Layout design of thin-walled structures with lattices and stiffeners using multi-material topology optimization

In this paper, the thin-walled structures with lattices and stiffeners manufactured by additive manufacturing are investigated. A design method based on the multi-material topology optimization is proposed for the simultaneous layout optimization of the lattices and stiffeners in thin-walled structures. First, the representative lattice units of the selected lattices are equivalent to the virtual homogeneous materials whose effective elastic matrixes are achieved by the energy-based homogenization method. Meanwhile, the stiffeners are modelled using the solid material. Subsequently, the multi-material topology optimization formulation is established for both the virtual homogeneous materials and solid material to minimize the structural compliance under mass constraint. Thus, the optimal layout of both the lattices and stiffeners could be simultaneously attained by the optimization procedure. Two applications, the aircraft panel structure and the equipment mounting plate, are dealt with to demonstrate the detailed design procedure and reveal the effect of the proposed method. According to numerical comparisons and experimental results, the thin-walled structures with lattices and stiffeners have significant advantages over the traditional stiffened thin-walled structures and lattice sandwich structures in terms of static, dynamic and anti-instability performance.     

Topology optimization of joint load control with geometrical nonlinearity

This paper presents an extended topology optimization approach considering joint load constraints with geo-metrical nonlinearity in design of assembled structures. The geometrical nonlinearity is firstly included to reflect the structural response and the joint load distribution under large deformation. To avoid a failure of fastener joints, topology optimization is then carried out to minimize the structural end compliance in the equilibrium state while controlling joint loads intensities over fasteners. During nonlinear analysis and optimization, a novel implementation of adjoint vector sensitivity analysis along with super element condensation is introduced to address numerical instability issues. The degrees of freedom of weak regions are condensed so that their influences are excluded from the iterative Newton-Raphson (NR) solution. Numerical examples are presented to validate the efficiency and robustness of the proposed method. The effects of joint load constraints and geometrical nonlinearity are highlighted by comparing numerical optimization results.     

Fatigue life research and experimental verification of superalloy thin-walled structures subjected to thermal-acoustic loads

Rapid alternating stress is formed in structure subjected to harsh thermal-acoustic loads, which will affect fatigue performance and reduce fatigue life seriously. First, fatigue experiment of superalloy thin-walled structure was carried out to obtain fatigue damage location and failure time of the experiment specimen, and S-N curves of superalloy thin-walled structure at 723 K were fitted. Then, dynamic response simulation of superalloy thin-walled structure under the same load as experiment was implemented, and fatigue life was estimated based on the fatigue life prediction model which mainly included: improved rain-flow counting method, Morrow average stress model and Miner linear cumulative damage theory. Further, comparisons between simulation solutions and experimental results achieved a consistency, which verified the validity of the Fatigue Life Prediction Model (FLPM). Moreover, taking a rectangle plate as the analysis object, the distributions of Fain-low circulation blocks and damage levels of the structure were discussed respectively. Finally, current research indicates that in pre-buckling the structure is in softened area and fatigue life decreases with the increase of temperature; in post-buckling the structure is in hardened area and fatigue life increases with the increase of temperature within a certain range.     

主动冷却薄壁结构的通道布局与形状优化

针对基于传统分析方法的超然冲压发动机燃烧室主动冷却设计存在通用性差、周期长问题,采取子结构法建立主动冷却通道体胞的流固热多场耦合有限元模型,在与实验对比验证有限元模型有效性基础上,分析了结构质量和质量流率不变时通道数目对换热性能的影响;采用超椭圆方程描述通道截面形状,结合Kriging响应面和多目标遗传算法,开展了最小...     

拓扑优化与增材制造结合:一种设计与制造一体化方法

被誉为"第三次工业革命"的增材制造技术通过材料层层累加的方式实现结构的制备,这种独特的制造方式实现了高度复杂结构的自由"生长"成形,极大地拓宽了设计"空间",为新型结构及材料的制备提供了强大的工具。制造工艺的飞速发展往往需要设计技术的快速跟进,拓扑优化方法因其不依赖初始构型及工程师经验,可获得完全意想不到的创新构型,已成为结构创新设计的重要工具。因此,将拓扑优化(先进设计技术)与增材制造(先进制造技术)融合,发展面向增材制造的创新设计技术具有广阔的前景。从面向增材制造的优质结构构型设计以及考虑增材制造工艺约束的拓扑优化设计方法两个方面,介绍了现阶段基于拓扑优化方法所建立的结构创新设计理论,并指出未来研究的趋势。     

多组件结构系统布局拓扑优化中处理组件干涉约束的惩罚函数方法

包含大量组件的多组件结构系统布局拓扑优化设计中存在大量的组件干涉约束,研究了包含大量组件的结构系统整体式拓扑布局优化设计问题,基于有限包络圆方法（FCM）提出了处理组件干涉约束的惩罚函数方法,构造了包含结构刚度和组件之间几何干涉函数的内外混合惩罚函数,应用基于梯度的优化算法对包含数十个组件上百个干涉约束的多组件结构系统进行刚度优化设计,得到了清晰的支撑结构构型和无干涉的组件布局位置,充分体现了提出的混合惩罚函数方法在解决多组件结构系统布局拓扑优化设计中组件干涉问题上的有效性和适用性。     

