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- 2018
- Lorentzian influence
- optical flow
- additive white Gaussian noise
- 2D vector
- Materials characterization
- laser additive manufacturing
- selective laser sintering
- Additive manufacturing
- selective laser melting
- Optoelectronic Information Science and Engineering
- Mechanical Engineering
- University of Johannesburg
- Assumption University
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Laser Enhanced Direct Print Additive Manufacturing of Embedded Circular Cross-Section Optical Fiber Interconnects for Board Level Computing Devices
摘要： Integrated photonics have many compelling advantages for computing and communication applications, including in high-speed and extremely wide bandwidth operations. Current systems are typically hybrid assemblies of packaged photonic devices where printed circuit boards often serve to route electrical signals and power, and in some cases, have runs of optical fibers. We present a flexible, low cost assembly method of optical interconnects for photonic systems that could enable higher transmission rates, lower power requirements, improved signal integrity and timing, less heat generation, and improved security of communication signals. The new process is based on laser enhanced direct print additive manufacturing (LE-DPAM) that combines fused deposition modeling (FDM) of plastic, micro-dispensing of rubber-like materials, and picosecond laser subtraction. The process is demonstrated by fabricating few-mode and multi-mode optical fibers in a controlled manner such that compact, 3-dimensional optical interconnects can be printed along non-lineal paths. We have produced working optical interconnects with fiber core diameters from 70-μm to as small as 12-μm. Our results demonstrate surface roughness of less than 100 nm, and optical transmitted power of 63% that of a commercial fiber, for proof of concept devices. We anticipate these devices to be a starting point in the development of more sophisticated electro-optical computing devices using this new LE-DPAM technique. The LE-DPAM approach could lead to large scale integrated photonic computing devices that would replace our current generation of servers, computers, and phones.
关键词： 3D printing,Optical fiber interconnects,Additive manufacturing,Laser enhanced direct print additive manufacturing
更新于2025-09-23 15:19:57
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Production Tools Made by Additive Manufacturing Through Laser-based Powder Bed Fusion; Herstellung von Produktionswerkzeugen mittels additiver Fertigung durch laserbasiertes Pulverbettschmelzen;
摘要： This paper deals with the design and production of stamping tools and dies for sheet metal components and injection molds for plastic components. Laser-based Powder Bed Fusion (LPBF) is the additive manufacturing method used in this investigation. Solid and topology optimized stamping tools and dies 3D-printed in DIN 1.2709 (maraging steel) by LPBF are approved/certified for stamping of up to 2-mm thick hot-dip galvanized DP600 (dual-phase steel sheet). The punch in a working station in a progressive die used for stamping of 1-mm thick hot-dip galvanized DP600 is 3D-printed in DIN 1.2709, both with a honeycomb inner structure and after topology optimization, with successful results. 3D printing results in a significant lead time reduction and improved tool material efficiency. The cost of 3D-printed stamping tools and dies is higher than the cost of those made conventionally. The core (inserts) of an injection mold is 3D-printed in DIN 1.2709, conformal cooling optimized and 3D-printed in Uddeholm AM Corrax, and compared with the same core made conventionally. The cooling and cycle time can be improved, if the injection molding core (inserts) is optimized and 3D-printed in Uddeholm AM Corrax. This paper accounts for the results obtained in the above-mentioned investigations.
关键词： Design,Injection molding,Tools,Stamping,Powder bed fusion,Optimization,Topology,Metal,Additive manufacturing,Cooling
更新于2025-09-23 15:19:57
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Multi-physics modelling of molten pool development and track formation in multi-track, multi-layer and multi-material selective laser melting
摘要： Selective laser melting (SLM) is a promising powder-based additive manufacturing technology due to its capability to fabricate metallic components with complex geometries. While most previous investigations focus on printing with a single material, recent industry-orientated studies indicate the need for multi-material SLM in several high-value manufacturing sectors including medical devices, aerospace and automotive industries. However, understanding the underlying physics in multi-material SLM remains challenging due to the di?culties of experimental observation. In this paper, an integrated modelling framework for multi-track, multi-layer and multi-material SLM is developed to advance the in-depth understanding of this process. The main novelty is in modelling the molten pool evolvement and track morphology of multiple materials deposited on the same and across different layers. Discrete element method (DEM) is employed to reproduce the powder deposition process of multiple materials in different deposition patterns, with particle size distribution imported from a particle size analyser. Various phenomena including balling effect, keyhole depression, and lack of fusion between layers are investigated with different laser energy inputs. As a result of the different thermal properties, several process parameters including energy density and hatch spacing are optimised for different powder materials to obtain a continuous track pro?le and improved scanning e?ciency. The interface between two layers of different materials is visualised by simulation; it was found that the phase migration at the interface is related to the convection ?ow inside the molten pool, which contributes to the mixing of the two materials and elemental diffusion. This study signi?cantly contributes to the challenging area of multi-material additive manufacturing by providing a greater in-depth understanding of the SLM process from multi-material powder deposition to laser interaction with powders across multiple scanning tracks and different building layers than can be achieved by experimentation alone.
