Localized stress relaxation by impression testing

Abstract A small flat-ended cylindrical punch was impressed onto the surface of an LiF single crystal. The impression was made in an Instron at a constant cross-head speed. At a certain depth of the impression the crosshead was stopped and the load relaxation with time was recorded. It was found that the velocity-stress exponent for dislocation motion obtained in this way was identical with that obtained by conventional stress relaxation techniques using bulk samples. However, this new method caused only local deformation of the specimen and used very little material in the process.