基于自组装成品率的球栅阵列焊点工艺参数分析

为了提高球栅阵列焊点封装器件的自组装成品率,研究了焊点体积偏差率及焊盘直径对器件自组装成品率的影响。考虑封装器件的温度翘曲变形、焊点体积的不可避免的制造误差及焊点位置的随机性,分析了器件自组装过程。通过求解不同体积焊点的形态,得到了不同体积焊点的液桥刚度曲线。基于不同体积焊点的液桥刚度曲线,仿真分析了焊点体积偏差率及焊盘直径对器件自组装成品率的影响。结果表明,焊点体积偏差率及焊盘直径的减小会增大焊点液桥刚度曲线的公共范围,从而提高器件的自组装成品率。     

Parallel heterodyne readout of information from three-dimensional superimposed holograms

A method is proposed for parallel (simultaneous) readout of information from threedimensional “coupled” Fourier holograms. The method is based on the principle of transformation of informational degrees of freedom of the optical signal with the use of moving diffraction gratings: the spectrum of spatial harmonics of superimposed holograms is transformed to a spectrum of time harmonics separated in terms of frequency. A method of formation of images of moving gratings with a prescribed orientation in the volume of the recording material is developed. Conditions of the frequency separation of the signals, resolution of the method over the material depth, and the number of detected bits as a function of grating parameters are obtained.     

复合材料瓦面推力轴承弹性模量的研究

对复合材料瓦面推力轴承表面弹性层进行了不同温度下的整体加压和局部加压测试试验,在测得弹性层的压缩弹性模量的基础上,给出了理论弹性模量和计算弹性模量的定义,研究了载荷和温度对弹性模量的影响规律及弹性模量的取值范围,提出了以弹性层压缩弹性模量作为轴瓦整体压缩弹性模量的观点.所得结果可用于轴瓦结构设计、润滑参数计算及瓦面修形.     

Effects of dissipative forces on Coriolis flowmeter readings

An indirect measurement method based on recording the phase difference of resonance vibrations of two symmetrical halves of the flow-carrying tube is used to quantify the mass flow rate of the current fluid in Coriolis mass flowmeters (CMFs). A variant of modeling the CMF vibration system is analyzed, which allows taking into account the influence of the dissipation of oscillations of a measuring tube with fluid flowing through it on the dependence between the mass flow rate of the fluid and the phase difference recorded by the sensor. The steady-state CMF vibration mode is considered as the result of the superposition of two principal vibrations of the measuring tube. The first principal coordinate corresponds to the deformation of the measuring tube along the lowest natural mode excited by an external driving force in the resonance mode. Vibrations of the other principal coordinate correspond to deformation in a natural mode corresponding to a higher natural frequency than the frequency of the exciting force. The relationship of the amplitudes of the principal coordinates is established on the basis of the gyroscopic coupling of the principal vibrations that occurs when a fluid flows through a tube. The coefficients of gyroscopic coupling are determined as a result of 3D finite-element simulation of the steady-state vibration mode of the measuring tube with a flowing fluid. The simulation is performed for five variants of the shape of the axis of the measuring tube, taking into account the distribution of the gyroscopic forces of the flowing fluid. Quantitative estimates of the influence of dissipative forces on the flowmeter readings are obtained on the example of dissipative forces of linear viscous friction. A comparison of the CMF simulation results for different tube axis shapes demonstrates how the phase shift arising in the vibration system is affected by the dissipation level and the proximity of the natural frequencies of the flowmeter measuring tube at a fixed mass flow rate of the fluid.     

Effect of the parameters of a material on the surface displacements caused by waves propagating in a layer

The amplitude—frequency characteristics of the vibrations of the surface of a free elastic layer are determined. These vibrations are caused by propagating Lamb waves under the action of a normal surface load. The changes in the spectra of surface displacements and in the tangential-to-normal displacement-amplitude ratios during changes in the Poisson ratio are studied. Studying the spectrum of surface displacements of an elastic layer is of interest owing to the necessity of discriminating modal components of the wave field [1] and as one of possible methods for determining some of the parameters of a material. The ratio of the amplitudes of the horizontal and vertical displacements as a function of the frequency of a vibration source is sensitive to the Poisson ratio of the material and the conditions of the contact with the base. The amplitude-frequency characteristics of the surface displacements of an elastic isotropic layer are plotted and compared to those obtained in the case of a layer that is in contact with a rigid base.     

