An investigation of electromagnetic rig-generated strong magnetic fields
Ekreem, Nasser B. (2009) An investigation of electromagnetic rig-generated strong magnetic fields. PhD thesis, Dublin City University.
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In this thesis, two alternative solenoid designs are presented: 'Air-core' coil design and 'C-shape' coil design. The coils were designed to be capable of generating strong and static magnetic fields in various samples of magnetic materials. In the case of the first design, the sample would be placed in the central air space. In the second design, the sample would be placed in part of the 'jaws' of the 'C' shape. It was intended that the rig would be used to measure the magnetostriction strain of annealed cobalt ferrite and Terfenol-D based materials. It was thought that magnetic flux densities of the order 1.6 tesla would be needed in the air-gap. However after carrying out preliminary calculations for the air-core design, it was realized that very high electrical currents would be required, with the result that complex systems would be needed to remove the heat being generated. This design was therefore abandoned.
The 'C-shape' coil design was completed allowing for fabrication and experimental performance measurement.
The thesis also presents comparisons between the experimentally generated magnetic field strengths and values generated from modelling the structures using Finite Element Method Magnetics (FEMM) software. It had been assumed that the experimental measurements would be almost the same as the original design calculations and predictions of the software. However the experimental results fell far short of both the calculated magnetic field strengths and the values predicted by the software. Magnetic flux densities in the range of 1.03 tesla were achieved.
The discrepancies could be due to changes in the magnetic properties of the core material. Drilling and machining of these components could have produced skin effects and other regions of poor magnetic properties. The effects could be exaggerated or diminished, depending on the exact configuration of the 'C' shape.
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