Noncontact spatiotemporal strain mapping of composite multiferroic cylinders

International Journal of Mechanics and Materials in Design - Recently, the reinvigoration of research interest in in strain-mediated composite multiferroic structures resulted in translational...     

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.     

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.     

Direct pneumatic pressure in a clamping technique during strain gauge bonding

A technique is described for the clamping of metallic foil strain gauges during epoxy adhesion bonding to non -porous surfaces. Following application of the uncured adhesive, the gauge is conformed to the surface using self-adhesive tape and the workpiece placed in a pressurised environment for the duration of cure. The pnematically derived clamping pressure is transmitted directly to the glue line, and is equal to the pressure within the containment vessel. Since the clamping pressure is both uniform over the strain gauge area, and readily reproducible between installations, it is possible to produce consistent gauge performance. The technique may offer time and cost advantages over classical clamping methods where gauges are installed on small, intricate, or batch components in stress analysis and transducer applications.     

Ring gauge for biaxial strain analysis

The ring gauge performs the same function as a strain gauge rosette by providing three independent signals from which may be deduced the three unknowns in a biaxial strain system, viz. the magnitudes of the principal strains and the directions of the principal axes relative to a datum direction. It is analogous to a delta rosette but possesses advantages over the usual method of cementing three gauges to the surface of the material.     

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.     

Method for computing temperature characteristic of a wire-wound strain gauge

Summary Both the theoretical and experimental data show that it is possible to apply the above technique in a general case for calculating, without the necessity of testing, the temperature characteristic of a strain gauge glued to any material providing it is supplied with a certificate indicating in the given temperature range the properties of the wire ( _R, ₁) and of the wire network (S, R). Such a condition will exist if the manufacture of strain gauges with differing characteristics is centralized.     

Applications of operational amplifiers in strain gauge circuits

Operational amplifiers, originally developed for analogue computation, are now widely used in analogue instrumentation, signal conditioning, servo controls, voltage and current regulators and an extensive range of other functions. In experimental mechanics, operational amplifiers are ideally suited to applications involving strain gauges. Both Wheatstone bridge and ballast (potentiometer) circuits are examined together with the limitations and constraints imposed by amplifier and external circuit considerations. These limitations are important, whether relatively simple operational amplifiers or the more complex instrumentation amplifiers are used. Many manufacturers provide a wide range of 'off-the-shelf' integrated circuit and discrete amplifiers, together with comprehensive specifications, permitting selection of a suitable device. Before discussing strain gauge applications, the properties of operational amplifiers will be reviewed briefly.