金属圆管早期损伤的非线性周向超声导波评价方法研究

In order to ensure safety of metal circular tubes that have been widely used in practical engineering fields, it is necessary to carry out quantitative nondestructive evaluation for early damage in metal circular tubes. The present project aims to investigate a new nondestructive evaluation technique for quantitatively evaluating the early damage in metal circular tubes using nonlinear Circumferential Ultrasonic Guided Waves (abbr. CUGW). Firstly, we will establish a theoretical model to analyze the nonlinear effect of primary CUGW propagation, reveal the physical process on propagation of second harmonics generated, and develop a theoretical modal that describes the relationship between the effect of cumulative second-harmonic generation of primary CUGW propagation and the state of early damage in metal tubes. Secondly, we will select and optimize some appropriate mode pairs of primary and double-frequency CUGW modes to ensure larger efficiency of second-harmonic generation and higher sensitivity of second harmonic to early damage. Thirdly, a Finite Element Method (FEM) simulation model of the effect of second-harmonic generation by primary CUGW propagation will be constructed. By introducing the relevant parameters of the experimental specimen into the FEM simulation model, the features of nonlinear CUGW propagation in various damaged specimens will be numerically investigated. Finally, with the ultrasonic measurements and microstructural imaging observations on specimens with different states of damage in circular tubes, the correspondence relationship among “acoustic nonlinearity parameter β of CUGW - microstructural image - state of early damage in metal tubes” will be presented. Based on the abovementioned correspondence relationship, a technique for quantitatively evaluating early damage in metal circular tubes can be established. There is no doubt that the results obtained in this project will promote and facilitate the further developments and applications of nonlinear ultrasonic nondestructive evaluation technique.

对金属圆管早期损伤开展定量无损评价对于确保其使用安全十分必要。本项目拟就金属圆管早期损伤的非线性周向超声导波评价方法开展研究。首先通过对非线性周向超声导波的理论研究，揭示周向超声导波积累二次谐波发生与传播的物理过程，建立周向超声导波积累二次谐波发生效应与管材损伤状态相互作用的理论模型；理论探讨如何选择适当的基频和二倍频周向导波的模式对，以获得较大的二次谐波发生效率和较高的二次谐波对金属圆管早期损伤的响应灵敏度；构建非线性周向超声导波传播的有限元仿真模型，数值分析非线性周向超声导波在不同损伤程度圆管中的传播特性；就不同早期损伤状态的圆管试样进行超声测量和微观组织图像观察，以构建“周向超声导波非线性声参量β-微观组织图像-金属圆管损伤状态”三者之间的对应关系，基于该对应关系建立一种定量评价金属圆管早期损伤的非线性周向超声导波方法。项目成果将进一步促进和推动非线性超声无损评价技术的应用和发展。

周向超声导波作为在金属圆管结构中传播的一类重要导波模式，对其非线性效应开展系统的理论、仿真和实验研究，探索一种准确有效的金属圆管早期损伤无损评价方法具有重要的实际工程意义。在国家自然科学基金的大力支持下，项目对金属圆管早期损伤的非线性周向超声导波评价方法开展了系统的理论、仿真及实验研究。构建了金属圆管中周向超声导波二次谐波发生效应的理论分析模型，给出了周向超声导波二次谐波声场之解析解；揭示周向超声导波积累二次谐波发生与传播的物理过程；厘清了金属圆管材料弹性常数（二阶和三阶弹性常数）的改变对周向超声导波二次谐波发生效应所产生的影响。展示了如何选择适当的基频和二倍频周向导波的模式对，以获得较大的二次谐波发生效率和较高的二次谐波对金属圆管早期损伤的响应灵敏度；构建了非线性周向超声导波传播的有限元仿真模型，验证了周向超声导波二次谐波所具有的空间积累增长效应，及周向超声导波的沿周向传播的空间周期性对其二次谐波信号测量所起的增强作用，并分析了非线性周向超声导波对金属圆管损伤水平的响应特性。建立了周向超声导波二次谐波信号的实验测量系统，实验证明了采用非线性周向超声导波评价圆管早期损伤的可行性。在理论、仿真及实验研究基础上，建立一种定量评价金属圆管早期损伤的非线性周向超声导波方法。受项目资助，现已发表期刊论文9篇，其中有5篇被SCIE期刊收录，会议论文7篇，会议摘要3篇，授权实用新型专利1项，授权软件著作权4项。通过理论分析、数值仿真和实验相结合的方式，项目深刻揭示了金属圆管中周向超声导波二次谐波发生效应的物理过程及传播规律。项目成果对于促进非线性超声导波理论的进一步丰富和发展，以及奠定相关应用研究的理论与实验基础，具有重要的理论和实际意义。