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1
Gujba, Abdullahi K., and Mamoun Medraj. "Power Ultrasonic Additive Manufacturing: Process Parameters, Microstructure, and Mechanical Properties." Advances in Materials Science and Engineering 2020 (February 28, 2020): 1–17. http://dx.doi.org/10.1155/2020/1064870.
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Additive manufacturing (AM) for fabricating 3D metallic parts has recently received considerable attention. Among the emerging AM technologies is ultrasonic additive manufacturing (UAM) or ultrasonic consolidation (UC), which uses ultrasonic vibrations to bond similar or dissimilar materials to produce 3D builds. This technology has several competitive advantages over other AM technologies, which includes fabrication of dissimilar materials and complex shapes, higher deposition rate, and fabrication at lower temperatures, which results in no material transformation during processing. Although UAM process optimization and microstructure have been reported in the literature, there is still lack of standardized and satisfactory understanding of the mechanical properties of UAM builds. This could be attributed to structural defects associated with UAM processing. This article discusses the effects of UAM process parameters on the resulting microstructure and mechanical properties. Special attention is given to hardness, shear strength, tensile strength, fatigue, and creep measurements. Also, pull-out, push-out, and push-pin tests commonly employed to characterize bond quality and strength have been reviewed. Finally, current challenges and drawbacks of the process and potential applications have been addressed.
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Grossi, Niccolò, Antonio Scippa, Giuseppe Venturini, and Gianni Campatelli. "Process Parameters Optimization of Thin-Wall Machining for Wire Arc Additive Manufactured Parts." Applied Sciences 10, no. 21 (October 27, 2020): 7575. http://dx.doi.org/10.3390/app10217575.
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Additive manufacturing (AM) is an arising production process due to the possibility to produce monolithic components with complex shapes with one single process and without the need for special tooling. AM-produced parts still often require a machining phase, since their surface finish is not compliant with the strict requirements of the most advanced markets, such as aerospace, energy, and defense. Since reduced weight is a key requirement for these parts, they feature thin walls and webs, usually characterized by low stiffness, requiring the usage of low productivity machining parameters. The idea of this paper is to set up an approach which is able to predict the dynamics of a thin-walled part produced using AM. The knowledge of the workpiece dynamics evolution throughout the machining process can be used to carry out cutting parameter optimization with different objectives (e.g., chatter avoidance, force vibrations reduction). The developed approach exploits finite element (FE) analysis to predict the workpiece dynamics during the machining process, updating its changing geometry. The developed solution can automatically optimize the toolpath for the machining operation, generated by any Computer Aided Manufacturing (CAM) software updating spindle speed in accordance with the selected optimization strategies. The developed approach was tested using as a test case an airfoil.
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Lee, Won-Hyuk, Tae-Wook Na, Kyung-Woo Yi, Seung-Min Yang, Jang-Won Kang, Hyung Giun Kim, and Hyung-Ki Park. "Thermodynamic analysis of oxidation during selective laser melting of pure titanium." Rapid Prototyping Journal 26, no. 8 (June 26, 2020): 1401–4. http://dx.doi.org/10.1108/rpj-08-2019-0226.
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Purpose When a pure titanium component is fabricated in a selective laser melting (SLM) process using titanium powder, the oxygen concentration of the SLM sample increases compared to the initial powder. The purpose of this paper is to study the reason for increasing oxygen concentration after SLM. Design/methodology/approach To understand this phenomenon, the authors analyzed the oxidation behavior during the SLM process thermodynamically. Findings Based on the laser parameters used in this study, the temperature of the Ti melt during the SLM process was expected to rise to 2,150°C. Based on the thermodynamic analysis, the equilibrium oxygen partial pressure for oxidation was 2.32 × 10−19 atm at 2,150°C when the dissolved oxygen concentration in the titanium is 0.2 wt.%. However, the oxygen partial pressure inside the SLM chamber was 1 × 10−3 atm, which is much higher than the equilibrium oxygen partial pressure. Therefore, oxidation occurred during the SLM process, and the oxygen concentration of the SLM sample increased compared to the initial powder. Originality/value Most studies on fabricating Ti components using additive manufacturing (AM) have been focused on how the changes in the microstructures and mechanical properties depend on the process parameters. However, there are a few studies that analyzed the oxygen concentration change of Ti during the AM process and its causes. In this study, the authors analyzed the oxidation behavior during the SLM process thermodynamically.
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Ameen, Wadea, Muneer Khan Mohammed, and Abdulrahman Al-Ahmari. "Evaluation of Support Structure Removability for Additively Manufactured Ti6Al4V Overhangs via Electron Beam Melting." Metals 9, no. 11 (November 11, 2019): 1211. http://dx.doi.org/10.3390/met9111211.
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The addition of support structures is essential for the successful fabrication of overhang structures through additive manufacturing (AM). The support structures protect the overhang portion from distortions. They are fabricated with the functional parts and are removed later after the fabrication of the AM part. While structures bearing insufficient support result in defective overhangs, structures with excessive support result in higher material consumption, time and higher post-processing costs. The objective of this study is to investigate the effects of design and process parameters of support structures on support removability during the electron beam melting (EBM)-based additive manufacturing of the Ti6Al4V overhang part. The support design parameters include tooth parameters, no support offset, fragmentation parameters and perforation parameters. The EBM process parameters consist of beam current, beam scan speed and beam focus offset. The results show that both support design and process parameters have a significant effect on support removability. In addition, with the appropriate selection of design and process parameters, it is possible to significantly reduce the support removal time and protect the surface quality of the part.
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Heisel, U., and D. Albrecht. "Bearbeitungskräfte beim Bandsägen dynamisch messen*/Dynamic measurement of the processing forces during band-sawing - A holistic investigation of the sawing process." wt Werkstattstechnik online 105, no. 01-02 (2015): 35–40. http://dx.doi.org/10.37544/1436-4980-2015-01-02-37.
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Um die Standzeit von Sägebändern zu verlängern und die Schnittqualität am Werkstück zu erhöhen, ist das Wissen über den Einfluss der relevanten Parameter auf den Sägeprozess entscheidend. Bisher gibt es keine weitreichenden Untersuchungen zum Erfassen der gesamten Prozesskräfte beim Bandsägen. Daher wurde am Institut für Werkzeugmaschinen (IfW) der Universität Stuttgart eine Messeinrichtung zur detaillierten Untersuchung der Parameter Zerspankraft, Werkstückspannkraft, Sägebandspannung und Sägebandauslenkung während des Sägeprozesses entwickelt. To increase the tool life of saw bands and improve the cutting quality on the workpiece, it is essential to investigate the influence of the relevant parameters on the sawing process . So far, there are no major investigations to record the whole process forces during band-sawing. Hence a measuring system was developed at the IfW for the explicit investigation of the parameters of cutting force, workpiece clamping force, saw band tension as well as the displacement of the saw band during the sawing process.
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Chen, Shu Guang, Yi Du Zhang, Qiong Wu, and Han Jun Gao. "Effects of Substrate Parameters on the Residual Stress and Deflection of Ti-6Al-4V Walls in Additive Manufacturing Process." Materials Science Forum 976 (January 2020): 156–61. http://dx.doi.org/10.4028/www.scientific.net/msf.976.156.
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Given substrate parameters affect the heat transfer during additive manufacturing (AM) deposition process, the precision and residual stress of the component will also be affected. Such effect is an important aspect that should be considered but has not been reported. Thus, this paper presents a three-dimensional thermo-mechanical finite element model to study the effects of substrate parameters on the residual stress of Ti-6Al-4V walls during the AM process. The thermal and deflection histories and residual stress profile with different substrate parameters were investigated. Results show that the influence of the substrate height on the deflection, heat transfer and residual stress is most obvious, the length change has little influence on the deflection and stress distribution. The maximum deflection difference between the heights of 2.4 and 10.4 mm is 92.12%, the maximum deflection is reduced by 39.65% with the width increased from 15.4mm to 35.4mm. And the increased height is beneficial to the uniform of Z component residual stress but decrease uniformity of Y component residual stress.
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Klingvall Ek, Rebecca, Lars-Erik Rännar, Mikael Bäckstöm, and Peter Carlsson. "The effect of EBM process parameters upon surface roughness." Rapid Prototyping Journal 22, no. 3 (April 18, 2016): 495–503. http://dx.doi.org/10.1108/rpj-10-2013-0102.
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Purpose The surface roughness of products manufactured using the additive manufacturing (AM) technology of electron beam melting (EBM) has a special characteristic. Different product applications can demand rougher or finer surface structure, so the purpose of this study is to investigate the process parameters of EBM to find out how they affect surface roughness. Design/methodology/approach EBM uses metal powder to manufacture metal parts. A design of experiment plan was used to describe the effects of the process parameters on the average surface roughness of vertical surfaces. Findings The most important electron beam setting for surface roughness, according to this study, is a combination of “speed and current” in the contours. The second most important parameter is “contour offset”. The interaction between the “number of contours” and “contour offset” also appears to be important, as it shows a much higher probability of being active than any other interaction. The results show that the “line offset” is not important when using contours. Research limitations/implications This study examined “contour offset”, “number of contours”, “speed in combination with current” and “line offset”, which are process parameters controlling the electron beam. Practical implications The surface properties could have an impact on the product’s performance. A reduction in surface processing will not only save time and money but also reduce the environmental impact. Originality/value Surface properties are important for many products. New themes containing process parameters have to be developed when introducing new materials to EBM manufacturing. During this process, it is very important to understand how the electron beam affects the melt pool.
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Ahmed, Sazzad H., and Ahsan Mian. "Influence of Material Property Variation on Computationally Calculated Melt Pool Temperature during Laser Melting Process." Metals 9, no. 4 (April 18, 2019): 456. http://dx.doi.org/10.3390/met9040456.
