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Sujatha, M. N., i Vijeshree Kadiya. "A subcell based approach for enhancing the absorption bandwidth of microwave absorbers using printed periodic metallic geometries". Engineering Science and Technology, an International Journal 22, nr 1 (luty 2019): 385–90. http://dx.doi.org/10.1016/j.jestch.2018.08.008.
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Gáspár, Igor, i Réka Neczpál. "Testing of 3D Printed Turbulence Promoters for Membrane Filtration". Periodica Polytechnica Chemical Engineering 64, nr 3 (25.05.2020): 371–76. http://dx.doi.org/10.3311/ppch.15211.
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Membrane filtration process can be intensified by using static mixers inside tubular membranes. Most of commercial static mixers are optimized for mixing fluids, not for membrane filtration. We have developed new turbulence promoter geometries designed for intensification of permeate flux and retention without significant pressure drop along the membrane. In previous experiments, we used metallic turbulence promoters, but in this work, FDM 3D printing technology was used to create these improved geometries, which are new in membrane filtration and they have the same geometry as existing metallic versions. New 3D printed objects were tested with filtration of stable oil-in-water emulsion. Our experiments proved that 3D printed static mixers might be as effective as metallic versions. The effect on initial flux and retention of oil was very similar. Pressure drop along membrane was slightly higher (but significantly lower from pressure drop along the membrane resulted by commercial static mixers, designed only for mixing fluids). Higher pressure drop may be the result of rougher surface due the layer-technology of 3D printing. This negative effect can be reduced by using a smaller nozzle (which will produce smaller layers) or smoothing the surface. PLA is material easier for printing, but from these two materials, PETG is a better choice due its higher operating temperature and better water-resist properties too.
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Zhao, Zijian, Guang Yang i Kun Zhao. "3D Printing of Mg-Based Bulk Metallic Glasses with Proper Laser Power and Scanning Speed". Metals 12, nr 8 (5.08.2022): 1318. http://dx.doi.org/10.3390/met12081318.
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Additive manufacturing allows for the fabrication of large-sized metallic glasses with complex geometries, which overcomes the size limitation due to limited glass-forming ability. To investigate the effect of synthesis parameters on the Mg-based metallic glasses, Mg65Cu20Zn5Y10 was fabricated by laser-based powder bed fusion under different scanning speeds and laser powers. For high energy density, the samples showed severe crystallization and macrocracks, while for low energy density, the samples contained pore defects and unfused powders. Three-dimensionally printed samples were used for the compression test, and the mechanical properties were analyzed by Weibull statistics. Our work identifies proper parameters for 3D printing Mg-based metallic glasses, which provide a necessary, fundamental basis for the fabrication of 3D-printed Mg-based metallic glass materials with improved performance.
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Wang, Jun, Rahul Rai i Jason N. Armstrong. "Investigation of compressive deformation behaviors of cubic periodic cellular structural cubes through 3D printed parts and FE simulations". Rapid Prototyping Journal 26, nr 3 (17.11.2019): 459–72. http://dx.doi.org/10.1108/rpj-03-2019-0069.
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Purpose This paper aims to clarify the relationship between mechanical behaviors and the underlying geometry of periodic cellular structures. Particularly, the answer to the following research question is investigated: Can seemingly different geometries of the repeating unit cells of periodic cellular structure result in similar functional behaviors? The study aims to cluster the geometry-functional behavior relationship into different categories. Design/methodology/approach Specifically, the effects of the geometry on the compressive deformation (mechanical behavior) responses of multiple standardized cubic periodic cellular structures (CPCS) at macro scales are investigated through both physical tests and finite element simulations of three-dimensional (3D) printed samples. Additionally, these multiple CPCS can be further nested into the shell of 3D models of various mechanical domain parts to demonstrate the influence of their geometries in practical applications. Findings The paper provides insights into how different CPCS (geometrically different unit cells) influence their compressive deformation behaviors. It suggests a standardized strategy for comparing mechanical behaviors of different CPCS. Originality/value This paper is the first work in the research domain to investigate if seemingly different geometries of the underlying unit cell can result in similar mechanical behaviors. It also fulfills the need to infill and lattify real functional parts with geometrically complex unit cells. Existing work mainly focused on simple shapes such as basic trusses or cubes with spherical holes.
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Su, Huanhuan, Shan Wu, Yuhan Yang, Qing Leng, Lei Huang, Junqi Fu, Qianjin Wang, Hui Liu i Lin Zhou. "Surface plasmon polariton–enhanced photoluminescence of monolayer MoS2 on suspended periodic metallic structures". Nanophotonics 10, nr 2 (24.11.2020): 975–82. http://dx.doi.org/10.1515/nanoph-2020-0545.
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AbstractPlasmonic nanostructures have garnered tremendous interest in enhanced light–matter interaction because of their unique capability of extreme field confinement in nanoscale, especially beneficial for boosting the photoluminescence (PL) signals of weak light–matter interaction materials such as transition metal dichalcogenides atomic crystals. Here we report the surface plasmon polariton (SPP)-assisted PL enhancement of MoS2 monolayer via a suspended periodic metallic (SPM) structure. Without involving metallic nanoparticle–based plasmonic geometries, the SPM structure can enable more than two orders of magnitude PL enhancement. Systematic analysis unravels the underlying physics of the pronounced enhancement to two primary plasmonic effects: concentrated local field of SPP enabled excitation rate increment (45.2) as well as the quantum yield amplification (5.4 times) by the SPM nanostructure, overwhelming most of the nanoparticle-based geometries reported thus far. Our results provide a powerful way to boost two-dimensional exciton emission by plasmonic effects which may shed light on the on-chip photonic integration of 2D materials.
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Sangiorgio, Valentino, Fabio Parisi, Francesco Fieni i Nicola Parisi. "The New Boundaries of 3D-Printed Clay Bricks Design: Printability of Complex Internal Geometries". Sustainability 14, nr 2 (6.01.2022): 598. http://dx.doi.org/10.3390/su14020598.
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The building construction sector is undergoing one of the most profound transformations towards the digital transition of production. In recent decades, the advent of a novel technology for the 3D printing of clay opened up new sustainable possibilities in construction. Some architectural applications of 3D-printed clay bricks with simple internal configurations are being developed around the world. On the other hand, the full potential of 3D-printed bricks for building production is still unknown. Scientific studies about the design and printability of 3D-printed bricks exploiting complex internal geometries are completely missing in the related literature. This paper explores the new boundaries of 3D-printed clay bricks realized with a sustainable extrusion-based 3D clay printing process by proposing a novel conception, design, and analysis. In particular, the proposed methodological approach includes: (i) conception and design; (ii) parametric modeling; (iii) simulation of printability; and (iv) prototyping. The new design and conception aim to fully exploit the potential of 3D printing to realize complex internal geometry in a 3D-printed brick. To this aim, the research investigates the printability of internal configuration generated by using geometries with well-known remarkable mechanical properties, such as periodic minimal surfaces. In conclusion, the results are validated by a wide prototyping campaign.
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Agyapong, Johnson N., Bo Van Durme, Sandra Van Vlierberghe i James H. Henderson. "Surface Functionalization of 4D Printed Substrates Using Polymeric and Metallic Wrinkles". Polymers 15, nr 9 (28.04.2023): 2117. http://dx.doi.org/10.3390/polym15092117.
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Wrinkle topographies have been studied as simple, versatile, and in some cases biomimetic surface functionalization strategies. To fabricate surface wrinkles, one material phenomenon employed is the mechanical-instability-driven wrinkling of thin films, which occurs when a deforming substrate produces sufficient compressive strain to buckle a surface thin film. Although thin-film wrinkling has been studied on shape-changing functional materials, including shape-memory polymers (SMPs), work to date has been primarily limited to simple geometries, such as flat, uniaxially-contracting substrates. Thus, there is a need for a strategy that would allow deformation of complex substrates or 3D parts to generate wrinkles on surfaces throughout that complex substrate or part. Here, 4D printing of SMPs is combined with polymeric and metallic thin films to develop and study an approach for fiber-level topographic functionalization suitable for use in printing of arbitrarily complex shape-changing substrates or parts. The effect of nozzle temperature, substrate architecture, and film thickness on wrinkles has been characterized, as well as wrinkle topography on nuclear alignment using scanning electron microscopy, atomic force microscopy, and fluorescent imaging. As nozzle temperature increased, wrinkle wavelength increased while strain trapping and nuclear alignment decreased. Moreover, with increasing film thickness, the wavelength increased as well.
