基于高能电磁脉冲激励的金属构件早期疲劳损伤定量检测方法研究

Accurate nondestructive evaluation of fatigue damage in early stage is of great important for improving equipment quality and reliability and is also the key for the life prediction and failure analysis of high strength metal structure. Nonlinear ultrasonic method has an enormous potential for micro-defect testing. Since there are some problems, such as, nonlinear interfering resource caused by acoustic couplant and the unclear correspondence between loading, defect and response, a multi-field coupled model based on material magnetic characteristic is proposed and the Electromagnetic Acoustic Transducer (EMAT) is introduced to solve the extra nonlinear noise in piezoelectric ultrasonic testing. In this project, a model with fatigue damage is set up in the way of high-energy electromagnetic loading, including the interaction among electric field, magnetic field and mechanic field. In our project, the purpose is to study the nonlinear dynamic response of the fatigue damage under the high-energy electromagnetic load and to discover the relationship between the load, the defect and the detection signal. The using of electromagnetic ultrasonic transducer drived by high-energy electromagnetic pulse can improve the intensity of stress wave which will enhance the nonlinear response amplitude. A new type of early fatigue damage evaluation under high-energy nonlinear electromagnetic ultrasonic testing method is proposed in this project, which aims to improve the key nondestructive evaluation index of fatigue damage, such as the detection precision, reliability and repeatability.

早期疲劳损伤的准确无损评估，是高强度金属结构寿命预测和失效分析的关键，对提高设备的质量和可靠性具有重要意义。非线性超声方法在微损伤检测方面具有巨大潜力，针对其存在的载荷、缺陷与响应对应关系不明晰和压电非线性超声的耦合剂非线性干扰问题，本课题提出基于材料磁特性建立用于疲劳损伤检测的多场耦合分析模型，并采用高能脉冲激励的非线性电磁超声方法解决耦合剂引起的额外非线性问题。本课题建立包含磁特性/磁致伸缩特性和电/磁/力多物理场耦合等要素的疲劳损伤分析模型，研究疲劳损伤在载荷作用前后的非线性动态变化规律，揭示载荷、缺陷和检测信号之间的对应关系；通过高能电磁脉冲驱动电磁超声换能器，可有效提高应力波能量，增强超声非线性效应，解决低信噪比造成无法有效提取非线性信号的问题，并最终给出一种新型的早期疲劳损伤高能非线性电磁超声定量检测方法，以期提高疲劳损伤的检测精度、检测可信度、检测重复性等关键的无损评估指标。

早期疲劳损伤的准确无损评估，是高强度金属结构寿命预测和失效分析的关键。针对早期疲劳损伤的定性分析不准确、定量分析困难和压电超声的耦合剂非线性干扰问题，项目将高能电磁激励和非线性超声技术相结合，研究高能电磁激励、疲劳损伤与非线性信号的对应关系。首先，分析了疲劳裂纹的动态响应特性，建立了金属疲劳裂纹电磁-应力-应变非线性耦合模型，实现了对疲劳裂纹的定量检测。第二，设计了一种新型无静态偏置磁场的高能超声激励系统，研究了高能脉冲电磁超声换能器在换能过程中其磁场、力场、声场的变化规律，高能脉冲激励电源可以显著提高超声波信号。第三，研究了电磁超声换能器的换能机制与外加磁场、材料的磁化特性和磁致伸缩特性的关系。通过引入不同磁导率和电导率等效模拟塑性变形试件，得到了不同塑性损伤试件与相对磁导率变化的对应关系。第四，研究了应力应变、塑性损伤、超声非线性系数三者之间的关系，并利用非线性电磁超声方法对拉伸变形的试件进行塑性损伤评估。本项目为金属早期疲劳损伤的检测奠定了新的理论基础，该研究成果应用于高端装备制造、航空航天等国家重大战略领域中，为研究重大金属装备和设施的可靠性评估与寿命预测提供了理论依据。结合该项目的研究，培养博士、硕士研究生15名，其中已经毕业硕士13名；发表论文22篇，其中SCI收录6篇，EI收录16篇；授权发明专利2项，授权实用新型专利6项。