部件级多组件结构系统的整体式拓扑布局优化

基于多组件结构系统整体式拓扑布局优化设计方法,研究了同时含有部件布局、组件布局、主结构框架构型和部件结构构型4类设计变量的复杂系统协同优化设计问题,是整体式拓扑布局优化设计面向复杂飞行器结构系统设计的拓展。采用多点约束(MPC)模拟组件、部件及支撑结构之间的刚性连接,采用有限包络圆方法(FCM)解决组件之间、组件与设计域边界之间的几何干涉问题。通过整体式拓扑布局的刚度优化设计,部件和组件均可以获得优化的布局位置,同时主结构框架构型和部件结构构型获得优化的结构样式,充分体现了整体式拓扑布局优化设计方法应用于复杂结构系统设计的能力。     

Reliability design optimization of composite structures based on PSO together with FEA

The present work aims to develop a method for reliability-based optimum design of composite structures. A procedure combining particle swarm optimization (PSO) and finite element analysis (FEA) has been proposed. Numerical examples for the reliability design optimization (RDO) of a laminate and a composite cylindrical shell are worked out to demonstrate the effectiveness of the method. Then a design for composite pressure vessels is studied. The advantages and necessity of RDO over the conventional equi-strength design are addressed. Examples show that the proposed method has good stability and is efficient in dealing with the probabilistic optimal design of composite structures. It may serve as an effective tool to optimize other complicated structures with uncertainties.     

Aeroelastic two-level optimization for preliminary design of wing structures considering robust constraints

An aeroelastic two-level optimization methodology for preliminary design of wing struc- tures is presented, in which the parameters for structural layout and sizes are taken as design vari- ables in the first-level optimization, and robust constraints in conjunction with conventional aeroelastic constraints are considered in the second-level optimization. A low-order panel method is used for aerodynamic analysis in the first-level optimization, and a high-order panel method is employed in the second-level optimization. It is concluded that the design of the abovementioned structural parameters of a wing can be improved using the present method with high efficiency. An improvement is seen in aeroelastic performance of the wing obtained with the present method when compared to the initial wing. Since these optimized structures are obtained after consideration of aerodynamic and structural uncertainties, they are well suited to encounter these uncertainties when they occur in reality.     

圆柱接触面榫连接结构的优化设计

以圆柱对平面接触特性研究为基础,提出了榫头接触面由直平面和部分圆弧面组成的结构方案,与典型的圆柱接触面榫结构方案对比,给出了设计结果.进而基于微动疲劳考虑,分别选择了最大综合参数FFD(fretting fatigue damage)最小和最大接触应力最小作为优化目标,对两种榫接触面设计方案分别进行了优化分析,结果表明以最大综合参数FFD最小为优化目标效果更好.      

不同约束条件下跨声速涡轮叶栅伴随气动优化设计

发展了一种简化的基于无反射边界理论的伴随方程进出口边界条件确定方法,研究了考虑不同约束的叶片气动外形优化设计。研究结果表明:采用流动强耦合的简化伴随方程进出口边界条件确定方法,能够确定精度较高的伴随灵敏度,在不同类型的伴随气动优化设计中均具有较好适用性。无约束的出口质量熵优化后,出口质量熵降低0.253%,流道面积和出口气流角变化较大。分别考虑出口气流角气动约束、流道面积几何约束和同时考虑上述两种约束的影响,优化后出口质量熵分别降低0.176%、0.227%和0.164%,优化后叶片气动性能显著提升,且满足约束条件。改变叶型曲率能有效减弱激波强度,吸力面前段曲率降低时,流动减速、出口气流角增大,吸力面前段曲率变化较小时,出口气流角约束较好。      

类C-HGB布局锐边化气动隐身优化设计

C-HGB （Common Hypersonic Glide Body）作为美国现今试验成功率最高的高超声速滑翔飞行器已被美国防部列入重点发展项目,并预计发展为三军通用武器。本文针对此类"球+双锥+弹翼"的气动外形和隐身性能进行了研究。采用考虑交互作用的正交设计进行了多约束下参数敏感性分析,并采用改进的基于DE差分变异算子的具有自适应学习机制的优化算法进行气动优化,对优化后的外形采用简单高效的锐边化设计,在提高升阻比的同时可降低雷达散射截面积,极大提高突防能力。锐边设计改变了弹体部分表面温度分布,降低制造成本的同时对热防护系统的设计和红外隐身具有一定积极意义。结果表明：锐边化设计可以得到较好的气动隐身性能,是未来高超声速滑翔飞行器的潜在设计方案。     

多孔材料夹层结构声辐射特性的两尺度拓扑优化设计

基于均匀化计算理论结合结构构型设计和材料构型设计,建立以声辐射功率为目标的两尺度材料/结构协同优化模型,针对夹层结构声学设计问题,开展了声辐射特性拓扑优化研究。分别给出了声辐射功率对宏观和微观设计变量的灵敏度,结合移动渐近线法(MMA)实现了材料/结构两尺度设计。结果表明,声辐射功率两尺度优化改变了夹层结构各阶主振型的形状和顺序,同时也改变了被激发的振型。此外,算例研究了激励频率和约束对优化结果的影响以及声辐射功率目标优化的特殊现象。     

