An Application of Image-Processing to Stress Measurement by Copper Plating Foil (On the Effect of Frequency, Stress Ratio and Stress Waveform)

Abstract

Strain gauges made of copper plating foil are devised for measuring the elastic surface stress of machine parts in operation. The elastic stress is measured by observing slip bands in the bonded foil. Calibration studied by cyclic tension test with various frequencies, various stress ratios and different stress waveforms are performed on round steel bars with copper plating foil. It is verified that the relation between the threshold stress for the first appearance of slip bands and the number of cycles are not affected by the stress ratios and stress waveforms, but the frequency. Using a computer image-processing system, the density of slip bands in a microscopic image of the bonded foil is analyzed automatically and quantitatively.