This study examines the potential of the Electro-Mechanical Impedance (EMI) method to provide an estimation of the
developed thermal stress in constrained bar-like structures. This non-invasive method features the easiness of
implementation and interpretation, while it is notoriously known for being vulnerable to environmental variability. A
comprehensive analytical model is proposed to relate the measured electric admittance signatures of the PZT element to
temperature and uniaxial stress applied to the underlying structure. The model results compare favorably to the
experimental ones, where the sensitivities of features extracted from the admittance signatures to the varying stress levels
and temperatures are determined. Two temperature compensation frameworks are proposed to characterize the thermal
stress states: (a) a regression model is established based on temperature-only tests, and the residuals from the thermal stress
tests are then used to isolate the stress measurand; (b) the temperature-only tests are decomposed by Principle Components
Analysis (PCA) and the feature vectors of the thermal stress tests are reconstructed after removal of the temperaturesensitive
components. For both methods, the features were selected based on their performance in Receiver Operating
Characteristic (ROC) curves. Experimental results on the Continuous Welded Rails (CWR) are shown to demonstrate the
effectiveness of these temperature compensation methods.
Xuan Zhu, Francesco Lanza di Scalea, and Mahmood Fateh, "Thermal stress characterization using the electro-mechanical impedance method," Proc. SPIE 10164, Active and Passive Smart Structures and Integrated Systems 2017, 1016407 (Presented at SPIE Smart Structures and Materials + Nondestructive Evaluation and Health Monitoring: March 26, 2017; Published: 11 April 2017); https://doi.org/10.1117/12.2258155.
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