A genetic algorithm with memory for optimal design of laminated sandwich composite panels

This paper is concerned with augmenting genetic algorithms (GAs) to include memory for continuous variables, and applying this to stacking sequence design of laminated sandwich composite panels that involves both discrete variables and a continuous design variable. The term “memory” implies preserving data from previously analyzed designs. A balanced binary tree with nodes corresponding to discrete designs renders efficient access to the memory. For those discrete designs that occur frequently, an evolving database of continuous variable values is used to construct a spline approximation to the fitness as a function of the single continuous variable. The approximation is then used to decide when to retrieve the fitness function value from the spline and when to do an exact analysis to add a new data point for the spline. With the spline approximation in place, it is also possible to use the best solution of the approximation as a local improvement during the optimization process. The demonstration problem chosen is the stacking sequence optimization of a sandwich plate with composite face sheets for weight minimization subject to strength and buckling constraints. Comparisons are made between the cases with and without the binary tree and spline interpolation added to a standard GA. Reduced computational cost and increased performance index of a GA with these changes are demonstrated.     

Multilevel optimization of space trusses using continuum modelling

A new concept of using continuum modelling in multilevel decomposition of structural optimization problems is presented. Its practicality is demonstrated by applying it to the optimization of large beam-like space structures. The results of the optimization scheme are tested against traditional optimization procedures for numerical accuracy and computational efficiency. Results from both optimization methods are presented for comparison.     

Wind load modeling for topology optimization of continuum structures

Topology optimization of two and three dimensional structures subject to dead and wind loading is considered. The wind loading is introduced into the formulation by using standard expressions for the drag force, and a strategy is devised so that wind pressure is ignored where there is no surface obstructing the wind. A minimum compliance design formulation is constructed subject to a volume constraint using the Solid Isotropic Material with Penalization model. The optimization problem is solved using the Method of Moving Asymptotes, modified by including a line search and by changing the formula for the update of asymptotes. To obtain black/white design, intermediate density values, which are used as design variables, are controlled by imposing an explicit constraint. Numerical examples of a windmill structure demonstrate that the proposed formulation rationally incorporates the effect of wind loading into the topology optimization problem as illustrated by void appearing in the optimal structure.     

Study of a new local update scheme for cellular automata in structural design

This paper investigates an improved local update scheme for cellular automata (CA) applied to structural design. Local analysis and design rules are derived for equilibrium and minimum compliance design. The new update scheme consists of repeating analysis and optimality-based design rules locally. The benefits of this approach are demonstrated through a series of systematic experiments. Truss topology design problems of various sizes are used based on the Gauss–Seidel and the Jacobi iteration modes. Experiments show the robust convergence of the approach as compared to an earlier CA implementation. The approach is also extended to a plate problem.     

New knowledge in strategic management through visually mining semantic networks

Today’s highly competitive business world requires that managers be able to make fast and accurate strategic decisions, as well as learn to adapt to new strategic challenges. This necessity calls for a deep experience and a dynamic understanding of strategic management. The trait of dynamic understanding is mainly the skill of generating additional knowledge and innovative solutions under the new environmental conditions. Building on the concepts of information processing, this paper aims to support managers in constructing new strategic management knowledge, through representing and mining existing knowledge through graph visualization. To this end, a three-stage framework is proposed and described. The framework can enable managers to develop a deeper understanding of the strategic management domain, and expand on existing knowledge through visual analysis. The model further supports a case study that involves unstructured knowledge of profit patterns and the related strategies to succeed using these patterns. The applicability of the framework is shown in the case study, where the unstructured knowledge in a strategic management book is first represented as a semantic network, and then visually mined for revealing new knowledge.     

Optimization of a composite cylinder under bending by tailoring stiffness properties in circumferential direction

A fiber-reinforced cylindrical shell with given geometry and material properties is optimized for maximum load-carrying capability under bending. The shell is assumed to be built using an advanced fiber-placement machine, which allows in-plane steering and overlapping of fibers, resulting in a so-called variable-stiffness shell. The design methodology for strength and stiffness variation in circumferential direction by means of fiber placement is explained and restrictions on the manufacturability are specified. Implementation in the commercially available finite element package ABAQUS^® for structural analysis is described. Subsequently, the cylinder is optimized to carry a maximum buckling load under bending, while applying a strength constraint. Constraints on the global stiffness are imposed by means of comparison with a baseline quasi-isotropic shell, while a matrix dominated lay up is avoided at all locations in the laminate in order to ensure that the laminate is strong enough in all directions in case a hole is present. Optimization is done using a surrogate model in order to minimize the amount of finite element analyses. Improvements of up to 17% are obtained by changing the load path. The tension side is made stiffer and the compression side softer in longitudinal direction by changing the fiber orientation from near zero at the upper (tension) side to higher fiber angles at the lower (compression) side, such that load is relieved from the compression side. This results in a higher load-carrying capability of the cylinder.     

Circumferential stiffness tailoring of general cross section cylinders for maximum buckling load with strength constraints

Stiffness tailoring of laminated composite structures using steered fibre tows is a design method that maximally uses the directional properties of composite materials. Cylindrical structures usually have circular cross sections while some application, geometric or aerodynamic requirements can necessitate other cross sections, e.g. elliptical. Circumferential tailoring can increase the buckling load of thin cylinders by compensating for non-uniform sectional loading such as bending and/or varying radius of curvature in general cylinders. Here, strength constraints are considered in maximum buckling load design, to ensure that the failure load is greater than the buckling load. A two-step optimisation framework is used to separate the theoretical and manufacturing issues in design. A computationally cheap semi-analytical finite difference method is used to solve the linear static and buckling problems. Conservative failure envelopes based on Tsai-Wu failure criterion are used for strength evaluation. To avoid repetitive analyses, successive convex approximation method is used. For demonstration, circumferential tailoring framework is applied to a circular cylinder under bending and an elliptical cylinder under axial compression. The improvements in buckling capacity of variable over constant stiffness designs are shown and verified using nonlinear buckling analysis in the commercial FEM software Abaqus^TM, and the mechanisms of improvements are investigated.     

Experimental zones: two cases of exploring frames of participation in a dialogic museum

Abstract

A matter of concern for dialogic institutions such as museums is the struggle to find appropriate ways of integrating social media and digital technologies into dialogues with visitors. This paper addresses how co-creation and experimental methods may be applied in a situated, natural environment, exploring how these technologies may be shaped to support museum visitor relations. The concept ‘experimental zone’ is suggested as a format for a collaborative design space where digital media-based dialogues are explored in line with professional practices. This concept is discussed in relation to two design experiments undertaken in collaboration with the Norwegian Museum of Science and Technology.     

Matters of becoming,experimental zones for making museums public with social media

Making things public challenges existing matters of concern and, in design, may also be about changing them. This paper advances the concept of translation from early ANT literature and explores it in order to support co-designing for making things public. We elaborate on how translations may be understood as moves and transformations of practices and objects that require both time and learning. We discuss how translations may include the emerging, situated, fluid, enacted, experiential and the material, and suggest co-design to rethink translation as a temporal process of learning and ‘becoming’. Our aim is to demonstrate a mutual theoretical influence between ANT and co-design. Our conceptual reflection is based on a museum design case where museum staff and the authors explore new communicational modes of social media. The project established a longitudinal ‘experimental zone’ as space and time for design in the everyday practice of the museum. The paper reflects upon the value of ANT as a framework for rethinking the design–use divide using concepts of learning and translations to bring awareness of co-design as temporal, fluid and emerging processes of becoming.