scholarly journals Modelling of Powder Removal for Additive Manufacture Postprocessing

2021 ◽  
Author(s):  
Andrew Roberts ◽  
Recep Kahraman ◽  
Desi Bacheva ◽  
Gavin Tabor
Keyword(s):  
Complex Geometry ◽  
Selective Laser Sintering ◽  
Computational Cost ◽  
Additive Manufacture ◽  
Granular Temperature ◽  
Multiphase Model ◽  
Metal Powders ◽  
The Individual ◽  
Eulerian Multiphase Model ◽  
Critical Challenge

A critical challenge underpinning the adoption of Additive Manufacture (AM) as a technology is the postprocessing of manufactured components. For Selective Laser Sintering (SLS) this can involve the removal of powder from the interior of the component, often by vibrating the component to fluidise the powder to encourage drainage. In this paper we develop and validate a computational model of the flow of metal powder suitable for predicting powder removal from such AM components. The model is a continuum Eulerian multiphase model of the powder including models for the granular temperature; the effect of vibration can be included through appropriate wall boundaries for this granular temperature. We validate the individual sub-models appropriate for AM metal powders by comparison with in-house and literature experimental results, and then apply the full model to a more complex geometry typical of an AM Heat Exchanger. The model is shown to provide valuable and accurate results at a fraction of the computational cost of a particle-based model.

scholarly journals Modelling of Powder Removal for Additive Manufacture Postprocessing

2021 ◽  
Vol 5 (3) ◽  
pp. 86
Author(s):  
Andrew Roberts  ◽  
Recep Kahraman ◽  
Desi Bacheva ◽  
Gavin Tabor
Keyword(s):  
Complex Geometry ◽  
Computational Cost ◽  
Additive Manufacture ◽  
Granular Temperature ◽  
Multiphase Model ◽  
Metal Powders ◽  
Powder Bed ◽  
The Individual ◽  
Eulerian Multiphase Model ◽  
Critical Challenge

A critical challenge underpinning the adoption of Additive Manufacture (AM) as a technology is the postprocessing of manufactured components. For Powder Bed Fusion (PBF), this can involve the removal of powder from the interior of the component, often by vibrating the component to fluidise the powder to encourage drainage. In this paper, we develop and validate a computational model of the flow of metal powder suitable for predicting powder removal from such AM components. The model is a continuum Eulerian multiphase model of the powder including models for the granular temperature; the effect of vibration can be included through appropriate wall boundaries for this granular temperature. We validate the individual sub-models appropriate for AM metal powders by comparison with in-house and literature experimental results, and then apply the full model to a more complex geometry typical of an AM Heat Exchanger. The model is shown to provide valuable and accurate results at a fraction of the computational cost of a particle-based model.

Evolution of Direct Selective Laser Sintering of Metals

2011 ◽  
Vol 383-390 ◽  
pp. 6252-6257
Author(s):  
Francesco Cardaropoli ◽  
Fabrizia Caiazzo ◽  
Vincenzo Sergi
Keyword(s):  
Complex Geometry ◽  
Selective Laser Sintering ◽  
Laser Sintering ◽  
Layer By Layer ◽  
Metal Powders ◽  
Additive Process ◽  
Operator Experience ◽  
Critical Phases ◽  
Time Required

Direct Metal Selective Laser Sintering (DMSLS) is a layer-by-layer additive process for metal powders, which allows quick production of complex geometry parts. The aim of this study is to analyse the improvement of DMSLS with “EOSINT M270”, the new laser sintering machine developed by EOS. Tests were made on sintered parts of Direct Metal 20 (DM20), a bronze based powder with a mean grain dimension of 20 μm. Different properties and accuracy were evaluated for samples manufactured with three different exposure strategies. Besides mechanical properties, the manufacturing process was also examined in order to evaluate its characteristics. The quality of laser sintered parts is too affected by operator experience and skill. Furthermore, critical phases are not automatic and this causes an extension of time required for the production. Due to these limitations, DMSLS can be used for Rapid Manufacturing, but it is especially suitable to few sample series.

scholarly journals A multiphase model for reinforced concrete structures considering the concrete cracking

2011 ◽  
Vol 4 (2) ◽  
pp. 179-190
Author(s):  
M. P. Figueiredo ◽  
S. Maghous ◽  
A. Campos Filho
Keyword(s):  
Reinforced Concrete ◽  
Computational Cost ◽  
Concrete Structures ◽  
Homogenization Method ◽  
Numerical Code ◽  
Multiphase Model ◽  
Present Contribution ◽  
Concrete Cracking ◽  
Smeared Crack Approach ◽  
The Individual

Assessing the global behavior of reinforced materials from the individual properties of their components has been the subject of a considerable amount of experimental and theoretical works in the last years. The so-called multiphase model is an alternative generalization of the homogenization method and it relies upon the idea that, at the macroscopic scale, the reinforced concrete is a geometrical superposition of the matrix phase (concrete) and the reinforcing phase (steel bars). This technique was already successfully employed in several geotechnical structures. Considering the particular case of concrete structures, Figueiredo et al [1] analyzed the mechanical behavior of reinforced concrete flat slabs under prescribed loading using the multiphase model in elastoplasticity. The present contribution extents a previously numerical code to account for concrete cracking based on a smeared crack approach. Comparison with direct simulation results emphasizes the advantage of such multiphase model in terms of reduced computational cost.

