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Mihaela Vlasea
Department of Mechanical & Mechatronics Engineering, University of Waterloo, Waterloo, ON N2L 3G1, Canada

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Journal article
Published: 16 August 2021 in Materials
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A path to lowering the economic barrier associated with the high cost of metal additively manufactured components is to reduce the waste via powder reuse (powder cycled back into the process) and recycling (powder chemically, physically, or thermally processed to recover the original properties) strategies. In electron beam powder bed fusion, there is a possibility of reusing 95–98% of the powder that is not melted. However, there is a lack of systematic studies focusing on quantifying the variation of powder properties induced by number of reuse cycles. This work compares the influence of multiple reuse cycles, as well as powder blends created from reused powder, on various powder characteristics such as the morphology, size distribution, flow properties, packing properties, and chemical composition (oxygen and nitrogen content). It was found that there is an increase in measured response in powder size distribution, tapped density, Hausner ratio, Carr index, basic flow energy, specific energy, dynamic angle of repose, oxygen, and nitrogen content, while the bulk density remained largely unchanged.

ACS Style

Gitanjali Shanbhag; Mihaela Vlasea. Powder Reuse Cycles in Electron Beam Powder Bed Fusion—Variation of Powder Characteristics. Materials 2021, 14, 4602 .

AMA Style

Gitanjali Shanbhag, Mihaela Vlasea. Powder Reuse Cycles in Electron Beam Powder Bed Fusion—Variation of Powder Characteristics. Materials. 2021; 14 (16):4602.

Chicago/Turabian Style

Gitanjali Shanbhag; Mihaela Vlasea. 2021. "Powder Reuse Cycles in Electron Beam Powder Bed Fusion—Variation of Powder Characteristics." Materials 14, no. 16: 4602.

Journal article
Published: 14 July 2021 in CIRP Journal of Manufacturing Science and Technology
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Metal additive manufacturing (AM) processes have transitioned from rapid prototyping applications to industrial adoption owing to their flexibility in product design, tooling, and process planning. Directed energy deposition (DED) is one of the most commonly used metal AM processes capable of producing large, high density parts, with a controlled microstructure. However, there are still ongoing challenges in maintaining a high level of reliability and repeatability when compared to conventional manufacturing processes. There is a need to define, identify and maintain regions of process stability in DED. In this study, a high-dynamic range camera and a physics-based model are used to monitor the melt pool, obtain process signatures, and predict deposition stability characteristics. The research efforts are focused on generating process maps to identify unstable process zones, with a reference to process physics, process signatures, and process outcomes using analytical modeling, in-situ melt pool monitoring, and ex-situ characterization, respectively. The goal is to classify the process signatures in pre-defined process zones (under-melt, conduction, keyhole, balling) to avoid instabilities, defects and anomalies using a low-cost high-dynamic range camera and kNN classifier, which has achieved 13% error rate. With this approach, decisions can be made to perform corrective actions (e.g. machining, re-manufacturing) or to scrap the manufactured part without ex-situ characterization.

ACS Style

Deniz Sera Ertay; Mohamed A. Naiel; Mihaela Vlasea; Paul Fieguth. Process performance evaluation and classification via in-situ melt pool monitoring in directed energy deposition. CIRP Journal of Manufacturing Science and Technology 2021, 35, 298 -314.

AMA Style

Deniz Sera Ertay, Mohamed A. Naiel, Mihaela Vlasea, Paul Fieguth. Process performance evaluation and classification via in-situ melt pool monitoring in directed energy deposition. CIRP Journal of Manufacturing Science and Technology. 2021; 35 ():298-314.

Chicago/Turabian Style

Deniz Sera Ertay; Mohamed A. Naiel; Mihaela Vlasea; Paul Fieguth. 2021. "Process performance evaluation and classification via in-situ melt pool monitoring in directed energy deposition." CIRP Journal of Manufacturing Science and Technology 35, no. : 298-314.

Article
Published: 29 June 2021 in Journal of Materials Engineering and Performance
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The use of metal additive manufacturing (AM) technologies is growing rapidly in many industries owing to their ability to produce complex designs, to light-weight critical components, and to consolidate assemblies. Laser powder bed fusion (LPBF) is a metal AM technology that offers finer feature resolution when compared with other metal AM technologies, with ongoing challenges in controlling the process to guarantee defect-free parts. Manufacturing of end-use products via LPBF with a high degree of internal feature design complexity results in an increased demand for demonstrating the performance of various nondestructive evaluation (NDE) tools. In this work, the use of high-frequency (50 MHz) phased array ultrasonic testing (PAUT) for the nondestructive evaluation of a cubic AlSi10Mg sample manufactured by the LPBF process is demonstrated. Artificial internal features with various sizes and shapes are implanted into this sample. The sample is tested offline by high-frequency PAUT from different directions and the position and shape of defects are evaluated. The sample is then subjected to X-ray computed tomography (XCT) and the results are compared with those obtained by ultrasonic testing. Very good agreement is observed between PAUT and XCT results and defects with dimensions as small as 0.75 mm are successfully identified.

