2019 International Solid Freeform Fabrication Symposium
Permanent URI for this collectionhttps://hdl.handle.net/2152/89836
Proceedings for the 2019 International Solid Freeform Fabrication Symposium. For more information about the symposium, please see the Solid Freeform Fabrication website.
The Thirtieth Annual International Solid Freeform Fabrication (SFF) Symposium – An Additive Manufacturing Conference, held at The University of Texas in Austin on August 12-14, 2019, was attended by 701 researchers from 25 countries. The number of oral and poster presentations increased to 557 this year. The meeting was held on the Hilton Austin in the downtown area. The meeting consisted of a Monday morning plenary, 64 parallel technical sessions and a poster session.
The recipient of the International Outstanding Young Researcher in Freeform and Additive Manufacturing Award was Dr. Xiaoyu (Rayne) Zheng from Virginia Tech University. Dr. Olaf Diegel from the University of Auckland in New Zealand won the International Freeform and Additive Manufacturing Excellence (FAME) Award.
There are 197 papers in the conference proceedings. Papers marked "REVIEWED" in the title area were peer reviewed by two external reviewers. We have sequentially numbered the pages of the papers to facilitate citation. Manuscripts for this and all preceding SFF Symposia are available for free download below and at the conference website: http://sffsymposium.engr.utexas.edu/archive.
Nine materials-related papers were selected as best papers for inclusion in the journal JOM under the aegis of The Minerals, Metals & Materials Society (TMS). Two of these papers were substantially improved for the journal with the original also appearing in this proceedings. Seven were moved with only minor modification; these do not appear in the proceedings. The abstracts of these nine papers appear in the proceedings immediately before the first article. The special issue of JOM was published in the March 2020 issues of JOM.
A student lunch and panel discussion was provided on August 13th, 2019. A panel discussion with a focus on navigating the transition into career positions in the AM field was conducted with ample opportunities for the students to ask questions. The panel featured four recent PhD graduates working in the field of AM in academia, industry, and a national lab. The panel included, (1) Dr. David Epsalin (Assistant Professor - University of Texas at El Paso and Director of Research at the W.M. Keck Center for 3D Innovation), (2) Ben Fulcher (EOS North America), (3) Dr. Brian Gierra (Principle Investigator at Lawrence Livermore National Laboratory) and (4) Dr. Joy Gockel (Assistant Professor in Mechanical and Materials Engineering at Wright State University). The luncheon was attended by approximately 200 students.
The editors would like to thank the Organizing Committee, the session chairs, the attendees for their enthusiastic participation, and the speakers both for their significant contribution to the meeting and for the relatively prompt delivery of the manuscripts comprising this volume. We are grateful to TMS conference management staff for their significant contributions to the meeting planning and proceedings production, particularly Trudi Dunlap, Jennifer Booth, and Kelcy Wagner. We look forward to the continued close cooperation of the additive manufacturing community in organizing the Symposium. We also want to thank the Office of Naval Research (N00014-19-1-2678) and the National Science Foundation (CMMI-1934397) for supporting this meeting financially. The meeting was co-organized by the Mechanical Engineering Department/Lab for Freeform Fabrication under the aegis of the Advanced Manufacturing and Design Center at the University of Texas at Austin. The 2020 SFF Symposium is set for August 17-19, 2020 at the Hilton Austin Hotel in Austin, Texas, USA.
