Research On NDT Device For Magnetism Material Properties And Stress Detection Based On Magnetic Barkhausen Noise

Ferromagnetic material has good adaptability in mechanical behavior and it is widely used in railway, transportation and construction industry. It is often used as the major bearing part to bear the weight and load. Its complicated stress state leads to stress concentration and localized plastic deformation. Besides, temperature stress due to temperature variation and residual stress due to processing technic always accumulate in the material. The metal construction will get defect and fatigue damage in long term service under these conditions. Magnetic Barkhausen noise method is used to detect the stress in the metal construction of lifting equipment in this thesis. To avoid volatility of magnetic Barkhausen noise features, and find the mathematical relationship between Barkhausen noise and magnetism property of ferromagnetic material, a new method of curvilinear integration was proposed based on the magnetization theory and the relationship between magnetic Barkhausen noise signal and hysteresis loop was studied. Some new features were extracted from the integration curve.To achieve the stress and magnetism properties detection in the metal, an equipment was designed with embedded chip. The interactive software based on ARM core and Android is introduced in the thesis. With the help of the stress detection equipment, four-point bending load experiment was carried out, and the feasibility of calculating hysteresis loop use the envelope of Barkhausen noise as well as the feasibility of evaluating stress use the new extracted features. Axial tensile experiment was also carried out on MTS810 servo hydraulic testing platform for Q235 steel specimen and the variation trend of features was studied. Influence of residual stress was also studied by comparison of three specimens, which provides base of stress calibration.