Electromechanical impedance (EMI) is an important technique for bond-line integrity monitoring of adhesively bonded joints in automotive and aerospace structures. In the current work, numerical analysis of temperature sensitivity of the EMI technique is performed. The objective is to detect stiffness reduction of the adhesive in the presence of temperature and external mechanical load. Increase in the operating temperature can degrade the bonded piezoelectric material causing misinterpretation of the EMI data. EMI Signal features are numerically investigated to decouple the effect of load and temperature on the piezoelectric material in the mechanically loaded bonded joint. The computational results indicate higher dependence of EM resonance spectrum towards piezoelectric material matrix as compared to the tensile load applied on the bonded sample as the stiffness of adhesive is numerically varied.
High temperature (HT) environment in liquid metal cooled reactors poses major challenges towards development of ultrasonic transducer which is a key enabling technology for safety of reactors. In the current work, BS-PT (BiScO3- PbTiO3) piezoelectric material based ultrasonic transducer is proposed for the structural health monitoring at HT. Physics based model using finite element method simulates effect of temperature increase on the transduction ability of the BSPT piezoelectric material. Pulse-echo contact measurements are performed up to 260C which is the hot stand by temperature for liquid metal cooled reactors, to study the performance of the acoustic coupling agent and the BS-PT piezoelectric material bonded to a low-carbon steel sample. Experimental contact measurements indicate 6dB reduction in amplitude of the first backwall echo from 20C to 260C. Also, 0.1 MHz reduction in the fundamental and third harmonic resonance is observed in the spectral analysis of the first backwall echo.
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