Performance of metal-foil strain gages during large cyclic strains

Constantan-alloy gages with polyimide backing were bonded to axial-fatigue specimens which were tested under cyclic loading. Constant-strain ranges between 0.0075 and 0.04 were applied to each specimen by means of a clip on extensometer, and the strain-gage signals were monitored for gage accuracy and life. Gage life varied upwards from about four cycles at the highest strains investigated. Although significant zero shift occurred, strain ranges were generally measured within five percent over most of the life of the gage. The gage-performance information obtained will aid in later study of local strain and low-cycle fatigue in notched members.