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Lee, Sung-Ho, Sang-Yoon Gee, Chul Kang i Chul-Sik Kee. "Terahertz Wave Transmission Properties of Metallic Periodic Structures Printed on a Photo-paper". Journal of the Optical Society of Korea 14, nr 3 (25.09.2010): 282–85. http://dx.doi.org/10.3807/josk.2010.14.3.282.
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Kim, Jiho, i Dong-Jin Yoo. "3D printed compact heat exchangers with mathematically defined core structures". Journal of Computational Design and Engineering 7, nr 4 (7.04.2020): 527–50. http://dx.doi.org/10.1093/jcde/qwaa032.
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Abstract This paper describes a new design method for generating a compact heat exchanger (CHX) computational model consisting of triply periodic minimal surface (TPMS) core structures. These TPMS-based core structures are not easy to design using existing CAD systems, especially in the case of CHXs with complex 3D geometries. In this paper, we introduce a novel CHXs design strategy based on the calculation of volumetric distance fields (VDFs). All geometric components, including TPMS-based core structure, heat exchanger exterior shape, and a set of parts for inlet and outlet, are expressed as VDFs in a given design domain. This VDF-based geometric components description allows for the computationally efficient design of a complex-shaped CHX computational model with high levels of geometric complexity. In conjunction with several TPMS-based CHX prototypes built with additive manufacturing (AM) technologies, we describe and discuss the design and manufacturing results for a wide range of CHXs with various geometries to validate the effectiveness of the newly proposed design method. Besides, by examining the heat transfer performance experimental data, we show that the innovative CHX production method using the combination of VDF-based Boolean operations, TPMS-based core structures, and AM technologies proposed in this paper can create an ultra-efficient CHX while maintaining an allowable pressure drop.
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Zhai, Guohua, Yong Cheng, Qiuyan Yin, Shouzheng Zhu i Jianjun Gao. "Uniplanar Millimeter-Wave Log-Periodic Dipole Array Antenna Fed by Coplanar Waveguide". International Journal of Antennas and Propagation 2013 (2013): 1–5. http://dx.doi.org/10.1155/2013/430618.
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A uniplanar millimeter-wave broadband printed log-periodic dipole array (PLPDA) antenna fed by coplanar waveguide (CPW) is introduced. This proposed structure consists of several active dipole elements, feeding lines, parallel coupled line, and the CPW, which are etched on a single metallic layer of the substrate. The parallel coupled line can be optimized to act as a transformer between the CPW and the PLPDA antenna. Meanwhile, this transform performs the task of a balun to achieve a wideband, low cost, low loss, simple directional antenna. The uniplanar nature makes the antenna suitable to be integrated into modern printed communication circuits, especially the monolithic millimeter-wave integrated circuits (MMIC). The antenna has been carefully examined and measured to present the return loss, far-field patterns, and antenna gain.
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Legett, Shelbie A., Xavier Torres, Andrew M. Schmalzer, Adam Pacheco, John R. Stockdale, Samantha Talley, Tom Robison i Andrea Labouriau. "Balancing Functionality and Printability: High-Loading Polymer Resins for Direct Ink Writing". Polymers 14, nr 21 (1.11.2022): 4661. http://dx.doi.org/10.3390/polym14214661.
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Although direct ink writing (DIW) allows the rapid fabrication of unique 3D printed objects, the resins—or “inks”—available for this technique are in short supply and often offer little functionality, leading to the development of new, custom inks. However, when creating new inks, the ability of the ink to lead to a successful print, or the “printability,” must be considered. Thus, this work examined the effect of filler composition/concentration, printing parameters, and lattice structure on the printability of new polysiloxane inks incorporating high concentrations (50–70 wt%) of metallic and ceramic fillers as well as emulsions. Results suggest that strut diameter and spacing ratio have the most influence on the printability of DIW materials and that the printability of silica- and metal-filled inks is more predictable than ceramic-filled inks. Additionally, higher filler loadings and SC geometries led to stiffer printed parts than lower loadings and FCT geometries, and metal-filled inks were more thermally stable than ceramic-filled inks. The findings in this work provide important insights into the tradeoffs associated with the development of unique and/or multifunctional DIW inks, printability, and the final material’s performance.
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Dallacasa, Valerio. "Diffraction Effects in the Propagation of Radiation in Polarizable Layers". Journal of Nanoscience and Nanotechnology 8, nr 2 (1.02.2008): 595–601. http://dx.doi.org/10.1166/jnn.2008.d084.
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The very low transmission of light through holes smaller than the wavelength has been found to be enhanced for subwavelength apertures in metallic surfaces with periodic corrugations. This effect has been attributed to the interaction of light with surface plasmons. Similar effects obtained subsequently for non-metallic surfaces have been attributed to evanescent waves on the surface produced by the diffracted Bloch waves from different points in the array. We present an exact solution of Maxwell's equations in the discrete dipole approximation (DDA) for a periodic array of polarizable point dipoles in a layer. Metallic as well as non metallic layers are described. When the wavelength is smaller than the lattice period there is a Bragg's scattered wave, while for subwavelength conditions an evanescent wave on the surface appears. The transmission/reflection coefficients are found to oscillate as a function of frequency, with resonances occurring in a broad range of frequencies depending on the polarizability, at which the evanescent field is enhanced. A detailed study is presented for nanostructured arrays. We find that this model agrees with features observed in experiments through hole arrays supporting the role played by diffraction during light transmission through such arrays without invoking surface plasmons and providing a base to analyze more complex geometries.
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Goussetis, G., A. P. Feresidis i J. C. Vardaxoglou. "Tailoring the AMC and EBG Characteristics of Periodic Metallic Arrays Printed on Grounded Dielectric Substrate". IEEE Transactions on Antennas and Propagation 54, nr 1 (styczeń 2006): 82–89. http://dx.doi.org/10.1109/tap.2005.861575.
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Sugino, Christopher, Romain Gerbe, Ehren Baca, Charles Reinke, Massimo Ruzzene, Alper Erturk i Ihab El-kady. "Machined phononic crystals to block high-order Lamb waves and crosstalk in through-metal ultrasonic communication systems". Applied Physics Letters 120, nr 19 (9.05.2022): 191705. http://dx.doi.org/10.1063/5.0083380.
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For systems that require complete metallic enclosures (e.g., containment buildings for nuclear reactors), it is impossible to access interior sensors and equipment using standard electromagnetic techniques. A viable way to communicate and supply power through metallic barriers is the use of elastic waves and ultrasonic transducers, introducing several design challenges that must be addressed. Specifically, the use of multiple communication channels on the same enclosure introduces an additional mechanism for signal crosstalk between channels: guided waves propagating in the barrier between channels. This work numerically and experimentally investigates a machined phononic crystal to block MHz Lamb wave propagation between ultrasonic communication channels, greatly reducing wave propagation and the resulting crosstalk voltage. Blind grooves are machined into one or both sides of a metallic barrier to introduce a periodic unit cell, greatly altering the guided wave dispersion in the barrier. Numerical simulations are used to determine a set of groove geometries for testing, and experiments were performed to characterize the wave-blocking performance of each design. The best-performing design was tested using piezoelectric transducers bonded to the barrier, showing a 14.4 dB reduction in crosstalk voltage. The proposed periodic grooving method is a promising technique for completely isolating ultrasonic power/data transfer systems operating in a narrow frequency range.
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Felix, Levi C., Vladimir Gaál, Cristiano F. Woellner, Varlei Rodrigues i Douglas S. Galvao. "Mechanical Properties of Diamond Schwarzites: From Atomistic Models to 3D-Printed Structures". MRS Advances 5, nr 33-34 (2020): 1775–81. http://dx.doi.org/10.1557/adv.2020.175.
