VMC1000L立式加工中心立柱性能分析与结构优化

立柱是VMC1000L立式加工中心的关键零部件之一,本文采用ANSYS Workbench软件对其进行仿真分析,通过分析结果梳理出零件的薄弱位置,并结合该“C”型机的结构特点和企业生产的实际情况提出了立柱的两个结构优化方案。通过对该立柱的两个结构优化方案仿真分析结果对比,从而优选出相较原始立柱最大变形减小29.7%,且二阶、三阶、四阶模态的固有频率均有大幅度提升的最佳方案,实现了立柱的结构优化,并为类似零件的性能分析与结构优化提供了有效的方法和手段。     

液压挖掘机斗杆结构的拓扑优化设计

为了提高斗杆的刚度并减小其质量,以BD85W型液压挖掘机的斗杆为例,应用变密度拓扑优化方法,以刚度最大为目标,以体积分数为约束,对斗杆结构进行优化设计,得到了液压挖掘机斗杆的新结构.斗杆的新旧结构对比表明:斗杆新结构体积减小18.22%,刚度增大6.58%,达到了预期的刚度要求.拓扑优化方法有利于提高产品的系列化程度和设计水平,能为挖掘机斗杆的结构分析和优化设计提供参考.     

基于TPA和遗传算法的动力总成悬置系统优化设计

针对某前置前驱(FF)的乘用车的怠速抖动问题,提出了基于传递路径分析(TPA)和遗传算法的动力总成悬置系统优化设计方法.利用TPA技术,将悬置系统固有特性和车内目标点振动响应相联系,并综合利用悬置系统6自由度模型,考虑其解耦率和固有频率分布,建立了悬置系统优化数学模型,进而利用NSGA-II遗传算法对其进行多目标优化,...     

考虑节点刚度的网壳杆件切线刚度矩阵

本文采用Timoshenko梁柱理论,推导出网壳杆件的切线刚度矩阵。该矩阵不仅考虑了两个主轴方向弯曲的耦合作用。而且考虑了节点刚度以及节点体大小的影响,对于位移的高阶项没有任何省略,其精度比C．Oran的切线刚度矩阵有很大程度的提高。通过对一单层网壳结构的算例分析,证明了该分析模型的正确性。     

考虑制造因素的变刚度层合板的抗屈曲铺层优化设计

与常规层合板相比,变刚度层合板的制造、有限元建模分析和铺层设计有其特殊之处。首先对设计时需考虑的制造因素进行了归纳,提出了变刚度层合板的铺层设计要求。然后给出了变刚度层合板的理想模型和考虑丝束宽度模型的建模方法。基于理想模型对ABAQUS的前处理模块进行二次开发,利用编制的参数化建模程序分析了不同铺放角的变刚度层合板的屈曲性能,并讨论了最小曲率半径对铺层的限制和变刚度设计提高屈曲载荷的机制。基于变刚度层合板的抗屈曲机制建立了一种铺层优化设计方法,使用遗传算法经两步优化得到最优铺层。对最优铺层建立考虑丝束宽度的模型以研究丝束宽度和铺层偏移对变刚度层合板抗屈曲铺层优化结果的影响。研究表明,在变刚度层合板的抗屈曲铺层优化中使用简化的理想模型通常来说是可行的。在考虑制造因素的情况下,优化后的变刚度层合板较常规层合板屈曲载荷有显著提高。     

基于多分辨率-多边形单元建模策略的多材料结构动刚度拓扑优化方法

利用多边形有限单元的高精度求解优势,融合多分辨率拓扑优化方法,实现粗糙位移网格条件下的高分辨率构型设计,由此提出多材料结构动刚度问题的拓扑优化方法。将多边形单元(位移场求解单元)劈分为精细的小单元,构造设计变量与密度变量的重叠网格,形成多分辨率-多边形单元的优化建模策略;以平均动柔度最小化为目标和多材料的体积占比为约束,建立多材料结构的动力学拓扑优化模型,通过HHT-α方法求解结构动响应,采用伴随变量法推导目标函数和约束的灵敏度表达式,利用基于敏度分离技术的ZPR设计变量更新方案构建多区域体积约束问题的优化迭代格式;通过典型数值算例分析优化方法的可行性和动态载荷作用时间对优化结果的影响机制。     