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Item 2019 International Solid Freeform Fabrication Symposium Table of Contents(2019) Laboratory for Freeform Fabrication and University of Texas at AustinItem 3D Printing of Compliant Passively Actuated 4D Structures(University of Texas at Austin, 2019) Jayashankar, Dhileep Kumar; Gupta, Sachin Sean; Stella, Loo Yi Ning; Tracy, KennethAdditive manufacturing has begun to revolutionize the production of various physical technologies that depend on bespoke geometry and tailored material properties for function. This includes the design of compliant mechanisms, which rely on an integral coupling between geometric and material parameters to attain the elastic flexibility necessary to accommodate programmed deformation. While kinetic structures with compliant parts are typically activated by the application of a mechanical force, alternative means of achieving motion are available, such as the use of smart, 4D, or stimuli-responsive materials which react to environmental conditions. In this research, a combination of compliant mechanisms and water-responsive chitosan biopolymers was explored to create flexible, programmable passive actuators, enabled by 3D printing. A set of compliant joints were modeled, simulated, fabricated, and tested to determine the optimal design for use in the actuator. The actuator was then iteratively tested with wetting and drying of chitosan films to invoke a specific shape change, which was analyzed for accuracy, speed, and consistency. The study concluded with a discussion of the implications of synthesizing compliant mechanisms, chitosan biopolymer, and additive manufacturing for next-generation adaptive structures.Item Additive Manufactured Lightweight Vehicle Door Hinge with Hybrid Lattice Structure(University of Texas at Austin, 2019) Aydin, I.; Akarcay, E.; Gumus, O.F.; Yelek, H.; Engin, C.B.Item Additive Manufacturing of Fatigue Resistant Materials: Avoiding the Early Life Crack Initiation Mechanisms During Fabrication(University of Texas at Austin, 2019) Pegues, Jonathan; Roach, Michael; Shamsaei, NimaThe full potential of additive manufacturing (AM) has been limited by the process induced defects within the fabricated materials. Defects such as lack of fusions and gas entrapped pores act as stress concentrators and result in premature fatigue crack initiation, severely limiting the applicability of AM in fatigue-critical applications. However, by understanding the failure mechanisms associated with AM materials and leveraging the intimate localized thermal input (i.e. process conditions), the failure mechanisms for some materials may be avoided during the fabrication process. This study investigates the crack initiation behavior of an AM austenitic stainless steels subjected to fatigue testing. The microstructural features responsible for fatigue crack initiation are captured at the surface by ex-situ electron backscatter diffraction. Results show that the higher cooling rates during AM offer the opportunity to fabricate fatigue resistant austenitic stainless steel parts by avoiding the microstructural features that are most detrimental to fatigue performance.Item Additive Manufacturing of High-Gamma Prime Nickel-Based Superalloys through Selective Laser Melting (SLM)(University of Texas at Austin, 2019) Basak, AmritaHigh-ℽ' nickel-based superalloys are abundantly used in the aerospace, marine, nuclear, and chemical industries where excellent corrosion and oxidation resistance, superior mechanical properties, and exceptional high-temperature performance are required. However, selective laser melting (SLM)-based additive manufacturing (AM) of high-ℽ' nickel-based superalloys pose significant challenges due to these alloys’ complex chemistry. With multiple alloying elements and high aluminum + titanium fraction, these materials when consolidated through SLM form various secondary phases severely affecting the processability leading to the formation of cracks. The objective of this review is to summarize the progress made so far on SLM of high-ℽ' nickel-based superalloys with a special emphasis towards elucidating the relationships between processing, microstructures, and properties in this alloy system.Item Alternative Approach on an In-Situ Analysis of the Thermal Progression During the LPBF-M Process Using Welded Thermocouples Embedded into the Substrate Plate(University of Texas at Austin, 2019) Schnell, N.; Siewert, M.; Kleszczynski, S.; Witt, G.; Ploshikhin, V.Laser powder bed fusion (LPBF-M) is a very potent technology for creating highly individualized, complex, and functional metal parts. One of the major influencing factors is the thermal progression. It significantly determines size accuracy, microstructure and process stability. Therefore, creating an enhanced understanding of thermal phenomena through measurements and simulations is crucial to increase the reliability of the technology. Current research is mainly based on temperature measurements of the upper layer, leaving major scope for the conditions at the substrate-part-interface. This area is of utmost technical importance because it serves as the main heat sink. Insufficient heat dissipation leads to accumulations of heat, deformations, and process breakdowns. This contribution presents a simple and flexible method to analyze the thermal progression close to the part inside the substrate plate. The acquired data shows very high consistency. Additionally, the results are compared to a model created using an ISEMP developed FEM-Software which shows promising results for validation studies.Item An Aluminum-Lithium Allloy Produced by Laser Powder Bed Fusion(University of Texas at Austin, 2019) Qi, Yang; Zhang, Hu; Zhu, Haihong; Nie, Xiaojia; Zeng, XiaoyanAluminum-lithium (Al-Li) alloys are promising to replace traditional high-strength aluminum alloys in aerospace and military industries due to their low density, high specific strength, and excellent corrosion resistance. However, there is little research focused on the laser powder bed fusion (LPBF) of Al-Li alloys due to their poor weldability and high crack susceptibility. In this study, the feasibility of the Al-Li alloy fabricated by LPBF was investigated. The effect of the processing parameters on the densification and crack formation behavior was studied. Finally, after optimizing the processing parameters, crack-free and nearly fully dense 2195 Al-Li alloy 3D-printed samples were obtained. A relative density of 99.92% and a microhardness of 89.1 HV were achieved.Item Analysis of Fatigue Crack Evolution Using In-Situ Testing(University of Texas at Austin, 2019) Alqahtani, Hassan; Keller, Eric; Ray, Asok; Basak, AmritaThe objective of the current work is to investigate the feasibility of an in-situ technique to characterize the evolution of fatigue failure in conventionally manufactured aluminum parts in real time. An in-situ fatigue testing setup integrated with ultrasonic transducers and a digital microscope allows for the systematic study of fatigue crack evolution in aluminum specimens. The resulting data from experimentation, characterization, and analysis are integrated to gain unprecedented insights into the evolution of fatigue failure in wrought aluminum parts. The learning from this work will be further implemented on additively manufactured specimens.Item Analysis of Layer Arrangements of Aesthetic Dentures as a Basis for Introducing Additive Manufacturing(University of Texas at Austin, 2019) Pitz, K.; Anderl, R.Aesthetic dentures are highly individual products, needing to adapt to the patient’s natural dentition in both color and shape. In general, dentures are geometrically complex structures, consisting of several layers of different materials, which are applied consecutively. This is why efforts are being made to introduce additive manufacturing into the production process of aesthetic dentures which is to date largely based on manual work of skilled professionals. In order to successfully apply additive manufacturing accurate models of the denture to be produced are essential. In this paper the layer arrangements of dental crowns from real patient cases are analyzed. Different approaches, based on normal vectors, cylindrical coordinates, spherical coordinates and paraxial rays, are compared to each other. The emphasis of this comparison lies on transferring layering strategies from analyzed patient cases to future patient cases where the geometry might be slightly different but a similar optical impression is desired. The most suitable approach for this purpose has been identified, implemented and tested.Item Analysis of Powder Removal Methods for EBM Manufactured Ti-6Al-4V Parts(University of Texas at Austin, 2019) Lopes, Amit J.; Ramos, Luis C.; Saenz, David; Morton, Philip; Terrazas, Cesar A.; Choudhuri, Ahsan; Wicker, RyanAdditive Manufacturing (AM) allows the creation of complex geometries that are not achievable through subtractive manufacturing. Regardless of the advantages that 3D Printing offers, technology limitations often constraints the desired geometry. When fabricating Ti-6Al4V parts in Electron Beam Powder Bed Fusion (EBPBF), the electron beam is used to preheat the powder bed to maintain the desired temperature gradient during the build. One disadvantage of EBPBF during the fabrication process is the trapped powder within internal channels gets partially sintered and require extra processing. This research analyzes several powder removal methods and compares their effectiveness. This work utilizes two types of samples, both made of Ti-6Al4V in EBPBF; with geometries that resemble typical features when designing a component. The target weight of each cylinder is calculated based on dimensions and effective density of the sample. The results summarizing the effectiveness of each method are presented.Item Analysis of the Shielding Gas Dependent L-PBF Process Stability by Means of Schlieren and Shadowgraph Techniques(University of Texas at Austin, 2019) Hoppe, B.; Enk, S.; Schleifenbaum, J.H.Ensuring a robust and reproducible Laser Powder Bed Fusion (L-PBF) process depends on the design of the shielding gas flow in the corresponding manufacturing system. The gas flow assures the removal of particles from the process zone that emerge from the interaction with the laser irradiation. Minor disturbances may influence the stability of the L-PBF-Process and cause defects in final parts produced. The objective of this work comprises visualizing the convection processes and particle dynamics to analyze their influence on process stability. Therefore, a high speed camera based Schlieren and Shadowgraph setup is used to visualize convection flows as well as trajectories of metallic condensate and particles with up to 10,568 fps. This arrangement allowed investigating the influence of shielding gas flow conditions on single melt tracks. Corresponding results and studies on the interaction between laser irradiation and particles in varying shielding gas flow conditions are contents of this work.Item Application of Schlieren Technique in Additive Manufacturing: A Review(University of Texas at Austin, 2019) Bharadwaja, R.; Murugan, Aravind; Chen, Yitao; Liou, F WAdditive manufacturing has gained a lot of attention in the past few decades due to its significant advantages in terms of design freedom, lower lead time, and ability to produce complex shapes. One of the pivotal factors affecting the process stability and hence the part quality is the shielding gas flow