Percorrer por autor "Madureira, M.L.R."
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- A finite element formulation for piping structures based on thin shell displacements theoryPublication . Fonseca, E.M.M.; Melo, F.J.M.Q. de; Madureira, M.L.R.
- A multi-nodal ring finite element for analysis of pipe deflectionPublication . Fonseca, E.M.M.; Melo, F.J.M.Q. de; Madureira, M.L.R.The main objective of this work is to present a numerical formulation to solve the problem of the deformation analysis ot thin-walled circular cylindrical pipes under concentred loads. The solutions is based on a displacement field entirely defined from a set of trigonometic functiobns where the amplitudes are assigned as a nodal paramenters in a multi-nodal finite element. With this formulation it is possible to provide an easy alternative tool when compared with a complex finite shell or solid element modelling for the same type of applications. The present work permits to examine the defection of pipe rings subjected to lateral (transverse) static loading conditions. Several case studies presented have been compared and discussed with numericalç analysisresults obtained with a shell element from Ansys programme.
- Out of plane bending in curved pipes.Publication . Madureira, M.L.R.; Fonseca, E.M.M.; Melo, F.J.M.Q. dePiping structures have large application in power generation and chemical plants. Given their complexity and construction safety standards, the development of accurate numerical methods has been analyzed by several authors [1,2,3] with trigonometric solutions. Also pipe finite elements, with a considerable amount and complexity of work, has been used to define accurate models for numerical approach of the stress field [4,5,6,7]. In this work both analytical and numerical approaches are presented. A mathematical analytical solution is derived using a mixed formulation where unknown functions are combined with Fourier series [8]. Using a minimization criterion for the total energy involved in the process a system of second order ordinary differential equations is obtained and then solved using the MAPLE® mathematical package. Numerical simulation was performed using the Finite Element Method for the same steel pipe under out-of-plane bending and results are compared showing that a good agreement can be reached with only a few terms in the Fourier expansion. In this example four terms were considered.
- The deformation of cylindrical shells subjected to radial loadsPublication . Madureira, M.L.R.; Fonseca, E.M.M.; Melo, F.J.M.Q. deThe exact bending solutions of moderately thick rectangular plates with two opposite sides simply into Hamilton cononical equations. Then the whole state variables are separeted. According to the method of eigenfunction expansion in the symplectic geometry, the exact bending solutions of the plates are used and there is no need to select the deformation functions arbitrary, the approach utilized is completely reasonable.
- The deformation of cylindrical shells subjected to radial loadsPublication . Madureira, M.L.R.; Fonseca, E.M.M.; Melo, F.J.M.Q. deCylindrical shells have a simple geometry and application in pressure vessels and piping engineering. The development of calculation algorithms in structural project is impelled by a constant challenge in the search of more accurate and fast design tools in engineering. The objective of this work is to contribute with a simple and reliable numerical tool for the stress analysis of cylindrical vessels subjected to generalized forces. A hybrid formulation in the definition of forces and displacements is proposed for cylindrical shells subjected to radial loads. Variational techniques coupled with functional analysis are used to obtain an optimized solution for the shell displacement and further stress field evaluation. As it is not possible to obtain exact solutions for the displacements or deformation field whenever the external loads are either concentrate or locally distributed, the solution here proposed deals with the combination of unknown analytic functions combined with Fourier expansions, where the former depend on the axial shell coordinate and the trigonometric terms are dependent upon the cylinder circumferential polar angle. These functions are expanded in Fourier series where displacement amplitudes are combined with trigonometric terms. The result is a system of ordinary differential equations where the solution is analytic after evaluation of eigenvalues and eigenvectors. The boundary conditions are then used to reach the final solution. As an example a large cylindrical shell subjected to pinching loads is considered. The results for the radial displacement and section ovalization are analyzed where the solution was obtained with three terms (nq=6) for the accuracy is acceptable in this case. The transverse displacement presents important dependence on the shell thickness vs radius, as the shell can be a thin-walled one (this case is included in the presented example) up to a moderately thick one, where the surface displacement ranges until the extreme edges, which is not the case analyzed. The proposed method leads to accurate results with a relatively low complexity input data. For conclusions of this work it is remarked that the definitions of the load system and boundary conditions are easily processed as the method has pre-defined possibilities for each load case or edge boundary conditions. An analytic solution is obtained and a low number of terms in the Fourier series show good accuracy. A comparison with finite element methods is presented.