Abstract
Strain gages made of nickel foil are developed for measuring the elastic surface stress of machine parts in operation. Sticking a piece of nickel foil about 10 um thick on the surface of a specimen subjected to repeated loads, the elastic stress is measured by observing slip-bands in the foil resulting from repeated strains. Calibration studies with rotating-bending tests are performed on round steel bars with nickel foil to determine the applicable test temperatures for the gage, and to establish the relation between the threshold stress for the first appearance of slip-bands and the number of stress cycles. The peak stresses in grooved shafts under bending are measured with the nickel foil gages, and the accuracy of the results is examined.
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