某清扫车车架结构分析与拓扑优化设计

为了提高某自卸清扫车车架的力学性能并减轻重量,建立了车架的有限元模型,对车架进行了强度和刚度校核以及模态分析。并借助LS-DYNA分析了车架中间矩形框在外力激励输入下的位移时程曲线,得到了车架的变形及变化趋势,针对车架的动态变形分析结果,对车架中间矩形框的前后横梁加强区域进行了局部拓扑优化,以减少材料使用提高车架刚度,改善了车架的动态特性。分析结果表明:车架静态强度满足工作要求,工作时路面激励及怠速不会引起车架共振。     

空间桁架结构优化设计

为获得空间桁架结构的合理构型,以某空间设备支撑结构为例,分析结构材料在设计空间的分布形式和桁架结构的传力路径。在已知载荷约束和设计空间大小的条件下,基于连续体拓扑优化方法,以静态多工况刚度和动态固有频率为多目标函数进行优化分析。依据设计要求确定计算模型的结点数和结点位置,获得满足要求的空间桁架结构并进行优化设计。优化结果比原模型质量减少36.7%,一阶模态提高3.6%。     

汽车空气滤清器的模态分析及结构优化

汽车空气滤清器的表面板壳非常薄,高速气流从进气系统流过时将激励薄板结构产生振动,进而辐射出强烈的噪声,提高滤清器结构动态刚度是减小辐射噪声的有效途径,但刚度的提高通常伴随着质量的增加,实际中希望以最低的结构质量获得最大的动态刚度.针对上述问题,建立了空气滤清器的有限元模型,对其进行了模态分析.从前4阶模态分析结果找出了滤清器上下壳体的薄弱环节,然后通过调节上下壳体壁厚及合理布置加强肋的方法进行结构优化.经优化得到了一种壳体壁厚为3.5mm,加强肋厚度为2.5mm的结构优化设计方案.分析结果表明,滤清器的基频从157.1Hz提高到188.7Hz,提高了20.1％.模态测试表明,结构1阶固有频率为184.4Hz,有限元分析误差为2.3％,优化后的结构提高了低阶固有频率,降低了辐射噪声.     

基于多目标优化技术的发动机罩加强筋布局设计研究

为了加强发动机罩壳的静态刚度特性和抑制振动能力,实现罩壳结构的轻量化,引入基于水平集法的拓扑优化技术和多目标理论,完成发动机罩加强筋布局的多目标优化设计。采用折衷规划法构建关于静刚度和一阶固有频率的多目标优化模型,运用水平集法求出罩壳加强筋的最佳分布形式。结果表明,该方法能大大地提高静动态结构性能,最大应力的下降说明罩壳应力集中现象得到有效的改善,缓解罩壳的疲劳现象。此外,基于层次分析法确定权重因子,避免了多目标优化模型构建中的主观能动性。采用平均频率法对动态目标函数的处理,有效地消除了动态优化过程中的收敛性。     

重型自卸车架模态分析和结构优化

针对受较大动载荷或作用力的频率与车架某些固有频率接近时,车架会产生强烈的振动,造成破坏或不允许的大变形的问题,采用有限元法对某自卸车冲压铆接车架进行仿真分析.采用刚性单元和梁单元的组合来模拟铆钉连接;用Lanczos方法求解特征值.模态分析结果表明,该车架具有合理的低阶振型和固有频率.利用网格变形技术对车架横梁的位置进行设计优化,使车架的1阶扭转固有频率得到提升.     

飞行器空气舵系统的高效刚度分配优化方法研究

空气舵系统是飞行器典型操纵部件,其伺服作动器、连杆、摇臂、舵轴和舵面等子结构对空气舵系统的整体刚度有着不同程度的贡献,合理分配各子结构的刚度,可使空气舵系统的整体刚度得到进一步优化.本文提出了一种基于多体系统传递矩阵法和遗传算法相结合的空气舵系统高效刚度分配优化方法.首先,基于多体系统传递矩阵法建立了以结构尺寸和材料属性为参数的高效结构动力学计算模型,仿真结果表明,基于该计算模型所预测的空气舵第一阶俯仰模态固有频率与商业软件计算结果的误差仅为1.06%.其次,基于本文建立的高效结构动力学计算模型对各子结构刚度对空气舵系统动力学特性的贡献进行了灵敏度分析,给出了各部件对系统固有频率贡献的规律.最后,采取将遗传算法和多体系统传递矩阵法相结合的思路,以所建立的空气舵高效结构动力学模型为适应度函数,各子部件尺寸作为待优化变量,空气舵系统整体质量为约束条件,对空气舵系统各个子结构的刚度分配进行了优化.优化结果表明,在保持空气舵系统整体重量不变的条件下,可将空气舵系统第一阶俯仰模态固有频率提高约15.8%.     

