A portable magnetic Barkhausen noise (MBN) instrument for hardness and stress evaluation

This paper presents the design of a highly-integrated battery-powered portable instrument system for measuring magnetic Barkhausen noise (MBN) across a wide frequency range (1 – 100 Hz). The hardware and software architecture of the system is described in detail. Two miniaturized sensors are designed for taking measurements on flat surfaces and gear tooth slots respectively. Furthermore, a revised skew Gaussian distribution for curve-fitting the MBN signal envelope is proposed. Additionally, the measurement results are analysed using standard error analysis techniques, including standard deviation, relative standard deviation, and box plots, to evaluate the repeatability of the measurements. The accuracy and repeatability of the system under varying excitation frequencies are validated by comparing with a commercial product. Finally, representative MBN signal measurements are presented to demonstrate the system's capability in distinguishing materials with varying hardness levels, as well as in scanning weld cross-section for hardness mappings and residual stress evaluations.