变体机翼大变形梯形蒙皮结构研究

首先介绍了变体机翼及蒙皮结构的发展研究现状,提出了大变形梯形蒙皮结构的构想.随后,建立了梯形蒙皮结构的力学分析数学模型,与有限元仿真分析结果进行了比较和分析,验证了所建立数学分析模型的正确性,为进一步开展制备和实验研究奠定了理论基础.     

A Study of Bistable Laminates of Generic Lay‐Up for Adaptive Structures

Abstract: Asymmetric laminates are known to exhibit two stable cylindrical states and one unstable saddle state. Such bistability has attracted attention in aerospace applications because of the potential low energy requirement to achieve a large deflection or change in shape. This paper presents experimental observations of a generic asymmetric [?30/60] laminate with and without piezoelectric actuation and compares against both energy‐based analytical and finite element (FE) models. It is observed that the analytical model offers a qualitative understanding of bistable behaviour, degree of curvature and overall shape but is unable to model the distinctive curvature changes near the boundaries which can be captured by the FE model. The investigation also presents the use of piezoelectric actuation to achieve snap‐through in both analytical and FE models, which is compared and validated with experimental characterisation.     

Shape morphing of laminated composite structures with photostrictive actuators via topology optimization

In this paper, a new design method is presented for achieving remote wireless shape morphing of laminated composite structures using topology optimization methods. A recently emerging family of smart materials, photostrictive materials, is introduced as the actuation discipline to implement the active control of optical structures by utilizing the photostriction mechanism, which arises from the superposition of photovoltaic effect and converse piezoelectric effect when exposed to the illumination of near ultraviolet light. In terms of the Mindlin plate theory of first-order shear deformation, a finite element formulation including multiphysics effects of photovoltaic, pyroelectric and thermal expansion is developed to model composite structures of ferroelectric materials polarized in 0–1 and 0–3 directions, respectively. The design is formulated as a multi-constrained optimization problem with a least square objective function to minimize structural shape errors. The topology optimization method is used as a systematic design approach to seek the optimal topologies of material layouts for both the photostrictive and host layers as well as the actuator light distribution. In terms of design sensitivity analysis, many gradient-based optimization algorithms can be applied to solve the problem effectively. Numerical examples are presented to demonstrate the effectiveness of this method in the field of active photonic control of laminated composite structures.     

Topology and sizing optimization of discrete structures using a cooperative coevolutionary genetic algorithm with independent ground structures

This article proposes a method called the cooperative coevolutionary genetic algorithm with independent ground structures (CCGA-IGS) for the simultaneous topology and sizing optimization of discrete structures. An IGS strategy is proposed to enhance the flexibility of the optimization by offering two separate design spaces and to improve the efficiency of the algorithm by reducing the search space. The CCGA is introduced to divide a complex problem into two smaller subspaces: the topological and sizing variables are assigned into two subpopulations which evolve in isolation but collaborate in fitness evaluations. Five different methods were implemented on 2D and 3D numeric examples to test the performance of the algorithms. The results demonstrate that the performance of the algorithms is improved in terms of accuracy and convergence speed with the IGS strategy, and the CCGA converges faster than the traditional GA without loss of accuracy.     

The universal scissor component: Optimization of a reconfigurable component for deployable scissor structures

Deployable scissor structures are well equipped for temporary and mobile applications since they are able to change their form and functionality. They are structural mechanisms that transform from a compact state to an expanded, fully deployed configuration. A barrier to the current design and reuse of scissor structures, however, is that they are traditionally designed for a single purpose. Alternatively, a universal scissor component (USC)—a generalized element which can achieve all traditional scissor types—introduces an opportunity for reuse in which the same component can be utilized for different configurations and spans. In this article, the USC is optimized for structural performance. First, an optimized length for the USC is determined based on a trade-off between component weight and structural performance (measured by deflections). Then, topology optimization, using the simulated annealing algorithm, is implemented to determine a minimum weight layout of beams within a single USC component.     

Multiobjective design of actively controlled structures using a hybrid optimization method

A multiobjective approach to the combined structure and control optimization problem for flexible space structures is presented. The proposed formulation addresses robustness considerations for controller design, as well as a simultaneous determination of optimum actuator locations. The structural weight, controlled system energy, stability robustness index and damping augmentation provided by the active controller are considered as objective functions of the multiobjective problem which is solved using a cooperative game-theoretic approach. The actuator locations and the cross-sectional areas of structural members are treated as design variables. Since the actuator locations are spatially discrete, whereas the cross-sectional areas are continuous, the optimization problem has mixed discrete-continuous design variables. A solution approach to this problem based on a hybrid optimization scheme is presented. The hybrid optimizer is a synergetic blend of artificial genetic search and gradient-based search techniques. The computational procedure is demonstrated through the design of an ACOSS-FOUR space structure. The optimum solutions obtained using the hybrid optimizer are shown to outperform the optimum results obtained using gradient-based search techniques.     

