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This paper presents a novel piezoelectric-driven nanoindentation system for a scanning electron microscope (SEM) with an improved analog compensation (IAC) method. This system mainly consists of a piezoelectric-driven indenter head, a rectangle-shaped transducer, and a nanopositioner module. Compared with the state-of-the-art piezoelectric-driven nanoindentation system with a circle-shaped transducer, the proposed nanoindentation system is capable of multi-direction operation inside a SEM with a rectangle-shaped transducer. Self-matched semiconductor strain gauges are selected as the position sensor for the piezoelectric-actuator. The Wheatstone bridge output voltage cannot achieve a zero temperature coefficient because the temperature coefficients of self-matched semiconductor strain gauge pairs become significantly different from each other after installation in practice. An IAC method is proposed to compensate the temperature coefficients further. Compared with the existing analog compensation method, the IAC method solves the problem of amplifier saturation and improves the sensitivity of the self-matched semiconductor strain gauge pairs position sensor by 27%. The multi-direction operation results inside a standard SEM HITACHI SU5000 validate the advantage of the developed nanoindentation system. [ABSTRACT FROM AUTHOR]

Crosstalk resistance is an important criterion for evaluating the measurement error of the Joint Torque Sensor (JTS) in actual collaborative robot application, but few research literature studies on the crosstalk resistance of shear beam-type JTS have been found. This paper proposes a mechanical structure of one shear beam sensor and determines its strain gauge working area. Multi-objective optimization equations are established with three major performance indicators of sensitivity, stiffness, and crosstalk resistance. Optimal processing and manufacturing structure parameters are obtained by employing both the response surface method based on the central composite design experimental principle and the multi-objective genetic algorithm. By simulating and experimenting, the optimized sensor is verified and has the following indices: overload resistance 300% F.S., torsional stiffness 503.44 KN m/rad, bending stiffness 142.56 KN m/rad, range 0–±200 N m, sensitivity 25.71 mV/N m, linearity 0.1999%, repeatability error 0.062%, hysteresis error 0.493%, measurement error less than 0.5% F.S. under Fx (392.4 N) or Fz (600 N) crosstalk load, and measurement error less than 1% F.S. under My (25 N m) moment crosstalk. The proposed sensor possesses good crosstalk resistance and especially axial crosstalk resistance and has good overall performance to meet well the engineering requirements. [ABSTRACT FROM AUTHOR]

Digital Image Correlation (DIC) is a camera-based method of measuring full-field displacements and strains from the surface of a deforming object. It can be applied at any length scale (determined by the lenses) and any time scale (determined by the camera), and because it is non-contacting, it can also be used at temperatures much higher than can be withstood by bonded strain gauges. At extreme temperatures, materials emit light in the form of blackbody radiation, which can saturate the camera sensor. It has previously been shown that the emitted light can be effectively screened by using ultraviolet (UV) cameras, lenses, and filters; however, commercially available UV cameras are relatively slow, which limits the speed of combined UV-DIC measurements. In this study, a UV intensifier was paired with a high-speed camera, and its ability to perform UV-DIC at high temperature and high speed was investigated. The system was compared over three different experiments: (A) a quasi-static thermal expansion test at high temperature, (B) a vibration test at room temperature, and (C) the same vibration test repeated at high temperature. The system successfully performed DIC up to at least 1600 °C at frame rates of 5000 fps, which is more than 100 times faster than other examples of UV-DIC in the literature. In all cases, measurements made using the UV intensifier were much noisier than those made without the intensifier, but the intensifier enabled measurements at temperatures well above those which an unfiltered high-speed camera otherwise saturates. [ABSTRACT FROM AUTHOR]

Inertial piezoelectric actuators (IPAs) are widely used in micro–nano manipulation, biomedicine, and other fields as the simple structure and excitation signal. However, the step consistency is difficult to guarantee in a large stroke range due to the limited machining accuracy of the mover and inherent roll back, which limits the practical application in these precision fields. Therefore, a step consistency active control method for IPAs is proposed based on bending hybrid motions, which uses embedded strain gauges as the force sensors to acquire the pressure between the mover and the actuator. The IPA is driven by horizontal bending motion, and the pressure can be dynamically adjusted by vertical bending motion to ensure the constant pressure and achieve a constant step. Experiments results show that the maximum standard deviation of the step is 0.41 µm under the active control of 350 Vp–p and 1 Hz driving voltage within 2 mm stroke range in 500 driving cycles, and the maximum standard deviation of the step is 1.14 µm under the non-active control with the same conditions, which show that the proposed method evidently improves the step consistency of IPA in a large stroke range. [ABSTRACT FROM AUTHOR]

