基于OLCAO算法金属塑性变形磁记忆信号特征研究

塑性变形是金属材料在应力作用下产生损伤的早期阶段，对其的有效检测可预判危害的发生，实现设备破坏前的预警。针对金属磁记忆检测技术，利用量子力学密度泛函理论建立铁磁材料力磁耦合计算模型，采用原子轨道正交化线性组合法（Orthogonalized linear combination atomic orbitals，OLCAO）计算铁磁晶体在应力作用下的磁特性变化及磁记忆信号特征。结果表明：应力作用引起晶体内部电子运动状态及其分布特征改变，导致体系能带结构和电子态密度分布发生变化，材料的磁特性发生改变，定量表现为原子磁矩随应力的增加而变化。拉应力导致原子磁矩线性减小，压应力导致原子磁矩线性增大。当金属发生塑性变形时，体系的磁矩均发生突变，应力磁矩关系曲线出现拐点，变化速度变慢，表现为磁记忆信号的特殊变化特征。通过铁磁材料的拉伸及压缩试验，验证了理论计算结果的正确性。

Study on Magnetic Memory Signal Character of Metal Plastic Deformation Based on OLCAO Algorithm

The plastic deformation is the early damage stage of metal under the stress. It can pre-judge the danger and achieve to early warning for equipment damage through effectively testing plastic deformation. Aimed at metal magnetic memory, force magnetic coupling calculation model of ferromagnetic material is build based on quantum mechanics density functional theory. The orthogonalized linear combination atomic orbitals (OLCAO) algorithm is used to calculate the magnetic characteristic change and magnetic memory signal character of ferromagnetic crystal under different stress. The results show that the stress induces electron motion state and distribution character change inside crystal, and then results in the change of band structure and the density of electron states. Material magnetic characteristic changes. Atomic magnetic moment quantitative changes with stress increase. Tensile stress induces atomic magnetic moment decrease. Compressive stress induces atomic magnetic moment increase. When the plastic deformation of metal emerges, system atomic magnetic moment changes suddenly and the curve appears knee point, as well as change velocity decreases. The special change characters of metal magnetic memory appear. The correctness of theory calculation results is validated by tensile test and compression test of ferromagnetic material.