On-Line Monitoring of Weld Pool Depth with Laser Ultrasound

利用激光超声波在线监测熔池深度

• 批准号: 9622277
• 负责人: I. Charles Ume
• 金额: $ 19.38万
• 依托单位: Georgia Tech Research Corporation
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 1996
• 资助国家: 美国
• 起止时间: 1996-09-01 至 1999-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9622277&HistoricalAwards=false
• 关键词: Line; Monitoring; Weld; Pool; Depth

9622277 Ume Pulsed laser generation is a thermoelastic process when the laser energy is below the ablation level. The laser deposits heat on the surface causing a local expansion and contraction which in turn results in ultrasonic stress waves. This principle has been successfully demonstrated by the investigators to simulated welds using phased array laser in a prior NSF funded research. Phased array was the novelty in the prior work which allowed for control of beam width, direction and focusing and the directionality of the emanating ultrasonic waves as well as generation of one type of wave motion, such as the surface (Raleigh) wave, shear wave, or longitudinal wave. In the detection of molten weld pool this last feature can be taken advantage by using the distinguishing feature of liquid, which can not carry shear waves unlike solids. In the current research, the detection will be carried out by electromagnetic acoustic transducer. Weld pool depth during an actual gas metal arc welding process will be attempted by lining up the phased laser array and electromagnetic acoustic transducer behind the welding torch in a programmable automated welding system. In order to understand the process sufficiently to automate the on-line monitoring of welding, an analytical model will be developed for array sources and combined with published work on effects of ultrasound propagation through temperature gradients. Industrial researchers with expertise in welding have come forward with the donation of an automated welding equipment system as well as shown a commitment to provide on-site consulting. This kind of close working relationship between industrial researchers and academic faculty and students should be invaluable not only transferring the technology to the commercial sector but also in training the future engineers in a relevant customer pull manufacturing project. Current state of automation in welding is limited to open control by monitoring the weld quality as a post-processing step bec ause of the very aggressive environment (splattering of molten metals surrounded by hot gases) during the welding process. This research has the potential to make possible closed loop control whereby a very high quality of the weld could be achieved. Such a manufacturing process has far reaching consequences in the welding industry in terms product quality, rework reduction and thus lower process cost. Considering that welding is used extensively in a wide variety of manufacturing from ship building to construction, the impact on the national infrastructure could be enormous.

当激光能量低于烧蚀水平时，9622277微米脉冲激光的产生是一个热弹性过程。激光在表面沉积热量，引起局部膨胀和收缩，进而产生超声波应力波。这一原理已经被研究人员成功地演示到使用相控阵激光模拟焊接，这是在美国国家科学基金会先前资助的一项研究中。相控阵是前人工作中的创新，它允许控制波束宽度、方向和聚焦，以及发射的超声波的方向性，以及产生一种类型的波动，如表面(Raleigh)波、横波或纵波。在熔池检测中，利用液体不能像固体一样携带横波的特点，可以充分利用液体的这一特性。在目前的研究中，将采用电磁声换能器进行检测。在可编程自动焊接系统中，通过在焊枪后面排列相控激光阵列和电磁声传感器来尝试在实际的气体保护金属弧焊过程中焊接熔池深度。为了充分了解这一过程以实现焊接在线监测的自动化，将开发一个阵列源的分析模型，并将其与已发表的关于超声波通过温度梯度传播的影响的工作相结合。具有焊接专业知识的工业研究人员已经挺身而出，捐赠了一套自动化焊接设备系统，并承诺提供现场咨询。工业研究人员与学术教职员工和学生之间的这种密切合作关系应该是无价的，不仅可以将技术转移到商业部门，而且在相关的客户拉动制造项目中培养未来的工程师也是如此。由于焊接过程中非常恶劣的环境(被热气包围的熔融金属飞溅)，焊接自动化的当前状态仅限于通过监测焊接质量作为后处理步骤的开放式控制。这项研究有可能使闭环控制成为可能，从而实现非常高的焊接质量。这种制造工艺在产品质量、减少返工和降低工艺成本方面对焊接行业产生了深远的影响。考虑到焊接在从造船到建筑的各种制造业中广泛使用，对国家基础设施的影响可能是巨大的。