基于非线性超声导波混频的结构塑性损伤定位及表征方法

The engineering components will probably undergo plastic deformations, such as fatigue, creep or ratchet damages at a condition of high-temperature and high pressure in the service process. Quantitative evaluation and localization of early plastic damage of components would be a tough problem and has become a research hotspot in engineering fields. The current project aims to study the nonlinear mixing effect of ultrasonic guided waves (one kind effect of acoustic nonlinearity) and develop a new nondestructive evaluation method for localizing and assessing the plasticity induced micro-damages in in-service components. First, the generation conditions of nonlinear guided wave mixing can be determined by a theoretical analysis based on model expansion method. Then, the finite element method (FEM) simulation is carried out to investigate the generation effect of nonlinear mixing wave propagation in materials, whose results can be used as a comparison with experimental measurements. Next, experimental measurements of signals of nonlinear guided wave mixing are performed in plastically damaged materials. The localization of plastic micro-damages can be achieved by nonlinear wave mixing signals through altering the time delay of signal excitation. Finally, based on phenomenological research, an evaluation method relating to plastic damage-nonlinear wave mixing signal-residual life of component could be established by analytical computations, FEM simulations and experimental measurements. The researches of this project would provide a potential new ultrasonic testing technology for localization and evaluation of plastic micro-damages in materials by the nonlinear guided wave mixing method.

工程构件在服役过程中由于高温、高压等高参数运行工况的作用，极易发生疲劳、蠕变、棘轮等塑性变形现象。精确定量构件早期损伤和剩余寿命成为本领域研究的热点和难点。本项目拟开展非线性超声导波混频的研究（一种非线性效应），发展用于构件服役塑性微损伤的定位及表征的新方法。本项目拟采用导波模式展开分析方法，从理论上研究非线性导波混频信号的发生效应及激发条件；再根据理论条件开展材料中非线性导波混频波动传播的有限元仿真，研究不同导波模式发生非线性声波混频的效率，为塑性损伤结构中的超声导波实验测量提供对比研究；开展结构塑性损伤的非线性导波混频信号的实验测量，通过改变激发信号的延时，实现损伤后不同位置的非线性导波混频信号的定位表征；最后利用有限元仿真计算和实验测量，基于唯象方法构建结构塑性损伤-超声混频信号-服役寿命相关的评价方法。本项目的研究将建立结构服役塑性微损伤定位及表征的超声检测与评价新的方法。

对于在高温、高压和重载等极端条件下服役的关键设备核心构件，随着构件材料的微观组织演化往往会产生塑性损伤。为避免塑性损伤积累引起的结构突然断裂失效，本项目提出基于非线性超声导波混频的结构塑性损伤定位及表征方法。围绕非线性超声导波混频信号的发生效应理论、波动过程仿真、结构塑性损伤的超声导波混频信号的实验测量，构建了结构塑性损伤（微观组织演化）-超声混频信号-结构服役寿命三者相关的评价方法。.（1）采用二阶微扰理论及正交模式展开方法，理论研究非线性超声导波混频信号发生效应及激发条件，通过对各种混频方式进行相位匹配和矢量分析，得到具有累积效应的差（和）频信号产生条件，实现快速有效地筛选出满足条件的模式对。.（2）构建了非线性超声导波在结构中的波动传播模型，研究不同导波模式发生非线性声波混频的效率，以及激发频率、基波周期数和激发导波模式等物理参数对混频效率的影响，优化非线性超声导波混频模式。 .（3）基于非线性超声共振条件和优化导波模式对，对局部塑性损伤铝合金试样进行非线性兰姆波实验测量研究，通过改变激发信号的延时，实现结构局部塑性损伤的非线性导波混频信号的测量及定位表征。.（4）通过实验获得非线性参量值与材料塑性损伤之间的关系曲线，利用该曲线作为损伤试样的定标曲线，构建了一种利用非线性超声混频定量无损评价材料剩余寿命的方法。