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  Subjects -> ENGINEERING (Total: 2096 journals)
    - CHEMICAL ENGINEERING (176 journals)
    - CIVIL ENGINEERING (161 journals)
    - ELECTRICAL ENGINEERING (88 journals)
    - ENGINEERING (1157 journals)
    - ENGINEERING MECHANICS AND MATERIALS (330 journals)
    - HYDRAULIC ENGINEERING (53 journals)
    - INDUSTRIAL ENGINEERING (52 journals)
    - MECHANICAL ENGINEERING (79 journals)

CIVIL ENGINEERING (161 journals)                  1 2     

ACI Structural Journal     Full-text available via subscription   (Followers: 8)
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: 30)
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: 20)
Architectural Engineering     Open Access   (Followers: 3)
Archives of Civil Engineering     Open Access   (Followers: 8)
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: 5)
Baltic Journal of Road and Bridge Engineering     Full-text available via subscription   (Followers: 2)
BER : Building and Construction : Full Survey     Full-text available via subscription   (Followers: 9)
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: 14)
Canadian Journal of Civil Engineering     Full-text available via subscription   (Followers: 14)
Case Studies in Engineering Failure Analysis     Open Access   (Followers: 4)
Cement and Concrete Composites     Hybrid Journal   (Followers: 9)
Change Over Time     Full-text available via subscription   (Followers: 3)
Civil and Environmental Research     Open Access   (Followers: 13)
Civil Engineering     Hybrid Journal   (Followers: 11)
Civil Engineering = Siviele Ingenieurswese     Full-text available via subscription   (Followers: 5)
Civil Engineering and Architecture     Open Access   (Followers: 3)
Civil Engineering and Environmental Systems     Hybrid Journal   (Followers: 5)
Civil Engineering and Technology     Open Access   (Followers: 4)
Civil Engineering Dimension     Open Access   (Followers: 4)
Cohesion and Structure     Full-text available via subscription   (Followers: 2)
Composite Structures     Hybrid Journal   (Followers: 74)
Computer-aided Civil and Infrastructure Engineering     Hybrid Journal   (Followers: 9)
Computers & Structures     Hybrid Journal   (Followers: 26)
Concrete Research Letters     Open Access   (Followers: 2)
Constructii : Journal of Civil Engineering Research     Open Access   (Followers: 9)
Construction Engineering     Open Access   (Followers: 3)
Construction Management and Economics     Hybrid Journal   (Followers: 29)
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: 14)
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: 4)
Fatigue & Fracture of Engineering Materials and Structures     Hybrid Journal   (Followers: 14)
Frattura ed Integrità Strutturale : Fracture and Structural Integrity     Open Access   (Followers: 1)
Frontiers of Structural and Civil Engineering     Hybrid Journal   (Followers: 5)
Geomaterials     Open Access   (Followers: 2)
Geosystem Engineering     Hybrid Journal   (Followers: 3)
Geotechnik     Hybrid Journal   (Followers: 1)
Géotechnique Letters     Hybrid Journal   (Followers: 4)
HBRC Journal     Open Access   (Followers: 2)
HVAC&R Research     Hybrid Journal   (Followers: 1)
Indoor and Built Environment     Hybrid Journal   (Followers: 1)
Infrastructure Asset Management     Full-text available via subscription  
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: 6)
International Journal of Construction Engineering and Management     Open Access   (Followers: 3)
International Journal of Geosynthetics and Ground Engineering     Full-text available via subscription  
International Journal of Protective Structures     Full-text available via subscription   (Followers: 6)
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)
International Journal on Pavement Engineering & Asphalt Technology     Open Access   (Followers: 1)
ISRN Civil Engineering     Open Access   (Followers: 4)
ISRN Power Engineering     Open Access   (Followers: 1)
Journal of Accessibility and Design for All     Open Access   (Followers: 6)
Journal of Advanced Research in Civil and Environmental Engineering     Open Access   (Followers: 1)
Journal of Applied Fire Science     Full-text available via subscription   (Followers: 3)
Journal of Bridge Engineering     Full-text available via subscription   (Followers: 15)
Journal of Building Materials and Structures     Open Access  
Journal of Building Performance Simulation     Hybrid Journal   (Followers: 5)
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: 12)
Journal of Civil Engineering Research     Open Access   (Followers: 11)
Journal of Civil Society     Hybrid Journal   (Followers: 2)
Journal of Civil Structural Health Monitoring     Hybrid Journal   (Followers: 2)
Journal of Composites     Open Access   (Followers: 17)
Journal of Composites for Construction     Full-text available via subscription   (Followers: 10)
Journal of Computing in Civil Engineering     Full-text available via subscription   (Followers: 20)
Journal of Construction Engineering     Open Access   (Followers: 4)
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: 8)

