应变电测与传感器技术的新发展及应用

首先介绍应变电测与传感器技术的新发展:(1)各种新型特殊电阻应变计:高温600～800℃密封焊接式应变计,900℃粘贴式动态应变计,低温-269～-196℃电阻应变计,防水应变计,大应变15%～30%电阻应变计等。(2)新型应变计式传感器:土木、机械用力传感器,钢筋计,土压力计,扭矩传感器,六分力传感器,另有应变传感器可安装在结构上测量应变,可重复使用,配合应变测试仪器使用,还可进行无线遥测。(3)新型数据采集仪器:高速静态数据采集仪,最多达1000通道,可测应变、温度、应变式传感器、直流电压等,精度0.05%,采集速度每通道0.04s,多通道总计0.4s采集完成;小型多通道动态应变和温度记录仪,最多有80通道,其中应变最多达64通道,其余为热电偶、电压测量通道;超动态电阻应变仪,频响可达200～500kHz,另有数据采集和分析软件可快速分析处理数据。其次介绍近来在土木工程、铁路工程、机械工程和航空航天工程以及医学、体育等领域中的若干应用实例。     

Early days of the resistance strain gauge

The earliest developments in the use of electrical strain gauges as a means of quantifying the measurement of stress in materials are recalled by the author, whose own involvement was associated with the early developments in the mechanised production of strain gauges. The manufacture of batch quantitities is vividly recounted following the realisation that strain gauges would lend themselves to commercial exploitation.     

A computer program for repetitive strain gauge rosette analysis

A system is described with which the signals from a strain gauge rosette can be used to compute principal stresses and their orientation, the results being plotted on a VDU screen and updated continuously.     

高温ITO薄膜应变计制备及压阻性能EI北大核心CSCD

高温薄膜应变计被广泛应用于极端条件热端构件的应变测量。ITO薄膜应变计通常能够应用于1000℃以上的应变测量,为了研究ITO薄膜的显微结构、XPS光谱、阻温特性及压阻响应,采用磁控溅射在陶瓷基底上制备了ITO薄膜应变计,并在高温纯N2中热处理ITO薄膜。结果表明,其电阻温度系数稳定在-750×10-6℃-1,在1200℃下测试其应变特性,测得电阻漂移率为0.0018 h-1,应变因子为16。ITO薄膜在高温下具有稳定的电阻温度系数和低漂移率,为高温端部件应变的测量提供了可能。     

Vapour pressure thermometry in high magnetic fields using a Pirani gauge

Vapour pressure thermometry has the advantage of not being affected by magnetic fields. Therefore, a study was carried out of thermometry below 1 K using a Pirani pressure gauge in the vapour of He³. Its sensitivity and error in temperature measurements above 0.55 K are dV/dT ≥ K^?1 and 0.4% respectively.Additionally, a semiconductor pressure sensor in the vapour of He⁴ was examined for the vapour pressure thermometry.     

An assessment of a frictional strain gauge probe for dynamic strain measurement

A probe for the measurement of surface strains on dynamically loaded structures has recently been tested at the National Engineering Laboratory (NEL). The procedure for estimating the amplitude of the conditioned signals from the frictional strain gauge attached to the probe is described and the usefulness of the technique is discussed. Calibration data are presented from comparative tests of the performance of the frictional gauge and bonded gauges on an axially loaded testpiece subjected to sinusoidal and random loading conditions.     

A simple technique for installing strain gauges on cylindrical surfaces

In this paper a simple technique for the installation of strain gauges on circular and conical cylindrical surfaces has been described. This technique may be adopted in an experimental stress analysis laboratory where sophisticated equipment is not available.     

Random errors caused by temperature in magnitude of principal strains evaluated ith 3-element strain gauge rosettes

The effects of the uncertainties associated ith the apparent strain and gauge factor data, given by the manufacturer, in the evaluation of principal strains are examined. Principal strains are obtained by a reduction of the strains measured ith electrical resistance strain gauge rectangular or delta rosettes. The theoretical analysis points out the relevance of the effects caused.     

