References of "Duysinx, Pierre"
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See detailMicrostructural design using stress–based topology optimization
Collet, Maxime ULg; Bruggi, Matteo; Noël, Lise ULg et al

Conference (2016, September 12)

New additive manufacturing techniques break the limitations encountered for years when producing components descending from topology optimization. Classical design procedures focus on macro-structural ... [more ▼]

New additive manufacturing techniques break the limitations encountered for years when producing components descending from topology optimization. Classical design procedures focus on macro-structural optimization to sustain given loads but today innovative manufacturing processes allow considering structures exhibiting tailored microstructures, i.e. the well known microstructural design. The practical applications of structures including material design is mainly motivated by the greater performances that can be achieved compared to classical solutions. Microstructural design has been shown a great interest as attested by recent works. However, stress–based topology optimization has not yet been extensively exploited when addressing microstructural design using numerical homogenization though stress constraints is an important feature and have gained in interest in the field of topology optimization. This contribution investigates the problem of material design enforcing stress constraints within periodic microstructures by considering a representative volume element (RVE) subject to prescribed strain fields. The SIMP approach is adopted as material interpolation law while the optimization problems are solved using a sequential convex programming approach. In particular the well known method of moving asymptotes (MMA) is considered. Numerical homogenization is used to assess the effective elastic properties of the microstructures. The Von Mises stress criterion is used to impose the constraints on the stress level. This work discusses the formulation of a well-posed design problem as well as some numerical issues encountered. The developed solution procedure is first validated by comparison against analytical results, e.g. the single inclusion of Vigdergauz microstructure. [less ▲]

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See detailOverhanging Constraints in Addivitive Manufacturing Using Two Different Tools
Bauduin, Simon ULg; Collet, Maxime ULg; Duysinx, Pierre ULg

Conference (2016, September 12)

Topology optimization is widely used as a design tool for advanced application in mechanical, aerospace and automotive industries. This technique offers an optimal distribution of a predetermined amount ... [more ▼]

Topology optimization is widely used as a design tool for advanced application in mechanical, aerospace and automotive industries. This technique offers an optimal distribution of a predetermined amount of material in a given design space. In the last years, a lot of efforts has been invested into the development of high performance methods such as homogenization, SIMP or BESO. However as the state of the art in manufacturing experiences evolution, a coupling between topology optimization and additive manufacturing is needed. Additive manufacturing has numerous advantages that fits the characteristics of topology optimized designs. It can manufacture highly complex design without high cost increase and furthermore continuous density material of the SIMP method could be manufactured by lattice structures. With all the opportunities given by the additive manufacturing the urge to bind the last one to topology optimization is heavily required. Specific constraints related to manufacturing issues have to be taken into account such as the need of supports structures to ensure a good heat evacuation during the manufacturing process, as well as to hold up overhanging section. Some researches have been done to try to include this constraint in the optimization problem such as Leary and al or Andrew T. Gaynor. However this work focuses on 2 different methods (projection scheme and mechanical approach) to tackle the overhanging problem and compare them . [less ▲]

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See detailStructural design considering damage within an XFEM-level set framework
Noël, Lise ULg; Duysinx, Pierre ULg; Maute, Kurt

Conference (2016, September)

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See detailOverhanging Constraints in Addivitive Manufacturing Using Two Different Tools
Bauduin, Simon ULg; Collet, Maxime ULg; Duysinx, Pierre ULg

Poster (2016, August 23)

Topology optimization is widely used as a design tool for advanced application in mechanical, aerospace and automotive industries. This technique offers an optimal distribution of a predetermined amount ... [more ▼]

Topology optimization is widely used as a design tool for advanced application in mechanical, aerospace and automotive industries. This technique offers an optimal distribution of a predetermined amount of material in a given design space. In the last years, a lot of efforts has been invested into the development of high performance methods such as homogenization, SIMP or BESO. However as the state of the art in manufacturing experiences evolution, a coupling between topology optimization and additive manufacturing is needed. Additive manufacturing has numerous advantages that fits the characteristics of topology optimized designs. It can manufacture highly complex design without high cost increase and furthermore continuous density material of the SIMP method could be manufactured by lattice structures. With all the opportunities given by the additive manufacturing the urge to bind the last one to topology optimization is heavily required. Specific constraints related to manufacturing issues have to be taken into account such as the need of supports structures to ensure a good heat evacuation during the manufacturing process, as well as to hold up overhanging section. Some researches have been done to try to include this constraint in the optimization problem such as Leary and al or Andrew T. Gaynor. However this work focuses on 2 different methods (projection scheme and mechanical approach) to tackle the overhanging problem and compare them . [less ▲]

