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  Subjects -> ENGINEERING (Total: 1955 journals)
    - CHEMICAL ENGINEERING (153 journals)
    - CIVIL ENGINEERING (148 journals)
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    - ENGINEERING (1111 journals)
    - HYDRAULIC ENGINEERING (45 journals)
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CIVIL ENGINEERING (148 journals)                  1 2     

ACI Structural Journal     Full-text available via subscription   (Followers: 5)
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: 23)
Advances in Structural Engineering     Full-text available via subscription   (Followers: 18)
Ambiente Construído     Open Access   (Followers: 2)
American Journal of Civil Engineering and Architecture     Open Access   (Followers: 15)
Architectural Engineering     Open Access   (Followers: 3)
Archives of Civil Engineering     Open Access   (Followers: 6)
Archives of Hydro-Engineering and Environmental Mechanics     Open Access   (Followers: 2)
ATBU Journal of Environmental Technology     Open Access  
Australian Journal of Structural Engineering     Full-text available via subscription   (Followers: 3)
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)
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: 11)
Case Studies in Engineering Failure Analysis     Open Access   (Followers: 3)
Cement and Concrete Composites     Hybrid Journal   (Followers: 7)
Change Over Time     Full-text available via subscription   (Followers: 3)
Civil and Environmental Research     Open Access   (Followers: 12)
Civil Engineering     Hybrid Journal   (Followers: 10)
Civil Engineering = Siviele Ingenieurswese     Full-text available via subscription   (Followers: 4)
Civil Engineering and Environmental Systems     Hybrid Journal   (Followers: 4)
Civil Engineering and Technology     Open Access   (Followers: 1)
Civil Engineering Dimension     Open Access   (Followers: 3)
Cohesion and Structure     Full-text available via subscription   (Followers: 2)
Composite Structures     Hybrid Journal   (Followers: 36)
Computer-aided Civil and Infrastructure Engineering     Hybrid Journal   (Followers: 7)
Computers & Structures     Hybrid Journal   (Followers: 17)
Concrete Research Letters     Open Access   (Followers: 1)
Constructii : Journal of Civil Engineering Research     Open Access   (Followers: 4)
Construction Engineering     Open Access   (Followers: 3)
Construction Management and Economics     Hybrid Journal   (Followers: 26)
Construction Science     Open Access   (Followers: 1)
Constructive Approximation     Hybrid Journal  
Earthquake Engineering and Structural Dynamics     Hybrid Journal   (Followers: 11)
Enfoque UTE     Open Access   (Followers: 2)
Engineering Project Organization Journal     Hybrid Journal   (Followers: 4)
Engineering Structures     Hybrid Journal   (Followers: 11)
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: 2)
Fatigue & Fracture of Engineering Materials and Structures     Hybrid Journal   (Followers: 12)
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: 5)
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: 3)
Journal of Applied Fire Science     Full-text available via subscription  
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: 2)
Journal of Civil Engineering and Management     Hybrid Journal   (Followers: 5)
Journal of Civil Engineering and Science     Open Access   (Followers: 9)
Journal of Civil Engineering Research     Open Access   (Followers: 9)
Journal of Civil Society     Hybrid Journal   (Followers: 2)
Journal of Civil Structural Health Monitoring     Hybrid Journal   (Followers: 1)
Journal of Composites     Open Access   (Followers: 7)
Journal of Composites for Construction     Full-text available via subscription   (Followers: 8)
Journal of Computing in Civil Engineering     Full-text available via subscription   (Followers: 18)
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: 6)
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)
Journal of Infrastructure Systems     Full-text available via subscription   (Followers: 13)
Journal of Legal Affairs and Dispute Resolution in Engineering and Construction     Full-text available via subscription   (Followers: 5)

        1 2     

Journal Cover Structural and Multidisciplinary Optimization
   Journal TOC RSS feeds Export to Zotero [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  [2209 journals]   [SJR: 1.273]   [H-I: 54]
  • Probabilistic sensitivity analysis for novel second-order reliability
           method (SORM) using generalized chi-squared distribution
    • Abstract: Abstract Reliability-based design optimization (RBDO) requires evaluation of sensitivities of probabilistic constraints. To develop RBDO utilizing the recently proposed novel second-order reliability method (SORM) that improves conventional SORM approaches in terms of accuracy, the sensitivities of the probabilistic constraints at the most probable point (MPP) are required. Thus, this study presents sensitivity analysis of the novel SORM at MPP for more accurate RBDO. During analytic derivation in this study, it is assumed that the Hessian matrix does not change due to the small change of design variables. The calculation of the sensitivity based on the analytic derivation requires evaluation of probability density function (PDF) of a linear combination of non-central chi-square variables, which is obtained by utilizing general chi-squared distribution. In terms of accuracy, the proposed probabilistic sensitivity analysis is compared with the finite difference method (FDM) using the Monte Carlo simulation (MCS) through numerical examples. The numerical examples demonstrate that the analytic sensitivity of the novel SORM agrees very well with the sensitivity obtained by FDM using MCS when a performance function is quadratic in U-space and input variables are normally distributed. It is further shown that the proposed sensitivity is accurate enough compared with FDM results even for a higher order performance function.
