某SUV车架多目标拓扑优化设计

为得到同时满足刚度和动态要求的SUV车架,基于SIMP材料插值方法,分别以刚度最大和低阶模态固有频率最大作为优化目标建立拓扑优化模型,利用折中规划法建立多工况下刚度和低阶固有频率多目标优化模型,通过拓扑优化迭代得到新的SUV车架;对新车架进行仿真分析,得到其位移和应力分布及前4阶固有频率.其静态特性满足材料要求且有很大提高,第1阶固有频率提高到30.3 Hz,新车架质量减轻到193.3 kg.计算结果表明该方法能够很好地解决多目标下的结构优化问题。     

摩托车车架模态、刚度Nastran优化实例

本文采用有限元结构分析软件Nastran对摩托车车架的模态、刚度进行优化,计算各个设计变量的灵敏度系数,并结合工程实际,找出了对车架第一阶模态频率和弯曲、扭转刚度值影响最大的因素。     

高重复定位稳定精度的副车架设计

为了保证车载光电跟踪设备载车平台的刚度和位置稳定性,设计了一种新的高重复定位稳定精度的副车架结构.副车架采用焊接成型,通过材料和型材的选取以及结构的设计,可以提高副车架的刚度,在上述基础上,采用三点支撑的方式,能够保证其拥有较高的重复定位稳定精度.建立数学模型,在三点支撑的状态下对模型进行变形和应力分析,检验副车架的刚度性能,对模型进行模态分析,验证结构设计可以避开激励的实际频率,避免整车共振现象的发生,最后通过设计实验来检验副车架的刚度性能及重复定位稳定精度.实验结果表明副车架的变形满足使用要求,证明副车架的设计合理.     

装载机后车架焊接顺序优化的数值仿真

利用热弹塑性有限元法和Marc对装载机后车架的焊接变形进行数值仿真.分别用壳单元和实体单元进行仿真,对比焊接角变形,结果表明两者精度比较相似.建立后车架壳单元热-力耦合模型,定性对比在相同约束条件下焊接顺序对整个后车架结构内缩变形和面外弯曲变形的影响.结果表明,在先焊接框架焊缝的条件下,整体结构刚度增大,各种变形较小;其中,当采用正/反面焊缝、立焊缝依次焊接时,大梁下挠峰值最小,为0.002 m,从而确定后车架最佳焊接顺序方案,在该顺序下的变形模拟值与实测值吻合良好.     

基于有限元法的客车车架结构分析与研究

在Hypermesh软件中采用板壳单元对车架几何模型进行网格划分,建立车架的有限元模型。根据客车的承载特点和行使工况,对该车车架进行动力学分析。并对车架进行模态计算,得到车架的固有频率和固有振型。配合实验数据,对车架结构的设计提出了合理的改进方案,本文可获得较高的工程应用价值。     

基于多工况的车门结构多目标优化设计方法研究

车门结构的单一工况优化设计常难以满足车门设计要求。本文基于车门垂直刚度和一阶模态两工况,提出一种车门结构多工况多目标优化设计方法。以车门垂直刚度、一阶频率和车门质量为优化目标,通过均匀拉丁方试验设计和响应面方法得出车门垂直刚度和一阶频率的近似数学模型,并在此基础构建车门结构多目标优化模型。最后采用多目标遗传算法对其进行求解,最终优化结果在车门质量减少的情况下,垂直刚度和一阶频率均达到设计要求,达到预期优化效果。     

转向架齿轮箱吊杆的优化设计

针对某转向架齿轮箱吊杆开发设计过程中吊杆原始结构工作安全因数过大的问题,为进行轻量化设计,基于OptiStruct采用拓扑优化结合自由形状优化的方法对吊杆进行优化设计.优化后吊杆的质量减轻约38.3%,其工作安全因数和刚度满足要求.     