Design optimization of laminated composite structures using distributed grid resources

Parameter studies, genetic algorithms and Monte Carlo type calculations are examples of pleasantly parallel computational tasks. Pleasantly parallel computational tasks can be effectively calculated in computer clusters or grids. In this work, we consider a weight minimization problem of a laminated composite structure in the post-buckling region. The design variables are the number of layers and the layer orientations given in a discrete set of allowable angles for layer orientations. Optimization is carried out using a deterministic search process, where the lay-up configurations are generated iteratively in the design space from the selected design points of the population at the preceding cycle. Computation is performed using NorduGrid grid computing platform. In this work, we briefly go through some general grid concepts and the use of grid in optimization of laminated composite structures.     

聚脲柔性减阻材料的制备及性能

以喷涂聚脲弹性体技术为依托,合成NCO%在13~14的芳香族聚脲半预聚物(A组分),在B组分中引入适当比例的长链氨基聚醚和位阻型胺类扩链剂,设计合适的工艺参数制备出一种低模量、高伸长率的聚脲柔性减阻涂层。与传统的硅胶、PVC、聚氨酯、丙烯酸等减阻涂层相比,该涂层具:①耐冲击,附着力好;②密度与水基本相同;③模量低,阻尼小;④涂层致密,不透水等重要特点。经中国船舶科学研究中心测试,在3 m/s~10 m/s时平板上1 mm的柔性减阻涂层可降低阻力6%以上。     

Merits and limitations of optimality criteria method for structural optimization

The merits and limitations of the Optimality Criteria (OC) method for the minimum weight design of structures subjected to multiple load conditions under stress, displacement and frequency constraints were investigated by examining several numerical examples. The examples were solved utilizing the OC design code that was developed for this purpose at the NASA Lewis Research Center. This OC code incorporates OC methods available in the literature with generalizations for stress constraints, fully utilized design concepts, and hybrid methods that combine both techniques. It includes multiple choices for Lagrange multiplier and design variable update methods, design strategies for several constraint types, variable linking, displacement and integrated force method analysers, and analytical and numerical sensitivities. On the basis of the examples solved, the optimality criteria for general application were found to be satisfactory for problems with few active constraints or with small numbers of design variables. However, the OC method without stress constraints converged to optimum even for large structural systems. For problems with large numbers of behaviour constraints and design variables, the method appears to follow a subset of active constraints that can result in a heavier design. The computational efficiency of OC methods appears to be similar to some mathematical programming techniques.     

An algorithm for optimization of non-linear shell structures

An algorithm for optimal design of non-linear shell structures is presented. The algorithm uses numerical optimization techniques and nonlinear finite element analysis to find a minimum weight structure subject to equilibrium conditions, stability constraints and displacement constraints. A barrier transformation is used to treat an apparent non-smoothness arising from posing the stability constraints in terms of the eigenvalues of the Hessian of the potential energy of the structure. A sequential quadratic programming strategy is used to solve the resulting non-linear optimization problem. Matrix sparsity in the constraint Jacobian is exploited because of the large number of variables. The usefulness of the proposed algorithm is demonstrated by minimizing the weight of a number of stiffened thin shell structures.     

基于BP-GA的冲击破岩掘进机工作机构动态优化

为了改善某型冲击破岩掘进机工作机构的动态性能,利用ANSYS Workbench建立有限元模型,通过模态分析和谐响应分析,得到其第1至第6阶固有频率和模态特性,确定了影响动态性能的模态频率;经灵敏度分析,确定了影响工作机构动态性能的主要结构参数;利用BP神经网络模型,建立所选结构参数与最大动应力、弯曲动刚度和钎杆顶端动位移间的映射关系,运用遗传算法对结构参数进行动态性能优化.结果表明,优化后工作机构的最大动位移和最大动应力分别减小27.5%和43.07%,固有频率提高24.7%,明显改善了工作机构的动态性能.     

Design and development of hybrid composite bistable structures for energy absorption under quasi-static tensile loading

The composite bistable structures discussed in this paper consist of a material-based mechanism with a saw-tooth strain/stress curve. They have a more damage-tolerant behavior, and considerably higher strain-to-failure than the corresponding monolithic material.     