ACS Style

Farhang Honarvar; Sagar Patel; Mihaela Vlasea; Hossein Amini; Ahmad Varvani-Farahani. Nondestructive Characterization of Laser Powder Bed Fusion Components Using High-Frequency Phased Array Ultrasonic Testing. Journal of Materials Engineering and Performance 2021, 1 -11.

AMA Style

Farhang Honarvar, Sagar Patel, Mihaela Vlasea, Hossein Amini, Ahmad Varvani-Farahani. Nondestructive Characterization of Laser Powder Bed Fusion Components Using High-Frequency Phased Array Ultrasonic Testing. Journal of Materials Engineering and Performance. 2021; ():1-11.

Chicago/Turabian Style

Farhang Honarvar; Sagar Patel; Mihaela Vlasea; Hossein Amini; Ahmad Varvani-Farahani. 2021. "Nondestructive Characterization of Laser Powder Bed Fusion Components Using High-Frequency Phased Array Ultrasonic Testing." Journal of Materials Engineering and Performance , no. : 1-11.

Journal article
Published: 14 June 2021 in Journal of Manufacturing Science and Engineering
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This study focuses on developing and demonstrating a straightforward workflow for identifying pathways to increase green part density in binder jetting additive manufacturing (BJAM) using statistically driven process maps. The workflow was applied to investigate the effects of process parameters toward improving green part density, with a direct application in manufacturing of Fe-Si components. Specifically, a half-factorial experimental design was used to study the effects of four key parameters—layer thickness, powder spreading speed, roller rotational speed, and binder saturation—on Fe-Si spherical powder with D50 of 32.40 µm. Relative bulk density was estimated via three methods: geometrical and mass measurements, the Archimedes test, and CT imaging. The study discusses relative bulk density as well as localized density variation in the printed parts, which is attributed to both parameter selection and inherent process variability. A regression analysis was used to reveal the significance of main effects and second-order interactions. The regression model (R2 = 0.915) was used to derive an expression for green density as a function of the parameters and had a prediction error of 0.96%. Based on the regression model, an optimized set of parameters was obtained that would maximize green density up to 57.96% for the machine and material system.

ACS Style

Issa Rishmawi; Mihaela Vlasea. Binder Jetting of Silicon Steel, Part I: Process Map of Green Density. Journal of Manufacturing Science and Engineering 2021, 143, 1 -19.

AMA Style

Issa Rishmawi, Mihaela Vlasea. Binder Jetting of Silicon Steel, Part I: Process Map of Green Density. Journal of Manufacturing Science and Engineering. 2021; 143 (11):1-19.

Chicago/Turabian Style

Issa Rishmawi; Mihaela Vlasea. 2021. "Binder Jetting of Silicon Steel, Part I: Process Map of Green Density." Journal of Manufacturing Science and Engineering 143, no. 11: 1-19.

Review
Published: 23 April 2021 in Applied Sciences
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Cellular structures (CSs) have been used extensively in recent years, as they offer a unique range of design freedoms. They can be deployed to create parts that can be lightweight by introducing controlled porous features, while still retaining or improving their mechanical, thermal, or even vibrational properties. Recent advancements in additive manufacturing (AM) technologies have helped to increase the feasibility and adoption of cellular structures. The layer-by-layer manufacturing approach offered by AM is ideal for fabricating CSs, with the cost of such parts being largely independent of complexity. There is a growing body of literature concerning CSs made via AM; this presents an opportunity to review the state-of-the-art in this domain and to showcase opportunities in design and manufacturing. This review will propose a novel way of classifying cellular structures by isolating their Geometrical Degrees of Freedom (GDoFs) and will explore the recent innovations in additively manufactured CSs. Based on the present work, the design inputs that are common in CSs generation will be highlighted. Furthermore, the work explores examples of how design inputs have been used to drive the design domain through various case studies. Finally, the review will highlight the manufacturability limitations of CSs in AM.

ACS Style

Ken Nsiempba; Marc Wang; Mihaela Vlasea. Geometrical Degrees of Freedom for Cellular Structures Generation: A New Classification Paradigm. Applied Sciences 2021, 11, 3845 .

AMA Style

Ken Nsiempba, Marc Wang, Mihaela Vlasea. Geometrical Degrees of Freedom for Cellular Structures Generation: A New Classification Paradigm. Applied Sciences. 2021; 11 (9):3845.

