Stress Measurement Using Slip-initiation Phenomenon in Iron Foil

Abstract

By applying a slip -initiation phenomenon by fatigue in an iron foil attached to a specimen, the method of obtaining cyclic stresses acting upon the specimen at high temperatures is studied basically. Effects of elastic moduli of basic materials, speeds of cyclic loads and test temperatures on the critical stress of slip-initiation in the iron foil are examined. The critical stress of slip-initiation is dominated by cyclic shearing strain on the surface of basic material and becomes lower with a decrease of cyclic speed. As an application of the method, stress-concentration factors in notched specimens are obtained under various cyclic speeds and temperatures. The results are in good agreement with those obtained previously. It is concluded that the present method can be applied favourably for stress measurement at high temperatures up to 430°C.