In this paper, a micro-load cell utilized for the thrust measurement of a micro-resistojet is described. To improve the degree of completion of the micro-resistojet during the development process, a concept of a micro-load cell, which enables sufficient performance evaluation under space environmental conditions, was proposed through minimization and simplification of a thrust measurement stand. The piezoresistive sensing method was applied to this load cell, which was composed of a membrane, strain gauges, and a built-in Wheatstone bridge. The membrane size was designed using large-deflection theory so that the load cell could exhibit linear characteristics within the measurement range. A polysilicon strain gauge with a high gauge factor was used for the piezoresistor. The strain gauge also had very low sensitivity to temperature, allowing accurate measurement of the membrane deflection caused by thrust without requiring an additional compensation circuit. Four strain gauges were placed to form a full-bridge circuit at the edge of the membrane. The load cell was then realized by a microelectromechanical system fabrication process. The fabricated load cell was calibrated using a three-axis precision moving stage and a commercial load cell. As a result, the load cell output signal was linear in the measurement range of 1–7 mN and the measured sensitivity of the sensor was 1.566 31 × 10−4 V/mN. The calculated nonlinearity was within 1% in the measurement range. [ABSTRACT FROM AUTHOR]

We introduce a simple thrust stand for the direct measurement of the millinewton impulses or thrusts delivered by small thrusters intended for in-space electric propulsion. The thruster under test, with a weight below 1.5 kg, is disposed on a horizontal platform and its impulse is measured as an overweight by using a strain gauge cell physically protected from the ambient plasma and vacuum conditions. This system provides ten thrust readings per second with noise peak to peak amplitudes of 0.10–0.18 mN. The calibration procedures to verify its dynamic response to time dependent thrusts in the range of 0–15 mN using control weights as well as its minimum thrust sensitivity δTs = 0.3 mN are discussed. Additionally, its simple conception permits a plain data reduction and analysis of steady state and low frequency thrust transients. This thrust stand was employed under low pressure and plasma ambient conditions to measure the steady impulses delivered by the Alternative Low Power Hybrid Ion Engine (ALPHIE) of 0.4–4.0 mN with absolute errors ΔT = ±0.3 mN. Finally, the experimental results show that a control electric voltage governs the ALPHIE thruster throttle. [ABSTRACT FROM AUTHOR]

Electric motors are being investigated in-depth for their application in aerospace. Part of this investigation is the characterization of the loadings from the propulsion devices, in a stationary setup, usually accomplished through the utilization of load cells. The majority of the load cells used in this application are designed around a resistance-based strain gauge. However, electric motors radiate electromagnetic interference (EMI) when in operation, which degrades the signal retrieved through the strain gauge, due to the gauge's metallic construction acting as an antenna for the EMI. To demonstrate the advantage of fiber Bragg gratings (FBGs), with their immunity to EMI, a load cell implementing both sensor technologies was designed and subjected to the same mechanical loading and EMI, with a flywheel coupled to a brushless DC motor. The load cell had a sensitivity of 8.59 ± 0.18 N and 2.49 ± 2.49 N through the strain gauge and FBG system, respectively. The strain gauge signal contained the mechanical loading signal embedded in wideband noise and spikes (that increased linearly with motor angular velocity), while the FBG signal did not, with little noise. The raw strain gauge signal, at a maximum, had a signal power ratio (mechanical signal power divided by the overall signal power mean) of 21.06 at 104.72 rad/s; the FBG signal, at a minimum, had a signal power ratio of 40.09 at 52.36 rad/s. Therefore, on the basis of the mechanical tests performed in this work, the recommended sensor of choice for electric propulsion in aerospace applications is the FBG. [ABSTRACT FROM AUTHOR]

The development of a torsional thrust balance with a spring leaf sensor based on strain gauges is described in the present work. The balance is capable of measuring thrust forces up to 225 mN with micro-Newton resolution. Steady state thrust force is hereby measured via displacement of the balance arm, which in return leads to a displacement of the sensor. The strain induced by the force on the flexure member of the sensor is measured using strain gauges. The development of the sensor and the dynamic behavior of the balance are based on analytical analysis. The oscillatory motion of the balance arm is damped by a passive eddy current damper. An automated calibration mechanism with a pulley and calibration weights is used to calibrate the balance prior to measurement. Atmospheric as well as in situ calibration, single and multiple calibration runs with automatic averaging of calibration coefficients, is possible at all operational stages. The calibration of the balance exhibits excellent linearity and repeatability, while the dynamic behavior shows some deviations from the analytical prediction. The sensor exhibits low noise, with an estimated resolution within 15 μN. A state-of-the-art ratio of resolution to measurement range is achieved. As a conclusion, a series of thrust measurements in the range of 29 μN–37.04 mN are presented and briefly discussed. [ABSTRACT FROM AUTHOR]

