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固体中带状裂缝对脉冲超声波散射的理论分析——普适解

SCATTERING OF AN ULTRASONIC PULSE BY A TWO-DIMENSIONAL CRACK IN SOLID——GENERAL THEORETICAL ANALYSIS

  • 摘要: 研究各种形状散射体,特别是具有尖锐稜边散射体的散射声场,是无损检测中关键性的基础工作。本文研究了固体内部具有自由表面的无限长带状裂缝对平面纵波或平面sv横波超声脉冲的散射,采用拉氏变换和广义Wiener-Hopf方法,给出了散射声场在拉氏域的表达式。当裂缝较宽时,本文给出了上述表达式的一种近似。这个近似式,可以采用Cagniard-de Hoop方法反演,而获得在时空域中的解析解。这个解在散射的初始阶段较准确地描述了散射近场的一些特性。我们曾用光弹方法,对玻璃内带状裂缝的散射进行了一些实验验证,实验情况将另文报道。

     

    Abstract: Scattering of elastic waves by obstacles of various shapes, especially those having sharp edges, is an important problem in NDE. The problem of scattering of a plane longitudinal or SV ultrasonic pulse in a solid, by a crack of finite width but very large length and with free faces is investigated in this paper by applying Laplace transforms and the generalized Wiener-Hopf technique, and a solution in the Laplace domain for the scattered field is obtained. For a wide crack, an approximate form of the solution is formulated, which can be inverted by the Cagniard-de Hoop method. The approximate solution in the time-space domain gives the major features of scattering in the early time and hence of the near field. We have also experimentally studied the corresponding scattered ultrasonic field in glass by the use of the photoelastic visualizing technique, but the results are not included here.

     

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