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1.
对用电子显微镜测量薄膜厚度的三种方法:双束衍射法、污斑法、污线法进行了实验及比较分析。结果表明:污法操作简单、使用方便、定位准确、测量误差小,是一种较为理想的测厚方法。  相似文献   

2.
对用电子显微镜测量薄膜厚度的三种方法:双束衍射法、污斑法、污线法进行了实验及比较分析。结果表明:污线法操作简单、使用方便、定位准确、测量误差小,是一种较为理想的测厚方法。  相似文献   

3.
文章分析了腐蚀测厚变送器测量误差产生的原因,并给出了一种不同温度下误差校正补偿算法,实现从-40~500℃对测厚数据进行温度补偿。为实现高温易腐蚀设备和管线的在线测厚,给出了超声波在线实时测厚技术和实现此技术的硬件、软件方案。根据此方案设计的腐蚀测厚变送器,厚度检测精度高,运行稳定,在腐蚀测厚领域具有极高的应用价值。  相似文献   

4.
华焕灵 《计量技术》2000,(12):18-19
射线测厚公式中吸收系数在较大测量范围内并非为一常数,本文提出一种测厚数据的处理方法,并给出在单片机上的实现实例。  相似文献   

5.
在科研生产中,对介质厚度测量提出了越来越高的要求,例如在橡胶轮胎的生产过程中,要求控制胶帘布厚度公差为±0.03mm。传统方法是采用同位素测厚法,但不易掌握。电容法是继同位素法后提出的一种新的测厚方法。它具有安全、准确、经济、易于掌握的特  相似文献   

6.
袁易全  朱明 《计量学报》1998,19(3):175-182
介绍一种新颖高温超声测厚实验系统的理论研究和实测结果。阐述了它的原理、特点、5MHz超声换能器系统及多种介质测厚使用效果。本测厚系统可在温度328℃介面上接触在线运行检测。当PZT晶片夹角设置为2°、声波延迟块长20mm时,则在0.2~13mm测厚范围内有效,精度可达0.1mm。该机体积小、功耗低,且可适用于多种介质的测厚工作。  相似文献   

7.
 为了满足无缝钢管在线高精度测厚的需求,开展了基于广义倒频谱测厚技术的研究.分析了传统测厚算法的缺点,提出一种基于广义倒频谱的无缝钢管在线测厚方法,此算法结合了相关分析和倒频谱的综合优势,处理后的波形峰值尖锐,提高了测厚精度;在此基础上对在线系统钢管旋转造成的声程误差进行了补偿.实验结果证明该方法测量精度高,实时性强,适用于工业无缝钢管在线高精度检测系统.  相似文献   

8.
卷绕式镀膜机的电气控制   总被引:2,自引:1,他引:1  
李宪华 《真空》1992,(6):44-49
卷绕式镀膜机的电气控制包括真空机组、蒸发、送铝丝及薄膜传动等四部分, 此外还增设了方阻法测厚装置。本文对上述的电气控制作了粗浅的介绍与分析.其重点 是电气控制的可靠性并力求电路简单,使用方便.可为用户维修该设备提供理论指导.  相似文献   

9.
针对石化行业中在高温工作状态下的管道测厚问题,本文研究了超声波高温管道测厚方法中的一些影响因素,并实现了一套高温管道超声波测厚的仿真系统。实验中讨论了不同厚度、不同材料、不同噪声水平以及不同温度对超声波管道测厚结果的影响。此外,比较了不同测厚方法对管道厚度测量的影响。实验结果表明,该系统能够较好的模拟高温超声波测厚系统,能够实现高温管道厚度的测量。  相似文献   

10.
本文论述了使用单片机测频的四种方法,即直接计数法、周期测频法、混合测频法和等精度测频法。通过误差分析指出,直接计数法适于高频测量,周期测频法适于低频测量。在此基础上,提出具有通频带测频性质的混合测频法,并给出其测频最大相对误差和最大误差频率点的表达式。关于等精度测频法,提出利用软件查询实现同步的方法。并论证其测频精度可达10~(-6)  相似文献   

