The Proceedings of the Dynamics & Design Conference
Online ISSN : 2424-2993
2016
Session ID : 533
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Evaluation of Bolted Joints Based on Nonlinear Piezoelectric Impedance Modulation
Yusuke FUJIIArata MASUDA
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Abstract

In this paper, a health monitoring methodology for a structure with bolted joints based on nonlinear piezoelectric impedance modulation method is presented. This technique uses a single piezoelectric active sensor bonded on the structure surface, which is driven by a high frequency harmonic voltage source. When the structure including a contact surface such as a bolted joint is subjected to a pump excitation at low frequency, the induced structural vibration causes a fluctuation in the driving point mechanical impedance at high frequency range because of the contact acoustic nonlinearity at the contact surface in the structure. This causes a modulation of the coupled electro-mechanical admittance of the piezoelectric active sensor, which can be observed as the amplitude modulation and the phase modulation of the current. It is known that loosening the bolt causes weakening of the contact pressure on the joint. This may result in more significant fluctuation of the contact conditions under the pump loading, leading to stronger modulation of the admittance. Experiments conducted using a bolted beam specimen showed increasing damage index as the bolt loosed. In addition, to obtain deeper understanding of the relationship between the pump load and the contact stiffness fluctuation we did an experiment measuring piezoelectric admittance when the specimen was subjected to a static load. The result suggests that the load applied to the bolted joint may affect the attenuation of the high frequency elastic wave at the joint.

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© 2016 The Japan Society of Mechanical Engineers
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