中文摘要：

由焊缝内部粗大柱状晶引起的声波衰减及散射噪声会给超声检测带来较大的困难。采用超声TOFD检测方法对奥氏体不锈钢焊缝进行检测;通过调整探头参数在焊缝中形成入射方向各异的检测声束,分析焊缝组织结构在各种声场条件下对缺陷衍射波幅度及信噪比的影响。结果显示：不锈钢焊缝中的超声波传播具有明显的各向异性特征,焊缝中不连续界面的取向与声束的夹角对检测波衰减及散射具有显著影响,优化声束入射方向能有效提高检测波信噪比;此外,建立了焊缝组织结构模型进一步解释了声波传播各向异性的形成机理,为优化检测参数提供了可靠的理论依据。

英文摘要：

Ultrasonic testing is difficult to be implemented well because of the acoustic noise and attenuation resulted by the big column grain in the weld.In the paper,ultrasonic TOFD method is adopted to inspect the defects in austenitic stainless steel weld.Ultrasonic beam with different incident angle is formed in the weld through adjusting experimental parameters,and then the influence of weld structures on amplitude of diffraction waves and signal-to-noise ratio is analyzed to reveal the ultrasonic propagation in the weld.The results indicate that the wave propagation in the weld shows obvious anisotropy characteristics,and the included angle of the ultrasonic beam and discontinuous boundary in weld have a significant impact on the wave attenuation and scattering,so optimizing the beam direction is liable to enhance noise-signal ratio and testing effect.Moreover,the mechanism of anisotropy is presented by constructing weld modal,which gives reliable theory evidence for optimizing testing parameters.