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See detailDesign of microstructures using stress-based topology optimization
Collet, Maxime ULg; Bruggi, Matteo; Noël, Lise ULg et al

Conference (2016, August 22)

This paper aims at designing microstructures using stress-based topology optimization. Most of the developments so far have been made for compliance design in various field of applications as reflected in ... [more ▼]

This paper aims at designing microstructures using stress-based topology optimization. Most of the developments so far have been made for compliance design in various field of applications as reflected in the literature. The emergence of the new additive manufacturing techniques allows to consider porous material, such as lattice structures for instance, which ca be used for the design of structural components subject to various solicitations. Those components must account for the stress level to prevent failure everywhere in the microstructures and by extension the whole structure itself. This work proposes to design such microstructures using topology optimization with limitation on the stress level within the microstructures before printing the result. The homogenization technique is used to determine the equivalent material properties. The issues and perspectives are also discussed. [less ▲]

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See detailStructural design under damage constraints with XFEM and level sets
Noël, Lise ULg; Duysinx, Pierre ULg; Maute, Kurt

Conference (2016, August)

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See detailTopology optimization for minimum weight with compliance and simpli ed nominal stress constraints for fatigue resistance
Collet, Maxime ULg; Bruggi, Matteo; Duysinx, Pierre ULg

in Structural and Multidisciplinary Optimization (2016)

This work investigates a simpli ed approach to cope with the optimization of preliminary design of structures under local fatigue constraints along with a global enforcement on the overall compliance. The ... [more ▼]

This work investigates a simpli ed approach to cope with the optimization of preliminary design of structures under local fatigue constraints along with a global enforcement on the overall compliance. The problem aims at the minimization of the weight of linear elastic structures under given loads and boundary conditions. The expected sti ness of the optimal structure is provided by the global constraint, whereas a set of local stress-based constraints ask for a structure to be fatigue resistant. A modi ed Goodman fatigue strength comparison is implemented through the same formalism to address pressure-dépendent failure in materials as in Drucker-Prager strength criterion. As a simplification, the Sines approach is used to de ne the equivalent mean and alternating stresses to address the fatigue resistance for an infinite life time. Sines computation is based on the equivalent mean and alternate stress depending on the invariants of the stress tensor and itsdeviatoric part, respectively. The so-called singularity phenomenon is overcome by the implementation of a suitable qp-relaxation of the equivalent stress measures. Numerical examples are presented to illustrate the features of the achieved optimal layouts and of the proposed algorithm. [less ▲]

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See detailDesign Sensitivity Analysis for Shape Optimization of Nonlinear Magnetostatic Systems
Kuci, Erin ULg; Henrotte, François; Duysinx, Pierre ULg et al

in IEEE Transactions on Magnetics (2016), 52(3),

The paper discusses the sensitivity analysis for the shape optimization of a nonlinear magnetostatic system, evaluated both by direct and adjoint approaches. The calculations rely on the Lie derivative ... [more ▼]

The paper discusses the sensitivity analysis for the shape optimization of a nonlinear magnetostatic system, evaluated both by direct and adjoint approaches. The calculations rely on the Lie derivative concept of differential geometry where the flow is the velocity field associated with the modification of a geometrical parameter in the model. The resulting sensitivity formulas can be expressed naturally in a finite element setting through a volume integral in the layer of elements connected to the surface undergoing shape modification. The accuracy of the methodology is analyzed on a 2D model of an interior permanent magnet motor (IPM), and on a 3D model of a permanent magnet system. [less ▲]

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See detailOn the equivalent static load method for flexible multibody systems described with a nonlinear finite element formalism
Tromme, Emmanuel ULg; Sonneville, Valentin ULg; Bruls, Olivier ULg et al

in International Journal for Numerical Methods in Engineering (2016)

The equivalent static load (ESL) method is a powerful approach to solve dynamic response structural optimization problems. The method transforms the dynamic response optimization into a static response ... [more ▼]

