微磁检测应力和塑性区的磁弹塑耦合理论

金属磁记忆微磁检测方法, 利用铁磁材料局部磁性状态的变化, 进行应力集中或塑性区域位置及程度的检测与评价. 面向微磁信号的定量理论分析可对其工程领域应用提供重要指导. 本文介绍铁磁材料微弱环境磁场下的磁弹塑性本构进展, 及其在微磁信号分析方面的应用. 力磁本构关系方面, 针对微磁检测弱磁化条件, 基于有效场理论构建了受弹塑性载荷铁磁材料的理想磁化本构的显式解析式, 并结合接近原理分析了恒定外加微弱磁场下应力-应变对材料磁化强度的影响. 检测信号分析方面, 基于弹性力学理论、静磁学理论和新建立的磁弹塑性本构关系, 建立并求解了微弱磁场下铁磁试件中弹性应力或塑性区诱导的表面磁信号的二维分析模型. 结合实验结果证实其在刻画弹塑性因素对微磁信号影响规律方面的能力, 并详细分析了微磁信号的特征量与局部弹性应力或塑性区的尺寸间的相关关系. 相比已有力磁本构关系, 本文建立的显式解析形式的理想磁化更加简洁, 有助于提升对力磁耦合效应的定量化理解和应用. 

THEORETICAL MODEL OF MAGNETO-ELASTOPLASTIC COUPLING FOR MICRO-MAGNETIC NON-DESTRUCTIVE TESTING METHOD WITH STRESS CONCENTRATION AND PLASTIC ZONE

The metal magnetic memory micro-magnetic non-destructive testing method can detect and evaluate the damage location and degree using the local change of magnetic state caused by the stress concentration or plastic zone of ferromagnetic materials. The quantitative theoretical analysis for micro-magnetic signals can provide important guidance for its engineering application. This paper reports on the research development of the magnetic-elastoplastic constitutive relationship of ferromagnetic materials under weak environmental magnetic field and its application in micro-magnetic signal analysis for the metal magnetic memory micro-magnetic non-destructive testing method. Regarding the research on the magneto-mechanical constitutive relationship, under the weak magnetization conditions of micro-magnetic testing, an analytical expression for the ideal magnetization constitutive relationship of ferromagnetic materials subjected to an elastoplastic load is established based on the effective field theory. Then, combined with the approaching principle between magnetization and ideal magnetization, the influence of the historical process of stress and strain loading on the magnetization under a constant and applied weak magnetic field is analyzed to consider the magnetization hysteresis effect. For the micro-magnetic non-destructive testing signal analysis, based on the elasticity theory, magnetostatics theory and the newly established magnetic-elastoplastic constitutive relationship, a two-dimensional model of the surface magnetic signal induced by the elastic stress or plastic zone in the ferromagnetic specimen under a weak magnetic field is established and solved by the finite element method. Combing with the exsting experiment results, the quantitative ability of theoretical model to describe the influence of elastoplastic factors on micro-magnetic signals is confirmed, and the correlation between the characteristic parameters of micro-magnetic signals and the size of local elastic stress or plastic zone is analyzed in detail. Compared with the existing magneto-mechanical constitutive relationship, the analytical expression of the ideal magnetization established in this paper is more concise, which helps to improve the understanding and application of the magneto-mechanical coupling effect.