论文部分内容阅读
数字超声成象在医疗诊断和材料的无损检测中引起了重视。本文将详细研究与材料缺陷所引起的弹性动力波衍射有关的特殊的物理现象,并使之能用于数字方法的识别和成象。 弹性动力波的衍射现象,可根据Huygens原理,其物理量是缺陷表面的位移分布。辐射位移场可用辐射图形来描述。它既与频率有关,又与观察角度有关。这对描述缺陷的几何形状特别有用,并可用于识别和成象。 频率依赖关系的运用,需要激发和接收宽带超声脉冲。时域参数化法是缺陷识别和分类的基本方法,把缺陷分为裂缝或杂质。我们要阐述的是纵-纵波散射的普遍原理。
Digital ultrasound imaging has drawn much attention in medical diagnosis and non-destructive testing of materials. This article will study in detail the special physical phenomena associated with the elastic dynamic wave diffraction caused by material defects and make them useful for the identification and imaging of digital methods. The diffraction of elastic dynamic waves can be based on the Huygens principle and the physical quantity is the displacement distribution of the defect surface. The radiation displacement field can be described by the radiation pattern. It is both frequency-dependent and observation-related. This is particularly useful for describing the geometry of the defect and can be used for identification and imaging. The use of frequency dependence requires the excitation and reception of broadband ultrasound pulses. Time domain parameterization method is the basic method of defect identification and classification, the defects are divided into cracks or impurities. We are going to explain the general principle of longitudinal-longitudinal wave scattering.