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ABSTRACTTriply Periodic Minimal Surfaces (TPMS) possess locally minimized surface area under the constraint of periodic boundary conditions. Different families of surfaces were obtained with different topologies satisfying such conditions. Examples of such families include Primitive (P), Gyroid (G) and Diamond (D) surfaces. From a purely mathematical subject, TPMS have been recently found in materials science as optimal geometries for structural applications. Proposed by Mackay and Terrones in 1991, schwarzites are 3D crystalline porous carbon nanocrystals exhibiting a TPMS-like surface topology. Although their complex topology poses serious limitations on their synthesis with conventional nanoscale fabrication methods, such as Chemical Vapour Deposition (CVD), schwarzites can be fabricated by Additive Manufacturing (AM) techniques, such as 3D Printing. In this work, we used an optimized atomic model of a schwarzite structure from the D family (D8bal) to generate a surface mesh that was subsequently used for 3D-printing through Fused Deposition Modelling (FDM). This D schwarzite was 3D-printed with thermoplastic PolyLactic Acid (PLA) polymer filaments. Mechanical properties under uniaxial compression were investigated for both the atomic model and the 3D-printed one. Fully atomistic Molecular Dynamics (MD) simulations were also carried out to investigate the uniaxial compression behavior of the D8bal atomic model. Mechanical testings were performed on the 3D-printed schwarzite where the deformation mechanisms were found to be similar to those observed in MD simulations. These results are suggestive of a scale-independent mechanical behavior that is dominated by structural topology.
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Al-Ketan, Oraib, Reza Rowshan i Rashid K. Abu Al-Rub. "Topology-mechanical property relationship of 3D printed strut, skeletal, and sheet based periodic metallic cellular materials". Additive Manufacturing 19 (styczeń 2018): 167–83. http://dx.doi.org/10.1016/j.addma.2017.12.006.
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Nitoi, Alexandra, Mihai Alin Pop, Ting Ting Peng, Tibor Bedő, Sorin Ion Munteanu, Ioana Ghiuta i Daniel Munteanu. "Build Orientation Influence on some Mechanical Properties of 3D-Printed Polyamide Specimens". Advanced Engineering Forum 34 (październik 2019): 3–9. http://dx.doi.org/10.4028/www.scientific.net/aef.34.3.
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Additive manufacturing [AM] is a type of production technology characterized by the additive nature of stacking and unifying individual layers, with the main advantage that parts with complex geometries can easily be obtained, compared to conventional production methods. Due to its working principle, i.e. stacking layers, obtained by melting and solidification, the mechanical characteristics of the built part might be influenced by the build orientation chosen for the specific part. The mechanical behavior, cyclic deformation and fatigue behaviors of additively manufactured metallic parts as compared to their counterparts obtained by conventional processing technologies was reported to be highly dependent on the build orientation. The aim of this study was to assess whether the build orientation will have an impact on the mechanical properties of parts built by Selective Laser Sintering, using polyamide powder as raw material. Samples were built at various inclination degrees, and were further tested in terms of bending, compressive, impact and hardness tests. It was observed that the build orientation has a significant effect on the mechanical properties of parts additively manufactured from polyamide, compared to the behavior presented on the technical sheet of the material, provided by the manufacturer. Keywords: additive manufacturing, mechanical properties, build orientation, Selective Laser Sintering
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Liu, Yuchun, Swee Leong Sing, Rebecca Xin En Lim, Wai Yee Yeong i Bee Tin Goh. "Preliminary Investigation on the Geometric Accuracy of 3D Printed Dental Implant Using a Monkey Maxilla Incisor Model". International Journal of Bioprinting 8, nr 1 (28.01.2022): 476. http://dx.doi.org/10.18063/ijb.v8i1.476.
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Additive manufacturing has proven to be a viable alternative to conventional manufacturing methodologies for metallic implants due to its capability to customize and fabricate novel and complex geometries. Specific to its use in dental applications, various groups have reported successful outcomes for customized root-analog dental implants in preclinical and clinical studies. However, geometrical accuracy of the fabricated samples has never been analyzed. In this article, we studied the geometric accuracy of a 3D printed titanium dental implant design against the tooth root of the monkey maxilla incisor. Monkey maxillas were scanned using cone-beam computed tomography, then segmentation of the incisor tooth roots was performed before the fabrication of titanium dental implants using a laser powder bed fusion (PBF) process. Our results showed 68.70% ± 5.63 accuracy of the 3D printed dental implant compared to the actual tooth (n = 8), where main regions of inaccuracies were found at the tooth apex. The laser PBF fabrication process of the dental implants showed a relatively high level of accuracy of 90.59% ± 4.75 accuracy (n = 8). Our eventual goal is to develop an accurate workflow methodology to support the fabrication of patient-specific 3D-printed titanium dental implants that mimic patients’ tooth anatomy and fit precisely within the socket upon tooth extraction. This is essential for promoting primary stability and osseointegration of dental implants in the longer term.
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Ma, Quoc-Phu, Jakub Mesicek, Frantisek Fojtik, Jiri Hajnys, Pavel Krpec, Marek Pagac i Jana Petru. "Residual Stress Build-Up in Aluminum Parts Fabricated with SLM Technology Using the Bridge Curvature Method". Materials 15, nr 17 (1.09.2022): 6057. http://dx.doi.org/10.3390/ma15176057.
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In metal 3D printing with Selective Laser Melting (SLM) technology, due to large thermal gradients, the residual stress (RS) distribution is complicated to predict and control. RS can distort the shape of the components, causing severe failures in fabrication or functionality. Thus, several research papers have attempted to quantify the RS by designing geometries that distort in a predictable manner, including the Bridge Curvature Method (BCM). Being different from the existing literature, this paper provides a new perspective of the RS build-up in aluminum parts produced with SLM using a combination of experiments and simulations. In particular, the bridge samples are printed with AlSi10Mg, of which the printing process and the RS distribution are experimentally assessed with the Hole Drilling Method (HDM) and simulated using ANSYS and Simufact Additive. Subsequently, on the basis of the findings, suggestions for improvements to the BCM are made. Throughout the assessment of BCM, readers can gain insights on how RS is built-up in metallic 3D-printed components, some available tools, and their suitability for RS prediction. These are essential for practitioners to improve the precision and functionality of SLM parts should any post-subtractive or additive manufacturing processes be employed.
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Nguyen, Lan. "A MIMO Antenna with Enhanced Gain using Metasurface". Applied Computational Electromagnetics Society 36, nr 4 (10.05.2021): 458–64. http://dx.doi.org/10.47037/2020.aces.j.360412.
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This paper proposes a new metasurface to improve gain for dipole antenna. The antenna includes two sets of two elements (1 x 2), the integrated J shaped baluns, five metasurface cells (each metasurface cell consists of 5 periodic metallic plates printed on a thin low-cost FR4 substrate) for four antenna elements and the antenna is supplied by two T-junction power dividers. The metasurface is designed to operate as reflection surface. The antenna is designed based on RT5880 and witnesses an overall size of 140 x 37 x 35.075 mm3 (2.7λ x 0.71λ x 0.67λ at 5.8 GHz), an isolation of approximately 28 dB, a peak gain of 9.5 dBi, and a radiation efficiency of 84%.
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Nóbrega, Clarissa de Lucena, Marcelo Ribeiro da Silva, Paulo Henrique da Fonseca Silva, Adaildo Gomes D’Assunção i Gláucio Lima Siqueira. "Simple, Compact, and Multiband Frequency Selective Surfaces Using Dissimilar Sierpinski Fractal Elements". International Journal of Antennas and Propagation 2015 (2015): 1–5. http://dx.doi.org/10.1155/2015/614780.
