REU Supplement: Sensors: Measurement of Dynamic Weld Pool Surface

Welding is a widely used means for the assembly of final products of metals and the US can not afford to give up its leadership in cutting-edge welding technologies. However, this labor intensive operation requires skills. In addition, it is a very complex process which can only be depicted through numerical model based analysis. Weld pool is the center where complex phenomena occurring and the measurement of its dynamic surface is an unresolved fundamental issue which affects the validation/improvement of numerical models and the development of the next generation intelligent welding machines which emulate skilled operators. This project aims at the measurement of dynamic weld pool surface via developing an innovative sensor. There are four major difficulties associated with the measurement of weld pool surface: the arc is very bright; the weld pool surface is specular; the weld pool is very dynamic and changes very rapidly; and the sensor must function in and suitable for the particular environment of welding which is known as harsh. Although the measurement of weld pool surface is important, a literature survey shows that limited work has been done in this area. Innovative ideas are needed to construct effective solutions. Intellectual Merit: The proposed weld pool surface sensor are based on three innovative but relatively simple ideas: (1) Using the difference between illumination laser and arc in their propagation natures to clearly image the reflected laser rays in the presence of bright arc and to change "being specular surface" from "being a difficulty" to "being an advantage"; (2) Using an adjustable lens shape to optically determine the reflected rays quickly and using a liquid lens to implement the needed adjustment of lens shape; (3) Separating the sensor control electronics from the image sensor chip for sensor miniaturization which is needed for welding applications. These innovative ideas were developed from the PI's persistent learning, creative thinking, and experimenting for resolving the challenging issues. The completion of the proposed tasks requires using knowledge of optics, laser, arc, weld pool, imaging devices, image processing/computer vision, etc. to conduct exploratory research. Broader Impact: Welding is the final stage of manufacturing and US can not afford to give up its leadership in this field. Unfortunately, production of quality welds requires good understanding of the process and its operation requires high skills. The completion of this proposed research will significantly help better understand the process and provide foundations for the development of next generation, intelligent welding machines. The multi-disciplinary research and collaborative activities will provide good opportunities for training the participating postdoctoral scholar and PhD student toward academic researchers and educators. The participation of undergraduate students will help them gain opportunities to lead the change of manufacturing industry from being "low-tech" to a high-tech industry. Also, the participating high school senior would learn the beautiful and challenging part of engineering research so that he/she can be attracted to engineering filed. Of course, the proposed research would also provide excellent materials for senior design projects.