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2008, Arxiv preprint arXiv:0801.2085
In this paper we study some optimization problems for nonlinear elastic membranes. More precisely, we consider the problem of optimizing the cost functional J (u) = R ∂Ω f (x)u dH N−1 over some admissible class of loads f where u is the (unique) solution to the problem −∆pu + |u| p−2 u = 0 in Ω with |∇u| p−2 uν = f on ∂Ω.
Applied Mathematics and Optimization, 2009
In this paper we study some optimization problems for nonlinear elastic membranes. More precisely, we consider the problem of optimizing the cost functional J (u) = R ∂Ω f (x)u dH N −1 over some admissible class of loads f where u is the (unique) solution to the problem −∆ p u + |u| p−2 u = 0 in Ω with |∇u| p−2 u ν = f on ∂Ω.
2006
This paper concerns an optimization problem related to the Poisson equation for the p-Laplace operator, subject to homogeneous Dirichlet boundary conditions. Physically the Poisson equation models, for example, the deformation of a nonlinear elastic membrane which is fixed along the boundary, under load. A particular situation where the load is represented by a characteristic function is investigated.
UDC 519.6
Contemporary Mathematics, 2000
In this paper, continuing our earlier article [CGIKO], we study qualitative properties of solutions of a certain eigenvalue optimization problem. Especially we focus on the study of the free boundary of our optimal solutions on general domains.
Computers & Structures, 2004
In this work, a numerical approach is presented for solving problems of finitely deformed membrane structures made of compressible hyperelastic material and subjected to external pressure loadings. Instead of following the usual finite element procedure that requires computing the material tangent stiffness and the geometric stiffness, here we solve the membrane structures by directly minimizing the total potential energy, which proves to be an attractive alternative for inflatable structures.
Journal of Elasticity, 2009
For very thin shell-like structures it is common to ignore bending effects and model the structure using simple membrane theory. However, since the thickness of the membrane is not modeled explicitly in simple membrane theory it is not possible to use the three-dimensional strain energy function directly. Approximations must be introduced like the assumptions of: no thickness changes, generalized plane stress or incompressibility. In contrast, the theory of a Cosserat generalized membrane uses the three-dimensional strain energy function directly, it includes both thickness changes and shear deformation and it allows contact conditions to be formulated on the interface of the membrane with another body instead of on the middle surface of the membrane. A specific nonlinear contact problem is used to study these effects and comparison is made with solutions of a hierarchy of theories which include different levels of deformation through the thickness of the membrane and different formulations of the contact conditions. The results indicate that within the context of a simple membrane the assumption of generalized plane stress is best for this problem and that a generalized contact condition extends the range validity of the simple membrane solution to thicker membranes.
International Series of Numerical Mathematics, 2015
We consider a classical shape optimization problem for the eigenvalues of elliptic operators with homogeneous boundary conditions on domains in the N-dimensional Euclidean space. We survey recent results concerning the analytic dependence of the elementary symmetric functions of the eigenvalues upon domain perturbation and the role of balls as critical points of such functions subject to volume constraint. Our discussion concerns Dirichlet and buckling-type problems for polyharmonic operators, the Neumann and the intermediate problems for the biharmonic operator, the Lamé and the Reissner-Mindlin systems.
Computational Mechanics, 2005
A class of mixed finite elements based on the Hu-Washizu functional is introduced as a strategy to reduce the spurious stress phenomena encountered with standard or displacement-based formulations for geometrically exact membranes. Selected examples compare the performance of this class of elements with that of the standard formulation and demonstrate that reduction of spurious stresses is obtained and that the stresses are more accurate than those optimally sampled in the standard formulation.
Journal of Mathematical Analysis and Applications, 2005
In this paper, we study a nonlocal variational inequality. The nonlocality appears both in the coefficients of the operator, through an integral representing some elastic energy, and in the constraints, which are of the type called soft in the literature. 2004 Elsevier Inc. All rights reserved.