考虑混合约束的柔顺机构拓扑优化设计

为了满足制造工艺和静强度要求,提出一种综合考虑最小尺寸控制和应力约束的柔顺机构混合约束拓扑优化设计方法。采用改进的固体各向同性材料插值模型描述材料分布,利用多相映射方法同时控制实相和空相材料结构的最小尺寸,采用最大近似函数P范数求解机构的最大应力,以机构的输出位移最大化作为目标函数,综合考虑最小特征尺寸控制和应力约束建立柔顺机构混合约束拓扑优化数学模型,利用移动渐近算法求解柔顺机构混合约束拓扑优化问题。数值算例结果表明,混合约束拓扑优化获得的柔顺机构能够同时满足最小尺寸制造约束和静强度要求,机构的von Mises等效应力分布更加均匀。     

考虑混合约束的柔顺机构拓扑优化设计

为了满足制造工艺和静强度要求,提出一种综合考虑最小尺寸控制和应力约束的柔顺机构混合约束拓扑优化设计方法。采用改进的固体各向同性材料插值模型描述材料分布,利用多相映射方法同时控制实相和空相材料结构的最小尺寸,采用最大近似函数P范数求解机构的最大应力,以机构的输出位移最大化作为目标函数,综合考虑最小特征尺寸控制和应力约束建立柔顺机构混合约束拓扑优化数学模型,利用移动渐近算法求解柔顺机构混合约束拓扑优化问题。数值算例结果表明,混合约束拓扑优化获得的柔顺机构能够同时满足最小尺寸制造约束和静强度要求,机构的von Mises等效应力分布更加均匀。     

考虑结构稳定性的变密度拓扑优化方法

将稳定性问题引入传统变密度法中,可实现包含稳定性约束的平面模型结构拓扑优化。以单元相对密度为设计变量,结构柔度最小为目标函数,结构体积和失稳载荷因子为约束条件建立优化问题数学模型,提出了一种考虑结构稳定性的变密度拓扑优化方法。通过分析结构柔度、体积、失稳载荷因子对设计变量的灵敏度,并基于拉格朗日乘子法和Kuhn-Tucker条件,推导了优化问题的迭代准则。同时,利用基于约束条件的泰勒展开式求解优化准则中的拉格朗日乘子。通过推导平面四节点四边形单元几何刚度矩阵的显式表达式,得到了优化准则中的几何应变能。最后,通过算例对提出的方法进行了验证,并与不考虑稳定性的传统变密度拓扑优化方法进行对比,结果表明该方法能显著提高拓扑优化结果的稳定性。研究结果对细长受压结构的优化设计有重要指导意义,对结构的稳定性设计有一定参考价值。     

考虑玻璃刚度的高层幕墙地震响应数值分析

玻璃幕墙设计一般认为幕墙结构的力学性能主要由支承结构决定,常常忽略玻璃刚度对于幕墙的影响,或者将玻璃等效为质量施加于幕墙支承结构.然而对于超高层悬挂式幕墙结构,当承受较大风载和地震作用时,幕墙支承结构将产生较大变形,此时玻璃刚度将一定程度影响幕墙整体刚度.针对这一问题,依托上海某在建超高层大厦幕墙,研究了考虑玻璃刚度的大厦幕墙地震响应.并将此与未考虑玻璃刚度的地震响应进行对比分析,结果表明玻璃刚度增大了幕墒整体刚度,从而一定程度上减少了幕墙变形以及幕墙杆件的应力,但对大厦主体结构影响较少.本文最终的计算结果可作为该工程幕墙抗震设计参考依据.     