简谐力激励下多组件结构系统的整体优化设计

多组件结构系统整体优化设计通过协同优化支撑结构拓扑构型和组件布局来使结构系统的位移响应最小。本文提出通过模态加速度法（MAM）求解多组件结构系统的位移响应,并以位移响应值最小作为优化目标;引入多点约束（MPC）方法模拟组件与设计域间的铆钉或螺栓连接形式;采用有限包络圆法（FCM）来避免组件之间及组件与设计域边界产生干涉。建立了多组件结构系统整体优化问题的数学模型,并对动响应目标函数关于设计变量的灵敏度进行了推导。最后,通过几个算例验证了整体优化方法在简谐力激励下求解问题的可行性及其在实际问题中的有效性。     

Precise output loads control of load-diffusion components with topology optimization

The purpose of this paper is to present a novel topology optimization approach to control precisely the output loads under static loads and harmonic excitations.We introduce the Artificial Bar Element(ABE) at the designated output positions, where the output loads are equivalently measured and constrained with the nodal displacements of ABE.Optimization model is then formulated considering the output load constraints as well as the minimization of strain energy and dynamic displacement responses...     

Location layout design of aircraft parts assembly based on MSVR

Location layout of aircraft assembly is an important factor affecting product quality.Most of the existing re-searches use the combination of finite element analysis and intelligent algorithm to optimize the location layout,which are limited by numerical simulation accuracy and the selection and improvement of intelligent algorithms.At present,the analysis and decision-making technology based on field data is gradually applied in aircraft manufacturing.Based on the perception data of intelligent...     

6156-T4铝合金焊接加筋薄壁结构剩余强度评估的CTOD方法

为保证飞机设计满足损伤容限性能要求,有必要对其进行剩余强度评估。针对6156-T4铝合金焊接连接薄壁结构进行了R曲线和剩余强度试验,判断了裂纹扩展经过筋条时的裂纹扩展路径,测量了母板和筋条两个方向的裂纹扩展速率,并采用不同的断裂准则和分析方法对单及双跨度多个初始裂纹长度焊接加筋薄板的剩余强度进行了预测。结果表明:裂纹扩展在经过筋条时,同时沿着母板和筋条继续扩展,筋条上的裂纹扩展方向垂直于母板且两个方向的裂纹扩展速率基本相同;采用净截面屈服准则进行剩余强度预测时会低估这种韧性较好的焊接连接薄壁结构的剩余强度;基于SINTAP-FITNET评价体系,以裂纹尖端张开位移(CTOD-δ5)作为裂纹尖端弹塑性表征参量进行剩余强度预测时,预测结果比采用K曲线预测方法精度高。     

边缘连接设计对座舱透明件承载能力的影响

研究了不同边缘连接设计对座舱透明件承载能力的影响.测定了拉伸破坏载荷和冲击能,结果表明,材料种类、边缘连接形式、孔边距等多种因素均会影响边缘连接件的承载能力.     

大跨度空间结构典型形体风压分布风洞试验研究现状

随着科学技术的发展和施工工艺的进步,各种外形美观、结构新颖的大跨度空间结构得到了广泛的应用。这类结构往往对风荷载十分敏感,其屋面几何形状对表面风压分布有着重大影响。不同形式的屋面,表面风压分布有很大区别;即使屋面整体形式相同,但由于其矢跨比(f/D)、长跨比(L/D)等几何参数的不同,也会使屋面风压分布发生较大变化。对此,目前尚无详细规范可依。本文回顾了几类典型空间结构的风洞试验,总结了这几类结构的屋面几何形状与风压分布之间的变化规律,为大跨空间结构风压分布规律确定及气动优化设计研究提供参考。     

Geometry and size optimization of stiffener layout for three-dimensional box structures with maximization of natural frequencies

Based on the growth mechanism of natural biological branching systems and inspiration from the morphology of plant root tips, a bionic design method called Improved Adaptive Growth Method (IAGM) has been proposed in the authors’ previous research and successfully applied to the reinforcement optimization of three-dimensional box structures with respect to natural frequencies. However, as a kind of ground structure methods, the final layout patterns of stiffeners obtained by using the IAGM are highly subjected to their ground structures, which restricts the optimization effect and freedom to further improve the dynamic performance of structures. To solve this problem, a novel post-processing geometry and size optimization approach is proposed in this article. This method takes the former layout optimization result as start, and iteratively finds the optimal layout angles, locations, and lengths of stiffeners with a few design variables by optimizing the positions of some specific node lines called active node lines. At the same time, thicknesses of stiffeners are also optimized to further improve natural frequencies of three-dimensional box structures. Using this method, stiffeners can be successfully separated from their ground structures and further effectively improve natural frequencies of three-dimensional box structures with less material consumption. Typical numerical examples are illustrated to validate the effectiveness and advantages of the suggested method.