        1 2     

Journal Cover   Structural and Multidisciplinary Optimization
  [SJR: 1.825]   [H-I: 61]   [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  [2302 journals]
  • Level set topology optimization of stationary fluid-structure interaction
           problems
    • Abstract: Abstract This paper introduces a topology optimization approach that combines an explicit level set method (LSM) and the extended finite element method (XFEM) for designing the internal structural layout of fluid-structure interaction (FSI) problems. The FSI response is predicted by a monolithic solver that couples an incompressible Navier-Stokes flow model with a small-deformation solid model. The fluid mesh is modeled as an elastic continuum that deforms with the structure. The fluid model is discretized with stabilized finite elements and the structural model by a generalized formulation of the XFEM. The nodal parameters of the discretized level set field are defined as explicit functions of the optimization variables. The optimization problem is solved by a nonlinear programming method. The LSM-XFEM approach is studied for two- and three-dimensional FSI problems at steady-state and compared against a density topology optimization approach. The numerical examples illustrate that the LSM-XFEM approach convergences to well-defined geometries even on coarse meshes, regardless of the choice of objective and constraints. In contrast, the density method requires refined grids and a mass penalization to yield smooth and crisp designs. The numerical studies show that the LSM-XFEM approach can suffer from a discontinuous evolution of the design in the optimization process as thin structural members disconnect. This issue is caused by the interpolation of the level set field and the inability to represent particular geometric configurations in the XFEM model. While this deficiency is generic to the LSM-XFEM approach used here, it is pronounced by the nonlinear response of FSI problems.
      PubDate: 2015-03-17
       
  • Thickness filters for gradient based multi-material and thickness
           optimization of laminated composite structures
    • Abstract: Abstract This paper presents a new gradient based method for performing discrete material and thickness optimization of laminated composite structures. The novelty in the new method lies in the application of so-called casting constraints, or thickness filters in this context, to control the thickness variation throughout the laminate. The filters replace the layerwise density variables with a single continuous through-the-thickness design variable. Consequently, the filters eliminate the need for having explicit constraints for preventing intermediate void through the thickness of the laminate. Therefore, the filters reduce both the number of constraints and design variables in the optimization problem. Based upon a continuous approximation of a unit step function, the thickness filters are capable of projecting discrete 0/1 values to the underlying layerwise or ”physical” density variables which govern the presence of material in each layer through the thickness of the laminate. Combined with an in-plane density filter, the method enables manufacturers to control the length scale of the geometry while obtaining near discrete designs. Together with the applied manufacturing constraints it is now possible for manufacturers to steer the design towards a higher level of manufacturability. The method is demonstrated for mass minimization with displacement and manufacturing constraints. The results show that the method indeed is capable of obtaining near discrete designs which obey the governing constraints.
      PubDate: 2015-03-13
       
