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Image processing-based techniques for process parameter characterization in Plasma Transferred Arc Additive Manufacturing (PTA-AM) process

  • Author / Creator
    Gajbhiye, Raviraj
  • The plasma transferred arc additive manufacturing (PTA-AM) process is a recently established additive manufacturing (AM) technique for manufacturing large parts for the resource industries. In the PTA-AM process, the build quality of the 3D part is governed by various processing parameters, including but not limited to plasma arc current, stand-off distance (SOD) and powder flow rate. The PTA-AM is challenging for in-process monitoring due to the complex interaction among the plasma arc, powder stream and substrate. Any instability in these processing parameters affects the overall build quality of the component, inducing non-conformance to geometrical properties. In the AM field, various high-speed imaging techniques are used to investigate the correlation between the processing parameter variation contributing to quality fluctuations of the final 3D product. This thesis presents the in-situ image processing methodologies to quantify and analyze the process aspects of the emergent PTA-AM system. Firstly, the single-track multi-layer bead deposition experiments of WC-reinforced NiCrBSi composites are carried out on a PTA-AM system and recorded with a high-speed camera. The optimized SOD has been determined from image analysis, contributing to the uniform deposition with quality deviation. The image analyzed SOD is validated with the experimentally determined SOD. This information is also used to evaluate the impact of powder variation on bead layer height. Secondly, the proposed in-situ image processing technique has been employed to describe the relationship between powder stream distribution and build geometry variation. In addition, the effect of plasma arc current on bead layer geometry (height and width) is also investigated. The Analysis of variance and t-tests has checked the significance of build quality dependence on powder and plasma arc variation. It is well-known that the powder flow behaviour (the particle trajectories and velocities) under the plasma arc region is a complex but crucial physical phenomenon that affects the geometric dimensions and the bead deposition characteristics in PTA-AM. Therefore, we proposed another image processing methodology to investigate the powder stream behaviour under the influence of the plasma arc region. In the findings, variation in trajectories and impact velocities of individual powder particles due to plasma arc has been observed. Using the single-particle trajectory model, we validated that the results are within the theoretical range. Later, based on calculated impact velocities of powder particles, the parametric study was conducted to predict the spreading and solidification of molten powder particles on the substrate. Using dimensionless numbers, the parametric effect of hydrodynamic forces (Weber and Reynolds number) and thermophysical forces (Stefan and Peclet number) on the impinging melted powder particles is also studied.

  • Subjects / Keywords
  • Graduation date
    Spring 2022
  • Type of Item
    Thesis
  • Degree
    Master of Science
  • DOI
    https://doi.org/10.7939/r3-wt8d-h857
  • License
    This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.