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Jack L. Beuth - One of the best experts on this subject based on the ideXlab platform.
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Using machine learning to identify in-situ Melt Pool signatures indicative of flaw formation in a laser powder bed fusion additive manufacturing process
Additive Manufacturing, 2019Co-Authors: Luke Scime, Jack L. BeuthAbstract:Because many of the most important defects in Laser Powder Bed Fusion (L-PBF) occur at the size and timescales of the Melt Pool itself, the development of methodologies for monitoring the Melt Pool is critical. This works examines the possibility of in-situ detection of keyholing porosity and balling instabilities. Specifically, a visible-light high speed camera with a fixed field of view is used to study the morphology of L-PBF Melt Pools in the Inconel 718 material system. A scale-invariant description of Melt Pool morphology is constructed using Computer Vision techniques and unsupervised Machine Learning is used to differentiate between observed Melt Pools. By observing Melt Pools produced across process space, in-situ signatures are identified which may indicate flaws such as those observed ex-situ. This linkage of ex-situ and in-situ morphology enabled the use of supervised Machine Learning to classify Melt Pools observed (with the high speed camera) during fusion of non-bulk geometries such as overhangs.
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Toward determining Melt Pool quality metrics via coaxial monitoring in laser powder bed fusion
Manufacturing Letters, 2018Co-Authors: Brian A. Fisher, Brandon Lane, Ho Yeung, Jack L. BeuthAbstract:The current industry trend in metal additive manufacturing is towards greater real time process monitoring capabilities during builds to ensure high quality parts. While the hardware implementations that allow for real time monitoring of the Melt Pool have advanced significantly, the knowledge required to correlate the generated data to useful metrics of interest are still lacking. This research presents promising results that aim to bridge this knowledge gap by determining a novel means to correlate easily obtainable sensor data (thermal emission) to key Melt Pool size metrics (e.g., Melt Pool cross sectional area).
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integrated Melt Pool and microstructure control for ti 6al 4v thin wall additive manufacturing
Materials Science and Technology, 2015Co-Authors: Joy Gockel, Jack L. Beuth, Jason Cho Fox, R HafleyAbstract:AbstractIn additive manufacturing (AM), Melt Pool dimension control is needed to accurately build a geometry and determine process precision. Microstructure control is needed for its effect on mechanical properties. This research addresses both for Ti–6Al–4V thin walled structures fabricated by wire feed electron beam AM. Model results show that beam power and beam velocity combinations yielding constant Melt Pool cross-sectional areas also yield constant solidification cooling rates. Experimental measurements back up this finding and show roughly 20 beta grains across the width of a thin wall deposit which is consistent with an earlier study of single bead deposits, suggesting that links between Melt Pool geometry and beta grain size are independent of deposition geometry, with significant implications for AM process control.
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Integrated control of solidification microstructure and Melt Pool dimensions in electron beam wire feed additive manufacturing of ti-6al-4v
2014Co-Authors: Joy Gockel, Jack L. Beuth, Karen M. TamingerAbstract:The ability to deposit a consistent and predictable solidification microstructure can greatly accelerate additive manufacturing (AM) process qualification. Process mapping is an approach that represents process outcomes in terms of process variables. In this work, a solidification microstructure process map was developed using finite element analysis for deposition of single beads of Ti-6Al-4V via electron beam wire feed AM processes. Process variable combinations yielding constant beta grain size and morphology were identified. Comparison with a previously developed process map for Melt Pool geometry shows that maintaining a constant Melt Pool cross sectional area will also yield a constant grain size. Additionally, the grain morphology boundaries are similar to curves of constant Melt Pool aspect ratio. Experimental results support the numerical predictions and identify a proportional size scaling between beta grain widths and Melt Pool widths. Results further demonstrate that in situ indirect control of solidification microstructure is possible through direct Melt Pool dimension control.
Richardson I.m. - One of the best experts on this subject based on the ideXlab platform.
