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首页> 外文学位 >PHYSICAL PRINCIPLES UNDERLYING ULTRASONIC NONDESTRUCTIVE EVALUATION OF ANISOTROPIC MEDIA (ULTRASOUND, COMPOSITES, GRAPHITE-EPOXY, BACKSCATTER, ATTENUATION).
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PHYSICAL PRINCIPLES UNDERLYING ULTRASONIC NONDESTRUCTIVE EVALUATION OF ANISOTROPIC MEDIA (ULTRASOUND, COMPOSITES, GRAPHITE-EPOXY, BACKSCATTER, ATTENUATION).

机译：各向异性介质（超声，复合材料，石墨-环氧树脂，背散射，衰减）的超声非破坏性评估的物理原理。

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摘要

The research described in this thesis is aimed toward extending the physics underlying the application of ultrasound to the investigation of materials. Some of the results presented deal with isotropic materials, both homogeneous and inhomogeneous. However, the primary focus is the physics of inhomogeneous, anisotropic materials, such as fiber-reinforced plastics.;In this thesis, we describe the physics underlying the use of ultrasound as a tool for the detection and characterization of damage in composite materials. The thesis is composed of two inter-related portions. The first portion serves as an introduction to wave propagation in isotropic and anisotropic media. These chapters provide a basis of insight and intuition for the non-destructive evaluation experiments described in the second portion.;The second portion deals with experimental application of ultrasonic techniques to several specific problems in nondestructive evaluation. The studies reported here examine parameters of ultrasonic propagation in materials with known flaws whose location and character have been verified by independent (non-ultrasonic) means. The ultrasonic parameters employed in these studies are backscatter, attenuation measured in transmission, and attenuation estimated from backscatter. Three chapters deal with the use of a backscatter-based technique known as polar backscatter. In this technique the effects of specular reflection from the water/sample interface in an immersion-type measurement are reduced by interrogating at nonperpendicular incidence. The anisotropic nature of composite laminates makes polar backscatter a very useful tool for investigation of impact damage and porosity. Two chapters discuss a theoretical approach and experimental results for estimating attenuation in inhomogeneous materials from backscattered ultrasound.;Fiber-reinforced plastics exhibit very favorable strength-to-weight ratios and can be fabricated to exhibit a wide range of structural properties. From a mechanical standpoint, two types of disadvantages of otherwise well-designed composite materials are fabrication defects (e.g., delamination, fiber-misalignment, and porosity) and wear damage (e.g., environmental degradation, fatigue stress, and impact damage).
机译：本文所描述的研究旨在将超声应用的基础物理学扩展到材料研究中。提出的一些结果涉及均质和非均质的各向同性材料。但是，主要的重点是非均质各向异性材料（例如纤维增强塑料）的物理学。在本论文中，我们描述了将超声波用作检测和表征复合材料中的损伤的工具的基础物理学。论文由两个相互关联的部分组成。第一部分介绍了波在各向同性和各向异性介质中的传播。这些章节为第二部分中描述的非破坏性评估实验提供了见识和直觉的基础。第二部分介绍了超声技术在无损评估中几个特定问题的实验应用。此处报道的研究检查了具有已知缺陷的材料中超声传播的参数，这些缺陷的位置和特征已通过独立（非超声）手段进行了验证。这些研究中使用的超声参数是反向散射，在传输中测量的衰减以及根据反向散射估算的衰减。三章介绍了基于反向散射的技术（称为极地反向散射）的使用。在该技术中，通过以非垂直入射方式进行询问，可以减少在水浸式测量中水/样品界面的镜面反射的影响。复合材料层压板的各向异性使极性反向散射成为研究冲击破坏和孔隙率的非常有用的工具。两章讨论了估算反向散射超声对不均匀材料的衰减的理论方法和实验结果。纤维增强塑料具有非常好的强度重量比，并且可以制造成具有广泛的结构特性。从机械的观点来看，否则设计得很好的复合材料的两种类型的缺点是制造缺陷（例如，分层，纤维错位和孔隙率）和磨损损坏（例如，环境退化，疲劳应力和冲击损坏）。

著录项

  • 作者

    BLODGETT, EARL DANIEL.;

  • 作者单位

    Washington University in St. Louis.;

  • 授予单位 Washington University in St. Louis.;
  • 学科 Acoustics.
  • 学位 Ph.D.
  • 年度 1986
  • 页码 229 p.
  • 总页数 229
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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