Chicago/Turabian Style

Ken Nsiempba; Marc Wang; Mihaela Vlasea. 2021. "Geometrical Degrees of Freedom for Cellular Structures Generation: A New Classification Paradigm." Applied Sciences 11, no. 9: 3845.

Journal article
Published: 26 March 2021 in Journal of Manufacturing Science and Engineering
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Achieving defect-free parts is traditionally challenging in laser powder bed fusion (LPBF). The mechanical properties of additively manufactured parts are highly affected by their density; as such, research in defect detection and pore prediction has gained significant interest. The process parameters, the powder characteristics, and the process environment conditions play an important role in defect occurrence. Moreover, the laser scan path affects density, especially at scan path discontinuities. In this work, the complex interaction between the process parameters and the scan path on the occurrence of subsurface pores is investigated. In the data preparation step, a synthetic data set is generated to model the melt pool morphology along the scan path. A secondary data set containing the pore space of the resulting parts is obtained via X-ray computed tomography (CT) and is registered with the synthetic data set. Machine learning models, namely, a Conditional Variational AutoEncoder (CVAE) and a Convolutional Neural Network (CNN), are then trained based on the input features to predict pore occurrence. The performance evaluation of both CNN and CVAE models on synthetic data indicates that the scan path and process parameters can be utilized in predicting pore locations. Quantitative results show that employing offline CT images a priori in training the CVAE, without the need to have CT information in the test phase, leads the CVAE model to superior performance over the CNN.

ACS Style

Deniz Sera Ertay; Shima Kamyab; Mihaela Vlasea; Zohreh S Azimifar; Thanh Ma; Allan D. Rogalsky; Paul Fieguth. Toward Sub-Surface Pore Prediction Capabilities for Laser Powder Bed Fusion Using Data Science. Journal of Manufacturing Science and Engineering 2021, 143, 1 -40.

AMA Style

Deniz Sera Ertay, Shima Kamyab, Mihaela Vlasea, Zohreh S Azimifar, Thanh Ma, Allan D. Rogalsky, Paul Fieguth. Toward Sub-Surface Pore Prediction Capabilities for Laser Powder Bed Fusion Using Data Science. Journal of Manufacturing Science and Engineering. 2021; 143 (7):1-40.

Chicago/Turabian Style

Deniz Sera Ertay; Shima Kamyab; Mihaela Vlasea; Zohreh S Azimifar; Thanh Ma; Allan D. Rogalsky; Paul Fieguth. 2021. "Toward Sub-Surface Pore Prediction Capabilities for Laser Powder Bed Fusion Using Data Science." Journal of Manufacturing Science and Engineering 143, no. 7: 1-40.

Article
Published: 04 January 2021 in Journal of Materials Engineering and Performance
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Laser power bed fusion (LPBF) enables the possibility to improve the performance of critical automotive components by leveraging new design and manufacturing potentials. While the LPBF approach taps into numerous design freedom advantages, the finely focused energy input source, layer-wise thermal cycling, and rapid cooling rates also impact the properties of a given material, thereby affecting performance characteristics of the end-product. The microstructure and mechanical properties of LPBF components must hence be thoroughly compared with the traditional processing technique used for a given application to evaluate its feasibility. In the context of this work, AlSi10Mg processed via LPBF is compared to a high-pressure die-cast aluminum alloy to compare the performance toward technology adoption in manufacturing automotive transmissions. It was found that, with proper process control, LPBF parts can achieve better or comparable density of 99.84–99.95% (cast: 99.15–99.97% cast), similar surface topography, comparable hardness of 54.3–69.3 HRB (cast: 72.8–81.5 HRB), comparable specific wear rates of 3.92*10−4 to 6.04*10−4 mm3N−1m−1 (cast: 2.50*10−4 to 2.55*10−4 mm3N−1m−1), and an overall better corrosion resistance compared to the cast pump housing. The findings show that, with an appropriate selection of process parameters, it is feasible to pursue and possibly enhance the performance of AlSi10Mg for fluid power applications using LPBF.

ACS Style

Lisa Brock; Ibrahim Ogunsanya; Hamed Asgari; Sagar Patel; Mihaela Vlasea. Relative Performance of Additively Manufactured and Cast Aluminum Alloys. Journal of Materials Engineering and Performance 2021, 30, 760 -782.

AMA Style

Lisa Brock, Ibrahim Ogunsanya, Hamed Asgari, Sagar Patel, Mihaela Vlasea. Relative Performance of Additively Manufactured and Cast Aluminum Alloys. Journal of Materials Engineering and Performance. 2021; 30 (1):760-782.