11.
This paper deals with the propagation of surface waves in homogeneous, elastic solid media whose free surfaces or interfaces of separation are capable of supporting their own stress fields. The general theory for the propagation of surface waves in a medium which supports surface stresses is first deduced, and then this theory is employed to investigate the particular cases of surface waves, viz. (a) Rayleigh waves, (b) Love waves and (c) Stoneley waves. It is seen that the Rayleigh waves become dispersive in nature; and, in case of low frequency with residual surface tension, a critical wavelength exists, below which the propagation of Rayleigh waves is not possible. This critical wave length is directly proportional to the surface tension. Some numerical calculations have been made in the case of Love waves and conclusions have been drawn.  相似文献   

12.
Effects of inhomogeneity on surface waves in anisotropic media   总被引:1,自引:0,他引:1  
This paper investigates the effects of anisotropy and inhomogeneity on surface waves in elastic media. Exponential variation in properties are assumed for the elastic parameters and material density. The classical equations of motion for propagation of waves in an inhomogeneous transversely isotropic elastic solid are deduced. The equations of motion for surface waves are derived and general surface waves are investigated. This general theory is then utilized to investigate Rayleigh, Love and Stoneley waves. Results obtained in the above cases reduce to the corresponding well-known classical results when inhomogeneity and anisotropy are not present. It is seen that inhomogeneity has significant effects on dispersion characteristics. Numerical calculations are included for Love waves and some conclusions have been drawn from the above calculations.  相似文献   

13.
P R Sengupta  Sisir Nath 《Sadhana》2001,26(4):363-370
The aim of this paper is to investigate surface waves in anisotropic fibre-reinforced solid elastic media. First, the theory of general surface waves has been derived and applied to study the particular cases of surface waves — Rayleigh, Love and Stoneley types. The wave velocity equations are found to be in agreement with the corresponding classical result when the anisotropic elastic parameters tends to zero. It is important to note that the Rayleigh type of wave velocity in the fibre-reinforced elastic medium increases to a considerable amount in comparison with the Rayleigh wave velocity in isotropic materials.  相似文献   

14.
The propagation of plane waves in fibre-reinforced media is discussed. The expressions of phase velocities of quasi-P (qP) and quasi-SV (qSV) waves propagating in plane symmetry are obtained in terms of propagation vectors. We have established a relation from which the displacement vector can be obtained in terms of the propagation vector. Expressions for the reflection coefficients of qP and qSV waves are obtained. Numerical results of reflection coefficients are obtained and presented graphically. The partition of energy between qP and qSV waves reflected on free and rigid boundaries due to incident qP and qSV waves are also obtained and presented graphically.  相似文献   

15.
The present paper deals with the study of Rayleigh waves in a thermoelastic homogeneous isotropic solid half space in the context of dual-phase-lag model. The medium is subjected to stress free, thermally insulated, boundary conditions. The equation for the phase velocity of Rayleigh waves and the analytical expressions for the amplitudes of the displacements, temperature and thermal stresses have been derived. The expressions are obtained for a wave traveling along the free surface. The results discussed numerically and illustrated graphically to show effect of the coupling parameter and phase-lags.  相似文献   

