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Simultaneous design of structural layout and discrete fiber orientation using bi-value coding parameterization and volume constraint ; ; Duysinx, Pierre in Structural and Multidisciplinary Optimization (2013), 48(6), 1075-1088 The so-called bi-value coding parameterization (BCP) method is developed for the simultaneous optimization of layout design and discrete fiber orientations of laminated structures related to the ... [more ▼] The so-called bi-value coding parameterization (BCP) method is developed for the simultaneous optimization of layout design and discrete fiber orientations of laminated structures related to the compliance minimization and natural frequency maximization. Both kinds of problems are transformed into a discrete material selection problem that is then solved as a continuous topology optimization problem with multiphase materials. A new form of the volume constraint is introduced in accordance with the BCP to control the material usage and material removal in the corresponding problem formulation. The BCP scheme assigning the integer value of +1 or -1 to each design variable for the unique “coding” is efficiently used to interpolate discrete fiber orientations and to identify the presence and removal of materials. Meanwhile, a general set-up strategy is proposed by assigning “uniform” weight values in BCP to ensure the feasibility of the initial starting point. Numerical tests illustrate that the BCP is efficient in dealing with both kinds of design problems including the volume constraint. [less ▲] Detailed reference viewed: 42 (3 ULg)A bi-value coding parameterization scheme for the discrete optimal orientation design of the composite laminate Gao, Tong ; ; Duysinx, Pierre in International Journal for Numerical Methods in Engineering (2012), 91(1), 98-114 The discrete optimal orientation design of the composite laminate can be treated as a material selection problem dealt with by continuous topology optimization method. In this work, a new bi-value coding ... [more ▼] The discrete optimal orientation design of the composite laminate can be treated as a material selection problem dealt with by continuous topology optimization method. In this work, a new bi-value coding parameterization (BCP) scheme is proposed to this aim. The idea of the BCP scheme is to “code” each material phase using integer values of +1 and -1. Each available material phase has one unique “code” consisting of +1 and/or -1 assigned to design variables. Theoretical and numerical comparisons between the proposed BCP scheme and existing schemes show that the BCP has the advantage of an evident reduction of the number of design variables in logarithmic form. This is very beneficial when the number of candidate materials becomes important. Numerical tests with up to 36 candidate material orientations are illustrated for the first time to indicate the reliability and efficiency of the proposed scheme in solving this kind of problem. It proves that the BCP is an interesting and potential scheme to achieve the optimal orientations for large-scale design problems. [less ▲] Detailed reference viewed: 55 (3 ULg)Mechanical Buckling of Composite Panels with/without Cutouts ; ; Ponthot, Jean-Philippe in International Journal of Plant Engineering and Management (2012), 17(2), 65-76 A simpli ed analytical solution suitable for simple stacking sequences was developed using the Euler buckling theory, the structure's equations of equilibrium and laminate panel mathematical formulation ... [more ▼] A simpli ed analytical solution suitable for simple stacking sequences was developed using the Euler buckling theory, the structure's equations of equilibrium and laminate panel mathematical formulation. Comparing these results with numerical results reveals the ac- curacy of the method and even more, allows us to validate the numerical analysis. Therefore, two important results are obtained : a simpli ed analytical solution for the buckling problem and vali- dation of the numerical results. Another important and novel nding is related to the in uence of the angle ply orientation and of the cutouts, on the buckling load. Under symmetrical boundary conditions and loading case, rectangular panels with elliptical cutouts, give better results for 90 oriented plies than for 0 oriented ones. With a compression load applied in the X direction, and with material properties 10 times better in X direction than in Y direction, the best results are obtained when the load is aligned with the Y direction associated to the material reference frame. Moreover, panels with cutouts seem to behave better than panels without cutouts under certain ply orientation angles. [less ▲] Detailed reference viewed: 24 (0 ULg)Evaluation of the mechanical properties of plasma-sprayed coating by nanoindentation technology ; ; Papeleux, Luc et al in Mechanics & Industry (2012), 13(3), 151-162 In this paper, the mechanical properties of plasma-sprayed coatings are evaluated using the technology of nanoindentation. According