      PubDate: 2014-10-01
  • Multidisciplinary multifidelity optimisation of a flexible wing aerofoil
           with reference to a small UAV
    • Abstract: Abstract The preliminary Multidisciplinary Design and Optimisation of a flexible wing aerofoil apropos a small Unmanned Air Vehicle is performed using a multifidelity model-based strategy. Both the passively adaptive structure and the shape of the flexible wing aerofoil are optimised for best aerodynamic performance under aero-structural constraints, within a coupled aeroelastic formulation. A typical flight mission for surveillance purposes is considered and includes the potential occurrence of wind gusts. A metamodel for the high-fidelity objective function and each of the constraints is built, based on a tuned low-fidelity one, in order to improve the efficiency of the optimisation process. Both metamodels are based on solutions of the aeroelastic equations for a flexible aerofoil but employ different levels of complexity and computational cost for modelling aerodynamics and structural dynamics within a modal approach. The high-fidelity model employs nonlinear Computational Fluid Dynamics coupled with a full set of structural modes, whereas the low-fidelity one employs linear thin aerofoil theory coupled with a reduced set of structural modes. The low-fidelity responses are then corrected according to few high-fidelity responses, as prescribed by an appropriate Design of Experiment, by means of a suitable tuning technique. A standard Genetic Algorithm is hence utilised to find the global optimum, showing that a flexible aerofoil is characterised by higher aerodynamic efficiency than its rigid counterpart. Wing weight reduction is also accomplished when a Multiobjective Genetic Algorithm is adopted.
      PubDate: 2014-10-01
  • Bilevel multiobjective packaging optimization for automotive design
    • Abstract: Abstract The successful application of multiobjective optimization to engineering problems has motivated studies of more complex systems involving multiple subsystems and design disciplines, each with multiple design criteria. Complex system design requires participation of different teams that are highly specialized within each discipline and subsystem. Such a high differentiation results in limited sharing of information among the design teams. The mathematical modeling and the solution algorithm proposed in this paper address the issue of coordinating multiple design problems that negotiate according to conflicting criteria. The design of the layout of hybrid vehicles is formulated as a bilevel decomposed problem including a vehicle level and a battery level in concert with the specialization of the respective design teams required at each level. An iterative algorithm, the Multiobjective Decomposition Algorithm (MODA) is proposed, whose generated sequences are shown to converge to efficient designs for the overall design problem under certain conditions examined in the context of the block coordinate descent method and the method of multipliers. MODA applied to the hybrid electric design problem captures the bilevel tradeoffs originating by the conflicting objectives at the vehicle and battery levels.