Error analysis and method of accuracy evaluation of strain gauge factor testing apparatus based on pure bending moment beams

For the appraisal of accuracy of strain gauge factor testing apparatus based on pure bending moment beams, the common means adopted since the 1960s and still in use internationally today are by application of the strain definition to measure directly the strain on the calibration beam surfaces. However, because of the imperfect measuring principle and inadequate resolution and accuracy of instruments available, etc., this problem has not been solved satisfactorily. This paper proposes a unique way by introducing two new concepts, i.e. the shape errors of the cylindrical surfaces and deflection errors of the bent calibration beam, in accordance with the features of the forces acting on the beam, and the geometric shape and dimensions of the beam in operation, to analyse and classify the various accidental and systematic errors involved. Through the two concepts, the task of appraisal of accuracy is simplified as the appraisal of the cylindricality of the cylindrical surfaces of the bent calibration beam and the appraisal of the three main parameters in the strain formula.     

Self-compensated high plastic resistance strain gauges for use up to 300°C

The development of a high plastic strain gauge for use up to 300C is presented. This kind of gauge can measure strain up to 8% and possesses good self compensation on carbon steel. Basic analysis, gauge wire, adhesive material, gauge structure and examples of application are also described.     

Closely packed nanoparticle monolayer as a strain gauge fabricated by convective assembly at a confined angle

The reliability and sensitivity of a strain gauge made from a nanoparticle monolayer intrinsically depend on electron tunneling between the adjacent nanoparticles, so that creating nanoscale interstitials with uniform distribution and tuning the interparticle separation reversibly during cyclic mechanical stress are two vital issues for performance enhancement. In this work, one assembly technique is initialized to fabricate parallel nanoparticle strips by precisely tailoring the contact angle of a gold colloid on a substrate. The assembly of a nanoparticle monolayer with a close-packed pattern can be simultaneously switched on and off by independently varying the contact angle across a threshold value of 4.2~. This nanoparticle strip shows a reversible and reliable electrical response even if a mechanical strain as small as 0.027% is periodically supplied, implying well-controlled electron tunneling between the adjacent nanoparticles.     

The fatigue of strain gauges - a user's view

The information needed by the strain measurement engineering concerning the fatigue of strain gauge installations is discussed, and compared with that readily available. It is suggested that far more extensive and detailed information is needed and should be made readily available.     

Use of displacement data to calculate strain gauge response in non-uniform strain fields

A simple and effective method is described for calculating the strain indicated by a practical strain gauge mounted in a nonuniform strain field. The method uses integration or summation of the displacement field along the perimeter of the strain gauge area. This procedure gives results which are equivalent to those obtained by much lengthier calculations involving double integration of the strain field within the strain gauge area. The displacement summation method can easily take into account significant strain gauge design details such as number, length, width and spacing of the grid lines. The method also demonstrates that a strain gauge can be used as a displacement sensor as well as a strain sensor.     

The design of a multi-purpose multi-component strain gauge dynamometer

The design, construction and calibration of a multi-purpose multi-component strain gauge dynamometer is described. The dynamometer was constructed for use with a free surface water channel, which can also be used as a water tunnel or a cavitation tunnel. In this experimental facility, the large speed range available (0·03 to 6·1 m/s) and the variety of projects encountered require the measurement of a wide range of loads in several different configurations. The dynamometer system has been based on a unit block concept so that the blocks can be assembled into a suitable configuration and complexity of components to suit each particular problem.
The basic design concept is described together with the calibration results and the magnitude of the interactions. It is concluded that the overall accuracy of the dynamometer blocks and the absence of interaction coupled with the versatility of the system confirm the choice of the original design.     

The role of strain measurement technology in structural evaluation

This paper describes the importance of structural evaluation to the process of design assessment and outlines the significant role played by strain measurement technology in extending the scope of strain history data collection and facilitating strain monitoring of full-scale structures in the laboratory. After some general discussion of the various models of structural behaviour, it then proceeds to give a brief historical account and outlines the principles of thermoelastic stress analysis (TSA). A general desciption is provided of a specific TSA technique namely Stress Pattern Analysis by Thermal Emission (SPATE).
Despite the level of innovation and development in strain measurement technology, the use of bonded strain gauge elements is still by far the most commonly used strain measurement and monitoring technique in structural evaluation work at NEL. The paper highlights several recent test programmes carried out at NEL in the form of case studies which demonstrate different aspects of measuring, monitoring and validation of this and other strain measurement techniques; and verification of analytical models.     

