铁磁试件应变损伤微结构蜕变的灵敏微分磁导率评价

为了精确检测和早期评价铁磁试件的应力集中状况和疲劳损伤程度，对灵敏微分磁导率检测技术进行了理论分析和试验研究。探讨了灵敏微分磁导率检测技术的基本原理和基本特征，研制搭建了灵敏微分磁导率检测的试验平台，对部分碳素钢结构材料的灵敏微分磁导率进行了测量，并采用测量低场磁化曲线的方法对碳素钢材料的灵敏微分磁导率进行了测量验证。理论证明了检测信号与微分磁导率成正比，试验发现20钢、35钢和235钢的灵敏微分磁导率即初始微分磁导率，并与振动样品磁强计低场磁化曲线的测量结果一致。对20钢，当拉应力接近断裂强度时，灵敏微分磁导率的变化量可达30%；对45钢，当拉应力接近断裂强度时，灵敏微分磁导率的变化量可达35%。可见，灵敏微分磁导率检测技术是一种新的高精度测量应力分布的检测方法，具有广阔的应用前景。

Evaluating of Microstructure Damage and Strain for Ferromagnetic Specimens Based on Sensitive Differential Susceptibility

In order to early and accurately test and evaluate the stress concentration situation and fatigue damage degree of ferromagnetic component, the sensitive differential magnetic permeability testing technique is to be theoretical analysis and experimental search. The basic principle and basic characteristics of the sensitive differential permeability detection technology are studied, and test platform has been successfully fabricated. Some experiments of measuring sensitive differential magnetic permeability are performed for carbon steel specimens. At the same time, further confirmation is realized by measuring initially magnetizing curve for carbon steel materials. Theory analysis testifies that the test signal is proportional to differential magnetic permeability. It shows that for 20 steel, 35 steel and 235 steel, the sensitive differential permeability is the initial differential magnetic permeability, which is verified by low field initial magnetization curve. For 20 steel, when the stress reaches the rupture strength, sensitive differential permeability is up to 30%. For 45 steel, when the stress is near the rupture strength, sensitive differential permeability is up to 35%. Experiments show that the sensitive differential permeability testing technology is a new high-precision testing method,and has broad application prospect.