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Numerical study of molten metal Melt Pool behaviour during conduction-mode laser spot Melting
'IOP Publishing', 2021Co-Authors: Ebrahimi Amin, Kleijn C.r., Richardson I.m.Abstract:Molten metal Melt Pools are characterised by highly non-linear responses, which are very sensitive to imposed boundary conditions. Temporal and spatial variations in the energy flux distribution are often neglected in numerical simulations of Melt Pool behaviour. Additionally, thermo-physical properties of materials are commonly changed to achieve agreement between predicted Melt-Pool shape and experimental post-solidification macrograph. Focusing on laser spot Melting in conduction mode, we investigated the influence of dynamically adjusted energy flux distribution and changing thermo-physical material properties on Melt Pool oscillatory behaviour using both deformable and non-deformable assumptions for the gas-metal interface. Our results demonstrate that adjusting the absorbed energy flux affects the oscillatory fluid flow behaviour in the Melt Pool and consequently the predicted Melt-Pool shape and size. We also show that changing the thermo-physical material properties artificially or using a non-deformable surface assumption lead to significant differences in Melt Pool oscillatory behaviour compared to the cases in which these assumptions are not made.MSE-5ChemE/Transport Phenomen
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Numerical study of molten metal Melt Pool behaviour during conduction-mode laser spot Melting
'IOP Publishing', 2021Co-Authors: Ebrahimi Amin, Kleijn C.r., Richardson I.m.Abstract:Molten metal Melt Pools are characterised by highly non-linear responses, which are very sensitive to imposed boundary conditions. Temporal and spatial variations in the energy flux distribution are often neglected in numerical simulations of Melt Pool behaviour. Additionally, thermo-physical properties of materials are commonly changed to achieve agreement between predicted Melt-Pool shape and experimental post-solidification macrograph. Focusing on laser spot Melting in conduction mode, we investigated the influence of dynamically adjusted energy flux distribution and changing thermo-physical material properties on Melt Pool oscillatory behaviour using both deformable and non-deformable assumptions for the gas-metal interface. Our results demonstrate that adjusting the absorbed energy flux affects the oscillatory fluid flow behaviour in the Melt Pool and consequently the predicted Melt-Pool shape and size. We also show that changing the thermo-physical material properties artificially or using a non-deformable surface assumption lead to significant differences in Melt Pool oscillatory behaviour compared to the cases in which these assumptions are not made.Team Marcel HermansChemE/Transport Phenomen
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A simulation-based approach to characterise Melt-Pool oscillations during gas tungsten arc welding
'Elsevier BV', 2021Co-Authors: Ebrahimi Amin, Kleijn C.r., Richardson I.m.Abstract:Development, optimisation and qualification of welding and additive manufacturing procedures to date have largely been undertaken on an experimental trial and error basis, which imposes significant costs. Numerical simulations are acknowledged as a promising alternative to experiments, and can improve the understanding of the complex process behaviour. In the present work, we propose a simulation-based approach to study and characterise molten metal Melt Pool oscillatory behaviour during arc welding. We implement a high-fidelity three-dimensional model based on the finite-volume method that takes into account the effects of surface deformation on arc power-density and force distributions. These factors are often neglected in numerical simulations of welding and additive manufacturing. Utilising this model, we predict complex molten metal flow in Melt Pools and associated Melt-Pool surface oscillations during both steady-current and pulsed-current gas tungsten arc welding (GTAW). An analysis based on a wavelet transform was performed to extract the time-frequency content of the displacement signals obtained from numerical simulations. Our results confirm that the frequency of oscillations for a fully penetrated Melt Pool is lower than that of a partially penetrated Melt Pool with an abrupt change from partial to full penetration. We find that during transition from partial to full penetration state, two dominant frequencies coexist in the time-frequency spectrum. The results demonstrate that Melt-Pool oscillations profoundly depend on Melt-Pool shape and convection in the Melt Pool, which in turn is influenced by process parameters and material properties. The present numerical simulations reveal the unsteady evolution of Melt Pool oscillatory behaviour that are not predictable from published theoretical analyses. Additionally, using the proposed simulation-based approach, the need of triggering the Melt-Pool oscillations is expendable since even small surface displacements are detectable, which are not sensible to the current measurement devices employed in experiments.MSE-5ChemE/Transport Phenomen
