum total potential energy based on 3D elasticity theory and generalized geometric stiffness concept. Finally, finite element method is applied for solving the governing equations of structure. The influence of different parameters including various porosity distribution, porosity coefficient, patterns of GPL dispersion, weight fraction of GPL nanofiller, boundary conditions and sector angles on shear buckling loads of the annular sector plate has been surveyed.