      PubDate: 2014-10-01
  • Seismic optimum design of triple friction pendulum bearing subjected to
           near-fault pulse-like ground motions
    • Abstract: Abstract Triple Friction Pendulum Bearing (TFPB) as a novel seismic isolator, provides different combinations of stiffness and damping during its course of motion. The adaptive behavior of TFPBs is one of the practical solutions for unsuitable performance of seismic isolation systems under near-fault ground motions. Selecting the TFPB’s design variables (curvature radii, friction coefficients and displacement capacity of sliding surfaces) is complicated process while finding the optimized combination of these variables depends on input ground motion characteristics and seismic performance objectives of the superstructure. Here first, comprehensive nonlinear dynamic analyses are performed to identify influence of the design variables on superstructure response (roof acceleration and displacement of isolated level). Next, a specific numerical optimization method based on Genetic Algorithms (GA) is applied to determine the optimum values of the design variables that minimize superstructure demands. In this process, near-fault ground motions are employed with ranges of pulse periods and hazard levels as input excitations. According to GA results, the derived optimum design variables of TFPB have significantly distinct intervals for different target responses such as story drift and TFPB displacement. Therefore response targets (single objective functions) are combined to make a new fitness function. The proposed optimization method for determining design variables and design intervals can be used for investigating many other types of superstructures with similar behaviors.
      PubDate: 2014-10-01
  • Material interface effects on the topology optimizationof multi-phase
           structures using a level set method
    • Abstract: Abstract A level set method is used as a framework to study the effects of including material interface properties in the optimization of multi-phase elastic and thermoelastic structures. In contrast to previous approaches, the material properties do not have a discontinuous change across the interface that is often represented by a sharp geometric boundary between material regions. Instead, finite material interfaces with monotonic and non-monotonic property variations over a physically motivated interface zone are investigated. Numerical results are provided for several 2D problems including compliance and displacement minimization of structures composed of two and three materials. The results highlight the design performance changes attributed to the presence of the continuously graded material interface properties.
      PubDate: 2014-10-01
  • Eigenvalue topology optimization of structures using a parameterized level
           set method
    • Abstract: Abstract Preventing a structure from resonance is important in many real-world applications. Because an external excitation frequency can be lower than the fundamental eigenfrequency or between the eigenfrequencies of a structure, there is a strong need for eigenfrequency optimization technology to optimize the fundamental eigenfrequency and, in addition, the k-th eigenfrequency and to maximize the gap between eigenfrequencies. However, previous optimization studies on vibrating elastic structures that used the level set method have been devoted to the optimization of the fundamental eigenfrequency, whereas the higher-order eigenfrequencies optimization problem has seldom been considered. This paper presents an eigenfrequency optimization technology that is based on the compactly supported radial basis functions (CS-RBFs) parameterized level-set method, using the fundamental eigenfrequency, the eigenfrequency of a given higher-order, and the gap between two consecutive eigenfrequencies as the optimization objectives. Furthermore, to address the oscillation problem of the objective function, we adopt an exponential weighted optimization model of a number of the lower eigenfrequencies for multiple eigenvalue optimizations, and we utilize mode-tracking technology for the single eigenvalue optimization.In addition, we further extend the CS-RBFs parameterized level-set method to an optimization that is performed with geometric constraints, which means that the size and position of the regular holes in the structure can be optimized with the shape and topology. This approach is useful in real-world applications. The effectiveness of this method is demonstrated by several widely investigated examples that have various objectives.
      PubDate: 2014-10-01
  • The gradient projection method for structural topology optimization
           including density-dependent force
    • Abstract: Abstract This paper proposes a modified gradient projection method (GPM) that can solve the structural topology optimization problem including density-dependent force efficiently. The particular difficulty of the considered problem is the non-monotonicity of the objective function and consequently the optimization problem is not definitely constrained. Transformation of variables technique is used to eliminate the constraints of the design variables, and thus the volume is the only possible constraint. The negative gradient of the objective function is adopted as the most promising search direction when the point is inside the feasible domain, while the projected negative gradient is used instead on condition that the point is on the hypersurface of the constraint. A rational step size is given via a self-adjustment mechanism that ensures the step size is a good compromising between efficiency and reliability. Furthermore, some image processing techniques are employed to improve the layouts. Numerical examples with different prescribed volume fractions and different load ratios are tested respectively to illustrate the characteristics of the topology optimization with density-dependent load.