关键词： Additive manufacturing,Discrete element method (DEM),Computational ?uid dynamics (CFD),Heat transfer,Multi-material,Selective laser melting (SLM)
更新于2025-09-23 15:19:57
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Additivea??Assisted Hota??Casting Free Fabrication of Diona??Jacobson 2D Perovskite Solar Cell with Efficiency Beyond 16%
摘要： Two-dimensional (2D) Dion-Jacobson (DJ) perovskite solar cells (PVSCs) with high power conversion efficiency (PCE) are currently predominately fabricated via a hot-casting process. The reason lies in the difficulty in preparing high-quality perovskite film under mild condition when the application of divalent ammonium removes the weak interaction from the spacer cation layer. In this work, the morphology of the 2D DJ perovskite film with rigid piperidinium ring is tuned through room-temperature spin-coating method, with the aid of methylammonium thiocyanate (MASCN) additive. With optimized amount of MASCN addition, the perovskite films deposited on poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] (PTAA)/poly[(9,9-bis(30-(N,N-dimethylamino)propyl)-2,7-uorene)-alt-2,7-(9,9-dioctylfuorene)] (PFN) substrate exhibit fine crystallinity, preferred orientation, decreased defects and better energy level alignment with the hole transport layer. The device with inverted planar structure presents JSC of 17.91 mA cm-2, VOC of 1.19 V, FF of 0.76, with a maximum PCE of 16.25%, which is the highest PCE for 2D DJ PVSCs free of hot-casting. The unsealed device maintained around 80% of its initial efficiency after 35 days exposure to air (Hr = 45 ± 5%). This work provides a potential route towards high performance 2D DJ PVSCs.
关键词： additive,2D perovskite,film morphology,charge transport,growth orientation
更新于2025-09-23 15:19:57
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Numerical studies of residual states and scaling effects in laser-directed energy deposition additive manufacturing
摘要： Sequentially coupled thermo-mechanical model was used to simulate the residual stresses and residual distortions in the directed energy deposition additive manufacturing by laser. The proposed models were validated by comparison with experimental data. Different sizes of components were used to study the scaling effects. Results indicate that the residual stress can be controlled by the component sizes. This phenomenon can be explained by the bending deformation and the temperature fluctuations, especially the cooling rate, in the directed energy deposition additive manufacturing process. Both the bending deformation and the temperature fluctuations can be controlled by the ambient temperature and the designed process parameters. Analytical model was established to show how the components’ sizes affect the final residual states in combination with different design parameters.
关键词： Scaling effect,Residual stress,Residual distortion,Additive manufacturing
更新于2025-09-23 15:19:57
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Design of a laser control system with continuously variable power and its application in additive manufacturing
摘要： system adjusts the laser position. This paper will also discuss the development and advanced laser control techniques enable a higher level of control over the processing process relies heavily on understanding and controlling the thermodynamics of the polymer melt temperatures and lead to more uniform components. Currently, there are no commercial options for a laser power controller that allows continuously variable power to be used as a galvanometer process. One of the biggest challenges SLS faces is lack of adequate process control, which leads to comparatively high component variations. It has been shown that implementing more manufacturing processes with applications in aerospace, biomedical, tooling, prototyping, and beyond. SLS is capable of creating unique, functional parts with little waste and no tooling by using a high-powered laser to selectively melt powdered polymer into desired shapes. This Selective laser sintering (SLS) is one of the most popular industrial polymer additive implementation of a galvanometer controller solution that works in conjunction with an off-the-shelf unit to enable this crucial functionality and will present results showing that, when applied laser sintering (SLS) additive manufacturing. The work contained in this paper is a continuation of previous work that developed a method of controlling laser power is SLS in order to improve the consistency of components built [1]. This previous effort was capable of improving temperature uniformity of SLS components by up to 57% and strength uniformity by up to 45%. Powder Bed Fusion
关键词： Laser Control,Additive Manufacturing,Surrogate Modeling,Powder Bed Fusion,Process Control
更新于2025-09-23 15:19:57
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Assessment of laser power and scan speed influence on microstructural features and consolidation of AISI H13 tool steel processed by additive manufacturing
摘要： Additive manufacturing can produce parts with complex geometries in fewer steps than conventional processing, which leads to cost reduction and a higher quality of goods. One potential application is the production of molds and dies with conformal cooling for injection molding, die casting, and forging. AISI H13 tool steel is typically used in these applications because of its high hardness at elevated temperatures, high wear resistance, and good toughness. However, available data on the processing of H13 steel by additive manufacturing are still scarce. Thus, this study focused on the processability of H13 tool steel by powder bed fusion and its microstructural characterization. Laser power (97-216 W) and scan speed (300-700 mm/s) were varied, and the consolidation of parts, common defects, solidification structure, microstructure, and hardness were evaluated. Over the range of processing parameters, microstructural features were mostly identical, consisting of a predominantly cellular solidification structure. Cellular/dendritic solidification structure displayed C, Cr, and V segregation toward cell walls. The thermal cycle resulted in alternating layers of heat-affected zones, which varied somewhat in hardness and microstructure. Retained austenite was correlated to the solidification structure and displayed a preferential orientation with {001}//build direction. Density and porosity maps were obtained by helium gas pycnometry and light optical microscopy, respectively, and, along with linear crack density, were used to determine appropriate processing parameters for H13 tool steel. Thermal diffusivity, thermal conductivity, and thermal capacity were measured to determine dimensionless processing parameters, which were then compared to others reported in the literature.
