Strain Gauge Bridge Research Articles

Cutting Force Measurement of a Rotating Tool by Means of Optical Data Transmission

The study proposes a new way to accurately measure transient cutting forces of a rotating tool such as a milling cutter from the side of tool. The transmission of cutting forces through a slip ring or a FM telemeter is liable to be affected by noises. Therefore, a device to obtain reliable cutting data has been required to analyze the cutting phenomena, In the measurement system developed, amplified output signals from strain gauge bridges are digitized using an AD converter and then converted to continuous serial data streams to optically transmit them outside a machine tool by use of LED. Received serial data streams by a photo sensor are conversely restored to parallel data, which are immediately processed by a personal computer. The transient cutting forces can be measured without any trouble. As a result, this method was found to be very practical and also applicable to a variety of measuring fields requisite for non-contacting data transmission.

Development of a simple instrument for determination of salt concentration profile in the operation of solar ponds

The development and construction details of an instrument to measure densities of the brine at different depths in a solar pond are presented and discussed. Using a vertically moving sampling tube, brine is drawn from the pond and then is fed to the bottom of a conical container in which a sealed conical glass vessel is fully submerged. The bouyancy force exerted by the water on the sealed glass vessel is measured by a system of cantilever beam and strain gauges. The output of the strain gauge bridge is proportional to the density of the fluid passing through the conical container. It is shown that this instrument can be effectively used to determine the salt concentration profile in salt gradient solar ponds.

New high impedance strain gauge bridge transducer plus a new low current amplified pressure transducer

New high impedance strain gauge bridge transducer plus a new low current amplified pressure transducer

Certain problems of metrological support of tensometric data acquisition systems

Multichannel tens.metric data aquisition systems (DASs) offer high metrological characteristics and fast response in the measurement of various physical quantities such as force, pressure, strain, etc. Since they are commonly used under conditions far from normal, one must record besides the measured data also the various influencing factors (temperature, pressure, humidity)that may affect the results. Such an approach makes it possible to find corrections to the measured results in order to ensure that the accuracy obtained in the given operating conditions is as near as possible to that obtainable under normal conditions. This approach improves the performance of DASs but at the same time puts more stringent demands on the reliability of incoming information and, consequently, also on the metrological reliability of the system which can be described by the level of potential breakdowns~ To reduce the measuring cycle, DASs are usually complemented by a computer which stores the relevant data, processes the incoming information and controls the measuring process. Tens.metric DASs are usually fixed facilities acting as an organic part of the experimental setup so that centralized certification and verification in special State or departmental metrological service laboratories is precluded. This creates the problem of developing a system of metrological support for use in DAS certification and for providing information about the DAS performance in the course of its operation. Metrological support systems are based on special-purpose portable and fixed reference measuring facilities of an appropriate level of accuracy and auxiliary devices combined with the DAS into a common metrological data control and processing system, thusproviding a selftesting system which is always ready for operation. General-purpose reference devices are not suitable for such systems since they do not meet the principal demands of DASs as to accuracy and response speed. The earliest tens.metric measuring facilities, for example, used automatic multichannel recorders with various modifications in which electric signals for strain gauge bridges were applied to ~n electronic amplifier and then to a motor rotating a numbered wheel [i]. Automatic recorders ~ere certified and tested with the aid of a set of resistance coils and boxes. Such operations took up to 140 min of time per channel. To reduce the certification time special reference devices, called strain-gauge calibrators [2], were developed. The principal reduced (with respect to the maximum measuring range) error of strain-gauge calibrators was 0.02-0.03% with a confidence coefficient P = 0495. Their use is suitable for testing tens.metric facilities with a reduced error 6 ~ 0.1% [3]. By using manually controlled strain-gauge calibrators testing time was reduced to i0 min per DAS channel while the application of calibrators with automatic control [4] and computer data processing shortened the testing time to 0.6 min (for nch > 200).