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A simulation-based approach to characterise Melt-Pool oscillations during gas tungsten arc welding
'Elsevier BV', 2021Co-Authors: Ebrahimi Amin, Kleijn C.r., Richardson I.m.Abstract:Development, optimisation and qualification of welding and additive manufacturing procedures to date have largely been undertaken on an experimental trial and error basis, which imposes significant costs. Numerical simulations are acknowledged as a promising alternative to experiments, and can improve the understanding of the complex process behaviour. In the present work, we propose a simulation-based approach to study and characterise molten metal Melt Pool oscillatory behaviour during arc welding. We implement a high-fidelity three-dimensional model based on the finite-volume method that takes into account the effects of surface deformation on arc power-density and force distributions. These factors are often neglected in numerical simulations of welding and additive manufacturing. Utilising this model, we predict complex molten metal flow in Melt Pools and associated Melt-Pool surface oscillations during both steady-current and pulsed-current gas tungsten arc welding (GTAW). An analysis based on a wavelet transform was performed to extract the time-frequency content of the displacement signals obtained from numerical simulations. Our results confirm that the frequency of oscillations for a fully penetrated Melt Pool is lower than that of a partially penetrated Melt Pool with an abrupt change from partial to full penetration. We find that during transition from partial to full penetration state, two dominant frequencies coexist in the time-frequency spectrum. The results demonstrate that Melt-Pool oscillations profoundly depend on Melt-Pool shape and convection in the Melt Pool, which in turn is influenced by process parameters and material properties. The present numerical simulations reveal the unsteady evolution of Melt Pool oscillatory behaviour that are not predictable from published theoretical analyses. Additionally, using the proposed simulation-based approach, the need of triggering the Melt-Pool oscillations is expendable since even small surface displacements are detectable, which are not sensible to the current measurement devices employed in experiments.
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The Effects of Process Parameters on Melt-Pool Oscillatory Behaviour in Gas Tungsten Arc Welding
'IOP Publishing', 2021Co-Authors: Ebrahimi Amin, Kleijn C.r., Hermans M.j.m., Richardson I.m.Abstract:Internal flow behaviour and Melt-Pool surface oscillations during arc welding are complex and not yet fully understood. In the present work, high-fidelity numerical simulations are employed to describe the effects of welding position, sulphur concentration (60-300 ppm) and travel speed (1.25-5 mms-1) on molten metal flow dynamics in fully-penetrated Melt-Pools. A wavelet transform is implemented to obtain time-resolved frequency spectra of the oscillation signals, which overcomes the shortcomings of the Fourier transform in rendering time resolution of the frequency spectra. Comparing the results of the present numerical calculations with available analytical and experimental datasets, the robustness of the proposed approach in predicting Melt-Pool oscillations is demonstrated. The results reveal that changes in the surface morphology of the Pool resulting from a change in welding position alter the spatial distribution of arc forces and power-density applied to the molten material, and in turn affect flow patterns in the Pool. Under similar welding conditions, changing the sulphur concentration affects the Marangoni flow pattern, and increasing the travel speed decreases the size of the Pool and increases the offset between top and bottom Melt-Pool surfaces, affecting the flow structures (vortex formation) on the surface. Variations in the internal flow pattern affect the evolution of Melt-Pool shape and its surface oscillations.
J N Dupont - One of the best experts on this subject based on the ideXlab platform.