Chicago/Turabian Style

Lisa Brock; Ibrahim Ogunsanya; Hamed Asgari; Sagar Patel; Mihaela Vlasea. 2021. "Relative Performance of Additively Manufactured and Cast Aluminum Alloys." Journal of Materials Engineering and Performance 30, no. 1: 760-782.

Short communication
Published: 28 July 2020 in Manufacturing Letters
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Electron beam powder bed fusion can offer advantages in terms of powder reuse by virtue of larger layer thickness and flexible recoater, thus lowering the economic barrier by reducing material waste. Systematic studies focused on quantifying the effect of reuse on powder performance metrics such as size, rheometry and flowability remain scarce. This work presents results on the influence of the process on Ti-6Al-4V powder, by comparing virgin powder to reused powders over two processing cycles, benchmarking the most sensitive powder characteristics. Particle size, flow properties and rheometry are compared. It was observed that morphology, size distribution, flowability and spreadability were degraded due to partial sintering and powder recovery.

ACS Style

Gitanjali Shanbhag; Mihaela Vlasea. The effect of reuse cycles on Ti-6Al-4V powder properties processed by electron beam powder bed fusion. Manufacturing Letters 2020, 25, 60 -63.

AMA Style

Gitanjali Shanbhag, Mihaela Vlasea. The effect of reuse cycles on Ti-6Al-4V powder properties processed by electron beam powder bed fusion. Manufacturing Letters. 2020; 25 ():60-63.

Chicago/Turabian Style

Gitanjali Shanbhag; Mihaela Vlasea. 2020. "The effect of reuse cycles on Ti-6Al-4V powder properties processed by electron beam powder bed fusion." Manufacturing Letters 25, no. : 60-63.

Journal article
Published: 22 July 2020 in Additive Manufacturing
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In-situ vision data acquisition, feature extraction, and analysis are ongoing challenges for quality assessment in directed energy deposition (DED). This work proposes a method for detecting target regions in the laser-material interaction zone based on a low-cost high-dynamic-range (HDR) vision sensor. Adaptive image thresholding, connected component analysis, and iterative energy minimization are used to identify target regions. The method is designed to be adaptive, in terms of obtaining parameters based on simple training data, and robust, in terms of feature detection performance subject to under-melt, conduction and keyhole melting mode phenomena. The performance of the proposed region detection scheme is quantitatively and qualitatively evaluated against annotated data. It was found that the True Positive Rate in detection was above 90%, while the False Detection Rate was less than 10%. Extensive experimental results show that the proposed scheme is able to detect and follow target regions under a variety of power levels and process conditions.

ACS Style

Mohamed A. Naiel; Deniz Sera Ertay; Mihaela Vlasea; Paul Fieguth. Adaptive vision-based detection of laser-material interaction for directed energy deposition. Additive Manufacturing 2020, 36, 101468 .

AMA Style

Mohamed A. Naiel, Deniz Sera Ertay, Mihaela Vlasea, Paul Fieguth. Adaptive vision-based detection of laser-material interaction for directed energy deposition. Additive Manufacturing. 2020; 36 ():101468.

Chicago/Turabian Style

Mohamed A. Naiel; Deniz Sera Ertay; Mihaela Vlasea; Paul Fieguth. 2020. "Adaptive vision-based detection of laser-material interaction for directed energy deposition." Additive Manufacturing 36, no. : 101468.

Journal article
Published: 03 June 2020 in Journal of Materials Research
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Additively manufactured parts produced via laser powder bed fusion (LPBF) have limitations in their applications due to post-processing requirements caused by high surface roughness. The characteristics of side-skin surfaces are generally assumed to be dominated by adhered powder particles. This work aims to analyze and interpret the effects of LPBF processing parameters on side-skin surfaces. As such, this work has two sections to investigate the effect of (i) core and (ii) border LPBF parameters on side-skin surface roughness for Ti–6Al–4V. The findings show that there is a robust correlation between both core and border LPBF parameters on side-skin surface morphologies. In terms of core LPBF parameters, an interaction between laser power and beam velocity is shown to influence side-skin surface roughness, resulting in S a values in the range of 11–26 μm. Additionally, a preliminary investigation into the effect of melting mode phenomena at the border leads to a possibility of obtaining S a values of

ACS Style

Sagar Patel; Allan Rogalsky; Mihaela Vlasea. Towards understanding side-skin surface characteristics in laser powder bed fusion. Journal of Materials Research 2020, 35, 2055 -2064.

AMA Style

Sagar Patel, Allan Rogalsky, Mihaela Vlasea. Towards understanding side-skin surface characteristics in laser powder bed fusion. Journal of Materials Research. 2020; 35 (15):2055-2064.