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This paper presents a design methodology for frequency selective surfaces (FSSs) using metallic patches with dissimilar Sierpinski fractal elements. The transmission properties of the spatial filters are investigated for FSS structures composed of two alternately integrated dissimilar Sierpinski fractal elements, corresponding to fractal levelsk=1, 2, and 3. Two FSS prototypes are fabricated and measured in the range from 2 to 12 GHz to validate the proposed fractal designs. The FSSs with dissimilar Sierpinski fractal patch elements are printed on RT/Duroid 6202 high frequency laminate. The experimental characterization of the FSS prototypes is accomplished through two different measurement setups composed of commercial horns and elliptical monopole microstrip antennas. The obtained results confirm the compactness and multiband performance of the proposed FSS geometries, caused by the integration of dissimilar fractal element. In addition, the proposed FSSs exhibited frequency tuning ability on the multiband frequency responses. Agreement between simulated and measured results is reported.
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Teng, Fei, Ching-Heng Shiau, Cheng Sun, Robert C. O’Brien i Michael D. McMurtrey. "Investigation of Deformation Behavior of Additively Manufactured AISI 316L Stainless Steel with In Situ Micro-Compression Testing". Materials 16, nr 17 (31.08.2023): 5980. http://dx.doi.org/10.3390/ma16175980.
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Additive manufacturing techniques are being used more and more to perform the precise fabrication of engineering components with complex geometries. The heterogeneity of additively manufactured microstructures deteriorates the mechanical integrity of products. In this paper, we printed AISI 316L stainless steel using the additive manufacturing technique of laser metal deposition. Both single-phase and dual-phase substructures were formed in the grain interiors. Electron backscatter diffraction and energy-dispersive X-ray spectroscopy indicate that Si, Mo, S, Cr were enriched, while Fe was depleted along the substructure boundaries. In situ micro-compression testing was performed at room temperature along the [001] orientation. The dual-phase substructures exhibited lower yield strength and higher Young’s modulus compared with single-phase substructures. Our research provides a fundamental understanding of the relationship between the microstructure and mechanical properties of additively manufactured metallic materials. The results suggest that the uneven heat treatment in the printing process could have negative impacts on the mechanical properties due to elemental segregation.
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Shams, M., Z. Mansurov, C. Daulbayev i B. Bakbolat. "Effect of Lattice Structure and Composite Precursor on Mechanical Properties of 3D-Printed Bone Scaffolds". Eurasian Chemico-Technological Journal 23, nr 4 (31.12.2021): 257. http://dx.doi.org/10.18321/ectj1129.
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This article presents an investigation on designing and fabricating scaffolds with different structures, desired porosity, composition, and surface area to volume ratio (SA:V) for orthopedic applications by using the computer-aided design (CAD) and the stereolithography (SLA) 3D printing technique. Different triply periodic minimal surfaces (TPMS) and functionally graded lattice structures (FGLS) were designed based on various cell geometries. Finite element analysis (FEA), tensile and compression tests were carried out, and the results are presented. Two different resin compositions were used to print the models and compare the effect of resin precursors on the mechanical properties of scaffolds. The first was a biodegradable resin made from soybean oil commercially available on the market (made by Anycubic Co.). The second was a mixture of biodegradable UV-cured resin with 5% W/W of hydroxyapatite (HA) and 5% W/W calcium pyrophosphate (CPP). Bio-Hydroxyapatite and Bio-Calcium Pyrophosphate were obtained from eggshells waste and characterized using XRD and FESEM. The obtained data show that adding resin precursors (HA/CPP) slightly decreases the mechanical strength of printed scaffolds; however, considering their extraordinary effect on bone regeneration, this small effect can be ignored, and HA/CPP can be used as an ideal agent in bioscaffolds.
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Florencio, Rafael, Álvaro Somolinos, Iván González i Felipe Cátedra. "BICGSTAB-FFT Method of Moments with NURBS for Analysis of Planar Generic Layouts Embedded in Large Multilayer Structures". Electronics 9, nr 9 (9.09.2020): 1476. http://dx.doi.org/10.3390/electronics9091476.
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BICGSTAB-FFT method of moment (MM) scheme is proposed to analyze several levels of planar generic layouts embedded in large multilayer structures when the layout geometries are modeled by NURBS surfaces. In this scheme, efficient computation of normalized error defined in iterative bi-conjugate gradient stabilized (BICGSTAB) method for large multilayer structure analysis problems is implemented. The efficient computation is based on pulse expansion with dense equi-spaced mesh of generalized rooftop basis functions (BFs) defined on NURBS surfaces and equivalent periodic problem (EPP) in order to apply fast Fourier transforms (FFT). Moreover, efficient computation of Green’s functions for multilayer structure is implemented for near and far field regions. Experimental and numerical validations of whole printed reflect array antennas of electrical size between 8 and 16 times the vacuum wavelengths are shown. In these validations, CPU time consumptions of the proposed method are obtained with results between few minutes and half an hour using a conventional laptop.
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Peng, Pei-Wen, Jen-Chang Yang, Wei-Fang Lee, Chih-Yuan Fang, Chun-Ming Chang, I.-Jan Chen, Chengpo Hsu i Tzu-Sen Yang. "Effects of Heat Treatment of Selective Laser Melting Printed Ti-6Al-4V Specimens on Surface Texture Parameters and Cell Attachment". Applied Sciences 11, nr 5 (3.03.2021): 2234. http://dx.doi.org/10.3390/app11052234.
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Selective laser melting (SLM) is extensively used for fabricating metallic biomedical products. After 3D printing, it is almost always advisable to apply a heat treatment to release the internal tensions or optimize the mechanical properties of the printed parts. The aim of this paper is to investigate the effects of heat treatment of SLM printed Ti-6Al-4V (Ti64) circular specimens on the areal surface texture parameters and cell attachment. Areal surface texture parameters, including the arithmetic mean height (Sa), root-mean-square height (Sq), skewness (Ssk), and kurtosis (Sku) were characterized. In addition, wavelet-based multi-resolution analysis was applied to investigate the characteristic length scales of untreated and heat-treated Ti64 specimens. In this study, the vertical distance between the highest and lowest position of cell attachment for each sampling area was defined as ΔH. Results showed that an increase in the periodic characteristic length scale was primarily due to the formation of large-scale aggregations of Ti64 metal powder particles on the heat-treated surface. In addition, MG-63 cells preferred lying in concave hollows; in heat-treated specimens, values of ΔH statistically significantly decreased from 31.6 ± 4.2 to 8.8 ± 2.8 μm, while Sku decreased from 3.3 ± 1.4 to 2.6 ± 0.6, indicating a strong influence of Sku on cell attachment.
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Xu, Peng, Wei Xiang Jiang, Xiao Cai, Yue Gou i Tie Jun Cui. "A high-efficiency and ultrathin transmission-type circular polarization converter based on surface structure". EPJ Applied Metamaterials 8 (2021): 4. http://dx.doi.org/10.1051/epjam/2021002.
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In this paper, we propose, design and fabricate a kind of ultrathin and high-efficiency circularly polarization converter based on artificially engineered surfaces in the transmission mode. The converter is composed of double-layer periodic surface structures with cross slots. The top and bottom layers are printed on both sides of the F4B substrate and connected by metallic via holes. The proposed converter can transform the right-handed circularly polarized incident electromagnetic (EM) wave to a left-handed circularly-polarized one with near-unity efficiency in the transmission mode, or vice versa. We explain the conversion mechanism based on numerical simulations and equivalent circuit (EC) theory. The measured result has a good agreement with the simulated one in the working frequency band. Such ultrathin polarization converters can be used in wireless microwave communication, remote sensing, and EM imaging where circularly polarization diversity is needed.
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Mandache, Catalin, Richard Desnoyers i Yan Bombardier. "Crack Growth Monitoring with Structure-Bonded Thin and Flexible Coils". Sensors 22, nr 24 (17.12.2022): 9958. http://dx.doi.org/10.3390/s22249958.
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Structural health monitoring with thin and flexible eddy-current coils is proposed for in situ detection and monitoring of fatigue cracks in metallic aircraft structures, providing a promising means of crack sizing. This approach is seen as an efficient replacement to periodic inspections, as it brings economic and safety benefits. As such, printed-circuit-board eddy-current coils are viable for in situ crack monitoring for multi-layer, electrically conductive structures. They are minimally invasive and could be attached to or embedded into the evaluated structure. This work focuses on the monitoring of fatigue crack growth from a fastener hole with structure-bonded, thin, and flexible spiral coils. Numerical simulations were used for optimization of the driving frequency and selection of crack-sensitive coil parameters. The article also demonstrates the fatigue crack detection capabilities using spiral coils attached to a 7075-T6 aluminum coupon.
