Fundamental frequency and testing mode of complicated elastic clamped-plate vibration

Aimed at the modal analysis of complicated elastic clamped-plates, a trigonometric interpolation method of conformal mapping is applied to set up the mapping function between a complicated region and a unit dish region, and the fundamental frequency of the complicated vibrating region is analyzed with the help of the Galerkin method. Taking an elastic rectangle-plate with arc radius as an example, the testing mode frequency band of plates is determined by analyzing the fundamental frequency; meanwhile, according to hamming testing method of multi-point excitation to the single-point response, and by signal processing technology and its software programming, modal parameter recognition of the elastic clamped-plate is completed. Comparing the first order modal frequency with the theoretical fundament frequency, the validity of the testing mode method and theoretical analysis are verified.     

高频加热-红外线吸收法测定石灰石样品中硫含量

石灰石样品熔融时分解产生的氧化钙对硫有很强的吸附能力,而且极容易吸水。分析用坩埚主要成分是二氧化硅和三氧化二铝,而且表面有粗糙的微孔容易吸附空气中的二氧化碳和水汽。本文采用高频加热方式燃烧石灰石样品,红外线吸收法测定硫含量,确定了仪器分析的最佳条件、坩埚与样品的预处理方法、合理的称样质量、适宜的助熔剂与加入方式。通过对不同石灰石标准样品分别进行测定,测定结果与标准值基本一致,相对标准偏差(RSD,n=10)小于3.50%,实验结果表明,本方法测定结果准确可靠,有效解决了样品和坩埚因为吸附作用影响硫含量分析结果不稳定的问题。     

高速切削在特种防护橡胶内衬加工中的应用

橡胶材料具有显著的高弹性和粘弹性 ,传统的切削加工方法很难得到良好的加工表面。本文分析了线形非晶态高聚物材料的力学状态和动态力学性能频率谱 ,在此基础上研究了橡胶材料的加工机理 ,并在高速加工中心上进行了切削加工试验 ,取得了很好的效果。研究成果将为该材料在武器装备上的应用打下基础。     

衬胶蝶阀的加工及试验

介绍了金属表面衬胶的几种方法，论述了衬胶表面的切削加工及刀具的选择，阐述了衬胶蝶阀开关寿命试验过程。     

基于80C196单片机的橡胶硫化仪的研制

利用80C196单片机研制了一种低成本、全自动化橡胶硫化仪。该仪器采用单片机驱动24针打印机和彩色波晶屏，实现了整机自动控制，大大提高了整机的性能价格比，在橡胶加工工业中具有较大的实用价值。     

一种高精度频标比对方法

介绍了相位重合点检测技术和频差倍增原理,提出了基于频差倍增技术的计数方案,实现了虚拟频标比对仪的设计,着重分析了系统的运行原理和实现方法。相位重合点检测是一种高精度测量周期性信号参数的技术,该技术有效克服了±1个数的计数误差,使得仪器的测量精度比普通仪器提高了1000倍以上,可广泛应用于高精度频率测量仪器中。实际证明,基于该方案的频标比对系统精度有了显著提高,且设备构成简单、易于实现,取得了不错的效果。     

水润滑橡胶轴承的设计研究

根据原单位的工程经验,综合了很多国内外水润滑橡胶轴承的研究情况,对水润滑橡胶轴承及其润滑机理进行了简单介绍和分析,提出了水润滑橡胶轴承的设计方法,指出了各结构参数对水润滑橡胶轴承磨损以及承载能力等的影响,为水润滑橡胶轴承的工程设计提供指导。     

压电驱动共振式高频疲劳试验机构的设计与实验

针对在小振幅、高频受力工况下微小与硬脆材料构件的疲劳检测,提出利用压电振子(PZT、PLZT或PMN)作为高频疲劳试验机构的驱动力源,并利用系统共振方法设计高频疲劳试验机构.首先,介绍压电共振式疲劳试验机构的工作原理,建立了动力学模型,获得了系统的动态特性.然后,设计和制作了样机.最后,利用样机测量了作用在试件上的动载荷.实验结果表明;改变输入交流电压幅值(100～250 V)和板弹簧厚度(1.1～0.6 mm),可施加在试件上的动载荷为24.7～99.2 N.本文制成的样机适用于测试动载荷在为24.7～99.2 N,且在小振幅、高频受力工况下试件的拉伸和弯曲疲劳性能.     

Loading rate effects of high damping seismic isolation rubber bearing on earthquake responses

This paper investigates the effects of the loading rates of high damping seismic isolation rubber bearing on earthquake responses. For this purpose, a seismically isolated system is formulated by the Runge-Kutta numerical algorithm with nonlinear rate model of high damping rubber bearing to carry out the seismic time history response analysis. Results, of the seismic time history response analyses using both the present parameter equations and Fujita's equations are compared with those of pseudo dynamic tests. From these results it is confirmed that the parameter equations of high damping rubber bearing should be obtained by tests with the loading rate equivalent to the isolation frequency as close as possible.     