Modal criteria for optimization of structures through active structural acoustic control

This paper deals with modal criteria allowing optimization of structures through active structural acoustic control (ASAC) based on the independent modal strategy control (IMSC). The aim of the paper is to propose efficient criteria allowing to process optimization of structures by determining the most important modes to control considering only the location of the excitation on the structure. A generalized modal synthesis is used to study the coupled fluid–structure system. Modal criteria are proposed in order to determine the best choice for the controlled modes used in IMSC method. The way the ASAC will be applied is not discussed in the paper. Numerical simulations are computed to show the efficiency of the method, considering a simple vibroacoustic structure. Copyright © 2010 John Wiley & Sons, Ltd.     

Crushing analysis and multi-objective optimization of different length bi-thin walled cylindrical structures under axial impact loading

This article attempts to increase the crashworthiness characteristics of energy absorbers. It is found that the effect of the bi-tubular arrangement on the energy absorption and peak force is nonlinear. This nonlinearity is somewhat related to friction but is mostly related to the changing of buckling modes. Therefore, it is possible to reach higher Specific Absorbed Energy (SAE) in the bi-tubular case than with two tubes since the weight is the same in both arrangements while the energy absorption is higher in the bi-tubular case. To exploit this, multi-objective optimization of bi-thin walled cylindrical aluminium tubes under axial impact loading is performed. The absorbed energy and the SAE are considered as the objective functions while the maximum crush load is regarded as a constraint. Finally, the optimal dimensions of tubes are found in order to maximize the SAE and energy absorption for a specified maximum crushing force.     

General model for constitutive relationships of concrete and its composite structures

This paper presents a unified mathematical model that can be used to construct various constitutive relationships for concrete materials and its composite interfaces. The unified model has a single expression and a maximum of six variables/parameters, whereas in most cases, three to four parameters are sufficient. The model is simple, continuous, and easy to be integrated and differentiated. Its parameters can be assigned clear physical meanings, and used to control variations of different parts of the curve separately. Its greater versatility and flexibility enables possible applications in almost all kinds of constitutive relationships for concrete and its composite structures. For example, it is demonstrated to be suitable for stress-strain relationships of plain and confined concrete, bond-slip relationships of steel bar-to-concrete interfaces, externally-bonded fiber-reinforced polymer (FRP) interfaces, near surface mounted FRP interfaces, etc. Furthermore, a simple equation for the bond-slip relationship of steel reinforcement-to-concrete interface is derived using the unified model to replace the four-segment CEB-FIP code model.     

新型多目标遗传算法及其在导弹射击效能优化中的应用

多目标规划是一类重要的优化模型，有着广泛的实际应用，但其求解至今仍是运筹学的一个难点．针对一般约束多目标优化问题，在设计了新的适应度函数和选择算子的基础上，提出一种新型多目标遗传算法．将其应用于导弹对集群目标射击效能优化问题，验证了算法的有效性．     

多阶段控制系统的优化及其在水平井设计中的应用

水平井三维轨道设计是以方位角、井斜角为状态变量，以曲线半径、装置角、曲线段长为控制变量，以入靶精度等为性能指标的非线性多阶段最优控制系统。针对该系统多峰的特点，本文提出一种改进的GA，该算法通过引进个体相似性来保持群体的多样性；通过定义的梯度算子生成新的个体来加速算法的收敛。将该算法用于辽河油田多口水平井的优化设计，数值结果表明了算法的正确性、有效性。     

Global shared-layer blending method for stacking sequence optimization design and blending of composite structures

A global shared-layer blending (GSLB) method is proposed for obtaining manufacturable stacking sequence of composite structures with blending and design rules. The method combines the traditional SLB technique with an evaluation algorithm of spatial variation of panels, where the manufacturability of laminates is enhanced by identifying and minimizing the ply-drops, and controlling the laminate transition drop boundaries. In addition, a blended design scheme is also proposed, which is achieved by using the stacking sequence table technique. A composite wing structure is selected to validate the efficiency and accuracy of the proposed method. Results show that the GSLB method can be used for generating more manufacturable designs of large-scale composite structure with multiple engineering constraints.     

An effective hybrid cuckoo search and genetic algorithm for constrained engineering design optimization

This article presents an effective hybrid cuckoo search and genetic algorithm (HCSGA) for solving engineering design optimization problems involving problem-specific constraints and mixed variables such as integer, discrete and continuous variables. The proposed algorithm, HCSGA, is first applied to 13 standard benchmark constrained optimization functions and subsequently used to solve three well-known design problems reported in the literature. The numerical results obtained by HCSGA show competitive performance with respect to recent algorithms for constrained design optimization problems.