2024 Annual International Solid Freeform Fabrication Symposium (SFF Symp 2024): Applications: Analysis, Modeling, and Optimization
Program Organizers: Joseph Beaman, University of Texas at Austin
Monday 1:30 PM
August 12, 2024
Room: Salon A
Location: Hilton Austin
Session Chair: Chukwuzubelu Ufodike, Texas A&M University
1:30 PM Cancelled
Rapid Qualification and Process Optimization of an LPBF Printer for Printing Complex Thermofluidic Units: Junwon Seo1; Nicholas Lamprinakos1; Yu-Tsen Yi1; Anthony Rollett1; 1Carnegie Mellon University
Laser powder bed fusion (LPBF) additive manufacturing allows the fabrication of complex geometries that were practically impossible to fabricate with conventional methods, allowing for more efficient designs of thermo-fluidic components. LPBF requires a process optimization, where various process parameters including the laser power and scanning speed, are varied to minimize the amount of defects in the part. However, in large, part-scale geometries, the optimal process parameters may not be the same at different locations. In this research, we investigate the effect of the geometry and the build height on the melt pool dimensions, which in turn affects the defect content and the microstructure. The study shows a measurable shift of the optimal process window within thin walls, overhangs, and tall builds. We also provide an exemplary process optimization where thermo-fluidic components are fabricated in alloys 282 and 316L, in two LPBF printers with different spot sizes.
1:50 PM
Custom Cathode Optimization for Electropolishing Additively Manufactured 316L Stainless Steel: Kasandra Escarcega Herrera1; Michael Melia1; Mary Louise Gucik1; Jason Taylor1; 1Sandia National Laboratories
Laser powder bed fusion (LPBF) has become increasingly popular for its ability to create complex geometries. However, LPBF creates tortuous surfaces that may degrade overall performance. Consequently, post-processing is often needed for LPBF parts through techniques such as electropolishing (EP). Utilizing COMSOL, this project aims to enhance EP of a LPBF 316L T-shaped part in a polyethylene glycol/NaCl based electrolyte by optimizing the cathodes to smooth the T-shaped surface more efficiently. First, different electrode spacings were experimentally compared using a 316L flat lattice cathode. Next, cylindrical and conformal cathodes of increasing sizes were evaluated. Based on those results, a cathode was then optimized using COMSOL to polish an anode selectively and uniformly. Roughness measurements and optical images were acquired and compared before and after polishing to quantify EP efficacy. SNL is managed and operated by NTESS under DOE NNSA contract DE-NA0003525.SAND2024-04664A
2:10 PM
Analytical prediction of texture of multi-phase materials in laser powder bed fusion: Wei Huang1; 1Gatech
Crystallographic orientations are critical in determining material properties among all microstructure representations due to their influence on anisotropy, void growth, coalescence behaviors, etc, in LPBF. This paper first developed a physics-based analytical model to predict the multi-phase materials texture related to the 3D temperature distribution, considering heat transfer boundary conditions, heat input using point-moving heat source solution, and heat loss due to heat conduction, convection, and radiation. This study offers a quick and more precise way of analyzing texture prediction in multi-phase mode for metallic materials. It lays the groundwork for future research on microstructure-affected or texture-affected materials' properties in academic and industrial settings. This study initially employs a computational approach to generate a singular BCC beta phase texture based on thermal history to represent the liquidus materials of Ti-6Al-4V during the melting process.
2:30 PM
Hybrid LP-DED for Thin Components: James Wateska1; Carolyn Seepersad1; 1Georgia Tech
Hybrid Manufacturing integrates metal additive manufacturing with machining to fabricate dimensionally accurate components, particularly excelling in near-net-shape manufacturing. However, manufacturing thin and complex structures remains a challenge under tight dimensional tolerances. The lack of surrounding stock material from the deposition phase introduces less rigidity during the milling process, resulting in an increased susceptibility to vibrations and chatter. To mitigate these issues, the implementation of optimized sacrificial structures is proposed. This approach relies on accurate data concerning the deflections of both the tool and the workpiece, influenced by the geometry of the milling tool and the mechanical properties of the deposited material. Thus, current work directions include: (1) utilizing a mechanistic force model to predict interactions between the milling tool and the deposited workpiece, and (2) incorporating these predictions into a Finite Element model in Abaqus to simulate and forecast milling-induced deflections.
2:50 PM
Development and Optimization of Additively Manufactured Inconel 718 Thin Walls Printed via Laser Powder Bed Fusion with a Roller Recoater and Fine Powder: Lucas Becker1; 1AddUp Inc.
Additive manufacturing allows for thinner and more complex design features than what traditional manufacturing methods can offer. Inconel 718 is a suitable material for thin feature applications at high temperatures due to its age hardenability, which allows for retention of desirable tensile properties at elevated operating temperatures. Thin wall parameters were developed for Inconel 718 printed on a Laser Powder Bed Fusion (LPBF) printer using fine powder and a roller recoater. Walls with a thickness of 200 µm and single pass walls were achieved by optimizing primary processing parameters like laser power, scan speed, and contour order. The resulting parameter set created stable 200 µm thin walls with as-printed roughness (Ra) values around 4 µm. Stable and fully continuous single pass thin walls were also created at thickness of 75 and 100 µm. Additionally, etched sample micrographs were taken to evaluate the microstructures.
