AGENT based structural static and dynamic collaborative optimization

A static and dynamic collaborative optimization mode for complex machine system and its ontology project relationship are put forward, on which an agent-based structural static and dynamic collaborative optimization system is constructed as two agent colonies: optimization agent colony and finite element analysis colony. And a two-level solving strategy as well as the necessity and possibility for handing with finite element analysis model in multi-level mode is discussed. Furthermore, the cooperation of all FEA agents for optimal design of complicated structural is studied in detail. Structural static and dynamic collaborative optimization of hydraulic excavator working equimpent is taken as an example to show that the system is reliable.     

Optimal Structural Modifications of a Gun Tripod for Desired Natural Frequencies

Sensitivity analysis and structural modification techniques are used to investigate the structural modifications of a machine gun tripod which suffers from severe vibration during firing due to the resonance. The finite element analysis and modal test techniques are used to determine the natural frequencies of the machine gun. The sensitivities of natural frequencies with respect to the structural parameters of the tripod are obtained by the method of sensitivity analysis, and they can be used as an indication for the structural modification of the tripod so as to shift the natural frequencies effectively. By the structural modification techniques, finally, the optimal structural modifications of the tripod for desired natural frequencies are made to avoid the resonance, and this optimal structural modification is verified by re-analysis of the modified structure and the vibration contrast between original structure and modified structure. The research resulted in a successful structural modification for desired natural frequencies, which can avoid the resonance and thereby greatly improve the shooting precision of the machine gun during firing.     

枪管温度场和热应力的研究

目的　研究大口径高射机枪在连续发射过程中枪管的温度场和热应力、应变的变化规律 .方法　利用有限元分析法 ,通过物理模型和有限元模型的建立以及边界条件的处理等 ,在数值上对枪管的温度、温度梯度和热应力、应变变化规律进行分析 .结果　得出大口径高射机枪在连续发射过程中 ,距内膛不同距离上的温度、温度梯度、温度等效应力、应变和全等效应力、应变随时间的变化规律 .结论　在连续发射过程中 ,热作用对管壁中应力应变的影响是先由次要因素上升为主要因素的 ,而非一开始就是其主要影响因素 .所以在连续发射时 ,热作用是枪管壁内应力、应变的主要来源 ,也是枪管破坏的主要原因 .     

CAD软件与有限元软件的集成技术研究

结合ＡｕｔｏＣＡＤ绘图功能的特点与有限元分析需要建立力学模型的要求,通过采用数图交换格式及数据交换技术,以ＡＳＣＩ码文件作为过渡文件,将ＣＡＤ软件与有限元软件集成化,为设计和分析产品零部件提供了一种新方法．     

结构动力响应分析的多重网格方法

提出了一种适合于有限元分析中求解结构动力响应的多重网格方法,该方法利用初始网格下的结果,通过双线性插值技术得到网格变化后新的近似位移向量,然后由多重网格迭代过程求解结构动力响应问题。在多重网格迭代的前光滑过程中,选择了共轭梯度法提高其收敛率;在粗网格校正过程中,给出了一种近似求解位移向量误差的方程;在后光滑过程中,选择了Jacobi松弛迭代提高解的光滑性。该方法将网格离散过程和数值求解过程结合在一起,建立了一个网格细分后结构动力响应问题的快速重分析方法,与传统有限元方法相比较,具有计算简便、迭代步骤少,运算时间短等特点,可以作为结构动力问题自适应有限元分析的一种十分有效的工具。同时,本文还给出了一种简单实用的时间步长划分的自适应方法。     

大口径机枪弹簧液压式浮动机优化设计

目的　对浮动技术在大口径高射机枪上的应用进行研究, 并对浮动机参数进行设计． 方法　采用单目标优化的方法． 结果　通过优化设计, 得到了一组满足条件的浮动机结构参数, 并分析了该组参数下机枪的性能． 结论　浮动技术应用于大口径机枪是完全适合的, 它不仅可以大幅度地减小后坐力, 而且通过参数的合理匹配, 具有良好的浮动稳定性, 对提高射击精度是有利的     