in additive manufacturing. As extremely beneficial for the process, the shielding gas flow is often set at maximum supply to achieve enough gas cover over the substrate. This causes excessive quantity of shielding gas to be unutilized. Realizing the importance of shielding gas, various studies have been carried out to monitor and visualize the shielding gas, and one such technique is Schlieren imaging. Schlieren visualization has been used since the 1800s as a powerful visualization tool to visualize fluctuations in optical density. The Schlieren technique is highly effective for visualizing and optimizing shielding gas flow. This paper aims to provide an overview of Schlieren technique used for visualization of shielding gas and highlights the application of Schlieren in additive manufacturing.Item Application of the Fog Computing Paradigm to Additive Manufacturing Process Monitoring and Control(University of Texas at Austin, 2019) Adnan, Muhammad; Lu, Yan; Jones, Al; Cheng, Fan TienMonitoring and controlling Additive Manufacturing (AM) processes play a critical role in enabling the production of quality parts. AM processes generate large volumes of structured and unstructured in-situ measurement data. The ability to analyze this volume and variety of data in real-time is necessary for effective closed-loop control and decision-making. Existing control architectures are unable to handle this level of data volume and speed. This paper investigates the functional and computational requirements for real-time closed-loop AM process control. The paper uses those requirements to propose a function architecture for AM process monitoring and control. That architecture leads to a fog-computing solution to address the big data and real-time control challenges.Item Applications of Supervised Machine Learning Algorithms in Additive Manufacturing: A Review(University of Texas at Austin, 2019) Joshi, M.S.; Flood, A.; Sparks, T.; Liou, F.W.Additive Manufacturing (AM) simplifies the fabrication of complex geometries. Its scope has rapidly expanded from the fabrication of pre-production visualization models to the manufacturing of end use parts driving the need for better part quality assurance in the additively manufactured parts. Machine learning (ML) is one of the promising techniques that can be used to achieve this goal. Current research in this field includes the use of supervised and unsupervised ML algorithms for quality control and prediction of mechanical properties of AM parts. This paper explores the applications of supervised learning algorithms - Support Vector Machines and Random Forests. Support vector machines provide high accuracy in classifying the data and is used to decide whether the final parts have the desired properties. Random Forests consist of an ensemble of decision trees capable of both classification and regression. This paper reviews the implementation of both algorithms and analyzes the research carried out on their applications in AM.Item Approach to Defining the Maximum Filler Packing Volume Fraction in Laser Sintering on the Example of Aluminum-Filled Polyamide 12(University of Texas at Austin, 2019) Tarasova, A.; Wegner, A.; Witt, G.Laser sintering is one of the most popular additive manufacturing techniques that uses thermoplastic polymer powders to generate layer-by-layer complex structures. Despite its broad application, some limitations exist restricting its further development. One such restriction is a narrow assortment of commercially available materials that would allow the production of the parts with the desired mechanical characteristics, which is the case with the widely used Polyamide 12 (PA12). Reinforcement of a matrix polymer with metal particles is routinely performed to achieve better mechanical properties. In this work, a PA12 system enhanced with a 35% volume ratio of aluminum was investigated. Mechanical characteristics, e.g. elastic and flexural moduli, were examined with respect to variation of manufacturing process parameters. In addition, a new methodology was tested, which should help determine the maximum filler packing volume fraction corresponding to the highest mechanical characteristics of a polymer-filler mixture.Item An Automated Method for Geometrical Surface Characterization for Fatigue Analysis of Additive Manufactured Parts(University of Texas at Austin, 2019) Rasoolian, Behnam; Pegues, Jonathan; Shamsaei, Nima; Silva, DanielRecent interest to implement additive manufactured parts into structural applications has created a critical need to better understand the fatigue behavior of these parts. Alloys such as Ti-6Al-4V are popular in the aerospace and biomedical industries due to their superior strength to weight ratio and biocompatibility. Previous works have associated fatigue behavior with surface roughness, especially radius of curvature of notches. It is therefore important to develop a fast, reliable and consistent methodology for extracting such curvatures. The contribution of this paper is in providing an automated method for extracting radius of curvature using image processing techniques and optimization. Results on fatigue life prediction indicates similar results between the automated method and manually extracted radii in a significantly shorter period of time.Item Binder Saturation, Layer Thickness, Drying Time and Their Effects on Dimensional Tolerance and Density of Cobalt Chrome - Tricalcium Phosphate Biocomposite(University of Texas at Austin, 2019) Ruprecht, John; Agarwal, Kuldeep; Ahmed, ShaheenTraditional metals such as stainless steel, titanium and cobalt chrome are used in biomedical applications (implants, scaffolds etc.) but suffer from issues such as osseointegration and compatibility with existing bone. One