Journal of the Korean Society for Precision Engineering

Development of the Fretting Corrosion Test Equipment for the Automotive Electrical Connector: Jeong Hyun Kim, Sang Hoon Lee; J. Korean Soc. Precis. Eng. 2026;43(1):21-28.
Published online January 1, 2026; DOI: https://doi.org/10.7736/JKSPE.025.029

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Fretting corrosion results from microscopic abrasion of connector contacts and is influenced by environmental conditions in automotive applications. This study designed and fabricated test equipment capable of evaluating fretting corrosion characteristics at low temperatures. A temperature–humidity environmental chamber was used, and a compact test jig box was created to fit inside it. The specimen was positioned outside the box and fully exposed to low temperatures, while the driving components were enclosed inside the box. To ensure their reliable operation, warm air was supplied using vortex tubes, maintaining the internal box temperature above 0oC even when chamber conditions reached −40℃. A hemispherical-tip jig was also produced to enable consistent specimen preparation. Experiments conducted at −40℃ used a constant current–resistance method to measure output signals. The system successfully captured accurate and stable resistance changes corresponding to displacement cycles. These findings indicate that the developed equipment provides stable low-temperature operation and reliable measurement performance. Therefore, the system is expected to support fretting corrosion characterization across a wide range of environments, including low-temperature, high-temperature, and temperature-cycling conditions.

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A Review of in Operando Measurements of Local Temperature for Lithium-ion Batteries: Soyoung Park, Woosung Park; J. Korean Soc. Precis. Eng. 2025;42(12):1021-1035.
Published online December 1, 2025; DOI: https://doi.org/10.7736/JKSPE.025.00024

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Sensing the internal temperature of lithium-ion batteries is particularly useful for reliable battery operation as both electrochemistry and mass transport are dictated by local temperature. In this article, we review in operando techniques to monitor the internal temperature of lithium-ion batteries during charging and discharging. We categorize existing techniques into two groups: invasive and non-invasive approaches. Invasive techniques include optical fibers, thermocouples, and resistance temperature detectors as a thermometer. Non-invasive methods cover the temperature estimation techniques, namely electrochemical impedance spectroscopy as well as X-ray thermometry. For both approaches, we review working principle of thermometry, pros and cons of each thermometry, and recent studies to tackle relevant technical challenges. This review provides useful information for internal temperature measurements, offering chances for thermally reliable battery operation.

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The Design of an Electrode Performance Evaluation Platform of Low-temperature Solid Oxide Fuel Cells for High-efficiency Biogas Energy Conversion: Sanghoon Ji, Weonjae Kim, Soyoung Baek; J. Korean Soc. Precis. Eng. 2025;42(12):1011-1020.
Published online December 1, 2025; DOI: https://doi.org/10.7736/JKSPE.025.00018

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This study presents a performance evaluation platform for sputtered thin-film electrodes used in biogas-driven, low-temperature solid oxide fuel cells (SOFCs). The design considerations include electrolyte material composition and thickness, anode material composition and thickness, anode fuel composition, and cathode composition and thickness, all derived from a review of existing literature. For the electrolyte, we propose a thickness of 100 μm for the main electrolyte made of gadolinium-doped ceria (GDC) and 0.1 μm for the auxiliary electrolyte made of scandia-stabilized zirconia. In terms of anode fabrication, we suggest a material composition of Ru/Ni-Cu-GDC, with thicknesses of 1 μm for Ni-Cu-GDC and a few nanometers for Ru in the nanoporous anode. For the anode fuel supply, we recommend mole ratios of 45% to 75% CH₄ and 25% to 55% CO₂ to assess the impact of biogas composition on power performance. Lastly, for the cathode, we propose a material composition of Pt-Ti-samarium-doped ceria with a thickness of 100 nm for the nanoporous structure.

