Study on The Character of Metal Magnetic Memory Signal in The Course of High-cycle Fatigue Experiment for 16MnR Steel

1.School of Mechanical and Electric Engineering, Beijing University of Technology, Beijing 100124, China; 2. China Special Equipment Inspection and Research Academe, Beijing 100013,China Abstract: Fatigue damage is a slow process of accumulation of damage, there is no obvious macroeconomic plastic deformation, therefore the assessment of the security status about component bore alternating load would have a difficulty. Although there are many kinds of effective nondestructive testing methods currently, the structure of Equipment components and various unfavorable interference factors restrict the implementation of these methods. Metal magnetic memory method has been widely used in detection and experimental research project because of its characteristic: early detect on the flaw, easily accessible and accurate. But there are some questions which are the mechanism of magnetic memory method and characteristics of magnetic memory signal in the process of fatigue to be resolved. This article selects 16MnR steel as the fatigue specimen for research, the magnetic memory signal was tested in different fatigue life to study the characteristics of magnetic memory fatigue signal. The results showed that: fatigue cracks occur within the region where the magnetic field intensity curve is concave fluctuations; tiny crack is an important factor to change of the metal magnetic field intensity, and partial magnetic field changes which is caused by tiny cracks is a partial magnetic field effects; the magnetic signal curve changes in rates is tremendous in the region of fatigue crack, with the increase of the fatigue life magnetic field intensity change rate get to be larger than before ,and the gradient of magnetic field increases rapidly after the fatigue cracks germinated.