奥氏体不锈钢焊缝超声TOFD检测中声波传播特性分析及其应用

Application and analysis on wave propagation in ultrasonic TOFD test of austenitic stainless steel weld

由焊缝组织引起的声波衰减及散射严重影响奥氏体不锈钢焊缝的超声TOFD检测效果,这在无损检测方面是亟待解决的难题.文中分析焊缝中各角度检测声束形成的缺陷衍射波幅度及检测信号信噪比特征,揭示声波传播特性的影响因素.结果表明,不锈钢焊缝中的超声波传播具有明显的各向异性特征,柱状晶生长方向与声束入射方向的夹角对检测波衰减及散射具有显著影响;文中结合金相结构图建立焊缝组织模型进一步解释了声波传播各向异性的形成机理;并以此为基础提出一次波检测方法和二次波检测方法,获得了较好的检测效果.

Ultrasonic TOFD testing of stainless steel weld is deeply influenced by the acoustic noise and attenuation produced by the weld structure,and which are the key problem needed be solved. Ultrasonic beams with different incident angle were formed,and the amplitude and noise-signal ratio of diffraction wave influenced by weld structure were analyzed to reveal the characteristics of ultrasonic propagation in the weld. The results indicate that the ultrasonic propagation in the weld show obvious anisotropy characteristics,and the incident angle of the ultrasonic beam and columnar crystal boundary in weld have a significant impact on the wave attenuation and scattering. Moreover,the mechanism of anisotropy was presented by constructing weld model,which gives reliable theory evidence for optimizing testing parameters in real testing. And then,there are two testingmethods include primary wave testing method and secondary wave testing method presented to achieve better testing results.