Two-Phase Computational Modelling of a Spiral Bevel Gear Using a Eulerian Multiphase Model

2015 ◽  
Author(s):  
Baydu C. Al ◽  
Kathy Simmons ◽  
Hervé P. Morvan
Keyword(s):  
Computational Cost ◽  
Computational Modelling ◽  
Bevel Gear ◽  
Spiral Bevel Gear ◽  
Multiphase Model ◽  
Transmission Systems ◽  
Two Phase ◽  
Film Model ◽  
Spiral Bevel ◽  
Eulerian Multiphase Model

The efficiency of power transmission systems is increasingly targeted with a view to reducing parasitic losses and improving specific fuel consumption (SFC). One of the effects associated with such parasitic losses is gear windage power loss and this mechanism can be a significant contributor to overall heat-to-oil within large civil aeroengines. The University of Nottingham Technology Centre in Gas Turbine Transmission Systems has been conducting experimental and computational research into spiral bevel gear windage applicable to an aeroengine internal gearbox (IGB). The two-phase flows related to gear lubrication, shrouding and scavenging are complex. Good understanding of such flows can be used to balance lubrication needs with need to minimise oil volumes and parasitic losses. Previous computational investigations have primarily employed discrete phase modelling (DPM) to predict oil behaviour under the shroud [1, 2]. In this paper modelling capability has been investigated and extended through application of FLUENT’s Eulerian multiphase model. In addition, DPM modelling linked to FLUENT’s Lagrangian film model has been conducted. A control volume with periodic symmetry comprising a single tooth passage of the bevel gear has been modelled to keep the computational cost down.The results from both models are compared to each other and to available experimental visual data. Both models are found to perform acceptably with the Eulerian multiphase model yielding results closer to those observed experimentally. The use of DPM with a Eulerian film model is suggested for future work and extension to a full 360° model is recommended.

A Numerical Approach for the Simulation of Internal Nozzle Flow in a Pressure Swirl Atomizer Using Different Turbulent Models and Towards an Effective Inlet Weber Number

2013 ◽  
Author(s):  
Ahmadreza Abbasi Baharanchi ◽  
Seckin Gokaltun ◽  
Shahla Eshraghi
Keyword(s):  
Weber Number ◽  
Computational Cost ◽  
Internal Flow ◽  
Numerical Approach ◽  
Reynolds Stress Model ◽  
Multiphase Model ◽  
Vof Model ◽  
Swirl Atomizer ◽  
Pressure Swirl ◽  
Pressure Swirl Atomizer

VOF Multiphase model is used to simulate the flow inside a pressure-swirl-atomizer. The capability of the Reynolds Stress Model and variants of the K-ε and K-ω models in modeling of turbulence has been investigated in the commercial computational fluid dynamics (CFD) software FLUENT 6.3. The Implicit scheme available in the volume-of-fluid (VOF) model is used to calculate the interface representation between phases. The atomization characteristics have been investigated as well as the influence of the inlet swirl strength of the internal flow. The numerical results have been successfully validated against experimental data available for the computed parameters. The performance of the RNG K-ε model was found to be satisfactory in reducing the computational cost and introducing an effective Weber number for the flow simulated in this study.

A Novel Turbulent Aggregation Device for Flue Gas

2014 ◽  
Vol 955-959 ◽  
pp. 2425-2429 ◽  
Author(s):  
Yun Fei Li ◽  
Jian Guo Yang ◽  
Yan Yan Wang ◽  
Xiao Guo Wang
Keyword(s):  
Size Distribution ◽  
Flue Gas ◽  
Large Scale ◽  
Balance Model ◽  
Small Scale ◽  
Multiphase Model ◽  
Specific Performance ◽  
Particles Size Distribution ◽  
Scale Turbulence ◽  
Eulerian Multiphase Model

The purpose of this study is to construct a turbulent aggregation device which has specific performance for fine particle aggregation in flue gas. The device consists of two cylindrical pipes and an array of vanes. The pipes extending fully and normal to the gas stream induce large scale turbulence in the form of vortices, while the vanes downstream a certain distance from the pipes induce small one. The process of turbulent aggregation was numerically simulated by coupling the Eulerian multiphase model and population balance model together with a proposed aggregation kernel function taking the size and inertia of particles into account, and based on data of particles’ size distribution measured from the flue of one power plant. The results show that the large scale turbulence generated by pipes favours the aggregation of smaller particles (smaller than 1μm) notably, while the small scale turbulence benefits the aggregation of bigger particles (larger than 1μm) notably and enhances the uniformity of particle size distribution among different particle groups.

scholarly journals A consensus-based global optimization method for high dimensional machine learning problems

2020 ◽  
Author(s):  
Jose Carrillo ◽  
Shi Jin ◽  
Lei Li ◽  
Yuhua Zhu
Keyword(s):  
Optimization Problems ◽  
Computational Cost ◽  
Weighted Average ◽  
Planck Equation ◽  
Optimization Method ◽  
Learning Problems ◽  
High Dimensional ◽  
Nonconvex Functions ◽  
The Individual ◽  
Parameter Constraints

We improve recently introduced consensus-based optimization method, proposed in [R. Pinnau, C. Totzeck, O. Tse and S. Martin, Math. Models Methods Appl. Sci., 27(01):183{204, 2017], which is a gradient-free optimization method for general nonconvex functions. We rst replace the isotropic geometric Brownian motion by the component-wise one, thus removing the dimensionality dependence of the drift rate, making the method more competitive for high dimensional optimization problems. Secondly, we utilize the random mini-batch ideas to reduce the computational cost of calculating the weighted average which the individual particles tend to relax toward. For its mean- eld limit{a nonlinear Fokker-Planck equation{we prove, in both time continuous and semi-discrete settings, that the convergence of the method, which is exponential in time, is guaranteed with parameter constraints independent of the dimensionality. We also conduct numerical tests to high dimensional problems to check the success rate of the method.

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