轨道动力车车架结构强度与刚度分析

为了计算轨道动力车车车架的静强度,保证动力车正常的工作和运行,提出了一种在三维软件中建模方法与边界条件的施加方法。运用ANSYSWORKBENCH软件对车架进行结构静强度和刚度的有限元分析并与试验结果对比。结果表明:车架的静强度和刚度均满足设计要求,对于同一测试点其仿真分析的应力值与试验得到的应力值误差基本在15%以内,结果一致性较好,所提出的方法也可以为其他类型的车架建模及仿真分析提供参考。     

基于MSC Nastran的前副车架动刚度分析

设计某A级乘用车的前副车架,并用HyperMesh建立其有限元模型,用MSC Nastran的模态频率响应方法对该前副车架进行动刚度分析,得到相关频率的动刚度值.对该前副车架悬置点的动刚度分析可以为车辆NVH性能提供理论参考.     

基于APDL的结构拓扑优化程序开发及在C919客机舱门铰链臂设计中的应用

为使结构在相同甚至更少质量下获得更大的刚度,并让设计过程更加科学和高效,根据拓扑优化技术利用APDL对ANSYS进行二次开发,并与基准算例比较验证该程序的有效性,实现结构的轻量化设计.将所开发的程序用于C919客机舱门铰链臂结构的最小柔度设计,获得比2种原始设计方案刚度更大的轻质拓扑构型,具有一定的实际参考价值.所开发的程序具有如下优点:适用于低阶单元,极大提升计算效率;可扩展到包括实体单元在内的各种单元类型,如梁、板和壳等,有效增加结构模型的应用范围;引入并实现FILTER技术以避免使用低阶单元优化时出现棋盘格现象;具有针对拓扑优化结果的有特色的后处理模块.     

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.     

基于拓扑优化的中央空调模块机机架结构设计

为提高中央空调模块机的整体性能和品质,对模块机机架的结构框架进行最优化设计.基于拓扑优化方法,利用HyperWorks建立有限元模型并施加载荷和边界条件;以节点位移为约束条件,以模型体积最小化为目标函数,对模块机机架进行分析和结构优化.结果表明,拓扑优化方法可以获得较优的结构模型,可以改善结构的力学性能,减轻产品质量和降低制造成本.     

Seismic energy dissipation-based optimum design of tuned mass dampers

Tuned mass dampers (TMDs) are a subclass of dynamic vibration absorbers that consist of a mass-spring-damper unit that is attached to a structure to adjust its response to seismic and wind loads. The efficacy, performance and optimum design of a TMD strongly depend not only on its mass, stiffness and damping as well as the input energy and the structure characteristics, but also on the structural response parameter(s) that the TMD is intended to mitigate. In that respect, this study evaluates the suitability of four objective functions for the optimum design of the TMD of an inelastic, steel moment-resisting frame (SMRF) under an artificial, white-noise excitation. The objective functions include 1) the maximum roof lateral displacement, 2) the maximum drift, 3) the root mean square of drifts and 4) the cumulative hysteretic energy of the SMRF. The results indicate that the SMRF equipped with a TMD optimized using the cumulative hysteretic energy of the SMRF as the objective function exhibits the best seismic response under the artificial earthquake. Further examining the response of the TMD-equipped SMRF under four historic earthquake records shows that equipping a structure with a TMD optimized using an artificial earthquake will not warrant that the structure will exhibit a better seismic performance in all measures compared with when no TMD is used. Put other way, while the minimization of cumulative hysteretic energy could be the best objective function for a case subjected to an artificial earthquake, under real earthquakes, none of the objective functions consistently results in a better seismic performance. This behavior is attributed to detuning effects arising from major structural damages and significant period shifts that occur during strong earthquakes.     

Structural optimization with several discrete design variables per part by outer approximation

The article proposes an optimal design approach to minimize the mass of load carrying structures with discrete design variables. The design variables are chosen from catalogues, and several variables are assigned to each part of the structure. This allows for more design freedom than only choosing parts from a catalogue. The problems are modelled as mixed 0–1 nonlinear problems with nonconvex continuous relaxations. An algorithm based on outer approximation is proposed to find optimized designs. The capabilities of the approach are demonstrated by optimal design of a space frame (jacket) structure for offshore wind turbines, with requirements on natural frequencies, strength, and fatigue lifetime.     