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Selective Laser Melting (SLM) is a popular additive manufacturing (AM) method where a laser beam selectively melts powder layer by layer based on the building geometry. The melt pool peak temperature during build process is an important parameter to determine build quality of a fabricated component by SLM process. The melt pool temperature depends on process parameters including laser power, scanning speed, and hatch space as well as the properties of the build material. In this paper, the sensitivity of melt pool peak temperature during the build process to temperature dependent material properties including density, specific heat, and thermal conductivity are investigated for a range of laser powers and laser scanning speeds. It is observed that the melt pool temperature is most sensitive to melt pool thermal conductivity of the processed material for a set of specific process parameters (e.g., laser power and scan speed). Variations in the other mechanical–physical properties of powder and melt pool such as density and specific heat are found to have minimal effect on melt pool temperature.
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Greco, Sebastian, Sonja Kieren-Ehses, Benjamin Kirsch, and Jan C. Aurich. "Micro milling of additively manufactured AISI 316L: impact of the layerwise microstructure on the process results." International Journal of Advanced Manufacturing Technology 112, no. 1-2 (November 19, 2020): 361–73. http://dx.doi.org/10.1007/s00170-020-06387-3.
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AbstractIn the field of metal additive manufacturing (AM), one of the most used methods is selective laser melting (SLM)—building components layer by layer in a powder bed via laser. The process of SLM is defined by several parameters like laser power, laser scanning speed, hatch spacing, or layer thickness. The manufacturing of small components via AM is very difficult as it sets high demands on the powder to be used and on the SLM process in general. Hence, SLM with subsequent micromilling is a suitable method for the production of microstructured, additively manufactured components. One application for this kind of components is microstructured implants which are typically unique and therefore well suited for additive manufacturing. In order to enable the micromachining of additively manufactured materials, the influence of the special properties of the additive manufactured material on micromilling processes needs to be investigated. In this research, a detailed characterization of additive manufactured workpieces made of AISI 316L is shown. Further, the impact of the process parameters and the build-up direction defined during SLM on the workpiece properties is investigated. The resulting impact of the workpiece properties on micromilling is analyzed and rated on the basis of process forces, burr formation, surface roughness, and tool wear. Significant differences in the results of micromilling were found depending on the geometry of the melt paths generated during SLM.
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Razavykia, Abbas, Eugenio Brusa, Cristiana Delprete, and Reza Yavari. "An Overview of Additive Manufacturing Technologies—A Review to Technical Synthesis in Numerical Study of Selective Laser Melting." Materials 13, no. 17 (September 3, 2020): 3895. http://dx.doi.org/10.3390/ma13173895.
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Additive Manufacturing (AM) processes enable their deployment in broad applications from aerospace to art, design, and architecture. Part quality and performance are the main concerns during AM processes execution that the achievement of adequate characteristics can be guaranteed, considering a wide range of influencing factors, such as process parameters, material, environment, measurement, and operators training. Investigating the effects of not only the influential AM processes variables but also their interactions and coupled impacts are essential to process optimization which requires huge efforts to be made. Therefore, numerical simulation can be an effective tool that facilities the evaluation of the AM processes principles. Selective Laser Melting (SLM) is a widespread Powder Bed Fusion (PBF) AM process that due to its superior advantages, such as capability to print complex and highly customized components, which leads to an increasing attention paid by industries and academia. Temperature distribution and melt pool dynamics have paramount importance to be well simulated and correlated by part quality in terms of surface finish, induced residual stress and microstructure evolution during SLM. Summarizing numerical simulations of SLM in this survey is pointed out as one important research perspective as well as exploring the contribution of adopted approaches and practices. This review survey has been organized to give an overview of AM processes such as extrusion, photopolymerization, material jetting, laminated object manufacturing, and powder bed fusion. And in particular is targeted to discuss the conducted numerical simulation of SLM to illustrate a uniform picture of existing nonproprietary approaches to predict the heat transfer, melt pool behavior, microstructure and residual stresses analysis.
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Fahad, Muhammad, and Neil Hopkinson. "Evaluation of Parts Produced by a Novel Additive Manufacturing Process." Applied Mechanics and Materials 315 (April 2013): 63–67. http://dx.doi.org/10.4028/www.scientific.net/amm.315.63.
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Rapid prototyping refers to building three dimensional parts in a tool-less, layer by layer manner using the CAD geometry of the part. Additive Manufacturing (AM) is the name given to the application of rapid prototyping technologies to produce functional, end use items. Since AM is relatively new area of manufacturing processes, various processes are being developed and analyzed for their performance (mainly speed and accuracy). This paper deals with the design of a new benchmark part to analyze the flatness of parts produced on High Speed Sintering (HSS) which is a novel Additive Manufacturing process and is currently being developed at Loughborough University. The designed benchmark part comprised of various features such as cubes, holes, cylinders, spheres and cones on a flat base and the build material used for these parts was nylon 12 powder. Flatness and curvature of the base of these parts were measured using a coordinate measuring machine (CMM) and the results are discussed in relation to the operating parameters of the process.The result show changes in the flatness of part with the depth of part in the bed which is attributed to the thermal gradient within the build envelope during build.
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Mondal, Sudeepta, Daniel Gwynn, Asok Ray, and Amrita Basak. "Investigation of Melt Pool Geometry Control in Additive Manufacturing Using Hybrid Modeling." Metals 10, no. 5 (May 22, 2020): 683. http://dx.doi.org/10.3390/met10050683.
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Metal additive manufacturing (AM) works on the principle of consolidating feedstock material in layers towards the fabrication of complex objects through localized melting and resolidification using high-power energy sources. Powder bed fusion and directed energy deposition are two widespread metal AM processes that are currently in use. During layer-by-layer fabrication, as the components continue to gain thermal energy, the melt pool geometry undergoes substantial changes if the process parameters are not appropriately adjusted on-the-fly. Although control of melt pool geometry via feedback or feedforward methods is a possibility, the time needed for changes in process parameters to translate into adjustments in melt pool geometry is of critical concern. A second option is to implement multi-physics simulation models that can provide estimates of temporal process parameter evolution. However, such models are computationally near intractable when they are coupled with an optimization framework for finding process parameters that can retain the desired melt pool geometry as a function of time. To address these challenges, a hybrid framework involving machine learning-assisted process modeling and optimization for controlling the melt pool geometry during the build process is developed and validated using experimental observations. A widely used 3D analytical model capable of predicting the thermal distribution in a moving melt pool is implemented and, thereafter, a nonparametric Bayesian, namely, Gaussian Process (GP), model is used for the prediction of time-dependent melt pool geometry (e.g., dimensions) at different values of the process parameters with excellent accuracy along with uncertainty quantification at the prediction points. Finally, a surrogate-assisted statistical learning and optimization architecture involving GP-based modeling and Bayesian Optimization (BO) is employed for predicting the optimal set of process parameters as the scan progresses to keep the melt pool dimensions at desired values. The results demonstrate that a model-based optimization can be significantly accelerated using tools of machine learning in a data-driven setting and reliable a priori estimates of process parameter evolution can be generated to obtain desired melt pool dimensions for the entire build process.
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Obilanade, Didunoluwa, Christo Dordlofva, and Peter Törlind. "SURFACE ROUGHNESS CONSIDERATIONS IN DESIGN FOR ADDITIVE MANUFACTURING - A LITERATURE REVIEW." Proceedings of the Design Society 1 (July 27, 2021): 2841–50. http://dx.doi.org/10.1017/pds.2021.545.
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AbstractOne often-cited benefit of using metal additive manufacturing (AM) is the possibility to design and produce complex geometries that suit the required function and performance of end-use parts. In this context, laser powder bed fusion (LPBF) is one suitable AM process. Due to accessibility issues and cost-reduction potentials, such ‘complex’ LPBF parts should utilise net-shape manufacturing with minimal use of post-process machining. The inherent surface roughness of LPBF could, however, impede part performance, especially from a structural perspective and in particular regarding fatigue. Engineers must therefore understand the influence of surface roughness on part performance and how to consider it during design. This paper presents a systematic literature review of research related to LPBF surface roughness. In general, research focuses on the relationship between surface roughness and LPBF build parameters, material properties, or post-processing. Research on design support on how to consider surface roughness during design for AM is however scarce. Future research on such supports is therefore important given the effects of surface roughness highlighted in other research fields.
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Taqi, Shahad A., and Saad K. Shatner. "Investigation the Effect of Negative Polarity of Surface Roughness and Metal Removal Rate During EDM Process." Engineering and Technology Journal 38, no. 12A (December 25, 2020): 1852–61. http://dx.doi.org/10.30684/etj.v38i12a.1591.
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The Electro discharge machine that named (EDM) is used to remove the metal from the workpiece by spark erosion. The work of this machining depends on the multiple variables. One of the most influential variants of this machine is the polarity, the material of the electrode, the current and the time pulses. Essentially the polarity of the tool (electrode) positive and the work piece is negative, this polarity can be reversed in this paper was reversed the polarity that was made the tool (electrode) negative and the work piece was positive. The aim of this paper was focused on the influence of reversed the polarity (negative) with changing the electrode metal (copper and graphite) on the surface roughness and metal removal rate by using different parameters (current and pulses of time). Experiments show that: the copper electrode gives (best surface roughness 0.46 µm when the current 5 Am and Ton 5.5 µs) and (worst surface roughness 1.66 µm when the current is 8 A and Ton 25 µs). And give (best values of the MRR 0.00291 g/min when the current is 8 and Ton 25 µs) and (The lowest values of MRR (0.00054 g/min when current is 5 and Ton 5.5 µs). The graphite electrode gives (best surface roughness 2.07 µm when the current 5 Am and Ton 5.5 µs) and (worst surface roughness 4.17 µm when the current is 8 A and Ton 25 µs). And give (best values of the MRR 0.05823 g/min when the current is...
