Experimental Research on Metal Magnetic Memory Method

摘要

Metal magnetic memory (MMM) method is a novel, passive magnetic method for inspecting mechanical degradation of ferromagnetic components. To promote a further understanding of the relation between the magnetic characteristics and mechanical deformation, the normal spontaneous stray field component and its gradient of Q235-steel specimens were measured during uniaxial tensile and compressive loading processes. The results show that the normal spontaneous stray field component and its gradient are effective in capturing different deformation stages under tensions, but no detectable change can be found during the whole compressive loading processes. Compared with the amplitude of the normal spontaneous stray field component, the gradient is a more sensitive parameter. In addition, the result demonstrates that it is easy to differentiate macro-crack and plastic deformation because the differences among measured spontaneous stray field signals are obvious. Moreover, various factors affecting test results were also considered.