16.
Marine hydrodynamics is characterised by both weak nonlinearities, as seen for example in drift forces, and strong nonlinearities, as seen for example in wave breaking. In many cases their relative importance is still a controversial matter. The phenomenon of particle escape, seen in linear theory, appears to offer a guide to when strongly nonlinear effects will start to become important, and what will happen when they do. In the case of the “ringing” of vertical cylinders in steep waves, particle escape is shown to correspond approximately to local wave breaking, which leads to the cavitation responsible for “ringing”. Another example is rogue waves, where recent results from weakly nonlinear theory are disappointing, and also fail to explain the rogue waves seen in relatively shallow water, as in the data from the Draupner and Gorm platforms. Recent laboratory experiments, too, show wave crests continuing to grow in height after all frequency components have come into phase, which is inconsistent with weakly nonlinear theory. Particle escape, which is more frequent in shallow water, offers a simple alternative explanation for these observations, as well as for the violent motion at the wave crests, which often confuses rogue-wave data. Extreme wave crests have long been known to be strongly nonlinear, so it appears possible that rogue waves are primarily a strongly nonlinear phenomenon. Fully nonlinear computations of two interacting regular waves are presented, to explore further the connection between particle escape and wave breaking. They are combined with Monte-Carlo simulations of particle escape in hurricane conditions, and the very few measurements of large breaking waves during hurricanes. It is concluded that large breaking waves will have occurred about once per hour, and once per 100 h, respectively, in the recent hurricanes LILI and IVAN. These findings call into question the use of non-breaking wave models in the design codes for fixed steel offshore structures.  相似文献   

17.
Large-amplitude waves at the interface between two laminar immisible inviscid streams of different densities and velocites, bounded together in a straight infinite channel are studied, when surface tension and gravity are both present. A long-wave approximation is used to develop a theory for fully nonlinear interfacial waves allowing amplitudes as large as the channel thickness. The result is a set of evolution equations for the interfacial shape and the velocity jump across it. Traveling waves of permanent form are studied and it is shown that solitary waves are possible for a range of physical parameters. All solitary waves can be expressed implicitly in terms of incomplete elliptic integrals of the third kind. When the upper layer has zero density, two explicit solitary-wave solutions have been found whose amplitudes are equal to h/4 or h/9, where 2h is the channel thickness. In the absence of gravity solitary waves are not possible but periodic ones are. Numerically constructed solitary waves are given for representative physical parameters.  相似文献   

18.
The object of the present paper is to investigate the propagation of quasi-transverse waves in a nonlinear perfectly conducting nonhomogeneous elastic medium in the presence of a uniform magnetic field transverse to the direction of wave propagation. Different types of figures have been drawn to exhibit the distortion of waves due to the presence of magnetic field and the nonhomogeneous nature of the medium. Formation of shocks has also been numerically discussed.  相似文献   

19.
In the present context, we consider the propagation of shear waves in the transverse isotropic fluid saturated porous plate. The frequency spectrum for SH-modes in the plate has been studied. It is observed that the frequency of the propagation is damped due to the two-phase character of the porous medium. The dimensionless phase velocities of the shear waves have also been calculated and presented graphically. It is interesting to note that the frequency and phase velocity of shear waves in porous media differ significantly in comparison to that in isotropic elastic media.  相似文献   

20.
The present paper concentrates on the study of propagation and reflection characteristics of waves from the stress free, thermally insulated/isothermal boundary of a piezothermoelastic half space. The non-classical (generalized) theories of linear piezo-thermoelasticity have been employed to investigate the problem. In the two-dimensional model of the transversely isotropic piezothermoelastic medium, there are three types of plane waves quasi-longitudinal (QL), quasi-transverse (QT) and thermal wave (T-mode), whose velocities depend on the angle of incidence and frequency. These waves are dispersive in character and are also affected by piezoelectric as well as pyroelectric properties of the materials. The low and high frequency approximations for the speeds of propagation and the attenuation coefficients of these waves have been obtained. The quasi-longitudinal (QL), quasi-transverse (QT) and thermal wave (T-mode) incident cases at the stress free, thermally insulated or isothermal open circuit boundary of a transversely isotropic piezothermoelastic half space are considered to discuss the reflection characteristics of various waves. The amplitude ratios of reflected waves to that of incident one in each case have been obtained. The special cases of normal and grazing incidence are also derived and discussed. Finally, the numerical computations of reflection coefficients are carried out for cadmium Selenide (CdSe) material by using Gauss elimination procedure. In addition the phase velocities and attenuation coefficients are also computed along various directions of wave propagation. The obtained results in each case are presented graphically.  相似文献   

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