The equivalent static load (ESL) method is a powerful approach to solve dynamic response structural optimization problems. The method transforms the dynamic response optimization into a static response optimization under multiple load cases. The ESL cases are defined based on the transient analysis response whereupon all the standard techniques of static response optimization can be used. In the last decade, the ESL method has been applied to perform the structural optimization of flexible components of mechanical systems modeled as multibody systems (MBS). The ESL evaluation strongly depends on the adopted formulation to describe the MBS and has been initially derived based on a floating frame of reference formulation. In this paper, we propose a method to derive the ESL adapted to a nonlinear finite element approach based on a Lie group formalism for two main reasons. Firstly, the finite element approach is completely general to analyze complex MBS and is suitable to perform more advanced optimization problems like topology optimization. Secondly, the selected Lie group formalism leads to a formulation of the equations of motion in the local frame, that turns out to be a strong practical advantage for the ESL evaluation. Examples are provided to validate the proposed method. [less ▲]

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See detailUnilateral contact condition enhanced with squeeze film modelling in automotive differentials
Virlez, Geoffrey; Bruls, Olivier ULg; Duysinx, Pierre ULg et al

in Proceedings of the Institution of Mechanical Engineers - Part C - Journal of Mechanical Engineering Science (2016), 230(7-8), 1243-1257

The dynamic behaviour of automotive drivetrains is significantly influenced by contacts occurring between the various parts. In this paper, a three-dimensional formulation is proposed to model unilateral ... [more ▼]

The dynamic behaviour of automotive drivetrains is significantly influenced by contacts occurring between the various parts. In this paper, a three-dimensional formulation is proposed to model unilateral and frictional contact conditions between two rigid planar rings. The magnitude of the contact force is determined by a penalty method. In a second step, a simple squeeze film model is developed to account for the damping effect produced by the lubricating oil filling the gap between the two contacting bodies. The relevance and the accuracy of these models are illustrated through the global multibody modelling of a TORSEN differential. [less ▲]

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See detailAnalytical sensitivity analysis using the extended finite element method in shape optimization of bimaterial structures
Noël, Lise ULg; Van Miegroet, Laurent; Duysinx, Pierre ULg

in International Journal for Numerical Methods in Engineering (2016)

The present work investigates the shape optimization of bimaterial structures. The problem is formulated using a level set description of the geometry and the extended finite element method (XFEM) to ... [more ▼]

The present work investigates the shape optimization of bimaterial structures. The problem is formulated using a level set description of the geometry and the extended finite element method (XFEM) to enable an easy treatment of complex geometries. A key issue comes from the sensitivity analysis of the structural responses with respect to the design parameters ruling the boundaries. Even if the approach does not imply any mesh modification, the study shows that shape modifications lead to difficulties when the perturbation of the level sets modifies the set of extended finite elements. To circumvent the problem, an analytical sensitivity analysis of the structural system is developed. Differences between the sensitivity analysis using FEM or XFEM are put in evidence. To conduct the sensitivity analysis, an efficient approach to evaluate the so-called velocity field is developed within the XFEM domain. The proposed approach determines a continuous velocity field in a boundary layer around the zero level set using a local finite element approximation. The analytical sensitivity analysis is validated against the finite differences and a semi- analytical approach. Finally our shape optimization tool for bimaterial structures is illustrated by revisiting the classical problem of the shape of soft and stiff inclusions in plates. [less ▲]

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See detailSimplified fatigue resistance in mechanical engineering using topology optimization
Collet, Maxime ULg; Bruggi, Matteo; Bauduin, Simon ULg et al

Conference (2015, July 09)

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See detailDeterministic Manufacturing constraints for Optimal Distribution in the Case of Additive Manufacturing
Bauduin, Simon ULg; Collet, Maxime ULg; Duysinx, Pierre ULg et al

Conference (2015, July 09)

An overview of the difficulties of coupling additive manufacturing to topology optimization with various solution founded and implemented.