      PubDate: 2014-10-01
  • Optimal SVM parameter selection for non-separable and unbalanced datasets
    • Abstract: Abstract This article presents a study of three validation metrics used for the selection of optimal parameters of a support vector machine (SVM) classifier in the case of non-separable and unbalanced datasets. This situation is often encountered when the data is obtained experimentally or clinically. The three metrics selected in this work are the area under the ROC curve (AUC), accuracy, and balanced accuracy. These validation metrics are tested using computational data only, which enables the creation of fully separable sets of data. This way, non-separable datasets, representative of a real-world problem, can be created by projection onto a lower dimensional sub-space. The knowledge of the separable dataset, unknown in real-world problems, provides a reference to compare the three validation metrics using a quantity referred to as the “weighted likelihood”. As an application example, the study investigates a classification model for hip fracture prediction. The data is obtained from a parameterized finite element model of a femur. The performance of the various validation metrics is studied for several levels of separability, ratios of unbalance, and training set sizes.
      PubDate: 2014-10-01
  • Topological optimization of two-dimensional phononic crystals based on the
           finite element method and genetic algorithm
    • Abstract: Abstract By using the finite element method and a “coarse to fine” two-stage genetic algorithm as the forward calculation method and the inverse search scheme, respectively, we perform both the unconstrained and constrained optimal design of the unit cell topology of the two-dimensional square-latticed solid phononic crystals (PnCs), to maximize the relative widths of the gaps between the adjacent energy bands of the PnCs. In the constrained optimizations, the maximization is subjected to the constraint of a predefined average density. In the numerical results, the variation patterns of the optimized structures with the order of the bandgap for both the out-plane shear and the in-plane mixed elastic wave modes are presented, and the effects of both the material contrast and the predefined average density on the obtained optimal structures are discussed.
      PubDate: 2014-10-01
  • Sensitivity analysis of structural response to position of external
           applied load: in plane stress condition
    • Abstract: Abstract Procedures for sensitivity analysis of the structural responses, i.e., nodal displacement, mean compliance and local stresses within an element, with respect to the location of an external applied load are developed. This is mainly because the external loads are often of some freedom to change their application positions in the structural preliminary design. Apart from the structural response evaluation, the finite element method is employed in this work for the sensitivity analysis implementation of a plane stress continuum structure. First, an external load is transformed into the equivalent nodal forces such that the influence of an external load shift is represented completely by the magnitude variation of the associated nodal forces, upon which the first- and second-order derivatives of an external load to its location change are performed respectively in a closed form by the aid of the features of the element shape functions. Then, the relevant sensitivities of the structural responses aforementioned are formulated readily with the discrete method. Finally, two typical examples are provided to demonstrate the validity of the sensitivity formulations presented, and the numerical results show a perfect accuracy of calculation of the response sensitivity.
      PubDate: 2014-10-01
  • A confirmation of a conjecture on the existence of symmetric optimal
           solution under multiple loads
    • Abstract: Abstract In this note, a conjecture on the existence of symmetric optimal solution under multiple loads made in Rozvany (Struct Multidisc Optim 43:297–317, 2011, Conjecture 4) has been confirmed.
      PubDate: 2014-10-01
  • Structural topology optimization with constraints on multi-fastener joint
    • Abstract: Abstract This paper addresses an important problem of design constraints on fastener joint loads that are well recognized in the design of assembled aircraft structures. To avoid the failure of fastener joints, standard topology optimization is extended not only to minimize the structural compliance but also to control shear loads intensities over fasteners. It is shown that the underlying design scheme is to ameliorate the stiffness distribution over the structure in accordance with the control of load distributions over fastener joints. Typical examples are studied by means of topology optimization with joint load constraints and the standard compliance design. The effects of joint load constraints are highlighted by comparing numerical optimization results obtained by both methods. Meanwhile, resin models of optimized designs are fabricated by rapid prototyping process for loading test experiments to make sure the effectiveness of the proposed method.