Iii-Flight Measurements of the Vibration History of Spin-StabilizedProjectiles

M spin-stabilized projectiles commonly contain solid but nonrigid or liquid pay loads. These types of pay loads often produce projectile/pay load interactions that are undesirable. Vibrations of the projectile/pay load assembly could impair the performance of military fuzing, especially if that fuzing is mechanical in nature. In some instances, the timer is mechanical, but normally all fuzes have mechanical arming and safety devices. Projectile designers during test sequences often report fuze malfunctions, but little is known about the vibration environment of an artillery projectile during flight. In response to this need, an instrumentation package consisting of a strain gage bridge/attitude sensor and a telemetry unit was built and successfully tested. Several types of units were flight tested and data showing undesirable vibration histories during the flight of a projectile have been recorded.' Data from 155mm projectiles with liquid payloads are discussed. A standard yawsonde body was modified to accommodate a Wheatstone bridge. The bridge was located on a flat machined onto the cylindrical portion of the yawsonde body which extends into the ogive of a parojectile (Fig. 1). This flat was located 90 deg from the optical sensors of the yawsonde. Wires that provide voltage input and resistance measurements were located in a groove. These wires were brought through a hole in the groove to the interior of the yawsonde. The strain gages were semiconductor types and required amplification for telemetering. The output of the bridge circuit was not calibrated in such a fashion as to provide meaningful measurements of strain. Rather, the outputs of all units were adjusted for maximum sensitivity to variations in strain, i.e., vibrations. The output of the bridge circuit will be directly affected by the spin and yaw of the projectile; hence, yawsonde data are needed to interpret the vibration history of a particular projectile flight. The angular and spin motions of a projectile are traced by a yawsonde. The projectile motion is presented in terms of oN and 0 vs time. The complement of the angle between a vector drawn to the sun and a vector aligned with the spin axis of the projectile is aN, while is the derivative of the projectile's Eulerian roll angle with respect to the sun plane, i.e., the plane containing the missile's axis and the sun. The output of the strain gage bridge is an indicator of a fluctuating strain, and a spectral analysis can reveal the frequency content of these fluctuations. The presence of a particular frequency component implies that the projectile is experiencing a measurable mechanical strain at that frequency. For example, all projectiles experienced strains produced by the spin and yaw motions at the spin and yaw rates. As seen from Fig. 2, the Fourier transform of the bridge

The measurement of shalf torque in micro-alternators

In the technique described a resistance strain gauge bridge is used. The output from the bridge is amplified and used to pulse-width-modulate a 20 kHz square wave. The modulated waveform is extracted from the shaft, using split brass rings and carbon-copper brushes, and demodulated to give a continuous record of shaft torque. In this way distortion of the torque signal by electromagnetic radiation and variation in contact resistance between brushes and slip rings is eliminated.

Measurement of aerodynamic forces and moments with strain-gauge scales

For aerodynamic tests on models for aircraft extensive use is made of the strain-gauge scales [i] which comprise an elastic system 1 (see Fig. i) that senses and balances the forces acting on the model. The components X, Y, and Z of the total force vector Pf and the components Mx, ~, and M z of the total moment M are determined in the coordinates associated with the model's axes from the deformations of the elastic force. The origin of coordinates is chosen close to the model's nominal center of gravity. The deformation (strain) of the scales' elastic elements is transferred to the strain gauges 2 cemented to them and produces in the latter resistance changes proportional to the forces and moments acting on them. Signals from strain-gauge bridges to go electronic measuring equipment and then on to recording and processing apparatus.

Torsional Vibrations of a Boiler Feed Pump

The paper describes an investigation into the dynamic behavior of a large steam turbine-driven boiler feed pump, following the failure of gearboxes, couplings and bearings. The line consists of a 17 MW turbine driving a four-stage high pressure pump directly and a single-stage booster pump via a 2:1 single-reduction gearbox. Flexural vibration was measured using accelerometers at the bearings and eddy current proximity transducers. The torque transmitted to the gearbox was measured using a four-arm strain gauge bridge mounted in a coupling spacer shaft, the signals being obtained via a telemetry system. The observations showed a complex vibration pattern which was compared with predictions from simple analytic models. A lumped mass system accurately predicted the order of magnitude of oscillatory torque as a function of frequency, given the inevitable errors in gear manufacture. It was shown that the choice of flexible coupling has a crucial effect on the response. The methods of calculation have been generalized to give an accurate model of a system with distributed mass. This is achieved formally using the dynamic Green’s function approach or, for detailed results by a finite-element technique. It was shown that a change of coupling alters the dynamic torque of the system. Hence the effects of a number of changes were calculated and a suitable combination of couplings and gearbox were chosen to implement the practical solution to the problem. The basis for the choice is described and the implications for more general design criteria are discussed.

Design of a strain-gauge bridge to operate without an amplifier

The low-power output signal obtained from a wire strain-gauge is, as a rule, amplified. When making industrial tests in the damp and dusty atmosphere of underground mines, when testing farm machinery, and when using measuring transducers in metallurgical shops the adjustment and servicing of amplifiers involves considerable inconvenience and difficulty. Under these conditions it is convenient to work without an amplifier for the output signal by utilizing the so-called "high-power" strain-gauge transducers. The tensoresistors for them are specially made out of Constantan wire. The design of transducers with such tensoresistors is presented in [i].

Analytical and Experimental Investigation of Elastic Slider-Crank Mechanisms

Analytical and experimental dynamic bending stresses are determined for a slider-crank mechanism with a rigid crank and an elastic connecting rod. The mathematical model is derived by way of the lumped-parameter approach using d’Alembert’s principle and the Euler-Bernoulli beam equation. Viscous damping is included, and the resulting differential equations are solved numerically. Experimental data are obtained by means of strain gauge bridges mounted on the connecting rod. The effects on the elastic response of various parameters, including the crank speed, crank length, and slider offset, are examined. Comparison of the analytical and experimental results shows good agreement.

