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.     

Study on energy dissipation pattern in vibrating fluid filled cylindrical shells with a constrained viscoelastic layer

The modal strain energy method is used to study the energy dissipation pattern in vibrating cylindrical shells with a viscoelastic damping layer, for various circumferential and axial modes. The effect of tank size, boundary condition and height of contained fluid on the distribution pattern is also investigated. The regions of energy dissipation concentration are identified. The effect of redistribution of the (initially uniformly distributed) constrained viscoelastic material by concentrating it in the above regions is studied.     

基于信牌驱动模式的工作流柔性建模的研究

目前大多数工作流系统都不能支持动态可变的柔性特征,而支持动态可变的柔性工作流系统是人们在实际应用中对工作流系统提出的新要求,也是企业为了满足业务流程变更的需要.提高工作流系统的柔性需要从工作流的建模、系统设计等各方面去努力.在协同信牌驱动工作流模式模型的基础上引进了适合该模式的柔性建模的元模型,并且提出了限制该模型的一些规则来讨论基于该模型的柔性建模工作流系统的实现.     

Changing the role of the air traffic controller: how will free flight affect memory for spatial events?

At present, air traffic controllers (ATCOs) exercise strict control over routing authority for aircraft movement in airspace. The onset of a free flight environment, however, may well result in a dramatic change to airspace jurisdictions, with aircraft movements for the large part being governed by aircrew, not ATCOs. The present study examined the impact of such changes on spatial memory for recent and non-recent locations of aircraft represented on a visual display. The experiment contrasted present conditions, in which permission for manoeuvres is granted by ATCOs, with potential free flight conditions, in which aircrew undertake deviations without explicit approval from ATCOs. Results indicated that the ATCO role adopted by participants impacted differently on short-term and long-term spatial representations of aircraft manoeuvres. Although informing participants of impending deviations has beneficial effects on spatial representations in the short term, long-term representations of spatial events are affected deleteriously by the presentation of subsequent information pertaining to other aircraft. This study suggests strongly that recognition of the perceptual and cognitive consequences of changing to a free flight environment is crucial if air safety is not to be jeopardized.     

Multivariable frequency-response curve fitting with application to modal parameter estimation

This paper presents a computational approach for the frequency-domain identification of multivariable, discrete-time transfer function models based on a cost function minimization. The algorithm is optimized for the parametric characterization of complex high-order multivariable systems requiring a large number of model parameters, including sparse matrix methods and QR-projections for the reduction of computation time and memory requirements. The algorithm supports a multivariable frequency-dependent weighting, which generally improves the quality of the transfer function model estimate. The overall approach is successfully demonstrated for a typical case encountered in experimental structural dynamics modelling (using modal analysis) and compared with related algorithms in order to assess the gain in computational efficiency.     

陀螺稳定平台的有限元模态分析

陀螺稳定平台是制导武器的核心部件之一,平台结构性能好坏直接影响制导武器的工作精度和可靠性.应用有限元模态分析理论,对该平台的结构动态特性进行研究,目的是为对平台进行结构动力学修改和结构优化设计提供依据,以便提高平台的工作精度和可靠性.运用uG建立某陀螺稳定平台的三维实体模型,进行合理简化后,建立该平台的有限元模型.采用有限元数值计算方法,计算得到该平台前七阶模态的频率及振型,各阶模态的频率均满足要求.并提出了改善该平台结构动态性能的措施.     

The role of actual modal-contributions versus frequency to optimize the structure

In modal frequency response analysis, the dynamic analyst is often faced with the structure’s dynamic behavior, the modal contributions included, over a frequency window rather than at a single frequency. Therefore a new method in modal frequency response analysis has been developed for computing both complex modal-contributions and real, actual modal-contributions over a frequency range. Contributions from normal modes to displacement, velocity, or acceleration of a set of selected evaluation points (grid-component combinations) are considered. The focus lies on identifying the major actual-contributions from normal modes and the frequency range they are active in. The method is valid for all branches of mechanical engineering. With the thorough knowledge of the dominant modal-contributions to the physical motion response of relevant structure locations and the modal contributions’ frequency history, the traditional design process can substantially be enhanced. It is worthwhile to notice that by the use of the presented procedure the dynamic analyst may find innovative redesigns which the automatic structural optimizers are not able to find. Examples are given to demonstrate the application, the strength of the coupling between modes, the influence of base and force excitation on the modal contributions and, finally, some recommendations on how to reduce undesired structural responses.     

