磁记忆信号定量分析的电子交换模型及性能

Electronic exchange model and performance of quantitative analysis of the magnetic memory signals

磁记忆法可以有效地判断铁磁性金属构件的应力损伤区域。但是,磁记忆自发漏磁信号形成机理和影响因素复杂,不同应力集中程度的磁记忆信号特征很难得到定量化分析,严重影响了该项技术的实际应用。根据电子自旋理论,建立了s-d轨道电子交换模型,计算了晶体屈服前后电子自旋态密度、原子磁矩、晶格尺寸的变化规律,进而定量分析磁记忆信号与应力集中程度的对应关系。研究结果表明,磁记忆信号与应力成一一对应的线性变化关系。晶体在屈服前,磁记忆效应主要由d轨道电子自旋作用决定,磁记忆信号与应力的对应关系具有很好的可重复性;晶体发生屈服后,电子自旋交换作用增强,d轨道电子自旋作用减弱,s轨道电子自旋作用增强,磁记忆信号变化幅度减小,磁记忆效应整体减弱。

The magnetic memory method can effectively determine the stress damage areas of the ferromagnetic metal components. However, the formation mechanism and complicated influenced factors of the spontaneous magnetic flux leakage signal make it hard to quantitatively analyze the magnetic memory signals under different stress concentration, and limit the practical applications. According to electron spin, the electronic exchange model of the s-d orbit is established, the changing rules of the electronic spin of density, the atomic magnetic moment and the crystal lattice size nearby the field of the crystal are calculated. Furthermore, the relationship between the magnetic memory signals and the degree of stress concentration is quantitatively analyzed. Results show that the magnetic memory signal varies linearly with the stress. Before the yielding stress appearing, the magnetic memory effect is determined by the electronic spin interactions of the d orbit, and the repeatability of the relationship between the magnetic memory signals and the stress is good. After the yielding stress appearing, the electronic spin interactions enhance, the electronic spin interactions of the d orbit weaken, the electronic action of the s orbit enhances, the amplitude of variation of the magnetic memory signal decreases, and the whole magnetic memory effect weakens.