| It is an inevitable requirement to make health detection of board structure in engineering, for it’s easy to suffer damage in the manufacture and use of engineering structure (steel, aluminum and composite board, etc.). The guided wave detection technology based on the magnetostrictive effect is a potentially valuable research directions, this method is efficient, fast, non-contact, etc. This thesis makes a further research focusing on steel plate nondestructive testing using magnetostrictive guided wave technology, this research lays the foundation for practical engineering application. The thesis detail work was presented as follows:The first chapter analyzed the background and significance of the program, disserts the key technologies required by the program and introduced the latest domestic and international research status of ultrasonic guided wave theory and the magnetostrictive guided wave detection technologies.The second chapter studied the guided wave theory. Firstly, the mathematical model of the Lamb wave and SH wave in the plate was established. Then dispersion curves were calculated by matlab simulation and wave structure was also analyzed. The above studies provided a theoretical basis for the subsequent sensor design and test design.The third chapter studied the numerical simulation of steel plate detection using guided wave, simulated the different lengths of transverse cracks in the steel plate with the finite element method, the SHO mode guided wave excited in the steel plate was to achieve the detection of the steel plate defect. Then the reflection characteristic of the SHO mode guided wave for steel plate transverse cracks would be achieved. It was a preliminary study on the quantitative detection of guided wave for steel plate defect.The fourth chapter designed magnetostrictive guided wave sensors. Firstly, the mechanism of magnetostrictive SH mode guided wave was studied, which provided a theoretical basis for the design of the bias magnetic field and transmitting/receiving sensor. Then the adjustable bias magnetic field structure and the array magnetostrictive transmitting/receiving guided wave sensor were designed. This sensor structure has good directivity characteristics. Finally, a finite element analysis was carried for the magnetic field of the sensor.The fifth chapter involved the establishment of magnetostrictive guided wave detection system and the experiment study of steel plate detection using magnetostrictive guided wave. This detail work mainly included the descriptions of system modules, the design of the experimental program, the experimental studies of the steel plate transverse cracks detection using magnetostrictive guided wave sensor and the studies of magnetostrictive SHO mode guided wave beam pattern. The final experimental result would provide the basis for further design and improvement of magnetostrictive guided wave sensor.The sixth chapter summarized the achievements of the thesis, and give recommendations for further research. |
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