应变式呼气流量传感器的有限元模型与动态特性

应变式呼气流量传感器利用应变电桥对人的呼气流量进行测量。为实现对变化呼气流量的正确测量,该传感器在工作频带范围内必须满足无失真测量条件。用有限元分析软件ANSYS建立了该传感器的有限元模型。对该模型进行模态分析得出了它的前四阶振型和固有频率。对该模型进行谐响应分析,得到了该传感器的幅频特性曲线和相频特性曲线。通过分析这些仿真结果得出了该传感器在工作频带范围内符合无失真测量的条件,能对人的呼气流量进行正确的测量。     

泛组合运算模型研究

泛逻辑学是在模糊逻辑的基础上,分析命题之间关系的连续可变性。提出了“广义相关性”和“广义自相关性”两个重要的概念,将命题连接词运算模型定义为由相关性所控制的算子簇,实现了命题连接词运算模型的柔性化。其中泛组合运算模型是为了满足连续值逻辑中综合决策的需求而提出的。目前仅有二元模型,在实际应用中迫切需要多元模型。但由于泛组合问题的复杂度随着“元”的个数增加而急剧增大,其设计有一定的难度。提出了多元泛组合运算模型和生成元加权零级泛组合运算模型,从而不仅满足了应用中多元综合决策的要求,还进一步完善了泛逻辑学中的命题连接词理论。     

第一运输机的振动研究及其链轮的结构分析

运输机振动将产生噪音,导致机器运行失常,无法正常运行,更为严重的是运输机的振动将导致刮板链的断裂,造成严重的人员伤亡和巨大的经济损失。本文介绍第一运输机产生振动的原因以及应用ANSYS软件对运输机上刮板链的链轮进行静力学和动力学模态分析,验证链轮设计是否合理以及求得其固有频率及振型,从理论模型和动态仿真两部分说明其合理性,为整个机构设计提供合理依据。     

A coupling algorithm for partitioned solvers applied to bubble and droplet dynamics

Bubbles and droplets both consist of a liquid in contact with a gas. In this paper, we consider the interface between the incompressible liquid and the gas as a zero thickness structure. The position of the interface is determined by the equilibrium between surface tension effects and the fluid pressure difference across the interface. So, the structure interacts with the fluids on either side. The behaviour of a limited number of bubbles and droplets can therefore be simulated as a Fluid-Structure Interaction (FSI) problem.Most existing techniques frequently used for studying bubble and droplet dynamics, such as Level Set or Volume Of Fluid, use monolithic schemes. The flow on both sides of the interface and the position of the interface are calculated in a single code. In this contribution, a partitioned approach is presented. The position of the interface is calculated with a structural solver. Given a displacement of the interface, a separate flow solver calculates the flow on the liquid side of the interface with the Arbitrary Lagrangian-Eulerian (ALE) technique. The structural solver uses a reduced order model of the flow solver to obtain implicit coupling between both solvers. This reduced order model is built up during the coupling iterations of a time step. Grid and time converged solutions of two axisymmetric problems are calculated: an oscillating water droplet in air and the growth and detachment of an air bubble from the outlet of a vertical needle, submerged in quiescent water.     

Analysis of the dynamic behaviour of a torsional micro-mirror

In this paper, the results of the dynamic pull-in voltage characteristics of a micro-mirror using electrostatic actuation are analyzed. Based on torsional dynamic theory, appropriate equations are developed that allowed to give insight into the actuating voltage, switching time and other dynamic parameters. The analytical results are discussed in detail without and with considering air squeeze film damping, respectively. This is equivalent to assuming the mirror is operated in vacuum or at ambient pressure. When the effect of the damping is considered, the movement trajectory of the cantilever beam is changed, and the calculated results of the pull-in voltage and switching time are considerably different compared to those without considering damping. Therefore, the effect of the air squeeze film damping is an important factor in the design and fabrication of micro-electro-mechanical systems. Finally, the experimental results in the air environment are discussed and compared to the theoretical analysis.     

摩托车车架动特性计算机仿真分析

摩托车车架的动特性是摩托车振动舒适忡的一个重要影响因素,采用计算机仿真分析方法进行摩托车车架动特性分析能有效的减少试验费用,缩短产品开发周期。该文基于某摩托车车架的二维图纸和实物,首先利用UG软件进行几何建模;然后用MSC．PATRAN／NASTRAN软件建立其有限元模型,并进行了自由模态的计算机仿真分析;最后利用LMS实验模态分析系统对该车架进行了实验模态分析,验证了计算机仿真结果,结果表明仿真精度较高,可将二者相结合以分析车架的振动特性。     

基于有限元的客车车身的静动态特性分析

随着客车需求的日益增加,制造企业通过降低开发成本、缩短开发周期、改进产品性能提高产品竞争力。科学合理的应用计算机辅助技术是参与竞争的有力手段。以某集团NJ6826TMF型客车为对象,联合应用多种CAD软件,研究骨架的建模技术;应用分析软件ANSYS对它的典型工况进行静态和模态分析,提出修改该骨架结构的建议;验算表明,修改建议是合理的。文中壳元建模的应用彻底克服了梁元算法的弊病。     