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A Study on the Performance Enhancement of Solid Oxide Fuel Cells by Controlling the Infiltration Molar Concentration of PNO: Miju Ku, Jisung Yoon, Young-Beom Kim; J. Korean Soc. Precis. Eng. 2025;42(11):943-947.
Published online November 1, 2025; DOI: https://doi.org/10.7736/JKSPE.025.076

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In this study, we employed an infiltration technique to create a nanostructured functional layer, enhancing the electrochemically active area in solid oxide fuel cells (SOFCs). We infiltrated Pr₂NiO_4+δ (PNO) into a porous GDC electrolyte, resulting in a nanostructured catalytic layer. We characterized its microstructure and cross-sectional morphology using field-emission scanning electron microscopy (FE-SEM). The electrochemical performance was assessed at 750°C with a NiO-YSZ/YSZ/GDC half-cell configuration. The reference cell without PNO infiltration achieved a maximum power density of 2.07 W/cm², while the cell with 0.05 M PNO infiltration reached an improved value of 2.55 W/cm². These results demonstrate that by optimizing the infiltration concentration of PNO, we can fabricate a high-performance nanostructured functional layer without adding extra thickness, confirming infiltration as an effective strategy for enhancing SOFC performance.

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A Numerical Investigation on Heat Transfer Enhancement of a Dual-impeller Heat Exchanger for Electro-optical Tracking System Cooling via System Structural Modification: Sungbin Lee, Manyul Jeon, Hyungpil Park, Donghyeok Park, Hoonhyuk Park, Jongin Bae, Heesung Park; J. Korean Soc. Precis. Eng. 2025;42(10):871-877.
Published online October 1, 2025; DOI: https://doi.org/10.7736/JKSPE.025.071

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This study presents a dual-impeller air-cooled heat exchanger aimed at improving thermal management in electro-optical tracking systems operating under high power density. Two geometric modifications were introduced to enhance flow characteristics and heat transfer performance: the curvature of the center plate and the integration of a pin-fin structure at the outlet. Through numerical simulation, the improved model demonstrated more efficient internal flow compared to the original model, achieved through enhanced inflow characteristics and reduced flow separation. The pin-fin structures induced localized turbulence and recirculation zones, contributing to an increased thermal exchange surface area and longer effective heat transfer time. Consequently, the outlet temperature of the internal system decreased by an average of 1.4°C across various rotational speeds, resulting in a 5.9% increase in heat exchanger efficiency compared to the original model. Overall, this study shows that structural enhancements in heat exchanger design can significantly improve the cooling performance of high-power electronic systems, suggesting practical applicability for advanced thermal management solutions.

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Effect of the Internal Thermometer for Room Temperature Compensation on the Calibration Uncertainty of Thermocouple Indicators: Joo Gyeong Kang, Young Hee Lee, Inseok Yang; J. Korean Soc. Precis. Eng. 2025;42(1):39-45.
Published online January 1, 2025; DOI: https://doi.org/10.7736/JKSPE.024.105

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Most temperature indicators that use thermocouples as sensors include an internal thermometer for compensating room temperature variations. This thermometer measures ambient temperature, which is then converted to a thermoelectric voltage. This voltage is added to the electromotive force measured in the thermocouple sensor and then converted back to temperature. Although precise calibration of the indicator can be conducted in a controlled room-temperature environment, additional uncertainty arises due to room temperature compensation during actual measurements. To address this issue, we calibrated temperature indicator at the ice point. In this experiment, the indicator was placed in an environment where the temperature varied between 8 and 38oC, demonstrating its dependency on ambient temperature. In a second set of experiments, we shorted the thermocouple input terminal to verify whether the indicator correctly indicated the ambient temperature. This study proposed a method to assess additional uncertainty that must be considered when using a thermocouple connected to an indicator calibrated with an external ice point in a laboratory. It also highlights additional steps and factors to consider during the calibration of temperature indicators that employ internal temperature compensation.

