Research Status and Critical Problems of Metal Magnetic Memory Testing

As a novel magnetic nondestructive testing method, the metal magnetic memory (MMM) technique has received extensive attention since it was first proposed. It can be used to assess stress concentration, early damage, and the degree of damage. However, previous studies primarily focused on component experimental research of MMM. Thus, studies of physical models and stress quantitative evaluations have been insufficient. This review outlines the research status and advances of MMM mechanisms, the influence factors of magnetic signals, the appraisal parameters for damage, and the basic experimental research conducted both domestically and internationally. Some critical problems of MMM that must be resolved are examined and the future trend of MMM development is discussed. The results of this review reveal that the influence factors of MMM signals are complicated and that systematic experiments are inadequate, which thus hinder the quantifiable development and engineering application of the MMM technique. Before a stress quantitative evaluation by the MMM technique can be conducted, the influence factors and degrees of MMM signals must be confirmed. Existing evaluation parameters proposed by different researchers have been shown to be suitable only for specific conditions and specimens and thus cannot provide comprehensive analysis for random specimens. The quantitative evaluation parameters of the MMM technique must therefore be further researched. Previous studies of the MMM technique conducted uniaxial tensile and fatigue experiments but rarely performed bending tests. Indeed, many structural members are subjected primarily to bending and shearing stresses during service. Clearly, to apply the MMM technique to a building's steel structure, research on the effect of bending and shearing stresses on MMM signals must be performed. © 2019, Editorial Department of China Journal of Highway and Transport. All right reserved.