高频群脉冲电源在微细孔电化学加工中的应用

针对电化学加工的特殊需要所设计的一种新型电源———高频群脉冲电源的设计原理和特征,从理论上分析其对 于传统的直流电源和脉冲电源在微小型零件加工中的优越性;通过微细孔加工对这种新型的电源进行了分析和说明。 结果表明,在微小型加工领域,采用高频群脉冲电源在改善加工精度,提高加工质量方面优于直流电源和脉冲电源。     

光源闪动频率测试系统设计

针对某型号手机带手电筒闪光的特点,设计了一种光源闪动频率测试系统。利用小面积PIN光电二极管对光源闪动的信息进行捕捉,设计了光电转换电路对光信号进行识别和转换,采用滞回比较器对信号进行整形。通过对手电筒30Hz闪动模式实际测量表明:该系统性能可靠且测量精度高,有一定的实用价值。     

相轨迹电涡流无损检测方法及频率响应特性研究

基于电磁涡流检测的变压器等效理论,研究了激励频率对电涡流等效变压器模型中各参数的影响。对不同频率正弦激励下空间磁通密度法相分量B_z信号进行相敏解调,并绘制其相轨迹图。仿真及实验结果表明,在不同频率的电流激励下,B_z的相轨迹最大值点所处位置相同.在该最大值点处,单一频率激励下B_z的相轨迹均呈现较好的线性度。而当激励频率变化时,相轨迹的斜率k_B呈现出高维度的变化规律,利用多项式拟合方法对k_B=f(ω)进行最小二乘拟合后发现,被测材料表面及内部缺陷均会对k_B=f(ω)的模型产生影响,表面缺陷对高频部分影响更明显,而内部缺陷使低频部分的变化更大。利用这一结论可有效识别缺陷深度,且该方法实现了对提离噪声的抑制。     

液压式可变高频冲击锤

介绍了一种液压式可变高频冲击锤,分析了其结构特点和工作原理,讨论了冲击锤的机构特点以及使用场合.这种设备尤其在海洋和地质勘探领域具有非常好的应用前景.     

Bending of long, rectangular-section bonded rubber blocks

Readily-calculable explicit closed-form representations are determined for the bending stiffness of, and stresses within, generally loaded bonded rubber blocks of long, rectangular cross-section. They satisfy exactly the stated governing equations and conditions based upon the classical theory of elasticity. From these, more detailed investigations are given for the especially interesting loading cases corresponding to simple bending, cantilever loading and apparent shear. It is observed that the deformed profiles of the side surfaces are not in general parabolic as has been usually assumed previously. In simple bending an improved approximate elementary expression is deduced for the couple needed to create a specified rotation of the loaded end of the block. Similarly, in apparent shear a more realistic simple estimate is derived from the exact expression for the ratio of the true to the apparent shear modulus.     

Fretting behavior of a rubber coating: Friction characteristics of rubber debris

This paper presents friction characteristics of a rubber coating undergoing fretting-like, oscillatory motion. Results are presented for rubber coated stainless steel as well as uncoated stainless steel experiencing fretting motion. Friction coefficients are experimentally investigated before and after the rubber coating is fully worn out. The effect of load, velocity and displacement amplitude on the friction coefficients of both uncoated and coated stainless steel is discussed.     

High frequency group pulse electrochemical machining

In the process of machining ultrathin metal structure parts, the signal composition of high frequency group pulse, the influence of frequency to reverse current, and the design of the cathode in high frequency group pulse electrochemical machining (HGPECM) are discussed. The experiments on process were carried out. Results indicate that HGPECM can greatly improve the characteristics of the inter-electrode gap flow field, reduce electrode passivation, and obtain high machining quality. The machining quality is obviously improved by increasing the main pulse frequency. The dimensional accuracy reaches 30–40 μm and the roughness attained is at 0.30–0.35 μm. High frequency group pulse electrochemical machining can be successfully used in machining micro-parts. __________ Translated from Transactions of Beijing Institute of Technology, 2006, 26(7): 585–588 [译自: 北京理工大学学报]     

基于调频激励和细化谱分析的多频涡流检测技术研究

常规多频涡流检测技术在谱分析时,一般采用多个频率的正弦信号同时工作,其激励信号峰值因数较大且检测信号频谱为离散谱.文中提出了一种基于调频信号激励和检测信号细化谱分析的多频涡流检测技术,它不仅降低了激励信号峰值因数,而且检测信号频谱为连续谱.对检测信号施加Tukey窗函数改善谱图,采用Chirp-Z变换计算检测信号频谱,提高谱图的频率分辨率.定义谱图能量、谱图重心、谱图峰度和谱图偏度4个特征量应用于缺陷识别和分类.对于内部缺陷,采用谱图差峰值频率点,定量检测内部缺陷的位置.理论分析和实验结果相一致,验证了所采用方法的正确性.     

一种能量自回馈的交流电机测试系统

为解决“交流电机研发、生产中需要对交流电机的各项性能进行测试”的问题,将电机的变频控制和能量回馈等多项电机控制技术应用到交流电机测试系统中,提出了一种新型交流电机测试系统一能量自回馈的交流电机测试系统。先从理论上分析了该系统的设计原理与合理性,又通过仿真分析和实验测试验证了系统的可行性与稳定性。最后,还提出了能量自回馈测试系统的研究发展方向。研究结果表明,该系统结构简单、控制方便,消除了直接回馈电网带来的一系列弊端。     

金属橡胶成型工艺研究及其应用

主要研究了金属橡胶的成型工艺,介绍了金属橡胶材料在工业中的应用.