PhD thesis defense to be held on June 29, 2023, at 10:00 (e-presence)

Picture Credit: Polychronis Pattakos


Abstract: This PhD thesis deals with the Development of Magnetic Circuits for Use in Autonomous Sensors Measurement of Internal Stresses in Steels and has a theoretical and experimental part. For the theoretical part, in Chapter 1 a Bibliographic Review is made in order to study the theoretical background on which the study is based of magnetic circuits, but also the overview of modern problems and methods in which this analysis is useful. In addition, there is a presentation of magnetic sensors, their usefulness and operation, and also reference to Non-Destructive Testing and the use of sensors as part of an Automatic Testing System. In Chapter 2 presents the Basic Principles of Magnetic Circuit Design. This involves the analysis of a simple magnetic circuit, the presentation of analogies with electric circuits and some elements of methodology which are necessary to understand the experimental part. In Chapter 3, the sensor arrangements that were studied, manufactured and were used to measure the Magnetic Permeability of steel samples in order to assess the deterioration of their mechanical properties and their stress from external stresses and other factors are presented. The sensor arrangements which are analyzed are the Single Sheet Tester, the yoke-shaped Magnetic Permeability Sensor with coil excitation, the Magnetic Permeability Sensor with Metglas core and the Permanent Magnet Device based on Hall sensor. In the Chapter 4 analyzes the construction methodology and the experimental use of an Energy Harvesting System. Then, this system is used in combination with the sensors that have already been analyzed for the autonomous construction measurement devices such as the Autonomous Magnetic Permeability Sensor, the Autonomous Permanent Magnet Device based on Hall sensors and the Multiple Hall Sensor Monitoring Device. Finally, Chapter 5 presents the conclusions of this thesis while analyzing some issues that arise as future work for further research in the field of magnetic sensors and their applications.

Supervisor: Professor Evangelos Hristoforou

PhD Student: Polychronis Pattakos