  • Development of a widely applicable gradientless shape optimization based
           bone adaptation model for comparative parametric studies
    • Abstract: Abstract Many gradientless optimization based methods have been developed to predict mechanically-driven strength adaptations of bone and to improve the failure resistance of inert mechanical components. However, because the gradientless optimization methods commonly used in these applications typically do not result in a unique solution, few are capable of providing quantitative comparisons of the effects of different boundary conditions on the resulting shape and strength changes of the objects studied. Driven by relative measures of the current local stress state, global stress state, and variation of the local stress state over the design region, a condition-independent, system-independent shape/strength adaptation model was developed that can be applicable to a system with a large number of design variables. Using a local extrema independent quantitative measure of the progression of the design region to a more uniform stress state, a consistent comparison point was defined that can be used regardless of the system studied, the boundary conditions applied, or the initial amount of stress variation. The implementation of the developed model demonstrated its effectiveness in the repeatable prediction of shape and strength changes over multiple orders of magnitude differences in boundary values with no changes to the modeling parameters or stopping criteria. The developed gradientless optimization based shape adaptation technique can be a useful tool in the comparison of the effects of various loading conditions on the strength changes in bones and in the creation of exercise regimens to strengthen fracture prone regions.
      PubDate: 2015-03-11
       
  • Design optimization of a runflat structure based on multi-objective
           genetic algorithm
    • Abstract: Abstract Runflat structure plays an important role in determining the sustainable mileage after the tire is shot. Lightweight, stiffness and strength are highly relevant to the overall performance of the structure. A parameterized model was built based on the full study of the structure, and a new adaptive meshing method is proposed to ensure the quality of the model. The accuracy of the new model was verified by comparing to the traditional finite element model. The parameter study was carried out to investigate the response of the performance and mass. Multi-objective optimization model was established by applying optimal Latin square design method and response surface model approach. Non-dominated sorting genetic algorithm-II (NSGA-II) was applied to obtain the optimization design. The results indicate that the combination of parameterized model and multi-objective genetic algorithms successfully achieve the goal of multi-objective optimization for mass and displacement while ensuring the stress. Meanwhile, the optimal topology, shape and thickness optimization for the runflat structure have been achieved at the same time.
      PubDate: 2015-03-11
       
  • A software development framework for structural optimization considering
           non linear static responses
    • Abstract: Abstract In the real world, structural systems may not have linear static characteristics. However, structural optimization has been developed based on static responses because sensitivity analysis regarding static finite element analysis is developed quite well. Analyses other than static analysis are heavily required in the engineering community these days. Techniques for such analyses have been extensively developed and many software systems using the finite element method are easily available in the market. On the other hand, development of structural optimization using such analyses is fairly slow due to many obstacles. One obstacle is that it is very difficult and expensive to consider the nonlinearities or dynamic effects in the way of conventional optimization. Recently, the equivalent static loads method for non linear static response structural optimization (ESLSO) has been proposed for structural optimization with various responses: linear dynamic response, nonlinear static response, and nonlinear dynamic response. In ESLSO, finite element analysis other than static analysis is performed, equivalent static loads (ESLs) are generated, linear static response structural optimization is carried out with the ESLs and the process iterates. A software system for the automatic use of ESLSO is developed and described. One of the advantages of ESLSO is that it can use well developed commercial software systems for structural analysis and linear static response structural optimization. Various analysis and optimization systems are integrated in the developed system. The structure of the system is systematically defined and the software is developed by the C++ language on the Windows operating system.
      PubDate: 2015-03-10
       
