虚拟仪器技术及计算机辅助教学

本文分析了虚拟仪器技术,概括了虚拟仪器特性,讨论虚拟仪器的硬件平台和软件开发平台及其进展情况。最后从虚拟仪器技术支撑角度阐述计算机辅助教学。     

一种可视化自动测试环境中的虚拟仪器技术

本文讨论了一种通用的可视化自动测试环境中的虚拟仪器的实现技术。该环境采用面向对象设计方法设计了虚拟仪器的面板及控件;设计了虚拟仪器管理器以管理虚拟仪器数据库。本文的最后通过一个例子说明了虚拟仪器在可视化自动测试环境中的具体实现方法。     

岩石模型大型虚拟仪器库开发系统

介绍了岩石模型的概念,在分析岩石模型大型虚拟仪器库库中资源的基础上,为实现虚拟仪器的自动拼搭引入了智能系统的概念,建立了该虚拟仪器智能开发系统的模型和结构。提出了在该虚拟仪器库中实现自动拼搭的具体方案,包括库中资源的分层管理方法,虚拟仪器智能开发系统规则集的建立方法,系统的输入输出值的确定,最后引入神经网络,即可实现虚拟仪器的智能拼搭。虚拟仪器的自动化拼搭能极大程度地降低虚拟仪器的开发要求,并能对虚拟仪器的推广起到一定的促进作用。     

基于实例推理的虚拟仪器设计方法研究

根据虚拟仪器软件系统的特点,论述了基于框架的虚拟仪器软件系统的实例表示方法和实例库的建造方法,在此基础上,提出了基于实例推理的虚拟仪器设计方法,该方法充分利用已有的虚拟仪器设计方案和组件资源,实现了虚拟仪器软件资源的重用,提高了虚拟仪器的设计效率。     

虚拟仪器技术及其在切削加工过程中的应用

近年来,随着计算机技术的发展,虚拟仪器成为了测试控制领域的一个重要工具。通过列举虚拟仪器的应用实例概述了虚拟仪器技术的发展现状,提出了虚拟仪器在切削加工过程中的设计方法。     

测试系统的虚拟仪器设计

本文介绍了虚拟仪器的概念、软硬件结构体系、工作原理、特点和应用,从虚拟仪器的设计思想出发,通过一套基于多功能数据采集卡(DAQ)的虚拟仪器构建方案,说明虚拟仪器软硬件方面的设计思路．体现虚拟仪器的测试仪特征。虚拟仪器的不断发展及应用表明基于微计算机的虚拟仪器系统将会逐步取代传统的测试仪器。     

虚拟仪器及其在切削力测量中的应用

本文根据虚拟仪器的发展背景,详细介绍了虚拟仪器系统的软硬件组成,并根据硬件组成的不同对虚拟仪器进行分类,然后综述了虚拟仪器的发展现状和未来的发展趋势。结合切削力测量在切削数据采集和分析以及切削机理研究和切削过程监测中的重要性,简要论述了虚拟仪器在切削力测量应用中的优越性,并归纳总结了利用虚拟仪器在切削力测量中所做的研究和发展现状。     

虚拟仪器--高校实验室设备的发展方向

本文介绍了虚拟仪器的系统构成及开发环境，并分析了虚拟仪器的特点、在比较虚拟仪器和传统仪器的基础上得出了虚拟仪器更适合于高校实验室的结论。     

虚拟仪器及机械振动虚拟测试

介绍了虚拟仪器的构成及其工作原理,阐述了以计算机硬件平台为基础的虚拟测试系统,并概述了虚拟仪器的特点。同时介绍了机械工程上常用的机械振动测试虚拟仪器系统的硬件构成和相应的虚拟仪器。     

