Development of a Relational Energy Balance for Additive Manufacturing

Open Access
Author:
Park, Joshua Zane
Graduate Program:
Engineering Science and Mechanics
Degree:
Master of Science
Document Type:
Master Thesis
Date of Defense:
July 09, 2015
Committee Members:
  • Richard Martukanitz, Thesis Advisor
  • Judith Todd Copley, Thesis Advisor
  • Albert Eliot Segall, Thesis Advisor
Keywords:
  • Energy Balance
  • Additive Manufacturing
  • Directed Energy Deposition
  • Heat Transfer
  • Laser
  • AM
  • DED
Abstract:
This thesis presents a proposed phenomenological, quasi-empirical model for the heat transfer of select additive manufacturing techniques through the use of an analytical energy balance, as well as results from related directed energy deposition experiments. Two sets of experiments were designed to measure deposition track geometries and melt-pool temperatures for Ti-6Al-4V and Inconel 625 alloys across a variety of processing conditions. Parameter variation experiments were conducted to examine the deposition track geometries associated with various combinations of several key user-established processing parameters. Full-factorial design was utilized for the processing parameters of laser power, velocity, and spot size in order to allow the study of the effect that each factor had on the response variable of melt-pool penetration depth for both alloys. A second set of experiments examined the thermal responses experienced in the deposition melt pool and on the substrate surface during a laser deposition process. Both Ti-6Al- 4V and Inconel 625* samples demonstrated melt-pool temperatures above the liquidus temperatures referenced in literature. These measured temperatures were recorded and used to establish not only thermophysical property data for the model, but also as direct inputs into the heat transfer equations inside the Energy Output term of the proposed energy balance model. Thirdly, an analytical energy balance was developed to examine the response that select key processing parameters have on a directed energy deposition track’s geometry. The melt-pool penetration were plotted as a response variable against laser power and velocity. Finally, the results of the model were compared with the experimental data to demonstrate the model’s potential for predicting responses in penetration data trends.