3:10 PM Break
3:40 PM
Characterization of the Tensile Behavior of Single and Multi-strut Ti64 Fabricated via Laser Powder-bed Fusion: Beytullah Aydogan1; Rabiul Islam1; Kevin Chou1; 1University Of Louisville
Laser powder-bed fusion is a leading technique for manufacturing intricate metal geometries, with lattice structures playing a key role. These structures reduce mass while maintaining mechanical strength by using small, thin cells. The overall mechanical behavior is closely linked to these individual features. Therefore, characterizing the mechanical behavior of small features becomes crucial for enhancing the overall mechanical strength. This study aims to address this challenge by fabricating thin struts of Ti64 using laser powder-bed fusion. Tensile coupons were fabricated at a 90-degree angle with a thin section at the center of the gauge. Circular and square geometries were fabricated with one, two, four, and nine pillars using five different process parameters. Tensile testing was conducted for each sample at least three times. The ultimate strengths were found to be consistent with those of laser-fabricated Ti64. However, premature failures were predominantly observed in multi-pillar samples with nine pillars.
4:00 PM
Size Effect on Porosity of Thin Struts Fabricated by Laser Powder-Bed Fusion (L-PBF): Nismath Vadakkan Habeeb1; David Jaggers1; Kevin Chou1; 1University of Louisville
The melt pool fluctuations under constantly changing physical phenomena cause porosity defects in the L-PBF parts. Melt pool variations across different layers depend largely on the process parameters. Scan length is one of the significant factors affecting the melt pool geometry. The melt pool fails to reach a quasi-steady state at shorter scan lengths. Hence, thin features made of shorter scan lengths of dimensions 2 mm or less show distinctive characteristics compared to bulk-sized components. Considering its wide range of applications, especially in biomedical industries, an in-depth investigation of thin features is essential. This study aims to analyze the porosity characteristics of thin struts fabricated via L-PBF process. The thin struts of different sizes and shapes were printed using Ti6Al4V powder at various processing conditions. The porosity and dimensional accuracy were characterized by using a micro-CT scanner and the results were evaluated using various 2D and 3D image analysis tools.
4:20 PM Cancelled
Investigating Wicking Structures for Haynes230-RAM Heat Pipes: Adnen Mezghani1; Edward Reutzel2; Saya Lee1; Christopher Balbier1; 1Pennsylvania State University; 2Applied Research Laboratory at Penn State
Heat pipes can achieve extremely high thermal conductivity through cyclic evaporation and condensation of a working fluid. High-temperature heat pipes that utilize alkali metal as the working fluid are attractive in many high-temperature applications, such as thermal protection of hypersonic leading edges and thermal management and energy harvesting in nuclear microreactors. However, conventional fabrication methods for heat pipes require multiple manufacturing and assembly steps which limit design space. Moreover, high-temperature alloys such as nickel-based alloys are especially difficult to fabricate due to high strength and hardness. Alternatively, utilizing additive manufacturing (AM) can bypass conventional manufacturing limitations through part consolidation and produce structural members with intricate internal channels. In this work we explore the fabrication of heat pipe components, namely the wicking structure, in a modified nickel-based alloy Ni230-RAM (similar to Haynes 230). Implications of the implemented designs and methods on the manufacturability and quality of the wicking structures are discussed.
4:40 PM
Effects of Process Parameters and Print Orientation on the Manufacturability and Fluid Wicking Performance of Additively Manufactured Inconel 718 Wicks For Heat Pipes: Cameron Noe1; Dhruv Bhate1; Tatiana EL Dannaoui2; Alexander Rattner2; 1Arizona State University; 2Pennsylvania State University
Thermal management is a common challenge in a range of engineering disciplines. Using additive manufacturing techniques, it is possible to create integrated wicking heat pipe structures for component level thermoregulation. One of the key elements to a functional integrated heat pipe is the fluid wick structure. The focus of this study is to quantify the effects of laser powder bed fusion printing process parameters and build orientation on wicking performance. Several factors such as wick porosity, permeability, effective pore radius, and presence of defects were studied to identify candidates for future heat pipe applications. In addition to performance metrics, correlation between print parameters, build orientation, and manufacturing defects are studied. The effects of overhanging wick geometry are also explored. Exploring many potential wicking parameters and print orientations yields insight into parameter choices that result in the most functional wicks with the fewest defects.
5:00 PM
Influence of Testing Method on Fatigue Performance of PBF-LB 316L Stainless Steel with As-Built Surfaces: Edwin Glaubitz1; Orion Kafka2; Nik Hrabe2; Joy Gockel1; 1Colorado School of Mines; 2National Institute of Standards and Technology
As-built surfaces of components produced using laser powder bed fusion (PBF-LB) are rougher compared to other manufacturing processes. Valleys on as-built surfaces often act as the crack initiation sites during fatigue. Two commonly used fatigue testing methods are axial and four-point rotating beam fatigue tests, which produce different stress distributions throughout the cross-section of the material in the gauge section. Fatigue specimens made with 316L stainless steel with as-built surfaces of varying roughness and porosity are tested using both techniques. In four-point bending fatigue, the maximum stress is on the surface of the specimen, whereas in axial fatigue the stress is uniform across the cross-section. Relationships between measured surface roughness, fatigue test method, and fatigue life are analyzed. Understanding the influence of surface roughness and testing method (i.e., stress profile) on fatigue life of as-built surfaces will improve transferability of functional correlations between surface roughness measurement and performance.