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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
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Plastic strain localization induced by microstructural gradient in laser cladding repaired structures
摘要： Laser Cladding is an additive manufacturing technology well suited for the repair of complex metallic components. The repair is a two-step process: first, one removes the worn region and then, the initial geometry is reconstructed locally. The aim of this work is to study the influence of the microstructural gradient on the strain localization in repaired structures. More precisely, we perform in-situ SEM tensile tests completed by EBSD observations of the microstructure in the interface neighborhood between the base material and the repaired region. Furthermore, we monitor the evolution of the local plastic strain distribution at the grain level until failure. This is performed by Digital Image Correlation methods and superposition of grains contours and strain maps. The observations of grain size and plasticity are compared with predictions provided by a Hall-Petch model. The study emphasizes the importance of the microstructural gradient in the vicinity of reparation interface, more precisely it reveals that this gradient induce multiaxial strains and that the strain localization phenomenon is governed mainly by a grain size effect.
关键词： Laser Cladding repair,Additive manufacturing,SEM in-situ tests,strain localization,microstructural gradient
更新于2025-09-23 15:19:57
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3D particle tracking velocimetry for the determination of temporally resolved particle trajectories within laser powder bed fusion of metals
摘要： Within this work, we present a system for the measurement of the three-dimensional (3D) trajectories of spatters and entrained particles during laser powder bed fusion (L-PBF) of metals. It is comprised of two ultrahigh-speed cameras and a reconstruction task specific processing reconstruction algorithm. The system enables an automated determination of 3D measures from the trajectories of a large number of tracked particles. Ambiguity evolving from an underdetermined geometrical situation induced by a two-camera setup is resolved within the tracking using a priori knowledge of L-PBF of metals. All processing steps were optimized to run on a graphics processing unit to allow the processing of large amounts of data within an appropriate time frame. The overall approach was validated by a comparison of the measurement results to synthetic images with a known 3D ground truth.
关键词： laser,high-speed imaging,3D particle velocimetry,image processing,additive manufacturing,powder bed fusion
更新于2025-09-23 15:19:57
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Crystallographic Orientation Control of 316L Austenitic Stainless Steel via Selective Laser Melting
摘要： In recent years, additive manufacturing has attracted attention as a technology that enables control of the crystallographic texture of metallic materials. We achieved successful control of the crystallographic texture of 316L austenitic stainless steel using selective laser melting (SLM). Three distinguished textures were achieved by changing the laser scan speed, namely: the single crystalline-like texture with {001} orientation in the build direction, the crystallographic lamellar texture in which two kinds of grains with {011} and {001} orientations in the build direction are alternately stacked, and polycrystalline with relatively random orientation. The melt pool shape and the solidification behavior (thermal gradient and migration velocity of solid/liquid interface) in a melt pool could be important controlling factors for the evolution of the crystallographic texture under the SLM process.
关键词： anisotropy,crystallographic texture,metal additive manufacturing (AM),selective laser melting (SLM),melt pool
更新于2025-09-23 15:19:57
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[IEEE 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Chicago, IL, USA (2019.6.16-2019.6.21)] 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Ultralight Luminescent Solar Concentrators for Space Solar Power Systems
摘要： This paper reports the design, fabrication, and characterization of arrays of miniaturized, internally fed, polymer electrospray emitters fabricated with stereolithography. The freeform additive manufacturing process used to make the devices has associated two orders of magnitude reduction in the fabrication cost per device and fabrication time (from thousands of dollars to tens of dollars, and from months to hours, respectively) and a two orders of magnitude reduction in the cost of the manufacturing infrastructure (from millions of dollars to tens of thousands of dollars) compared with a silicon MEMS multiplexed electrospray source. The 3-D printed devices include features not easily attainable with other microfabrication methods, e.g., tapered channels and threaded holes. Through the optimization of the fabrication process 10-mm tall, isolated, straight, solid columns with diameter as small as 300 μm, and 12-mm long, straight tubes with inner diameter as small as 400 μm and wall thickness as small as 150 μm were demonstrated. Arrays with as many as 236 internally fed electrospray emitters (236 emitters in 1 cm2) were made, i.e., a twofold increase in emitter density and a sixfold increase in array size compared with the best reported values from multiplexed, internally fed, electrospray sources made of polymer. The characterization of devices with a different array size suggests a uniform emitter operation.
关键词： Additive manufacturing of MEMS,multiplexed liquid ionizers,electrospray,stereolithography
更新于2025-09-23 15:19:57