      PubDate: 2014-10-01
  • Element deformation scaling for robust geometrically nonlinear analyses in
           topology optimization
    • Abstract: Abstract Geometrically nonlinear structural analyses in conventional density-based Topology Optimization (TO) may fail due to excessive deformation, concerning in particular compression in low stiffness parts (void) of the domain. This limits the application of TO in the field of realistic large deflection mechanisms, actuators and multi-stable structures. This paper investigates the source of the instabilities that may be encountered using the conventional strategy to scale the stiffness of finite elements using the density (e.g. SIMP). Based on the findings, we propose a new design interpolation, called Element Deformation Scaling (EDS), to obtain more robust structural analyses for geometrically nonlinear TO. Instead of scaling the stiffness, EDS scales the local internal displacements, and therefore, the deformation, in a low-density finite element. This ensures that, even for extremely deformed finite elements, the internal displacements remain in the range of applicability of the material model and finite element description. The effectiveness of the proposed method is compared with the conventional approach (e.g. SIMP) and the Element Connectivity Parameterization (ECP) method using several numerical experiments using path-following techniques. The proposed method, EDS, is demonstrated to lead to more robust structural analyses than the other approaches. However, EDS still has limitations. These limitations are discussed in detail.
      PubDate: 2014-10-01
  • Integrated optimization of the material and structure of composites based
           on the Heaviside penalization of discrete material model
    • Abstract: Abstract Based on discrete material optimization and topology optimization technologies, this paper discusses the problem of integrated optimization design of the material and structure of fiber-reinforced composites by considering the characteristics of the discrete variable of fiber ply angle because of the manufacture requirements. An optimization model based on the minimum structural compliance with a specified composite volume constraint is established. The ply angle and the distribution of the composite material are introduced as independent variables in two geometric scales (material and structural scales). The void material is added into the optional discrete material set to realize the topology change of the structure. This paper proposes an improved HPDMO (Heaviside Penalization of Discrete Material Optimization) model to obtain a better convergent result, and an explicit sensitivity analysis is performed. The effects of the HPDMO model on the convergence rate of the optimization results, the objective function value and the iteration history are studied and compared with those from the classical Discrete Material Optimization model and the Continuous Discrete Material Optimization model in this paper. Numerical examples in this paper show that the HPDMO model can effectively achieve the integrated optimization of the fiber ply angle and its distribution in the structural domain, and can also considerably improve the convergence rate of the optimal results compared with other DMO models. This model will help to reduce the manufacture cost of the optimal design.
      PubDate: 2014-09-30
  • Determination of back-pressure profile for forward extrusion using
           sequential approximate optimization
    • Abstract: Abstract This paper proposes a method for determining optimal back-pressure profile in forging of aluminum alloy using a sequential approximate optimization (SAO). In forging, it is important to improve the mold filling for the product quality. In addition, it is preferable to produce a product with a minimum forming energy. To achieve these objectives simultaneously, a forging method with back-pressure profile is proposed. Here, the back-pressure profile implies that the back-pressure varies through the stroke. In this paper, a multi-objective optimization (MOO) problem is formulated. To improve the mold filling, an unfilled area is taken as the first objective function. Furthermore, a forming energy during the forging is taken as the second objective function. Numerical simulation in the forging is so expensive that the SAO using the radial basis function (RBF) network is adopted, and the pareto-frontier is identified with a small number of simulation runs. Based on the numerical result, the experiments are also conducted. It can be found from these results that, the back-pressure profile approach is valid for improving the mold filling as well as the forming energy.
      PubDate: 2014-09-30
  • Introducing the sequential linear programming level-set method for
           topology optimization
    • Abstract: Abstract This paper introduces an approach to level-set topology optimization that can handle multiple constraints and simultaneously optimize non-level-set design variables. The key features of the new method are discretized boundary integrals to estimate function changes and the formulation of an optimization sub-problem to attain the velocity function. The sub-problem is solved using sequential linear programming (SLP) and the new method is called the SLP level-set method. The new approach is developed in the context of the Hamilton-Jacobi type level-set method, where shape derivatives are employed to optimize a structure represented by an implicit level-set function. This approach is sometimes referred to as the conventional level-set method. The SLP level-set method is demonstrated via a range of problems that include volume, compliance, eigenvalue and displacement constraints and simultaneous optimization of non-level-set design variables.
