The design of a substrate greatly affects the residual stress distribution and the deformation behavior of the repaired region by a directed energy deposition (DED) process. The objective of the present study was to investigate effects of edge length and slope of the substrate on residual stress and deformation characteristics in the vicinity of the repaired region for the repair of the straight damaged region using a DED process. Two-dimensional finite element analysis (FEA) was carried out using SYSWELD. Materials of the substrate and deposited powders were AISI 1045. The maximum residual stress during the deposition decreased when the edge length of the substrate increased, but increased when the slope of the substrate increased. The residual stress after a cooling state increased when the edge length and the slope increased. The displacement of the specimen increased when the slope of the substrate augmented. Finally, the methodology to select a proper edge length and slope of the substrate are discussed in this study.
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Artificial Intelligence Technologies and Applications in Additive Manufacturing Selim Ahamed Shah, In Hwan Lee, Hochan Kim International Journal of Precision Engineering and Manufacturing.2025; 26(9): 2463. CrossRef
Metal additive manufacturing processes such as directed energy deposition process (DED), can be used to manufacture high value metal parts, with improved mechanical properties and efficiency. However, parts produced by DED can suffer from excessive temperature gradients, and heat accumulation due to the deposition process. The purpose of this study was to investigate the impact of the deposited area on thermos-mechanical characteristics for the case of deposition of Inconel 718 powder, on the AISI 1045 substrate, using the DED process through finite element analyses (FEAs). Nine types of FE models were developed. Temperature dependent cooling conditions were analyzed, and applied to the model. Laser heat source was defined, as the three-dimensional volumetric heat source based on the Gaussian distribution model. Temperature dependent properties were assigned to the models. The influence of the width and the length of the deposited region, on residual stress distributions in the vicinity of deposited region were investigated. Additionally, the impacts of the deposited area on deformation characteristics were examined.
Due to the pandemic of SARS-CoV-2 (COVID-19) virus, the demand for personal protective equipment (PPE), including face shield, ventilator value, and so on, has abruptly increased in the world. The collapse of the global supply chain of PPE has led to a shortage of the PPE. An additive manufacturing process has emerged as one of solutions to overcome such shortage. The objective of this study was to develop a reusable protective face shield using a material extrusion (ME) process. Five types of face shield were designed. Effects of the design on effective stress distribution, deformation, and specific rigidity were investigated through finite element analyses. To examine the influence of the design on deposition and post-processing characteristics, five types of face shield were fabricated from a ME apparatus. Post-processing characteristics and building time were greatly improved when Design 1 was adopted. In addition, the overall weight, wasted material, and buy-to-fly (BTF) ratio were significantly reduced when Design 1 was applied. Finally, results of wearing and droplet spreading experiments showed that the fabricated face shield for Design 1 was applicable to protection of droplet spreading.
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Additive manufacturing processes have been called by a wide variety of terms since the early days of development. As these names are often mixed academically and industrially, the demand for standardization of terms has gradually increased. Accordingly, the American Society for Testing Materials (ASTM) and the International Organization for Standardization (ISO) are in the process of establishing standards for the names and definitions of important terms related to additive manufacturing. Although Korea has also begun to establish KS standards based on ISO/ASTM standards, the Korean language and definitions of important terms related to additive manufacturing as defined by ISO/ASTM have not been fully organized. Therefore, the similar terms defined in ISO/ASTM in many academic and industrial literature are called by various Korean terms. Thus, this work deals with suggestions on the Korean terminologies and standardization of important terms related to additive manufacturing based on ISO/ASTM standards. Especially, this paper deals with the Additive Manufacturing and seven sub-process classifications.
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Metal additive manufacturing using electron beam melting (EBM) process applies electron beam for heating, sintering, and melting of powders to fabricate a three-dimensional component. The component may contain residual porosity internally and may be subjected to poor surface finish externally. To improve the quality of the surface finish and densification, re-melting is conducted. The purpose of this paper was to estimate the appropriate process conditions for a plasma electron beam remelting process using heat transfer finite element analyses (FEAs). The impact of the travel speed of table and thickness of the deposited part on temperature distributions were examined. The size of molten pool was estimated from the results of the thermal FEA. From the estimated size of molten pool, the travel speed of table and the hatch spacing between remelting tracks are discussed and selected as the appropriate process conditions for electron beam re-melting process from the perspective of minimum overlapping region of the molten pool.
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Heat transfer characteristics in the vicinity of irradiated region of the beam of a selective laser melting (SLM) process affect the creation of the melted region during the deposition. The creation of the molten pool is greatly influenced by laser parameters and powder characteristics. The goal of the paper is to investigate the influence of laser parameters and powder porosity on thermal characteristics in the vicinity of the molten pool of the SLM process through repeated finite element analyses (FEAs). The power and the scan speed are chosen as the laser parameters. The laser is assumed to be a volumetric Gaussian heat flux model. Materials of the powder and the substrate are chosen as SUS17-4PH and S45C, respectively. Temperature dependent thermal properties for those material are used to perform the FEA. An appropriate efficiency of the heat flux is predicted by comparing the results of FEAs and those of experiments. The influence of laser parameters on temperature distributions in the vicinity of the melted region and the formation of the molten pool is examined. In addition, the effects of porosity of powders on heat transfer characteristics in the vicinity of the melted region are discussed.