Chicago/Turabian Style

Sagar Patel; Allan Rogalsky; Mihaela Vlasea. 2020. "Towards understanding side-skin surface characteristics in laser powder bed fusion." Journal of Materials Research 35, no. 15: 2055-2064.

Journal article
Published: 02 June 2020 in Journal of Manufacturing Science and Engineering
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The master sinter curve (MSC) is an empirical model used to predict the density of a part after being sintered. The model is typically applied to components that undergo isotropic shrinkage. Parts manufactured using binder jetting additive manufacturing (BJAM) are known to have nonuniform powder systems and high levels of anisotropy. This work explores the application of the master sinter curve to components made by BJAM. Cylindrical samples were manufactured with the long axis parallel (vertical), perpendicular (horizontal), and 45 deg to the printing direction. A bimodal blend of titanium powder (0–45 µm and 106–150 µm) was used to make samples with consistent green densities (ranging from 47.2% to 52.3%) between the different orientations. Samples were then sintered at heating rates of 1, 3, and 5 °C/min to a maximum of 1400 °C. After sintering, the samples showed significant variation between the different orientations, with vertical samples on average 7.6 ± 2.98% and 4.7 ± 1.20% denser than the horizontal and the 45 deg samples, respectively. The calculated apparent activation energies for sintering were within the same range for all orientations, 200–260 kJ/mol for vertical and 45 deg, and 140–260 kJ/mol for horizontal samples. Validation sinter runs showed that the density prediction errors of the master sinter curves were between 0.9% and 4.3%. This work shows that the master sinter curve can be applied to predict the sintered density of components manufactured by binder jetting additive manufacturing.

ACS Style

Evan Wheat; Gitanjali Shanbhag; Mihaela Vlasea. The Master Sinter Curve and Its Application to Binder Jetting Additive Manufacturing. Journal of Manufacturing Science and Engineering 2020, 142, 1 -37.

AMA Style

Evan Wheat, Gitanjali Shanbhag, Mihaela Vlasea. The Master Sinter Curve and Its Application to Binder Jetting Additive Manufacturing. Journal of Manufacturing Science and Engineering. 2020; 142 (10):1-37.

Chicago/Turabian Style

Evan Wheat; Gitanjali Shanbhag; Mihaela Vlasea. 2020. "The Master Sinter Curve and Its Application to Binder Jetting Additive Manufacturing." Journal of Manufacturing Science and Engineering 142, no. 10: 1-37.

Journal article
Published: 11 May 2020 in Additive Manufacturing
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Directed energy deposition (DED) is a metal additive manufacturing process, where dimensional accuracy and repeatability are traditionally challenging to achieve. Strategies for computationally inexpensive process modelling and fast-response process controls of the laser deposition process are necessary to keep the geometric features close to the required dimensional tolerances. The deposition geometry depends highly on the complex local laser-material interaction and global thermal history of the substrate. In order to control the deposition geometry, an accurate and computationally inexpensive discretized state space thermal history model coupled with an analytical deposition geometry model is developed in this work. The model accounts for the local laser-material interaction using the mass and energy equilibrium equations coupled in a lumped parameter solution, as well as the global thermal history of the product using a state space thermomechanical discretization. In literature, studies have only focused on 1D toolpaths with constant process parameters such as speed, powder feedrate, and laser power. As it is possible to achieve highly complex geometric shapes with additive manufacturing, it is important to have models compatible with 2D/3D complex toolpaths. In this paper, an analytical thermomechanical model and a coupled deposition geometry model for DED process are presented and experimentally validated. As such, the thermal history of the deposited part is predicted throughout the process and the geometric features are predicted for 2D toolpaths.

ACS Style

Deniz Sera Ertay; Mihaela Vlasea; Kaan Erkorkmaz. Thermomechanical and geometry model for directed energy deposition with 2D/3D toolpaths. Additive Manufacturing 2020, 35, 101294 .

AMA Style

Deniz Sera Ertay, Mihaela Vlasea, Kaan Erkorkmaz. Thermomechanical and geometry model for directed energy deposition with 2D/3D toolpaths. Additive Manufacturing. 2020; 35 ():101294.

Chicago/Turabian Style

Deniz Sera Ertay; Mihaela Vlasea; Kaan Erkorkmaz. 2020. "Thermomechanical and geometry model for directed energy deposition with 2D/3D toolpaths." Additive Manufacturing 35, no. : 101294.

