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  Subjects -> ENGINEERING (Total: 2017 journals)
    - CHEMICAL ENGINEERING (159 journals)
    - CIVIL ENGINEERING (153 journals)
    - ELECTRICAL ENGINEERING (86 journals)
    - ENGINEERING (1135 journals)
    - ENGINEERING MECHANICS AND MATERIALS (308 journals)
    - HYDRAULIC ENGINEERING (48 journals)
    - INDUSTRIAL ENGINEERING (52 journals)
    - MECHANICAL ENGINEERING (76 journals)

CIVIL ENGINEERING (153 journals)                  1 2     

ACI Structural Journal     Full-text available via subscription   (Followers: 6)
Acta Polytechnica : Journal of Advanced Engineering     Open Access  
Acta Structilia : Journal for the Physical and Development Sciences     Open Access   (Followers: 2)
Advances in Civil Engineering     Open Access   (Followers: 25)
Advances in Structural Engineering     Full-text available via subscription   (Followers: 20)
Ambiente Construído     Open Access   (Followers: 2)
American Journal of Civil Engineering and Architecture     Open Access   (Followers: 16)
Architectural Engineering     Open Access   (Followers: 3)
Archives of Civil Engineering     Open Access   (Followers: 7)
Archives of Hydro-Engineering and Environmental Mechanics     Open Access   (Followers: 2)
ATBU Journal of Environmental Technology     Open Access   (Followers: 1)
Australian Journal of Structural Engineering     Full-text available via subscription   (Followers: 4)
Baltic Journal of Road and Bridge Engineering     Full-text available via subscription  
BER : Building and Construction : Full Survey     Full-text available via subscription   (Followers: 8)
BER : Building Contractors' Survey     Full-text available via subscription   (Followers: 3)
BER : Building Sub-Contractors' Survey     Full-text available via subscription   (Followers: 2)
BER : Survey of Business Conditions in Building and Construction : An Executive Summary     Full-text available via subscription   (Followers: 5)
Berkeley Planning Journal     Open Access   (Followers: 5)
Bioinspired Materials     Open Access  
Bridge Structures : Assessment, Design and Construction     Hybrid Journal   (Followers: 12)
Building and Environment     Hybrid Journal   (Followers: 12)
Building Women     Full-text available via subscription  
Built Environment Project and Asset Management     Hybrid Journal   (Followers: 13)
Canadian Journal of Civil Engineering     Full-text available via subscription   (Followers: 12)
Case Studies in Engineering Failure Analysis     Open Access   (Followers: 3)
Cement and Concrete Composites     Hybrid Journal   (Followers: 8)
Change Over Time     Full-text available via subscription   (Followers: 3)
Civil and Environmental Research     Open Access   (Followers: 12)
Civil Engineering     Hybrid Journal   (Followers: 11)
Civil Engineering = Siviele Ingenieurswese     Full-text available via subscription   (Followers: 5)
Civil Engineering and Architecture     Open Access  
Civil Engineering and Environmental Systems     Hybrid Journal   (Followers: 4)
Civil Engineering and Technology     Open Access   (Followers: 2)
Civil Engineering Dimension     Open Access   (Followers: 3)
Cohesion and Structure     Full-text available via subscription   (Followers: 2)
Composite Structures     Hybrid Journal   (Followers: 70)
Computer-aided Civil and Infrastructure Engineering     Hybrid Journal   (Followers: 8)
Computers & Structures     Hybrid Journal   (Followers: 20)
Concrete Research Letters     Open Access   (Followers: 1)
Constructii : Journal of Civil Engineering Research     Open Access   (Followers: 5)
Construction Engineering     Open Access   (Followers: 3)
Construction Management and Economics     Hybrid Journal   (Followers: 27)
Construction Science     Open Access   (Followers: 1)
Constructive Approximation     Hybrid Journal  
Earthquake Engineering and Structural Dynamics     Hybrid Journal   (Followers: 13)
Enfoque UTE     Open Access   (Followers: 2)
Engineering Project Organization Journal     Hybrid Journal   (Followers: 4)
Engineering Structures     Hybrid Journal   (Followers: 13)
