Development of magnetic imaging system for shape identification based on GMR sensor array

Non-Destructive Evaluation (NDE) is one of the most common methodologies used in the industries. This method is proposed to examine the properties of ferromagnetic materials. NDE technique carries the ability to perform shapes evaluation of ferrous objects without permanently altering its characteristics. The NDE technique used in this study for shapes evaluation is based on the magnetization characteristics of ferrous metal specimens. In NDT industries measurement time is a key feature. Therefore, using a single small sized Giant Magneto Resistance (GMR) sensor element to scan an object in a fine grid is in most cases not practicable. Alternatively, a sensor array housing several tens of simultaneously operating elements is more reasonable. In this study, it presents the performance study of an array lining up 21 pieces of GMR sensor developed for evaluating shapes of ferrous metal specimens. This thesis is made up of few chapters elaborating the development of Giant Magneto Resistance Sensor for Magnetic Imaging (GMR-mi) System. It is developed to do assessment for ferrous metal specimen`s shapes evaluation. Focusing only on ferrous metal specimens which are SS400 mild steel iron specimens with various shapes, the prototype of GMR-mi system confirmed the ability to do the evaluation. Magnetic images produced as the result of the shapes evaluation after following the development steps of building the prototype of GMR-mi system. Few components development, started with Signals Sensing Unit (SSU) started off the measurement sensing the magnetic flux perturbation in the system. Next, Signals Acquisition Units (SAU) continues with the transferring the captured data for later processed at Signals Processing Unit (SPU). These developments steps giving out a brief flow on how the development of GMR-mi system is function. Magnetic imaging system developed with NDE characteristics by fully utilized Magnetic Flux Leakage Testing (MFLT) principle. It is performed on the surface of target ferrous metal specimens. Target specimen is navigates underneath the sensing measurement area with magnetic field supplied by the induction coil. Induction coils create the magnetic field environment with supplied an amount of specific current I, thus making magnetic flux present between the thickness evaluation gap g. perturbation of magnetic flux density will occurred when it is in contact with a present of ferrous metal specimens. Finally, the prototype of Giant Magneto Resistance Sensor Magnetic Imaging System is developed. Performance parameters of Giant Magneto Resistance Sensor Magnetic Imaging System are listed which are current I, induction coils number of turn n and thickness of evaluation gap g. In addition, all the experimental results have been studied and presented in this thesis. Firstly, it explains the ability of the system in visualizing the shapes of ferrous metal specimens with magnetic images. Next, all results presented showing the capability of this system in visualizing the shapes of ferrous metal specimens from the actual ferrous objects are having the same capabilities as other magnetic imaging technique. Last but not least, the effect of perpendicular gap towards accuracy of Giant Magneto Resistance Sensor Magnetic Imaging System for ferrous metal specimen is studied. According to the brief studies and assessment of all the magnetic images, the optimized perpendicular thickness of evaluation gap g is 7mm. Summing up, Giant Magneto Resistance Sensor Magnetic Imaging System is capable to evaluate the shapes of ferrous metal specimens.

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