基于自动微分的随机有限元方法

基于自动微分技术的基本原理,结合有限元分析,提出了一种随机有限元的计算方法。采用Fortran90语言编写了计算模块,可以在计算应力和应变等响应数值的同时,快速准确地计算出应力和应变对各随机参数的偏导数值。应用该方法对高压天然气罐进行了随机结构的响应分析,其结果与蒙特卡洛方法的模拟结果基本吻合。该方法不但可以分析随机参数为载荷和材料特性的随机结构,而且还可以分析随机参数为几何形状尺寸的随机结构,特别适合于一些求不出解析解但可以用有限元计算的工程结构的随机响应分析,为随机有限元的工程应用奠定了基础。     

机枪振动主动控制技术研究

目的　利用压电传感器和作动器主动控制技术解决机枪射击时的振动问题． 方法　采用智能结构的原理和方法, 对压电元件用于机枪结构振动控制的有关问题进行了研究． 结果　建立了机枪身管压电结构机电耦合动力学模型, 导出了控制方程, 给出了振动控制仿真结果． 结论　智能结构主动控制技术可以有效地抑制机枪射击时的振动响应, 提高射击密集度     

立式微铣床结构的优化设计与分析

在立式微铣床的设计期间,对机床常用结构进行拓扑优化分析,初步确定龙门结构基本形状。然后通过Ansys Workbench中的Design Exploration模块设计仿真实验,采用响应面法(RSM),以减小静力变形量和应力为目标,对立式微铣床龙门结构的跨度和高度参数进行了优化,利用权函数法得出该模型下的最优结果,加强了立式微铣床龙门结构稳定性。最后通过有限元分析软件对该立式微铣床整机结构进行了动静态特性分析,对微铣床结构设计上能否满足设计要求进行了校核。     

Analysis of lateral stability of I-section aluminum beams

This paper focuses on the lateral buckling of laterally-unrestrained aluminum beams subjected to a concentrated, uniformly loading and pure-bending action. The design methods of lateral stability of aluminum beams in the current codes are discussed. The influence of material property on the lateral buckling of aluminum beams is investigated with finite element analysis (FEA) methods. Some numerical examples are given, and the results from current codes are compared with the FEA solutions. The design method on lateral stability of steel beams specified in the Chinese standard GB 50017-2003 is modified to calibrate the stability factors of aluminum beams according to the European code, British code, and American code, and the modified method is verified by FEA results. Through comparison with the available test results, the modified design method for overall stability of aluminum bending members is proposed in this paper and proved applicable in the design of lateral stability of aluminum beams.     

重机枪系统定型试验辅助决策系统研究

介绍了重机枪系统定型试验辅助决策系统的设计方法、组成和主要研究内容;利用系统工程原理,创建了重机枪系统性能综合评定模型;利用超媒体技术,开发了系统应用软件,解决了重机枪系统性能综合评定、试验信息管理和大幅面图漫游等技术问题.研究成果有利于提高试验训练的效益,满足了试验训练基地对重机枪系统性能综合评定的需要.     

有限元法在薄壁壳体零件设计中的应用

有限元法是机械零件设计中的高级技术 ,在薄壁等复杂及特殊要求的零部件设计中 ,能够发挥特别的作用。本文通过一个工程实例说明该技术在产品设计中的重要作用     

基于LS-SVM的结构可靠度响应面分析方法

金伟良，袁雪霞 针对实际工程中常见的功能函数不能显式表达的可靠性分析问题，提出了一种基于最小二乘支持向量机（LS-SVM）的结构可靠度响应面分析方法.采用正交试验设计和有限元程序生成学习样本，并依据各随机变量的概率分布抽样得到检测样本;利用LS SVM的高度非线性映射能力，建立了结构响应量与随机变量之间的映射关系.进而结合Monte-Carlo原理，计算结构的失效概率.新方法可直接应用现有的有限元分析程序，对大型结构进行可靠性分析.通过典型工程结构的算例分析，结果表明该方法具有较好的效率和精度.     