Engineering Structures and Technologies     Hybrid Journal   (Followers: 2)
Engineering, Construction and Architectural Management     Hybrid Journal   (Followers: 16)
Environmental Geotechnics     Open Access  
European Journal of Environmental and Civil Engineering     Hybrid Journal   (Followers: 3)
Fatigue & Fracture of Engineering Materials and Structures     Hybrid Journal   (Followers: 13)
Frattura ed Integrità Strutturale : Fracture and Structural Integrity     Open Access   (Followers: 1)
Frontiers of Structural and Civil Engineering     Hybrid Journal   (Followers: 4)
Geomaterials     Open Access   (Followers: 2)
Geosystem Engineering     Hybrid Journal   (Followers: 3)
Geotechnik     Hybrid Journal  
Géotechnique Letters     Hybrid Journal   (Followers: 3)
HBRC Journal     Open Access   (Followers: 1)
HVAC&R Research     Hybrid Journal   (Followers: 1)
Indoor and Built Environment     Hybrid Journal   (Followers: 1)
Ingenio Magno     Open Access  
Insight - Non-Destructive Testing and Condition Monitoring     Full-text available via subscription   (Followers: 4)
International Journal for Service Learning in Engineering     Open Access  
International Journal of 3-D Information Modeling     Full-text available via subscription   (Followers: 2)
International Journal of Advanced Structural Engineering     Open Access   (Followers: 7)
International Journal of Concrete Structures and Materials     Open Access   (Followers: 5)
International Journal of Construction Engineering and Management     Open Access   (Followers: 3)
International Journal of Protective Structures     Full-text available via subscription   (Followers: 5)
International Journal of Steel Structures     Hybrid Journal   (Followers: 4)
International Journal of Structural Engineering     Hybrid Journal   (Followers: 7)
International Journal of Structural Integrity     Hybrid Journal  
International Journal of Structural Stability and Dynamics     Hybrid Journal   (Followers: 5)
International Journal of Sustainable Built Environment     Open Access   (Followers: 2)
International Journal of Sustainable Construction Engineering and Technology     Open Access   (Followers: 7)
ISRN Civil Engineering     Open Access   (Followers: 4)
ISRN Power Engineering     Open Access   (Followers: 1)
Journal of Accessibility and Design for All     Open Access   (Followers: 4)
Journal of Applied Fire Science     Full-text available via subscription   (Followers: 1)
Journal of Bridge Engineering     Full-text available via subscription   (Followers: 14)
Journal of Building Performance Simulation     Hybrid Journal   (Followers: 3)
Journal of Civil Engineering and Construction Technology     Open Access   (Followers: 3)
Journal of Civil Engineering and Management     Hybrid Journal   (Followers: 6)
Journal of Civil Engineering and Science     Open Access   (Followers: 10)
Journal of Civil Engineering Research     Open Access   (Followers: 10)
Journal of Civil Society     Hybrid Journal   (Followers: 2)
Journal of Civil Structural Health Monitoring     Hybrid Journal   (Followers: 1)
Journal of Composites     Open Access   (Followers: 16)
Journal of Composites for Construction     Full-text available via subscription   (Followers: 9)
Journal of Computing in Civil Engineering     Full-text available via subscription   (Followers: 19)
Journal of Construction Engineering     Open Access   (Followers: 3)
Journal of Construction Engineering and Management     Full-text available via subscription   (Followers: 21)
Journal of Construction Engineering, Technology & Management     Full-text available via subscription   (Followers: 3)
Journal of Constructional Steel Research     Hybrid Journal   (Followers: 7)
Journal of Earth Sciences and Geotechnical Engineering     Open Access   (Followers: 1)
Journal of Fluids and Structures     Hybrid Journal   (Followers: 2)
Journal of Frontiers in Construction Engineering     Open Access   (Followers: 1)
Journal of Green Building     Full-text available via subscription   (Followers: 7)
Journal of Highway and Transportation Research and Development (English Edition)     Full-text available via subscription   (Followers: 5)