way to improve traditional biomaterials is to incorporate ceramics with these metals so that their mechanical properties can be similar to cortical bones. Tricalcium phosphate is such a ceramic with properties so that it can be used in human body. This research explores the use of binder jetting based additive manufacturing process to create a novel biocomposite made of cobalt chrome and tricalcium phosphate. Experiments were conducted and processing parameters were varied to study their effect on the printing of this biocomposite. Layer thickness, binder saturation and drying time affected the dimensional tolerance and the density of the green samples. This effect is important to understand so that the material can be optimized for use in specific applications.Item Cellular and Topology Optimization of Beams under Bending: An Experimental Study(University of Texas at Austin, 2019) Gopal, Arjun; Parihar, Gaurav; Holt, McKay; Stinson, Tanner; Sharma, Manasvi; Bhate, DhruvDesign for Additive Manufacturing (AM) includes concepts such as cellular materials and topology optimization that combine the capabilities of advanced computational design with those of AM technologies that can realize them. There is however, limited experimental study of the relative benefits of these different approaches to design. This paper examines these two different approaches, specifically in the context of maximizing the flexural rigidity of a beam under bending, while minimizing its mass. A total of 23 beams were designed using commercially available cellular design, and topology optimization software. The Selective Laser Sintering (SLS) process was used to manufacture these beams with Nylon 12, which were then tested per ASTM D790 three-point bend test standards. The effect of varying the size and shape of cells on the flexural rigidity was studied using 15 different cellular designs. These results were then compared to six different topology optimized beam designs, as well as three solid and hollow baseline beams. These preliminary findings suggest that topology optimized shapes underperform their cellular counterparts with regard to specific stiffness, and that stochastic cellular shapes deserve deeper study.Item Characterisation of Austenitic 316 LSi Stainless Steel Produced by Wire Arc Additive Manufacturing with Interlayer Cooling(University of Texas at Austin, 2019) Cunningham, C.R.; Wang, J.; Dhokia, V.; Shrokani, A.; Newman, S.T.Wire arc additive manufacturing (WAAM) expands the possibilities of cost effectively producing large-scale, complex metal objects at high deposition rates. Austenitic stainless steel is a commonly used material and has many applications in the marine and nuclear industry due to its high toughness and corrosion resistance. Processes parameters such as heat input and interpass temperature can greatly affect the materials properties, part functionality and the economics of WAAM production. However, the effect of these process parameters is not well understood for WAAM of 316LSi. In this research, the effects of the interpass temperature and heat input process parameters on WAAM of austenitic AISI 316LSi stainless steel are experimentally analysed and evaluated. It was found that the heat input and interpass temperature influences the cellular/dendritic morphology and the formation of macro-scale grains within the microstructure. Additionally, use of higher heat input, resulted in a 28.7% improvement in average Young’s modulus compared to lower heat input, although this remained lower than provided by wrought annealed material.Item Characterization of Laser Direct Deposited Magnesium Aluminate Spinel Ceramics(University of Texas at Austin, 2019) Pappas, John M.; Dong, XiangyangAn additive manufacturing (AM) approach, via laser direct deposition, is investigated in printing transparent magnesium aluminate spinel (MAS) ceramics. Using AM, traditionally difficult or expensive to manufacture shapes, such as optical lenses, can be rapidly manufactured to near net shape, reducing time consuming and expensive post processing requirements. The transparency of MAS ceramics is highly dependent on the microstructure, with porosity and microcracking having the largest effect on the transparency of fabricated parts. With high localized heat inherent in the laser deposition process, the microstructure of ceramic parts can be controlled by adjusting processing parameters. In this study, thin wall MAS structures were fabricated by varying processing parameters. Processing parameters including laser scan speed and laser power had a large influence on the part quality. To fabricate transparent magnesium aluminate spinel ceramics with high mechanical properties, the effects of processing parameters on part porosity, density, and microstructure were studied. Dense MAS parts were successfully fabricated through the laser direct deposition process. Low scan speed and high laser power showed the most promising results in fabricating MAS parts of low porosity. Using a low powder flow rates of 0.58 g/min, a relative density of nearly 98% was achieved. Directional cooling through the substrate and from the powder conveying gas led to columnar grain growth at a tilt angle from the build direction. The primary defects of fabricated MAS ceramics were found to be residual porosity and microcracking, which negatively affected part transparency and mechanical properties. Typical microcracking patterns included transverse and longitudinal cracking, with longitudinal cracks being more prevalent due to the existence of columnar grains and intergranular fracture mode. A preliminary study demonstrated that a certain degree of transparency was achieved in additively manufactured MAS ceramic parts via laser direct deposition.