Spreading behavior of Ti48Al2Cr2 Nb powders in powder bed fusion additive manufacturing process: experimental and discrete element method study
TL;DR: In this paper, two types of powder powders, produced by the plasma rotating electrode process (PREP) and gas atomization (GA), were compared to compare spreading behaviors and powder bed properties.
Abstract: The quality of powder beds is a key factor governing the density of bulk parts produced by the powder bed fusion–additive manufacturing (PBF-AM) process. Conventional assessments of powder flowability cannot be used to evaluate spreadability of the spreading process owing to different dynamic conditions used. Therefore, factors that have dominant effects on the powder bed properties must be investigated. In this study, two types of Ti 48Al 2Cr 2 Nb powders, produced by the plasma rotating electrode process (PREP) and gas atomization (GA), were used to compare spreading behaviors and powder bed properties. The static and dynamic flowabilities of the PREP powder were better than those of the GA powder, while the packing density and surface roughness of the powder bed were worse. During the spreading process, the recorded recoating angle gradually increased for the GA powder, while it remained constant for the PREP powder. The increase in the recoating angle for the GA powder was due to the preferential segregation of fine particles during the spreading process. The discrete element method (DEM) model was calibrated by the fitting static and dynamic angle of repose. Based on the DEM model, three particle-flow regimes were identified: the vortex region, free flowing region, and shear stress region. In the shear stress region, the contact force between the GA powder particles was lower than that of the PREP powder, resulting in high packing density. Artificial manipulation of the particle size and shape in the DEM simulation revealed that the predominant factor governing the powder bed properties between the GA and PREP powders was the particle size distribution. We believe that our study provides an improved understanding of the powder-spreading mechanism and optimization of the powder bed properties.
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TL;DR: In this paper , the results of theoretical and experimental research carried out at the PWI in the field of electrometallurgy are presented, focusing on electroslag technology (electroslag melting, refining and casting).
Abstract: Electrometallurgy Today, 2022, №03. SOVREMENNAYA ELEKTROMETALLURGIYA Quarterly scientific-technical and production journal. ISSN: 2415-8445, Since 1985. Text in Russian, contents and summaries in English. The journal presents the results of theoretical and experimental research carried out at the PWI in the field of electrometallurgy. Special attention is given to electroslag technology (electroslag melting, refining and casting). The journal is divided into the following main sections: electroslag technology; electron beam processes; plasma arc technology; vacuum arc remelting and vacuum induction melting; general problems of special electrometallurgy.
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TL;DR: In this article , a physical model is proposed to predict the maximum fraction of spread layer at the specified gap height, and the simulation results are validated by comparing the total particle volume of spread layers with the experimental and numerical data in previous work.
Abstract: Powder spreadability is critical to particle spread layer and thus the quality of final product in powder-based additive manufacturing, but the metrics and the underlying mechanics have not yet been well acknowledged. In this work, the metrics of spreadability are examined for powder with different size classes, and the factors affecting powder spreadability are analysed, in which both the cohesion and interlocking of particles are included. The simulation results are validated by comparing the total particle volume of spread layer against the experimental and numerical data in previous work. The results show that relative powder spreadability should be compared at the same ratio of the gap height to particle size, especially for the powders with different particle size classes. Powder spreadability is mainly controlled by the shear action of the blade on the heap, the stagnation effect due to rough surface of substrate, particle jamming around the gap region, and the effect of powder flowability on the movement of particles within the heap. Jamming makes powder spreadability different from powder flowability. As particle jamming is more prone for the particles with strong interlocking, powder spreadability is more sensitive to the rolling friction than the cohesion of particles, especially for the substrate surface with small roughness, although the rheological behaviour of bulk particles is similar in front of the gap. A physical model is proposed to predict the maximum fraction of spread layer at the specified gap height.
1 citations
TL;DR: In this paper , a high-fidelity particle-scale model was developed to capture the dynamics of metal particle interactions in a virtual Hall flow meter based on a modified Beverloo law.
