助基于磁梯度张量的金属磁记忆检测方法

金属磁记忆是对铁磁材料早期微观损伤及应力集中进行无损检测的有效方法。为提高磁记忆检测的可靠性，充分利用磁记忆信号的矢量信息，将磁梯度张量测量及分析方法引入磁记忆检测中。根据张量缩并分析理论得到了磁记忆信号的磁梯度张量模量，通过求解梯度局部相位的一阶导数得到信号的梯度局部波数，然后分析信号的磁梯度张量模量和梯度局部波数分布特征，得到磁梯度模量和梯度局部波数极值点分别与应力集中边界和中心位置的对应关系。实验结果表明：磁梯度张量方法能够克服检测方向与缺陷夹角变化对测量信号的影响，准确地对应力集中进行判断。

Metal magnetic memory test method based on magnetic gradient tensor

Metal magnetic memory (MMM) test technology is a nondestructive testing method, which can detect the early micro damage and stress concentration of ferromagnetic material. In order to improve the reliability of the MMM test and making fully use of the vector information in the magnetic memory signal, a novel MMM test method based on magnetic gradient tensor measurement and analysis is proposed. According the analysis theory of tensor contraction, the magnetic gradient tensor modulus of the magnetic memory signal is obtained, and the gradient local wavenumber of the signal is achieved through solving the first derivative of the gradient local phase. Through analyzing the distribution characteristics of the magnetic gradient tensor modulus and gradient local wavenumber, the relationships between the extreme points of the magnetic gradient tensor modulus & gradient local wavenumber and the stress concentration border & central position are obtained, respectively. The experiment results show that the method based on magnetic gradient tensor can overcome the influence of the angle change between the detection direction and defect on measurement signal, and judge the stress concentration accurately.