Measuring on-line and off-line noncontact ultrasound time of flight weld penetration depth
Measuring on-line and off-line noncontact ultrasound time of flight weld penetration depth
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作者：
A. Kita;I. Ume
焊接是用于连接结构部件的主要技术。然而，焊缝熔深测量不是实时进行的，导致其开环控制。在线焊缝熔深测量的主要障碍是缺乏精确的和高分辨率的无损和非接触式传感器，可以在高温和恶劣的环境中典型的焊接工艺。使用超声波传感器来测量对接接头焊缝的焊透深度集中于使用来自焊道底部的纵波或横波的直接反射。在激光产生超声期间，观察到在焊接样品的底部上产生瑞利（表面）波。这种瑞利波传播到焊道的底部，在那里它模式转换成纵向（压力）和剪切（横向）波。模式转换的纵波行进到焊接样品的底部，在那里它产生剪切（RGLS）和纵向（ROLL）波反射。类似地，模式转换横波也产生横波（RGSS）和纵波（RGSL）反射。将介绍一种新的RGLS飞行时间（TOF）技术用于焊缝熔深测量的发展。使用RGLS TOF技术测量焊缝熔深的实验结果已被证明是准确的，精确的，和可重复的离线焊接后和在线焊接过程中。还将介绍与RGLS TOF技术相关的其他RGLL、RGSL和RGSS TOF技术。这种用于测量焊缝熔深的新技术可以实现焊缝熔深的闭环控制。
Welding is the primary technique used for joining structural components. However, weld penetration depth measurement is not done in real-time resulting in open-loop control of it. The major obstacle to on-line weld penetration depth measurement is a lack of accurate and high-resolution nondestructive and noncontact sensors that can operate in high temperatures and harsh environments typical of welding processes. The use of ultrasonic sensors to measure weld penetration depth of butt joint welds has focused on using a direct reflection of either a longitudinal or shear wave from the bottom of a weld bead. During laser generation of ultrasound, it was observed that a Rayleigh (surface) wave was generated on the bottom of weld samples. This Rayleigh wave traveled to the bottom of the weld bead where it mode converted into a longitudinal (pressure) and shear (transverse) wave. The mode-converted longitudinal wave traveled to the bottom of the weld sample where it generated a shear (RGLS) and longitudinal (ROLL) wave reflection. Similarly, the mode converted shear wave also generated a shear (RGSS) and longitudinal (RGSL) wave reflection. The development of a new RGLS time of flight (TOF) technique for weld penetration measurements will be presented. Experimental results using the RGLS TOF technique for weld penetration depth measurement has proven to be accurate, precise, and repeatable both off-line after welding and on-line during welding. Additional RGLL, RGSL, and RGSS TOF techniques related to the RGLS TOF technique will also be presented. This new technique for measuring weld penetration depth can enable closed loop control of weld penetration depth.