to the indentation curve (load versus indenter’s displacement), which ... [more ▼] In this paper, the mechanical properties of plasma-sprayed coatings are evaluated using the technology of nanoindentation. According to the indentation curve (load versus indenter’s displacement), which is recorded in an indentation experiment, the mechanical behaviour of the plasma-sprayed coating is investigated via inverse analysis using numerical optimization algorithms. The tip rounding of imperfect indenters is investigated in parameter identification. Subsequently, the hardness on the top surface and on the vertical cross section of the plasma-sprayed coating are investigated. The results show that the hardness on the top surface of the coating depends on the indentation depth. Moreover, the results show that the hardness on the cross section of the coating is significantly affected by the substrate if the indentation impression is too close to the coating-substrate interface. [less ▲] Detailed reference viewed: 35 (4 ULg)New developments for an efficient solution of the discrete material topology optimization of composite structures Duysinx, Pierre ; ; et al in Faester, S.; Juul Jensen, D.; Ralph, B. (Eds.) et al Composite materials for structural performance: towards the higher limits (2011, September 05) Optimal design of composite structures can be formulated as an optimal selection of material in a list of different laminates. Based on the seminal work by Stegmann and Lund (2005), the optimal problem ... [more ▼] Optimal design of composite structures can be formulated as an optimal selection of material in a list of different laminates. Based on the seminal work by Stegmann and Lund (2005), the optimal problem can be stated as a topology optimization problem with multiple materials. The research work carries out a large investigation of different interpolation and penalization schemes for the optimal material selection problem. Besides the classical Design Material Optimization (DMO) scheme and the recent Shape Function with Penalization (SFP) scheme by Bruyneel (2011), the research introduces a generalization of the SFP approach using a bi-value coding parameterization (BCP) (Gao, Zhang, and Duysinx, 2011) The paper provides a comparison of the different parameterization approaches. It also proposes alternative penalization schemes and it investigates the effect of the power penalization. Finally, we discuss the solution aspects in the perspective of solving large-scale industrial applications. The conclusions are illustrated by a numerical application for the compliance maximization of an in-plane composite ply. [less ▲] Detailed reference viewed: 98 (4 ULg)Comparison of volume constraint and mass constraint in structural topology optimization with multiple materials ; ; Duysinx, Pierre in Rodrigues, Helder (Ed.) Book of abstracts and proceeding of the 2nd International Conference on Engineering Optimization (2010, September 06) Instead of adopting the common idea of using volume constraint in topology optimization, this work investigates alternative formulations of the design problem of multiphase structures based on other mass ... [more ▼] Instead of adopting the common idea of using volume constraint in topology optimization, this work investigates alternative formulations of the design problem of multiphase structures based on other mass and single phase volume constraints. [less ▲] Detailed reference viewed: 16 (1 ULg)STUDY OF THE INFLUENCE OF FRICTION IN IMPERFECT CONICAL INDENTATION FOR ELASTO-PLASTIC MATERIAL Ponthot, Jean-Philippe ; ; et al in Tribology-Materials, Surfaces & Interfaces (2009), 3(4), 151-157 The investigation of this paper provides a rationale of the influence of friction in nanoindentation testing for elasto-plastic solids. The emphasis is placed on providing a detailed evaluation of the ... [more ▼] The investigation of this paper provides a rationale of the influence of friction in nanoindentation testing for elasto-plastic solids. The emphasis is placed on providing a detailed evaluation of the influence of the friction coefficient on the calculated hardness using an imperfect indenter. A new method for calculating the material hardness is derived. The new function can take into account the combined effects of friction and imperfect indenter tip geometry. For further investigations, some numerical simulations are executed. The results show that the new function can provide a good relationship for the hardness calculated in all friction cases. Moreover, the numerical simulations show that the friction coefficient does not significantly affect the curve of load versus indentation depth, whereas it significantly influences the deformations of the specimen surface around the indenter for some materials. [less ▲] Detailed reference viewed: 39 (7 ULg)Dual approach using a variant perimeter constraint and efficient sub-iteration scheme for topology optimization ; Duysinx, Pierre in Computers & Structures (2003), 81(22-23), 2173-2181 To prevent numerical instabilities associated with the