Abstract
A nickel foil strain gage is devised for measuring the elastic surface stress of a specimen subjected to repeated loads at elevated temperatures up to 350℃. The elastic stress is measured by observing slip bands in the bonded foil resulting from repeated strains. The relation between the stress amplitude acting on the specimen and the density of slip bands is examined at various temperatures and different numbers of stress cycles. An image processing system is applied for an automatic measurement of the density of slip bands. The peak stresses in grooved shafts under cyclic bending are measured by the nickel foil gage and the image processing system. It is found that the results are satisfactorily accurate.