        1 2     

Journal Cover Structural and Multidisciplinary Optimization
   [6 followers]  Follow    
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
     ISSN (Print) 1615-1488 - ISSN (Online) 1615-147X
     Published by Springer-Verlag Homepage  [2210 journals]   [SJR: 1.273]   [H-I: 54]
  • Topology optimization of Prager structures based on truss-like material
           model
    • Abstract: Abstract A finite element method is presented to optimize Prager structures using a truss-like material model. The members are assumed to be distributed over the design domain continuously but non-uniformly, and their densities and orientations at nodes are taken as design variables. The initial loads are applied to the design domain uniformly, and the densities of members are optimized by fully stressed criteria, with the members aligning along the principal direction of stress. Concomitantly, loads are moved to the elevations of the centroid along the vertical direction. Through iterating the above procedure until convergence, Prager structures can be optimized into anisotropic structures in which most of the arches are not parallel to each other.
      PubDate: 2014-11-22
       
  • Continuum shape sensitivity analysis and what-if study for two-dimensional
           
    • Abstract: Abstract This paper presents a shape sensitivity analysis and what-if study for two-dimensional multi-scale crack propagation problems using bridging scale decomposition. The sensitivity equations are derived in a continuum setting using direct differentiation method based on a continuum variational formulation of the bridging scale. Due to the fact that the crack propagation speed in an atomistic simulation is discrete in design, and cannot be formulated as a continuous function of shape design variables, we propose a hybrid method that combines analytical sensitivity analysis with finite difference approach. The finite difference part of the sensitivity analysis is only intended for calculating the sensitivity of crack growth speed based on the analytically obtained sensitivity coefficients of structural responses. The theoretical development on sensitivity formulation in this paper extends the application of the method to irregular-shaped finite elements and general design velocity fields. Furthermore, we evaluate and compare several performance measures that quantify crack propagation speed based on crack tip locations for sensitivity analysis and ultimately for structural optimization. A two-dimensional beam example is used to verify the accuracy of the proposed sensitivity approach. It is also demonstrated through a what-if study that with an adequate performance measure, the impact of macroscopic shape changes on microscopic crack propagation speed can be accurately predicted.
      PubDate: 2014-11-20
       
  • Experimental flapping wing optimization and uncertainty quantification
           using limited samples
    • Abstract: Abstract Flapping wing micro air vehicles are capable of hover and forward flight with high maneuverability. However, flapping wing flight is difficult to simulate accurately because it is a more complex phenomenon than fixed wing or rotorcraft flight. Consequently, the optimization of flapping wing behavior based on simulation is limited and, therefore, we have elected to optimize a wing experimentally. Specifically, we use experimental data to optimize the flapping wing structure for maximum thrust production in hover mode. We point out the similarities or otherwise between experimental optimization and the more common simulation-based optimization. Experimental optimization is hampered by noisy data, which is due to manufacturing variability and testing/measurement uncertainty in this study. These uncertainties must be reduced to an acceptable level and this requires their quantification. Therefore, improvements in manufacturing and testing procedures were implemented to reduce the noise. Another challenge is to limit the number of experiments for reducing time and cost. This is realized by using surrogates, or meta-models, to approximate the response (in this case, thrust) of the wing. In order to take into account the uncertainty, or noise, in the response, we use a Gaussian Process surrogate with noise and a 2nd order polynomial response surface. We apply a surrogate-based optimization algorithm called Efficient Global Optimization with different sampling criteria and multiple surrogates. This enables us to select multiple points per optimization cycle, which is especially useful in this case as it is more time efficient to manufacture multiple wings at once and this also serves as insurance against failed designs.
      PubDate: 2014-11-20
       
  • Matlab code for a level set-based topology optimization method using a
           reaction diffusion equation
    • Abstract: Abstract This paper presents a simple Matlab implementation for a level set-based topology optimization method in which the level set function is updated using a reaction diffusion equation, which is different from conventional level set-based approaches (Allaire et al. 2002, 2004; Wang et al. 2003) that use the Hamilton-Jacobi equation to update the level set function. With this method, the geometrical complexity of optimized configurations can be easily controlled by appropriately setting a regularization parameter. We explain the code in detail, and also the derivation of the topological derivative that is used in the level set-based topology optimization. Numerical results for stiffness maximization problems are provided to facilitate the reader’s understanding. The presented code is intended for educational purposes only. This paper was inspired by previously published papers presenting Matlab code for a SIMP method (Sigmund 2001; Andreassen et al. 2011), a level set-based method (Challis 2010), and FreeFem ++ code for a structural optimization method (Allaire and Pantz 2006). Readers can investigate results provided by these different methods and discover the prominent aspects of each particular method. The code presented here can be downloaded from http://www.osdel.me.kyoto-u.ac.jp/members/yamada/codes.html.
      PubDate: 2014-11-19
       
