BERT and Pareto dominance applied to biological strategy decision for bio-inspired design

Bio-inspired design (BID) approaches have provided numerous novel proposals for innovative design. Meanwhile, it resulted in an explosion of alternatives. Choosing a small amount of the personalized recommendations is becoming more and more difficult, and engineers may prefer fewer goals. Furthermore, engineers may choose designs that have variety and feasibility in BID. However, the diversity and feasibility of BID are often contradictory. Engineers need to apply multi-objective optimization methods to find better BID to ensure implementable. Aiming to overcome the above problems, based on the biological strategies from the most popular BID-AskNature, we proposed an interdisciplinary approach with the bidirectional encoder representation from transformers (BERT) and Pareto dominance for biological strategy decision (BPBSD) in the BID. First, we use BERT to find potential biological strategies similar to the keyword of BID. Then, aiming at the functional diversity and the feasibility of BID, we used the Pareto dominance theory to solve the contradiction. Finally, we verify the effectiveness of the proposed approach with three different application cases. Experiments show that the proposed BPBSD can balance the relationship between diversity and feasibility in BID. It is hoped that this work provides practical guidance for BID.     

A design model to predict optimal two-material composite structures

A method is presented for the prediction of optimal configurations for two-material composite continuum structures. In the model for this method, both local properties and topology for the stiffer of the two materials are to be predicted. The properties of the second, less stiff material are specified and remain fixed. At the start of the procedure for computational solution, material composition of the structure is represented as a pure mixture of the two materials. This design becomes modified in subsequent steps into a form comprised of a skeleton of concentrated stiffer material, together with a nonoverlapping distribution of the second material to fill the original domain. Computational solutions are presented for two example design problems. A comparison among solutions for different ratios of stiffness between the two materials gives an indication of how the distribution of concentrated stiffer material varies with this factor. An example is presented as well to show how the method can be used to predict an efficient layout for rib-reinforcement of a stamped sheet metal panel.     

Multilevel optimal design of composite structures including materials with negative Poisson's ratio

Multilevel iterative optimal design procedures, horrowed from the theory of structural optimization by means of homogenization, are used in this paper for the optimal material design of composite material structures. The method is quite general and includes materials with appropriate microstructure, which may lead eventually to phenomenological, overall negative Poisson's ratios. The benefits of optimal structural design gained by this approach, together with the first attempts to explain the taskoriented microstructure of natural structures, are investigated by means of numerical examples, and simulation of, among others, human bones.     

Effectiveness of optimal design with respect to computational models for laminated composite structures weakened by holes

The present work deals with the shape optimization of laminated structures via semianalytical sensitivity anslysis, based on linear programming. Particular attention is focused on the concise and correct finite element formulation of the problem taking into account explicit differentiation with respect to the control parameters. A series of numerical examples shows the influence of orthotropy parameters (treated as the level of anisotropy), stacking sequences, FE models and the employed 2-D plate theories of structures on the resulting optimal shapes.     

Automated selection of optimal material for pressurized multi-layer composite tubes based on an evolutionary approach

Decision making on the configuration of material layers as well as thickness of each layer in composite assemblies has long been recognized as an optimization problem. Today, on the one hand, abundance of industrial alloys with different material properties and costs facilitates fabrication of more economical or light weight assemblies. On the other hand, in the design stage, availability of different alternative materials apparently increases the complexity of the design optimization problem and arises the need for efficient optimization techniques. In the present study, the well-known big bang–big crunch optimization algorithm is reformulated for optimum design of internally pressurized tightly fitted multi-layer composite tubes with axially constrained ends. An automated material selection and thickness optimization approach is employed for both weight and cost minimization of one-, two-, and three-layer tubes, and the obtained results are compared. The numerical results indicate the efficiency of the proposed approach in practical optimum design of multi-layer composite tubes under internal pressure and quantify the optimality of different composite assemblies compared to one-layer tubes.

     

A new approach to optimal design of elastic structures

A new approach to the optimization of elastic trusses under stress constraints is discussed. The stress constraints are transformed into compliance constraints, which makes possible the derivation of a simple optimality condition. The condition provides a simple test to check whether a fully stressed design is optimal, for single as well as multiple loading conditions. It is readily extended to optimization problems, in which both stress and displacement constraints are imposed. An iterative routine, that is both simple and efficient, is derived from the optimality condition. Numerical examples of the application of the routine are presented.     

