Research On Relativity Of Crack Growths And Magnetic Memory Signal

To study the relativity of crack growths velocity and stress intensity factor range, we can analyze and detect the life of specimen, so we can prevent people and machine from accidents.Metal magnetic memory technology is a new NDT method, which estimates stress concentration of parts. Stress concentration appears before the flaw comes into being. So this method can forecast where will be first destroyed.metal magnetic memory technology can not only estimates stress concentration and early failures, but also estimates plastic deformation of metals effectively. To apply of metal magnetic memory technology to study crack growths velocity, we can obtain the relativity of magnetic memory signal and crack growths velocity with magnetic memory's advantage of convenience in the local in a new field. This provide us scientific foundation about fault diagnosis on operating machine.Based on this background, in this paper magnetic memory principle and its detection theory are studied firstly. Because magnetic memory principle is the foundation of application in actual engineering, it has been studied with magnetic mechanical effect theory and ferromagnetism energy balance theory.In order to realize the quantitative analysis of magnetic memory detection, the relation between metal mechanical characteristic and the distribution of magnetic memory signal has been studied by experiment. The stress experiment has been done both in single direction stress status and in double direction stress status, testing and investigating the distribution of magnetic memory signal, so that they can provide experimental data for quantitative magnetic memory detection.In this paper, on the basis of experiment and research, the blade of steam turbine is detected in work place. By evaluating the stress and analyzing the cause of rupture, the conclusion from magnetic memory technology is consistent with the failure fact, this further shows that magnetic memory technology is an effective tool in engineering practice.In order to realize the quantitative analysis of magnetic memory detection, the relation between metal mechanical characteristic and the distribution of magnetic memory signal has been studied by experiment. The stress experiment...