Dependence of the results of classification of multispectral images of forest vegetation on wavelet-transform parameters

The problem of classification of space multispectral images of forest vegetation is considered. Features based on the wavelet transform and a classification method involving consideration of the importance of each feature are investigated. Dependence of the classification results on the wavelet function, the level of the transform, and the parameter of the classification method — the number of segments of the range of features — is given. Results of classification of multispectral images of six classes of forest vegetation in images obtained by a Rapid Eye shooting system are presented.     

双列调心凹面滚子轴承接触载荷分析

在考虑滚子与套圈、滚子与保持架以及保持架与引导套圈作用力的条件下,建立双列调心凹面滚子轴承动力学模型。以某双列调心凹面滚子轴承为研究对象,与静力学分析模型滚子最大接触载荷计算结果对比,验证了模型的正确性。并分析了工况条件(轴向载荷、径向载荷、倾覆力矩、转速)和结构参数(滚子数量、滚子长度、径向游隙)对滚子最大接触载荷的影响,结果表明:随轴向载荷增大,一列滚子受力增大,另一列滚子受力减小;随径向载荷增大,滚子最大接触载荷增大;随倾覆力矩增大,2列滚子接触载荷几乎不变;随转速增大,滚子最大接触载荷增大;随滚子数量增多和滚子长度增加,滚子最大接触载荷减小;随径向游隙增大,滚子最大接触载荷呈先减小后增大趋势。     

基于UG的立铣刀铣削力的有限元分析

为提高加工精度,对立铣刀的应力场进行了有限元分析。通过铣削力试验,对不同切削参数下立铣刀的铣削力进行动态采集,利用UG中的建模模块进行立铣刀实体建模,根据切削力实验结果给出了边界条件,在立铣刀有限元模型上进行加载,利用UG有限元分析模块,获得了立铣刀切削过程中切入、切出的瞬时应力场云图,显示了切削中铣刀片应力场的变化规律。     

利用协同优化方法实现复杂机械系统的设计优化

利用协同优化方法实现了四辊轧机机座的结构参数设计优化。根据多学科设计优化对复杂系统进行设计优化的思想，提出将复杂机械系统分解为若干个简单的子系统进行设计优化。协同优化是近年来发展较快的一种多学科设计优化算法，描述了应用于复杂工程系统优化设计的协同优化方法。在协同优化的系统级优化中，引入松弛变量，将一致性等式约束转化为不等式约束，松弛变量的取值影响系统级优化的收敛速度。通过对四辊轧机机座的结构参数设计优化，给出了利用协同优化方法进行复杂机械系统设计优化的一般思路，为解决更为复杂的机械系统的设计优化问题打下了基础。算例证明了协同优化算法解决复杂机械系统设计优化问题的有效性。     

基于支持矢量聚类的机械故障诊断

针对无监督的支持矢量聚类方法由于样本类别数量未知带来的模型参数难以选择的问题,提出有监督的支持矢量聚类方法,并应用到机械故障诊断中.该方法首先以聚类区域个数及支持矢量个数作为模型参数的选择准则,以支持矢量为核估计样本分布的概率密度,并根据概率密度估计值选择不同聚类区域的类别代表样本,而后引入k近邻法实现对不同故障的分类.对测试样本的分类结果表明了该方法的有效性.     

曲线半径及轴重对轮轨摩擦功影响的研究

基于非Hertz滚动接触理论利用数值计算方法详细分析了静态接触情况下,轴重和曲线半径对轮轨接触质点间等效应力、接触斑粘滑区的分布、总滑动量和摩擦功的影响。分析计算表明,轴重增加引起轮轨接触质点间等效应力,接触质点间粘滑区的面积以及总滑动量的变化,同时对轮轨接触质点阍的摩擦功的变化有重要影响;小曲线半径处轮轨接触质点间的总滑动量,接触斑滑移区的面积以及摩擦功都明显增大,导致曲线上钢轨磨损加剧。因此曲线半径和轴重是影响轮轨滚动接触磨损的重要因素。     

The dynamic stability of a crane standing on soil during the rotation of the boom

In this work the influence of flexible soil foundation on the dynamic stability of the boom crane is presented. This analysis was made during the rotation of the boom, such that variable pressure on the soil and other deformations could be taken into account. The rheological deformation of the soil as a function of the changing strain in time has been described by an equation, which is the Duhamel integral. After accepting the discrete model of the considered system dynamic equations of motion were elaborated, which because of their nonlinearity and complexity were solved numerically. Appointed were the dynamic displacements of each of the supports for different rotational speeds of the boom, showing the influence of the rheological deformation of the soil on the behaviour of the whole crane. As well the trajectories of the motion of the weight hoisted were presented for different rotational speeds of the boom, which enabled the analysis of the precision of the positioning of the weight being hoisted (minimization of oscillation).     