Research article
Published: 12 January 2020 in Materialia
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Depending on processing conditions, laser powder bed fusion (LPBF) is known to have two operational regimes – conduction mode and keyhole mode. Heat conduction is the dominant heat transfer mechanism for conduction mode melting, whereas heat convection is the dominant heat transfer mechanism for keyhole mode melting. In addition, there exists a transition mode, which lies between the conduction and keyhole mode, wherein the dominance of conduction or convection depends upon the processing conditions. In this work, normalized processing diagrams are obtained to visualize the three melting modes - conduction mode, transition mode, and keyhole mode. The normalized processing diagrams obtained from this work are shown to be independent of material for specific classes of materials, of LPBF system, of laser modulation, and of powder layer thickness. Additionally, an analytical model is proposed to robustly predict the threshold between the three melting modes for two different classes of materials, (i) materials with low reflectivity and low thermal conductivity such as titanium, ferrous, and nickel alloys, and (ii) materials with high reflectivity and high thermal conductivity such as aluminium alloys. The normalized processing diagrams, alongside the identified melting mode thresholds, can provide a useful tool in diagnosing the origins of porous defects and enable accelerated process optimization efforts towards tailoring material properties in LPBF.

ACS Style

Sagar Patel; Mihaela Vlasea. Melting modes in laser powder bed fusion. Materialia 2020, 9, 100591 .

AMA Style

Sagar Patel, Mihaela Vlasea. Melting modes in laser powder bed fusion. Materialia. 2020; 9 ():100591.

Chicago/Turabian Style

Sagar Patel; Mihaela Vlasea. 2020. "Melting modes in laser powder bed fusion." Materialia 9, no. : 100591.

Journal article
Published: 09 October 2018 in Additive Manufacturing
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Binder jetting additive manufacturing (BJAM) is a comparatively low-cost process that enables manufacturing of complex and customizable metal parts. This process is applied to low-cost water-atomized iron powder with the goal of understanding the effects of printing parameters and sintering schedule on maximizing the green and sintered densities of manufactured samples respectively. The powder is characterized by using scanning electron microscopy (SEM) and particle size analysis (Camsizer X2). In the AM process, the effects of powder compaction, layer thickness and liquid binder level on green part density are investigated. Post-process heat treatment is applied to select samples, and suitable debinding parameters are studied by using thermo-gravimetric analysis (TGA). Sintering at various temperatures and durations results in densities of up to 91.3%. Image processing of x-ray computed tomography (μCT) scans of the samples reveals that porosity distribution is affected by powder spreading, and gradients in pore distribution in the sample are largely reduced after sintering. The resulting shrinkage ranges between 6.7 ± 3.0% and 25.3 ± 2.8%, while surface roughness ranges between 11.6 ± 5.0 μm and 32.1 ± 3.4 μm. The results indicate that the sintering temperature and time might be tailored to achieve target densities anywhere in the range of 64% and 91%, with possibly higher densities by increasing sintering time.

ACS Style

Issa Rishmawi; Mehrnaz Salarian; Mihaela Vlasea. Tailoring green and sintered density of pure iron parts using binder jetting additive manufacturing. Additive Manufacturing 2018, 24, 508 -520.

AMA Style

Issa Rishmawi, Mehrnaz Salarian, Mihaela Vlasea. Tailoring green and sintered density of pure iron parts using binder jetting additive manufacturing. Additive Manufacturing. 2018; 24 ():508-520.

Chicago/Turabian Style

Issa Rishmawi; Mehrnaz Salarian; Mihaela Vlasea. 2018. "Tailoring green and sintered density of pure iron parts using binder jetting additive manufacturing." Additive Manufacturing 24, no. : 508-520.

Journal article
Published: 01 October 2018 in Materials & Design
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To facilitate functional part production in metal binder jetting additive manufacturing, the relationship between materials, process and sintering needs to be understood. This work relates sintering theory with process outcomes. For this, commercially pure titanium was deployed to study the effect of powder size distributions on green and sintered part qualities (bulk density, relative density, particle size, pore size, sinter neck size). The powders were uni- and bi-modal blends of 0–45 μm, 45–106 μm, and 106–150 μm. Computed tomography analysis was used to evaluate non-densifying (1000 °C) and densifying (1400 °C) sintering regimes. For green parts, the relative density and powder size distribution along the build direction followed a periodic fluctuation equivalent to the 150 μm layer thickness. The relative density fluctuation range was higher (±20%) for bi-modal blends with 0–45 μm, compared to all other blends (±8%) due to powder segregation. For non-densifying sintering, parts with 0–45 μm blends displayed both densifying and non-densifying behavior. For densifying sintering, powders containing 0–45 μm blends surpassed the 70% density threshold expected for this sintering regime. Overall, the finer particles improved bulk density of sintered parts, at the expense of higher levels of shrinkage and density anisotropy along the build direction.

ACS Style

Evan Wheat; Mihaela Vlasea; James Hinebaugh; Craig Metcalfe. Sinter structure analysis of titanium structures fabricated via binder jetting additive manufacturing. Materials & Design 2018, 156, 167 -183.

