Abstract
A brief description is first given of the properties and method of using wire-resistance strain-gauges, indicating their sphere of usefulness and limitations, and the factors affecting their accuracy and stability, such as method of application, temperature, and moisture.
The determination of static strain, using a simple bridge and galvanometer method, is illustrated by reference to measurement of strain in public service vehicle road wheels due to inflation of the tyre and the axle load.
Dynamic strain determination is discussed with reference to measurements made on the frame and superstructure of a double-deck public service vehicle under road conditions, and typical strain records are given. Portable four-channel dynamic-strain recording equipment developed at the Motor Industry Research Association (M.I.R.A.) especially for this type of work, and which is sufficiently free from microphonic signals generated by road shock, is described. This equipment consists of an A.C. polarized bridge, oscillator, amplifiers, and power supply, and recording is by photographing cathode-ray tubes.
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