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See detailStress constrained topology optimization for additive manufacturing: Specific character and solution aspects
Duysinx, Pierre ULg

Conference (2015, July 07)

Since the fundamental work by Bendsøe and Kikuchi (1988), topology optimization has been based on compliance type formulations (Bendsoe & Sigmund, 2003) while the number of works considering stress ... [more ▼]

Since the fundamental work by Bendsøe and Kikuchi (1988), topology optimization has been based on compliance type formulations (Bendsoe & Sigmund, 2003) while the number of works considering stress constraints are rather limited (Duysinx & Bendsoe, 1998). More recently the generalized shape optimization approach using level set methods (see for instance Allaire, Jouve, Troader, 2004, Belytchko, Xiao, Parimi, 2003) has followed the tracks of topology optimization and has mainly been focusing on compliance minimization problems. The ‘compliance type’ formulation has produced quite interesting results in many problems because controlling the energy and the displacements under the loads is generally favourable for deflection control and because, for one load case, the compliance minimization leads to a fully stressed design nearly everywhere in the structure. However there are theoretical results that clearly show that the strongest and the stiffest structural layout can be quite different. As demonstrated in Rozvany & Birker (1994) truss topology optimization can lead to different results when there are several load cases, different stress limits in tension and compression, or when there are several materials involved. Therefore, the first goal of the paper points out the importance of considering stress constraints as soon as the preliminary design phase, that is, to include stress constraints in the topology optimization problem. Revisiting some contributions of the authors, this paper aims at illustrating the key role of stress constraints in the framework of topology optimization of continuum structures. The recent developments are able to treat: • Integrated stress criteria (i.e. global) relaxed stress constraints that aggregate the stress constraints in each finite element in order to be able to circumvent the large scale character of the local stress constraints. • Stress criteria that are able to tackle non equal stress limits in tension and compression. The usual von Mises criterion is unable to predict real-life designs when the structure is made of materials with unequal stress limits like concrete or composite materials. These different behaviours in tension and compression result in quite specific designs. Numerical applications make possible to point out the different nature of structural lay out for maximum strength and maximum stiffness. This one is clearly demonstrated in two kinds of particular situations: once several load cases are considered and when unequal stress limits in tension and compression are involved. The second contribution of the paper deals with the solution aspects of large scale constrained optimization problems. Because of the huge number of design variables, dual methods combined with local convex approximations such as CONLIN (Fleury, 1989) or MMA (Svanberg, 1987) are well indicated to solve classical topology optimization methods. However stress constrained problems introduce also a so large number of active constraints that one comes to a rather delicate situation. We show that the optimizer effort increases mostly as the cube of the number of constraints. In order to circumvent the problem, the idea developed in the paper is to combine first or second order approximations (Bruyneel, Duysinx, Fleury, 2002) with zero order approximations of stress constraints, especially for the subset of restrictions that are likely not to be active or not to change too fast. At first the paper presents the way to derive zero-order approximations of -relaxed stress constraints (that is necessary to cope with the singularity phenomenon of stress constraints in topology optimization). Then the proposed hybrid approach mixing approximation of different orders is benchmarked on numerical applications illustrating the reduction of computation time for solving optimization problems without sacrifying to the robustness and efficiency. Numerical applications will investigate topology optimized benchmark examples combined with additive manufacturing fabrication to illustrate the developments. [less ▲]

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See detailStructural optimization of multibody system components described using level set techniques
Tromme, Emmanuel ULg; Tortorelli, Daniel; Bruls, Olivier ULg et al

in Structural and Multidisciplinary Optimization (2015)

The structural optimization of the components in multibody systems is performed using a fully coupled optimization method. The design’s predicted response is obtained from a flexible multibody system ... [more ▼]

The structural optimization of the components in multibody systems is performed using a fully coupled optimization method. The design’s predicted response is obtained from a flexible multibody system simulation under various service conditions. In this way, the resulting optimization process enhances most existing studies which are limited to weakly coupled (quasi-) static or frequency domain loading conditions. A level set description of the component geometry is used to formulate a generalized shape optimization problem which is solved via efficient gradient-based optimization methods. Gradients of cost and constraint functions are obtained from a sensitivity analysis which is revisited in order to facilitate its implementation and retain its computational efficiency. The optimizations of a slider-crank mechanism and a 2-dof robot are provided to exemplify the procedure. [less ▲]

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See detailA level set approach for the structural optimization of flexible mechanisms
Tromme, Emmanuel ULg; Tortorelli, Daniel; Bruls, Olivier ULg et al

Conference (2015, June 08)

With the evolution of virtual prototyping, mechanical systems are commonly analyzed using a multibody system (MBS) approach to study the behavior of the entire system and notably the dynamic interactions ... [more ▼]