基于PC的虚拟仪器技术

文章阐述了虚拟仪器的概念、特点、组成 ,重点讨论了研究开发虚拟仪器所用的软、硬件平台及其特点 ,文章还介绍了虚拟仪器的应用和发展趋势。     

Thermally-driven nanoscale pump by molecular dynamics simulation

The feasibility of a device is studied that drives a fluid in nanoscale channel using a phenomenon called thermal transpiration, where the fluid is set in motion by a temperature gradient in the fluid-solid interface. Four different types of systems are considered using the Molecular Dynamics Simulation. They differ mainly in channel configuration and the way the gradient is applied. The simulation results show that the design of the device has major technical obstacles. One is a difficulty in imposing a sufficiently-large temperature gradient in the small scale. In this case, the feature like thermal-contact-resistance at the interface needs to be included in design considerations. The second is a limited flowdevelopment under an increased viscous drag in the narrow channel. One of the considered systems proves to be effective in a pumping operation. The system is based on a unit that repeats itself periodically in the system. The unit is composed of two regions: one that drives a fluid by thermophoretic force and the other that guides the fluid smoothly with little thermophoretic force. The latter region is made of a thermally-insulating, weakly-interacting solid.     

Detection of minute signs of a small fault in a periodic or a quasi-periodic signal by the harmonic wavelet transform

If a machine in operation has a fault, signs of the fault appear in the monitored signal and are usually synchronised with the operating speed. The signs are very small when the fault is at an early stage. The fast Fourier transform (FFT) is often utilised to detect these signs, but it is very difficult to detect minute signs. In this paper, harmonic wavelet transform is utilised to detect the minute signs of small faults in a monitored signal. The monitored signal of a machine element, in ordinary operation, is regarded as periodic or quasi-periodic. It is important for the effectual detection of the minute signs to reduce the obstructive noise and the end effects in the signal. The end effect is a peculiar phenomenon to wavelet transform and hampers effective detection. Useful methods to reduce the obstructive noise and the end effects are devised herein by the authors. Even if no visible information pertaining to a fault appears in the monitored waveform, the present method is able to detect a minute sign of a small fault. It is demonstrated that the present method is capable of detecting minute signs arising from slight collisions caused by a loose coupling and a fatigue crack.     

Modeling and experiments on eddy current damping caused by a permanent magnet in a conductive tube

Eddy currents are induced when a nonmagnetic, conductive material is moving as the result of being subjected to a magnetic field, or if it is placed in a time-varying magnetic field. These currents circulate in the conductive material and are dissipated, causing a repulsive force between the magnet and the conductor. With this concept, eddy current damping can be used as a form of viscous damping. The present study investigates analytically and experimentally the characteristics of eddy current damping when a permanent magnet is placed in a conductive tube. The theoretical model of eddy current damping as the result of a magnet in a copper tube is developed from electromagnetics and is verified from experiments. The experiments include a drop test whereby a magnet is dropped in a copper tube to measure the damping force in a steady-state, and a dynamic test is used to measure the same phenomenon in a dynamic-state. The drop test shows that the present model can accurately predict the force of steady-state damping. From the dynamic test, although predictability is not accurate at high excitation frequencies, the present model can be used to predict damping force at low excitation frequencies.     

数控加工半实物仿真系统的研究与开发

介绍数控加工半实物仿真系统的设计思想与开发方法.该系统由软件和硬件两部分组成.硬件包括一台PC计算机和一个半实物数控操作面板,用于模拟对数控机床的操作控制;软件系统以VC 6.0以及OpenGL为平台开发而成,可通过三维图形方式仿真出机床在切削中的各种运动与过程.与传统的纯软件仿真模式相比较,该半实物仿真系统提高了实践性,具有更加真实的操作性.     

An Optical Interferometry System for Measuring Three-Dimensional Displacements

The system is a combination of a Moiré interferometer (which measures the displacement in the plane of a sample) and a Twyman–Green interferometer used for measurements in the perpendicular plane. The diffraction grating that is applied to the sampleis also used as a beam splitter. As a result, the system is simple in design and easy to adjust, and its sensitivity is higher than that of a two-grating Moiré interferometer by a factor of two. The fringe pattern is distinguished by its high contrast and spatial resolution. The system has been tested in measuring the three-dimensional thermal deformation of microelectronic devices.     

