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
This study developed a defect-detecting system for automotive wheel nuts. We proposed an image processing method using OpenCV for efficient defect-detection of automotive wheel nuts. Image processing method focused on noise removal, ratio adjustment, binarization, polar coordinate system formation, and orthogonal coordinate system conversion. Through data collection, preprocessing, object detection model training, and testing, we established a system capable of accurately classifying defects and tracking their positions. There are four defect types. Types 1 and 2 defects are defects of products where the product is completely broken circumferentially. Types 3 and 4 defects are defects are small circumferential dents and scratches in the product. We utilized Faster R-CNN and YOLOv8 models to detect defect types. By employing effective preprocessing and post-processing steps, we enhanced the accuracy. In the case of Fast RCNN, AP values were 0.92, 0.93, 0.76, and 0.49 for types 1, 2, 3, and 4 defects, respectively. The mAP was 0.77. In the case of YOLOv8, AP values were 0.78, 0.96, 0.8, and 0.51 for types for types 1, 2, 3, and 4 defects, respectively. The mAP was 0.76. These results could contribute to defect detection and quality improvement in the automotive manufacturing sector.
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Large-area Inspection Method for Machined Micro Hole Dimension Measurement Using Deep Learning in Silicon Cathodes Jonghyeok Chae, Dongkyu Lee, Seunghun Oh, Yoojeong Noh Journal of the Korean Society for Precision Engineering.2025; 42(2): 139. CrossRef
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.
This paper investigated the hot deformation behavior of an AISI 4340 material through high-temperature compression experiments. The compression tests were performed to obtain stress-strain curves at processing temperatures of 900, 1,000, 1,100, and 1,200℃, and the strain rates of 0.01, 0.1, 1, and 10 s-1 up to a true strain of 1.0 in the high-temperature compression mode of Gleeble® 3,500. A novel 3D processing map, constructed through power dissipation efficiency and Ziegler"s instability criterion, is proposed. The deformation behavior was analyzed by observing changes in the microstructure from the high-temperature compression tests. Electron back scatters diffraction (EBSD) was used to characterize the microstructures for various processing parameters. The process workability of finite element analysis (FEA) was examined in the deformation flow instability map in the three-dimensional space for each strain. As a result, each particle"s strain rate and temperature of FEA data can be observed in a three-dimensional flow instability map to control the temperature and process speed to avoid unstable zones.
Process and die design of cold forging for the asymmetric part, engine mount adapter has been studied. Forging of the asymmetric part frequently causes die failure because of the high forging load and local stress concentration of the die. Thus, performing process design of cold forging to minimize forging load is required. Preform for the engine mount adapter was chosen based on the forging load and filling rate of forgings by the finite element analysis. In the die design, number of stress rings, interface radius, and relative interference were investigated in several cases with maximum principle stress by the finite element method. The shape of the die was determined by comparing the load changing the radius of the flange area. Also, the life of the designed die was calculated using the Goodman theory by cyclic fatigue loading. As a result, it was confirmed that the calculation life and results of the test were identical. In this study, it is verified that stress concentration and fatigue life should be considered simultaneously in the design of cold forging die for the asymmetric part.
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Analyzing Cold Heading of Self-Piercing Rivet Using FEM Sangchul Lee, Jaeho Hyun, Seung-Woo Hong, Kwon Hee Won, Heesoo Park, Soongkeun Hyun, Sang-Yeol Kim Journal of the Korean Society of Manufacturing Technology Engineers.2022; 31(1): 19. CrossRef
Mold-design Verification of Ball Housing Insert Die in Non Processing Type Multi-stage Cold Forging Won-Seok Hwang, Jong-Won Choi, Eu-Enn Jung, Myungchang Kang Journal of the Korean Society of Manufacturing Process Engineers.2021; 20(12): 8. CrossRef
A Study on the Elimination of Surface Defect and Increase in Tool Life of the Warm Forged Spider Jong-Hun Kang Journal of the Korean Society of Manufacturing Process Engineers.2020; 19(5): 82. CrossRef
The blade cylinder root is a key component connecting the blade and pitch bearing of a wind turbine and is 20% of the blade’s manufacturing cost. Blade cylinder roots are manufactured using the open die forging method with steel alloy. However the blade cylinder root for 750 KW class wind turbine is manufactured using AA5083 cast material to reduce weight. The purpose of this study is to develop a hot open die forging method, through experiment and FEA, using AA5083 material manufactured by continuous casting. The forging process was designed using the mandrel forging method. Hot compression tests were conducted to obtain flow stress of cast microstructure at different temperatures and strain rates. Control parameters of each forging process were analyzed/compared to predict adaptability of the mandrel forging process. High productivity, good internal quality, shapes, and dimension were verified by prototypes manufactured by the proposed forging process.
A multi-step warm forging process for subminiature screws is investigated. Due to the low formability of Titanium alloys, bit forming of Titanium screws is difficult by cold forging. In order to overcome this low formability of Titanium alloys, two candidate processes, i.e., multi-step forging and warm forging are introduced. First, a multi-step (two-step) forging process is investigated. The punch shape and stroke of forging during the first step is designed via various analyses. Finally, the bit formability is investigated at different forging temperatures. Analyses are carried out for two-step forging at various temperatures and the formability under these thermal conditions is compared.
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Flow behavior dependence of rod shearing phenomena of various materials in automatic multi-stage cold forging Kwang Min Kim, Su Min Ji, Seong Won Lee, Seok Moo Hong, Man Soo Joun Journal of Mechanical Science and Technology.2023; 37(1): 139. CrossRef
Characterization of Ti-6Al-4V alloy in the temperature range of warm metal forming and fracture analysis of the warm capping process Su Min Ji, Seong Min Jang, Young Seop Lee, Hee Man Kwak, Jeong Muk Choi, Man Soo Joun Journal of Materials Research and Technology.2022; 18: 1590. CrossRef
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