The future mobility industry is increasingly utilizing advanced tools for cutting and machining lightweight parts to enhance the fuel efficiency of automotive engines. Machining companies are turning to polycrystalline diamond (PCD) tools to boost productivity in the production of these lightweight components. PCD tools provide exceptional machining performance and a long service life, making them ideal for high-mix, low-volume production, which often involves customized requirements for various materials. To further improve efficiency, this study explores the application of metal 3D printing technology in the manufacturing of PCD tools. This technology allows for the creation of PCD tools with superior cutting performance and wear resistance, tailored for high-speed machining of lightweight materials, including complex shapes. Thus, research into this area is essential. In this study, we manufactured boring tools by brazing PCD tips onto three different laminated structures created using Fused Deposition Modeling (FDM), a method within metal 3D printing technologies. We then evaluated the fabricated boring tools through comparative machining experiments against existing sintered PCD boring tools. The results indicated that the 3D-printed solid tools demonstrated no significant differences in machining accuracy or surface quality compared to the conventional tools.
Carbon capture and storage is a vital strategy for mitigating rising atmospheric carbon dioxide, and metal–organic frameworks (MOFs) have gained attention as promising sorbents. Numerous simulations have examined factors governing CO2 capture in MOFs—such as diffusion in MOF-74 under varying temperatures and process modeling of MOF-5—but most were limited to specific structures or conditions, hindering a systematic understanding of diffusion across diverse MOFs. Conventional computational methods also face constraints: density functional theory mainly provides static energy evaluations, while molecular dynamics relies on fixed force fields with poor transferability and an inability to describe reactive events. To overcome these limitations, this study employs molecular dynamics simulations driven by neural network potentials to evaluate CO2 diffusivity in 17 types of MOFs. Results reveal significant variation in transport behavior, with zeolitic-imidazolate framework-3 showing the highest diffusivity and MOF-74 the lowest—an approximately 19-fold difference. These findings highlight the capability of neural-network-based molecular dynamics to deliver consistent and quantitative assessments of CO2 transport in MOFs, providing a reliable framework for the rational design of next-generation capture materials.
Secondary batteries are crucial for eco-friendly systems, but existing technologies struggle with energy density and safety issues. This study aims to develop a next-generation battery utilizing quasi-solid electrolytes (QSE), which combine the advantages of both liquid and solid electrolytes. However, QSEs often lack the mechanical strength necessary to prevent lithium dendrite growth. To address this challenge, two strategies were proposed and experimentally validated. The first strategy involves creating a QSE-separator composite (QSE-PI) by integrating QSE with a polyimide (PI) separator. Among the various options, PI with a thickness greater than 20 μm and a pore size of 2-5 μm exhibited superior electrolyte absorption and dendrite suppression. This configuration allowed for rapid lithium plating/stripping, high ionic conductivity (1.7 × 10-3 S cm-1), and excellent Coulombic efficiency (99.94%).The second strategy incorporates silica (SiO2) as a ceramic filler in the QSE-PI to enhance mechanical strength and ion transport. The addition of SiO2 disrupted polymer crystallinity, increased the amorphous regions, and effectively suppressed dendrite formation. Notably, SiO2 particles larger than 10 μm improved cycle stability, with the composite maintaining performance for over 50 cycles, compared to only 30 cycles for the version without filler.
This paper extensively explores and analyzes the latest research trends in Ionic Polymer-Metal Composites (IPMC) sensors. IPMC sensors are known for their flexibility, lightness, and high responsiveness. They show great promise across different fields. They can respond sensitively to various stimuli such as mechanical deformation, humidity, and pressure, making them ideal for bio-responsive detection, health monitoring, and energy harvesting. This paper introduces actuation and sensing mechanisms of IPMCs, discusses their manufacturing processes, and explores how these processes can influence the responsiveness and stability of sensors. Moreover, through case studies of IPMC-based research that can perform self-sensing functions, it presents possibilities brought by the integration of sensors and actuators. This paper emphasizes the potential for research and development of IPMC sensors to expand into various industrial fields and explores ways to continuously improve the accuracy and reliability of sensors. IPMC-based sensors are expected to play a significant role in advancing medical devices and wearable technologies, thereby facilitating innovation in the field.
