Determining the parameters of the dynamic magnetic hysteresis loop of the structural materials by attachable primary transducers

Abstract

Coercive force, which is one of the structure-sensitive characteristics of ferromagnetic materials, is most often used for magnetic analysis. This approach requires the use of powerful magnetization systems, which leads to an increase in the size of the attachable magnetic probe and, accordingly, to a decrease in the locality of control. The above-mentioned disadvantages can be eliminated by using the parameters of the dynamic magnetic hysteresis loop (MHL), which involves the use of variable magnetic fields. A device for studying the dynamic MHL during cyclic remagnetization for the tasks of testing ferromagnetic materials, namely structural analysis, is proposed. The device consists of a generator of sinusoidal signals, an amplifier, a cur¬rent sensor, an attachable magnetic probe, a two-channel analog-to-digital converter (ADC), and a computer. The attachable magnetic probe is proposed in the form of a U-shaped core with magnetization windings on one leg and measurement winding on the other leg. The signal from the generator through the amplifier and the current sensor enters the magnetization winding. The ADC receives two signals: first one – from the measurement winding, and second – from the current sensor. Both signals from the ADC output in digital form are processed and analyzed by the computer using the developed specialized software in the LabVIEW language. Due to the developed software the filtering and integration of the signal from the measuring winding as well as the MHL plotting and MHL parameters calculation was realized. To reduce interference when determining MHL parameters, averaging over 50 magnetization cycles was performed. The attachable magnetic probe with the dimensions of the contact part 30x17 mm created a field with a strength of 300 A/m at a frequency of 50 Hz. The device was tested on specimens of sheet steel of 09G2S type with a thickness of 4 mm, in which uniaxial tensile stresses were created. The obtained results show the sensitivity of the dynamic MHL area to mechanical tensile stresses, as it increases from 14.8 to 16.8 mT A/m during loading.