Interactive optimal design of truss structures

A CAD system based on combining structural optimization methods and graphical interaction is presented. The optimization methods implement the automated decisions and algorithms while the interaction provides the means to implement the designer's decisions. A new interactive optimization procedure for optimal truss design is proposed. The structural topology, geometry and member sizes are treated as design variables. Results show that the system provides a powerful tool to obtain a practical optimum design.     

Probabilistic optimal design of framed structures

Probabilistic structural design is a degree of difficulty greater than deterministic design and effectively is only tractable using a computer. This paper outlines one approach to the design of framed structures subject to random loading. In particular stochastic approximation is used iteratively to improve the value of the optimality criterion, leading to a guaranteed optimal solution in the limit. Two framed structures are used to illustrate the computations which are performed in conjunction with a random number generator to simulate the probabilistic aspects of the loading. The approach is independent of the probability model assumed for the loading. It is straightforward to implement and has good solution convergence characteristics.     

Variational sensitivity analysis of elastoplastic structures applied to optimal shape of specimens

Structural and Multidisciplinary Optimization - The aim of this paper is to improve the shape of specimens for biaxial experiments with respect to optimal stress states, characterized by the stress...     

Analysis and optimal design of layered structures subjected to impulsive loading

The attenuation of elastic stress waves propagating through layered structures situated between free and fixed surfaces is investigated. A stress transfer function, which relates the stress response at the fixed support to the applied stress pulse, is derived for several specific layered structures. An analysis of these responses indicate that when an incident stress pulse passes through a layered structure, a reduced stress amplitude and elongated pulse duration could be obtained with proper selection of materials and layer dimensions. Consequently, a design procedure is proposed to obtain the optimal layered structure, and several specific cases of layered structures are investigated.     

Parallel computing techniques applied to the simultaneous design of structure and material

In this work a computational procedure for two-scale topology optimization problem using parallel computing techniques is developed. The goal is to obtain simultaneously the best structure and material, minimizing structural compliance. An algorithmic strategy is presented in a suitable way for parallelization. In terms of parallel computing facilities, an IBM Cluster 1350 is used comprising 70 computing nodes each with two dual core processors, for a total of 280 cores. Scalability studies are performed with mechanical structures of low/moderate dimensions. Finally the applicability of the proposed methodology is demonstrated solving a grand challenge problem that is the simulation of trabecular bone adaptation.     

Reliability-based design optimization applied to structures submitted to random fatigue loads

Structural and Multidisciplinary Optimization - The reliability-based design optimization (RBDO) aims to find the most balanced design through a compromise between cost and safety when...     

Variable stiffness composite material design by using support vector regression assisted efficient global optimization method

In this work, a surrogate assisted optimization method is utilized to optimize buckling loads of variable stiffness composites made by fiber steering. To improve the efficiency of optimization procedure, an expected improvement criterion is employed. Moreover, considering uncertainties of the fiber placement, a robust surrogate, least square support vector regression (LSSVR) considering empirical and structural risks is integrated with the expected improvement (EI) criterion and applied to two applications. The first case is the fiber path design of a variable stiffness plate under the compression load. The second one is the fiber path design of a variable stiffness cylinder under the bending load. According to results of the optimization, the buckling load of the variable stiffness plate has 52.63% improvement than the constant stiffness plate and 24.3% improvement than the quasi-isotropic plate. The buckling load of the variable stiffness cylinder has 40.22% improvement than the constant stiffness cylinder and 31.25% improvement than the quasi-isotropic cylinder. Furthermore, to verify the robustness of optimal design variables for the variable stiffness cylinder, the perturbed optimum design is presented and demonstrates that the results are reliable.     

Analysis and optimum design of fibre-reinforced composite structures

The optimal design of a carbon-fibre-reinforced plastic (CFRP) sandwich-like structure with aluminium (Al) webs is addressed. The material parameters are determined using tensile tests, whereafter the results of an analytical model, a numerical model and an experimental setup are compared. The analytical and numerical approximations are then used to optimize the structure in a multi-algorithm approach for minimum cost and maximum stiffness. The selected algorithm and approximation are motivated by their accuracy and computational efficiency. The CFRP plates are optimized with respect to ply arrangement, while the complete sandwich-like structure is optimized with respect to the combination of manufacturing and material cost. Design constraints on maximum deflection of the total structure, buckling of the CFRP composite plates, buckling of the Al webs, stress in the composite plates and stress in the Al stiffeners are included in the formulation. For the different phases in the optimization process, we use the recently proposed particle swarm optimization algorithm, a dynamic search technique and a continuous-discrete optimization technique .     