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Taqi, Shahad A., and Saad K. Shatner. "Investigation the Effect of Negative Polarity of Surface Roughness and Metal Removal Rate During EDM Process." Engineering and Technology Journal 38, no. 12A (December 25, 2020): 1852–61. http://dx.doi.org/10.30684/etj.v38i12a.1591.
Full textAbstract:
The Electro discharge machine that named (EDM) is used to remove the metal from the workpiece by spark erosion. The work of this machining depends on the multiple variables. One of the most influential variants of this machine is the polarity, the material of the electrode, the current and the time pulses. Essentially the polarity of the tool (electrode) positive and the work piece is negative, this polarity can be reversed in this paper was reversed the polarity that was made the tool (electrode) negative and the work piece was positive. The aim of this paper was focused on the influence of reversed the polarity (negative) with changing the electrode metal (copper and graphite) on the surface roughness and metal removal rate by using different parameters (current and pulses of time). Experiments show that: the copper electrode gives (best surface roughness 0.46 µm when the current 5 Am and Ton 5.5 µs) and (worst surface roughness 1.66 µm when the current is 8 A and Ton 25 µs). And give (best values of the MRR 0.00291 g/min when the current is 8 and Ton 25 µs) and (The lowest values of MRR (0.00054 g/min when current is 5 and Ton 5.5 µs). The graphite electrode gives (best surface roughness 2.07 µm when the current 5 Am and Ton 5.5 µs) and (worst surface roughness 4.17 µm when the current is 8 A and Ton 25 µs). And give (best values of the MRR 0.05823 g/min when the current is...
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Kim, Hoejin, Yirong Lin, and Tzu-Liang Bill Tseng. "A review on quality control in additive manufacturing." Rapid Prototyping Journal 24, no. 3 (April 9, 2018): 645–69. http://dx.doi.org/10.1108/rpj-03-2017-0048.
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Purpose The usage of additive manufacturing (AM) technology in industries has reached up to 50 per cent as prototype or end-product. However, for AM products to be directly used as final products, AM product should be produced through advanced quality control process, which has a capability to be able to prove and reach their desire repeatability, reproducibility, reliability and preciseness. Therefore, there is a need to review quality-related research in terms of AM technology and guide AM industry in the future direction of AM development. Design/methodology/approach This paper overviews research progress regarding the QC in AM technology. The focus of the study is on manufacturing quality issues and needs that are to be developed and optimized, and further suggests ideas and directions toward the quality improvement for future AM technology. This paper is organized as follows. Section 2 starts by conducting a comprehensive review of the literature studies on progress of quality control, issues and challenges regarding quality improvement in seven different AM techniques. Next, Section 3 provides classification of the research findings, and lastly, Section 4 discusses the challenges and future trends. Findings This paper presents a review on quality control in seven different techniques in AM technology and provides detailed discussions in each quality process stage. Most of the AM techniques have a trend using in-situ sensors and cameras to acquire process data for real-time monitoring and quality analysis. Procedures such as extrusion-based processes (EBP) have further advanced in data analytics and predictive algorithms-based research regarding mechanical properties and optimal printing parameters. Moreover, compared to others, the material jetting progresses technique has advanced in a system integrated with closed-feedback loop, machine vision and image processing to minimize quality issues during printing process. Research limitations/implications This paper is limited to reviewing of only seven techniques of AM technology, which includes photopolymer vat processes, material jetting processes, binder jetting processes, extrusion-based processes, powder bed fusion processes, directed energy deposition processes and sheet lamination processes. This paper would impact on the improvement of quality control in AM industries such as industrial, automotive, medical, aerospace and military production. Originality/value Additive manufacturing technology, in terms of quality control has yet to be reviewed.
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Maucher, Clemens, Heiko Teich, and Hans-Christian Möhring. "Improving machinability of additively manufactured components with selectively weakened material." Production Engineering 15, no. 3-4 (March 2, 2021): 535–44. http://dx.doi.org/10.1007/s11740-021-01038-2.
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AbstractPart design and the possibilities of production are disrupted by the increased usage of additive manufacturing (AM). Featuring excellent creative freedom due to the layer-by-layer buildup of components, AM leads to profound changes in future part design and enables previously impossible geometries. Laser powder bed fusion (LPBF) technology already allows to manufacture small quantities of parts with high productivity and material efficiency. Due to the specific process characteristics, the resulting surface finish of these parts is insufficient for a wide range of applications, and post-processing is usually unavoidable. Specifically for functional surfaces, this post-processing is often done by machining processes, which can pose challenges for intricate and complex AM parts due to excessive machining forces. In the present paper, the influence and the possibilities of the LPBF process parameters on the subtractive post-processing are shown. A novel weakened structure is developed to selectively reduce the strength of the material and improve the cutting conditions. Chip formation, cutting forces and vibrations during drilling as well as cutting forces during an orthogonal cut are examined. To quantify the differences, a comparison of the machinability between bulk material, standard support structures and the weakened structure is carried out.
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Maricic, Aleksa, and Momcilo Ristic. "Corelation between the crystallisation process and change in thermoelectromotive force for the amorphous alloy Fe89.8Ni1.5Si5.2B3C0.5." Science of Sintering 35, no. 1 (2003): 31–36. http://dx.doi.org/10.2298/sos0301031m.
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Thermal and kinetic analyses of the structural changes for the amorphous alloy Fe89.8Ni1.5Si5.2B3C0.5, during the processes of non-isothermal heating and isothermal annealing, have been performed. The crystallisation process has been investigated using the method of differential scanning calorimetry (DSC). It is determined that this alloy crystalizes through three different stages. Changes in the electronic structure of the amorphous tape, for the temperature range 20 to 700?C have been studied. This was achieved by measuring the thermoelectromotive force (TEMS), of the thermo pair made of two tapes with same chemical structure of the alloy FeNiSiBC, but different atomic structure: one is in the crystal state (CL) and the other is in the amorphous state (AM). Analysis of the temperature dependence of the electromotive force has shown the following: the investigated alloy is thermically stable up to 450?C and changes in the atomic structure as well as equalising of the free electron density in both parts of the thermo pair AM-CL, take place in the temperature range from 450 to 550?C. Kinetic parameters of the process were determined by measuring time dependence of the TEMS in isothermic conditions at the temperatures 450, 480 and 510?C.
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Dadkhah, Mehran, Mohammad Hossein Mosallanejad, Luca Iuliano, and Abdollah Saboori. "A Comprehensive Overview on the Latest Progress in the Additive Manufacturing of Metal Matrix Composites: Potential, Challenges, and Feasible Solutions." Acta Metallurgica Sinica (English Letters) 34, no. 9 (May 23, 2021): 1173–200. http://dx.doi.org/10.1007/s40195-021-01249-7.
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AbstractNowadays, as an emerging technology, additive manufacturing (AM) has received numerous attentions from researchers around the world. The method comprises layer-by-layer manufacturing of products according to the 3D CAD models of the objects. Among other things, AM is capable of producing metal matrix composites (MMCs). Hence, plenty of works in the literature are dedicated to developing different types of MMCs through AM processes. Hence, this paper provides a comprehensive overview on the latest research that has been carried out on the development of the powder-based AM manufactured MMCs from a scientific and technological viewpoint, aimed at highlighting the opportunities and challenges of this innovative manufacturing process. For instance, it is documented that AM is not only able to resolve the reinforcement/matrix bonding issues usually faced with during conventional manufacturing of MMCs, but also it is capable of producing functionally graded composites and geometrically complex objects. Furthermore, it provides the opportunity for a uniform distribution of the reinforcing phase in the metallic matrix and is able to produce composites using refractory metals thanks to the local heat source employed in the method. Despite the aforementioned advantages, there are still some challenges needing more attention from the researchers. Rapid cooling nature of the process, significantly different coefficient of expansion of the matrix and reinforcement, processability, and the lack of suitable parameters and standards for the production of defect-free AM MMCs seem to be among the most important issues to deal with in future works.
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Jaenisch, Gerd-Rüdiger, Uwe Ewert, Anja Waske, and Alexander Funk. "Radiographic Visibility Limit of Pores in Metal Powder for Additive Manufacturing." Metals 10, no. 12 (December 4, 2020): 1634. http://dx.doi.org/10.3390/met10121634.
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The quality of additively manufactured (AM) parts is determined by the applied process parameters used and the properties of the feedstock powder. The influence of inner gas pores in feedstock particles on the final AM product is a phenomenon which is difficult to investigate since very few non-destructive measurement techniques are accurate enough to resolve the micropores. 3D X-ray computed tomography (XCT) is increasingly applied during the process chain of AM parts as a non-destructive monitoring and quality control tool and it is able to detect most of the pores. However, XCT is time-consuming and limited to small amounts of feedstock powder, typically a few milligrams. The aim of the presented approach is to investigate digital radiography of AM feedstock particles as a simple and fast quality check with high throughput. 2D digital radiographs were simulated in order to predict the visibility of pores inside metallic particles for different pore and particle diameters. An experimental validation was performed. It was demonstrated numerically and experimentally that typical gas pores above a certain size (here: 3 to 4.4 µm for the selected X-ray setup), which could be found in metallic microparticles, were reliably detected by digital radiography.
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Kiran, Abhilash, Martina Koukolíková, Jaroslav Vavřík, Miroslav Urbánek, and Jan Džugan. "Base Plate Preheating Effect on Microstructure of 316L Stainless Steel Single Track Deposition by Directed Energy Deposition." Materials 14, no. 18 (September 7, 2021): 5129. http://dx.doi.org/10.3390/ma14185129.