  • Global blending optimization of laminated composites with discrete
           material candidate selection and thickness variation
    • Abstract: Abstract A method capable of simultaneous topology and thickness optimization of laminated composites has previously been published by one of the authors. Mass constrained compliance minimization subject to certain manufacturing constraints was solved on basis of interpolation schemes with penalization. In order to obtain large patchwise material candidate continuity while also accommodating variable laminate thickness, a bi-linear stiffness parameterization was introduced, causing a non-convex problem. In this present work, we introduce an alternative problem formulation that holds identical capabilities but is, however, convex in the original mixed binary nested form. Convexity is the foremost important property of optimization problems, and the proposed method can guarantee the global or near-global optimal solution; unlike most topology optimization methods. The material selection is limited to a distinct choice among predefined numbers of candidates. The laminate thickness is variable but the number of plies must be integer. We solve the convex mixed binary non-linear programming problem by an outer approximation cutting-plane method augmented with a few heuristics to accelerate the convergence rate. The capabilities of the method and the effect of active versus inactive manufacturing constraints are demonstrated on several numerical examples of limited size, involving at most 320 binary variables. Most examples are solved to guaranteed global optimality and may constitute benchmark examples for popular topology optimization methods and heuristics based on solving sequences of non-convex problems. The results will among others demonstrate that the difficulty of the posed problem is highly dependent upon the composition of the constitutive properties of the material candidates.
      PubDate: 2015-03-10
       
  • A survey on handling computationally expensive multiobjective optimization
           problems using surrogates: non-nature inspired methods
    • Abstract: Abstract Computationally expensive multiobjective optimization problems arise, e.g. in many engineering applications, where several conflicting objectives are to be optimized simultaneously while satisfying constraints. In many cases, the lack of explicit mathematical formulas of the objectives and constraints may necessitate conducting computationally expensive and time-consuming experiments and/or simulations. As another challenge, these problems may have either convex or nonconvex or even disconnected Pareto frontier consisting of Pareto optimal solutions. Because of the existence of many such solutions, typically, a decision maker is required to select the most preferred one. In order to deal with the high computational cost, surrogate-based methods are commonly used in the literature. This paper surveys surrogate-based methods proposed in the literature, where the methods are independent of the underlying optimization algorithm and mitigate the computational burden to capture different types of Pareto frontiers. The methods considered are classified, discussed and then compared. These methods are divided into two frameworks: the sequential and the adaptive frameworks. Based on the comparison, we recommend the adaptive framework to tackle the aforementioned challenges.
      PubDate: 2015-03-10
       
  • Structural design of a level-luffing crane through trajectory optimization
           and strength-based size optimization
    • Abstract: Abstract The present study explores the trajectory optimization of a double-rocker four-bar mechanism to minimize the amplitude of its trajectory. A numerical model of the levelluffing crane (LLC) is first developed to describe the trajectory mechanism, and the optimal trajectory is then identified after selecting dominant design variables in the context of design of experiments. The numerical optimization solution obtained is compared with measured data. The optimized trajectory design is then applied to the strengthbased deterministic optimization (DO) to minimize the weight of a double-rocker structure under the constraints of stress and deflection. To carry out approximate optimization, a response surface method based on a second-order polynomial is used. Due to the existence of design uncertainties in an actual environment, reliability based design optimization (RBDO) is explored to assess the probabilities of failure in stress and deflection. For the design safety, DO and RBDO solutions are evaluated under severe loading conditions.
      PubDate: 2015-02-01
       
  • A Multi-point constraints based integrated layout and topology
           optimization design of multi-component systems
    • Abstract: Abstract The integrated layout and topology optimization is to find proper layout of movable components and topology patterns of their supporting structures, where two kinds of design variables, i.e. the structural pseudo-densities and the components’ locations are optimized simultaneously. The purpose of this paper is to demonstrate a new multi-point constraints (MPC) based method where the rivets or bolts connections between the components and their supporting structures are introduced. The displacement consistence involved in the MPC is strictly maintained which makes the components to carry the loads together with the supporting structures. Moreover, more benefits like avoidance of finite element remeshing and precise geometry of the components can be obtained. In particular, sensitivities with respect to the components’ locations can be analytically and efficiently achieved by deriving the MPC equations. Finally, several numerical examples are tested and discussed to demonstrate the validity of the proposed method.
      PubDate: 2015-02-01
       