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Progresses in Pneumatic Temperature Control Technique for Ultra-Precise Control and Measurement of Thermal Environment: Bomi Nam, Wukchul Joung; J. Korean Soc. Precis. Eng. 2024;41(10):759-776.
Published online October 1, 2024; DOI: https://doi.org/10.7736/JKSPE.024.081

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In this paper, we introduce a new pneumatic temperature control technique and its application to precision thermometry. The method controls temperature by adjusting gas pressure through the unique thermohydraulic linkage of the pressure-controlled loop heat pipe (PCLHP). Due to this temperature-pressure linkage, the PCLHP-based pneumatic temperature control achieves exceptional control speed, stability, and precision. To fully understand this method, we systematically investigated the effects of various influencing parameters, such as heat load, sink temperature, and rate of pressure change, on the stability of temperature control. In addition, we successfully achieved closed-type pneumatic temperature control using a mechanically-driven gas pressure controller. We also developed a hybrid PCLHP that incorporates a heat pipe liner into the isothermal region to further improve the temperature uniformity of the pneumatically-controlled temperature field. With this technique, we significantly improved the accuracy of the fixed point of the International Temperature Scale of 1990 by using inside nucleation of the freezing temperature of tin and determining the liquidus temperature of tin. In this paper, we summarize the results of these diverse efforts in characterizing the pneumatic temperature control technique, along with theoretical analyses.

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The Surface Temperature Monitoring of Brake Disc in Railway Vehicle: Jeongguk Kim, Sungil Seo; J. Korean Soc. Precis. Eng. 2024;41(9):693-698.
Published online September 1, 2024; DOI: https://doi.org/10.7736/JKSPE.024.070

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In mechanical braking systems, there are hot spots on the surface of a braking disc due to thermal deformation with a high thermal gradient. Controlling such hot spots is important for extending the life of a braking disc. In this study, surface temperatures of railway brake discs were monitored using infrared (IR) thermal imaging technique. A highspeed infrared camera with a maximum speed of 380 Hz was used to monitor surface temperature changes of the braking disc. Braking tests were performed with a full-scale dynamometer. During the braking test, the surface temperature change of the braking disc were monitored using a high-speed infrared camera. Hot spots and thermal damage observed on the surface of railway brake discs during braking tests were quantitatively analyzed using infrared thermographic images. Results revealed that monitoring disc surface temperature using IR thermographic technique can be a new method for predicting surface temperature changes without installing a thermocouple inside the disc.

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Development of a Vertical Burner Rig Using Methane Flame: Soo Park, Dae-Jin Kim, Jun-Young Kim, Seong-Ju Kim, Ki-Yong Lee, Jeong-Min Kim, Hyung-Ick Kim, Chang-Sung Seok; J. Korean Soc. Precis. Eng. 2024;41(8):653-661.
Published online August 1, 2024; DOI: https://doi.org/10.7736/JKSPE.024.053

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In this study, we developed a new vertical thermal gradient rig that uses methane-oxygen fuel. We conducted thermal gradient testing on a thermal barrier coating system, with a flame temperature of 1,900℃. Our results showed that the maximum surface temperature reached 1,065℃, while the temperature difference between the surface temperature and the temperature of the middle substrate (ΔT) was 70oC. Using the same torch as in this study, our finding suggest that the total flow rate of the flame should be above 12.4 LPM, and the gun distance should be less than 8 cm, to simulate a surface temperature of 1,300℃, while keeping the substrate temperature below 1,000℃. This will ensure that the flame is wide enough to cover the entire surface area of the thermal barrier coating.

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Thermal Fatigue Life Evaluation of EB-PVD TBC Using Newly Developed Small-scale Burner Rig
Soo Park, Dae-Jin Kim, Jun-Young Kim, Seoung-Ju Kim, Chang-Sung Seok
Journal of the Korean Society for Precision Engineering.2025; 42(1): 65. CrossRef

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Study on Correlation between Manufacturing Method of Thermal Insulation Fabric and Thermal Insulation Performance for Reducing Rail Temperature in Summer Season: Juyeop Park, Donghoon Kang; J. Korean Soc. Precis. Eng. 2024;41(4):313-319.
Published online April 1, 2024; DOI: https://doi.org/10.7736/JKSPE.023.151

