Monitoring of the Level of Residual Stress in Surface-Treated Specimens by a Noncontacting Thermoelectric Technique

Abstract

We have recently initiated the development of a noncontacting thermoelectric method based on magnetic detection of local thermoelectric currents in the compressed near‐surface layer of surface‐treated metals when a temperature gradient is established throughout the specimen. Beside the primary residual stress effect, the thermoelectric method is also sensitive to the secondary “material” effects of shot peening (local texture, increased dislocation density, hardening), but it is entirely insensitive to its “geometrical” by‐product, i.e., the rough surface topography. This method measures only the weighted average of the near‐surface residual stress, which is sufficient for quantitatively evaluating the degree of thermally‐induced stress release, but, in its present form, it is not suitable for detailed mapping of the residual stress profile. Preliminary results are presented for shot‐peened and low‐plasticity‐burnished IN100 nickel‐base superalloy specimens to show that the technique is also applicable to...