The optimal design of structures using ACO and EFG

This paper presents an ant colony optimization (ACO) algorithm incorporating the element free Galerkin (EFG) method for topology optimization of continuum structures. The EFG method is used to derive shape functions using the moving least squares approximation. The essential boundary conditions are enforced by the Lagrange multiplier method. Several numerical examples are presented to show the validity and feasibly of the proposed method. The common numerical instabilities of the ACO algorithm do not exist in the results.     

Combined design of structures and controllers for optimal maneuverability

This paper treats the problem of the combined design of structure/control systems for achieving optimal maneuverability. A maneuverability index which directly reflects the time required to perform a given maneuver or set of maneuvers is introduced. By designing the flexible appendages of a spacecraft, its maneuverability is optimized under the constraints of structural properties, and of the postmaneuver spill-over being within a specified bound. The spillover reduction is achieved by making use of an appropriate control design model. The distributed parameter design problem is approached using assumed shape functions and finite element analysis with dynamic reduction. Characteristics of the problem and problem solving procedures have been investigated. Adaptive approximate design methods have been developed to overcome computational difficulties. It is shown that the global optimal design may be obtained by tuning the natural frequencies of the spacecraft to satisfy specific constraints. We quantify the difference between a lower bound to the objective function associated with the original problem and the estimate obtained from the modified problem as the index for the adaptive refinement procedure. Numerical examples show that the results of the optimal design can provide substantial improvement.     

Cross-section optimal design of composite laminated thin-walled beams

This paper aims to perform optimal design of cross-section properties of thin-walled laminated composite beams. These properties are expressed as integrals based on the cross-section geometry, on the warping functions for torsion, shear bending and shear warping, and on the individual stiffness of the laminates constituting the cross-section. The finite element method is used in discretizing the theory. For design sensitivity calculations, the cross-section is modelled throughout design elements. Geometrically, these elements may coincide with the laminates that constitute the cross-section. The developed formulation is based on the concept of adjoint structure. After a warping function is calculated for the cross-section, an adjoint problem may be formulated for each of the properties and a corresponding adjoint warping is determined. It can be applied in a unified way to open, closed or hybrid cross-sections. Design optimization is performed by nonlinear programming techniques. Laminate thickness and lamina orientations are considered as design variables.     

Optimal design of laminated composite beam structures

This work deals with design sensitivity analysis and optimal design of composite structures modelled as thin-walled beams. The structures are treated as a torsion-bending resistant beams. The analysis problem is discretized by a finite element technique. A two-node Hermitean beam element is used. The beam sections are made from an assembly of elements that correspond to flat layered laminated composite panels. Optimal design is performed with respect to the lamina orientations and thickness of the laminates. The structural weight is considered as the objective function. Constraints are imposed on stresses, displacements, critical load and natural frequencies. Two failure criteria are used to limit the structural strength: Tsai-Hill and maximum stress. The Tsai-Hill criterion is also adopted to predict the first-ply-failure loads. The design sensitivity analysis is analytically formulated and implemented. An adjoint variable method is used to derive the response sensitivities with respect to the design. A mathematical programming approach is used for the optimization process. Numerical examples are performed on three-dimensional structures.     

Finite topology variations in optimal design of structures

The method of optimal design of structures by finite topology modification is presented in the paper. This approach is similar to growth models of biological structures, but in the present case, topology modification is described by the finite variation of a topological parameter. The conditions for introducing topology modification and the method for determining finite values of topological parameters characterizing the modified structure are specified. The present approach is applied to the optimal design of truss, beam, and frame structures. For trusses, the heuristic algorithm of bar exchange is proposed for minimizing the global compliance subject to a material volume constraint and it is extended to volume minimization with stress and buckling constraints. The optimal design problem for beam and frame structures with elastic or rigid supports, aimed at minimizing the structure cost for a specified global compliance, is also considered.