This paper discusses the use of optical fiber Bragg grating (FBG) and piezo strain sensors for structural dynamic measurements. For certain industrial applications, there is an interest to use strain sensors rather than in combination with accelerometers for experimental modal analysis. Classical electrical strain gauges can be used hereto, but other types of strain sensors are an interesting alternative with some very specific advantages. This work gives an overview of two types of dynamic strain sensors, applied to two industrial applications (a helicopter main rotor blade and an F-16 aircraft), FBG sensors and dynamic piezo strain sensors, discussing their use and benefits. Moreover, the concept of strain modal analysis is introduced and it is shown how it can be beneficial to apply strain measurements to experimental modal analysis. Finally, experimental results for the two applications are shown, with an experimental modal analysis carried out on the helicopter main rotor blade using FBG sensors and a similar experiment is done with the aircraft but using piezo strain sensors instead. [ABSTRACT FROM AUTHOR]

Force tests were conducted at the long-duration-test shock tunnel JF12, which has been designed and built in the Institute of Mechanics, Chinese Academy of Sciences. The performance tests demonstrated that this facility is capable of reproducing a flow of dry air at Mach numbers from 5 to 9 at more than 100 ms test duration. Therefore, the traditional internal strain-gauge balance was considered for the force tests use in this large impulse facility. However, when the force tests are conducted in a shock tunnel, the inertial forces lead to low-frequency vibrations of the test model and its motion cannot be addressed through digital filtering because a sufficient number of cycles cannot be found during a shock tunnel run. The post-processing of the balance signal thus becomes extremely difficult when an averaging method is employed. Therefore, the force measurement encounters many problems in an impulse facility, particularly for large and heavy models. The objective of the present study is to develop pulse-type sting balance by using a strain-gauge sensor that can be applied in the force measurement of 100 ms test time, especially for the force test of the large-scale model. Different structures of the S-series (i.e., sting shaped balances) strain-gauge balance are proposed and designed, and the measuring elements are further optimized to overcome the difficulties encountered during the measurement of aerodynamic force in a shock tunnel. In addition, the force tests were conducted using two large-scale test models in JF12 and the S-series strain-gauge balances show good performance in the force measurements during the 100 ms test time. [ABSTRACT FROM AUTHOR]

Investigates the use of gallium arsenide (GaAs) as an optical strain gauge. Use of optical fibers; Development of compressive and tensile strains; Effects of sample width; Calculation of the strain sensitivity of the device.

Analyzes the dynamic behavior of a strain gage pressure transducer with the one-dimensional elastic wave theory. Mathematical model; Comparison of analytic with experimental results; Means for ensuring a required measuring precision; Sticking condition of the strain gauge.

Commercial carbon composition resistors have been used as gauges to make dynamic stress measurements in homogeneous and heterogeneous reactive and inert materials. Initial loading was provided by plane wave lenses or shaped charge jets. A series of gas gun and aquarium experiments has been conducted to characterize the behavior of the gauges. Calibrations up to about 14 GPa for nominal 470 Ω resistors and 17 GPa for nominal 4700 Ω resistors are presented. The accuracy of the carbon resistor gauges is limited by response time considerations when submicrosecond rise times are encountered, and there is hysteresis during release. The gauge-to-gauge reproducibility appears to be adequate, and they survive in situations where no other stress transducer has been successfully used, such as in reacting beds of large-particle gun propellants. [ABSTRACT FROM AUTHOR]

Thick-film strain gauges having strain characteristics with small temperature dependency have been developed. Their gauge factor is more than ten times higher than that of a thin-film strain gauge and nearly half the value of a semiconductor gauge. This strain gauge is a thick film composed of 15 wt. % WO[sub 3] · 15 wt. % RuO[sub 2] · 70 wt. % glass (weight percent ratio). Its gauge factor is 40 to 55, its temperature coefficient of resistance is 0 to -200 ppm/°C, and its temperature coefficient of gauge factor is about -400 ppm/°C. The change of gauge factor in a repeat test after a strain had been applied to the gauge was smaller than 1%. The gauge was also very stable. [ABSTRACT FROM AUTHOR]

A simple technique is demonstrated for measuring strains in an electromagnetically noisy environment using electrical strain gauges. For applications in which strains are produced electromagnetically in current-carrying structures, the noise signal can be much larger than the strain signal. Furthermore, the noise signal is at precisely the same frequency as the strain signal, making standard methods of synchronous signal detection difficult. This problem has been surmounted by modulating the detection circuit sensitivity. Bridge circuit modulation has been shown to effectively decouple the strain signal from the noise, even at very low strain levels of ∼10-8 m/m. [ABSTRACT FROM AUTHOR]