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Cuesta, I. I., A. Díaz, M. A. Rojo, L. B. Peral, J. Martínez i J. M. Alegre. "Parameter Optimisation in Selective Laser Melting on C300 Steel". Applied Sciences 12, nr 19 (28.09.2022): 9786. http://dx.doi.org/10.3390/app12199786.
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Additive manufacturing (AM) of metallic materials is increasingly being adopted in numerous sectors, such as biomedicine, aerospace or automotive industries, due to its versatility in the creation of complex geometries and the minimisation of material waste when compared to traditional subtractive methods. In order to ensure a reliable operation of these parts, however, an in-depth study of the effect of additive manufacturing on mechanical properties, including tensile, fatigue and fracture resistance, is necessary. Among the vast number of methods and materials, this project is focused in one of the most promising techniques for the industry: Selective Laser Melting (SLM) for the production of a tools steel, in particular C300 steel components for the automotive sector. The main objective of this paper is to optimise some of the key parameters in the printing process, such as laser power, laser speed and hatch spacing. These variables are essential to obtain parts with good resistance. To that purpose, tensile tests were performed in 3D printed specimens, and then elastoplastic properties were extracted, organised and analysed through a design of experiments for the subsequent output fitting using the response surface methodology.
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Paredes, Ferran, Cristian Herrojo, Ana Moya, Miguel Berenguel Alonso, David Gonzalez, Pep Bruguera, Claudia Delgado Simao i Ferran Martín. "Electromagnetic Encoders Screen-Printed on Rubber Belts for Absolute Measurement of Position and Velocity". Sensors 22, nr 5 (5.03.2022): 2044. http://dx.doi.org/10.3390/s22052044.
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This paper presents, for the first time, an absolute linear electromagnetic encoder consisting of a rubber belt with two chains of screen-printed metallic inclusions (rectangular patches). The position, velocity, and direction of the belt (the moving part) is determined by detecting the inclusions when they cross the stator (the static part). The stator is a microstrip line loaded with three complementary split ring resonators (CSRRs), resonant elements exhibiting a resonance frequency perturbed by the presence of inclusions on top of them (contactless). The line is fed by three harmonic signals tuned to the resonance frequencies of the CSRRs. Such signals are generated by a voltage-controlled oscillator (VCO) managed by a microcontroller. The sensed data are retrieved from the pulses contained in the envelope functions of the respective amplitude modulated (AM) signals (caused by the belt motion) generated at the output port of the line. One of the signals provides the absolute belt position, determined by one of the chains, the encoded one. The information relative to the velocity and motion direction is contained in the other AM signals generated by the motion of the other chain, periodic, and thereby, uncoded. The spatial resolution of the system, a figure of merit, is 4 mm. Special emphasis is devoted to the printing process of the belt inclusions.
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Zafar, Mudasar, Hamzah Sakidin, Mikhail Sheremet, Iskandar B. Dzulkarnain, Abida Hussain, Roslinda Nazar, Javed Akbar Khan i in. "Recent Development and Future Prospective of Tiwari and Das Mathematical Model in Nanofluid Flow for Different Geometries: A Review". Processes 11, nr 3 (10.03.2023): 834. http://dx.doi.org/10.3390/pr11030834.
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The rapid changes in nanotechnology over the last ten years have given scientists and engineers a lot of new things to study. The nanofluid constitutes one of the most significant advantages that has come out of all these improvements. Nanofluids, colloid suspensions of metallic and nonmetallic nanoparticles in common base fluids, are known for their astonishing ability to transfer heat. Previous research has focused on developing mathematical models and using varied geometries in nanofluids to boost heat transfer rates. However, an accurate mathematical model is another important factor that must be considered because it dramatically affects how heat flows. As a result, before using nanofluids for real-world heat transfer applications, a mathematical model should be used. This article provides a brief overview of the Tiwari and Das nanofluid models. Moreover, the effects of different geometries, nanoparticles, and their physical properties, such as viscosity, thermal conductivity, and heat capacity, as well as the role of cavities in entropy generation, are studied. The review also discusses the correlations used to predict nanofluids’ thermophysical properties. The main goal of this review was to look at the different shapes used in convective heat transfer in more detail. It is observed that aluminium and copper nanoparticles provide better heat transfer rates in the cavity using the Tiwari and the Das nanofluid model. When compared to the base fluid, the Al2O3/water nanofluid’s performance is improved by 6.09%. The inclination angle of the cavity as well as the periodic thermal boundary conditions can be used to effectively manage the parameters for heat and fluid flow inside the cavity.
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Evsevleev, Sergei, Tatiana Mishurova, Dmitriy Khrapov, Aleksandra Paveleva, Dietmar Meinel, Roman Surmenev, Maria Surmeneva, Andrey Koptyug i Giovanni Bruno. "X-ray Computed Tomography Procedures to Quantitatively Characterize the Morphological Features of Triply Periodic Minimal Surface Structures". Materials 14, nr 11 (1.06.2021): 3002. http://dx.doi.org/10.3390/ma14113002.
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Additively manufactured (AM) metallic sheet-based Triply Periodic Minimal Surface Structures (TPMSS) meet several requirements in both bio-medical and engineering fields: Tunable mechanical properties, low sensitivity to manufacturing defects, mechanical stability, and high energy absorption. However, they also present some challenges related to quality control, which can prevent their successful application. In fact, the optimization of the AM process is impossible without considering structural characteristics as manufacturing accuracy, internal defects, as well as surface topography and roughness. In this study, the quantitative non-destructive analysis of TPMSS manufactured from Ti-6Al-4V alloy by electron beam melting was performed by means of X-ray computed tomography (XCT). Several advanced image analysis workflows are presented to evaluate the effect of build orientation on wall thicknesses distribution, wall degradation, and surface roughness reduction due to the chemical etching of TPMSS. It is shown that the manufacturing accuracy differs for the structural elements printed parallel and orthogonal to the manufactured layers. Different strategies for chemical etching show different powder removal capabilities and both lead to the loss of material and hence the gradient of the wall thickness. This affects the mechanical performance under compression by reduction of the yield stress. The positive effect of the chemical etching is the reduction of the surface roughness, which can potentially improve the fatigue properties of the components. Finally, XCT was used to correlate the amount of retained powder with the pore size of the functionally graded TPMSS, which can further improve the manufacturing process.
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Wu, Wenjing, Bo Yuan i Aiting Wu. "A Quad-Element UWB-MIMO Antenna with Band-Notch and Reduced Mutual Coupling Based on EBG Structures". International Journal of Antennas and Propagation 2018 (2018): 1–10. http://dx.doi.org/10.1155/2018/8490740.
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A compact planar quad-element ultrawideband (UWB) antenna with a band-notch and low coupling for multiple-input multiple-output (MIMO) system is proposed in this paper. The antenna consists of four circular monopoles with modified defected ground plane and a periodic electromagnetic band gap (EBG) structures. The proposed EBG structures are modified from the traditional mushroom-like ones, comprised of patterns of grids on the top patch, the metallic ground plane, and several vias that connect the top and bottom plane. It is printed at the center of the dielectric substrate to lower electromagnetic coupling between the parallel elements. Besides, by etching four crescent ring-shaped resonant slots on the radiators, a sharp band-notched characteristic is achieved. From the experimental results, the −10 dB bandwidth of the antenna is extended covers from 3.0 to 16.2 GHz, with a sharp notched band at 4.6 GHz. And the isolation is greater than 17.5 dB between its elements, with a peak gain of 8.4 dB and a peak efficiency of 91.2%. Moreover, it has a compact size of 0.6λ×0.6λ×0.016λ at 3 GHz and could be a good candidate for portable devices.
