模态分析在多联涡旋压缩机组振动分析中的应用

本文介绍了常见的并联机组管路振动的原因及其排查方式。针对某型号机组排气管路剧烈振动的问题,对机组结构和排气管路进行实验模态分析,确定机组结构和排气管路发生共振,通过结构优化改变其固有频率,使管路振动值降低。     

汽车传动轴振动的仿真计算及优化

考察汽车传动轴振动特性的指标为1阶约束模态的频率。由此,某商用车传动轴在设计阶段进行模态仿真分析,虽然满足了设计要求,但在整车验证阶段却出现共振,产生了车内共鸣音。针对该问题,改进传动轴模态分析方法,并对传动轴结构进行优化设计,消除共振模态。通过主观评价和噪声测试证实效果良好。     

利用CAE方法分析某客车整车共振问题

通过对客车结构进行合理的简化和等效,在建立了客车主要承载结构的几何模型的基础上,建立了能反映客车结构动态特性的有限元模型。随后对客车的有限元模型进行模态分析,计算出整车结构的固有频率和主要振型,并将模态分析结果与测试结果对比。经过分析,查明了问题客车运行时产生整车共振的原因,为进一步解决客车共振问题提供了可靠的理论依据。     

半挂牵引车整车模态分析

着重针对某半挂牵引车整车进行模态分析。首先通过UG对牵引车整车建模,然后运用HyperWorks对模型进行网格的划分生成整车有限元模态分析模型,最后对其进行模态分析,得到系统的各阶模态,并按照实际情况对模态参数进行分析。有限元模态分析结果表明该牵引车整车结构固有频率能有效避开各种激励源频率,避免发生共振现象。     

某航空发动机整体叶盘耦合振动特性分析

通过建立某航空发动机整体叶盘的三维实体模型,对整体叶盘结构的耦合振动特性进行了固有模态特性分析。根据有限元软件ANSYS的计算结果,绘制了叶片共振转速Campbell图,分析了整体叶盘结构模态振动的基本特性,得到了整体叶盘节径-频率图,分析的结果为进一步研究整体叶盘的结构设计优化和避免共振提供了依据。     

某消声器断裂问题的研究

针对某消声器筒体与排气管焊接处发生断裂的问题,运用CAE定量分析方法和模态测试分析技术对断裂消声器进行分析研究,并提出将原消声器的排气管贯穿筒体的改进方案。同时对改进前后的消声器进行理论模态和试验模态分析。分析结果表明,改进措施是合理的,提高消声器的工作可靠性。     

某轿车排气系统振动分析

联合有限元软件与AVL-Excite软件,对某轿车排气系统进行模态与强迫振动分析。首先利用有限元软件对排气系统做自由模态分析,初步分析其吊耳点布置合理与否。然后利用有限元软件对排气系统进行自由度缩减,提取其质量矩阵、刚度矩阵、主节点自由度信息及模态信息,整合到内燃机-排气系统多体动力学模型中,对排气系统进行受迫振动分析,充分考虑其弹性变形与模态共振对振动响应的影响。得出排气系统任一点上的振动响应及排气管路长度上的振动传递率,考察其振动耦合特性;为排气系统的空间走向和结构设计提供强有力的依据。     

基于测点优化与模态扩展的机械结构振动响应全场重构EI北大核心CSCD

提出一种基于测点优化与模态扩展的机械结构振动响应全场重构方法。使用D优化设计方法确定最优测点布置方案,根据模态扩展方法构造加速度响应扩展矩阵,从而实现由优化布置的有限测点的加速度响应重构机械结构全场加速度响应,并使用有限元分析软件读取重构的加速度响应,实现机械结构响应全场可视化。开展板结构数值仿真分析和振动响应重构试验,验证了当结构处于多模态共振或非共振状态下机械结构振动响应全场重构方法的有效性和鲁棒性。进一步,通过分析各阶加速度模态贡献量,精准选择主要振动模态分析机械结构的振动响应,实现了基于更少测点的振动响应全场重构。     

6830CR1型客车怠速振动问题分析及解决方法

对怠速状态下振动过大的客车进行现场振动测试及锤击模态实验,得到整车的振动频率成分及固有特性。通过振动分析得出影响该客车振动的主要因素是发动机转动传到底盘大梁的振动,与怠速车速密切相关。并对其底盘进行结构仿真分析,经过与模态测试对比,最终确定客车振动是怠速的工作频率与车辆底盘固有频率的耦合问题,通过改变底盘局部结构合理消除共振耦合现象。     

大型豪华游艇结构振动分析与控制

通过有限单元法对某大型豪华游艇进行固有频率及强迫振动预测分析,发现上甲板左舷通往楼梯的走廊振动速度的峰值超标10%。经过频谱分析、局部结构模态分析,讨论振动的有效控制方法,通过修改局部结构以改变其固有模态、避免共振的方法进行局部结构的振动控制,使得该区域的振动情况得到有效控制,满足相关规范的要求。该研究为其他工程项目的振动控制提供一定的参考。     

Estimation of Parameters of Universal Distribution of Moments of Failure of Products

A method is proposed for estimating the parameters of a mixture of exponential and Weibull distributions for which the accuracy of preliminary estimates obtained by graphical analysis is refined in accordance with the criterion of maximum likelihood. The efficiency of the proposed method is supported by the results of statistical modeling.     