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It is compelling to realize that the additive manufactured part using wire feeding type directed energy deposition (DED) process is subjected to undesired thermal effects, and induced residual stress during the manufacturing process. In order to improve the quality of the manufactured part, the distributions of temperature and residual stress have to be understood to manage the results of the processing of these materials. The objective of this paper is to investigate the influence of the angle of corner deposition on the distributions of temperature and residual stress of the Ti-6Al-4V deposited bead, and the substrate via thermo-mechanical finite element analyses (FEAs). In the same fashion, the formation of the heat affected zone (HAZ) and the stress influenced region (SIR) are estimated from the measured results of the FEAs. Equally important, it can be stated that from the estimated HAZ and SIR regions, the overlapping of undesired thermal effects and residual stress between two beads fabricated by the wire feeding type DED process can be avoided at the design stage.
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The development of the lightweight sandwich plate with periodically repeated cores is one of hot issues to reduce the weight of the part. The behavior of the sandwich plate under static and dynamic loads is greatly influenced by the design of the cores. The aim of this paper is to investigate the effects of the corrugated angle on low velocity impact characteristics of the lightweight sandwich plate with corrugated cores. The corrugated core with the fold surface is designed to improve the joining characteristics between cores and skin sheets. The corrugated angle of the corrugated cores ranges from 45o to 90o. Specimens are manufactured from the fused deposition modeling (FDM) process. The characteristics of the fabricated specimen are investigated. Impact experiments are performed using a drop impact tester with a stretching type of fixture and the hemispherical nose of the impact head. From the results of the experiments, the influence of the impact energy and corrugated angle on the failure pattern of the lightweight sandwich plate is examined. The effects of the corrugated angle on critical impact energies for different failure patterns are investigated. Finally, the failure map of the lightweight sandwich plate with corrugated cores is estimated.
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The goal of this paper is to investigate the effects of out-of-plane deposition angle on product characteristics of a UV photo-curing process. Specimens are manufactured from a commercialized UV photo-curing machine, the NOBEL V1.0. The influence of the out-of-plane deposition angle of the specimen on surface characteristics, including morphology of the sloped surface, pick-to-pick distance of convex region, and roughness of the sloped surface, is examined via the observation of the sloped surface. In addition, the influence of the radius of curvature of the specimen on the surface roughness of the sloped surface is evaluated. The effects of the out-of-plane deposition angle on impact strength of specimens are investigated via Izod impact experiments. Finally, we discuss the influence of the out-of-plane deposition angle on failure characteristics of specimens for impact loads.
The runner system of the injection mould and the injection volume of the injection molding process greatly affect the quality of the produced part. The goal of this paper is the design of the runner system and the prediction of the injection volume for the injection moulding of a housing part of small-size air cleaner to improve the formability through the three-dimensional injection moulding analysis. The effects of the runner system of the mould on the injection moulding characteristics are investigated. From the results of the investigation, a proper design of the runner system with uniform filling characteristics and the minimized defect formation is obtained. In addition, the influence of the moving distance of the screw on filling characteristics, weldline formation and deformation characteristics is examined. From the results of the examination, an appropriate moving distance of the screw for the housing part of small-size air cleaner is estimated.
The aim of this paper is to investigate the improvement of surface characteristics of Stellite21 deposited layer by powder feeding type of direct energy deposition (DED) process using a plasma electron beam. Re-melting experiments of the deposited specimen is performed using a three-dimensional finishing system with a plasma electron beam. The acceleration voltage and the travel speed of the electron beam are chosen as process parameters. The effects of the process parameters on the surface roughness and the hardness of the re-melted region are examined. The formation of the re-melted region is observed using an optical microscope. Results of these experiments revealed that the re-melting process using a plasma electron beam can greatly improve the surface qualities of the Stellite21 deposited layer by the DED process.
We explored localized plasmonic field enhancements using nanowire patterns to improve the sensitivity of a surface plasmon resonance (SPR) sensor. Two different materials, gold and silver, were considered for sample materials. Gold and silver nanowire patterns were fabricated by electron beam lithography for experimental measurements. The wavelength SPR sensor was also designed for these experiments. The material-dependent field enhancements on nanowire patterns were first calculated based on Maxwell’s equations. Resonance wavelength shifts were indicated as changes in the refractive index from 1.33 to 1.36. The SPR sensor with silver nanowire patterns showed a much larger resonance wavelength shift than the sensor with gold nanowire patterns, in good agreement with simulation results. These results suggest that silver nanowire patterns are more efficient than gold nanowire patterns, and could be used for sensitivity enhancements in situations where biocompatibility is not a consideration.
A powder spreading phenomenon is one of disadvantageous characteristics of the powder bed fusion process using electron beams. The powder spreading phenomenon can be controlled using a pre-heating process of metallic powders. The aim of this paper was to investigate the preheating process of Stellite21 powder using electron beams. Powder spreading experiments were performed to examine the influence of process parameters on the spreading behaviors of Stellite21 powder. Powder heating experiments were carried to investigate the effects of the focusing current of the electron beam on the quality of the heated region. Using the results of the powder spreading and heating experiments, an appropriate combination of process parameters was obtained. The pre-heating experiment of Stellite21 was performed using the estimated combination of process parameters. The results of preheating experiments showed that the preheated Stelllite21 layer with desired characteristics can be created when the estimated combination of process parameters is applied.
For a stable electric power supply in the space, nuclear batteries have been used as the main power source in a spacecraft owing to their long lifetime and high reliability. In accordance with the plan for lunar mission in Korea, nuclear batteries will supply electricity to the rover that needs to be developed. According to the information about the estimated payload, Korea Atomic Energy Research Institute started with the conceptual design based on the previous studies in USA and Russia. Because a nuclear battery converts the decay heat of the radioisotope into electricity, thermal design, radiation shield, and shock protection need to be considered. In this study, two types of nuclear batteries, radial type and axial type, were designed according to the alignment of the thermoelectric module. Heat transfer analyses were performed to compare their thermoelectric efficiency, and test mockups were fabricated to evaluate their performances.
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