This study focuses on preventing folding defects in the forging process of parachute harness parts. Through three- dimensional finite element analysis, it was determined that folding defects arise from uneven metal flow and timing differences in the filling of various regions. To address these issues, a preform die was designed and evaluated using multi-stage forging simulations. The results indicated that the preform die facilitated uniform metal flow, preventing folding defects and ensuring consistent filling across all key areas. To verify the simulation results, surface and cross-sectional metal flow analyses were conducted. Additionally, the preform die reduced the maximum die load, which is expected to extend die lifespan and improve overall process efficiency. These findings demonstrate that precise control of metal flow and the application of a preform die can significantly enhance the quality and durability of forged components, providing valuable insights for improving forging processes across various industries
In this study, to improve the performance of a solid oxide fuel cell based on a porous metal support, a fuel cell using a multi-layered anode functional layer was fabricated and electrochemical performance analysis was performed. Surface and cross-sectional microstructures according to particle size control were confirmed through FE-SEM. The pore size of the multi-layer anode functional layer was gradually reduced compared to that of a single-structure anode functional layer. As a result, it was confirmed that the surface roughness was lower than that of the single structure. This led to a reduction in polarization resistance through smooth transmission of gas generated from the electrode. As a result, it was confirmed that electrochemical performance was improved by more than 1.25 times in fuel cells using a multi-layered anode functional layer compared to that with a single structure.
This research developed a CAM S/W, which generates an adaptive 5-axis tool path, to optimize the quality of Direct Energy Deposition (DED) 3D printing. After reconstructing part shapes and generating printing paths in each shape, the path simulation including automatic collision detection was implemented. Productivity and printing quality were improved through equipment improvement and process optimization. In addition, high-quality parts with desirable physical and mechanical properties were produced by generating an adaptive 5-axis path specialized in the printing process that reflects various physical phenomena and monitoring results. Finally, the performance of CAM S/W was verified through the production of prototypes for industrial components.
This study performed high-frequency heat treatment experiments and simulations of the park gear of an automobile transmission. The heating temperature and hardening depth were measured during high-frequency heat treatment. Moreover, by applying the resonance RCL circuit, the current value of the coil during high-frequency heat treatment, the electromagnetic and heat transfer material properties dependent on the temperature, and the phase transformation function were all applied to the simulation. In the high-frequency heat treatment experiment, the heating temperature was 977.4℃ and the 1st direction hardening depth was 1.5 mm, the 2nd direction hardening depth was 3 mm, and the 3rd direction hardening depth was 2.5 mm, and the reliability was verified by comparing the simulation heating temperature of 1,097℃ and the 1st direction predicted hardening depth of 1.6 mm, the 2nd direction predicted hardening depth of 2.8 mm, and the 3rd direction predicted hardening depth of 2.7 mm. The error rate of the heating temperature results was 12.2% whereas that of the hardening depth results was 7.1%.
In this study, the production process of eccentric head bolts that fasten flanges for water supply pipe connections, which can only be achieved through the cold forging process, was improved. For axial forging, forming analysis was performed for a 200-ton header machine to check the raw material specifications, forming load, and metal flow improvements suitable for forming. The analysis found that the forging of high-strength bolts of M14×65 ㎜ with eccentric heads was possible under the maximum load condition of 137.2 tons with low carbon boron steel of ø13.8×89.7 ㎜ and 105.2 g. By mounting the prototype mold on the header machine, it was possible to prevent metal flow breakage, as shown by the trial mass production test. It was possible to improve the strength of the eccentric head bolt and reduce the weight of the input material through the cutting process. Therefore, manufacturing costs could be reduced.
We have developed a direct conductive patterning method with micro-scale line widths using the laser-induced-forward transfer (LIFT) and liquid metal. As this method does not need post-thermal processing, there is no thermal damage even on heat-sensitive polymer substrates by low-power laser irradiation on the dynamic release layer (DRL). Unlike other liquid metal patterning processes, this procedure can easily achieve fine line widths of a few tens of micrometers corresponding to laser spot size. The solid-state UV pulse laser with 266 nm wavelength and 20 ns pulse duration was used to transfer Eutectic Gallium Indium (EGaIn) liquid metal and the results for the single and multi-pulse laser irradiation were investigated to determine the effective process conditions. The applicability of flexible circuit fabrication and selective circuit repair was successfully tested on Polyimide (PI) substrate. After the LIFT process, the electrical properties of liquid metal on the pattern were measured to be approximately 5~8 x 10-3 Ω/m of resistance.
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Study on Micro Grooving of Tungsten Carbide Using Disk Tool Min Ki Kim, Chan Young Yang, Dae Bo Sim, Ji Hyo Lee, Bo Hyun Kim Journal of the Korean Society for Precision Engineering.2024; 41(2): 123. CrossRef
In this study, we demonstrated a triboelectric nanogenerator composed of a vertical column, and a cylindrical shell, for omnidirectional wind energy harvesting. With a simple structure using a metal wire, the height between the two triboelectric materials can be maintained, and the Al coated shell can also be electrically connected to the electrode. When the shell is deformed by wind, its Al layer and Polytetrafluoroethylene (PTFE) on the outside of the column can be triboelectrically charged. Thus, wind energy can be harvested through a triboelectric energy conversion mechanism. In particular, due to the high flexibility of the shell, the nanogenerator operates even at wind speeds as low as 1 m/s. Although the output voltage is asymmetrical depending on the wind direction due to the metal wire, it was experimentally confirmed that the device can harvest wind energy from all directions. The measured output RMS power was approximately 15 μW at a wind speed of 6 m/s.
