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.