Abstract: This work aims to improve the powder-bed spreading process for laser powder bed fusion additive manufacturing by gaining a greater understanding of metal powder flowability through numerical modelling and in-situ experimentation.Using the Discrete Element Method (DEM) to study the flowability of the powder and its intrinsic properties. A high-fidelity particle-scale model was developed to capture the dynamics of metal particle interactions in a virtual Hall flow meter based on a modified Beverloo law. The results are validated experimentally using the Hall flow static powder characterisation technique.For SS316L powder alloy with the hall-value of 29s/50g and with an angle of repose (AOR) of 32, the modelled powder that exhibited the same flow behaviour was found using 0.5 for both rolling and sliding coefficients resulting in simulated Hall value of 28.55s/50g with a simulated flow rate of 0.571 g/s, which is validated by AOR of the simulated powder [31.2-32.6]. However, rolling friction had minimal effect on the mass flow rate but increased the angle of repose. Sliding friction significantly decreased the mass flow rate and increased AOR.DEM is an ideal method to study flowability. However, there are certain constraints imposed on the computational power by a number of simulated particles and simulation time-step. Future research may involve investigating other dynamic flowability characterisation techniques.Enabling a better understanding of powder particle flow at a micro-scale by modelling powder flowability. This leads to simulating a more realistic powder bed and improving the powder spreading process, leading to better AM parts quality.This paper provides a unique approach for modelling the flowability of SS316L powder using a Beverloo law-based design of the Hall flow meter. This will improve the modelling of the spreading process needed for metal 3D printing.
TL;DR: The Paton Welding Journal as mentioned in this paper is a cover-to-cover English translation of the Avtomaticheskaya Svarka (Automatic Welding) journal, published monthly since 1948 in Russian, ISSN 005-111X.
Abstract: The Paton Welding Journal, 2022, №09. International Scientific-Technical and Production Journal «The Paton Welding Journal» «The Paton Welding Journal» has been published monthly since 2000 in English, ISSN 0957-798X. «The Paton Welding Journal» is a cover-to-cover English translation of the «Avtomaticheskaya Svarka» (Automatic Welding) journal. The «Avtomaticheskaya Svarka» journal has been published monthly since 1948 in Russian, ISSN 005-111X.
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TL;DR: The distinct element method as mentioned in this paper is a numerical model capable of describing the mechanical behavior of assemblies of discs and spheres and is based on the use of an explicit numerical scheme in which the interaction of the particles is monitored contact by contact and the motion of the objects modelled particle by particle.
Abstract: The distinct element method is a numerical model capable of describing the mechanical behaviour of assemblies of discs and spheres. The method is based on the use of an explicit numerical scheme in which the interaction of the particles is monitored contact by contact and the motion of the particles modelled particle by particle. The main features of the distinct element method are described. The method is validated by comparing force vector plots obtained from the computer program BALL with the corresponding plots obtained from a photoelastic analysis. The photoelastic analysis used for the comparison is the one applied to an assembly of discs by De Josselin de Jong and Verruijt (1969). The force vector diagrams obtained numerically closely resemble those obtained photoelastically. It is concluded from this comparison that the distinct element method and the program BALL are valid tools for research into the behaviour of granular assemblies. La methode des elements distincts est un modele numerique capab...
12,472 citations
TL;DR: The state-of-the-art of additive manufacturing (AM) can be classified into three categories: direct digital manufacturing, free-form fabrication, or 3D printing as discussed by the authors.
Abstract: This paper reviews the state-of-the-art of an important, rapidly emerging, manufacturing technology that is alternatively called additive manufacturing (AM), direct digital manufacturing, free form fabrication, or 3D printing, etc. A broad contextual overview of metallic AM is provided. AM has the potential to revolutionize the global parts manufacturing and logistics landscape. It enables distributed manufacturing and the productions of parts-on-demand while offering the potential to reduce cost, energy consumption, and carbon footprint. This paper explores the material science, processes, and business consideration associated with achieving these performance gains. It is concluded that a paradigm shift is required in order to fully exploit AM potential.
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TL;DR: In this article, the authors deal with methods of measuring the volume, shape, and roundness of sedimentary quartz particles, and propose a method to measure the volume and shape of the particles.
Abstract: The article deals with methods of measuring the volume, shape, and roundness of sedimentary quartz particles.
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