铁磁性材料热老化磁声复合检测技术研究及仪器研制

The primary coolant pipes of nuclear power plants and the ultra-supercritical thermal power generating units are mainly made of ferromagnetic materials. The service life and structural safety of ferromagnetic materials will be directly affected due to thermal ageing as long-term work under high temperature and high pressure. Limited parameters can be extracted to characterize thermal ageing of ferromagnetic materials by using existed nondestructive testing methods and therefore these methods cannot meet the needs of engineering testing. In this project, based on electromagnetic acoustic transduction mechanism, a magneto-acoustic compounding inspection technique is proposed for nondestructive evaluation of thermal ageing of ferromagnetic materials. Thermal ageing of ferromagnetic materials is characterized by material mechanical properties including hardness, yield strength and fracture toughness. Combining the effect of the Lorentz force mechanism and the magnetostrictive effect mechanism, the properties of the electromagnetic acoustic transduction characteristics will be analyzed in the ferromagnetic materials. The effect of material electromagnetic properties, bias static magnetic field and excitation current on magneto-acoustic compounding signals will be investigated. A new type of magneto-acoustic compounding transducer will be designed and optimized. A corresponding inspection instrument will be developed for thermal ageing inspection of ferromagnetic materials. A decoupling algorithm will be developed to realize the decoupling of eddy current signals, Lorentz force ultrasonic signals and magnetostrictive ultrasonic signals in magneto-acoustic compounding signals. Based on above investigation, a mapping model between acoustic properties, electromagnetic properties and material mechanical properties will be established to realize comprehensive characterization of multiple properties of thermal ageing of ferromagnetic materials.

核电站一回路主管道和火电厂超（超）临界机组主要为铁磁性材料。铁磁性材料长期工作在高温高压环境下易产生热老化，直接影响材料使用寿命和结构安全。目前已有的无损检测方法用于铁磁性材料热老化的表征参量有限，无法满足工程检测需求。本项目拟发展一种基于电磁声换能机理的磁声复合检测技术，用于铁磁性材料热老化的无损评估。利用硬度、屈服强度和断裂韧性等材料力学参量表征铁磁性材料热老化。考虑洛伦兹力机理和磁致伸缩效应机理的综合作用，进行铁磁性材料中电磁声换能特性的参量分析，研究材料电磁参量和偏置静磁场、激励电流等参量对磁声复合信号的影响。设计并优化一种新型磁声复合传感器，研制一套检测仪器，用于铁磁性材料热老化检测。发展磁声复合信号解耦算法，实现磁声复合信号中涡流信号、洛伦兹力超声信号和磁致伸缩超声信号的解耦。在此基础上，建立声学参量、电磁参量与材料力学参量之间的映射模型，实现铁磁性材料热老化的多参量综合表征。

铁磁性材料长期服役于核电站、火电厂等高温环境下，由于温度持续作用，材料微观结构易发生改变，引起金属材料力学性能退化，即铁磁性材料发生热老化。铁磁性材料热老化严重影响金属构件使用寿命和结构安全。目前已有的无损检测方法用于铁磁性材料热老化的表征参量有限，尚未完全实现金属材料热老化全面的定量评估。本项目面向铁磁性材料发生热老化引起力学性能退化的问题，发展了一种基于电磁声换能机理的磁声复合检测技术。考虑洛伦兹力机理和磁致伸缩机理作用研制了新型先进的电磁声传感器。针对电磁铁式电磁声传感器检测的需求研制了电磁铁式电磁声传感器检测系统，通过检测实验验证了所研制检测系统的合理性和实用性。发展了电磁声传感器检测信号解耦算法，提取电磁声传感器检测信号磁声特征参量。建立了磁声特征参量与铁磁性材料力学性能参量映射关系，基于神经网络建立力学性能退化定量预测模型，实现了铁磁性材料热老化的定量评估。