  • An active learning kriging model for hybrid reliability analysis with both
           random and interval variables
    • Abstract: Abstract Hybrid reliability analysis (HRA) with both random and interval variables is investigated in this paper. Firstly, it is figured out that a surrogate model just rightly predicting the sign of performance function can meet the requirement of HRA in accuracy. According to this idea, a methodology based on active learning Kriging (ALK) model named ALK-HRA is proposed. When constructing the Kriging model, the presented method only finely approximates the performance function in the region of interest: the region where the sign tends to be wrongly predicted. Based on the constructed Kriging model, Monte Carlo Simulation (MCS) is carried out to estimate both the lower and upper bounds of failure probability. ALK-HRA is accurate enough with calling the performance function as few times as possible. Four numerical examples and one engineering application are investigated to demonstrate the performance of the proposed method.
      PubDate: 2014-11-19
       
  • An adaptive hybrid approach for reliability-based design optimization
    • Abstract: Abstract Reliability-based design optimization (RBDO) is a powerful tool for design optimization with consideration of uncertainty. It can be solved by double loop approaches or single loop approaches, while double loop approaches are robust but their implementation is computationally costly. On the other hand, single loop approaches are highly efficient but may have convergence problem for highly nonlinear performance measure functions. To mend their respective drawbacks, we resort to a transition between them and propose the so-called adaptive hybrid approach (AHA) to take advantage of these two approaches. Based on a function type criterion, AHA adaptively selects the single loop or double loop approaches during the iteration. When single loop strategy is selected, the advanced mean value (AMV) method is used. When double loop strategy is selected, an improved adaptive chaos control (ACC) method is proposed to searches for the most probable target point (MPTP) of black-box function robustly and efficiently. Four illustrative examples, including two nonlinear analytical problems and two engineering applications, demonstrate the superior efficiency and robustness of the AHA over other prevalent approaches.
      PubDate: 2014-11-18
       
  • Distributed material density and anisotropy for optimized eigenfrequency
           of 2D continua
    • Abstract: Abstract A practical approach to optimize a continuum/structural eigenfrequency is presented, including design of the distribution of material anisotropy. This is often termed free material optimization (FMO). An important aspect is the separation of the overall material distribution from the local design of constitutive matrices, i.e., the design of the local anisotropy. For a finite element (FE) model the amount of element material is determined by a traditional optimality criterion (OC) approach. In this respect the major value of the present formulation is the derivation of simple eigenfrequency gradients with respect to material density and from this values of the element OC. Each factor of this expression has a physical interpretation. Stated alternatively, the optimization problem of material distribution is converted into a problem of determining a design of uniform OC values. The constitutive matrices are described by non-dimensional matrices with unity norms of trace and Frobenius, and thus this part of the optimized design has no influence on the mass distribution. Gradients of eigenfrequency with respect to the components of these non-dimensional constitutive matrices are therefore simplified, and an additional optimization criterion shows that the optimized redesign of anisotropy are described directly by the element strains. The fact that all components of an optimal constitutive matrix are expressed by the components of a strain state, imply a reduced number of independent components of an optimal constitutive matrix. For 3D problems from 21 to 6 parameters, for 2D from 6 to 3 parameters, and for axisymmetric problems from 10 to 4 parameters.
      PubDate: 2014-11-16
       
  • In-plane optimization of truss arch footbridges using stability and
           serviceability objective functions
    • Abstract: Abstract This paper investigates the use of stability and serviceability objective functions in the shape optimization of truss arch footbridges prone to in-plane snap-through buckling. The objective functions evaluated relate to global linear buckling, geometrically nonlinear response, fundamental frequency, linear compliance, and maximum deflection. These objective functions are applied to help define the global structural shape for the 2D configuration of a truss arch footbridge subjected to its governing code-defined load combination. The strength criterion of maximum axial force, the global stability responses of critical linear buckling load and nonlinear limit load, and the serviceability responses of fundamental frequency and unfactored live load deflection are used to evaluate the optimized topologies. These structural performance results are compared to those of a benchmark structure prone to in-plane snap-through buckling. The results highlight that improvement in stability and serviceability behavior can be obtained by altering the global structural form according to the presented objective functions. Stable optimized topologies, which are not prone to in-plane snap-though buckling, are achieved without the use of computationally expensive, geometrically nonlinear analysis functions.
      PubDate: 2014-11-14
       