Automated fixture configuration using projective geometry approach

The geometric and topological specification of a workpiece boundary is usually represented in a specific data format in a CAD database. To retrieve a set of workpiece data, to analyse its shape in addition to the machining requirements, and to determine the proper fixture configuration accordingly, are not trivial tasks when a part has a complicated shape. The real challenge is to recognise and synthesise the shape of a workpiece from its data representation. Consequently, the decision for fixturing can be made when the shape of a workpiece and the relationship of the shape and the fixturing configuration can be derived by a systematic methodology. In this paper, a projective spatial occupancy enumeration (PSOE) approach is applied as a representational and manipulating scheme for developing algorithms in automatic fixture configuration. The workpiece is projected onto the working plane of the fixture baseplate. A 2D projection is defined as a matrix of cells which can represent a workpiece with an arbitrary shape. Using a discrete search based upon the matrix of cells, the fixture types and their locations are generated according to a set of heuristic algorithms. This work is a generalisation and extension of previous works for prismatic parts. The same methodology is equally applicable in general robot grasping.     

Simulation on the motion of crankshaft with a slant crack in crankpin

A new model for vibration analysis of a crankshaft with a slant crack in crankpin is proposed, and the influence of crack depth on the transient response of a cracked crankshaft is investigated. A slant cracked shaft element is developed by deducing the local flexibility due to a slant crack. The frequently occurred slant crack in crankpin is studied, and a new finite element model of crankshaft including the slant crack in crankpin, which combines the slant cracked shaft element and Timoshenko beam elements, is derived. The support of engine block and the switching behaviour of the crack are considered, and the non-linear equation of motion for cracked crankshaft-bearing system is set up in a rotating coordinate system. The motion of a crankshaft of a four in-line cylinder engine with and without an initial crack is simulated. The influence of the crack depth on the transient response is investigated. The numerical simulation demonstrates that the current model is valid for simulating the motion of cracked crankshaft system. The results show that a useful foundation is laid for crack detection of crankshaft.     

A high-voltage pulse generator for electric-discharge technologies

The electric circuit and design of a high-volta ge pulse generator with an output voltage of ≥3 50 kV is described. The generator operates in the nanosecond range of pulse durations (~300 ns) at a repetition rate of up to 10 pulses/s in a continuous mode and is intended for electric-discharge technologies. The energy stored in the generator is ~600 J, and the energy released in a pulse is ≥300 J. A discharge of a capacitive storage through a toroidal pulsed transformer and a discharge gap is used in the generator.     

声致发光技术进展与应用前景

声致发光现象是指当液体受到强大声波作用时,液体中会产生一种"声空化"现象。即在液体中产生气泡,气泡瞬间缩小到一个非常小的体积,在此过程中会发出瞬间闪光并伴随释放大量的热量。声致发光作为声学和光学的交叉学科引起了很多人的兴趣。本文对声致发光这种奇特的现象进行系统评述,讨论声致发光的几种机理,介绍单泡声致发光和多泡声致发光的研究进展以及各领域最新研究成果,并对声致发光未来的发展及应用前景作出展望。     

碳纤维复合材料(CFRP)钻孔出口缺陷的研究

对碳纤维复合材料(CFRP)钻孔出口的缺陷进行了试验研究,对其典型形式进行了模型总结,指出孔出口缺陷由撕裂和毛边两部分组成,其中撕裂比毛边的尺寸大。撕裂的形成过程包括两个作用阶段即横刃作用阶段和主切削刃作用阶段,其中横刃作用在撕裂形成中占主导成份。毛边缺陷通常出现在表层纤维被“顺向”切削的孔边缘部分。另外,以孔出口两侧撕裂长度平均值作为撕裂评价参数,在总结钻削试验结果的基础上探讨了钻削参数变化对撕裂大小的影响。指出随着进给速度、进给量、钻头直径和轴向力等因素的增大,撕裂缺陷将变得严重;钻头转速的增大将使撕裂值变小;将切削速度与进给速度比值控制在3000-4000以下,可以有效地减小撕裂值。