MODES: A FORTRAN IV program to calculate modal analyses from raw point-count data

Program MODES is a FORTRAN IV program to calculate modal analyses of thin sections from raw data obtained by any normal point-counting technique. The program provides a table listing the modal analyses, quartz-feldspar-rock fragments (QFR) ratios, matrix-labiles-quartz (MLQ) ratios, ratios of plagioclase to total feldspar (P/F), ratios of volcanic lithic fragments to total lithic fragments (V/L), frequency, estimate, and confidence limits for each sample, and calculates the means and standard deviations for each component in a group of samples. It also prints a triangular diagram of the QFR or MLQ ratios. The program is useful where large numbers of modal analyses are determined because it requires no manual calculations, but it also has been determined useful when only a few samples are involved.     

基于ANSYS的压电圆片振子径向振动模式分析

压电陶瓷问世不过几十年,然而发展非常迅速,压电陶瓷振子的应用日趋广泛.为了更深入研究压电振子的特性,在ANSYS的软件平台上,对压电圆陶瓷片振子进行建模仿真;利用有限元分析方法,得到压电圆陶瓷片的多阶振动模式.再根据谐振理论,对其输入导纳-频率关系进行分析.结合模态分析结果文件进行筛选,得到了压电陶瓷圆片径向振动频率,最后通过理论分析和实验测试,验证了仿真值比理论值更接近测试值.相对传统的振动模式分析方法,此方法更为简单、准确、直观.     

Development of a sensor for surface state measurements using experimental and numerical modal analysis

The characterization of the surface state becomes an increasing necessity for many industries. This paper presents a patented measurement method [M.A. Bueno, S. Fontaine, M. Renner, Dispositif Pour Évaluer L’état de Surface d’un Matériau et Procédé de Mise en œuvre Dudit Dispositif, Patent No. PCT/FR01/01770, 2000], which is able to evaluate the surface state of materials. This method gives roughness–friction criteria and is based on the principle of a tribometer of type “blade-disc”, where the analysed surface is the disc. The sensor is an active element, which vibrates according to its vibrating modes. This work shows how experimental and numerical analysis has allowed optimizing its gage instrumentation and its geometry. Moreover, the modal analysis and the building of a numerical model have set up the coupling between mechanical solicitations of the tested surface and mechanical responses of the sensor in each mode. Finally, an example of measurement of known surfaces is illustrated to explain the results of this study and the efficiency of this measurement method.     

Retrieval of textured images through the use of quantization and modal analysis

This paper proposes a new method for textured image retrieval, by the modal analysis of quantized spectral point patterns as the modal correspondence method of Shapiro and Brady, to match point sets by comparing the eigenvectors of a pairwise point proximity matrix taken from the power spectrum peaks. A variant of the Carcassoni, Ribeiro and Hancock method for performing recognition is taken into account. For choosing image features to represent an image, a quantization scheme is applied. This quantization scheme acts in the spectral space given by the Fourier transform of each image. Its goal is to find a small set which represents an image efficiently, where the most important features are presented. The proposed technique is invariant to rotation and is robust in the presence of noise and damaged images. The techniques here presented are compared, and the commonly used retrieval performance measurement—precision and recall—is used as evaluation of the query results.     

Conditional bivariate probability function for source identification

In this paper a new receptor modelling method is developed to identify and characterise emission sources. The method is an extension of the commonly used conditional probability function (CPF). The CPF approach is extended to the bivariate case to produce a conditional bivariate probability function (CBPF) plot using wind speed as a third variable plotted on the radial axis. The bivariate case provides more information on the type of sources being identified by providing important dispersion characteristic information. By considering intervals of concentration, considerably more source information can be revealed that is absent in the basic CPF or CBPF. We demonstrate the application of the approach by considering an area of high source complexity, where many new sources can be identified and characterised compared with currently used techniques. Dispersion model simulations are undertaken to verify the approach. The technique has been made available through the openair R package.     

某经纬仪垂直轴系刚度分析

光电经纬仪垂直轴系由于负荷重、转动惯量大,其刚度将直接影响经纬仪的跟踪性能,所以其方位谐振频率显得更为重要,针对这种情况,在与传统的仿真分析软件MSC.patran进行对比的情况下,采用了三维建模软件UG NX4.0自身集成的建模仿真一体化功能对经纬仪垂直轴系进行了模态分析,得到了垂直轴系前三阶固有频率及振型,仿真结果满足实际工作需要,并且找到了刚度薄弱环节,能够指导以后的优化设计工作.并通过实验实测方位转动谐振频率,与仿真分析结果进行比对,验证了仿真分析方法的可行性.