AMA Style

Evan Wheat, Mihaela Vlasea, James Hinebaugh, Craig Metcalfe. Sinter structure analysis of titanium structures fabricated via binder jetting additive manufacturing. Materials & Design. 2018; 156 ():167-183.

Chicago/Turabian Style

Evan Wheat; Mihaela Vlasea; James Hinebaugh; Craig Metcalfe. 2018. "Sinter structure analysis of titanium structures fabricated via binder jetting additive manufacturing." Materials & Design 156, no. : 167-183.

Journal article
Published: 01 October 2018 in Materials & Design
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Experimental studies in the literature have identified the powder-bed compaction density as an important parameter, governing the quality of additively manufactured parts. For example, in laser powder-bed fusion (LPBF), the powder-bed compaction density directly affects the effective powder thermal conductivity and consequently the temperature distribution in melt pool. In this study, this physical parameter in a LPBF build compartment is measured using a new methodology. A UV curable polymer is used to bind powder-bed particles at various locations on the powder-bed compartment when Hastelloy X was used. The samples are then scanned using a nano-computing tomography (CT) system at high resolution to obtain an estimation of the relative powder-bed compaction density. It is concluded that due to the interaction between the recoater and the variation in the powder volume accumulated ahead of the recoater across the build compartment, the relative powder-bed compaction density decreases along the recoater moving direction (from 66.4% to 52.4%.). This variation in the powder-bed compaction density affects the density and surface roughness of the final printed parts that is also investigated. Results show that the part density and surface quality decrease ~0.25% and ~20%, respectively, along the build bed in direction of the recoater motion.

ACS Style

Usman Ali; Yahya Mahmoodkhani; Shahriar Imani Shahabad; Reza Esmaeilizadeh; Farzad Liravi; Esmat Sheydaeian; Ke Yin Huang; Ehsan Marzbanrad; Mihaela Vlasea; Ehsan Toyserkani. On the measurement of relative powder-bed compaction density in powder-bed additive manufacturing processes. Materials & Design 2018, 155, 495 -501.

AMA Style

Usman Ali, Yahya Mahmoodkhani, Shahriar Imani Shahabad, Reza Esmaeilizadeh, Farzad Liravi, Esmat Sheydaeian, Ke Yin Huang, Ehsan Marzbanrad, Mihaela Vlasea, Ehsan Toyserkani. On the measurement of relative powder-bed compaction density in powder-bed additive manufacturing processes. Materials & Design. 2018; 155 ():495-501.

Chicago/Turabian Style

Usman Ali; Yahya Mahmoodkhani; Shahriar Imani Shahabad; Reza Esmaeilizadeh; Farzad Liravi; Esmat Sheydaeian; Ke Yin Huang; Ehsan Marzbanrad; Mihaela Vlasea; Ehsan Toyserkani. 2018. "On the measurement of relative powder-bed compaction density in powder-bed additive manufacturing processes." Materials & Design 155, no. : 495-501.

Journal article
Published: 07 September 2018 in Journal of Manufacturing Processes
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Spherical powders are almost exclusively deployed for metal laser powder bed fusion (LPBF) additive manufacturing (AM). In this work, low-cost irregular powder feedstock is studied for its potential in three key areas to meet minimum AM process requirements, namely: (1) hopper flow, (2) layer spreading, and (3) de-powdering. Irregular water-atomized Iron powder was used as the study population, while spherical plasma-atomized Inconel 625 powder was used as the control. Powder flow characteristics were obtained using a FT4 Powder Rheometer (Freeman Technology). Layer spreading was evaluated indirectly via powder bed density measurements. Measurements were quantified by using printed artifacts for captive powder and evaluated using isopropanol infiltration and three-dimensional computed tomography (CT) imaging (Zeiss Xradia 520 Versa). Powder clearing from fine channels was quantified through vision-based measurements of printed artifacts (Dino-Lite DinoCapture 2.0). The results from this work demonstrated that: (1) A larger opening and steeper hopper angle are necessary to maintain a mass flow regime with the irregular powder. (2) Powder bed density is similarly consistent across the bed indicating adequate spreadability. (3) Water-atomized Iron powder has better de-powdering characteristics in the smallest cleared 0.6 mm diameter features, likely due to its 15% lower bed density.

ACS Style

Allan Rogalsky; Issa Rishmawi; Lisa Brock; Mihaela Vlasea. Low cost irregular feed stock for laser powder bed fusion. Journal of Manufacturing Processes 2018, 35, 446 -456.

AMA Style

Allan Rogalsky, Issa Rishmawi, Lisa Brock, Mihaela Vlasea. Low cost irregular feed stock for laser powder bed fusion. Journal of Manufacturing Processes. 2018; 35 ():446-456.

