The Alternating Current Potential Drop (ACPD) strain sensor has been developed as a tool to monitor the condition of a material. It is comprised of a square array of sensors that measures the resistance in two orthogonal directions, using the changes in the material’s resistance over time as a measure of its deformation and evolution of damage within it due to creep. The method expresses the change in resistance as the ratio of axial to lateral resistance, suppressing temperature-related effects on material resistivity, which are mostly isotropic.

Previous experiments have seen this method applied to samples of ferritic (2.25CrMoV) steel at 650°C [1]. Within this paper, the method has been extended to include work on the austenitic stainless steel 316H (17Cr11NiMo). Results of a series of interrupted creep tests are presented that show the resistance behaviour of the material at different points in its creep life. Metallographic studies have also been performed so as to establish how data gained using this technique is related to the condition of the material.

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