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The microstructural morphology in additive manufacturing (AM) has a significant influence on the building structure. High-energy concentric heat source scanning leads to rapid heating and cooling during material deposition. This results in a unique microstructure. The size and morphology of the microstructure have a strong directionality, which depends on laser power, scanning rate, melt pool fluid dynamics, and material thermal properties, etc. The grain structure significantly affects its resistance to solidification cracking and mechanical properties. Microstructure control is challenging for AM considering multiple process parameters. A preheating base plate has a significant influence on residual stress, defect-free AM structure, and it also minimizes thermal mismatch during the deposition. In the present work, a simple single track deposition experiment was designed to analyze base plate preheating on microstructure. The microstructural evolution at different preheating temperatures was studied in detail, keeping process parameters constant. The base plate was heated uniformly from an external heating source and set the stable desired temperature on the surface of the base plate before deposition. A single track was deposited on the base plate at room temperature and preheating temperatures of 200 °C, 300 °C, 400 °C, and 500 °C. Subsequently, the resulting microstructural morphologies were analyzed and compared. The microstructure was evaluated using electron backscattered diffraction (EBSD) imaging in the transverse and longitudinal sections. An increase in grain size area fraction was observed as the preheating temperature increased. Base plate preheating did not show influence on grain boundary misorientation. An increase in the deposition depth was noticed for higher base plate preheating temperatures. The results were convincing that grain morphology and columnar grain orientation can be tailored by base plate preheating.
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Galeeva, R. U., and S. V. Kuksov. "Algorithm for simulating the self-starting of a group of asynchronous electric motors with a short-circulated rotor." Power engineering: research, equipment, technology 23, no. 3 (July 20, 2021): 196–208. http://dx.doi.org/10.30724/1998-9903-2021-23-3-196-208.
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PURPOSE. To consider the problems of modeling the processes of run-out, self-starting of a group of asynchronous electric motors (AM) in case of short-term power outages (NEC) and voltage drops in external short circuits (SC), convenient for programming and practical use. To establish the integral reaction of the AM group during self-start to the disturbing effect, taking into account their characteristics and duration to establish the permissible limit values of the NEC. To develop an algorithm for the transient process of self-starting of the AM group when using matrix and vector data representation when solving the basic equation of the rotor motion and its computer implementation. METHODS. When solving the problem, the following methods were used: successive approximations when solving the basic electromechanical equation, taking into account electromagnetic transient processes; Gauss-Seidel method with accelerating the convergence of the iterative process when solving the equations of the parameters of the regime; method of nodal stresses. The algorithm is implemented in VBA and tested in Matlab Simulink. RESULTS. The article describes the relevance of the topic, considers a model of AM according to catalog data, an algorithm for self-starting a group of an AM with NEC and external short circuits, taking into account electromagnetic transient processes, which has high accuracy and is convenient for practical use. CONCLUSION. The use of asynchronous motor catalogs makes it possible not to carry out laborious preliminary calculations of the parameters of asynchronous motors. The application of the Gauss-Seidel method with acceleration of convergence provides a decrease in the number of iterations. Taking into account electromagnetic transients and the effect of displacement of the rotor current allows you to evaluate the mutual influence of motors and increase the accuracy of calculations. The use of the method of nodal voltages makes it possible to determine the residual voltage on the busbar section with AM, if at the first moment the motors are switched on to short circuit. The implementation of the algorithm in the VBA environment is convenient for practical use.
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Galeeva, R. U., and S. V. Kuksov. "Algorithm for simulating the self-starting of a group of asynchronous electric motors with a short-circulated rotor." Power engineering: research, equipment, technology 23, no. 3 (July 20, 2021): 181–93. http://dx.doi.org/10.30724/1998-9903-2021-23-3-181-193.
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PURPOSE. To consider the problems of modeling the processes of run-out, self-starting of a group of asynchronous electric motors (AM) in case of short-term power outages (NEC) and voltage drops in external short circuits (SC), convenient for programming and practical use. To establish the integral reaction of the AM group during self-start to the disturbing effect, taking into account their characteristics and duration to establish the permissible limit values of the NEC. To develop an algorithm for the transient process of self-starting of the AM group when using matrix and vector data representation when solving the basic equation of the rotor motion and its computer implementation. METHODS. When solving the problem, the following methods were used: successive approximations when solving the basic electromechanical equation, taking into account electromagnetic transient processes; Gauss-Seidel method with accelerating the convergence of the iterative process when solving the equations of the parameters of the regime; method of nodal stresses. The algorithm is implemented in VBA and tested in Matlab Simulink. RESULTS. The article describes the relevance of the topic, considers a model of AM according to catalog data, an algorithm for self-starting a group of an AM with NEC and external short circuits, taking into account electromagnetic transient processes, which has high accuracy and is convenient for practical use. CONCLUSION. The use of asynchronous motor catalogs makes it possible not to carry out laborious preliminary calculations of the parameters of asynchronous motors. The application of the Gauss-Seidel method with acceleration of convergence provides a decrease in the number of iterations. Taking into account electromagnetic transients and the effect of displacement of the rotor current allows you to evaluate the mutual influence of motors and increase the accuracy of calculations. The use of the method of nodal voltages makes it possible to determine the residual voltage on the busbar section with AM, if at the first moment the motors are switched on to short circuit. The implementation of the algorithm in the VBA environment is convenient for practical use.
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Stoia, Dan, Emanoil Linul, and Liviu Marsavina. "Influence of Manufacturing Parameters on Mechanical Properties of Porous Materials by Selective Laser Sintering." Materials 12, no. 6 (March 15, 2019): 871. http://dx.doi.org/10.3390/ma12060871.
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This paper presents a study on the tensile properties of Alumide and polyamide PA2200 standard samples produced by Additive manufacturing (AM) based on selective laser sintering (SLS). Because of the orthogonal trajectories of the laser beam during exposure, different orientations of the samples may lead to different mechanical properties. In order to reveal this process issue, four orientations of the samples in building envelope were investigated. For data reliability, all the other process parameters were constant for each material and every orientation. The tensile tests highlight small differences in elastic properties of the two materials, while significant differences in strength properties and energy absorption were observed. Nevertheless, Young modulus indicates high stiffness of the Alumide comparing to PA2200 samples. The stereo microscopy reveals a brittle fracture site for Alumide and a ductile fracture with longitudinal splitting zones for PA2200. From the orientation point of view, similar properties of samples oriented at 0 and 90 degrees for all investigated mechanical properties were observed. However, tensile strength was less influenced by the sample orientations.
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Chen, Shuying, Yang Tong, and Peter Liaw. "Additive Manufacturing of High-Entropy Alloys: A Review." Entropy 20, no. 12 (December 6, 2018): 937. http://dx.doi.org/10.3390/e20120937.
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Owing to the reduced defects, low cost, and high efficiency, the additive manufacturing (AM) technique has attracted increasingly attention and has been applied in high-entropy alloys (HEAs) in recent years. It was found that AM-processed HEAs possess an optimized microstructure and improved mechanical properties. However, no report has been proposed to review the application of the AM method in preparing bulk HEAs. Hence, it is necessary to introduce AM-processed HEAs in terms of applications, microstructures, mechanical properties, and challenges to provide readers with fundamental understanding. Specifically, we reviewed (1) the application of AM methods in the fabrication of HEAs and (2) the post-heat treatment effect on the microstructural evolution and mechanical properties. Compared with the casting counterparts, AM-HEAs were found to have a superior yield strength and ductility as a consequence of the fine microstructure formed during the rapid solidification in the fabrication process. The post-treatment, such as high isostatic pressing (HIP), can further enhance their properties by removing the existing fabrication defects and residual stress in the AM-HEAs. Furthermore, the mechanical properties can be tuned by either reducing the pre-heating temperature to hinder the phase partitioning or modifying the composition of the HEA to stabilize the solid-solution phase or ductile intermetallic phase in AM materials. Moreover, the processing parameters, fabrication orientation, and scanning method can be optimized to further improve the mechanical performance of the as-built-HEAs.
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Oehlmann, Paul, Paul Osswald, Juan Camilo Blanco, Martin Friedrich, Dominik Rietzel, and Gerd Witt. "Modeling Fused Filament Fabrication using Artificial Neural Networks." Production Engineering 15, no. 3-4 (February 7, 2021): 467–78. http://dx.doi.org/10.1007/s11740-021-01020-y.
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AbstractWith industries pushing towards digitalized production, adaption to expectations and increasing requirements for modern applications, has brought additive manufacturing (AM) to the forefront of Industry 4.0. In fact, AM is a main accelerator for digital production with its possibilities in structural design, such as topology optimization, production flexibility, customization, product development, to name a few. Fused Filament Fabrication (FFF) is a widespread and practical tool for rapid prototyping that also demonstrates the importance of AM technologies through its accessibility to the general public by creating cost effective desktop solutions. An increasing integration of systems in an intelligent production environment also enables the generation of large-scale data to be used for process monitoring and process control. Deep learning as a form of artificial intelligence (AI) and more specifically, a method of machine learning (ML) is ideal for handling big data. This study uses a trained artificial neural network (ANN) model as a digital shadow to predict the force within the nozzle of an FFF printer using filament speed and nozzle temperatures as input data. After the ANN model was tested using data from a theoretical model it was implemented to predict the behavior using real-time printer data. For this purpose, an FFF printer was equipped with sensors that collect real time printer data during the printing process. The ANN model reflected the kinematics of melting and flow predicted by models currently available for various speeds of printing. The model allows for a deeper understanding of the influencing process parameters which ultimately results in the determination of the optimum combination of process speed and print quality.
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Bai, Shuang, Hyeong Jae Lee, and Jian Liu. "3D Printing with Mixed Powders of Boron Carbide and Al Alloy." Applied Sciences 10, no. 9 (April 27, 2020): 3055. http://dx.doi.org/10.3390/app10093055.
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Laser additive manufacturing with mixed powders of boron carbide and aluminum alloy is investigated. Parameters such as laser power, scan speed, scan pattern, and hatching space are systematically evaluated and optimized to obtain the desired density and porosity. These results show that the AM part contains 20 wt% boron carbide and 80 wt% aluminum alloy, which are well mixed and synthesized during the melting process. Its mechanical properties are close to those of aluminum. A thin-wall structure based two dimensional and three dimensional radial collimators were fabricated with well-controlled geometry for neutron scattering measurement.
