The Research On Fracture Behavior Of A Rectangular Superconductor Bulk With An Inclined Crack

Since the superconductivity was found more than a hundred years ago, the researchers had spared no effort to make a huge leap forward in the development of superconductors and superconducting technology. Especially in the past thirty years, the role which superconductors play in the production and practice becomes more and more important, as a series of high temperature superconductors(HTS) appear. The high temperature superconductors have been paid much attention because of the high critical parameters in practical application. Because the advantageous performance of HTS has become an indispensable technical support in certain industries, more strict requirements about them are put forward.As we know, the HTS are brittle material with high density defects. They are always subjected to a varying magnetic field in the practical application. The electromagnetic force flux-pinning-induced inside the HTS has a great effect on mechanical property. In this case, it is much easier for HTS to fracture. Therefore, we should think about their safety and stability in practice, while we make full use of critical parameters. Based on the background, the paper investigates the fracture property when there is an inclined crack in a rectangular superconductor bulk. In fact, the study on fracture problem of HTS has started in advance, and many scholars come up with different opinions. In this paper, the critical state Bean model is employed to estimate the effect of the complex electromagnetic force on the fracture behavior of the superconductor bulk which contains an inclined penetrable crack. First of all, the surrounding form of critical current is established according to the crack angle. In addition, the magnetic flux density distribution form could be get based on Bean model. Finally, the stress intensity factors, which are for two kinds of activation process, the zero field cooling and field cooling, can be obtained in decreasing process of applied magnetic field according to finite element numerical method. Numerical results obtained show that the crack length and the crack angle have significant effects on the fracture behavior. Generally, maximum of mode-Ⅱ stress intensity factor is much smaller than that of mode-Ⅰ stress intensity factor. That is to say, the mode-Ⅰ stress intensity factor plays a major role in the fracture damage of HTS. From the magnetizing mode point of view, the stress intensity factors that have been get in FC process are larger those which are obtained in ZFC process. The results indicate that FC magnetizing mode is more dangerous for superconductors in application. The stress intensity factors analyzed in the paper are useful to avoid fracture and mechanical failure of superconductors.