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Research On Structural Health Monitoring Based On Metal Core Piezoelectric Fibers And Lamb Waves

Posted on:2011-05-04Degree:DoctorType:Dissertation
Country:ChinaCandidate:J LiuFull Text:PDF
GTID:1118330338495798Subject:Instrument Science and Technology
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Metal-core piezoelectric fiber (MPF) is one of the new types of piezoelectric devices used for sensors and actuators. MPF has small size, and does not affect the performance of the structure when bonded on the surface or integrated with a host structure. Therefore, MPF has great potential to be used as actuators and sensors for structural health monitoring based on Lamb wave. Lamb wave sensing and generating using MPF is proposed, the principle of sensing and generating using MPF is researched, and the model of Lamb wave sensing is developed. Meanwhile, MPF using as a Lamb wave sensor is researched for structural health monitoring application in one-dimensional and two-dimensional stucture respectively. The major contributions and novel research results in this dissertation are summarized as follows:(1) The piezoelectric equation of MPF in cylindrical-coordinate system is developed. Based on the piezoelectric equation of MPF, the strain response formula of MPF boned on the surface of structure is derived. Then, the model of MPF's response to Lamb waves excited by circular crested actuator is derived and verified by experiments; the comparative study of MPF and circular PZT's response to Lamb wave is performed in the end, the results show that MPF has the capability of sensing Lamb waves.(2) The directivity of MPF's response to Lamb waves is researched using amplitude and wavelet transformation factor respectively. Taking A0 mode Lamb wave as an example, the sensitivity factor function of MPF's response to lamb wave excited by circular PZT is derived, and the result is verified by experiments. The result shows that MPF has high directivity to sense Lamb wave, the directivity characterized by wavelet transformation factor shows more clear in comparison with amplitude.(3) The principle of Lamb wave generation using MPF is researched, the Lamb wave generation and sensing system with MPF is then established, and verified by experiments. At the same time, the directivity of Lamb wave generation with MPF is researched by means of amptitude and wavelet transformation factor method respectively.(4) The changes of MPF's response to Lamb wave in different damage type (load, removable putty damage, hole) is researched, and then the response sensivity of Lamb wave to different damage is researched. The BP NN is successfully applied to distinguish three damage type and the health type.(5) According to Gabor wavelet transform to calculate time delay of damage signal, MPF is used as Lamb wave sensors for damge localization in one-dimension structure, the accuracy of damge localization is very high.(6) According to the principle of resistance strain rosettes, a novel method for two-dimension structure damage localization based on MPF rosettes is proposed. This method doesn't need the speed of Lamb wave in the medium, only need the amplitude of Lamb wave. The passive monitoring experiment (sound source localization) and active monitoring experiment (load localization and hole localization) are performed in two- dimensional Al plate, the accuracy of damge localization is very high, which confirms that the MPF rosettes method has the cability of damage localization in two-dimension structure.,...
Keywords/Search Tags:Metal-core piezoelectric fiber (MPF), Lamb wave, directivity, MPF rosettes, structure health monitoring
PDF Full Text Request
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