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Zhonggang, Sun, Ji Shuwei, Guo Yanhua, Lu Yichen, Chang Lili, and Xing Fei. "Microstructure evolution and mechanical properties of Hastelloy X alloy produced by Selective Laser Melting." High Temperature Materials and Processes 39, no. 1 (May 27, 2020): 124–35. http://dx.doi.org/10.1515/htmp-2020-0032.
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AbstractSelective laser melting (SLM) is considered as an important additive manufacturing (AM) technology which can fabricate parts with complex geometry. However, it is difficult to predict the optimal SLM-parameters of metallic materials. In this study, orthogonal experiments were designed to study the influence of SLM-process parameters on the density and fabricated quality of Hastelloy X superalloy. Moreover, the relationship between microstructure evolution and performance of deposited microstructure was studied after heat treatment. The laser power, scanning speed and energy density have a significant effect on the density of the fabricated parts. The optimal parameters for determining Hastelloy X are 250 W laser power, 500 mm/s scanning speed, 100 μm hatch space, and 30 μmlayer thickness. The deposited microstructure is a lamellar microstructure in the horizontal direction and a columnar crystal in the longitudinal direction, and the microstructure is mainly martensite. After solid-solution and aging treatment, grain grows up. Martensite decomposes and the carbide M6C was precipitated during the aging process. The strength of the microstructure decreases slightly due to the growth of grain size.
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Razavykia, Abbas, Eugenio Brusa, Sina Ghodsieh, and Lorenzo Giorio. "DoE Applied to Thermal Analysis and Simulation of Geometrical Stability of a Wind Turbine Blade Made by Selective Laser Melting." Advanced Materials Research 1161 (March 2021): 65–74. http://dx.doi.org/10.4028/www.scientific.net/amr.1161.65.
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The Selective Laser Melting (SLM) is one of the most demanding additive manufacturing(AM) processes, although it assures some superior advantages in producing complex structural componentsand applies to a wide range of materials. The control of SLM parameters is crucial to guaranteethe quality of manufactured component. The steep thermal variation in part during the SLM processinduces some undesired effects, such as warping, residual thermal stresses and microcracks,as wellas geometrical instability. Effectively predicting the influence of process parameters upon the productquality of part made by SLM is extremely useful in the earliest steps of design, especially whena higher productivity is required. Particularly, thermal simulation is used to suitably calibrate someprocess parameters, to improve efficiency and reduce defects. Besides, such simulation is exploited toimprove the heat transfer between the bed and the first product layer, to reduce thermal stress and theoverall product deformation. This study exemplifies how numerical modeling of temperature distributionin a wind turbine blade made by SLM allows predicting the dimensional stability. The Design ofExperiments (DoE) and ANOVA analysis helped in studying effects on the product geometric stabilityand deformation, of some process parameters, as powder layer thickness, hatch space and laser scanspeed.
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Li, Jiang, Shangqin Yuan, Jihong Zhu, Shaoying Li, and Weihong Zhang. "Numerical Model and Experimental Validation for Laser Sinterable Semi-Crystalline Polymer: Shrinkage and Warping." Polymers 12, no. 6 (June 18, 2020): 1373. http://dx.doi.org/10.3390/polym12061373.
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Shrinkage and warping of additive manufacturing (AM) parts are two critical issues that adversely influence the dimensional accuracy especially in powder bed fusion processes such as selective laser sintering (SLS). Powder fusion, material solidification, and recrystallization are the key stages causing volumetric changes of polymeric materials during the abrupt heating–cooling process. In this work, the mechanisms of shrinkage and warping of semi-crystalline polyamide (PA) 12 in SLS are well investigated. Heat-transfer and thermo-mechanical models are established to predict the process-dependent shrinkage and warping. The influence of raw material- and laser-related parameters are considered in the heat-transfer and thermo-mechanical models. Such models are established considering the natural thermal gradient and dynamic recrystallization, which induce internal strain and volumetric change. Moreover, an experimental design via orthogonal approach is introduced to validate the feasibility and accuracy of the proposed models. Finally, the quantitative relationships of process parameters with product shrinkage and warping are established; the dimensional accuracy in part-scale can be well predicted and validated with printed parts in a real experiment.
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Hamulczuk, Dominika, and Ola Isaksson. "DATA ANALYSIS AS THE BASIS FOR IMPROVED DESIGN FOR ADDITIVE MANUFACTURING (DFAM)." Proceedings of the Design Society 1 (July 27, 2021): 811–20. http://dx.doi.org/10.1017/pds.2021.81.
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AbstractAdditive Manufacturing (AM) has a large potential to revolutionize the manufacturing industry, yet the printing parameters and part design have a profound impact on the robustness of the printing process as well as the resulting quality of the manufactured components. To control the printing process, a substantial number of parameters is measured while printing and used primarily to control and adjust the printing process in-situ. The question raised in this paper is how to benefit from these data being gathered to gain insight into the print process stability. The case study performed included the analysis of data gathered during printing 22 components. The analysis was performed with a widely used Random Forest Classifier. The study revealed that the data did contain some detectable patterns that can be used further in assessing the quality of the printed component, however, they were distinct enough so that in case the test and train sets were comprised of separate components the predictions’ result was very poor. The study gives a good understanding of what is necessary to do a meaningful analytics study of manufacturing data from a design perspective.
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Bian, Peiying, Xiaodong Shao, and Jingli Du. "Finite Element Analysis of Thermal Stress and Thermal Deformation in Typical Part during SLM." Applied Sciences 9, no. 11 (May 30, 2019): 2231. http://dx.doi.org/10.3390/app9112231.
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Selective laser melting (SLM) constitutes an additive manufacturing (AM) method. Many issues such as thermal strain and macro-thermal deformation, which are caused by the thermal stress of different process parameters, are not clear. In this paper, an efficient and fast manufacturing simulation method was researched based on a moving heat source model and an elastoplastic theory of welding simulation, which was studied based on the thermodynamic coupling algorithm with a software-developed application for the SLM process. Subsequently, typical case results of thin and hollow plate part formation and the corresponding performances were simulated in detail. The results demonstrated that the effective thermal stress increased as the layer height increased from the surface layer to the substrate, while the thermal strain followed an approximate change rule. In addition, the stress was released from the underlying substrate when the support was removed. Moreover, the largest single axis plane stress was changed from tension to compression from the edge to the center, finally reaching equilibrium. In particular, maximum macro thermal deformation occurred at the printed support structure to the samples, displaying similar results in other locations such as the corners. Finally, the effectiveness of the simulation could be verified from the realistic printed part, which could provide proof for the quality prediction of the part that is actually forming.
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Zeng, Quanren, Yankang Tian, Zhenhai Xu, and Yi Qin. "Simulation of thermal behaviours and powder flow for direct laser metal deposition process." MATEC Web of Conferences 190 (2018): 02001. http://dx.doi.org/10.1051/matecconf/201819002001.
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Laser engineering net-shaping (LENS), based on directed energy deposition (DED), is one of the popular AM technologies for producing fully dense complex metal structural components directly from laser metal deposition without using dies or tooling and hence greatly reduces the lead-time and production cost. However, many factors, such as powder-related and laser-related manufacturing parameters, will affect the final quality of components produced by LENS process, especially the powder flow distribution and thermal history at the substrate. The powder concentration normally determines the density and strength of deposited components; while the thermal behaviours of melt pool mainly determines the cooling rate, residual stress and consequent cracks in deposited components. Trial and errors method is obviously too expensive to afford for diverse applications of different metal materials and various manufacturing input parameters. Numerical simulation of the LENS process will be an effective means to identify reasonable manufacturing parameter sets for producing high quality crack-free components. In this paper, the laser metal powder deposition process of LENS is reported. The gas-powder flow distribution below the deposition nozzle is obtained via CFD simulation. The thermal behaviours of substrate and as-deposited layer/track during the LENS process are investigated by using FEM analysis. Temperature field distributions caused by the moving laser beam and the resultant melt pool on the substrate, are simulated and compared. The research offers a more accurate and practical thermal behaviour model for LENS process, which could be applied to further investigation of the interactions between laser, melt pool and powder particles; it will be particularly useful for manufacturing key components which has more demanding requirement on the components’ functional performance.
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Genna, Silvio, and Gianluca Rubino. "Laser Finishing of Ti6Al4V Additive Manufactured Parts by Electron Beam Melting." Applied Sciences 10, no. 1 (December 25, 2019): 183. http://dx.doi.org/10.3390/app10010183.
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In this work, the feasibility of laser surface finishing of parts obtained by additive manufacturing (AM) was investigated. To this end, a 450 W fiber laser (operating in continuous wave, CW) was adopted to treat the surface of Ti-6Al-4V samples obtained via electron beam melting (EBM). During the tests, different laser energy densities and scanning speeds were used. In order to assess the quality of the treatment, either the as-built or the treated samples were analyzed by means of a three-dimensional (3D) profilometer, digital microscopy, and scanning electron microscopy. Analysis of variance (ANOVA) was performed to check which and how process parameters affected the finishing. The results show that, in the best conditions, the laser treatment reduced surface roughness by about 80%.
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Fritz, Jörg, Ansgar Greshake, Mariana Klementova, Richard Wirth, Lukas Palatinus, Reidar G. Trønnes, Vera Assis Fernandes, Ute Böttger, and Ludovic Ferrière. "Donwilhelmsite, [CaAl4Si2O11], a new lunar high-pressure Ca-Al-silicate with relevance for subducted terrestrial sediments." American Mineralogist 105, no. 11 (November 1, 2020): 1704–11. http://dx.doi.org/10.2138/am-2020-7393.