  • Convex topology optimization for hyperelastic trusses based on the
           ground-structure approach
    • Abstract: Abstract Most papers in the literature, which deal with topology optimization of trusses using the ground structure approach, are constrained to linear behavior. Here we address the problem considering material nonlinear behavior. More specifically, we concentrate on hyperelastic models, such as the ones by Hencky, Saint-Venant, Neo-Hookean and Ogden. A unified approach is adopted using the total potential energy concept, i.e., the total potential is used both in the objective function of the optimization problem and also to obtain the equilibrium solution. We proof that the optimization formulation is convex provided that the specific strain energy is strictly convex. Some representative examples are given to demonstrate the features of each model. We conclude by exploring the role of nonlinearities in the overall topology design problem.
      PubDate: 2015-02-01
       
  • Development and validation of a dynamic metamodel based on stochastic
           radial basis functions and uncertainty quantification
    • Abstract: Abstract A dynamic radial basis function (DRBF) metamodel is derived and validated, based on stochastic RBF and uncertainty quantification (UQ). A metric for assessing metamodel efficiency is developed and used. The validation includes comparisons with a dynamic implementation of Kriging (DKG) and static metamodels for both deterministic test functions (with dimensionality ranging from two to six) and industrial UQ problems with analytical and numerical benchmarks, respectively. DRBF extends standard RBF using stochastic kernel functions defined by an uncertain tuning parameter whose distribution is arbitrary and whose effects on the prediction are determined using UQ methods. Auto-tuning based on curvature, adaptive sampling based on prediction uncertainty, parallel infill, and multiple response criteria are used. Industrial problems are two UQ applications in ship hydrodynamics using high-fidelity computational fluid dynamics for the high-speed Delft catamaran with stochastic operating and environmental conditions: (1) calm water resistance, sinkage and trim with variable Froude number; and (2) mean value and root mean square of resistance and heave and pitch motions with variable regular head wave. The number of high-fidelity evaluations required to achieve prescribed error levels is considered as the efficiency metric, focusing on fitting accuracy and UQ variables. DKG is found more efficient for fitting low-dimensional test functions and one-dimensional UQ, whereas DRBF has a greater efficiency for fitting higher-dimensional test functions and two-dimensional UQ.
      PubDate: 2015-02-01
       
  • Conceptual and detailed design of an automotive engine cradle by using
           topology, shape, and size optimization
    • Abstract: Abstract An automotive engine cradle supports many crucial components and systems, such as an engine, transmission, and suspension. Important performance measures for the design of an engine cradle include stiffness, natural frequency, and durability, while minimizing weight is of primary concern. This paper presents an effective and efficient methodology for engine cradle design from conceptual design to detailed design using design optimization. First, topology optimization was applied on a solid model which only contains the possible engine cradle design space, and an optimum conceptual design was determined which minimizes weight while satisfying all stiffness constraints. Based on topology optimization results, a design review was conducted, and a revised model was created which addresses all structural and manufacturability concerns. Shape and size optimization was then performed in the detailed design stage to further minimize the mass while meeting the stiffness and natural frequency targets. Lastly, the final design was validated for durability. The initial design domain had the mass of 82.6 kg; topology optimization in conceptual design reduced the mass to 26.7 kg; and the detailed design task involving shape and size optimization further reduced the mass to 21.4 kg.
      PubDate: 2015-02-01
       
  • Thermo-structural optimization of integrated thermal protection panels
           with one-layer and two-layer corrugated cores based on simulated annealing
           algorithm
    • Abstract: Abstract Toexplore weight saving potential capability, a multidisciplinary optimization procedure based on simulated annealing algorithm was proposed to unveil the minimum weight design for integrated thermal protection system subjected to in-service thermal and mechanical loads. The panel configurations with one-layer and two-layer corrugated cores are considered for comparison. Heat transfer and structural field analysis for each panel configuration were performed to obtain the temperature, buckling, stress and deflection responses for structural components of interest, which were then considered as critical constraints of the optimization problem. Sensitivity analysis was performed to disclose the effect of individual design variables on the thermo-structural extreme responses, and the designed thermal protection system performance and weight for the two configurations were discussed. The results demonstrated that the two-layer structure provides superior structural efficiency and performance to resist thermal buckling deformation in comparison with the one-layer panel. Its area-specific weight is reduced by more than 14–29 % with respect to the one-layer panel design, and 30–50 % weight efficient can be implemented at higher thermal buckling constraint levels, while keeping considerable temperature, stress and deflection margins.
      PubDate: 2015-02-01
       