动载体光电平台框架结构优化设计

在优化设计光电平台的研究中,由于动载体光电平台的光电传感器均安装在内框架上,内框架的谐振频率过低则易引起谐振,严重影响平台的稳定性。为提高内框架的谐振频率,对内框架结构进行了优化设计。根据灵敏度分析理论,以固有频率和振型幅值为目标函数,分析不同参数对结构性能的影响,通过修改对框架结构影响最为灵敏的参数改善框架的模型,应用ANSYS软件进行有限元动力学仿真。优化后的框架结构最低谐振频率提高到了270.93Hz,避开了平台伺服机构的带宽并远高于外界扰动频率,降低了框架机械谐振,提高了稳定性,为光电平台的结构优化设计提供了理论依据。     

Optimum structural design of spatial steel frames via biogeography-based optimization

Metaheuristic algorithms have provided an efficient tool for designers by which discrete optimum design of real-size steel space frames under design code requirements can be obtained. In this study, the optimum sizing design of steel space frames is formulated according to provisions of Load and Resistance Factor Design—American Institute of Steel Construction. The weight of the steel frame is taken as objective function. The design algorithm selects the appropriate W sections for members of the steel frame such that the frame weight is the minimum and design code limitations are satisfied. The biogeography-based optimization algorithm is utilized to find out the optimum solution of the discrete programming problem. This algorithm is one of the recent additions to metaheuristic techniques which are based on theory of island biogeography where each habitat is assumed to be potential solution for the design problem. The performance of the biogeography-based optimization algorithm is compared with other recent metaheuristic algorithms such as adaptive firefly algorithm, teaching and learning-based optimization, artificial bee colony optimization, dynamic harmony search algorithm, and ant colony algorithm. It is shown that biogeography-based optimization algorithm outperforms other metaheuristic techniques in the design examples considered.

     

Topology optimization of frame structures with flexible joints

A method for structural topology optimization of frame structures with flexible joints is presented. A typical frame structure is a set of beams and joints assembled to carry an applied load. The problem considered in this paper is to find the stiffest frame for a given mass. By introducing design variables for beams and joints, a mass distribution for optimal structural stiffness can be found. Each beam can have several design variables connected to its cross section. One of these is an area-type design variable which is used to represent the global size of the beam. The other design variables are of length ratio type, controlling the cross section of the beam. Joints are flexible elements connecting the beams in the structure. Each joint has stiffness properties and a mass. A framework for modelling these stiffnesses is presented and design variables for joints are introduced. We prove a theorem which can be interpreted as the fact that the removal of structural elements, e.g. joints or beams, can be modelled by a small strictly positive material amount assigned to the element. This is needed for the computations of sensitivities used in the applied gradient based iterative method. Both two and three dimensional problems, as well as multiple load cases and multiple mass constraints, are treated.     

基于特征造型的重载货车辗钢整体车轮结构设计优化

为减轻重载货车车轮的质量、提高使用寿命,将常规的设计优化方法、参数化特征造型和有限元分析结合,进行重载货车辗钢整体车轮设计优化.以车轮轻量化为优化目标,基于特征建模方法确定设计变量,用有限元分析确定车轮强度和刚度的约束条件,建立辗钢整体车轮的设计优化模型.设计优化和参数化特征造型为有限元分析提供轮辐的几何尺寸,有限元分析主要进行优化后的车轮应力分析,并判断优化后车轮应力是否得到改善.参照＂GB 8601—1988铁路用辗钢整体车轮＂,采用通用CAD/CAE软件建立重载货车辗钢整体车轮的三维实体模型,对其进行设计优化,取得满意的效果.     

高效LDPC译码器的优化与FPGA实现

针对高效LDPC译码器设计过程中的参数选择问题,提出了针对Turbo译码消息传播（Turbo decoding message passing,TDMP）译码算法的离散密度进化算法。利用这种离散密度进化算法对译码算法中的校正因子及量化精度进行了优化。与传统的通过数值仿真进行优化的方法相比,本文算法效率大大提高,且效果显著。测试结果表明,优化的定点化译码器与纯浮点仿真相比性能只相差0.1 dB左右。在译码器实现结构设计中提出了一种基于分布式RAM的P消息循环存储结构,与传统的基于寄存器和Benes网络的存储器结构相比,资源消耗明显下降。在Xilinx公司的FPGA平台上进行了硬件实现与测试,结果表明与同类译码器相比在资源消耗和吞吐率上均有一定优势,是一种高效的LDPC硬件译码器。