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Abstract We report on the occurrence of a new high-pressure Ca-Al-silicate in localized shock melt pockets found in the feldspatic lunar meteorite Oued Awlitis 001 and discuss the implications of our discovery. The new mineral crystallized as tiny, micrometer-sized, acicular grains in shock melt pockets of roughly anorthitic bulk composition. Transmission electron microscopy based three-dimensional electron diffraction (3D ED) reveals that the CaAl4Si2O11 crystals are identical to the calcium aluminum silicate (CAS) phase first reported from static pressure experiments. The new mineral has a hexagonal structure, with a space group of P63/mmc and lattice parameters of a = 5.42(1) Å; c = 12.70(3) Å; V = 323(4) Å3; Z = 2. This is the first time 3D ED was applied to structure determination of an extraterrestrial mineral. The International Mineralogical Association (IMA) has approved this naturally formed CAS phase as the new mineral “donwilhelmsite” [CaAl4Si2O11], honoring the U.S. lunar geologist Don E. Wilhelms. On the Moon, donwilhelmsite can form from the primordial feldspathic crust during impact cratering events. In the feldspatic lunar meteorite Oued Awlitis 001, needles of donwilhelmsite crystallized in ~200 mm sized shock melt pockets of anorthositic-like chemical composition. These melt pockets quenched within milliseconds during declining shock pressures. Shock melt pockets in meteorites serve as natural crucibles mimicking the conditions expected in the Earth's mantle. Donwilhelmsite forms in the Earth's mantle during deep recycling of aluminous crustal materials, and is a key host for Al and Ca of subducted sediments in most of the transition zone and the uppermost lower mantle (460–700 km). Donwilhelmsite bridges the gap between kyanite and the Ca-component of clinopyroxene at low pressures and the Al-rich Ca-ferrite phase and Ca-perovskite at high-pressures. In ascending buoyant mantle plumes, at about 460 km depth, donwilhelmsite is expected to break down into minerals such as garnet, kyanite, and clinopyroxene. This process may trigger minor partial melting, releasing a range of incompatible minor and trace elements and contributing to the enriched mantle (EM1 and EM2) components associated with subducted sedimentary lithologies.
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Falcão, R. B., E. Sallica-Leva, D. L. Bayerlein, J. B. Ferreira Neto, and F. J. G. Landgraf. "Obtention of Nb47Ti and Ti13Nb13Zr Alloys Powders by Hydride-Dehydride Process for Additive Manufacturing Applications." Materials Science Forum 1012 (October 2020): 343–48. http://dx.doi.org/10.4028/www.scientific.net/msf.1012.343.
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In this work, the hydride-dehydride process (HDH) parameters to obtain Nb47Ti and Ti13Nb13Zr alloys powders were investigated, aiming the production of orthopedic implants by additive manufacturing (AM). Nb47Ti and Ti13Nb13Zr alloys were previously obtained by electron beam melting furnace (EBMF). During the hydriding step, the alloys were heated at two activation temperatures, 800 and 1000 °C, under constant hydrogen pressure (1.8 bar), for 40 min followed by a controlled cooling rate step (2 °C/min). The hydride alloys were milled in a ring-type mill, for milling times ranging from 2 to 6 min, until to achieve the required particle size range (between 15 and 45 μm). The dehydriding step of the alloys was carried out under high vacuum at 700 °C for times up to 5 h. The alloys treated under distinct HDH steps were characterized by X-ray diffraction, scanning electron microscopy, dynamic image analysis, inert gas fusion and gravimetry. The alloys hydrides (δTiHx phase) were detected in both investigated activation temperatures, with hydrogen (H) contents up to 3.04 and 3.62 wt.% for the Nb47Ti and Ti13Nb13Zr alloys, respectively. During the hydriding step it was also observed a significant increase of nitrogen (N) and oxygen (O) contents regarding he as-cast alloys. The Nb47Ti alloy showed a lower embrittlement degree than the Ti13Nb13Zr alloy, resulting in higher milling times to reach the required particle size distribution. The higher oxygen pick up was observed during the milling step. After the dehydriding step, the HDH powders showed H contents lower than 0.01 wt.%, beside a significant N decreasing. Particles with irregular (or angular) shapes were obtained. However, the particle size was in the required range.
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Król, M., J. Mazurkiewicz, and S. Żołnierczyk. "Optimization and analysis of porosity and roughness in selective laser melting 316L parts." Archives of Materials Science and Engineering 1, no. 90 (March 1, 2018): 5–15. http://dx.doi.org/10.5604/01.3001.0012.0607.
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Purpose: The investigations have been carried out on 316L stainless steel parts fabricated by Selective Laser Melting (SLM) technique. The study aimed to determine the effect of SLM parameters on porosity, hardness, and structure of 316L stainless steel. Design/methodology/approach: The analyses were conducted on 316L stainless steel parts by using AM125 SLM machine by Renishaw. The effects of the different manufacturing process parameters as power output, laser distance between the point’s melted metal powder during additive manufacturing as well as the orientation of the model relative to the laser beam and substrate on porosity, hardness, microstructure and roughness were analysed and optimised. Findings: The surface quality parts using 316L steel with the assumed parameters of the experiment depends on the process parameters used during the SLM technique as well as the orientation of formed walls of the model relative to the substrate and thus the laser beam. The lowest roughness of 316L SLM parts oriented perpendicularly to the substrate was found when 100 W and 20 μm the distance point was utilised. The lowest roughness for part oriented at 60° relatives to the substrate was observed when 125 W and the point distance 50 μm was employed. Practical implications: Stainless steel is one of the most popular materials used for selective laser sintering (SLM) processing to produce nearly fully dense components from 3D CAD models. Reduction of porosity is one of the critical research issues within the additive manufacturing technique SLM, since one of the major cost factors is the post-processing. Originality/value: This manuscript can serve as an aid in understanding the importance of technological parameters on quality and porosity of manufactured AM parts made by SLM technique.
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Lu, Xufei, Miguel Cervera, Michele Chiumenti, Junjie Li, Xianglin Ji, Guohao Zhang, and Xin Lin. "Modeling of the Effect of the Building Strategy on the Thermomechanical Response of Ti-6Al-4V Rectangular Parts Manufactured by Laser Directed Energy Deposition." Metals 10, no. 12 (December 6, 2020): 1643. http://dx.doi.org/10.3390/met10121643.
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Part warpage and residual stress are two of the main challenges for metal additive manufacturing (AM) as they result in lower geometric precision and poor mechanical properties of the products. This work investigates the effect of the building strategy on the heat transfer process and the evolution of the thermally induced mechanical variables in laser directed energy deposition (L-DED) in order to minimize residual stresses and deformations. A 3D finite element (FE) thermo-mechanical model is firstly calibrated through in-situ experiments of rectangular workpieces fabricated by L-DED technology, and, secondly, the coupled thermo-mechanical responses for different process parameters and scanning patterns are discussed in detail. On the calibration stage, the remarkable agreement is achieved between predicted results and experimental data. Regarding the modeling stage, the numerical results indicate that minimization of the part warpage is achieved by reducing the back speed and shortening the scanning lines during the building process. Both residual stress and deformation can be further reduced if preheating the baseplate is added before L-DED.
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Gao, Wang, Shi, Wu, and Takagi. "Characterization of Multitermination CG Flashes Using a 3D Lightning Mapping System (FALMA)." Atmosphere 10, no. 10 (October 16, 2019): 625. http://dx.doi.org/10.3390/atmos10100625.
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We characterized 205 multiple-termination negative cloud-to-ground (CG) lightning flashes that were imaged by the Fast Antenna Lightning Mapping Array (FALMA) in Japan during the summer of 2017. The parameters we used included termination number, termination distance, fork height, return stroke (RS) number, the interval between the first RS of each termination, the shortest time difference between the strokes at different terminations, and the first RS intensities separated by termination occurrence orders. It was found that the multiple-termination flashes (MTFs) had a termination number ranging from 2 to 5, with the majority (148/205) at 2. The termination distance (with high probability) was between 2 and 4 km, with 10 out of 359 MTF termination distances being longer than 10 km. For most MTFs (146/205), their leader forks for different terminations occurred at a height between 4 and 6 km, indicating that the fork process mainly occurred inside the cloud. The RS number of the MTFs ranged from 2 to 18, with an arithmetic mean (AM) value of 5.8. The interval between the first RS of each termination in the MTFs ranged from 0.5 to 965.3 ms, with an AM value of 225.6 ms, while the shortest time difference between the strokes at different terminations had an AM value of 189.6 ms. The intensity of the first stroke in each termination tended to decrease with increasing termination occurrence orders.
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Selakovic, Vesna, Miodrag Colic, Marina Jovanovic, Ranko Raicevic, and Aco Jovicic. "Cerebrospinal fluid and plasma concentration of soluble intercellular adhesion molecule1, vascular cell adhesion molecule1 and endothelial leukocyte adhesion molecule in patients with acute ischemic b." Vojnosanitetski pregled 60, no. 2 (2003): 139–46. http://dx.doi.org/10.2298/vsp0302139s.
