Assessing Microstructural Damage Using Nonlinear Ultrasonics and Multiscale Numerical Modeling

超声波检测使用高频声波来确定材料的状态，而不会侵入。该技术可应用于缺陷检测、疲劳引起的小裂纹、材料表征和其他应用。非线性超声波检测不同于线性超声波检测，它考虑了大振幅的声波，因此它具有检测时效钢中微观组织变化的能力。非线性超声检测中的可测特性受各种类型和分布的微结构缺陷和裂纹的影响。该奖项支持基础研究，以了解超声波特性和微观结构损伤之间的相关性。该研究将通过结合数值模拟和实验测量，开发一种使用超声波检测钢中损伤的范例。该研究可应用于老化的民用基础设施，如桁架桥，管道，核电站等的结构健康检查，早期发现损坏和随后的维修可以延长结构的寿命。这项研究的成果将有益于美国的经济和社会。这项研究涉及计算力学、传感和监测以及材料科学等学科。非线性超声检测是通过测量高次谐波来检测微结构的变化，然而，从高次谐波中提取的非线性系数受损伤分布的不均匀性和损伤类型的影响。虽然它们可以使用实验方法进行评估，但在现场进行非线性超声检测时，实际上不可能考虑损伤分布和类型中的所有变量。本研究旨在利用多尺度数值模拟与实验相结合的方法，预测钢合金中由于非均匀损伤分布而引起的超声波的变化。包含材料异质性和微观结构的微观模型将从显微照片中创建，以获得受损材料的非线性特性，然后将其用于宏观模型中以评估损伤。多尺度框架将允许对材料中的微观结构变化及其对组件行为的影响进行建模。超声信号的变化将被量化，并与通过使用其他无损评估技术的机械测试和微观结构分析表征的机械性能变化进行比较。

Ultrasonic testing uses high frequency sound waves to determine the state of materials without intrusion. The technique can be applied to flaw detection, small cracks due to fatigue, material characterization, and other applications. Nonlinear ultrasonic testing differs from its linear counterpart on the consideration of large amplitude of sound wave; therefore it has capabilities of detecting microstructural variations in aged steel. The measurable characteristics in nonlinear ultrasonic testing are influenced by various types and distribution of microstructural defects and cracks. This award supports fundamental research to understand the correlation between ultrasonic wave characteristics and microstructural damage. The research will develop a paradigm to detect damage in steel using ultrasonic waves by combining numerical modeling and experimental measurements. The research can be applied to structural health inspection of aging civil infrastructure such as truss bridges, pipelines, nuclear power plants, etc. Early detection of damage and subsequent repairs can extend life of structures. The results of this research will benefit the U.S. economy and society. This research involves disciplines of computational mechanics, sensing and monitoring, and material science. The interdisciplinary approach will impact the education in the Science, Technology, Engineering, and Math disciplines.Nonlinear ultrasonic testing detects microstructural variations through measuring high order harmonics; however, the nonlinear coefficient extracted from high order harmonics is influenced by the heterogeneous damage distribution and the various damage types. Although they can be assessed using experimental methods, it is practically infeasible to consider all variables in damage distribution and types when conducting nonlinear ultrasonic testing in situ. The research is to predict changes in the ultrasonic waves due to heterogeneous damage distribution in steel alloys using multi-scale numerical modeling and experiments. The micro-scale model containing material heterogeneity and microstructure will be created from micrographs to obtain nonlinear properties of damaged materials, which will then be utilized in macro scale models to assess damage. The multi-scale framework will allow modeling microstructural changes in the material and their effects on the behavior of the component. The changes in ultrasonic signal will be quantified and compared with changes in mechanical properties characterized via mechanical testing and microstructural analysis using other nondestructive evaluation techniques.