Papers by Author: J.C. Zhang

Abstract: Metal magnetic memory testing (MMMT) technique is a kind of new NDT technique. It is interested by NDT area in recent years for its own advantages: early diagnosis, preventing sudden fatigue failure of equipments and the testing samples do not need to be magnetized. In order to find out the variation law of the residual magnetic strength of ferromagnetic material processed by different cutting method, axial tension tests about milling and flat surface grinding samples are completed in elastic and plastic deformation phase. The experimental results indicate that the magnetic strength variation law of two kinds of sample makes a great difference in the same deformation phase. The magnetic strength and standard deviation variation law of the grinding and milling samples are almost reverse. But there is a common ground of the two samples that when the material reaches yield phase, turning point occurs on both the residual magnetic strength and standard deviation curve. So we can identify whether there is plastic deformation according to the residual magnetic strength variation law of ferromagnetic material.

Abstract: The phase transition strain and magnetostrain during the martensitic transformation have been systematically investigated in Ni₄₆Co₄Mn₃₇In₁₃ Heusler alloy. A large phase transition strain with the value of about 0.25% upon martensitic transition has been observed, which is much larger than that in other metamagnetic shape memory alloys. In addition, such phase transition strain can be also obtained by the field change of about 50 kOe, exhibiting a large metamagnetic shape memory effect with nonprestrain. This behavior can be attributed to magnetoelastic coupling, which is caused by large difference in Zeeman energy between austenitic and martensitic phases.