  • Isogeometric configuration design optimization of built-up structures
    • Abstract: Abstract We derive the isogeometric configuration sensitivity of the Mindlin plates by using the material derivative and adjoint approaches. This is utilized in the shape design optimization that includes a variation of design components in its shape and orientation. By the isogeometric approach, the NURBS basis function in CAD system is directly utilized in the response analysis, which enables the seamless incorporation of higher continuity and exact geometry such as curvature and normal vector into the computational framework. The impact of exact curvature in the bending problem of Mindlin plates on the configuration design sensitivity is demonstrated through numerical examples. The obtained design sensitivity is further utilized in the shape design optimization of built-up structures. Due to the non-interpolatory property of the NURBS basis functions, a mismatch of patches in the built-up structures could occur during the isogeometric design optimization, which can be easily resolved using transformed basis functions.
      PubDate: 2015-02-01
       
  • Reduction of calibration effort in FEM-based optimization via numerical
           and experimental data fusion
    • Abstract: Abstract In this paper a fusion metamodeling approach is suggested as a method for reducing the experimental and computational effort generally required for calibrating the parameters of FEM simulations models. The metamodel is used inside an optimization routine for linking data coming from two different sources: simulations and experiments. The method is applied to a real problem: the optimal design of a metal foam filled tube to be used as an anti-intrusion bar in vehicles. The model is hierarchical, in the sense that one set of data (the experiments) is considered to be more reliable and it is labeled as “high-fidelity” and the other set (the simulations) is labeled as “low-fidelity”. In the proposed approach, Gaussian models are used to describe results of computer experiments because they are flexible and they can easily interpolate data coming from deterministic simulations. Since the results of experiments are obviously fully accurate, but aleatory, a second stage (“linkage”) model is used, which adjusts the prediction provided by the first model to more accurately represent the real experimental data. In the paper, the modeling and prediction ability of the method is first demonstrated and explained by means of artificially generated data and then applied to the optimization of foam filled tubular structures. The fusion metamodel yields comparable predictions (and optimal solution) if built over calibrated simulations vs. non-calibrated FEM models.
      PubDate: 2015-02-01
       
  • A semidefinite programming approach to robust truss topology optimization
           under uncertainty in locations of nodes
    • Abstract: Abstract This paper addresses truss topology optimization taking into account robustness to uncertainty in the truss geometry. Specifically, the locations of nodes are assumed not to be known precisely and the compliance in the worst case is attempted to be minimized. We formulate a semidefinite programming problem that serves as a safe approximation of this robust optimization problem. That is, any feasible solution of the presented semidefinite programming problem satisfies the constraints of the original robust optimization problem. Since a semidefinite programming problem can be solved efficiently with a primal-dual interior-point method, we can find a robust truss design efficiently with the proposed semidefinite programming approach. A notable property of the proposed approach is that the obtained truss is guaranteed to be stable. Numerical experiments are performed to illustrate that the optimal truss topology depends on the magnitude of uncertainty.
      PubDate: 2015-02-01
       
  • Finite strain topology optimization based on phase-field regularization
    • Abstract: Abstract In this paper the topology optimization problem is solved in a finite strain setting using a polyconvex hyperelastic material. Since finite strains is considered the definition of the stiffness is not unique. In the present contribution, the objective of the optimization is minimization of the end-displacement for a given amount of material. The problem is regularized using the phase-field approach which leads to that the optimality criterion is defined by a second order partial differential equation. Both the elastic boundary value problem and the optimality criterion is solved using the finite element method. To approach the optimal state a steepest descent approach is utilized. The interfaces between void and full material are resolved using an adaptive finite element scheme. The paper is closed by numerical examples that clearly illustrates that the presented method is able to find optimal solutions for finite strain topology optimization problems.
      PubDate: 2015-02-01
       