关键词： retained austenite,powder bed fusion,additive manufacturing,conformal cooling,processing parameters
更新于2025-09-23 15:19:57
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Accuracy of complex internal channels produced by laser powder bed fusion process
摘要： Additive manufacturing (AM) technology has great potential in manufacturing complex internal channels for several applications such as satellite-communication microwave systems. These systems can have complex shapes and make traditional ?nishing processes a challenge for additive parts. Therefore, it is desirable that the internal surfaces are as close as possible to the tolerance of the ?eld of application. In this study, a complex component, a unique waveguide device with bending, twisting and ?ltering functionalities, has been designed and manufactured in AlSi10Mg alloy through laser powder bed fusion (L-PBF) process. Three di?erent prototypes with three di?erent curvature (R of 50 mm, 40 mm and 30 mm), operating in Ku/K band, have been manufactured and tested showing a very good agreement with the desired performances. Using 3D scan data, the internal deviations from the CAD model have been evaluated showing an average deviation of the internal areas of about 0.08 mm, 0.046 mm and 0.023 mm from the CAD model for the R of 50 mm, 40 mm and 30 mm respectively The surface roughness measured in the internal channel is about Ra (arithmetic average roughness) of 8 μm ± 1.3 μm and Rz (average maximum height of the roughness pro?le) of 62.3 μm ± 0.34 μm.
关键词： Integration waveguide subsystem,Additive manufacturing,Laser powder bed fusion
更新于2025-09-23 15:19:57
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The influence of heat treatment on the microstructure of products manufactured by direct laser deposition using titanium alloy Ti-6Al-4V
摘要： The titanium alloy Ti-6Al-4V is an important alloy in the aerospace industry. The Direct Laser Deposition (DLD) allows manufacturing products of complex geometric shapes from this alloy, which are not inferior in quality to traditional methods. As a result of previous studies, it was found that the product structure does not match the specified requirements for the Ti-6Al-4V alloy and heat treatment is required. In this research, annealing of samples was carried out in different modes, where the time and annealing temperature varied. The microstructure of the products was studied. As a result of the work, it was found that at an annealing temperature of 600–650 °C, the microstructure is heterogeneous: individual grains of the b-phase are preserved. With an increase of the annealing temperature (750 °C–900 °C), the prior b-grains become less distinguishable. It was found that the length decreases with increasing plate thickness of the metastable a0-phase with increasing temperature. With an increase in the propagation time of grain boundaries, the structure becomes homogeneous. The microhardness of the samples after heat treatment decreases slightly, remains in the range of 300–400 HV0,5.
关键词： Direct laser deposition,Direct metal deposition,Microstructure,Additive manufacturing,Ti-6Al-4V,Heat treatment
更新于2025-09-23 15:19:57
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Rationally designed functionally graded porous Ti6Al4V scaffolds with high strength and toughness built via selective laser melting for load-bearing orthopedic applications
摘要： Functionally graded materials (FGMs) with porosity variation strategy mimicking natural bone are potential high-performance biomaterials for orthopedic implants. The architecture of FGM scaffold is critical to gain the favorable combination of mechanical and biological properties for osseointegration. In this study, four types of FGM scaffolds with different structures were prepared by selective laser melting (SLM) with Ti6Al4V as building material. All the scaffolds were hollow cylinders with different three-dimensional architectures and had gradient porosity resembling the graded-porous structure of human bone. Two unit cells (diamond and honeycomb-like unit cells) were used to construct the cellular structures. Solid support structures were embedded into the cellular structures to improve their mechanical performances. The physical characteristics, mechanical properties, and deformation behaviors of the scaffolds were compared systematically. All the as-built samples with porosities of ~52–67% exhibited a radial decreasing porosity from the inner layer to the outer layer, and their pore sizes ranged from ~420 to ~630 μm. The compression tests showed the Young’s moduli of all the as-fabricated samples (~3.79–~10.99 GPa) were similar to that of cortical bone. The FGM structures built by honeycomb-like unit cells with supporting structure in outer layer exhibited highest yield strength, toughness and stable mechanical properties which is more appropriate to build orthopedic scaffolds for load-bearing application.
关键词： Additive manufacturing,Orthopedic scaffolds,Mechanical properties,Functionally graded materials
更新于2025-09-23 15:19:57