With the evolution of virtual prototyping, mechanical systems are commonly analyzed using a multibody system (MBS) approach to study the behavior of the entire system and notably the dynamic interactions between the components. Modern structural optimization of mechanical systems considers the dynamic loading exerted on the individual flexible components. The consideration is an essential feature and can be implemented in two ways. Firstly, one can consider a strong coupling wherein the component’s optimization is performed using the time dependent loading conditions coming directly from the MBS simulation. Secondly, one can consider a weak coupling wherein the component’s optimization is performed using a series of static load cases that do not fully account for the interactions between the components of the MBS. Rather this approach performs a MBS simulation to evaluate the loads for the initial design and then optimizes the component assuming the loads do not change. The process of evaluating the loads and then performing the optimization is repeated until suitable convergence criteria is satisfied, assuming convergence is possible. The present paper focuses on the strong coupling method wherein the flexible MBS dynamic analysis is based on a nonlinear finite element formalism [1]. A level set (LS) description of the component geometry is used to enable a generalized shape optimization. The LS approach combines the advantages of shape and topology optimizations. Moreover, since the component boundaries are defined by CAD features, the manufacturing process is facilitated as no post-processing step of a rasterized design is required. The design sensitivity analysis for MBS is revisited in order to facilitate its implementation. The optimization of a slider-crank mechanism and a 2-dof robot is provided to exemplify the procedure. [1] Géradin M., Cardona A. (2001) Flexible Multibody Dynamics: A Finite Element Approach. John Wiley & Sons, New York. [less ▲]

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See detailTopology optimization of mechanical and aerospace components subject to fatigue stress constraints
Duysinx, Pierre ULg; Collet, Maxime ULg; Bauduin, Simon ULg et al

Conference (2015, June 08)

While topology optimization has been based mostly on compliance type formulations, industrial applications call for more elaborated formulations including several restrictions on the local displacements ... [more ▼]

While topology optimization has been based mostly on compliance type formulations, industrial applications call for more elaborated formulations including several restrictions on the local displacements and the stress constraints in some critical zones. Topology optimization with stress constraints was initially considered in Duysinx & Bendsoe (1998). Later the stress constraint formulation was further extended to consider non equal stress constraints limits Bruggi & Duysinx (2012) and to improve the solution efficiency using different strategies such as global stress constraint formulations (Duysinx & Sigmund, 1998, Le et al. 2010). In the present work, the authors are investigating the formulations of stress constraint topology optimization to support the redesign of structural components that have to be fabricated using additive manufacturing. In this perspective, design problem requirements include tackling fatigue constraints during stress constrained topology optimization. The work investigates different formulations of fatigue resistance which could be appropriate in a topology approach. At first the classical approach of mechanical engineering based on SN curves and Goodman or Soderberg lines. The treatment of these fatigue restrictions can take advantage of former work developed for unequal stress constraints by considering mean and alternating components of the stress state. In a second step our research is now focussing on more complex situations (3D stress states) which require resorting to more advanced criteria. Dang Van fatigue theory (Dang Van, Griveau, Message, 1989) has been selected but calls for a more elaborated procedure that is currently validated. Topology optimized structural layouts predicted using classical stress criteria, Goodman and Dang Van theories are compared. [less ▲]

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See detailDesign Sensitivity Analysis for Shape Optimization of Nonlinear Magnetostatic Systems
Kuci, Erin ULg; Duysinx, Pierre ULg; Dular, Patrick ULg et al

in Proceedings of COMPUMAG 2015 (2015, June)

In this paper, a direct and an adjoint analytic sensitivity analysis for a nonlinear magnetostatic system is obtained, in the context of shape optimization for any design function. The calculations are ... [more ▼]

In this paper, a direct and an adjoint analytic sensitivity analysis for a nonlinear magnetostatic system is obtained, in the context of shape optimization for any design function. The calculations are based on the material derivative concept of continuum mechanics. The resulting sensitivity formula can be expressed as either a volume integral or as a boundary integral along the interface where shape modification occurs. A method for the calculation of the design velocity field and mesh updating scheme is introduced as well. The accuracy of the methodology is analysed on an inductor system, suggesting that the volume integration technique should be preferred. All methods are freely available for further testing in the open source environment GetDP/Gmsh. [less ▲]

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