  • Optimization of the motion control mechanism of the hatch door of airliner
    • Abstract: Abstract This paper deals with the problem of parameter optimization of the motion control mechanism of the hatch door of ARJ21-700, a regional airliner of China. Motion improvement of the hatch door is implemented by two kinds of passive designs. Firstly, a single-layer optimization model for trajectory modification is developed to find the optimum size of the key parts of the control mechanism. Secondly, a novel nested bi-level optimization model is presented for the design of the size tolerance limits of the selected parts. The design objective is minimization of the total extremum deviation of the motion trajectory of the objective point of the hatch door, where the extremum deviation is obtained by solution of the inner-level size optimization problem for the fixed size tolerance limits. The optimization models for motion control of the hatch door mechanism are solved using the response surface method. Numerical examples show that the precision of the real running trajectory of the objective point of the hatch door mechanism may be improved effectively by using the methods presented. A home-made multi-body dynamics solver (THUSOLVER) and the corresponding optimization software have been developed to implement the above tasks.
      PubDate: 2014-11-12
       
  • Topology optimization of front metallization patterns for solar cells
    • Abstract: Abstract This paper presents the application of topology optimization (TO) for designing the front electrode patterns for solar cells. Improving the front electrode design is one of the approaches to improve the performance of the solar cells. It serves to produce the voltage distribution for the front surface such that the current flow through the solar cell is maximized. In this paper, we use TO to design the front electrode pattern for side-contact and pin-up modules. Specific challenges include the nonlinearity of the physical problem and the design-dependent photocurrent loading. The greater design freedom of TO versus traditional shape optimization generates novel, efficient electrode patterns. In addition, we study the effect of mesh resolution and solar cell size on the final design. The results suggest that TO can probably be an effective method to generate designs which could lead to improved performance of the solar cells.
      PubDate: 2014-11-12
       
  • Differential geometry tools for multidisciplinary design optimization,
           part II: application to QSD
    • Abstract: Abstract Having previously developed a differential geometry framework for analyzing and conceptualizing Multidisciplinary Design Optimization (MDO) problems and methods, we now apply that framework to consider the Quasi-Separable Decomposition (QSD) architecture. Based on our theoretical investigations, we predict that QSD will fail to return feasible designs for MDO problems. In the same vein, we analyze the Individual Discipline Feasible (IDF) architecture, predict that IDF will converge to feasible designs, and propose a modified version of QSD which we believe will also output feasible design points. To test these predictions, we run all three architectures on a well-known analytical MDO problem. Our predictions regarding feasibility prove to be accurate: QSD does not return any feasible points, whereas all of the final design points from IDF and the modified QSD are feasible. Now that convergence to feasibility has been established, the next step is to investigate the optimization performance of various QSD modifications.
      PubDate: 2014-11-09
       
  • Differential geometry tools for multidisciplinary design optimization,
           Part I: Theory
    • Abstract: Abstract Analysis within the field of Multidisciplinary Design Optimization (MDO) generally falls under the headings of architecture proofs and sensitivity information manipulation. We propose a differential geometry (DG) framework for further analyzing MDO systems, and here, we outline the theory undergirding that framework: general DG, Riemannian geometry for use in MDO, and the translation of MDO into the language of DG. Calculating the necessary quantities requires only basic sensitivity information (typically from the state equations) and the use of the implicit function theorem. The presence of extra or non-differentiable constraints may limit the use of the framework, however. Ultimately, the language and concepts of DG give us new tools for understanding, evaluating, and developing MDO methods; in Part I, we discuss the use of these tools and in Part II, we provide a specific application.
      PubDate: 2014-11-09
       
