Adaptability of a Strain Gage Made of Nickel Foil to Variable Test Temperatures : In Cases of Directly Rising Temperatures

When nickel foil strain gages are stuck on the surface of a specimen subjected to repeated loads, the elastic stress is measured by observing slip bands in the foil gages resulting from repeated strains. Calibration studies with rotating-bending tests at temperatures from 100°C to 350°C are performed on round steel bars with nickel foil, and the threshold stresses for the first appearance of slip bands are examined at variable temperatures rising directly. Furthermore, assuming that the first appearance of slip bands is subject to the linear cumulative damage law, the threshold stresses at the variable temperatures are calculated from those obtained by the calibration tests at several definite temperatures. The peak stresses in grooved shafts subjected to bending at the variable temperatures are measured with the nickel foil gages. The results are compared with those obtained previously by various methods.