LEE- Katı Cisimlerin Mekaniği Lisansüstü Programı

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http://hdl.handle.net/11527/19329

Gözat

Konu "3D printing" ile LEE- Katı Cisimlerin Mekaniği Lisansüstü Programı'a göz atma
  • Öge
    Numerical modeling of sintering in binder jetting additive manufacturing process
    (Graduate School, 2025-05-26) Yalçın, Mehmet Fatih ; Söylemez, Emrecan ; 503231508 ; Solid Mechanics
    Binder jetting additive manufacturing (BJT) is a significant additive manufacturing (AM) method due to its capability to produce complex geometries, print unsupported parts without being affected by residual stresses, and enable high-speed fabrication compared to other AM methods. While BJT offers a faster production capacity compared to other AM methods, it requires post-processing techniques such as sintering or infiltration to achieve full density. Challenges such as shrinkage during sintering and the need for precisely controlled furnace conditions make it a demanding technique to work with. In this thesis, a custom in-situ camera system was employed to observe the geometric shrinkage of green parts produced via the BJT process during sintering, and the shrinkage was measured using image processing techniques. The dimensional shrinkages recorded from images taken at specific intervals inside the furnace were used to calibrate the experimental coefficients in the Arrhenius-form sintering constitutive relation. Subsequently, finite element analyses (FEA) were conducted using this calibrated temperature profile on various geometries via Ansys software. Moreover compensated geometries were established through case studies within tolerances of the designed final parts. Experiments were conducted using two different furnaces in the study. The alumina tube furnace setup was used as the furnace from which we could take images with a camera. Second furnace is called vacuum furnace. For sintering larger parts, a recipe equivalent to the tube furnace was found in the vacuum furnace and used for them. Chapter 1 provides a literature review on the BJT process, key parameters for jettable binders, debinding issues, sintering stages, and the derivation of the linear viscous constitutive relation for sintering. Chapter 2 covers material characterization, printing, post-printing processes, the in-situ image processing setup developed for sintering, and the experimental results. In Chapter 3, the Arrhenius-form constitutive relation was calibrated using the time-dependent shrinkage behavior of the cube geometry presented in Chapter 2. Based on this calibration, FEA simulations were performed. The chapter then presents a comparison between the FEA results and the sintered part geometries, in which the final parts were scanned using a three-dimensional (3D) scanner. Deviations between the FEA predictions and the actual parts were evaluated for both the original and the compensated geometries. The sintering deformation predictions showed strong agreement with experimental results, with average deviations typically below 2-3% across most geometries. Maximum deviations were observed to be less than 5% for moderately thick regions and up to 10% in locally thin sections, when evaluated relative to the original reference height of the part.