Eddy current testing to detect welded zones in drawn wires

This thesis discusses how to detect weld defects of steel and stain steel wires welded by eddy current. A numerical modeled developed in MATLAB and EXCEL environment. Furthermore, experimental test setup has been designed using ProEngineer. In the beginning, it is shown how to calculate empty coil voltage and impedance that are useful to calculate filled coil voltage and impedance. Then, effective permeability and fill-factor are introduced to calculate coil voltage and impedance with test bar, which was more elaborated by making some comments about permeability and depth of penetration. At the next stage of this thesis, impedance modeled by MATLAB to show the effect of changing diameter, permeability, and represents maximum magnitude as well as real and imaginary parts of impedance. At this point, it is represented there are ferromagnetic steels that have to be saturated by applying magnetic field before the test in order to fix the permeability to reduce the noise and is explained how to design coil for saturating in EXCEL followed by demagnetization to reduce the residual magnetic field. Finally, 3 types of wire have been tested by different frequencies to find the optimum frequency to detect the mentioned defects. There is a wide range of excitation frequency for stainless steels however for each ferromagnetic steel there exists an optimum frequency value that has highest signal to noise ratio.