一维动静组合加载下深部石英片岩破坏研究

为研究锡铁山铅锌矿深部石英片岩的力学特性,利用分离式霍普金森杆(SHPB)对埋深863¹ 264m的试样进行25、30、35MPa轴压下的一维动静加载实验,和采用LS-DYNA软件模拟了25、30、35、40、45、50 MPa轴压情况下的冲击实验。研究结果表明:在冲击作用下,试样的一维动态抗压强度和破坏所需的入射能随着埋深的增加而增加,并呈现出常见的压剪破坏模式;当轴压40MPa左右,埋深1 428m的岩石动态抗压值达到最大;当轴压低于40 MPa时,轴压的增大能加强试样的抗压能力;当轴压大于40MPa时,轴压的增加反而减弱了试样的抗压能力。     

机械结构静动态性能协同分析方法研究

 分析了结构静动态性能有限元分析模型之问存在的内在共享关系，提出了静动态性能的协同分析策略．鉴于共享信息的复杂性，应用工作流管理技术对协同分析过程进行自动规划和管理，有效地提高了分析效率．提出的方法成功地应用于液压挖掘机工作装置的结构静动态性能分析，验证了该方法的合理性和有效性．     

汽车排气系统吊耳动刚度优化方法的研究

基于汽车排气系统吊耳传递的动态载荷最小、吊耳耐疲劳性最好,建立了考虑动力总成在内的排气系统振动分析模型。进行了排气系统的自由模态和约束模态的测试,并和计算值进行了对比分析,证明了所建立的排气系统振动模型的正确性。以吊耳的垂向动态载荷最小和其静变形量在一定范围内为优化目标,建立了排气系统吊耳动刚度优化模型。优化后,在怠速工况和2档全负荷加速工况下对车身底板驾驶员位置进行了振动响应测试,测试结果表明,利用优化后的吊耳刚度,能够有效降低车身底板的振动加速度,表明了阐述的排气系统建模和吊耳动刚度优化方法的有效性。文中建模与优化方法,对排气系统的吊耳动刚度计算与优化具有指导意义。     

Coupling dynamic mesh technique and heuristic algorithms in 3‐D‐tapered wing design

In this study, Onera M6 wing has been optimized by two parameters, the wing section and the taper ratio, by combining the recent mostly preferable popular approaches, i.e. parallel computing and evolutionary techniques. For the 3‐D models, developed during the optimization stages, the mesh required has been generated by using dynamic mesh technique. The code developed for this is robust and faster than the codes that produce mesh only by classical techniques. An Euler flow solver (ACER3D) is used to obtain the flow parameters for each member. From the results, it is observed that the optimization process is working as expected. During the optimization process, the lift coefficient and the thickness ratio are tried to be maintained close to the design values determined at the beginning. The taper ratio becomes smaller and converges to a certain value, while the code tries to minimize the drag force. Additionally, this study can be used as a reference for 2‐D or 3‐D aerodynamic body optimization by using heuristic‐type algorithms, since all details are outlined, referenced, and interpreted with their advantages and disadvantages. Copyright © 2007 John Wiley & Sons, Ltd.     

基于元结构的螺杆转子磨床床身动静态特性分析与优化

摘 要：螺杆转子磨床床身是关键的承载大件,其动静态性能的好坏将直接影响整机的加工精度和稳定性。为实现床身的快速动态优化设计,首先基于元结构理论,使用ANSYS软件仿真分析了床身筋格元结构各主要参数对其动态特性的影响。在此基础上,以提高床身低阶模态固有频率和降低床身重量为目标,对床身的结构参数进行优化,同时通过静力分析验证了优化方案的可行性。优化后,床身低阶固有频率得到了较大幅度的提高,其中一阶固有频率提高了22.3%,床身的重量下降了8.39%,同时静刚度也有明显提高,改善了床身的动静态特性,节约了制造成本。该方法对其他类似关键零部件的动态优化设计具有一定的借鉴意义。     

Optimal design of laminated piezocomposite energy harvesting devices considering stress constraints