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effects of substrate crystallographic orientations on crystal growth and microstructure development in laser surface Melted superalloy single crystals mathematical modeling of single crystal growth in a Melt Pool part ii
Acta Materialia, 2005Co-Authors: J N DupontAbstract:Abstract The mathematical model developed for single-crystalline solidification in laser surface Melting (LSM) described in Part I [Acta Mater 2004;52:4833–4847] was used to compute the dendrite growth pattern and velocity distribution in the 3D Melt Pool for various substrate orientations. LSM experiments with single-crystal nickel-base superalloys were conducted for different orientations to verify the computational results. Results show that the substrate orientation has a predominant effect on crystal growth pattern, and simultaneously influences the magnitude and distribution of dendrite growth velocity in the Melt Pool. The selected 〈1 0 0〉 growth variants and the number of the chosen growth variants are dependent on the substrate orientation. The maximum velocity ratio (dendrite growth velocity over the beam velocity, V/Vb) in the Melt Pool is a function of Melt-Pool geometrical parameters and the substrate orientation. The largest maximum velocity-ratio among the symmetric orientations is 1.414 for the (0 0 1)/[1 1 0] and ( 0 1 1 ) / [ 0 1 1 ¯ ] orientations, while that value for asymmetric orientations is 1.732 for the ( 0 1 1 ) / [ 1 1 1 ¯ ] orientation. Good agreement was obtained between the predicted and experimentally observed microstructures. The results are discussed with the susceptibility to stray grain formation as a function of substrate orientations and Melt-Pool geometrical parameters. These findings have some important implications for single-crystal surface processing.
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effects of Melt Pool geometry on crystal growth and microstructure development in laser surface Melted superalloy single crystals mathematical modeling of single crystal growth in a Melt Pool part i
Acta Materialia, 2004Co-Authors: J N DupontAbstract:Abstract The effects of Melt-Pool geometrical parameters on crystal growth and microstructure development during laser surface Melting of single-crystal alloys were studied by means of mathematical modeling and experiments. A mathematical model was developed for the three-dimensional (3-D) Melt-Pool geometry and single-crystalline Melt-Pool solidification in laser surface Melting. The 3-D Melt-Pool geometry corresponding to the solidification interface is described by four geometrical parameters ( w , l , h , α ). The model was used to study the effects of variations in the geometrical parameters on crystal growth and microstructure development in the Melt Pool. Laser surface Melting experiments with single-crystal nickel-base superalloys were conducted to verify the computational results of microstructure development in the Melt Pool. Results indicate that the Melt-Pool geometrical parameters have profound influences on the dendrite growth velocity and growth pattern in the Melt Pool. For the (0 0 1)/[1 0 0] substrate orientation, variations in l / w and α can influence both the number and the relative sizes of growth regions while the variation in h / w can only influence the relative sizes of the growth regions. Unidirectional dendrite growth along the [0 0 1] crystallographic direction can be achieved for an α value of 45° or below. The maximum ratio of dendrite-growth velocity to the beam velocity in the Melt Pool is related to α and l / w . Experimental microstructure observations agreed well with the computational results. These findings show that the desired dendrite growth velocity and microstructure can be obtained through proper control of the 3-D Melt-Pool geometry.
Jack Beuth - One of the best experts on this subject based on the ideXlab platform.
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Melt Pool geometry and microstructure of ti6al4v with b additions processed by selective laser Melting additive manufacturing
Materials & Design, 2019Co-Authors: Colt Montgomery, Jack Beuth, Bryan A WeblerAbstract:Abstract This paper documents an investigation into the microstructures and Melt Pool geometry features of Ti6Al4V + (0, 1, 2, 5, 10, wt%) B alloys processed by selective laser Melting (SLM). Single laser-deposited tracks were made on powder-free surface of arc-Melted Ti6Al4V-xB buttons. The applicability of powder-free results was supported by evaluation of Ti6Al4V Melt Pool geometry deposited with and without powder. For each Ti6Al4V-xB composition, Melt Pools were produced over wide ranges of laser beam power (P) and scan speed (V), with Melt Pool geometry and microstructure information gathered into mapping in P-V space to develop P-V process window. By varying wt% B and P-V parameter, a variety of microstructures were produced. A promising microstructure consisted of a TiB network with submicron spacing. Melt Pool microhardness was characterized, showing evident enhancement from arc-Melted baseline for all Ti6Al4V-xB composition. This work identified Ti6Al4V-xB with 2–5 wt% B as a promising composition range for SLM processing and showed the powder-free methodology can provide Melt Pool scale information for trial alloy composition evaluation.
