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This paper focuses on the optimization of a linear actuator by the “output space mapping (OSM)” method. The underlying objective of this work lies in the minimization of the time required for the achievement of this optimal design. Indeed, in addition to the sole costs of optimization processes strictly speaking, the time needed for the developpement of the models is taken into account. In the context of OSM, two different finite-element models of the same actuator are used. This paper presents these modeling solutions and considers their corresponding accuracy. Results of this multi-objective optimization method are presented and compared with those obtained by the sequential simplex (SS) method based solely on the fine model. Both approaches give similar results. However, the comparison of their performances clearly shows that the OSM algorithm is an effective technique for reducing the computation time of optimization studies, even in the case of relatively simple electromagnetic structures. Hence, this approach leads to an original and effective optimization methodology. [ABSTRACT FROM AUTHOR]

Abstract: Integrated design of the structure topology and involved component layout is a challenging design issue when compared with traditional topology optimization. In this paper, we propose an implicit modeling approach that works completely on an Eulerian finite element mesh throughout the whole optimization process. To this aim, implicit level-set functions and R-functions are employed to describe geometrical shapes of movable components. In particular, a modified arctan function is adopted to depict the material discontinuity along the interface between the structure domain and each component domain. They are then used for material interpolations and analytical sensitivity analysis w.r.t. both pseudo-density design variables and location design variables related to the host structure and components, respectively. Based on a variety of numerical tests, it is demonstrated that considered design problems with movable components can easily be solved by extending the SIMP material model based topology optimization approach using an Eulerian mesh and the gradient-based optimization algorithm. [Copyright &y& Elsevier]

Abstract: This paper describes a new numerical method for the design of multi-step stamping tools, in which the optimization approach is based on the Response Surface Method (RSM) with Kriging interpolation as well as the Sequential Quadratic Programming (SQP) algorithm. The present work attempts to provide a reliable methodology for the optimum design of the forming tools in order to produce a desired part by multi-step stamping within a severe tolerance (0.1mm). The numerical method has been proposed to reduce the number of forming steps and therefore increasing the process productivity. To reach this goal, an integrated optimization approach, using the commercial finite element code ABAQUS© together with an optimization algorithm was developed. The optimization algorithm consists in constructing an explicit form of the objective function according to the design variables. To search the global optimum of the objective function, the SQP algorithm has been used. A thin metallic part formed by manual press and without blank-holder has been considered, to demonstrate the effectiveness of the optimization approach to get the optimal tools shape in a few iterations. [Copyright &y& Elsevier]

Abstract: The reconstruction of the equilibrium of a plasma in a Tokamak is a free boundary problem described by the Grad–Shafranov equation in axisymmetric configuration. The right-hand side of this equation is a nonlinear source, which represents the toroidal component of the plasma current density. This paper deals with the identification of this nonlinearity source from experimental measurements in real time. The proposed method is based on a fixed point algorithm, a finite element resolution, a reduced basis method and a least-square optimization formulation. This is implemented in a software called Equinox with which several numerical experiments are conducted to explore the identification problem. It is shown that the identification of the profile of the averaged current density and of the safety factor as a function of the poloidal flux is very robust. [Copyright &y& Elsevier]

The aim of this paper is to present an efficient numerical procedure for the theoretical study of bimolecular reactions. It is based on the R matrix variational formalism and the p-version of the finite element method (p-FEM) for expanding the wave function in a finite basis set, and facilitates the development of an efficient algorithm to invert matrices that significantly reduces the computational time in R matrix calculations. We also utilise the self-consistent finite element method to optimise the elements mesh and provide faster convergence of results. We apply our methodology to the study of the collinear H + H process and evaluate its efficiency by comparing our results with several results previously published in the literature. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents an improved ant colony optimization (IACO) for the design of planar steel frames. The algorithm consists of two phases: the global search phase and the local search phase. In the global search phase, IACO employs a sub-optimization mechanism (SOM) based on the principles of finite element methods to reduce the search space, the size of the trail matrix, the number of analyses and consequently the optimization time. In the local search phase, a final optimum design is obtained considering W-shaped sections from the available steel sections specified by the American Institute of Steel Construction (AISC) in the neighborhood of the result gained in the previous phase. The proposed method is tested on several frames from the literature. In order to verify the suitability of the present method, the results of optimum design for several planar steel frames are obtained by the present study and compared to those of the standard ant colony optimization, the genetic algorithm and the harmony search algorithm. The results indicate that the computational time required for the improved ant colony optimization is considerably reduced. [Copyright &y& Elsevier]

In the present work, fluid–structure interaction problems are analysed by means of optimised boundary element–finite element coupling procedures. The boundary element method is here employed to numerically model acoustic fluids and the finite element method is applied to discretise dynamic bodies (nonlinear effects included). Boundary element—finite element coupling is accomplished by an iterative algorithm: each boundary element or finite element sub-domain is analysed independently (as an uncoupled model) and a successive renewal of the variables at the common interfaces is performed, until convergence is achieved. The evaluation of an optimised relaxation parameter is introduced taking into account the minimisation of a square error functional. The algorithm that arises is more efficient and stable, representing an advancement of the iterative procedure. At the end of the paper, numerical examples are presented, illustrating the potentialities of the proposed methodology. [Copyright &y& Elsevier]

In this paper we develop a posteriori error estimates for finite element discretization of elliptic optimization problems with pointwise inequality constraints on the control variable. We derive error estimators for assessing the discretization error with respect to the cost functional as well as with respect to a given quantity of interest. These error estimators provide quantitative information about the discretization error and guide an adaptive mesh refinement algorithm allowing for substantial saving in degrees of freedom. The behavior of the method is demonstrated on numerical examples. [ABSTRACT FROM AUTHOR]

In this paper, an algorithm is derived to solve a problem of inverse acoustics. It considers the damped acoustic boundary value problem, i.e. the Helmholtz equation and admittance boundary condition, in order to approximate the boundary admittance of interior domains. The algorithm is implemented by using a finite element method and tested for two-dimensional cavities with arbitrary shapes. The admittance condition is reconstructed based on sound pressure measurements. The solution of the arising nonlinear system of equations is obtained by applying the Newton method following a presetting method for finding reasonable initial boundary admittance values. A residual norm accounts for the objective function. Its first- and second-order sensitivities are determined analytically by using a modal decomposition in order to avoid direct inversion of the system matrix. The experiment is simulated by taking sound pressure data of the forward solution as inputs for the inverse problem. Test examples show that very few measurement points are necessary to reproduce piecewise constant boundary admittance values very accurately. Then, the admittance boundary condition is applied to reproduce the sound pressure distribution in the cavity. Again, it becomes obvious that only a few measurement points are required to reconstruct the sound pressure field. [ABSTRACT FROM AUTHOR]