材料损伤与微裂纹的非线性超声检测技术研究

The precision of traditional ultrasonic testing can't satisfy the requirements due to material or in service structural components with microcrack and fatigue damage, therefore, a new way to ultrasonic testing has been explored. Nonlinear ultrasonic nondestructive testing technology is expected to be a good means to detect above defects . At present, the nonlinear ultrasonic testing technology hasn't got general recognition for most nondestructive testing personnel because of its characteristic mechanism insufficient investigation (namely the formation mechanism of high frequency harmonic). This project uses the method to combining the dynamic finite element simulation with nonlinear sound waves experiment and the destructive experiment with non-destructive test in order to build the relationship between crack structure features and nonlinear ultrasonic parameter 1, the relationship between material fatigue damage and nonlinear ultrasonic parameter 2 respectively by analyzing mixed wave that comes from the low frequency pump wave and the fundamental wave on the basis of analyzing characteristics of ultrasonic propagation in the material with the microcrack and generate mechanism of high frequency harmonic deeply. it is illustrated that non-linear acoustic response for crack structure features. it can realize the nondestructive characterized for material with degradation of mechanical properties. It provides the technical support to our country that the nondestructive testing evaluation with independent intellectual property rights for the preparation of materials and structural components with initial cracking damage.

当材料或在役结构件存在疲劳损伤和微裂纹时，传统超声技术的检测精度就无法满足要求，促使人们探索新的超声检测途径。非线性超声无损检测技术有望成为检测上述缺陷的良好手段。由于对超声非线性特性的机理（即高频谐波的产生）了解得还不是十分透彻，使得非线性超声检测技术尚未得到普遍应用。本项目从材料裂化损伤特性和非线性超声机理两方面着手，运用动态有限元模拟和非线性声波实验相结合、有损实验和无损实验相结合的方法，通过对由低频泵波与基波产生的混合波的非线性特征参量提取，在深入分析超声在含有裂纹及损伤介质中的传播特性和高频谐波产生机理的基础上，分别阐明"裂纹结构特征-非线性响应特征参量1"、"疲劳损伤程度-非线性响应特征参量2"之间的内在关联。揭示微裂纹结构参量的非线性声学响应现象，实现对材料力学性能退化的无损表征。为材料制备及结构元件的初期裂化损伤的无损检测评价提供具有我国自主知识产权的技术支撑。

本项目基于非线性声学和材料学理论，建立了声波在含有损伤缺陷介质中传播时产生的非线性数学模型。从数值模拟和实验分析两方面入手，分析了缺陷引起的波形畸变、产生高频谐波的机理及不同损伤程度所产生的高频谐波参量变化规律。阐明了"损伤特征-非线性响应特征参量之间的内在关联。揭示了微裂纹结构参量的非线性声学响应现象，实现了对材料损伤性能的无损表征。主要研究结果如下：.首先，基于非线性超声波理论，借助泵波理论，建立了超声波非线性检测物理模型。利用小波变换法给出了非线性系数的求解方法。然后，通过求解非线性超声检测模型，计算出超声波在橡胶涂层和等离子涂层中传播产生的非线性系数。建立了非线性系数与涂层孔隙率之间的关系，以及非线性系数与界面结合强度之间的关系。其次，针对内孔直径为45mm，高度为150mm的薄壁圆柱壳试样。设计了一套基于非线性系数表征涂层界面的超声波C扫描系统，该系统由串行通讯接口模块、步进电机驱动模块，步进电机的控制模块和机械扫描模块四部分组成，能检测试样内壁涂层界面的结合情况。最后，基于超声波非线性检测方法，研究不同厚度的圆柱壳内壁涂层界面微小缺陷的数量和位置。通过C扫描系统成像界面缺陷，验证了涂层损伤的程度。.该项目为材料制备及结构元件的初期裂化损伤的无损检测评价提供具有我国自主知识产权的技术支撑。已经发表和录用论文8篇，其中SCI 检索1篇；EI检索4篇；实用新型专利3项。