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Sancho, R., F. Galvez, C. L. Garrido, S. Perosanz-Amarillo i D. Barba. "On the mechanical behaviour of additively manufactured metamaterials under dynamic conditions". EPJ Web of Conferences 250 (2021): 05006. http://dx.doi.org/10.1051/epjconf/202125005006.
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High-energy absorption and light-weightiness are two critical properties for impact protection in the aerospace sector. In the past, the use of periodic honeycomb structures or random porous metallic foams were the preferred route to obtain a good specific-energy absorption performance. In recent years, the use of additive manufacturing has increased the design freedom creating a new generation of reticulated and porous materials: the metamaterials or lattice materials. The internal geometries of these lattice structures can be tuned for superior optimal properties, e.g., energyabsorption and density. However, the mechanics of these materials under impact need to be understood with the purpose of mechanical optimisation, and the computational models validated. In this work, we present the experimental compressive behaviour, at room temperature, of two Ti6Al4V lattice structures under static and dynamic conditions. The quasi-static tests were performed by using a universal testing machine while the dynamic tests were conducted at 480s-1 with a split-Hopkinson bar. In all cases, the deformation process was filmed to analyse the failure. Finally, finiteelement simulations were done, employing the Johnson-Cook model, to describe the response of the alloy. The simulations were able to reflect the failure characteristics of each metamaterial but were not able to describe the macroscopic response due to the differences between the experimental and computational volume fraction.
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Koplin, Christof, Eric Schwarzer-Fischer, Eveline Zschippang, Yannick Marian Löw, Martin Czekalla, Arthur Seibel, Anna Rörich i in. "Design of Reliable Remobilisation Finger Implants with Geometry Elements of a Triple Periodic Minimal Surface Structure via Additive Manufacturing of Silicon Nitride". J 6, nr 1 (18.03.2023): 180–97. http://dx.doi.org/10.3390/j6010014.
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When finger joints become immobile due to an accident during sports or a widespread disease such as rheumatoid arthritis, customised finger joint implants are to be created. In an automated process chain, implants will be produced from ceramic or metallic materials. Artificial intelligence-supported software is used to calculate three-dimensional models of the finger bones from two-dimensional X-ray images. Then, the individual implant design is derived from the finger model and 3D printed. The 3D printing process and the structures used are evaluated via model tests and the final implant design via a reliability calculation in a way to ensure that this is also possible via an AI process in the future. Using additive manufacturing with silicon nitride-based ceramics, model specimens and implants are produced via the lithography-based ceramic vat photopolymerisation process with full geometry or elements of triple periodic minimal surfaces structure. The model specimens are tested experimentally, and the loads are matched with a characteristic strength assuming a Weibull distribution of defects in the volume to generate and match failure probabilities. Calculated fracture forces of the silicon nitride-based ceramic structure was validated by comparison of simulation and tests, and the calculation can be used as a quality index for training of artificial intelligence in the future. The proposed method for individualized finger implant design and manufacturing may allow for correction of potential malpositions of the fingers in the future.
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Ding, Liping, Shujie Tan, Wenliang Chen, Yaming Jin i Yicha Zhang. "Manufacturability analysis of extremely fine porous structures for selective laser melting process of Ti6Al4V alloy". Rapid Prototyping Journal 27, nr 8 (25.08.2021): 1523–37. http://dx.doi.org/10.1108/rpj-11-2020-0280.
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Purpose The manufacturability of extremely fine porous structures in the SLM process has rarely been investigated, leading to unpredicted manufacturing results and preventing steady medical or industrial application. The research objective is to find out the process limitation and key processing parameters for printing fine porous structures so as to give reference for design and manufacturing planning. Design/methodology/approach In metallic AM processes, the difficulty of geometric modeling and manufacturing of structures with pore sizes less than 350 μm exists. The manufacturability of porous structures in selective laser melting (SLM) has rarely been investigated, leading to unpredicted manufacturing results and preventing steady medical or industrial application. To solve this problem, a comprehensive experimental study was conducted to benchmark the manufacturability of the SLM process for extremely fine porous structures (less than 350 um and near a limitation of 100 um) and propose a manufacturing result evaluation method. Numerous porous structure samples were printed to help collect critical datasets for manufacturability analysis. Findings The results show that the SLM process can achieve an extreme fine feature with a diameter of 90 μm in stable process control, and the process parameters with their control strategies as well as the printing process planning have an important impact on the printing results. A statistical analysis reveals the implicit complex relations between the porous structure geometries and the SLM process parameter settings. Originality/value It is the first time to investigate the manufacturability of extremely fine porous structures of SLM. The method for manufacturability analysis and printing parameter control of fine porous structure are discussed.
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Hsu, Yu-Chuan, Zhenze Yang i Markus J. Buehler. "Generative design, manufacturing, and molecular modeling of 3D architected materials based on natural language input". APL Materials 10, nr 4 (1.04.2022): 041107. http://dx.doi.org/10.1063/5.0082338.
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We describe a method to generate 3D architected materials based on mathematically parameterized human readable word input, offering a direct materialization of language. Our method uses a combination of a vector quantized generative adversarial network and contrastive language-image pre-training neural networks to generate images, which are translated into 3D architectures that are then 3D printed using fused deposition modeling into materials with varying rigidity. The novel materials are further analyzed in a metallic realization as an aluminum-based nano-architecture, using molecular dynamics modeling and thereby providing mechanistic insights into the physical behavior of the material under extreme compressive loading. This work offers a novel way to design, understand, and manufacture 3D architected materials designed from mathematically parameterized language input. Our work features, at its core, a generally applicable algorithm that transforms any 2D image data into hierarchical fully tileable, periodic architected materials. This method can have broader applications beyond language-based materials design and can render other avenues for the analysis and manufacturing of architected materials, including microstructure gradients through parametric modeling. As an emerging field, language-based design approaches can have a profound impact on end-to-end design environments and drive a new understanding of physical phenomena that intersect directly with human language and creativity. It may also be used to exploit information mined from diverse and complex databases and data sources.
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Modir, Alireza, Arnaud Casterman i Ibrahim Tansel. "Detection of Anomalies in Additively Manufactured Metal Parts Using CNN and LSTM Networks". Recent Progress in Materials 05, nr 03 (26.07.2023): 1–20. http://dx.doi.org/10.21926/rpm.2303028.
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The process of metal additive manufacturing (AM) involves creating strong, complex components by using fine metal powders. Extensive use of AM methods is expected in near future for the production of small and medium-sized batches of end-use products and tools. The ability to detect loads and defects would enable AM components to be used in critical applications and improve their value. In this study, the Surface Response to Excitation (SuRE) method was used to investigate wave propagation characteristics and load detection on AM metallic specimens. With completely solid infills and the same geometry, three stainless steel test bars are produced: one conventionally and two additively. To investigate the effect of infills, four bars with the same geometries are 3D printed with triangular and gyroid infills with either 0.5 mm or 1 mm skin thickness. Two piezoelectric disks are attached to each end of the test specimens to excite the parts with guided waves from one end and monitor the dynamic response to excitation at the other end. The response to excitation was recorded when bars were in a relaxed condition and when compressive loads were applied at five levels in the middle of them. For converting time-domain signals into 2D time-frequency images, the Short-Time Fourier Transform (STFT) and Continuous Wavelet Transform (CWT) were implemented. To distinguish the data based on fabrication characteristics and level of loading, two deep learning models (Long Short-term Memory algorithm (LSTM) and Convolutional Neural Networks (2D CNN)) were utilized. Time-frequency images were used to train 2D CNN, while raw signal data was used to train LSTM. It was found that both LSTM and 2D CNN could estimate solid parts' loading level with an accuracy of more than 90%. In parts with infills, CNN outperformed LSTM for the classification of over five classes (internal geometry and loading level simultaneously).
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Ferro, Paolo, Alberto Fabrizi, Hamada Elsayed i Gianpaolo Savio. "Multi-Material Additive Manufacturing: Creating IN718-AISI 316L Bimetallic Parts by 3D Printing, Debinding, and Sintering". Sustainability 15, nr 15 (2.08.2023): 11911. http://dx.doi.org/10.3390/su151511911.
