表面不平度对近表面缺陷的超声检测的影响

激光焊接是连接钛合金的一种主要的工艺方法.由于焊缝中气孔形成倾向较大,需要进行严格的无损检测.文中概述了超声自动检测过程中工件表面不平度的不利影响,重点分析了焊缝余高对检测结果的影响.采用不同频率的探头对模拟试件进行超声水浸检测,通过对焊缝的不同位置进行测试得到适用的探头频率及其它检测参数.结果表明,通过选择合适的探头频率和检测工艺,可以减小表面不平度对检测灵敏度的影响,可以发现工件表面以下深度为1.0～2.5 mm、最小直径为0.3 mm的气孔缺陷,从而提高超声自动检测的可靠性.

Effects of uneven surface on ultrasonic testing results of defects close to surface

Laser welding is an important method to join titanium alloy.The rigorous nondestructive test is necessary because pores are eaeily formed in the laser welding.The bad effects of uneven weld surface on the automatic ultrasonic inspection were summarized.The simulated practical sample was inspected through immersed ultrasonic testing technique at different point with different frequency probe.The defects images of weld were constructed using reasonable testing parameters and probe.The defect,which was located in 1.0-2.5 mm below the surface and whose diameter was bigger than 0.3 mm,can be detected,when the testing process was used to detect the T-shape Ti alloy laser welded joint.The experimental results show that a right frequency of probe can reduce the bad influence of uneven surface,which improves the reliability of ultrasonic test effectively.