  • Local continuum shape sensitivity with spatial gradient reconstruction for
           nonlinear analysis
    • Abstract: Abstract Gradient-based optimization for large-scale, multidisciplinary design problems requires accurate and efficient sensitivity analysis to compute design derivatives. Presented here is a nonintrusive analytic sensitivity method, that is relatively easy to implement. Furthermore, it can be as accurate as conventional analytic sensitivity methods, which are intrusive and tend to be difficult, if not infeasible, to implement. The nonintrusive local continuum shape sensitivity method with spatial gradient reconstruction (SGR) is formulated for nonlinear systems. This is an extension of the formulation previously published for linear systems. SGR, a numerical technique used to approximate spatial derivatives, can be leveraged to implement the sensitivity method in a nonintrusive manner. The method is used to compute design derivatives for a variety of applications, including nonlinear static beam bending, nonlinear transient gust response of a 2-D beam structure, and nonlinear static bending of rectangular plates. To demonstrate that the method is nonintrusive, all analyses are conducted using black box solvers. One limiting requirement of the method is that it requires the converged Jacobian or tangent stiffness matrix as output from the analysis tool. For each example the design derivatives of the structural displacement response are verified with finite difference calculations.
      PubDate: 2014-11-07
       
  • Laminate stacking sequence optimization with strength constraints using
           two-level approximations and adaptive genetic algorithm
    • Abstract: Abstract A stacking sequence optimization method, which is conducted on the basis of a ground laminate and utilizes a two-level approximation as well as a genetic algorithm (GA), was developed before by the authors. Compared with general GAs, this method shows lower computational costs while reaching a high level of practical feasibility. However, the published work did not involve problems constrained with a strength requirement, which is essential for laminate structures subject to multiple loading conditions. Thus, in the present study, this approach is extended to implement strength constraints for laminate stacking sequence optimizations. First, to avoid the selection of some control parameters in the GA as well as to improve its performance, the standard genetic algorithm is modified with adaptive schemes in the fitness function and GA operators. Furthermore, by adopting the first-ply failure criterion and considering the stresses/strains for each layer in the ground laminate, the concept of temporal deletion techniques is proposed to extend this approach for handling optimization problems with strength constraints. Moreover, by combining the optimizer with the general finite element software MSC. Patran/Nastran, an optimization framework is established to conduct the optimization easily. Numerical examples are performed in repeated runs to illustrate the performance of the modified approaches in the GA as well as the feasibility and efficiency of this optimization system.
      PubDate: 2014-11-06
       
  • System-of-systems approach to air transportation design using nested
           optimization and direct search
    • Abstract: Abstract Aircraft sizing, route network design, demand estimation and allocation of aircraft to routes are different facets of the air transportation optimization problem that can be viewed as individual “systems,” since they can be conducted independently. In fact, there is a large body of literature that investigates each of these as a stand-alone problem. In this regard, the air transportation design optimization problem can be viewed as an optimal system-of-systems (SoS) design problem. The resulting mixed variable programming problem may not be solvable using an all-in-one (AiO) approach because its size and complexity grow rapidly with increasing number of network nodes. In this work, we use a decomposition-based nested formulation and the Mesh Adaptive Direct Search (MADS) optimization algorithm to solve the optimal SoS design problem. The two-stage expansion of an regional Canadian airline’s network to enable national operations is considered as a demonstrating example.
      PubDate: 2014-11-06
       
  • Random field modeling with insufficient field data for probability
           analysis and design
    • Abstract: Abstract Often engineered systems entail randomness as a function of spatial (or temporal) variables. The random field can be found in the form of geometry, material property, and/or loading in engineering products and processes. In some applications, consideration of the random field is a key to accurately predict variability in system performances. However, existing methods for random field modeling are limited for practical use because they require sufficient field data. This paper thus proposes a new random field modeling method using a Bayesian Copula that facilitates the random field modeling with insufficient field data and applies this method for engineering probability analysis and robust design optimization. The proposed method is composed of three key ideas: (i) determining the marginal distribution of random field realizations at each measurement location, (ii) determining optimal Copulas to model statistical dependence of the field realizations at different measurement locations, and (iii) modeling a joint probability density function of the random field. A mathematical problem was first employed for the purpose of demonstrating the accuracy of the random field modeling with insufficient field data. The second case study deals with the assembly process of a two-door refrigerator that challenges predicting the door assembly tolerance and minimizing the tolerance by designing the random field and parameter variables in the assembly process with insufficient random field data. It is concluded that the proposed random field modeling can be used to successfully conduct the probability analysis and robust design optimization with insufficient random field data.
      PubDate: 2014-11-04
       