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Background. Leukocyte migration into the ischemic area is a complex process controlled by adhesion molecules (AM) in leukocytes and endothelium, by migratory capacity of leukocytes and the presence of hemotaxic agents in the tissue. In this research it was supposed that in the blood and cerebrospinal fluid (CSF) of patients in the acute phase of ischemic brain disease (IBD) there were relevant changes in the concentration of soluble AM (sICAM-1 sVCAM-1 and sE-selectin), that could have been the indicators of the intensity of damaging processes in central nervous system (CNS). Methods. The study included 45 IBD patients, 15 with transient ischemic attack (TIA) 15 with reversible ischemic attack (RIA), and 15 with brain infarction (BI) of both sexes, mean age 66?7. Control group consisted of 15 patients with radicular lesions of discal origin, subjected to diagnostic radiculography without the signs of interruption in the passage of CSF. Changes of selected biochemical parameters were determined in all patients in frame 72 hours since the occurence of an ischemic episode. Concentrations of soluble AM were determined in plasma and CSF by ELISA. Total number of leukocytes (TNL) in peripheral blood was determined by hematological analyzer. Results. The results showed that during the first 72 hrs of IBD significant increases occured in TNL and that the increase was progressive compared to the severeness of the disease. Significant increase of soluble AM concentration was shown in plasma of IBD patients. The increase was highest in BI somewhat lower in RIA and the lowest in TIA patients compared to the control. In CSF concentrations of sICAM-1, sVCAM-1 and sE-selectin demonstrated similar increasing trend as in plasma. Conclusion. TNL, as well as the soluble AM concentrations in plasma and CSF, were increased during the acute IBD phase and progressive in relation to the severeness of the disease, so that they might have been the indicators of CNS inflammatory reaction intensity. Furthermore, the results indicated their role in IBD pathogenesis and offered the possibility of researching the application of antagonists and/or activity modulators of some of them in IBD therapy.
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Galati, Manuela, Oscar Di Mauro, and Luca Iuliano. "Finite Element Simulation of Multilayer Electron Beam Melting for the Improvement of Build Quality." Crystals 10, no. 6 (June 23, 2020): 532. http://dx.doi.org/10.3390/cryst10060532.
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Macroscale modeling plays an essential role in simulating additive manufacturing (AM) processes. However, models at such scales often pay computational time in output accuracy. Therefore, they cannot forecast local quality issues like lack of fusion or surface roughness. For these reasons, this kind of model is never used for process optimization, as it is supposed to work with optimized parameters. In this work, a more accurate but still simple three-dimensional (3D) model is developed to estimate potential faulty process conditions that may cause quality issues or even process failure during the electron beam melting (EBM) process. The model is multilayer, and modeling strategies are developed to have fast and accurate responses. A material state variable allows for the molten material to be represented. That information is used to analyze process quality issues in terms of a lack of fusion and lateral surface roughness. A quiet element approach is implemented to limit the number of elements during the calculation, as well as to simulate the material addition layer by layer. The new material is activated according to a predefined temperature that considers the heat-affected zone. Heat transfer analysis accuracy is comparatively demonstrated with a more accurate literature model. Then, a multilayer simulation validates the model capability in predicting the roughness of a manufactured Ti6Al4V sample. The model capability in predicting a lack of fusion is verified under a critical process condition.
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Alkahari, Mohd Rizal, Tatsuaki Furumoto, Takashi Ueda, and Akira Hosokawa. "Melt Pool and Single Track Formation in Selective Laser Sintering/Selective Laser Melting." Advanced Materials Research 933 (May 2014): 196–201. http://dx.doi.org/10.4028/www.scientific.net/amr.933.196.
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Selective Laser Sintering/Selective Laser Melting (SLS/SLM) is one of Additive Manufacturing (AM) processes that utilize layer by layer powder deposition technique and successive laser beam irradiation based on Computer Aided Design (CAD) data. During laser irradiation on metal powders, melt pool was formed, which then solidified to consolidated structure. Therefore, melt pool is an important behavior that affects the final quality of track formation. The study investigates the melt pool behavior through visualization of the consolidation process during the single track formation on the first layer. In order to understand the transformation process of metal powder to consolidated structure and mechanism involved, high speed camera was used to monitor the process. Yb:fiber laser beam was irradiated on metal powder at maximum power of 150W. The laser processing parameters such as laser power, scan speed and layer thickness were varied in order to investigate their influence on the consolidation process. The result shows the size of melt pool increased with laser power and decreasing with increment in scan speed. Furthermore, with the increase of layer thickness, melt pool formation was unstable with chaotic movement. Significant amount of molten powder splattering was recorded from the melt pool. At high layer thickness also, the molten powder formed spherical shaped and the solidified molten powder failed to wet with the substrate.
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Shaikh, Muhammad Omar, Ching-Chia Chen, Hua-Cheng Chiang, Ji-Rong Chen, Yi-Chin Chou, Tsung-Yuan Kuo, Kei Ameyama, and Cheng-Hsin Chuang. "Additive manufacturing using fine wire-based laser metal deposition." Rapid Prototyping Journal 26, no. 3 (November 18, 2019): 473–83. http://dx.doi.org/10.1108/rpj-04-2019-0110.
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Purpose Using wire as feedstock has several advantages for additive manufacturing (AM) of metal components, which include high deposition rates, efficient material use and low material costs. While the feasibility of wire-feed AM has been demonstrated, the accuracy and surface finish of the produced parts is generally lower than those obtained using powder-bed/-feed AM. The purpose of this study was to develop and investigate the feasibility of a fine wire-based laser metal deposition (FW-LMD) process for producing high-precision metal components with improved resolution, dimensional accuracy and surface finish. Design/methodology/approach The proposed FW-LMD AM process uses a fine stainless steel wire with a diameter of 100 µm as the additive material and a pulsed Nd:YAG laser as the heat source. The pulsed laser beam generates a melt pool on the substrate into which the fine wire is fed, and upon moving the X–Y stage, a single-pass weld bead is created during solidification that can be laterally and vertically stacked to create a 3D metal component. Process parameters including laser power, pulse duration and stage speed were optimized for the single-pass weld bead. The effect of lateral overlap was studied to ensure low surface roughness of the first layer onto which subsequent layers can be deposited. Multi-layer deposition was also performed and the resulting cross-sectional morphology, microhardness, phase formation, grain growth and tensile strength have been investigated. Findings An optimized lateral overlap of about 60-70% results in an average surface roughness of 8-16 µm along all printed directions of the X–Y stage. The single-layer thickness and dimensional accuracy of the proposed FW-LMD process was about 40-80 µm and ±30 µm, respectively. A dense cross-sectional morphology was observed for the multilayer stacking without any visible voids, pores or defects present between the layers. X-ray diffraction confirmed a majority austenite phase with small ferrite phase formation that occurs at the junction of the vertically stacked beads, as confirmed by the electron backscatter diffraction (EBSD) analysis. Tensile tests were performed and an ultimate tensile strength of about 700-750 MPa was observed for all samples. Furthermore, multilayer printing of different shapes with improved surface finish and thin-walled and inclined metal structures with a minimum achievable resolution of about 500 µm was presented. Originality/value To the best of the authors’ knowledge, this is the first study to report a directed energy deposition process using a fine metal wire with a diameter of 100 µm and can be a possible solution to improving surface finish and reducing the “stair-stepping” effect that is generally observed for wires with a larger diameter. The AM process proposed in this study can be an attractive alternative for 3D printing of high-precision metal components and can find application for rapid prototyping in a range of industries such as medical and automotive, among others.
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Cummins, Sharen, Paul W. Cleary, Gary Delaney, Arden Phua, Matthew Sinnott, Dayalan Gunasegaram, and Chris Davies. "A Coupled DEM/SPH Computational Model to Simulate Microstructure Evolution in Ti-6Al-4V Laser Powder Bed Fusion Processes." Metals 11, no. 6 (May 24, 2021): 858. http://dx.doi.org/10.3390/met11060858.
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A new multi-stage three-dimensional transient computational model to simulate powder bed fusion (L-PBF) additive manufacturing (AM) processes is presented. The model uses the discrete element method (DEM) for powder flow simulation, an extended smoothed particle hydrodynamics (SPH) for melt pool dynamics and a semi-empirical microstructure evolution strategy to simulate the evolving temperature and microstructure of non-spherical Ti-6Al-4V powder grains undergoing L-PBF. The highly novel use of both DEM and SPH means that varied physics such as collisions between non-spherical powder grains during the coating process and heat transfer, melting, solidification and microstructure evolution during the laser fusion process can be simulated. The new capability is demonstrated by applying a complex representative laser scan pattern to a single-layer Ti-6Al-4V powder bed. It is found that the fast cooling rate primarily leads to a transition between the β and α martensitic phases. A minimal production of the α Widmanstatten phase at the outer edge of the laser is also noted due to an in situ heat treatment effect of the martensitic grains near the laser. This work demonstrates the potential of the coupled DEM/SPH computational model as a realistic tool to investigate the effect of process parameters such as powder morphology, laser scan speed and power characteristics on the Ti-6Al-4V powder bed microstructure.
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Stalnaker, D. O., and J. L. Turner. "Vehicle and Course Characterization Process for Indoor Tire Wear Simulation." Tire Science and Technology 30, no. 2 (April 1, 2002): 100–121. http://dx.doi.org/10.2346/1.2135248.
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Abstract An empirical methodology is described for separately characterizing vehicles and road courses for subsequent combination to predict tire force histories in tire use or testing. By building a library of vehicle and wear course characterizations, indoor wear test simulations can be selectively constructed by using any combination of “virtual” test vehicles and wear courses. A reliable transient record of vertical, lateral and fore-aft forces and inclination angles can be generated and supplied to drive the indoor wear tire loading fixture. Vehicle characterization involves mapping the basic dynamic load transfer behavior over a range of acceleration, deceleration and cornering maneuvers. A unique indoor vehicle test facility is described for efficiently capturing the tire forces and inclination angles during various maneuvers. All four tire positions can be characterized. Vehicle center of gravity (CG) accelerations and speeds are also recorded during indoor testing. An alternative to experimental measurements is the use of a vehicle computer model for mapping the basic dynamic load transfer behavior. Empirical equations relating vehicle kinematics to tire forces and inclination angles have been developed and are presented. A method of utilizing these equations together with outdoor wear course measurements for predicting transient tire force histories is presented. The method is demonstrated and validated with several vehicle case studies. The tire force component of a wear course can be characterized by measurement of a few parameters: the vehicle CG accelerations and the longitudinal velocity. Course characterization is illustrated using the Department of Transportation's Uniform Tire Quality Grading wear course in the San Angelo, TX area. The full 650 km course was characterized and combined with the laboratory characterization of a 1997 Pontiac Grand Am. Four 650 km drive files were created, one for each tire position, for an indoor wear machine. These consisted of five time-based parameters: radial load, lateral force, wheel torque (acceleration, deceleration forces), inclination angle, and velocity. By sequencing a tire through these four drive files, it was “rotated” as it would have been on the actual vehicle. Examples of tire wear rates and irregular wear are shown for a number of tire constructions, comparing the indoor to the outdoor results. Good correlation was achieved. This simulation technique permits the tire force spectrum of quite complex and lengthy routes to be accurately reproduced in the precisely controlled environment of the laboratory. Each cornering maneuver, each braking and acceleration event, every hill and town can be reproduced in real-time. Only by combining the specific vehicle dynamics of a given vehicle with that of a specific wear route can tire wear be accurately simulated. This tire-vehicle system simulation methodology is referred to as a TS-Sim model.
