Loading monitoring in presence of cracks using magnetic sensors

• Main Author: Che, Maohao
• Other Authors: Soh Chee Kiong
• Format: Final Year Project
• Language: English
• Published: 2016
• Subjects: DRNTU::Engineering
• Online Access: http://hdl.handle.net/10356/67929
• Institution: Nanyang Technological University

In the field of structural health monitoring (SHM), the studies on lead zirconate titanate (PZT) transducer using electromechanical impedance (EMI) had been carried on for several decades. These PZT sensors are thin/ thick patches that are few centimetre square in the area which can be square, rectangle and circular shaped made of piezo ceramics. Among all the mainstream studies, the conventional application method is to attach these PZT transducers to host structures by surface bonding. Under electromechanical field, PZT serves as both actuators and sensors, and hence generate unique electromechanical (EM) signatures for further analysis. In most of the cases, attachments of PZT transducers on host structures are accomplished by adhesives or methods that fix transducers to the surface of host structures permanently. As a result, the attached transducers are not available for any other future use, and with permanent occupancy on structure could disturb it to some extent. In some cases, the permanent occupancy is not allowed especially on machines. Consequently, one solution is to propose bonding-free methods such as thumb force, contact pressure or nut bolt. These are alternatives when adhesives cannot be used in several situations, especially for finished mechanical products. This final year project introduces permanent magnets as an attaching method and testifies the workability of magnetic PZT sensors in monitoring loadings and cracks. Furthermore, whether the magnetic PZT sensors can provide continuous and reasonably accurate EM signatures when been removed and reattached on the same locations of the host structure is tested under the identical boundary conditions was studied. Lastly, one test was carried out on monitoring impact/dynamic load to justify the usability of magnetic sensors in the field other than static, and continuous loading, and damage detection. Experimental outcomes are validated by statistical Root Mean Square Deviation (RMSD) method.