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Allowing for complex shape and low energy consumption, 3D printing, debinding, and sintering (PDS) is a promising and cost-effective additive manufacturing (AM) technology. Moreover, PDS is particularly suitable for producing bimetallic parts using two metal/polymer composite filaments in the same nozzle, known as co-extrusion, or in different nozzles, in a setup called bi-extrusion. The paper describes a first attempt to produce bimetallic parts using Inconel 718 and AISI 316L stainless steel via PDS. The primary goal is to assess the metallurgical characteristics, part shrinkage, relative density, and the interdiffusion phenomenon occurring at the interface of the two alloys. A first set of experiments was conducted to investigate the effect of deposition patterns on the above-mentioned features while keeping the same binding and sintering heat treatment. Different sintering temperatures (1260 °C, 1300 °C, and 1350 °C) and holding times (4 h and 8 h) were then investigated to improve the density of the printed parts. Co-extruded parts showed a better dimensional stability against the variations induced by the binding and sintering heat treatment, compared to bi-extruded samples. In co-extruded parts, shrinkage depends on scanning strategy; moreover, the higher the temperature and holding time of the sintering heat treatment, the higher the density reached. The work expands the knowledge of PDS for metallic multi-materials, opening new possibilities for designing and utilizing functionally graded materials in optimized components. With the ability to create intricate geometries and lightweight structures, PDS enables energy savings across industries, such as the aerospace and automotive industries, by reducing component weight and enhancing fuel efficiency. Furthermore, PDS offers substantial advantages in terms of resource efficiency, waste reduction, and energy consumption compared to other metal AM technologies, thereby reducing environmental impact.
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Al Ajmi, Haitham, Mohammed Bait-Suwailam, Mahmoud Masoud i Muhammad Shafiq. "EFFICIENCY ENHANCEMENT OF PHOTOVOLTAIC SOLAR CELLS USING METAMATERIALS ABSORBING SCREEN". Journal of Engineering Research [TJER] 19, nr 2 (5.04.2023): 85–94. http://dx.doi.org/10.53540/tjer.vol19iss2pp85-94.
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This paper proposes a novel technique for the efficiency enhancement of photovoltaic (PV) solar cells using metamaterials absorbing screens. This kind of engineered material comprises resonant metallic rings that are printed on a host low-loss dielectric substance and made periodic in a two-dimensional lattice. The absorbing screen has been carefully designed, and its retrieved effective constitutive parameters, effective electric permittivity ϵeff and effective magnetic permeability µeff, are integrated within a numerically modelled amorphous-Silicon-based PV solar cell structure as an impedance matching layer. Such arrangement will greatly achieve matching between the effective impedance of the composite solar cell structure and free-space impedance and will result in higher photons absorption through the metamaterials anti-reflective screen. Numerical full-wave electromagnetic simulations are carried out using CST Microwave Studio for the design of a metamaterial absorbing screen. Due to the large computational resources required, COMSOL Multiphysics was adopted in the design and analysis of the composite structure comprising a two-dimensional PV solar cells layer. Based on the numerical results, both optical and electric characteristics of the PV solar cell structure were enhanced with the use of a metamaterial layer. Moreover, efficiency enhancement by 5% was permissible, in which efficiency reached 12% with the use of metamaterials as compared to the efficiency of the classical PV cells of 7%. The obtained results are very promising, and the potential integration of metamaterials in commercial PV solar cells will show significant advancement in efficiency enhancement of PV cells and realization of smart PV solar cells with the consideration of additional features from metamaterials.
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Ellebracht, Nathan C., Pratanu Roy, Thomas Moore, Aldair E. Gongora, Diego I. Oyarzun, Joshuah K. Stolaroff i Du T. Nguyen. "3D printed triply periodic minimal surfaces as advanced structured packings for solvent-based CO2 capture". Energy & Environmental Science, 2023. http://dx.doi.org/10.1039/d2ee03658d.
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Advanced structured packing geometries fabricated with 3D printing were used for absorber CO2 capture with a liquid solvent. Compared to conventional packing, they had greatly enhanced (90–140%) effective surface areas and comparable hydrodynamics.
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Xiong, Yichen, i Bing Zhang. "A metallic 3D printed miniaturized circularly polarized log periodic Koch‐dipole array antenna". International Journal of RF and Microwave Computer-Aided Engineering 31, nr 7 (9.04.2021). http://dx.doi.org/10.1002/mmce.22684.
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Małachowska, A., Ł. Żrodowski, B. Morończyk, Ł. Maj, A. Kuś i T. Lampke. "Selective Laser Melting of Fe-Based Metallic Glasses With Different Degree of Plasticity". Metallurgical and Materials Transactions A, 8.12.2022. http://dx.doi.org/10.1007/s11661-022-06913-w.
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AbstractSelective laser melting (SLM) is one of the promising techniques for producing metallic glass components with unlimited geometries and dimensions. In the case of iron-based metallic glasses, the appearance of cracks remains a problem. In this work, two alloys Fe48Mo14Cr15Y2C15B6 and (Fe0.9Co0.1)76Mo4(P0.45C0.2B0.2Si0.15)20, differing in their plasticity, were printed with a double stage scanning strategy. Both alloys were characterized by a fully amorphous structure and a crack grid that coincided with the hatch distance in the first scan. Segregations of metalloids were observed in the vicinity of the cracks. Fe48Mo14Cr15Y2C15B6 samples were characterized by a high compression strength of 1298 ± 11 MPa and zero plasticity. The compression strength of the (Fe0.9Co0.1)76Mo4(P0.45C0.2B0.2Si0.15)20 samples was 142 ± 22 MPa. The results obtained suggest that further development of scanning strategies and research on the influence of alloying elements is needed.
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Romero, Pablo E., Juan M. Barrios, Esther Molero i Andres Bustillo. "Tuning 3D-printing parameters to produce vertical ultra-hydrophobic PETG parts with low ice adhesion: A food industry case study". Proceedings of the Institution of Mechanical Engineers, Part B: Journal of Engineering Manufacture, 6.06.2023, 095440542311789. http://dx.doi.org/10.1177/09544054231178970.
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The food industry is a dynamic component of the European economy. A wide variety of products and small batch are demanded in a market that is accustomed to frequenting changes in food packaging formats. Cheaper and lighter 3D-printed tools are replacing expensive metallic ones, producing previously impossible product geometries and processing fish and meat products more quickly and in more reliable ways. In addition to food contact, these printed parts are often required to have hydrophobic surfaces that facilitate cleaning and have low adhesion both foodstuffs and ice. In this study, the surface wettability of PolyEthylene Terephthalate Glycol (PETG) printed parts via fused filament fabrication is assessed. Specifically, several printing parameters (layer height, extrusion temperature, printing speed, acceleration, and flow) and their influence on the hydrophobicity of 3D printed parts with vertical orientation are analyzed. The experimental results indicated that the parameter with the strongest influence on the wettability of the XZ parts was flow: low-flow values generated ultra-hydrophobic surfaces, with contact angles higher than 120°. Acceleration had no influence at low flow values; however, for high flow values, low acceleration rates yielded higher contact angles. In addition, it was experimentally proven that the 3D-printed PETG parts with high-contact angle surfaces showed lower adhesion to ice than those with low contact-angle surfaces. The technology was applied to a case study of a 3D-printed hopper for the ice duct of an ice-cube machine.
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Li, Tiantian, i Yaning Li. "Prediction of the Anisotropy of Chiral Mechanical Metamaterials via Micropolar Modeling". Journal of Applied Mechanics, 24.08.2022, 1–21. http://dx.doi.org/10.1115/1.4055349.
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Abstract The anisotropic elastic mechanical properties of a family of single material chiral mechanical metamaterials are explored systematically. An integrated monoclinic-micropolar constitutive model is developed to quantify the anisotropic mechanical properties of the chiral designs with different geometries. The model predictions are thoroughly verified by mechanical experiments on 3D printed specimens and FE simulations with periodic boundary conditions. The new integrated monoclinic-micropolar model can predict the anisotropic elastic properties in all directions. Normalized model parameters for this family of chiral designs are provided. Finally, the anisotropic effective stiffness and effective Poisson's ratio of all geometric designs in this family are quantified. The anisotropy and the completeness of auxeticity are evaluated systematically.