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The ultrasonic metal welding technique has been widely used because of the need to weld different materials for meeting high quality performance requirements. The key part in this type of welding is the horn, which plays an important role in the weld quality. Longitudinal vibration has so far been the most popular vibration mode for ultrasonic horns, but the longitudinal mode coupled with torsional mode is gaining a lot of attention these days owing to its better performance compared to the pure longitudinal mode. Although there are many studies on the performance of these two mode horns, comparative studies based on the performance of these two modes, particularly in ultrasonic metal welding, are very rare. This study focuses on the welding performance comparison of these two horns with 20 kHz resonant frequency. Experimental results show that the performance of the longitudinal-torsional horn is better than that of the longitudinal horn in terms of welding strength.
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The necessity of converting toxic gas has arisen from the usage of perfluorinated compounds (PFCs), volatile organic compounds (VOCs), and hydrocarbon gases in the semiconductor process and laboratories. Also, recent strong regulations on the emission gas from vehicles also present the need for the highly efficient chemical conversion of toxic emission gases. In this study, we present the fabrication of platinum and ruthenium alloy metal catalysts on the yttria-stabilized zirconia balls, and the application of the metal catalysts to the catalytic converter for methane oxidation. The platinum and ruthenium alloy metal catalysts showed better performance than the platinum catalyst, i.e., 75% increase in the methane conversion efficiency at 500℃. Such improvement seems to be because of the facile oxygen supply from the ruthenium surface. Also, the platinum and ruthenium alloy catalysts with the doped cerium oxide interlayer showed better thermal stability than the platinum and ruthenium alloy metal catalysts, possibly because of the stronger bonding between the metal and oxide support.
Incremental sheet metal forming can be used to manufacture various products without the punch and die set. However, it is difficult to manufacture the desired shape due to section deflection and springback of the sheet. Section deflection is caused by the force of the blank holder for fixing the sheet and the tool for forming the sheet. In this study, we analyzed the characteristics of the section deflection according to the geometries of the circular cup shapes in the sheet incremental forming process. The section deflection increased with an increase in the entering radius and forming angle in the section deflection region. However, section deflection was constant according to the exit radius. In addition, the secondary forming process for reducing the shape error was introduced. The secondary incremental forming process was conducted in the opposite direction. Characteristics of the shape error according to the entering depth of the tool among the forming parameters for reducing the shape error of the cup shape were analyzed. The springback in the cup-shape was reduced by the additional forming process with an optimum entering depth of the tool.
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Study on the Incremental sheet metal forming process using a metal foam as a die Jae-Hyeong Yu, Kyu-Seok Jung, Mohanraj Murugesan, Wan-Jin Chung, Chang-Whan Lee International Journal of Material Forming.2022;[Epub] CrossRef
Study on the Incremental Sheet Forming Process with the Ball Type Tool Jun-Hyun Kyeong, Byeong-Hyeop Lee, Sun-Jae Lee, Kyeong-Hoon Cho, Hyung-Won Youn, Chang-Whan Lee Journal of the Korean Society for Precision Engineering.2022; 39(5): 371. CrossRef
Tool Path Design of the Counter Single Point Incremental Forming Process to Decrease Shape Error Kyu-Seok Jung, Jae-Hyeong Yu, Wan-Jin Chung, Chang-Whan Lee Materials.2020; 13(21): 4719. CrossRef
As products life cycles are becoming shorter, the reduction of die and mold manufacturing cost and time is becoming more crucial in the machinery, automotive, and electronics industries. Over the past decades, many initiatives have been made to develop high performance free-machining steels without significant degradation of mechanical properties. To develop a modified AISI P20 free-machining steel, we studied the effects of B, N, and S additives on the variations of the cutting forces and metal structures such as grain size, density, and distribution of free-machining inclusions. From a set of experiments, it was observed that an appropriate addition of B and N additives reduces the resulting cutting force by approximately 6.3% and delays the tool wear progress. During the solidification B and N additives form hBN precipitates, with a layered and planar structure, within the steel matrix. The hBN precipitates’ weak shear strength results in lowering the required milling force. It is also confirmed that machinability is prominently improved when a large number of microsized hBN precipitates are distributed uniformly in the steel matrix. This study could contribute to the development of high performance BN-added free-machining steels for die and mold applications.
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