Research Of Magnetic Memory Testing Technology On Nondestructive Testing Of Representative Steel Structure

Metal magnetic memory (MMM) is a new technology in nondestructive testing technology that can find the dangerous areas whose characters were stress concentration in ferromagnetic components. It is suitable for early failure diagnosis and has great potential in the field of life prediction especially. So, it arouse great concern all over the world. However, as the developing time of the magnetic testing technology is very short, whose theories are not mature, there are some factors (imperfect testing) to restrict its use and development.Aiming at the problems of the technology, it is done for basic study with static tension and fatigue experiment, in order to gain the magnetic signals' characteristics in there different heat treatments for 18CrNiWA,45CrNiMoVA of tank steels.The check and measure is done by the initial magnetic memory signals of the two steels, which has processed. It shows that, the figures very small, and signals are pure, which indicate the effect of demagnetication is very perfect. It analyses the relation of magnetic signals and work stress by static tensile experiments. The research results reveal that, the curve of magnetic memory signals in the elastic and plastic loading phases had rules of inclined line. But, the rules in the two loading phases have obviously different characters. At the same time, the research reveals that: there are critical values of the Max,Min,Deta and |a| of magnetic memory signals have critical values, which become the warranty for judging stress concentration areas of highly dangerous state.The research on the changing principle of magnetic memory signals of various stress levels in different cycles for fatigue work pieces are done. The research results show that the corresponding relation should exist between fatigue cycles and the change of magnetic memory signals, and the patulous course of crackle can be pursuedThe experimental data are disposed by the method of magnetic value simulation. The equations of mathematics simulation are gained, and they are applicable to static tensile and fatigue experiments in the environment of laboratory.