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Wang, C., S. Chandra, X. P. Tan i S. B. Tor. "3D printing of metallic micro-gears for micro-fluidic applications". Journal of Micromechanics and Molecular Physics 06, nr 02 (czerwiec 2021). http://dx.doi.org/10.1142/s2424913021410022.
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Micro-fluidic devices are essential to handle fluids on the micro-meter scale (micro-scale), making them crucial to biomedical applications, where micro-gear is the key component for active fluid mixing. Rapid and direct fabrication of micro-gears is preferred because they are usually custom-made to specific applications and iterative design is needed. However, conventional manufacturing (CM) techniques for micro-fluidic devices are labor-intensive and time-consuming as multiple steps are required. Three-dimensional (3D) printing, or formally known as additive manufacturing (AM) offers a promising alternative over CM techniques in producing near-net shape complex geometries, given the micro-scale fabrication process. In this work, two types of powder-bed fusion (PBF) AM techniques, namely laser-PBF (L-PBF) and electron beam-PBF (EB-PBF) are used to benchmark 3D-printed micro-gears from stainless steel 316L micro-granular powders. Results showcase the preeminence of L-PBF over EB-PBF in generating distinguishable micro-scale features on gear profiles and superior micro-hardness in mechanical property. Overall, PBF metal AM shows significant promise in advancing the otherwise tedious state of CM for micro-gears.
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Tang, Shiwei, Qiong He, Shiyi Xiao, Xueqin Huang i Lei Zhou. "Fractal plasmonic metamaterials: physics and applications". Nanotechnology Reviews 4, nr 3 (1.01.2015). http://dx.doi.org/10.1515/ntrev-2014-0025.
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AbstractWe review our recent works on a particular type of metamaterials (MTMs), which are metallic plates drilled with periodic arrays of subwavelength apertures typically in fractal-like complex shapes. We first show that such MTMs can well mimic plasmonic metals in terms of surface plasmon properties, but with plasmon resonances solely dictated by their aperture geometries rather than the constitutional materials. We then develop an effective-medium description for such plasmonic MTMs based on the mode expansion theory. Based on these theoretical understandings, we show that such MTMs exhibit several interesting applications, such as superlensing, hyperlensing, and enhancing light-matter interactions, which are demonstrated by microwave experiments or full-wave simulations.
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Noroozi, Reza, Farzad Tatar, Ali Zolfagharian, Roberto Brighenti, Mohammad Amin Shamekhi, Abbas Rastgoo, Amin Hadi i Mahdi Bodaghi. "Additively Manufactured Multi-Morphology Bone-like Porous Scaffolds: Experiments and Micro-Computed Tomography-Based Finite Element Modeling Approaches". International Journal of Bioprinting 8, nr 3 (7.05.2022). http://dx.doi.org/10.18063/ijb.v8i3.556.
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Tissue engineering, whose aim is to repair or replace damaged tissues by combining the principle of biomaterials and cell transplantation, is one of the most important and interdisciplinary fields of regenerative medicine. Despite remarkable progress, there are still some limitations in the tissue engineering field, among which designing and manufacturing suitable scaffolds. With the advent of additive manufacturing (AM), a breakthrough happened in the production of complex geometries. In this vein, AM has enhanced the field of bioprinting in generating biomimicking organs or artificial tissues possessing the required porous graded structure. In this study, triply periodic minimal surface structures, suitable to manufacture scaffolds mimicking bone’s heterogeneous nature, have been studied experimentally and numerically; the influence of the printing direction and printing material has been investigated. Various multi-morphology scaffolds, including gyroid, diamond, and I-graph and wrapped package graph (I-WP), with different transitional zone, have been three-dimensional (3D) printed and tested under compression. Further, a micro-computed tomography (μCT) analysis has been employed to obtain the real geometry of printed scaffolds. Finite element analyses have been also performed and compared with experimental results. Finally, the scaffolds’ behavior under complex loading has been investigated based on the combination of μCT and finite element modeling.
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Sankineni, Rakesh, i Y. Ravi Kumar. "Evaluation of energy absorption capabilities and mechanical properties in FDM printed PLA TPMS structures". Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science, 18.08.2021, 095440622110395. http://dx.doi.org/10.1177/09544062211039530.
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Additive manufacturing is an advanced technology used to fabricate complex geometries with unique properties like cellular structures which accommodate repeated unit cells located in the x, y and z direction. These structures can be used as infill patterns due to their self-supporting structure. Among the cellular structures, Triply Periodic Minimal Surface (TPMS) structures such as Gyroid, Diamond and Schwarz Primitive (SchwarzP) structures can be tailored to produce complex structures for various applications like tissue engineering scaffolds and replace the conventional polymeric foams. TPMS structures are designed and manufactured by using the Fused Deposition Modelling (FDM) technique using Poly-Lactic Acid (PLA) as material. Among TPMS structures, Gyroid is having a unique property like structurally symmetric which design was modified to enhance the mechanical properties. The modified Gyroid or deformed Gyroid undergone a quasi-static compression test and compare the results with Diamond and SchwarzP structures. Porosity and permeability coefficients are evaluated and an optical microscope is used to verify the fabricated components. As well as, Failure patterns of the structures were evaluated and energy absorption capabilities determined. The main objective of this paper is to evaluate the impact of design and porosity on the mechanical and morphological properties of TPMS structures. In conclusion, the deformed Gyroid has more energy absorption capability up to the 11.6% strain than other TPMS structures. After 11.6% of strain, SchwarzP structure dominates.
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Liu, Bingyan, Shirong Liu, Vasanthan Devaraj, Yuxiang Yin, Yueqi Zhang, Jingui Ai, Yaochen Han i Jicheng Feng. "Metal 3D nanoprinting with coupled fields". Nature Communications 14, nr 1 (15.08.2023). http://dx.doi.org/10.1038/s41467-023-40577-3.
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AbstractMetallized arrays of three-dimensional (3D) nanoarchitectures offer new and exciting prospects in nanophotonics and nanoelectronics. Engineering these repeating nanoarchitectures, which have dimensions smaller than the wavelength of the light source, enables in-depth investigation of unprecedented light–matter interactions. Conventional metal nanomanufacturing relies largely on lithographic methods that are limited regarding the choice of materials and machine write time and are restricted to flat patterns and rigid structures. Herein, we present a 3D nanoprinter devised to fabricate flexible arrays of 3D metallic nanoarchitectures over areas up to 4 × 4 mm2 within 20 min. By suitably adjusting the electric and flow fields, metal lines as narrow as 14 nm were printed. We also demonstrate the key ability to print a wide variety of materials ranging from single metals, alloys to multimaterials. In addition, the optical properties of the as-printed 3D nanoarchitectures can be tailored by varying the material, geometry, feature size, and periodic arrangement. The custom-designed and custom-built 3D nanoprinter not only combines metal 3D printing with nanoscale precision but also decouples the materials from the printing process, thereby yielding opportunities to advance future nanophotonics and semiconductor devices.
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Pederson, Mark R., i Warren E. Pickett. "Theoretical Investigation of Fluorinated and Hydrocenated Diamond <100> Filks". MRS Proceedings 270 (1992). http://dx.doi.org/10.1557/proc-270-389.
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ABSTRACTTo investigate some of the fundamental differences between halogen and hydrogen assisted diamond film growth we have performed several calculations related to the <100> diamond surface. The models used in these investigations include ten-layer periodic slabs of free standing fluorinated diamond films as well as isolated clusters [C21F6H20]. For purposes of comparison, we have also performed calculations on models of the hydrogenated <100> surface. The calculations are performed within the density-functional framework using LCAO and LAPW computational methods. We have considered two geometries of a monofluoride surface. The first surface, best described as an ideal l×l surface with a monolayer of ionically bonded fluorines, exhibits a metallic density of states in contrast to a 2×l reconstructed surface with chemically bonded fluorines that is found to be insulating. We compare theoretical carbon core level shifts with experimental values and discuss growth models based on these surface calculations.