基于磁记忆检测原理的应力磁化特征及磁化反转效应研究

Metal magnetic memory test technique is a kind of new method，has great market potential，which can early estimate stress concentrate status and evaluate fatigue damage of ferromagnetic specimen by measuring leak magnetic field. At present, it is only as an auxiliary means of detection, can not quantitatively and accurately estimate stress concentration and fatigue damage status of ferromagnetic specimen. Stress-magnetism and stress magnetizing reversal effect of ferromagnetic specimen are the key problems of setting up quantitative estimate system, which is belong to the elemental mechanism problem of metal magnetic memory test，and have few studying report on the field. Physical mechanism of the metal magnetic memory testing has not yet been unified understood. It is very necessary to research and solve the related basic problem. Here, experimental research, theoretical research and finite element simulation of three methods will be utilized to research stress magnetic effect and stress magnetizating reversal features in depth. Experimental research is groundwork and bedrock, the results of simulation is evidence，the key works are setting up the physical model of stress-magnetization and magnetizing reversal effect which will coincide to the experimental data. The key of studying and the emphases are including "model of stress equivalence to magnetic field", "permeability model of stress magnetization", and "energy balance model of stress magnetization". These physical models can reveal the the objective law of stress magnetization and magnetic reversal effect, and will reflect the relationship of stress magnetic reversal parameter versus outside enviromental condition. Studying results can be offered draw lessons for setting up metal magnetic memory testing quantitative evaluation system.

磁记忆检测技术是通过对漏磁场检测对构件的应力集中及疲劳损伤程度进行早期评价的新方法,具有巨大的市场潜力。但是，目前该技术还只能作为一种辅助检测手段，还不能准确定量地检测铁磁试件的应力集中和疲劳损伤程度。铁磁试件的应力磁化和应力磁化反转特征是建立磁记忆定量检测评价体系所面临的瓶颈问题，是属于磁记忆检测尚未得到统一认识的物理机理问题，对该问题的研究报道很少。本申请从试验研究、理论研究和有限元仿真三方面对应力磁化效应和应力磁化反转特征进行深入研究。以试验研究数据为基础，以仿真结果为佐证，从理论上建立和完善与试验数据相吻合的应力磁化、磁化反转效应的物理模型。重点研究建立应力磁化的"应力等效磁场模型"、应力磁化的"磁导率模型"、应力磁化的"能量平衡模型"。该物理模型能够揭示应力磁化反转的客观规律，反映应力磁化反转特征参量与外部条件的变化关系。该研究成果可为金属磁记忆检测定量评价体系的建立提供借鉴。

金属磁记忆检测技术以其操作简单、应用方便受到学术界的广泛青睐。目前，金属磁记忆检测技术的物理机理还没有统一的认识，还存在一些基础问题严重阻碍定量检测技术的进一步发展。对目前学术界存在的几种关于金属磁记忆检测物理机理方面的论述进行了研究，例如在环境磁场中应力作用的应变磁化理论、应力的等效磁场理论、能量最低应力磁化理论、应力和磁场共同作用的理论、应力的磁导率效应理论。研究发现各种理论都存在各自的局限性。金属磁记忆信号可有三部分组成，应包括有序应力磁信号、残余应力磁信号和待检试件结构磁信号。金属磁记忆的检测机理是由多因素相互作用的结果。待检试件结构磁信号的大小与构件缺陷的大小结构特征有关，与构件的铁磁性特征有关；有序应力磁信号是由单向拉力或压力引起的磁化漏磁现象，是可逆的和无磁滞的，随有序外力的消失而消失；残余应力磁信号是加载的有序应力消除后，由残余应力(无序应力)引起的磁记忆信号。试验研究验证：(1)磁记忆信号(对外显示的宏观漏磁场)与环境磁场有关，环境磁场具有磁激励作用，无环境磁场条件下应力不能产生宏观磁效应；(2)有序应力磁效应与待检构件的初始磁化状态有关，有序应力总是使试件从当前的磁化状态向环境磁场决定的无磁滞磁化状态逼近，表现为有些情况应力使试件的磁化状态增强，有些情况应力使试件的磁化状态减弱，并表现出不同的应力磁化速率；(3)有序应力的磁效应变化规律与待检构件的初始残余应力状态有关，在施加有序应力的初期，总是试图抵消残余应力的磁效应，在施加有序应力的后期，随着有序应力的增加和试件材料组织、磁畴、晶粒的变形，试件磁化状态增强;(4)有序应力具有使试件磁化状态增强和使试件磁化状态减弱两种趋势;(5)残余应力磁效应反应了试件具有残余应力的前例状况，残余应力越大，对应的磁化越强;(6)磁导率随应力集中、疲劳损伤的变化关系对磁记忆信号有一定的影响，对磁记忆信号只是部分贡献。（7）应力磁化反转的本质是残余应力磁场、有序应力磁场共同作用的结果,只有加载前试件具有较大的残余应力才具有磁化反转效应。该研究成果具有重要的理论意义，是进一步研究定量检测技术的基础。