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Consideration of Thermal Effects in Electro-mechanical Impedance Measurement for Space Structures

M. L. ANDERSON, A. N. ZAGRAI, D. DOYLE, D. HENGEVELD, M. R. WILSON

Abstract


Space structures and structural health monitoring (SHM) systems are exposed to numerous hazards in the extreme environment of space. Investigation of the effect of these hazards on SHM is critical for proper operation of spaceship diagnostic systems. Recent studies have indicated utility of electro-mechanical impedance and elastic wave propagation methods for structural condition assessment in space. In this contribution, we report experimental studies of thermal effects on electromechanical impedance responses. For proper imitation of space thermal environment, electro-mechanical impedance responses of piezoelectric sensor and aluminum beam were collected for different temperatures in a vacuum chamber. Positive and negative temperature variations were considered and a hysteresis effect was investigated. The results generally confirm a conclusion from previous studies showing decrease of natural frequencies with temperature increase under standard atmospheric conditions. The opposite was observed for decreasing temperatures. However, at the temperature of 65 ºC a significant change in the amplitude of the impedance has been observed. Possible explanation of this phenomenon is suggested. The results demonstrate the importance of environmental thermal contributions and advocate for including thermal effects in automatic structural health monitoring algorithms for space systems.

doi: 10.12783/SHM2015/356


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