A statistical analysis of temperature compensation for piezoelectric sensor bonded to AISI-1080 material

Abstract

Electromechanical impedance (EMI) method has been widely used to evaluate structural health in recent years. In this method inexpensive, small, easy to apply, lightweight piezoelectric sensors are used to observe the changes in the structures. Different environmental conditions affect the piezoelectric sensor and the structure significantly. If the environmental impact is neglected, it causes misinterpretations as if it were present, although there is no construction defect. Therefore, it is necessary to compensate for the environmental effect. In this study, the EMI method was performed for AISI 1080 specimen at different environmental conditions. Impedance measurements were carried out between –45°C and –10°C. It has been observed that as the temperature decreases, the frequency shifts to the right and the amplitude increases. Temperature compensation was carried out to prevent these shifts. RMSD, MAPD, and CCDM were used as damage metrics. The effective frequency shift (EFS) algorithm was applied, and temperature compensation was performed according to the CCDM. As a result, damage metric values decrease after temperature compensation. Considering the change of damage metric values as a result of the compensation process, CCDM is a useful metric to detect changes. In the final stage, statistical tests (Pearson/Spearman and paired t-tests) were performed to compare non-compensated/compensated test results. Generally, damage metrics produce successful results in terms of statistical tests.