非承载式SUV白车身结构分析及优化

以某全新开发的SUV非承载式车身为研究对象,建立V91车身有限元模型,并进行模态分析.为使车身1阶模态满足目标值要求,对车身进行灵敏度分析和截面刚度分析,并提出改进方案.经过优化,车身的1阶弯曲模态提升7.8%,1阶扭转模态提升25.7%.研究结果可为企业研发非承载式SUV车身提供参考.     

FSC方程式赛车单体壳车架设计

车架质量占赛车整车质量的比例很大,其在轻量化方面存在可优化空间。利用CATIA设计一种钢管桁架结构和单体壳结构的复合式车架,在HyperMesh中建立有限元模型,对车架的单体壳部分进行尺寸优化,确定不同区域层合板的最佳厚度,最终得到的车架质量为21.8 kg,扭转刚度为4 057 N·m/(°),较纯钢管车架减重约5 kg,刚度提高约1倍,满足设计目标。     

基于OptiStruct的望远镜主框架拓扑优化设计

针对某航空望远镜主结构的重量过高的问题,提出了对航空相机望远镜主框架进行拓扑优化设计的方法.基于拓扑优化理论,在重力过载的工况下对望远镜主框架拓扑优化,以整个框架作为设计变量,以框架的体积分数和固有频率作为约束条件,选结构的柔度最小化为目标函数,建立拓扑优化模型.采用MSC.PATRAN/NASTRAN软件对航空望远镜拓扑优化结果进行仿真,分析结果表明,结构的重量减少了77%,结构静态刚度提高,动态刚度符合要求,温度变化环境下光学成像条件改善.     

基于虚拟仿真技术的车架动态响应特性分析

采用ALGOR有限元分析软件对车架进行模态分析,得出了前10阶振型及固有频率。运用二自由度汽车振动模型,建立了系统的运动微分方程并利用Matlab中的Simulink模块对车架的振动情况做出了仿真。利用路面谱仿真得到的路面激励信号作为输入,对车架进行动力响应模拟,得到了车架在典型路面上的动态响应特性,为车架的结构优化提供了理论依据。     

Reliability-based structural optimization of frame structures for multiple failure criteria using topology optimization techniques

Topology optimization methods using discrete elements such as frame elements can provide useful insights into the underlying mechanics principles of products; however, the majority of such optimizations are performed under deterministic conditions. To avoid performance reductions due to later-stage environmental changes, variations of several design parameters are considered during the topology optimization. This paper concerns a reliability-based topology optimization method for frame structures that considers uncertainties in applied loads and nonstructural mass at the early conceptual design stage. The effects that multiple criteria, namely, stiffness and eigenfrequency, have upon system reliability are evaluated by regarding them as a series system, where mode reliabilities can be evaluated using first-order reliability methods. Through numerical calculations, reliability-based topology designs of typical two- or three-dimensional frames are obtained. The importance of considering uncertainties is then demonstrated by comparing the results obtained by the proposed method with deterministic optimal designs.     

Lightweight flatbed trailer design by using topology and thickness optimization

A new design for a lightweight flatbed trailer with high bending stiffness and torsional frequency is presented. The design procedure consists of two main steps: topology optimization and thickness optimization. During topology optimization, a creative frame layout different from existing ladder-type frames can be obtained by searching the best layout out of all possible layouts of a simplified design domain model. After approximating the result of topology optimization as a thin-walled structure, the approximated thicknesses of the plates are optimized to minimize the mass of a trailer. The bending stiffness and torsional frequency obtained by topology optimization are set as design constraints for thickness optimization. Due to the closed cross-section, the optimized trailer can efficiently increase the stiffness-to-mass ratio to a large extent. Discrete thicknesses are employed as design variables for thickness optimization so that the thicknesses of the plates of a trailer can be included in those of commercially available high-strength steel products. The final model has a 29% reduction in total mass, a 21% decrease in mean compliance with a uniform bending load, and a 169% increase in torsional frequency.     

