An application of computer image-processing and film replica technique to a nickel foil strain gage

The elastic stress of a specimen subjected to repeated loads is measured by a microscopic observation of slip-bands in nickel foil bonded to the surface of the specimen. The relation between the stress amplitude and the density of slip-bands in the foil is examined at various temperatures. An image-processing system using a personal computer is applied for an automatic measurement of the density of slip-bands in the bonded foil. The density of slip-bands replicated in a plastic film is also measured by the imageprocessing system, and it is in good agreement with the density of the original slip-bands. The peak stresses in grooved shafts under bending are measured using the nickel foil gage and the image-processing system. It is found that the results are satisfactority accurate.