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所研制的基于波型转换的超声单探头探伤法可检测垂直裂缝,与串联法相比,该 LLT 技术有着几乎相同的灵敏度,且在操作及适应范围方面具有手动和自动检测的优点。此外,这种 LLT 技术可改善探伤区的近场影响,降低对裂缝偏斜的依赖,减少对有包装的工件损伤。由于可利用镜面反射原理,进行适当的幅度计算,LLT 技术可用来检测象大型容器或涡轮机机身之类厚壁工件,或可用来检测象管子或薄板之类的薄壁工件。缺陷特性鉴定有所改进,而且还有可能作缺陷分类,即区分缺陷是裂纹、孔隙还是夹渣。最近导出了计算机有限裂缝(无限长的条带状反射器)处散射的精确理论模型,证明 LLT 技术对有限裂缝同样具有很高的灵敏度。根据上述精确的弹性力学理论,并计算探头楔板和待测表面之间反射波的传播,已设计出 LLT 技术所需的3个一组的超声换能器,并计算了它们的灵敏区。
The developed single wave probe based on wave conversion detects vertical cracks. Compared with the tandem method, this LLT technique has almost the same sensitivity and has the advantages of manual and automatic detection in terms of operation and adaptation. In addition, this LLT technology improves near-field effects in the test area, reduces reliance on crack deflection and reduces damage to packaged workpieces. With the specular reflection principle, proper amplitude calculations are possible and LLT technology can be used to inspect thick-walled parts such as large vessels or turbine bodies or to detect thin-walled parts such as pipes or sheets. Identification of defects has improved, but also possible to make a defect classification, that is, the distinction between defects is cracks, pores or slag. Recently an accurate theoretical model of scattering at a finite crack in a computer (infinite strip reflector) has been derived, demonstrating that the LLT technique is equally sensitive to finite fractures. Based on the above precise theory of elasticity and the calculation of the propagation of reflected waves between the probe wedge and the surface under test, a set of three ultrasound transducers required by the LLT technique has been devised and their sensitive zones calculated.