  • Topology optimization of electrode coverage of piezoelectric thin-walled
           structures with CGVF control for minimizing sound radiation
    • Abstract: Abstract It is impractical to implement arbitrary-shaped piezoelectric patches from the view point of manufacturability of fragile piezoelectric ceramics, thus using designable electrode layers to deliver desired actuation forces provides a more realistic option in engineering applications. This study develops a topological design method of surface electrode distribution over piezoelectric sensors/actuators attached to a thin-walled shell structure for reducing the sound radiation in an unbounded acoustic domain. In the optimization model, the sound pressure norm at specific reference points under excitations at a certain excitation frequency or in a given frequency range is taken as the objective function. The pseudo densities for indicating absence and presence of surface electrodes at each element are taken as the design variables, and a penalized relationship between the densities and the active damping effect is employed. The vibrating structure is discretized with finite element model for the frequency response analysis and the sound radiation analysis in the unbounded acoustic domain is treated by boundary element method. The applied voltage on each actuator is determined by the constant gain velocity feedback (CGVF) control law. The technique of the complex mode superposition in the state space, in conjunction with a model reduction transformation, is adopted in the response analysis of the system characterized by a non-proportional active damping property. In this context, the adjoint-variable sensitivity analysis scheme is derived. The effectiveness and efficiency of the proposed method are demonstrated by numerical examples, and several key factors on the optimal designs are also discussed.
      PubDate: 2014-11-01
       
  • Solving multiobjective optimization problems using quasi-separable MDO
           formulations and analytical target cascading
    • Abstract: Abstract One approach to multiobjective optimization is to define a scalar substitute objective function that aggregates all objectives and solve the resulting aggregate optimization problem (AOP). In this paper, we discern that the objective function in quasi-separable multidisciplinary design optimization (MDO) problems can be viewed as an aggregate objective function (AOF). We consequently show that a method that can solve quasi-separable problems can also be used to obtain Pareto points of associated AOPs. This is useful when AOPs are too hard to solve or when the design engineer does not have access to the models necessary to evaluate all the terms of the AOF. In this case, decomposition-based design optimization methods can be useful to solve the AOP as a quasi-separable MDO problem. Specifically, we use the analytical target cascading methodology to formulate decomposed subproblems of quasi-separable MDO problems and coordinate their solution in order to obtain Pareto points of the associated AOPs. We first illustrate the approach using a well-known simple geometric programming example and then present a vehicle suspension design problem with three objectives related to ground vehicle ride and handling.
      PubDate: 2014-11-01
       
  • Optimization of gridshell bar orientation using a simplified genetic
           approach
    • Abstract: Abstract Gridshells are defined as structures that have the shape and rigidity of a double curvature shell but consist of a grid instead of a continuous surface. This study concerns those obtained by elastic deformation of an initially flat two-way grid. This paper presents a novel approach to generate gridshells on an imposed shape under imposed boundary conditions. A numerical tool based on a geometrical method, the compass method, is developed. It is coupled with genetic algorithms to optimize the orientation of gridshell bars in order to minimize the stresses and therefore to avoid bar breakage during the construction phase. Examples of application are shown.
      PubDate: 2014-11-01
       
  • Multidisciplinary design modeling and optimizationfor satellite with
           maneuver capability
    • Abstract: Abstract According to the mission of a satellite with maneuver capability, the collaborative optimization (CO) method was introduced for the satellite system design, and the related multidisciplinary design optimization (MDO) model was established. The possessing and needed velocity increments Δv and Δv n e e d were taken as the measurement of maneuvering capability of the studied satellite, which were then combined with total mass of the satellite to form the optimization objective in the systematic level of the MDO problem. The design variables and constraints of the MDO problem dealt with disciplines or subsystems as guidance, navigation and control (GNC), power, and structure, and corresponding engineering analysis models were also built. A program system to solve the MDO problem wasdeveloped by integrating a non-nested CO method, the commercial and user-supplied codes on framework software iSIGHT. The result showed that the satellite performance could be obviously improved, which also indicates MDO technique is feasible and effective for the spacecraft design problem. The modeling and optimization procedure of the work can be referred for further research and engineering design.
      PubDate: 2014-11-01
       
 
 
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