Sensors: Measurement of Dynamic Weld Pool Surface

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The objective of this Sensors and Sensor Networks (NSF 05-526) research project is to develop an innovative sensor which can measure a highly dynamic weld pool surface despite the pool's specular nature and the presence of bright plasma. The approach will be to make use of three relatively simple ideas: (1) exploit the difference between propagation in illumination laser and plasma to clearly image laser rays mirrored from the weld pool surface in the presence of bright plasma, thus changing the specular surface from a difficulty to an advantage; (2) use optical means to rapidly determine the reflected rays; (3) separate the sensor control electronics from the image sensor chip to enable sensor miniaturization, crucial for many welding applications.The pool is where complex welding phenomena originate so welding phenomena cannot be understood completely without pool surface data. The proposed sensor will improve the capability to observe, analyze and understand welding phenomena/processes. In addition, because welding phenomena are so complex, numerical models must be used; in fact, they have already played a significant role in depicting aspects of the welding process. Unfortunately, the unavailability of weld pool surface data makes the development of accurate numerical models difficult. By providing data for model validation, this project will help develop highly reliable and trustworthy numerical models. Lastly, measuring the pool surface can also provide the knowledge base from which to develop the next generation of intelligent welding machines to emulate and surpass the art of skilled welders who can control weld penetration by observing the weld pool surface. In terms of broader impact, the multi-disciplinary research and collaborative activities will provide good opportunities for training the participating post-doctoral scholar and PhD student as academic researchers and educators. The plans for undergraduate and high school senior participation, curriculum development, and special website establishment would further the impact of the project.