Principles of piezo-based machinery health monitoring

In this paper methods used for structural health monitoring of machinery parts are discussed. These methods are based on applications of piezoelectric transducers. Proposed methods are used for assessment of structural machine parts manufactured of carbon fiber reinforced plastics/polymers (CFRP) and glass fiber reinforced plastics/polymers (GFRP). The first discussed method is based on elastic wave propagation and scanning laser vibrometry. This method is based on the fact that any kind of structural discontinuities cause changes in elastic wave propagation within the structure. In the proposed approach elastic waves are generated using piezoelectric transducer and then the waves are registered using scanning laser vibrometer. Here attention was paid on an analysis of elastic wave propagation in simple composite parts and parts with complex structure. The paper presents also results of simulated damage localization. The second method is an electromechanical impedance (EMI) technique. In this case piezoelectric transducer is also effectively used. This transducer is attached to an investigated structure. Due to electromechanical coupling of piezoelectric transducer and a structure, characteristics of mechanical resonances of the structure can be registered through the measurement of electrical parameters of piezoelectric transducer. An initiation of damage causes changes in resonant characteristics of considered structures. As electrical parameter very often impedance, admittance, resistance, conductance or reactance are used. For that purpose electrical impedance analyzer is used. Three parameters have been taken for the analysis. For proposed method effective damage indexes have been proposed