Improving strain-measurement accuracy when using shunt calibrations

It is conventional practice to consider shunt calibration of a strain-gage bridge in a manner which can result in erroneous tension-strain measurements. For strains from 1 percent to 10 percent as encountered increasingly in today’s structural materials and composites, the measured tension strains can be significantly lower than the actual strain. These errors are eliminated by using the method of determining ‘equivalent strains’ which is presented here. Shunt-calibration output is equated separately to tension-and compression-strain outputs to determine the ‘equivalent strain’ to be used for the reduction of each.

Quantitative tensile-tilting stages for the high voltage electron microscope

This paper describes a soft and a hard tensile stage for the high voltage electron microscope. Both stages can be combined with a top entry double tilting stage. The devices are driven by thermal expansion elements operating against water cooled parts. The drive mechanism shows smooth action with a relatively low response time and good long-time stability. The stages are equipped with strain gauge bridges for force and elongation measurements. The soft stage has a maximum load of 13 g, and a hard one reaches 1.5 kg.

A dynamometer to measure the forces on a sugar beet topping knife

A dynamometer is described which is designed to measure the cutting and vertical forces acting on a sugar beet topping knife, independently of their lines of action. The instrument is based on an extended octagonal ring, provided with strain gauge bridges, and can be fitted to a topper for field measurements. It exhibits linear force characteristics, with negligible hysteresis, and low interactions between the orthogonal measuring bridges. The calibrations show that some modification is necessary to design formulae based on a simple octagonal ring.

Balancing techniques for strain gauge bridges. 3F

Balancing techniques for strain gauge bridges. 3F

An X-ray strain rig and a versatile rosette strain-gauge monitoring bridge

An X-ray strain rig and a monitoring bridge specially designed for investigating X-ray elastic modulus anisotropy in cold rolled textured sheet is described. The rig is compatible with conventional Bragg-Brentano diffractometer geometry and back reflection camera methods and also the Seeman-Bohlin diffractometer geometry. It has improved rotation facilities which are useful particularly with low X-ray intensities in textured specimens. In addition, the rig can be accurately aligned, an aspect of the design which other workers appear to have overlooked. The X-ray strain rig has a load capacity of 2000 kg applied in uniaxial tension. The monitoring bridge has a resolution of better than 5 mu strain in the 0-1000 mu strain range and can measure up to 30000 mu strain.

Balancing techniques for strain gauge bridges

Four common methods of adjusting the resistive balance of a strain gauge bridge installation are described and compared. Effects on gauge factor and temperature stability are discussed and formulae are presented for the calculation of possible errors.

環境工学における市街地風の変動とその影響に関する研究-6 : 市街地における建築物壁面風圧の性状について

Wind pressure records, taken from two pressure transducers located at various levels of 30-40m tall buildings in Tokyo, are analyzed to determine mean pressure coefficients, spectiral function, cross-correlation functions and frequency response functions. Two differential pressure transducers, made of thin metal bellows with four-arm unbonded strain-gauge bridges, are used to measure the pressure differences between each of tapping points and the atmospheric pressure detector. The atmospheric pressure detector consists of pitot-static tube, nozzle and blowers. Jet. speed from the nozzle is about 60m/s and the atmospheric pressure can be detected when natural wind speed above the roof is less than 10m/s. Observational resuts are obtained as follows, i) The coefficient of variation of fluctuating wind pressure is proportional to the turbulent intensity of wind, and windward one is larger than leeward one. ii) Power spectral density of wall pressure is larger than that of natural wind above the roof in high frequency range. iii) Cross-correlation coefficient between windward pressure and natural wind speed is large at small time lag, and so is its coherency at low frequency band. Relating to leeward pressure, cross-correlation coefficient and coherency are small at small time lag and all frequency band respectively. iv) The values of amplitude gain and out of phase between windward pressure and square of natural wind speed are about 0.03 and zero respectively.

An apparatus for fatigue-testing of fibres

An apparatus has been designed and constructed to determine the effects of applied oscillatory loads on fibres. It includes a piezoelectric transducer to register the oscillatory loads on the fibre. This, combined with a strain gauge bridge system and suitable amplification, provides signals directly proportional to the maximum and mean load experienced by the fibre under test. These signals actuate a servomechanism which limits the desired maximum load experienced by the fibre to a constant value.

Automatic sensitivity control for a strain gauge-bridge

Automatic sensitivity control for a strain gauge-bridge

MEASUREMENT OF THERMALLY INDUCED PRELOADS IN BEARINGS

Strain gauge bridges and thermocouples on a waisted section of the shaft, with heated potted amplifiers rotating with the shaft, measure changes in preload due to bearing temperature changes in an experimental simplified mainspindle assembly.