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Proctor, Devin. "Policing the Fluff: The Social Construction of Scientistic Selves in Otherkin Facebook Groups." Engaging Science, Technology, and Society 4 (September 29, 2018): 485. http://dx.doi.org/10.17351/ests2018.252.
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The Otherkin are a group of people who identify as other-than-human. Primarily gathering in online spaces, they discuss and debate the origins and parameters of this identification and try to make sense of their extraordinary experiences. This article traces how the Otherkin deploy scientific facts and theories during this process, arriving at Otherkin science, a carefully curated compilation of abstract physics, psychology, metaphysics, and ancient belief that renders other-than-human identification thinkable in a contemporary Western paradigm. Drawing on five years of ethnographic engagement with the Otherkin, this article examines this social knowledge construction through the processes of “questioning” and “grilling” on Otherkin Facebook groups. In continuously negotiating their own identities through scientific reasoning, they create what I am calling scientistic selves—frameworks of identification created by lay scientists whose adherence to specific scientific facts and theories is fundamental to their continued existence.
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Sharma, Neha, Soheila Aghlmandi, Shuaishuai Cao, Christoph Kunz, Philipp Honigmann, and Florian M. Thieringer. "Quality Characteristics and Clinical Relevance of In-House 3D-Printed Customized Polyetheretherketone (PEEK) Implants for Craniofacial Reconstruction." Journal of Clinical Medicine 9, no. 9 (August 31, 2020): 2818. http://dx.doi.org/10.3390/jcm9092818.
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Additive manufacturing (AM) of patient-specific implants (PSIs) is gradually moving towards in-house or point-of-care (POC) manufacturing. Polyetheretherketone (PEEK) has been used in cranioplasty cases as a reliable alternative to other alloplastic materials. As only a few fused filament fabrication (FFF) printers are suitable for in-house manufacturing, the quality characteristics of the implants fabricated by FFF technology are still under investigated. This paper aimed to investigate PEEK PSIs fabricated in-house for craniofacial reconstruction, discussing the key challenges during the FFF printing process. Two exemplary cases of class III (Group 1) and class IV (Group 2) craniofacial defects were selected for the fabrication of PEEK PSIs. Taguchi’s L9 orthogonal array was selected for the following nonthermal printing process parameters, i.e., layer thickness, infill rate, number of shells, and infill pattern, and an assessment of the dimensional accuracy of the fabricated implants was made. The root mean square (RMS) values revealed higher deviations in Group 1 PSIs (0.790 mm) compared to Group 2 PSIs (0.241 mm). Horizontal lines, or the characteristic FFF stair-stepping effect, were more perceptible across the surface of Group 1 PSIs. Although Group 2 PSIs revealed no discoloration, Group 1 PSIs displayed different zones of crystallinity. These results suggest that the dimensional accuracy of PSIs were within the clinically acceptable range; however, attention must be paid towards a requirement of optimum thermal management during the printing process to fabricate implants of uniform crystallinity.
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Els, Johan, Michele Truscott, Kobus van der Walt, and Gerrie Booysen. "Establishing the Optimal Process Parameters for the Laser Sintering of Ti64 for Layer Thicknesses of 15 μm and 30 μm and Validation of a Melt Pool Simulation Model." Advanced Materials Research 1019 (October 2014): 254–58. http://dx.doi.org/10.4028/www.scientific.net/amr.1019.254.
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Direct Metal Laser Sintering (DMLS) is a layer-by-layer Additive Manufacturing (AM) process that creates physical metal parts from three dimensional Computer Aided Design (CAD) data. For DMLS to be generally accepted by industry as a manufacturing technology, high mechanical integrity of final components needs to be demonstrated. Mechanical properties of manufactured components are directly affected by the quality of each individual laser sintered track of each consecutive layer. In this study, the optimal ratio of laser power and scanning speed on single tracks is determined for Titanium-6Al-4V powder on an EOSINT M270 DMLS machine for a layer thickness that varies between 15 μm and 30 μm. Two different laser powers, namely 150 W and 170 W were considered. Scanning speeds varied between 600 mm/s to 2000 mm/s with 200 mm/s intervals. The most stable tracks resulted from high laser power, slow scanning speed and thin powder distribution. The empirical data were compared to a melt pool width prediction program, which was found to underestimate track width at all scanning speeds and re-melting depth at low scanning speeds. Further, it was found that decreased powder thickness can be used with an increased scanning speed and high laser power. This strategy may be used to increase surface quality. The penetration data during fusion of the tracks onto the building platform further validates the quality of each sintered track.
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Mirkoohi, Elham, Daniel E. Seivers, Hamid Garmestani, and Steven Y. Liang. "Heat Source Modeling in Selective Laser Melting." Materials 12, no. 13 (June 26, 2019): 2052. http://dx.doi.org/10.3390/ma12132052.
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Selective laser melting (SLM) is an emerging additive manufacturing (AM) technology for metals. Intricate three-dimensional parts can be generated from the powder bed by selectively melting the desired location of the powders. The process is repeated for each layer until the part is built. The necessary heat is provided by a laser. Temperature magnitude and history during SLM directly determine the molten pool dimensions, thermal stress, residual stress, balling effect, and dimensional accuracy. Laser-matter interaction is a crucial physical phenomenon in the SLM process. In this paper, five different heat source models are introduced to predict the three-dimensional temperature field analytically. These models are known as steady state moving point heat source, transient moving point heat source, semi-elliptical moving heat source, double elliptical moving heat source, and uniform moving heat source. The analytical temperature model for all of the heat source models is solved using three-dimensional differential equations of heat conduction with different approaches. The steady state and transient moving heat source are solved using a separation of variables approach. However, the rest of the models are solved by employing Green’s functions. Due to the high temperature in the presence of the laser, the temperature gradient is usually high which has a substantial impact on thermal material properties. Consequently, the temperature field is predicted by considering the temperature sensitivity thermal material properties. Moreover, due to the repeated heating and cooling, the part usually undergoes several melting and solidification cycles, and this physical phenomenon is considered by modifying the heat capacity using latent heat of melting. Furthermore, the multi-layer aspect of the metal AM process is considered by incorporating the temperature history from the previous layer since the interaction of the layers have an impact on heat transfer mechanisms. The proposed temperature field models based on different heat source approaches are validated using experimental measurement of melt pool geometry from independent experimentations. A detailed explanation of the comparison of models is also provided. Moreover, the effect of process parameters on the balling effect is also discussed.
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Scharrer, Manuel, Katharina Sandritter, Benjamin F. Walter, Udo Neumann, and Gregor Markl. "Formation of native arsenic in hydrothermal base metal deposits and related supergene U6+ enrichment: The Michael vein near Lahr, SW Germany." American Mineralogist 105, no. 5 (May 1, 2020): 727–44. http://dx.doi.org/10.2138/am-2020-7062.
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Abstract Native arsenic is an occasional ore mineral in some hydrothermal base metal deposits. Its rarity (compared to pyrite, arsenopyrite, galena, sphalerite, or chalcopyrite, for example) is surprising, as arsenic is a common constituent of upper crustal fluids. Hence, the conditions of formation must be quite special to precipitate native arsenic. An ideal location to investigate the formation of native As and to explore the parameters constraining its crystallization is the Michael vein near Lahr, Schwarzwald, southwest (SW) Germany. Here, galena, sphalerite, and native arsenic are the most abundant ore minerals. The two important ore stages comprise (1) galena-barite and (2) sphalerite-native arsenic-quartz, the latter with a general mineral succession of pyrite → sphalerite ± jordanite-gratonite solid solution → galena → native As. The native arsenic-bearing mineralization formed by cooling of an at least 130 °C hot saline fluid accompanied by a reduction due to the admixing of a sulfide-bearing fluid. Thermodynamic calculations reveal that for the formation of native arsenic, reduced conditions in combination with very low concentrations of the transition metals Fe, Co, and Ni, as well as low sulfide concentrations, are essential. “Typical” hydrothermal fluids do not fulfill these criteria, as they typically can contain significant amounts of Fe and sulfide. This results in the formation of arsenides, sulfarsenides, or As-bearing sulfides instead of native arsenic. Very minor amounts of pyrite, sulfarsenides, and arsenides record the very low concentrations of Fe, Co, and Ni present in the ore-forming fluid. High concentrations of aqueous Zn and Pb lead to early saturation of sphalerite and galena that promoted native arsenic precipitation by decreasing the availability of sulfide and hence suppressing realgar formation. Interestingly, native arsenic in the Michael vein acted as a trap for uranium during supergene weathering processes. Infiltrating oxidizing, U+VI-bearing fluids from the host lithologies reacted under ambient conditions with galena and native arsenic, forming a variety of U+VI (±Pb)-bearing arsenates such as hügelite, hallimondite, zeunerite, heinrichite, or novacekite together with U-free minerals like mimetite or anglesite. Some parts of the vein were enriched to U concentrations of up to 1 wt% by this supergene process. Reduced (hypogene) uranium phases like uraninite were never observed.