Evaluation of optical properties of highly scattering media by moments of distributions of times of flight of photons

A novel method for the determination of the optical properties of tissue from time-domain measurements is presented. The data analysis is based on the evaluation of the first moment and the second centralized moment, i.e., the mean time of flight and the variance of the measured distribution of times of flight (DTOF) of photons injected by short (picosecond) laser pulses. Analytical expressions are derived for calculation of absorption and of reduced scattering coefficients from these moments by application of diffusion theory for infinite and semi-infinite homogeneous media. The proposed method was tested on experimental data obtained with phantoms, and results for absorption and reduced scattering coefficients obtained by the proposed method are compared with those obtained by fitting of the same data with analytical solutions of the diffusion equation. Furthermore, the accuracy of the moment analysis was investigated for a range of integration limits of the DTOF. The moment analysis may serve as a comparatively fast method for evaluating optical properties with sufficient accuracy and can be used, e.g., for on-line monitoring of optical properties of biological tissue.     

Assessment of intakes of mixtures of radionuclides

Australia has several uranium mines and a large number of mineral sand mines, with associated processing facilities. Exposures resulting from these mining and processing operations usually involve intakes of mixtures of radionuclides. This work describes the development of a suite of first order, linear compartment models, based on the ICRP Publication 66 respiratory tract model, and an analytical solution to the decay equations, for assessing the consequences of such intakes. The computer programs based on these models directly compute excretion, organ retention and organ and whole-body doses for intakes of either single radionuclides or any mixture of radionuclides belonging to the same radioactive decay chain. The intake can be via inhalation, ingestion or injection, and can be acute, chronic or of limited duration. The starting concentration and degree of secular (dis)equilibrium can be specified for each radionuclide. No assumptions need to be made about the relative magnitudes of the radioactive half-lives of the different nuclides.     

Estimation of potentialities of methods of summation of direct measurement errors

Conventional methods for summation of direct measurement errors are considered. Conditions under which these methods provide consistent results are stated. It is proposed to utilize for characteristic of the total error, its interval estimator or the half-sum of the value obtained by adding up its arithmetic and geometric random errors.Translated from Izmeritel'naya Tekhnika, No. 4, pp. 10–12, April, 1995.     

空压机轴承箱蜗壳温度探头油封改造

由于空压机进气侧轴承箱蜗壳温度探头密封效果不好,使空压机及其后续管道受到油污染。后将温度探头的O形圈密封改为骨架油封,杜绝了轴承箱漏油问题。文章简介空压机的结构和技术参数,详细介绍了骨架油封的制作和优点。     

Determination of parameters of microstructural inhomogeneity of deformation of metals by the method of modeling

The article suggests a method of evaluating the microstructural inhomogeneity of deformation of metals by modeling. The method includes the measurement of deformations of metal according to meshes of a dividing grid with small base and the calculation of the distribution parameters of microdeformations in model representation. It is shown that the modeling method makes it possible objectively to evaluate the microinhomogeneity of deformation of metals independently of the chosen mesh size of the dividing grid. New structural characteristics are introduced: the base and wave of variation expressing the degree of crumbling or amalgamation of metal grains by inhomogeneity of deformation.Translated from Problemy Prochnosti, No. 7, pp. 40–44, July, 1991.     

Characteristics of mechanical properties of materials in studies of conditions of attainment of marginal states

It is shown that conditions of attainment of marginal states in the material of structural components are formulated on the basis of analysis of force and deformation criteria of formation and development of destruction. The parameters of these criteria are data on types of structural materials, standard and special characteristics of their mechanical properties, structural forms of considered elements of the equipment, and their operating stress loading. In this case, the construction of a system of state equations for describing interrelation of current damage, external actions, and responses to them is based on the concept of calculating variations in properties of materials at all stages of the design life cycle.     

Analysis of anisotropy of properties on the basis of studies of texture of coarse-grained ingots of thermoelectric materials

An analysis of anisotropy of the properties of a Bi₂Se_0.3Te_2.7 solid solution was carried out using construction of demonstrative surfaces for thermoelectric effectiveness and thermal expansion coefficients. It is shown that the texture is an important factor forming anisotropy of properties and technological fitness of ingots for manufacturing modules. Anisotropy of properties based on the studies of the ingot textures obtained using the float-zone method and Bridgman method (growing thermoelectric plates in a flat cavity) was studied.     

Analysis of the rate of propagation of the wave of change of boiling modes

An approximate analytical expression is derived for the velocity of the front of the wave of change of boiling modes on a rod and on a plate. The impact of the Thomson effect and of the heater orientation in the gravity field is included. Adequate agreement is demonstrated between the derived relations and experimental data.