Date of Award

Fall 12-2020

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Mechanical & Aerospace Engineering

Program/Concentration

Mechanical and Aerospace Engineering

Committee Director

Abdelmageed Elmustafa

Committee Director

Hamid Eisazadeh

Committee Member

Sebastian Y. Bawab

Committee Member

Vukica Jovanovic

Abstract

Wire and Arc Additive Manufacturing (WAAM) is a cost-effective additive manufacturing process due to its capability to fabricate large metal parts with high deposition rate and low equipment cost. Although this method is gaining popularity in manufacturing industry, more research is needed to understand process parameters’ effects on residual stress (RS) distribution and part distortion. As such, a 3D thermo-elastic-plastic transient model was established in ABAQUS and employed to investigate the effect of process parameters such as the torch speed, the deposition power and the interlayer dwell time on RS distribution and distortion in WAAM part. The numerical model utilized a comprehensive three-dimensional transient heat transfer model to calculate the temperature distribution and gradient in WAAM process for various process parameters. The heat source was reproduced by a user subroutine DFLUX in ABAQUS. The calculated temperature was exported into mechanical model to predict residual stress and distortion. Variation of microstructural morphology in WAAM components is also critical as it can influence RS in the part. Therefore, the USDFLD user subroutine was utilized to incorporate mechanical property change due to microstructure variation in the mechanical analysis. Both thermal and mechanical models were validated with the experimental data. A 30-layer high wall was built using a GMA-WAAM process with a collaboration with students at Clarkson University.

The WAAM setup utilized a gas metal arc welding process for deposition of hot 718 Inconel electrode on a A36 steel substrate. Temperature histories, which is necessary for validating the thermal model, were collected at five locations on the substrate. Lattice spacing for strain calculation was measured by neutron diffraction technique on ex-situ basis, at Oak Ridge National Laboratory. The numerical results showed process parameters can induce significant impact on RS and distortion in the WAAM part. As such, these parameters should be optimized to produce WAAM parts with low RS.

DOI

10.25777/snsx-4x28

ISBN

9798557054553

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