Apparent strains in unmounted strain gauges at high temperature

A detailed investigation into the source of the unmounted apparent strains in resistance strain gauges over a temperature range of 20°C to 550°C is presented. Different measuring systems give different values of unmounted apparent strain. Formulae for two different measuring systems relating the unmounted apparent strains to resistance values are derived. Values computed from these formulae using measured values of resistance are compared with values of unmounted apparent strains measured directly. In addition, formulae which are essential in order to relate the actual strain to the indicated strain are derived for each of the systems. It is shown using the derived expressions that the magnitude of the unmounted apparent strains can be reduced considerably by connecting a shunt resistor across the active element.     

Dynamic pressure measurements during pulsed gas injection in a quadrupole ion trap

A quadrupole ion trap has been modified to perform dynamic pressure measurements during pulsed introduction of gases. A continuous electron beam is directed through the ion trap where the gas is ionized via electron impact. Ion and electron currents are monitored on the ring and end-cap electrodes, respectively. Dynamic pressure measurements in a region not accessible to a standard gauge are performed using a static quadrupole field. Characteristic current-voltage curves of the ion-trap gauge are presented and optimum operating conditions of the electron-ion optical system are identified in steady state conditions. The sensitivity of the ion-trap gauge is calibrated at these optimum conditions. In the pulsed gas mode ion and electron signals are measured simultaneously on a fast oscilloscope. The time constant of the circuit for the dynamic measurements is ∼129 μs and pressure variations of ∼10⁻⁴-1 Pa occur within 60-130 ms. The exponential decay of the ion signals is used to calculate pumping speeds for helium and argon gases. The distinctive advantages of pulsed gas injections over the use of static pressures in quadrupole ion-trap mass spectrometry are emphasized.     

A Pirani gauge in a high-intensity proton accelerator

We have developed a Pirani-type vacuum gauge for monitoring the back pressure of a turbo-molecular pump (TMP), which is employed as the main pump for the 3-GeV Rapid Cycling Synchrotron (RCS) at the Japan Proton Accelerator Complex (J-PARC).As vacuum components are subjected to high levels of radiation in these devices, the TMP and the vacuum gauge used for monitoring the TMP’s back pressure should have high reliability and a long life so as to minimize exposure to radiation during maintenance. Moreover, to ascertain the vacuum conditions of the ring and to monitor the back pressure, the gauge should preferably be capable of measuring pressures from 0.1 Pa to 10³ Pa. To satisfy these requirements, the following measures were taken: All the components around the sensor head, including the connector and cables, were replaced with components that were guaranteed to perform satisfactorily even with a radiation dose greater than 30 MGy. Then, the semiconductor devices used in the measuring circuits were checked by using the four-point probe method and found to work satisfactorily at a distance of 150 m from the sensor. To measure higher pressures, the current control circuit was modified in such a way that the set value of the current increased in stages as the pressure increased. Further, it was ensured that the gauge showed high resistance to vibration and to an abrupt air intake as well as high radioactive resistance. The newly designed gauge head comprised a series of twelve Pt wires, each with a diameter of 100 μm. It was confirmed that pressures from 5 × 10⁻² Pa to atmospheric pressure were measurable with an accuracy of less than 30%.This Pt Pirani gauge has shown good performance in monitoring the back pressure of the TMP at the J-PARC RCS, where it has been in use since Oct. 2009.     

无模型控制在气动变载荷加载系统中的应用

针对气动加载系统压力跟踪控制中强非线性、强耦合性、模型不精确性等问题,提出一种无模型自适应控制(model-free adaptive controller,MFAC)器,该控制器结构简单、参数少、不需要被控系统的数学模型,是一种低成本的控制器.其中的伪偏导数估计算法仅需利用受控系统的输入输出数据来估计伪偏导数,使该算...     

Experimental evaluation of a method for separating axial and bending stresses from strain gauge measurements taken on one surface by three-element rosettes

A method is described and results presented for the separation of axial and bending components of stress taken on one surface of a structure with a two-tier, three-element rosette assembly.