Passive thermoelectric power monitoring for material characterisation

Monitoring deterioration of material properties is important for assessing the structural integrity of engineering components, as it may indicate susceptibility to damage. This article focusses on the example of thermoelectric power measurements, which are known to be indicative of thermal and irradiation embrittlement and may therefore act as a proxy metric for material integrity. A passive thermoelectric power-monitoring technique is proposed which is suitable for permanent installation on engineering components. In passive measurements, the active perturbation (in this case, the heating required to create a temperature gradient) is replaced by incidental perturbation from the environment. The reduction in the 'signal' amplitude associated with relying on incidental perturbations may be compensated by increasing the number of individual measurements, facilitated by the greatly reduced power demand of the passive modality. Experimental studies using a stainless steel tube as a test component demonstrate thermoelectric power accuracy of <0.03 mu V/degrees C is achievable with temperature gradients of the order of 2 degrees C; in many cases of practical importance, this is sufficient to track the anticipated changes in thermoelectric power associated with thermal degradation.