      PubDate: 2014-09-30
  • Interior value extrapolation: a new method for stress evaluation during
           topology optimization
    • Abstract: Abstract This article presents a new method for evaluating stresses in the jagged structures that arise when using a fixed finite element mesh to optimize the topology of a structure. The new method, Interior Value Extrapolation, IVE, exploits the fact that in the interior of the structure, the stresses calculated by the finite element method are more accurate than at the boundary. The jagged nature of the mesh makes stresses at the boundary oscillate. Therefore, stresses at the boundary are instead extrapolated from results in the interior, resulting in a more stable and accurate stress measure. A restriction method in the form of a non linear density filter is also proposed, tailored to be used in conjunction with the new stress evaluation method. The new method is evaluated for accuracy using example geometries, for which the stresses are known. It is shown that IVE improves the accuracy of the stress calculation. Optimization examples are thereafter solved with and without IVE, and the results are discussed. It is shown that the change in stress evaluation can in fact cause changes in the solution of a typical stress minimization problem.
      PubDate: 2014-09-28
  • Adjoint design sensitivity analysis of dynamic crack propagation using
           peridynamic theory
    • Abstract: Abstract Based on the peridynamics of the reformulated continuum theory, an adjoint design sensitivity analysis (DSA) method is developed for the solution of dynamic crack propagation problems using the explicit scheme of time integration. Non-shape DSA problems are considered for the dynamic crack propagation including the successive branching of cracks. The adjoint variable method is generally suitable for path-independent problems but employed in this bond-based peridynamics since its path is readily available. Since both original and adjoint systems possess time-reversal symmetry, the trajectories of systems are symmetric about the u-axis. We take advantage of the time-reversal symmetry for the efficient and concurrent computation of original and adjoint systems. Also, to improve the numerical efficiency of large scale problems, a parallel computation scheme is employed using a binary space decomposition method. The accuracy of analytical design sensitivity is verified by comparing it with the finite difference one. The finite difference method is susceptible to the amount of design perturbations and could result in inaccurate design sensitivity for highly nonlinear peridynamics problems with respect to the design. It is demonstrated that the peridynamic adjoint sensitivity involving history-dependent variables can be accurate only if the path of the adjoint response analysis is identical to that of the original response.
      PubDate: 2014-09-28
  • A note on optimal design of multiphase elastic structures
    • Abstract: Abstract The paper describes the first exact results in optimal design of three-phase elastic structures. Two isotropic materials, the “strong” and the “weak” one, are laid out with void in a given two-dimensional domain so that the compliance plus weight of a structure is minimized. As in the classical two-phase problem, the optimal layout of three phases is also determined on two levels: macro- and microscopic. On the macrolevel, the design domain is divided into several subdomains. Some are filled with pure phases, and others with their mixtures (composites). The main aim of the paper is to discuss the non-uniqueness of the optimal macroscopic multiphase distribution. This phenomenon does not occur in the two-phase problem, and in the three-phase design it arises only when the moduli of material isotropy of “strong” and “weak” phases are in certain relation.
      PubDate: 2014-09-17
  • Simultaneous parameter and tolerance optimization of structures via
           probability-interval mixed reliability model
    • Abstract: Abstract Both structural sizes and dimensional tolerances strongly influence the manufacturing cost and the functional performance of a practical product. This paper presents an optimization method to simultaneously find the optimal combination of structural sizes and dimensional tolerances. Based on a probability-interval mixed reliability model, the imprecision of design parameters is modeled as interval uncertainties fluctuating within allowable tolerance bounds. The optimization model is defined as to minimize the total manufacturing cost under mixed reliability index constraints, which are further transformed into their equivalent formulations by using the performance measure approach. The optimization problem is then solved with the sequential approximate programming. Meanwhile, a numerically stable algorithm based on the trust region method is proposed to efficiently update the target performance points (TPPs) and the worst case points (WCPs), which shows better performance than traditional approaches for highly nonlinear problems. Numerical results reveal that reasonable dimensions and tolerances can be suggested for the minimum manufacturing cost and a desirable structural safety.
      PubDate: 2014-09-16
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