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Rails are important facilities related to safe running of trains. When buckling occurs due to thermal expansion, serious safety accidents such as train derailment can occur. Currently, operating organizations are building expensive temperature monitoring systems and automatic watering devices. However, they have limitations for universalization due to their costs. Recently, long-term rail temperature reduction effect has been demonstrated by applying thermal insulation paint to rail surface. However, when coating the rail surface with paint, it increases the difficulty of detecting defects through nondestructive testing, which is one of the important elements of rail maintenance. To solve this problem, previous studies have proposed a detachable thermal insulation fabric by coating the surface of a fabric with thermal insulation paint and attaching a magnetic material. In this study, effect of thermal insulation performance according to manufacturing method was analyzed to derive the optimal performance of the previously developed thermal insulation fabric. Experiment results confirmed that paint weight increased when the roller method was used compared to the spray method with temperature reduction performance improved. Finally, the most efficient and optimal paint weight ratio was derived when the roller method was applied.

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A Study on Numerical Analysis for Determination of Glass Molding Process Conditions for Glass Lenses: Jaehun Choi, Sajan Tamang, Heesung Park; J. Korean Soc. Precis. Eng. 2024;41(3):207-214.
Published online March 1, 2024; DOI: https://doi.org/10.7736/JKSPE.023.136

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The Glass Molding Process (GMP) produces large quantities of glass optical parts and provides the advantages of high molding accuracy, short production cycle, low cost, and little pollution. Developments in different sectors, such as cameras and telescopes, are prompting studies on the design of aspherical optical components. Modeling heat transfer and deformation at high temperatures are crucial aspects of studying glass because its properties are significantly influenced by temperature-induced phase changes. In this study, temperature changes and geometric deviations of lenses were studied with respect to heating, pressing, and cooling times and the heat capacity of the heater used. A 3D model was designed for the heating, pressing, and cooling steps, and heat transfer was subjected to numerical analysis considering the specific heat of glass and the temperature dependence of thermal conductivity. Lens molding temperature conditions were then analyzed with the heat capacity of the lens molding heating system. Lens molding conditions were derived by analyzing lens temperatures with respect to heating and cooling capacities at each process step.

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Precision Glass Aspherical Lens Manufacturing by Compression Molding: A Review
Xiaohua Liu, Jian Zhou, Bo Tao, Yang Shu, Zexin Feng, Shih-Chi Chen, Yingying Zhang, Allen Y. Yi
Light: Advanced Manufacturing.2025; 6: 1. CrossRef
A Study on Temperature and Stress Distribution in a Lens under Multi-Stage Cooling Conditions in Progressive Glass Molding Processes
Ji Hyun Hong, Jeong Taek Hong, Dong Yean Jung, Young Bok Kim, Keun Park, Chang Yong Park
Journal of the Korean Society for Precision Engineering.2025; 42(2): 157. CrossRef

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Study on Controlling Material Properties of Cladded Layers Using High Temperature and Hybrid Cladding Process: Yeong Kwan Jo, Sang Hu Park; J. Korean Soc. Precis. Eng. 2023;40(10):771-779.
Published online October 1, 2023; DOI: https://doi.org/10.7736/JKSPE.023.073

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A hybrid cladding technology was developed by combining direct energy deposition (DED) and ultrasonic nanocrystal surface modification (UNSM). This is an effective process to control the mechanical properties inside the metal-clad layer, but the scope to improve the internal properties is low. Therefore, in this study, the UNSM process was applied while heating at 300 and 600℃ to increase the effectiveness of this hybrid additive process. To validate the characteristics of this method, a study on the cross-sectional properties upon application of heating was conducted. Hybrid cladding at 300 degrees produced improvements- over a 40% larger area than the results at room temperature. At 600 degrees, the hybrid cladding improved mechanical properties over a larger area by nearly 2 times. In this study, the characteristics of the roomtemperature and the high-temperature hybrid cladding process were analyzed. The proposed method shows a high improvement effect and is a promising method to improve the internal mechanical properties of the cladded layer.

