Barkhausen Noise Properties Measured by Different Methods for Deformed Armco Samples

Abstract

The main goal of this research is the comparison of Barkhausen effect (BN) properties evaluated by means of two different methods: 1) using a ¿point probe¿ appropriate for industrial application; and 2) using a surrounding coil. The point probe contains ferrite core with searching coil perpendicular to the surface, and the sample is magnetized with a C-core electromagnet. Three quantities have been measured using first method: <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">V</i> 1- rms voltage over many periods, <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Nc</i> -number of BN pulses with amplitude higher than a given threshold, <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">V</i> 2-maximal value of the flux derivative in the C-core. In the second method, the sample is magnetized with external solenoid and voltage signal induced in surrounding coil is analyzed providing several quantities: hysteresis loop of magnetic flux density, envelopes of BN rms voltage and pulse count rate over one period of magnetization, <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">In</i> -an integral of the rms envelope, <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">N</i> -total number of pulses, <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">¿</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">m</sub> -maximal value of differential permeability. The samples made from Armco iron sheet have been plastically deformed by tensile load at room temperature up to <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">¿</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">p</sub> <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">=20%</i> . The differences in BN properties revealed by these two methods are discussed qualitatively and explained.