  • Reliability-based design optimization for vehicle occupant protection
           system based on ensemble of metamodels
    • Abstract: Abstract An Occupant Protection System (OPS) has very important applications in an automobile accident, which can save an occupant from fateful hurt or death. To provide a feasible framework for decreasing occupant injury degree, this paper presents a practical approach of the Reliability-based Design Optimization (RBDO) for vehicle OPS performance development based on the ensemble of metamodels. The weight factors of the ensemble associated with each metamodel are determined using a heuristic method. The comparative result shows that the prediction accuracies of the ensemble of metamodels exceed all individual one. Generally, the deterministic optimum designs without considering the uncertainty of design variables frequently push design constraints to the limit of boundaries and lead objective performance variation to largely fluctuate. So, the RBDO is presented and aims to maintain design feasibility at a desired reliability level. The First Order Reliability Method (FORM) and Second Order Reliability Method (SORM) are used to calculate the reliability index, and the results are checked by Monte Carlo (MC) simulation respectively, from which the failure probability of the OPS performance design is obtained. The result demonstrates that the reliability design is more reliable than the deterministic optimization in real engineering application. Finally, the reliability-based design optimization result is validated by the simulation result, which shows that the proposed RBDO approach is very effective in obtaining an optimum design.
      PubDate: 2015-02-01
       
  • A numerical form-finding method for the minimal surface of membrane
           structures
    • Abstract: Abstract This paper proposes a convenient numerical form-finding method for designing the minimal surface, or the equally tensioned surface of membrane structures with specified arbitrary boundaries. Area minimization problems are formulated as a distributed-parameter shape optimization problem. The internal volume or the perimeter is added as a constraint according to the structure type such as a pneumatic or a suspension membrane. It is assumed that the membrane is varied in the out-of-plane and/or the in-plane direction to the surface. The shape sensitivity function for each problem is derived using the material derivative method. The minimal surface is determined without shape parameterization by the free-form optimization method, a gradient method in the Hilbert space, where the shape is varied by the traction force in proportion to the sensitivity function under the Robin boundary condition. The calculated results show the effectiveness and practical utility of the proposed method for optimal form-finding of membrane structures.
      PubDate: 2015-02-01
       
  • Driving force profile design in comb drive electrostatic actuators using a
           level set-based shape optimization method
    • Abstract: Abstract Electrostatic actuators, actuators actuated by electrostatic forces, are now widely used as sensors and switches, especially in Micro-Electro-Mechanical Systems (MEMS). Among different kinds of electrostatic actuators, the comb drive type is one of the most popular because it has a relatively large range of displacement. In design problems for electrostatic actuators, the driving force profile is of primary engineering importance. In this paper, we develop a structural optimization method for comb drive electrostatic actuators that achieves prescribed driving force profiles, based on a level set-based shape optimization method that provides optimal configurations with clear boundaries, solutions that are valid in an engineering sense. Accurate calculation of the electrostatic forces that occur on the structural boundaries during optimization is important for developing actuators that operate with prescribed driving forces. In the conventional level set-based shape optimization methods, inaccuracies in the calculation of these electrostatic forces occur because the structural boundaries are seldom aligned with the finite element method (FEM) nodes. To precisely calculate the electrostatic forces, we developed a mesh adaptation scheme by which the finite element nodes are brought into alignment with the structural boundaries at every iteration of the optimization procedure. In the following, we explain the details of the proposed level set-based shape optimization method, in which a multi-objective optimization problem is formulated to achieve a prescribed driving force profile. The sensitivity is derived using the adjoint variable method. Four numerical examples are provided, to examine the suitability of the proposed optimization method.
      PubDate: 2015-02-01
       
 
 
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