用离散点源方法模拟分层介质中超声波场

发布时间：2019-06-14 04:06

【摘要】：在无损检测领域中,超声场的模拟是非常重要的内容,离散点源方法是众多模拟方法中的一种。此方法与有限元和有限差分方法不同,它不需要将整个空间离散化,仅需要将换能器表面和界面离散化,因此可提高计算声场的速度,是一种很有潜力的半解析仿真技术。近些年,离散点源方法发展迅速,国外已将这种技术作为一种新的无损评估方法,广泛应用于二维和三维几何问题中。这种方法可以模拟磁场、超声场、电场以及电磁场等问题,具有重要的理论研究价值,在实际工程的应用方面也有重要的指导意义。本文从离散点源方法的基本原理出发,通过引用格林函数方程,利用声源表面和界面上的边界条件建立线性方程组,求解各点源强度矢量,进而得到整个模型中的声场。本文独立编写程序,模拟了流体—流体介质的声压场、流体—固体介质中的声压场、流体—固体—流体介质的声压场。模拟结果表明,分层介质中的超声场图像与Kundu教授2007年所发表的分层介质超声场的研究成果具有良好的一致性。文中同时考察了点源密度对空间声压场的影响,得出当点源半径小于?50/时,声压场的模拟趋近稳定,接近理论值。这些工作为日后模拟破损固体的超声场提供了对比依据,也为模拟多层介质的声压场提供了理论基础。
[Abstract]:In the field of nondestructive testing, ultrasonic field simulation is a very important content, and discrete point source method is one of many simulation methods. Different from finite element method and finite difference method, this method does not need to discretize the whole space, but only needs to discretize the surface and interface of transducer, so it can improve the speed of calculating sound field and is a potential semi-analytical simulation technology. In recent years, discrete point source method has developed rapidly. As a new nondestructive assessment method, this technique has been widely used in two-dimensional and three-dimensional geometric problems abroad. This method can simulate magnetic field, ultrasonic field, electric field and electromagnetic field, and has important theoretical research value and important guiding significance in practical engineering application. In this paper, based on the basic principle of discrete point source method, the linear equations are established by using Green's function equation and the boundary conditions on the surface and interface of sound source, and the intensity vector of each point source is solved, and then the sound field in the whole model is obtained. In this paper, the sound pressure field of fluid-fluid medium, the sound pressure field of fluid-solid medium and the sound pressure field of fluid-solid medium are simulated independently. The simulation results show that the ultrasonic field images in layered media are in good agreement with the research results of ultrasonic field in layered media published by Professor Kundu in 2007. At the same time, the influence of point source density on the spatial sound pressure field is investigated, and it is concluded that when the radius of the point source is less than 50 /, the simulation of the sound pressure field is close to the theoretical value. These work provide a comparative basis for simulating the ultrasonic field of damaged solids in the future, and also provide a theoretical basis for simulating the sound pressure field of multilayered media.
【学位授予单位】：吉林大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TB55

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