Experimental Investigation Of Ferromagnetic Materials Stress Based On Magnetic Barkhausen Noise Detection

Ferromagnetic materials have been widely used in industries for a long time, such as mechanical equipment, instrumentation, water conservancy, electric power equipment, defense weapons and so on. Stress concentration is main reason to cause fatigue failure and damage. However the early damage is very difficult to be taken effective evaluation. With the development of the Barkhausen noise technology, it has begun to be widely used for the evaluation and testing of the ferromagnetic material microstructure and residual stress. The main content of my topic is, to complete intelligent testing equipment which is based on the research of the theoretical of Barkhausen noise and combination of the cause and impact of stress concentration. Meanwhile, analyzed the impact of stress on MBN noise signal from different depth view. Many experiments are done to explore the relationship between different depth stress distribution and MBN noise.First, based on the electromagnetic theory, this thesis analyzed the generation nature and testing mechanism of Barkhausen signal, introduced the MBN signal characteristics, deeply studied the main physical factors of Barkhausen signal, including magnetic field intensity, stress and microstructure, etc. Then, on the basis of the preliminary work we set up the intelligent testing equipment which is based on the theoretical of Barkhausen noise, and introduce each part of the hardware and software of the equipment in detail. Finally, according to the skin effect, the different analytical frequencies of MBN signal corresponds to different signal propagation depth, the experiment extracted root mean square of three different frequency-bands of MBN signal, analyzed the relationship between distribution of stress and MBN noise. Besides, in order to eliminate the influence of lift-off, BP neural network model is introduced to eliminate the interference factor.