A Potential Drop Strain Sensor for In-Situ Power Station Creep Monitoring

Creep is a high temperature damage mechanism of interest to the power industry and at present lacks a satisfactory inspection technique. Existing material inspection techniques are extremely laborious while strain measurements rely on often infrequent off-load measurements. A quasi-DC directional potential drop technique has been suggested that is able to suppress the effects of permeability and is primarily sensitive to changes in resistivity and also the geometry that will develop through strain. The change in creep related resistivity is shown by an equivalent effective resistivity approach to be small at <2% change when compared to the >100% change in transfer resistance that occurs due to strain as observed in laboratory tests. A biaxial inversion is then presented and demonstrated on in-lab samples showing good performance. The result is a sensor that performs as a very robust high temperature strain gauge.