Robust topology optimization of structures with uncertainties in stiffness – Application to truss structures

A computational strategy is proposed for robust structural topology optimization in the presence of uncertainties with known second order statistics. The strategy combines deterministic topology optimization techniques with a perturbation method for the quantification of uncertainties associated with structural stiffness, such as uncertain material properties and/or structure geometry. The use of perturbation transforms the problem of topology optimization under uncertainty to an augmented deterministic topology optimization problem. This in turn leads to significant computational savings when compared with Monte Carlo-based optimization algorithms which involve multiple formations and inversions of the global stiffness matrix. Examples from truss structures are presented to show the importance of including the effect of controlling the variability in the final design. It is also shown that results obtained from the proposed method are in excellent agreement with those obtained from a Monte Carlo-based optimization algorithm.     

基于类桁架的多工况下平面Prager结构拓扑优化

为开展多工况下曲面结构的拓扑优化,采用两向正交类桁架连续体材料模型和有限元分析方法,以杆件在结点位置的密度和方向为优化设计变量进行结构优化。根据有限元分析结果,采用满应力准则法优化各单一工况下的材料分布。按照多工况与各单工况下材料的方向刚度最大值的差值最小为原则,优化多工况下的杆件方向和密度分布。将杆件竖直位置的质心连线作为拓扑优化的平面Prager结构,以3个算例表明该方法的有效性。     

On the (non-)optimality of Michell structures

Optimal analytical Michell frame structures have been extensively used as benchmark examples in topology optimization, including truss, frame, homogenization, density and level-set based approaches. However, as we will point out, partly the interpretation of Michell’s structural continua as discrete frame structures is not accurate and partly, it turns out that limiting structural topology to frame-like structures is a rather severe design restriction and results in structures that are quite far from being stiffness optimal. The paper discusses the interpretation of Michell’s theory in the context of numerical topology optimization and compares various topology optimization results obtained with the frame restriction to cases with no design restrictions. For all examples considered, the true stiffness optimal structures are composed of sheets (2D) or closed-walled shell structures (3D) with variable thickness. For optimization problems with one load case, numerical results in two and three dimensions indicate that stiffness can be increased by up to 80 % when dropping the frame restriction. For simple loading situations, studies based on optimal microstructures reveal theoretical gains of +200 %. It is also demonstrated how too coarse design discretizations in 3D can result in unintended restrictions on the design freedom and achievable compliance.     

基于多模型拓扑优化方法的车身结构概念设计

为获得最优的初始设计方案,在车身概念设计阶段对车身结构进行拓扑优化。车身结构性能指标综合考虑整体刚度、局部动态刚度和碰撞性能,采用多模型优化(multi-model optimization,MMO)方法解决此类复杂工况的拓扑优化问题,通过调节设计空间和设置参数,获得车身最优载荷路径。根据拓扑优化结果初步形成车身框架结构,可为后期详细设计提供参考。     

Topology optimization of frame structures—joint penalty and material selection

This paper deals with joint penalization and material selection in frame topology optimization. The models used in this study are frame structures with flexible joints. The problem considered is to find the frame design which fulfills a stiffness requirement at the lowest structural weight. To support topological change of joints, each joint is modelled as a set of subelements. A set of design variables are applied to each beam and joint subelement. Two kinds of design variables are used. One of these variables is an area-type design variable used to control the global element size and support a topology change. The other variables are length ratio variables controlling the cross section of beams and internal stiffness properties of the joints. This paper presents two extensions to classical frame topology optimization. Firstly, penalization of structural joints is presented. This introduces the possibility of finding a topology with less complexity in terms of the number of beam connections. Secondly, a material interpolation scheme is introduced to support mixed material design.     

Maximization of structural natural frequency with optimal support layout

The optimal layout of supports is one of the key factors that dominates static and dynamic performances of the structure. In this work, supports are considered as elastic springs. The purpose is to carry out layout optimization of supports by means of topology optimization method. The technique of pseudo-density variables that transforms a discrete-variable problem into a continuous one is used in order that the problem is easily formulated and solved numerically. In this formulation, a power law of the so-called solid isotropic material with penalty model is employed to approximate the relation between the element stiffness matrix and density variable. Such a relation makes it easy to establish the computing scheme and sensitivity analysis of natural frequency. Support layout design that corresponds to optimization of boundary conditions is studied to maximize the natural frequency of structures. Numerical results show that reasonable distributions of supports can be generated effectively.