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Analysis of Electromagnetic Field and Temperature Distribution around Narrow Gap in High-frequency Resistance Welding of Steel Pipe: Young Soo Yang, Kang Yul Bae; J. Korean Soc. Precis. Eng. 2023;40(10):829-837.
Published online October 1, 2023; DOI: https://doi.org/10.7736/JKSPE.023.053

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When a narrow gap was formed under appropriate welding conditions in the steel pipe manufacturing process using highfrequency resistance welding, temperature distribution was analyzed to predict the length of the gap. Assuming the length of the gap from the apex point to the welding point at an applied voltage, and calculating the temperature distribution around the gap, the length of the gap with an appropriate fusion width at the welding point could be estimated. Along with this, the current density and magnetic flux density distributions that appeared in the narrow gap were obtained according to the change in the applied voltage, and the distribution shape and size of the electromagnetic force acting on the gap were also predicted. The current density, magnetic flux density, and electromagnetic force gradually increased along the narrow gap, showing the maximum value at the welding point. In the temperature distribution in the narrow gap, the surface of the front end began to melt at an appropriate applied voltage, and the melting width was the largest at the welding point. As the applied voltage increased, the narrow gap became longer, and the appropriate gap length appeared in proportion to the applied voltage.

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Analysis of Stress Distribution around the Weld Zone in High Frequency Resistance Welding of Steel Pipe
Young-Soo Yang, Kang-Yul Bae
Journal of the Korean Society of Manufacturing Process Engineers.2024; 23(6): 21. CrossRef

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Application of Deep Reinforcement Learning to Temperature Control of a Chamber for Ultra-precision Machines: Byung-Sub Kim, Seung-Kook Ro; J. Korean Soc. Precis. Eng. 2023;40(6):467-472.
Published online June 1, 2023; DOI: https://doi.org/10.7736/JKSPE.022.124

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Deep reinforcement learning (RL) has attracted research interest in the manufacturing area in recent years, but real implemented applications are rarely found. This is because agents have to explore the given environments many times until they learn how to maximize the rewards for actions, which they provide to the environments. While training, random actions or exploration from agents may be disastrous in many real-world applications, and thus, people usually use computer generated simulation environments to train agents. In this paper, we present a RL experiment applied to temperature control of a chamber for ultra-precision machines. The RL agent was built in Python and PyTorch framework using a Deep Q-Network (DQN) algorithm and its action commands were sent to National Instruments (NI) hardware, which ran C codes with a sampling rate of 1 Hz. For communication between the agent and the NI data acquisition unit, a data pipeline was constructed from the subprocess module and Popen class. The agent was forced to learn temperature control while reducing the energy consumption through a reward function, which considers both temperature bounds and energy savings. Effectiveness of the RL approach to a multi-objective temperature control problem was demonstrated in this research.

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Condition Evaluation for Railway Running Units Using Infra-red Thermography: Seok Jin Kwon, Min Soo Kim, Jung Won Seo, Young Sam Ham; J. Korean Soc. Precis. Eng. 2023;40(6):433-439.
Published online June 1, 2023; DOI: https://doi.org/10.7736/JKSPE.022.122

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Damage to the units related to driving and running of the railway vehicle may cause an inevitable accident due to defects and malfunctions in operation. In order to prevent such an accident, a non-destructive diagnostic technology that detects the damage is required. Previous researchers have researched and developed a monitoring system of the infrared thermography method to diagnose the condition of the railway vehicle driving and driving units. A system for monitoring running of the railway vehicle and temperature condition of the drive unit at a vehicle speed of 30 to 100 km/h was constructed, and a study on its applicability was conducted. In this study, a system for diagnosing an abnormal condition of the driving and running units while the vehicle is running with an infrared thermography diagnostic system was installed in the depot and operation route, and evaluation of the abnormal condition of the driving and running units was performed. The results show that the diagnosis system using infrared thermography can be used to identify abnormal conditions in the driving and running units of a railway vehicle. The diagnosis system can effectively inspect the normal and abnormal conditions in operation of a railway vehicle.