基于磁场梯度测量的磁记忆试验

Magnetic Memory Experiment Based on Magnetic Gradient Measurement

金属磁记忆检测是无损检测领域的新技术。为探索以磁场梯度为判据的磁记忆检测方法,采用自制的专用磁场梯度检测仪,在地磁场环境对棒状低碳钢进行拉伸试验。结果显示磁场梯度与应力的关系随测量方法不同有很大差异。当将试件原位放置在拉伸机上测量时,磁场梯度与应力之间没有确定的关系;当将试件从拉伸机上取下测量时,磁场梯度与近期曾经受到的最大应力成线性关系。通过测量铁磁性构件表面的磁场梯度,为非破坏性测量应力提供新途径。另外,磁记忆信号会随试件取下后搁置时间而逐渐减弱的事实,表明用金属磁记忆技术检测应力集中具有时效性。

Metal magnetic memory technology is a new nondestructive testing method.To explore a new diagnostic method based on magnetic gradient testing,a series of tensile tests on low carbon steel bars are carried out in geomagnetic field environment.A self-made special detector is used to measure the magnetic gradient above the material surface.The results show that the relation between the magnetic gradient and the stress varies with different measurement methods.The magnetic gradient has no specific relation to tensile stress if the sample is placed on the tensile testing machine and measured.If the sample is taken off from the machine and measured,the magnetic gradient shows a linear relation with the maximum stress that the sample was subjected to recently.It offers a new method for nondestructive measurement of stress by measuring the magnetic gradient on the ferromagnetic component surface.In addition,magnetic memory signal will gradually decrease after the sample is taken off and laid aside,which shows that the detection of stress concentration by using metal magnetic memory technique is time dependent.