References of "ZHANG, Weihong"
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See detailSimultaneous design of structural layout and discrete fiber orientation using bi-value coding parameterization and volume constraint
TONG, Gao; ZHANG, Weihong; Duysinx, Pierre ULg

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 ▲]

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See detailA bi-value coding parameterization scheme for the discrete optimal orientation design of the composite laminate
Gao, Tong ULg; ZHANG, Weihong; Duysinx, Pierre ULg

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 ▲]

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See detailEvaluation of the mechanical properties of plasma-sprayed coating by nanoindentation technology
Guo, Weichao; Rauchs, Gast; Papeleux, Luc ULg 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 ▲]

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See detailNew developments for an efficient solution of the discrete material topology optimization of composite structures
Duysinx, Pierre ULg; Gao, Tong; Zhang, Weihong 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 ▲]

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See detailSTUDY OF THE INFLUENCE OF FRICTION IN IMPERFECT CONICAL INDENTATION FOR ELASTO-PLASTIC MATERIAL
Ponthot, Jean-Philippe ULg; Guo, Weichao; Rauchs, Gast 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 ▲]

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See detailDual approach using a variant perimeter constraint and efficient sub-iteration scheme for topology optimization
Zhang, Weihong; Duysinx, Pierre ULg

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 ▲]

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See detailA Generalized Method of Moving Asymptotes (GMMA) Including Equality Constraints
Zhang, Weihong; Fleury, Claude ULg; Duysinx, Pierre ULg et al

in Structural Optimization (1996), 12(2/3), 143-146

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See detailA New Separable Approximation Scheme for Topological Problems and Optimization Problems Characterized by a Large Number of Design Variables
Duysinx, Pierre ULg; Zhang, Weihong; Fleury, Claude ULg 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 ▲]

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See detailStructural Shape Optimization with Error Control
Duysinx, Pierre ULg; Zhang, Weihong; Zhong, H. G. 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 ▲]

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See detailSensitivity Analysis With Unstructured Free Mesh Generators in 2-D Shape Optimization
Duysinx, Pierre ULg; Zhang, Weihong; Fleury, Claude ULg

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 ▲]

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