mesh-dependence, checkerboards and grey regions in topology optimization, a variant perimeter-constrained version of the SIMP algorithm is proposed ... [more ▼] To prevent numerical instabilities associated with the mesh-dependence, checkerboards and grey regions in topology optimization, a variant perimeter-constrained version of the SIMP algorithm is proposed using a smooth and quadratic function. In order to have an efficient implementation and to make sure the strict satisfaction of such an upper-bound perimeter constraint, a diagonal quadratic approximation of the perimeter constraint is used in the construction of each explicit optimization subproblem. The latter is then solved by a dual sub-iteration scheme. Numerical results show that the incorporation of such a sub-iteration scheme leads to a convergent solution without needs of move-limits or artificial control parameters. In addition to this, it is found that successive relaxations of the perimeter constraint by increasing the upper-bound tend to regularize the topology solution and result in a checkerboard free and satisfactory design solution without grey regions. [less ▲] Detailed reference viewed: 31 (0 ULg)A Generalized Method of Moving Asymptotes (GMMA) Including Equality Constraints ; Fleury, Claude ; Duysinx, Pierre et al in Structural Optimization (1996), 12(2/3), 143-146 Detailed reference viewed: 100 (3 ULg)A New Separable Approximation Scheme for Topological Problems and Optimization Problems Characterized by a Large Number of Design Variables Duysinx, Pierre ; ; Fleury, Claude et al in Olhoff, Niels; Rozvany, Georges I.N. (Eds.) Proceedings of the First World Congress of Structural and Multidisciplinary Optimization (WCSMO1) (1995, May) This paper is dedicated to a new convex separable approximation for solving optimization problems characterized by a very large number of design variables as in topology design. For such problems, the ... [more ▼] This paper is dedicated to a new convex separable approximation for solving optimization problems characterized by a very large number of design variables as in topology design. For such problems, the convergence speed can be accelerated if one uses high quality approximation schemes for structural responses. To achieve this task, we propose, here, a new approximation procedure that belongs to the GMMA family. The originality of this new scheme is to rely on an automatic selection procedure of the asymptotes, using only first and zero order information accumulated during the previous iterations. This is possible owing to a diagonal Quasi-Newton update technique. Firstly, the new approximation procedure is validated on classical "benchmarks" of structural optimization. Then, it is compared to other schemes on a typical topology optimization problem. [less ▲] Detailed reference viewed: 106 (2 ULg)Structural Shape Optimization with Error Control Duysinx, Pierre ; ; et al in Proceedings of 20th ASME Design Automation Conference (1994, September) A robust and automatic shape optimization procedure is presented in this paper, which incorporates recent developments in the field of computer-aided design (CAD) of mechanical structures, such as ... [more ▼] A robust and automatic shape optimization procedure is presented in this paper, which incorporates recent developments in the field of computer-aided design (CAD) of mechanical structures, such as geometric modelling, automatic selection of independent design variables, sensitivity analysis using reliable mesh perturbation schemes, error estimation and adaptive mesh refinement. A numerical example is given to show the efficiency of the procedure. [less ▲] Detailed reference viewed: 100 (12 ULg)Sensitivity Analysis With Unstructured Free Mesh Generators in 2-D Shape Optimization Duysinx, Pierre ; ; Fleury, Claude in Herskowitz, José (Ed.) Proceedings of Structural Optimization 93, The World Congress on Optimal Design of Structural Systems (1993, August) Shape optimization has to consider new progress in mesh generators to take full benefits from the use of free unstructured meshes in realistic industrial optimization. The main difficulty relies in the ... [more ▼] Shape optimization has to consider new progress in mesh generators to take full benefits from the use of free unstructured meshes in realistic industrial optimization. The main difficulty relies in the mesh flow determination during sensitivity analysis. The authors present their experience in applying smoothing techniques to transmit boundary perturbations to the inner mesh. It is explained how smoothing can be used to evaluate velocity fields in a simple and inexpensive way while guarantying reliability, efficiency and precision. A wide range of smoothing procedures are compared and confronted with other velocity field approaches to investigate their advantages and drawback. Finally, applications of smoothing procedures in the commercial optimization package OPTI-SAMCEF are described. [less ▲] Detailed reference viewed: 61 (9 ULg) |
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