Multi-Dimensional Stress Quantification at Complex Loaded Structural Components with Nonlinear Rayleigh Waves

本研究的目的是开发一种新的无损检测程序的建设结构部件。该项目将量化包括残余应力在内的受载结构元件的多方向应力状态。所提出的方法使用非线性瑞利波评估在正常和剪切方向的应力状态。假设声弹性描述了应力和超声波之间的关系。这种方法将通过使用瑞利波来量化三个应力分量。这些波与剪切应力相互作用，并允许三个角度的超声测量，以解决三个未知的应力值同时进行。研究涉及瑞利波传播的解析公式;数值模拟将与实验室实验进行验证。这种方法具有潜在的适用性的各种结构部件的桥梁，核电站和other.The穿透深度的瑞利波取决于扰动频率。该特性将用于量化法向应力和剪切应力分量。将研究一系列激励频率以了解剪切应力对超声波的影响，并量化三个方向的非线性系数。对非线性超声的基本方程进行修正，加入剪切应力项，并通过实验对修正后的方程进行验证。本项目测试的测量方法包括具有耦合校正的压电接收器-发射器、电磁换能器系统和压电耦合激光感应超声波。应力水平分辨率的目标值为10 MPa，置信度为90%。

The goal of this research is to develop a new procedure for nondestructive testing of built structural components. The project will quantify the multi-directional state of stress of loaded structural elements including residual stresses. The proposed approach uses nonlinear Rayleigh Waves for assessing the state of stress in normal and shear directions. The hypothesis is that acoustoelasticity describes the relationship between stress and ultrasonic waves. This approach will quantify three stress components through use of Rayleigh Waves. These waves interact with shear stress and permit three angled ultrasonic measurements to solve three unknown stress values simultaneously. The research involves analytical formulations of propagation of Rayleigh Waves; the numerical simulation will be validated with laboratory experiments. This approach has the potential of applicability to a variety of structural components of bridges, nuclear power plants and others.The penetration depth of the Rayleigh wave depends on the perturbation frequency. This property will be utilized to quantify the normal and shear stress components. A range of excitation frequencies will be studied to understand the influence of shear stress on the ultrasonic waves, and quantify the nonlinearity coefficients for three directions. The basic equations of nonlinear ultrasonic will be modified to include the shear stress term; the resultant equations will be verified with the laboratory experiments. The measurement approaches to be tested in this project include piezoelectric receiver-transmitter with the coupling correction, electromagnetic transducer system and piezoelectric coupled-laser induced ultrasonic waves. The stress level resolution is targeted at 10 MPa with 90 percent confidence level.