Distribution curves of sectional areas through some families of convex particles

We outline the results of a computer program which calculates frequency distributions of functions of cross-sectional regions of convex planar-faced polyhedra, ‘sphero-polyhedra’, and populations of perturbed polyhedra. This is done by ‘cutting’ a computer representation of the figure by a large number of random planes. The procedure is applied to cubes, dodecahedra, truncated octahedra, and approximate β-tetrakaidecahedra. Certain aspects of the shape of the object, e.g. sharpness of corners, angularity, compactness, and degree of symmetry are related to aspects of the shape of the distribution curves, e.g. beginning and ending points of the curves, rate of rise of the peak, relative location of the peak, and height and width of the peak.     

摆动平底从动件凸轮廓线曲率半径计算的新方法

摆动平底从动件凸轮机构经高副低代后 ,得到等效的导杆机构。利用三心定理及弗列登斯坦定理对等效的导杆机构进行运动分析后 ,可以得到确定凸轮廓线曲率半径的图解法。本文在图解法的基础上应用矢量运算法则推导出了摆动平底从动件凸轮廓线曲率半径的计算公式 ,分析了机构的主要尺寸及从动件的运动参数对曲率半径的影响 ,并通过实例验证了该曲率半径计算公式的正确性     

The analysis of polarized light using a stereographic projection of the Poincaré sphere

The mathematical analysis of a beam of polarized light into two constituent beams of plane-polarized light vibrating at right angles to each other and with a difference of phase, can be somewhat time-consuming. This paper describes a graphical method of solution, of reasonable accuracy, which can be carried out rapidly. The simple geometry of the representation of a polarized beam as a point on the surface of the Poincaré sphere is explained together with the stereo-graphic projection of the surface of the sphere on a diametral plane. Examples are given of the use of the stereogram in conjunction with the polarizing microscope for the determination of phase difference of a transparent crystal, for the determination of the state of polarization after transmission through a bire-fringent crystal and for the analysis of superimposed crystals.     

Technical condition control calculation for hazardous industrial facilities

A formula for calculation of inspection times of monitoring the technical condition of a hazardous industrial facility, as well as a formula for calculation of the number of operation intervals between monitoring events depending on certain values of parameters of reliability of the facility were demonstrated. In addition, the monotonic behavior of the duration of equally possible operational intervals between monitoring events for facilities with monotonic changes in fault occurrence intensity was defined. A monotonic behavior in values of probabilities of flawless performance of the facility within intervals between monitoring events with equal duration of operation and monotonic change in intensity of faults occurrence were demonstrated.     

GB15563《震源药柱》2006版修订内容

新标准GB15563-2006《震源药柱》在95版基础上有较大变化,扩大了适用范围;根据目前震源药柱的生产和使用情况,对震源药柱进行了重新分类;对部分产品性能指标的要求进行了调整;对震源药柱壳体颜色重新进行了规定;补充完善了爆速测试方法;增加了抗水性能和抗拉性能试验装置示意图;对震源药柱的编码方式进行了统一规定;对检验项目和抽样方案进行了调整;增加了包装检验的内容[3]。     

Studying thermal state of friction pairs of multidisc brake

A dimensionless heat problem for a friction pair of a multidisc brake was formulated under conditions of a linear decrease in the friction power of discs with time. Thermal state of friction pairs of the multidisc brake under load and velocity conditions of the friction of the discs that simulate service brakings of a wheel tractor was experimentally and theoretically studied. The validity of a mathematical model of the temperature field in the discs of the brake has been experimentally confirmed and functional dependences of the maximum temperature of friction surfaces of the discs on values of the main performance parameters have been obtained.     

Material testing by plotting total deformation curves

The paper deals with the theoretical and experimental aspects of the study of the behavior of materials at the stage of supercritical deformation or work softening, consideration of which is important for the assessment of the durability of structures. The study results show the theoretical confirmation of the effect of the specimen configuration on the possibility of plotting the descending portions of deformation curves. It is shown that the equilibrium supercritical deformation of a material is possible if the stiffness of the loading system is sufficient. This is confirmed by the results of the uniaxial tension tests with unloading at various stages of elastoplastic and supercritical deformation. The method for interpreting experimental data obtained for the specimens of various dimensions under conditions of deformation localization are considered.