Possibilities of the application of resistance foil strain gauges in high pressure research are discussed. In order to demonstrate such a possibility, the isothermal linear compressibility of selected metals, such as Al, Cu, and Fe, was measured with the use of foil strain gauges. The results obtained were compared with those given in the literature. Also, the possible effect of a protective foil on foil gauge properties subjected to high pressures was investigated. The experiments have shown that foil strain gauges are suitable for compressibility measurements and attain similar accuracy as wire strain gauges. The measuring method presented here was used to determine the compressibility of superionic glass given by the formula 0.4Agl-0.6(Ag[sub 2]O-P[sub 2]O[sub 5]). It is concluded that the improved properties of foil strain gauges, in comparison with the wire ones, will result in better application possibilities of foil strain gauges in high pressure research. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

This article presents a unique hybrid flowmeter that combines the turndown ratio/low resistance benefits of a variable area differential pressure flowmeter with the low component simplicity of a target flowmeter. The design attaches a single element strain gage to the flexural membrane suspended in a fluid flow passage, eliminating the need for force or pressure transducers. A prototype of the concept produced favorable results that conformed well to a theoretical model. [ABSTRACT FROM AUTHOR]

An experimental technique is described which employs resistive strain gauges to measure the pressure–volume relationship of solids up to∼50 kbar. The strain resolution is better than 10 ppm with a dynamical range up to 20 000. Two examples are presented to illustrate the sensitivity and the reliability of this technique. [ABSTRACT FROM AUTHOR]

In a closed water-tunnel circuit, the multi-component strain gauge force and moment sensor (also known as balance) are generally used to measure hydrodynamic forces and moments acting on scaled models. These balances are periodically calibrated by static loading. Their performance and accuracy depend significantly on the rig and the method of calibration. In this research, a new calibration rig was designed and constructed to calibrate multi-component internal strain gauge balances. The calibration rig has six degrees of freedom and six different component-loading structures that can be applied separately and synchronously. The system was designed based on the applicability of formal experimental design techniques, using gravity for balance loading and balance positioning and alignment relative to gravity. To evaluate the calibration rig, a six-component internal balance developed by Iran University of Science and Technology was calibrated using response surface methodology. According to the results, calibration rig met all design criteria. This rig provides the means by which various methods of formal experimental design techniques can be implemented. The simplicity of the rig saves time and money in the design of experiments and in balance calibration while simultaneously increasing the accuracy of these activities. [ABSTRACT FROM AUTHOR]

Describes the design and fabrication of a simple strain cell using a displacement dial gauge. Strain sensitivity; Calculation of average strain in the film; Applications of high sensitivity strain gauges.

A simple profilometer based upon a commercial strain gauge force transducer is described. It has been used on polymer film coated substrates to determine film thicknesses on the order of 10.0 u µm. Measured film thicknesses agree with gravimetrically determined values to within ±0.3 µm. [ABSTRACT FROM AUTHOR]

A free deforming-cylinder pressure transducer with bonded strain gauges is presented for pressure measurements in liquid media up to 0.5 GPa. Description is given of its operating principle and of its main metrological properties; the overall accuracy of this prototype pressure transducer is inside ±0.25 MPa. [ABSTRACT FROM AUTHOR]

A variable-temperature probe has been developed to study the effect of strain on the transport properties of superconducting wires and tapes in high magnetic fields. The strain is applied to the wire by soldering it to a thick coiled spring and twisting one end of the spring with respect to the other. Strain can be applied reversibly from -0.7% to +0.7%. Measurements can be performed either in (pumped) cryogen or under vacuum. When immersed in liquid helium at 4.2 K, the probe can carry at least 200 A. From 6 to 16 K, with thin (low-loss) current leads the temperature of the sample is stable to ±45 mK for currents around 15 A, and to ±100 mK for currents around 25 A. With thick current leads, ±10 mK stability is achieved for currents up to 85 A. Full details of the probe design are described. Results obtained for a bronze processed niobium-tin multifilamentary wire are presented. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Strain, deformation, and temperature measurements constitute some of the most interesting parameters to be monitored in composite materials or structures. White light interferometry offers good performance even for long-term measurements of these parameters. Based on the Michelson interferometer, a fiberoptic localized extensometer and multiplexing strain-sensing techniques are demonstrated in this article. Related problems such as the effect of optical fiber coating on an embedded sensor and the dual use of one sensor are discussed. Finally, application examples of surface strain and internal strain (0-6000 microstrain) and temperature (22-36 °C) of concrete sample are given. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]