中文摘要：

提出采用裂纹区的应力场和应力-磁场理论来解释磁记忆检测原理,并通过采用磁偶极子模型来实现裂纹长度的定量化研究;对各种不同管道裂纹进行磁记忆检测,再对其磁记忆信号特征进行分析、研究。检测分析结果表明：裂纹尖端处应力集中且磁场出现最大值,磁场强度的法向分量也达最大值;而在裂纹中部附近,磁场强度的切向分量出现最大值,法向分量具有过零点特征。裂纹长度与磁记忆切向分量信号梯度峰值之间的距离和法向分量信号的波峰和波谷之间的距离近似成正比例关系。根据这一现象,给出了一个具有较好计算精度的确定裂纹长度的计算表达式,并用实验结果进行了验证。

英文摘要：

In this paper, the stress field and the stress- magnetic field theory for a crack domain are used to explain the principle of magnetic memory testing. The magnetic dipole model is employed to the quantitative research of crack length. The magnetic memory testing for different metal pipe cracks is made and the characteristics of magnetic memory signal are analyzed. It is shown that on the crack tip stress concentration appears, the magnetic field strength and it＇ s normal component reach the maximum. However, near the middle of the crack, the tangential component of the magnetic field intensity attends the crest and the normal component has zero-crossing feature. The crack length is approximately proportional to two parameters, the distance between the adjacent peaks of the tangential signal gradient, the distance between the peak and valley of the normal component of the signal. Based on the experiment, a calculation formula with good accuracy is suggested to determine the crack length and is proved by the experiment result.