Mechanical Strain Gauge Research Articles

Response of epoxy oversized models of strands to axial and torsional loads

As part of an extensive investigation on strand and cable properties, epoxy oversized models of strands have been manufactured using a newly developed technique. Axial and torsional loadings have been applied to the models. Strains, stresses and displacements have been determined using mechanical and electrical strain gages, dial gages and brittle coatings. The results obtained are compared with calculations using a previously developed theory. The response of a reference structure in which each wire is assumed to act independently is also compared with the response of the strand. Several discrepancies with theory are pointed out. It is believed that these are the first systematic measurements taken on strands.

Circular Land Cofferdam for Deep Excavation

Site conditions, dewatering, design, construction procedures and observations and stress measurements made during construction of a circular land cofferdam for a 79-ft (24.0-m) deep excavation for construction of a car dumper structure for Oak Creek Power Plant in Oak Creek, Wis., are described. The cofferdam consisted of wood lagging, soldier posts, four levels of concrete ring beams, and a lower caisson section. The concrete ring beams were instrumented with mechanical strain gages. Apparent earth pressure diagram computed from the results of the instrumentation is presented. Design and construction of the caisson section and the dewatering system are also examined.

Stresses in Pressurized Circular Shells With Discontinuities, With or Without Stiffeners

This paper is a summary of a series of five research programs dealing with the experimental determination of stresses, strains, and displacements in circular cylinders subjected to pressure. The vessels have either constant thickness or transverse reinforcing ribs. Circular holes, with either plain or reinforced edges, are located in different positions of the vessels. The methods used for the analysis are: brittle coatings, three-dimensional photoelasticity ("freezing" technique), and electrical and mechanical strain gages. The most important results are summarized in a table. These results will be of interest to designers of underwater ships and of pressure vessels in general.

Accuracy of various techniques used to measure strain in sub-surface operations

A number of mechanical, electronic and photoelastic strain gauges are being marketed today which are highly compatible and competitive with regard to thier initial cost, maintenance and suitability for sub-surface operations. Tests have shown that, in spite of their different partial and mean variation, these different types of instruments may be regarded as equivalent as far as their true accuracy is concerned.

A MECHANICAL STRAIN GAUGE FOR RECORDING PENILE CIRCUMFERENCE CHANGE

A MECHANICAL STRAIN GAUGE FOR RECORDING PENILE CIRCUMFERENCE CHANGE

Further notes on the Demec, a demountable mechanical strain gauge for concrete structures

Further notes on the Demec, a demountable mechanical strain gauge for concrete structures

The design and use of a demountable mechanical strain gauge for concrete structures

Summary This paper describes the principle, design and use of a form of demountable mechanical strain gauge which has been found particularly useful for determining strains in concrete structures. The instrument which uses a lever and dial gauge is cheap to make and use, and is located on 8 in. gauge lengths which are formed by pairs of punched and drilled steel discs glued to the concrete surface. With practice, 200 strains per hour may be measured with an accuracy of about ±5 × 10−6 under most laboratory test conditions. Even greater accuracy has been obtained using the gauge in its ideal horizontal position and with the readings lying within a small range on the dial. In development tests of this kind 90 per cent of measured strains were within ±3 × 10−6 of the mean. Tests on various locating discs show that normal, drilled mild steel discs give the best results.

RESIDUAL STRESSES IN ENAMELED SHEET‐IRON SPECIMENS*

AbstractA method of quantitatively measuring the magnitude of the stresses existing in porcelain enameled specimens is explained. The method involves measuring with a mechanical strain gauge the dimensional changes which occur when an enameled‐metal specimen is de‐enameled. The theoretical approach to the problem is reviewed, and equations are derived. The results obtained in tests on a series of ground‐coated specimens are presented and indicate that with a normal application of a commercial, 3‐frit ground coat on 20‐gauge enameling iron a compressive stress of about 35,000 1b. per sq. in. is present in the enamel.

The Electrical Measurement of Strain

The electrical measurement of strain is an art which has been developed gradually over a considerable number of years. It will be realised that the electrical measurement of strain includes the electrical magnification and measurement of a strain indicated by a non-electrical pick-up, such as a mechanical strain gauge, as well as the case of pure electrical measurement in which the pick-up unit itself operates electrically.The principal reasons for the popularity of electrical gauges are their ability to record data at a station remote from the point of application of the gauge, thus allowing gauges to be attached in positions which would be inaccessible for direct measurement by mechanical or optical means, and the high dynamic response of the electric gauge which renders the gauge invaluable for dynamic work.