23 research outputs found
On Lagerstrom’s Model of Slow Incompressible Viscous Flow
Get PDFThe model discussed is a nonlinear boundary value problem which contains a parameter that models the Reynolds number. The matched asymptotic expansions, an inner “Stokes” expansion valid near the inner boundary and an outer “Oseen” expansion valid away from it, that describe the solutions of the model problem for small are extended. Numerical calculations show that these matched expansions have only a small range of usefulness, with the addition of further terms generally causing a worse, rather than better, approximation at moderate values of . Far better results are achieved when a single expansion, the outer expansion, is used throughout. The additional terms that have been calculated then consistently give improved approximations for all . It is also rigorously proved that an iterative method of solution of the model equation based on the outer “Oseen” approximation, converges for all to a unique solution.\ud
The results presented here for Lagerstrom’s model suggest that iterative improvement of the Oseen expansion may be an effective method of approximation of viscous flows at moderate Reynolds number
A New Numerical Procedure for Determination of Effective Elastic Constants in Unidirectional Composite Plates
Get PDFIn this paper a composite plate with similar unidirectional fibers is considered. Assuming orthotropic structure, theory of elasticity is used for investigating the stress concentration. Also, complex variable functions are utilized for solving the plane stress problems. Then the effective characteristics of this plate are studied numerically by using ANSYS software. In this research a volume element of fibers in square array is considered. In order to investigate the numerical finite element modeling, the modeling of a quarter unit cell is considered. For determining the elasticity coefficients, stress analysis is performed for considered volume with noting to boundary conditions. Effective elasticity and mechanical properties of composite which polymer epoxy is considered as its matrix, are determined theoretically and also by the proposed method in this paper with finite element method. Finally, the variations of mechanical properties with respect to fiber-volume fraction are studied
An Investigation on Tensile Properties of Glass Fiber/Aluminium Laminates
No full textThe idea of combining low weight and good mechanical properties has led to efforts to develop a new light fiber/metal laminate (FML) in the last decade. FMLs are hybrid composites consisting of alternating thin layers of metal sheets and fiber-reinforced epoxy prepregs. In this study, the effect of fiber orientation on tensile properties of this material is investigated both analytically and experimentally. An analytical constitutive model based on classical lamination theory by using Kirchhoff-Love assumption, which incorporates the elastic-plastic behavior of the aluminium alloy was applied. Test results show that fiber sheet, with zero angle in laminates, improve the tensile strength. The composite layers with different fiber orientation change specimens' mode of fracture. Good agreement is obtained between the model predictions and experimental results
DETERMINING OF FORMING LIMIT STRESS DIAGRAM FOR AL5083-H321 ALLOY BY CRUCIFORM SPECIMEN
No full textThis paper deals with experimental and numerical studies of fracture behavior of Al. 5083-H321 alloy, under uniaxial and biaxial tensile loadings. In order to experimentally investigate biaxial fracture behavior, cruciform specimens were prepared using electrochemical method, based on Lionel proposed model. The specimens were gridded by electrochemical etching method. A dependent biaxial tension mechanism was also designed and fabricated with relatively high precision machining methods. Installing the mechanism on an INSTRON-1343uniaxial machine, the experimental biaxial tests were performed at ambient temperature and strain rate of 0.0003 . Different aspects of the facture behavior, which may be of more interest to study, include initiation and development of fracture pattern, fracture path on the specimen section, and the force diagram for each of the arms. ABAQUS commercial software was utilized to simulate the biaxial tension test. Damage model was incorporated into the FE simulations to enable the FE model to capture the fracture occurrence in the cruciform specimen. Displacement loading with different ratios was applied to the specimen arms in the FE model to study the effect of loading ratio on the fracture of the material. Experimental and numerical results for location of crack initiation, path of crack growth and also the arms force diagram were compared and a good correlation was observed between. The experimental results reveal that the fracture grows along the corner-to-corner diagonal line, in the test section zone of the specimen. Simulation results show that minimal strains occur in the test section zone, near the arms. Experimentally measuring the fracture stress is one of the great challenges, and hence, numerical simulation would be very useful in this regard. Maximum of stress gradient in the simulation results is observed along the corner-to-corner direction, in the test section zone. Based on the simulation results, some fracture biaxial points were obtained in the first quarter of the biaxial stress plane subspace. These fracture stress point can be used to determine the material fracture loci in the first quarter of the biaxial stress plane subspace
Sensitivity characteristics of electrostatic sensor using finite element modeling
No full textElectrostatic sensor detects the electric charge carried by dry particle in a pneumatic conveyor. Sensitivity characteristics of the Electrostatic sensor play an important role to design a flow measurement system. In this study, the sensitivity features of the ring shape electrodes are simulated to find the effect of electrode geometry on sensor sensitivity. Ansys Maxwell 14.0 is utilized as an electric field simulator to measure the amount of induced electrical charge from a particle to the sensor electrode in a 3D environment using finite-element analysis. The results precisely show the sensitivity characteristics between electrodes with different thickness, axial length and diameter
Electric charge tomography imaging using finite-element method and pro-rata distribution
No full textTomography is a cross-sectional distribution of materials in some region of interest such as cross-section of a pipeline. The technology is widely applied in order to optimize the production efficiencies in process industries that uses pipeline for conveyance. In this paper the elements' and coordinates interpolation techniques of the finite-element method; Cartesian coordinate system, Gauss and Coulombs electrostatic laws were applied to model the system equation with sixteen electrodynamic sensors. However, Matlab program was designed to structurally mesh cross-section of the conveying pipeline into triangular elements which serves as the image pixels. From the modeled system equation, charge spatial sensitivity map for the problem domain was made. The sensitivity matrix obtained, was used to reconstruct the tomography image of the moving particles using Filtered Back Projection and Pro-rata distribution concepts. The combination of the filtered back projection and Pro-rata distribution concepts introduced in the paper, gave a good tomographic image that shows the concentration profile of moving particles through pipeline
A low-profile flexural displacement-converter mechanism for piezoelectric stack actuators
No full textA Heuristic Algorithm Based on Line-up Competition and Generalized Pattern Search for Solving Integer and Mixed Integer Non-linear Optimization Problems
No full textAbstract The global optimization of integer and mixed integer non-linear problems has a lot of applications in engineering. In this paper a heuristic algorithm is developed using line-up competition and generalized pattern search to solve integer and mixed integer non-linear optimization problems subjected to various linear or nonlinear constraints. Due to its ability to find more than one local or global optimal points, the proposed algorithm is more beneficial for multi-modal problems. The performance of this algorithm is demonstrated through several non-convex integer and mixed integer optimization problems exhibiting good agreement with those reported in the literature. In addition, the convergence time is compared with LCAs' one demonstrating the efficiency and speed of the algorithm. Meanwhile, the constraints are satisfied after passing only a few iterations