In this work, a numerical approach is presented for solving problems of finitely deformed membrane structures made of compressible hyperelastic material and subjected to external pressure loadings. Instead of following the usual finite element procedure that requires computing the material tangent stiffness and the geometric stiffness, here we solve the membrane structures by directly minimizing the total potential energy, which proves to be an attractive alternative for inflatable structures. The numerical computations are performed over two simple geometries-the circular and the rectangular membranes-and over a more complex structure-a parabolic antenna-using the Saint-Venant Kirchhoff and neo-Hookean models. Whenever available, analytical or semi-analytic solutions are used to validate the finite element results.
Nonlinear Analysis: Theory, Methods & Applications, 2000
Optimization and Engineering, 2015
We focus on a particular class of optimal design problems in elasticity where the objective function depends on the stresses along the boundary to be optimized. This is an issue of interest with many engineering applications. This work describes a gradient-type method to solve the finite element numerical approximation of such problems. The descent direction of the discrete cost functional is computed as a discrete projection of the continuous gradient formula, which is derived systematically from shape derivatives and a careful local coordinates calculus. The computational procedure is presented together with an illustrative example, namely the optimization of a cross-sectional tunnel vault immersed in a linearly elastic terrain to obtain uniform compression along the vault.
Networks & Heterogeneous Media
In this paper we study the optimal reinforcement of an elastic membrane, fixed at its boundary, by means of a network (connected one-dimensional structure), that has to be found in a suitable admissible class. We show the existence of an optimal network, and observe that such network carries a multiplicity that in principle can be strictly larger than one. Some numerical simulations are shown to confirm this issue and to illustrate the complexity of the optimal network when the total length becomes large.
2015
Membrane structures are one of spatial structures that allow for long span and light weight roofs. In many cases, the membrane roofs are supported with trusses or mats and prestressed together with cables to obtain a resistant shape for a given loading condition. For the design of membrane structures, nonlinear analysis is required. Besides, modeling of each membrane element and form-finding of the shape are of great importance in the design process. First, an equilibriumfinding analysis is conducted for the purpose of obtaining the optimal shape of the membrane structure, during which the initial stresses of the
2018
In this paper, we are interested in a shape optimization problem for a fluid-structure interaction system composed by an elastic structure immersed in a viscous incompressible fluid. The cost functional to minimize is an energy functional involving together the fluid and the elastic parts of the structure. The shape optimization problem is introduced in the 2-dimensional case. However the results in this paper are obtained for a simplified free-boundary 1-dimensional problem. We prove that the shape optimization problem is wellposed. We study the shape differentiability of the free-boundary 1-dimensional model. The full characterization of the associated material derivatives is given together with the shape derivative of the energy functional. A special case is explicitly solved, showing the relevancy of this shape optimization approach for a simplified free boundary 1-dimensional problem. The full model in two spatial dimensions is under studies now.
Progress in Nonlinear Differential Equations and Their Applications, 2006
Journal of Mathematical Sciences, 2009
The parabolic N-membranes problem for the p-Laplacian and the complete order constraint on the components of the solution is studied in what concerns the approximation, the regularity and the stability of the variational solutions. We extend to the evolutionary case the characterization of the Lagrange multipliers associated with the ordering constraint in terms of the characteristic functions of the coincidence sets. We give continuous dependence results, and study the asymptotic behavior as t → ∞ of the solution and the coincidence sets, showing that they converge to their stationary counterparts. Dedicated to V.A. Solonnikov, on the occasion of his 75th birthday, with admiration and friendship.
2013
We consider a Canham-Helfrich-type variational problem defined over closed surfaces enclosing a fixed volume and having fixed surface area. The problem models the shape of multiphase biomembranes. It consists of minimizing the sum of the Canham-Helfrich energy, in which the bending rigidities and spontaneous curvatures are now phase-dependent, and a line tension penalization for the phase interfaces. By restricting attention to axisymmetric surfaces and phase distributions, we extend our previous results for a single phase (arXiv:1202.1979) and prove existence of a global minimizer.
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