Vitreous carbon (VC) is an excellent material for glass molding due to its high hot hardness and low adhesion to glass materials. As a low-cost VC micro/nano mold fabrication method, carbonization of replicated Furan precursor has been investigated for various glass molded micro/nano optical and fluidic devices. One of the critical issues identified in the method is the substantial pyrolysis shrinkage (~22%) during the carbonization process. In this study, a method of minimizing pyrolysis shrinkage by adding VC powder to the initial Furan resin mixture was investigated. The mixing ratio of Furan resin, initiator, and ethanol was experimentally optimized for each VC powder mixing ratio, and the effects of the VC powder mixing ratio on the pyrolysis shrinkage of VC mold were examined. As the VC powder mixing ratio increased from 0% to 40%, we observed a reduction in the shrinkage ratio from 22.18% to 12.89% aligning closely with theoretical expectations.
Knee contact forces and knee stiffness are biomechanical factors worth considering for walking in knee osteoarthritis patients. However, it is challenging to acquire these factors in real time; thus, making it difficult to use them in robotic rehabilitation and assistive systems. This study investigated whether trained deep neural networks (DNNs) can capture the biomechanical factors only using kinematics during gait, which is possible to measure via sensors in real time. A public dataset of walking on the ground was analyzed through biomechanical analysis to train and test DNNs. Using the training dataset, several DNN topologies were explored via Bayesian optimization to tune the hyperparameters. After optimization, DNNs were trained to estimate the biomechanical factors in a supervised manner. The trained DNNs were then evaluated using two new datasets, which were not used in the training process. The trained DNNs estimated the biomechanical factors with a high level of accuracy in both types of test datasets. Results confirmed that DNNs can estimate the biomechanical factors based on only kinematics during gait.
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
In this work, we present an experimental study on cutting force and chip shrinkage coefficient during the milling of SKD11 steel at elevated temperatures using a high-frequency induction heating method. To improve the determination of the chip shrinkage coefficient, a 3D scanning method incorporating GOM Inspect 3D data analysis software was used to measure the chip length. To evaluate the effect of the heating process on output data such as chip geometry, cutting force, and chip shrinkage coefficient, cutting experiments were conducted at room and elevated temperatures with the same machining parameters of cutting speed, feed rate, and cutting depth. The Taguchi orthogonal array method was subsequently used for experimental design to obtain optimum values of the machining parameters. The analysis of variance method was also performed to indicate the percentage effect of the machining parameters on the cutting force and chip shrinkage coefficient. Finally, models of the cutting force and chip shrinkage coefficient during thermal-assisted milling of SKD11 were established and compared with experimental data.
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The influence of induction-assisted milling on the machining characteristics and surface integrity of γ-TiAl alloys Tao Fan, Changfeng Yao, Liang Tan, Yilong Cao, Yunqi Sun, Wenhao Tang Journal of Manufacturing Processes.2024; 118: 215. CrossRef
Assessment of the Effect of Thermal-Assisted Machining on the Machinability of SKD11 Alloy Steel Thi-Bich Mac, The-Thanh Luyen, Duc-Toan Nguyen Metals.2023; 13(4): 699. CrossRef
The Impact of High-Speed and Thermal-Assisted Machining on Tool Wear and Surface Roughness during Milling of SKD11 Steel Thi-Bich Mac, The-Thanh Luyen, Duc-Toan Nguyen Metals.2023; 13(5): 971. CrossRef
The manufacture of BLAC motor requires the motor stator (electric steel plate) and the motor case (aluminum die casting material) maintain strong contact to support the resistance of rotating moments against the rotational moments of the rotor. If there is small reverse rotational moment, the motor stator rotates easily, and damages the motor. To prevent a strong reverse rotational moment, interference fit between the motor stator and the motor case manufactured through heat shrinkage is required. This study, considers the tolerances that may occur in the manufacturing process of assembling stator and case, the contact pressure range that can occur in the heat shrinkage and the moments that can be supported by the motor stator. These are verified through the finite element analysis. The result validates finite element analysis as compared with theoretical values.
To solve the limitation of motion synchronization measurement method applied to medical rehabilitation in most laboratories, a new method to measure the change of metabolic costs with or without a military exoskeleton on an external field environment has been proposed. The relationship between oxygen consumption and heart rate in male subjects aged 20- 30 years is analyzed and an equation that estimates oxygen consumption by heart rate was derived using a multiple regression analysis. An evaluation model which verifies the effectiveness of military exoskeleton was established for specific military scenarios utilizing exoskeleton. As a result, the proposed method is simple and effective for quantitative evaluation of exoskeleton system and can be a substitute of the evaluation methods for the metabolic costs or movement synchronization between human and exoskeleton.
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