UBC Theses and Dissertations
Development of a heat transfer model of a simplified build environment in electron beam additive manufacturing Rahimi, Farhad
In this research, a 3D heat transfer model incorporating cavity radiation was developed in ABAQUS version 2017 to approximate the thermal field within the build environment in an Electron Beam Powder Bed Fusion (EB-PBF) Additive Manufacturing (AM) Process. The build environment, also referred to as the "pseudo build environment, was fabricated in an Electron Beam Button Furnace (EB BF) using an ARCAM Q20Plus heat shield (with the top section removed). The “build plate” was fabricated from a commercially pure titanium disk, which was surrounded by a stainless-steel plate. A circular beam pattern with a diameter of 50 mm was used to heat the titanium disk in the absence of powder. The experimental set-up was instrumented with type-K thermocouples to record the evolution in temperature on the heat shield walls, within the titanium disk and stainless-steel plate during the experiment. To record and store the temperature, an autonomous data acquisition system was developed for in-situ instrumentation within a vacuum environment. The model was validated with respect to the temperature data extracted from the EB BF. Overall, the results of the heating experiment and the numerical model suggest that the radiative heat exchange between various surfaces within the build environment is complex. The model results indicate that the portion of heat transferred via cavity radiation and absorbed by the heat shield walls was found to be a strong function of the titanium disk temperature. Additionally, four simple numerical case studies were developed to evaluate the effect of heating pattern, initial preheat, the heat absorption by the powder deposition sequence and post powder deposition preheat on the thermal behaviour in the pseudo build environment. The results of the numerical cases provide guidance into future model development, which can potentially aid in better understanding the heat transfer within the build environment leading to better AM process control.
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