Restricted Scope for REU Supplement: Control of Metal Transfer at Given Arc Variables

In the laser-enhanced gas metal arc welding (GMAW), the droplet is primarily detached by the gravitational force of the droplet that is determined by the desired mass of the droplet, the recoil pressure from the applied laser that increases with the laser power, and the electromagnetic force that increases with the welding current. Detaching the droplet at a desired mass (controlling this metal transfer variable at a desired value) requires the sum of the laser recoil force and detaching electromagnetic force to be sufficient. A reduction in the current requires an increase in the laser power in order to still detach the droplet at the desired mass. However, an increased laser power implies an increased cost. The PI proposes to use the momentum of an oscillating droplet to reduce the needed power from the laser when the desired peak current and droplet mass are given. To optimally control the oscillation, the PI proposes a combined experimental-theoretical method to model the oscillation. The proposed research will be undertaken by two undergraduate students with the assistance from a PhD student and the PI. Intellectual Properties: The undergraduate students will (1) conduct experiments to identify major parameters that affect the effectiveness of the oscillation, (2) conduct experiments using designed major parameters, (3) record the welding process/metal transfer process using a high speed camera and synchronize the recorded images with the current and voltage waveforms, (4) analyze recorded images, (5) propose and test image algorithms to extract/measure the droplet formation and detachment from the recorded images, (6) study the correlation of the droplet measurements from the image processing with the major parameters, (7) model this correlation mathematically from experimental data, (8) model this correlation based on first principles with appropriate simplifications, (9) compare the experimental mathematic model with the first-principle theoretical model to check if the assumptions for theoretical derivations are reasonable and need to be modified, (10) finalize the model from the first-principle theoretical model by incorporating experimentally verified assumptions and finally fit the model parameters from experimental data. These tasks are challenging and the completion will help optimally control the oscillation to maximize its effectiveness in reducing the laser power. Broader Impact: The participating undergraduate students will gain research experience on analysis of experimental phenomena, high speed image processing, and modeling of complex process using a combined experimental-theoretical method. Such research experience will help the two participating outstanding undergraduate students from under-represented groups to compete for challenging R&D positions.