Energy harvesting devices are smart structures capable of converting the mechanical energy (generally, in the form of vibrations) that would be wasted otherwise in the environment into usable electrical energy. Laminated piezoelectric plate and shell structures have been largely used in the design of these devices because of their large generation areas. The design of energy harvesting devices is complex, and they can be efficiently designed by using topology optimization methods (TOM). In this work, the design of laminated piezocomposite energy harvesting devices has been studied using TOM. The energy harvesting performance is improved by maximizing the effective electric power generated by the piezoelectric material, measured at a coupled electric resistor, when subjected to a harmonic excitation. However, harmonic vibrations generate mechanical stress distribution that, depending on the frequency and the amplitude of vibration, may lead to piezoceramic failure. This study advocates using a global stress constraint, which accounts for different failure criteria for different types of materials (isotropic, piezoelectric, and orthotropic). Thus, the electric power is maximized by optimally distributing piezoelectric material, by choosing its polarization sign, and by properly choosing the fiber angles of composite materials to satisfy the global stress constraint. In the TOM formulation, the Piezoelectric Material with Penalization and Polarization material model is applied to distribute piezoelectric material and to choose its polarization sign, and the Discrete Material Optimization method is applied to optimize the composite fiber orientation. The finite element method is adopted to model the structure with a piezoelectric multilayered shell element. Numerical examples are presented to illustrate the proposed methodology. Copyright © 2015 John Wiley & Sons, Ltd.     

动静轴结构旋翼轴载荷分离仿真分析与试验研究

动静轴结构旋翼轴是一种具有抗弹击能力的新型直升机旋翼轴构型,拟对自主设计的鼓形花键动静轴结构旋翼轴和柔性联轴节动静轴结构旋翼轴进行载荷分离特性研究。利用有限元软件对这2种动静轴结构旋翼轴的载荷分离系数进行仿真分析,并开展多通道加载试验加以验证。结果表明采用7 mm壁厚静轴时动静轴结构旋翼轴的载荷分离系数相比采用4 mm壁厚静轴时明显提高;柔性联轴节动静轴结构旋翼轴的综合载荷分离系数为77.37%,略高于鼓形花键动静轴结构旋翼轴的76.33%。研究结果可为直升机动静轴结构旋翼轴的设计提供指导。     

Optimal lay-up design of variable stiffness laminated composite plates by a layer-wise optimization technique

The optimal lay-up design for the maximum fundamental frequency of variable stiffness laminated composite plates is investigated using a layer-wise optimization technique. The design variables are two fibre orientation angles per ply. Thin plate theory is used in conjunction with a p-element to calculate the fundamental frequencies of symmetrically and antisymmetrically laminated composite plates. Comparisons with existing optimal solutions for constant stiffness symmetrically laminated composite plates show excellent agreement. It is observed that the maximum fundamental frequency can be increased considerably using variable stiffness design as compared to constant stiffness design. In addition, optimal lay-ups for the maximum fundamental frequency of variable stiffness symmetrically and antisymmetrically laminated composite plates with different aspect ratios and various combinations of free, simply supported and clamped edge conditions are presented. These should prove a useful benchmark for optimal lay-ups of variable stiffness laminated composite plates.     

Simultaneous optimal design of topology and size for a flexure-hinge-based guiding mechanism to minimize mass under stiffness and frequency constraints

The guiding mechanism based on flexure hinges (FHs) is widely used in micro/nano-manufacturing technology. Both the stiffness and the frequency of FHs play significant roles in their dynamic performance, so the design task of such a structure is to find the optimal topology and corresponding size of FHs under stiffness and frequency constraints. However, the existing optimization methods pay more attention to the stiffness than to the frequency constraint owing to difficulties in dynamic topology optimization. In this article, with the symmetrical layout assumption of FHs and the analytical equivalent stiffness and mass expression of a single FH, the simultaneous topology and size optimization problem is converted to an analytical optimization formula with both discrete and continuous variables. Finally, the tension stiffening effect is used to compensate for manufacturing errors. A design case is used to illustrate the efficiency of the proposed method.     

基于遗传算法的20 K氦制冷机的优化设计及其热力学分析

通过计算机程序实现10 k W@20 K的大型氦制冷机的热力学过程,在此基础上分析了流程中压缩机和透平膨胀机入口压力对系统制冷系数和效率的影响。同时与Matlab编写的遗传算法接口相连交互数据,从而实现针对该制冷机热力学参数的优化。选取制冷量和系统效率的加权值为优化目标,压缩机和透平膨胀机入口压力为待优化参数,通过遗传算法(GA)的优化计算得到了稳定的最优解,表明遗传算法在优化大型制冷系统过程中可以快速高效搜索到满足目标要求的全局最优解。