Chicago/Turabian Style

Allan Rogalsky; Issa Rishmawi; Lisa Brock; Mihaela Vlasea. 2018. "Low cost irregular feed stock for laser powder bed fusion." Journal of Manufacturing Processes 35, no. : 446-456.

Journal article
Published: 31 August 2018 in Data in Brief
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The adoption of metal binder jetting additive manufacturing (AM) for functional parts relies on a deep understanding between the materials, the design aspects, the additive manufacturing process and sintering. This work focuses on the relationship between sintering theory and process outcomes. The data included in this article provides additional supporting information on the authors' recent publication (Wheat et al., 2018 [1]) on the sinter structure analysis of commercially pure titanium parts manufactured using powder bed binder jetting additive manufacturing. For this work, commercially pure titanium was deployed to study the effect of powder size distributions on green and sintered part qualities (bulk density, relative density, particle size, pore size, sinter neck size). This manuscript includes the overall computed tomography visualization methods and results for the green and sintered samples using uni- and bi-modal powders. Moreover, the effective particle and pore size for the different batches of powder are presented.

ACS Style

Evan Wheat; Mihaela Vlasea; James Hinebaugh; Craig Metcalfe. Data related to the sinter structure analysis of titanium structures fabricated via binder jetting additive manufacturing. Data in Brief 2018, 20, 1029 -1038.

AMA Style

Evan Wheat, Mihaela Vlasea, James Hinebaugh, Craig Metcalfe. Data related to the sinter structure analysis of titanium structures fabricated via binder jetting additive manufacturing. Data in Brief. 2018; 20 ():1029-1038.

Chicago/Turabian Style

Evan Wheat; Mihaela Vlasea; James Hinebaugh; Craig Metcalfe. 2018. "Data related to the sinter structure analysis of titanium structures fabricated via binder jetting additive manufacturing." Data in Brief 20, no. : 1029-1038.

Journal article
Published: 01 May 2018 in Additive Manufacturing
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The feasibility of a hybrid additive manufacturing (AM) method combining material extrusion and powder bed binder jetting (PBBJ) techniques for fabrication of structures made of silicone (polysiloxane) is investigated in this paper. A full factorial experimental design was conducted to maximize the geometrical accuracy of the parts. The rheological and morphological properties of the silicone powders, the thermal characteristics of the liquid silicone binder, and mechanical characterization the additively manufactured parts are reported. Using this hybrid AM method, porous cylindrical structures (5 mm diameter (D) × 3 mm height (H)) with potential applications in biomedical industry were additively manufactured. The final structures are composed of ∼60% silicone powder, ∼ 30% silicone binder, and <10% air voids. These three phases are distributed throughout the structure in a non-uniform fashion.

ACS Style

Farzad Liravi; Mihaela Vlasea. Powder bed binder jetting additive manufacturing of silicone structures. Additive Manufacturing 2018, 21, 112 -124.

AMA Style

Farzad Liravi, Mihaela Vlasea. Powder bed binder jetting additive manufacturing of silicone structures. Additive Manufacturing. 2018; 21 ():112-124.

Chicago/Turabian Style

Farzad Liravi; Mihaela Vlasea. 2018. "Powder bed binder jetting additive manufacturing of silicone structures." Additive Manufacturing 21, no. : 112-124.

Data article
Published: 23 April 2018 in Data in Brief
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The data included in this article provides additional supporting information on our recent publication (Liravi et al., 2018 [1]) on a novel hybrid additive manufacturing (AM) method for fabrication of three-dimensional (3D) structures from silicone powder. A design of experiments (DoE) study has been carried out to optimize the geometrical fidelity of AM-made parts. This manuscript includes the details of a multi-level factorial DOE and the response optimization results. The variation in the temperature of powder-bed when exposed to heat is plotted as well. Furthermore, the effect of blending ratio of two parts of silicone binder on its curing speed was investigated by conducting DSC tests on a silicone binder with 100:2 precursor to curing agent ratio. The hardness of parts fabricated with non-optimum printing conditions are included and compared.

ACS Style

Farzad Liravi; Mihaela Vlasea. Data related to the experimental design for powder bed binder jetting additive manufacturing of silicone. Data in Brief 2018, 18, 1477 -1483.

AMA Style

Farzad Liravi, Mihaela Vlasea. Data related to the experimental design for powder bed binder jetting additive manufacturing of silicone. Data in Brief. 2018; 18 ():1477-1483.

Chicago/Turabian Style

Farzad Liravi; Mihaela Vlasea. 2018. "Data related to the experimental design for powder bed binder jetting additive manufacturing of silicone." Data in Brief 18, no. : 1477-1483.