Computational uncertainty principle in nonlinear ordinary differential equations (I)——Numerical results

In a majority of cases of long-time numerical integration for initial-value problems, roundoff error has received little attention. Using twenty-nine numerical methods, the influence of round-off error on numerical solutions is generally studied through a large number of numerical experiments. Here we find that there exists a strong dependence on machine precision (which is a new kind of dependence different from the sensitive dependence on initial conditions), maximally effective computation time (MECT) and optimal stepsize (OS) in solving nonlinear ordinary differential equations (ODEs) in finite machine precision. And an optimal searching method for evaluating MECT and OS under finite machine precision is presented. The relationships between MECT, OS, the order of numerical method and machine precision are found. Numerical results show that round-off error plays a significant role in the above phenomena. Moreover, we find two universal relations which are independent of the types of ODEs, initial val     

Computational uncertainty principle in nonlinear ordinary differential equations--Numerical results

In a majority of cases of long-time numerical integration for initial-value problems, round-off error has received little attention. Using twenty-nine numerical methods, the influence of round-off error on numerical solutions is generally studied through a large number of numerical experiments. Here we find that there exists a strong dependence on machine precision (which is a new kind of dependence different from the sensitive dependence on initial conditions), maximally effective computation time (MECT) and optimal stepsize (OS) in solving nonlinear ordinary differential equations (ODEs) in finite machine precision. And an optimal searching method for evaluating MECT and OS under finite machine precision is presented. The relationships between MECT, OS, the order of numerical method and machine precision are found. Numerical results show that round-off error plays a significant role in the above phenomena. Moreover, we find two universal relations which are independent of the types of ODEs, initial values and numerical schemes. Based on the results of numerical experiments, we present a computational uncertainty principle, which is a great challenge to the reliability of long-time numerical integration for nonlinear ODEs.     

基于Taguchi实验设计方法优化PoP的翘曲

通过对PoP的翘曲进行优化分析,采用有限元分析方法分析了PoP中FBGA和PBGA的翘曲形变,并利用Taguchi设计和有限元模拟相结合的方法进行优化设计.分析结果表明:PBGA具有较大的翘曲,增加基板厚度和塑封料热膨胀系数,减小芯片大小和厚度可以改善PBGA的翘曲.对比优化前后的翘曲,在25 ℃时翘曲值从53.3 μm降到39.1 μm,260 ℃时翘曲值从-112 μm降到了-67.7 μm.塑封料热膨胀系数和芯片尺寸在优化翘曲中起着重要作用.     

转管机枪开闭锁系统的总体分析设计

目的　探讨转管机枪机心组开闭锁系统的分析设计 ,并保证其布置合理 ,结构简单 ,动作可靠 .方法　在优化机心匣凸轮曲线的基础上 ,通过合理分析机心在开闭锁运动时的回转角 ,确定开锁臂和闭锁臂位置及长度来设计开闭锁系统 .结果　设计出了能满足要求的机心组开闭锁系统 .结论　该方法可用来指导转管武器的机心组开闭锁系统设计     

基于灵敏度分析的机枪结构动力修改研究

介绍了机械结构灵敏度分析的基本理论,探讨了用有限元法进行结构优化和灵敏度分析的一般过程．以某型机枪的枪架为例建立了有限元结构分析模型,选择枪架的弯曲刚度、扭转刚度和整枪的第一阶固有频率为性能约束,根据灵敏度分析结果,按高强度、轻质量的要求,选择出有效的设计变量进行了重量最轻和性能最优的结构优化．同时,利用试验测试数据对优化前后武器的动态响应进行了仿真对比．结果表明,优化后武器的射击频率与固有频率的匹配更加合理,提高了武器的射击精度．     

机床主轴结构的有限元——优化设计

运用有限元法和优化设计理论,建立机床主轴结构设计的优化数学模型,选择优化方法,进行了实例计算。     

大口径转管高射机枪轻量化关键技术

目的　研究大口径转管高射机枪轻量化技术 .方法　从武器系统角度出发 ,对枪身两种原理方案进行了比较 ,针对该武器系统 ,从枪身和枪架两大部分出发 ,对主要构件进行了分析 .结果　提出了大口径转管高射机枪轻量化的一些关键技术 .结论　研制步兵用转管武器 ,必须对轻量化关键技术进行攻关