用信号处理技术分析风扇的振动

本文介绍了用脉冲激励法测定风扇系统轴向振动的固有频率。应用谱分析诊断风扇叶片和电机轴质量的好坏。并提出降低风扇系统振动和噪声的方法及措施,从而提高了风扇的质量和合格率。     

电磁风扇离合器系统参数匹配设计

分析电磁风扇离合器系统振动问题及影响因子,进行影响因子灵敏度分析,从而拟定灵敏度计算公式。提出了电磁风扇离合器系统参数匹配设计方法和技术路线,并针对典型风扇离合器系统进行参数匹配设计。不仅解决原结构振动过大问题,还保证结构柔性损失小,使系统质量有所降低,取得了很好的效果。     

无霜冰箱风扇电机性能及对节能的影响

通过对无霜冰箱风扇及电机的研究,了解各种电机的种类及性能,以及电机所匹配的风扇性能,了解不同风扇下的性能变化影响因素,无霜冰箱的风道阻力设计选择,并通过冰箱性能仿真软件分析风扇及电机对冰箱节能的影响。     

冰箱压缩机橡胶垫减振系统设计因素分析

冰箱压缩机的橡胶垫可减小压缩机向冰箱的振动传递,从而降低冰箱的噪音和振动。本文从理论分析、仿真计算、及实验测试几个方研究了冰箱压缩机橡胶垫的关键设计因素。结果表明,橡胶垫的隔振效果和压缩机的质量M,旋转频率f,以及橡胶垫的刚度K和阻尼C有关。从传递力的角度考虑,K越小传递给基础的力越小,但是相对整个冰箱系统而言,存在一个最佳刚度k值使整个冰箱系统的振动和噪音最小。     

基于时间平均小波谱的汽车后桥质量检测

汽车后桥是汽车的关键部件之一，有20％的事故是由后桥造成的，因此在其出厂前要进行严格的质量检测。本文采用振动诊断方法实现了后桥的质量检测，通过采集、分析汽车后桥振动信号，应用时间平均小波谱法提取后桥的质量检测参数，根据新产品的振动能量特点，如果参数值在特征参数阈值允许范围内则产品合格，否则认为产品不合格，这种方法能够实现自动检测，更适合现代化生产的需要。     

样品检测结果符合性判定规则及风险水平

目前产品标准或相关规范对技术指标只给出了上限和(或)下限值,并未明确如何对检测结果进行判定,特别是没有考虑检测不确定度对检测结果判定的影响。简述了检测结果的符合性判定规则及相应风险水平,探讨了简单的接受/拒绝判定规则及考虑不确定度后的判定规则,根据不同情况采取不同的规则对检测结果进行符合性评定,考虑了不确定度对合格评定的影响,使得合格评定结果更科学和准确。     

冰箱侧壁振动传递路径分析试验研究

某型冰箱振动较大,为明确振源及其主要传递路径,采用振动传递路径分析方法进行测试分析,本文介绍频域法传递路径分析的原理和传递函数及激励力的测量方法,试验结果找到了对冰箱侧壁振动贡献最大的激励源和传递路径,根据分析结果对冰箱底板改进设计后冰箱侧壁振动降低,验证了传递路径分析方法对振动源识别和贡献分析的可靠性。     

冰箱的缓冲包装CAE分析

目的研究冰箱在运输过程中的振动和冲击特性。方法利用Pro/E建立冰箱缓冲包装模型,并对模型进行适当简化,然后利用有限元分析软件Ansys对冰箱缓冲包装的振动和冲击特性进行模拟分析计算。结果求出了冰箱缓冲包装的固有频率与固有振型,以及在公路运输过程中受到振动和冲击下的动态响应。结论所提出的模拟产品包装系统的振动和冲击特性的方法,不仅缩短了产品的设计周期,而且为电子产品的包装设计提供了依据。     

合格判定在时间频率计量校准领域应用研究

为避免时间频率校准工作中对被校准设备合格判定产生错误判定,通过对频率偏差参数合格判定方法的研究,针对晶振老化或原子钟频率漂移、频率复现性及测量不确定度对测量结果影响,建立3种合格判定典型数学模型,分析造成错误判定的原因并提出解决思路;采用高稳晶振、铷原子钟等典型仪器进行试验验证和数据分析。实验表明:归纳总结出的3种方法能够在实际工作中得到运用,避免产生错误判定,为时间频率计量校准工作中合格判定提供解决思路和指导方法,具有较强的指导性和应用价值。     

汽车风扇减振器振动特性设计

本文为解决某汽车风扇叶片振动断裂的问题，针对风扇减振器系统的结构特性，进行了试验模态分析和动态特性的计算。分析结果表明发动机工作转速（主激励频率）与该系统的第一阶固有频率非常接近而引起共振，导致风扇叶片断裂。据此分析结果，本文对风扇减振器进行了重新设计研究，提出了风扇城根器改讲设计方案，并运用计算机辅助设计，取得了满意的效果。     

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.     

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.     

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。     

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.     

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.     

水三相点复现的不确定度评定

水三相点是开尔文热力学温度的唯一基准点，也是ITS-90国际温标重要的定义固定点。因此，水三相点不确定度分析对整个温标的建立、温度量值传递起着至关重要的作用。近3年来，中国计量科学研究院研制出一系列高质量的水三相点容器，加强了水三相点的研究，为不确定度的分析提供了更为可靠的实验依据。同时，不确定度的分析也是客观评价新研制容器性能的一个重要指标。因此，根据实验结果对新研制容器所复现的水三相点进行了不确定度评定。评定结果表明，其扩展不确定度为0．16mK(k=2．69，P=0．99)。