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Melt Pool geometry and morphology variability for the inconel 718 alloy in a laser powder bed fusion additive manufacturing process
Additive manufacturing, 2019Co-Authors: Luke Scime, Jack BeuthAbstract:Abstract Expanding on prior process mapping work by the authors, multiple Melt Pool cross-sections are measured at multiple process parameter combinations for the Inconel 718 alloy in a Laser Powder Bed Fusion (L-PBF) process. Collection of such data enables the study of the variability of Melt Pool geometry (e.g. width, depth, and cross-sectional area) across process space. Furthermore, the statistical distribution of the measured Melt Pool geometries is compared to that of an equivalent normal distribution and intriguing outliers are observed. The cross-sectional morphology of the Melt Pools are associated with defects such as keyholing porosity and balling and the variability of the defects is quantified. The final product of this work is a robust description of L-PBF In718 Melt Pool behavior, based on ex-situ observations, which can be linked to in-situ observations of Melt Pool morphology in future work.
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process maps for predicting residual stress and Melt Pool size in the laser based fabrication of thin walled structures
Journal of Manufacturing Science and Engineering-transactions of The Asme, 2007Co-Authors: Aditad Vasinonta, Jack Beuth, Michelle L GriffithAbstract:Thermomechanical models are presented for the building of thin-walled structures by laser-based solid freeform fabrication (SFF) processes. Thermal simulations are used to develop quasi-non-dimensional plots (termed process maps) that quantify the effects of changes in wall height, laser power, deposition speed, and part preheating on thermal gradients, with the goal of limiting residual stresses in manufactured components. Mechanical simulations are used to demonstrate the link between thermal gradients and, maximum final residual stresses. The approach taken is analogous to that taken in previous research by the authors in developing process maps for Melt Pool length, for maintaining an optimal Melt Pool size during component fabrication. Process maps are tailored for application to the laser engineered net shaping process; however, the general approach, insights, and conclusions are applicable to most SFF processes involving a moving heat source, and to other laser-based fusion processes. Results from the residual stress simulations identify two mechanisms for reducing residual stresses and quantify maximum stress reductions achievable through manipulation of all process variables. Results from thermal gradient and Melt Pool length process maps are used to identify a manufacturing strategy for obtaining a consistent Melt Pool size while limiting residual stress in a thin-walled part.
Luke Scime - One of the best experts on this subject based on the ideXlab platform.
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Melt Pool geometry and morphology variability for the inconel 718 alloy in a laser powder bed fusion additive manufacturing process
Additive manufacturing, 2019Co-Authors: Luke Scime, Jack BeuthAbstract:Abstract Expanding on prior process mapping work by the authors, multiple Melt Pool cross-sections are measured at multiple process parameter combinations for the Inconel 718 alloy in a Laser Powder Bed Fusion (L-PBF) process. Collection of such data enables the study of the variability of Melt Pool geometry (e.g. width, depth, and cross-sectional area) across process space. Furthermore, the statistical distribution of the measured Melt Pool geometries is compared to that of an equivalent normal distribution and intriguing outliers are observed. The cross-sectional morphology of the Melt Pools are associated with defects such as keyholing porosity and balling and the variability of the defects is quantified. The final product of this work is a robust description of L-PBF In718 Melt Pool behavior, based on ex-situ observations, which can be linked to in-situ observations of Melt Pool morphology in future work.
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Using machine learning to identify in-situ Melt Pool signatures indicative of flaw formation in a laser powder bed fusion additive manufacturing process
Additive Manufacturing, 2019Co-Authors: Luke Scime, Jack L. BeuthAbstract:Because many of the most important defects in Laser Powder Bed Fusion (L-PBF) occur at the size and timescales of the Melt Pool itself, the development of methodologies for monitoring the Melt Pool is critical. This works examines the possibility of in-situ detection of keyholing porosity and balling instabilities. Specifically, a visible-light high speed camera with a fixed field of view is used to study the morphology of L-PBF Melt Pools in the Inconel 718 material system. A scale-invariant description of Melt Pool morphology is constructed using Computer Vision techniques and unsupervised Machine Learning is used to differentiate between observed Melt Pools. By observing Melt Pools produced across process space, in-situ signatures are identified which may indicate flaws such as those observed ex-situ. This linkage of ex-situ and in-situ morphology enabled the use of supervised Machine Learning to classify Melt Pools observed (with the high speed camera) during fusion of non-bulk geometries such as overhangs.
