Journal of the Korean Society for Precision Engineering

Tensile Behavior of 3D Printed Specimens by Small Punch Test: Bum Joon Kim; J. Korean Soc. Precis. Eng. 2025;42(10):879-884.
Published online October 1, 2025; DOI: https://doi.org/10.7736/JKSPE.025.121

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The purpose of this study is to evaluate the deformation behavior of 3D printed specimens using the small punch tensile test method. Traditional tensile tests for assessing mechanical properties require a significant amount of material to produce uniaxial tensile specimens. In contrast, the small punch test method only requires 10 x 10 x 0.5 mm (width x length x thickness) thin plate specimens, providing a substantial economic advantage in specimen sampling and production. This method is particularly beneficial when it is impossible to produce specimens of the same size as uniaxial specimens, as it allows tensile testing with just the minimum sample required. In this study, we utilized fused deposition modeling 3D printing and considered various 3D printing parameters, such as layer height and volume fraction, while manufacturing the specimens. We then compared and analyzed the effects of these variables on tensile strength as measured by the small punch tensile test. Furthermore, we focused on investigating the applicability of this method to the deformation behavior of 3D printed specimens. We also examined the impact of laminating conditions, including layer height, printing speed, and laminating direction, on the failure modes observed after the small punch tensile test.

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Aerodynamic Flow Characteristics Inducing Centrifugal Compressor Noise Generation in High-speed Turbomachinery: Jihun Song, Chang Ho Son, Dong-Ryul Lee; J. Korean Soc. Precis. Eng. 2025;42(9):763-770.
Published online September 1, 2025; DOI: https://doi.org/10.7736/JKSPE.025.088

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Centrifugal compressor is a device that converts kinetic energy to increase the air pressure. It rotates at a high speed of up to 200,000 RPM and directly affects aerodynamic noise. Various studies have already been conducted, but the direct calculation method of acoustics based on the unsteady solution is inefficient because it requires a lot of resources and time. Therefore, flow characteristics and numerical comparison according to various aerodynamic factors predicted as a cause of noise generation were analyzed in this study based on the steady solution. High-frequency noise was calculated locally near the asymmetric flow properties. Vortex and turbulent kinetic energy were generated at similar locations. Among static components, a large-sized vortex of 3.48×10⁷ s^-1 was distributed at the location where the rotational flow around the compressor wheel combined with the inlet suction flow. In addition, a locally high vortex of 8.16×10⁵ s^-1 was distributed around the balancing cutting configurations that cause asymmetric flow characteristics. Analysis of these factors and causes that directly affect noise can be efficiently improved in the pre-design stage. Therefore, the efficient design methodology for centrifugal compressors that considers both performance and noise is expected based on the results of this study.

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Phasic and Tonic Coordination among Upper-limb Muscles in Different Speeds of Reaching Movement: Min-Jae Kim, Ju-Hee Kim, Hyeon-Soo Shin, Sean-Min Lee, Na-Yeon Kim, Gwang-Moon Eom; J. Korean Soc. Precis. Eng. 2025;42(2):105-120.
Published online February 1, 2025; DOI: https://doi.org/10.7736/JKSPE.024.112

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In the rehabilitation of upper limb function impaired by stroke, facilitating the coordinated activation of multiple muscles is desirable. This study aims to analyze the coordination patterns of the tonic and phasic components of EMG during a reaching task and to investigate how the phasic component changes in relation to reaching speed. The analysis focused on the shoulder and elbow joints. EMG was recorded at five different speeds, with the slowest speed selected to represent the tonic component. The tonic component was then removed from the total EMG at the other four speeds to extract the phasic component. Correlation coefficients were calculated between the tonic component and joint angles, as well as between the phasic component and joint angular accelerations. For the tonic component, as joint angle increased during reaching, muscle activation also increased to counteract gravitational moments and enhance joint stiffness. For the phasic component, as reaching speed increased, the correlation between acceleration-deceleration patterns and muscle activation also increased. This suggests a greater synergistic contraction for enhanced acceleration and deceleration, as well as increased antagonistic contraction to ensure dynamic stability during faster movements

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A Study on the Characteristics of the Retainer applied to Taped Roller Bearings under High Speed Operating Condition: Kang Seok Kim, Kyoung Ku Lee, Deug Woo Lee; J. Korean Soc. Precis. Eng. 2023;40(7):563-570.
Published online July 1, 2023; DOI: https://doi.org/10.7736/JKSPE.023.007

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Factors such as weight reduction and improved fuel efficiency of vehicles interfere with the efficiency of roller bearings in automobiles under harsh conditions. In particular, studies are ongoing to increase the load capacity and rigidity under highspeed conditions. The development of tapered roller bearings that can be used under high-speed conditions is accelerating. In the case of high-speed bearings, factors such as centrifugal force, gyroscopic moment, and slippage have a greater influence on the performance of the bearing, unlike the traditional operating mechanisms. The resulting lubrication characteristics have a profound impact on the failure mode of the bearing. In particular, unlike traditional roller bearings, system failure due to damage to the retainer frequently occurs, suggesting the need for prompt investigation. In this study, the rotational characteristics and strength of three models, a steel cage and two plastic cages for tapered roller bearings with the same internal structure, were examined. A comparative analysis of retainers with different shapes and materials can reveal the factors contributing to optimal performance under high-speed operating conditions and the optimal design of bearings.

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A Study on the Influence of Dominant Parameters Related to Brake Squeal in the Brake System with the Flexible Pad: Eunseok Lee, Kwanju Kim, Namsik Yoo, Beomjoo Lee, Sunjoo Na, Jongtae Na; J. Korean Soc. Precis. Eng. 2022;39(5):345-355.
Published online May 1, 2022; DOI: https://doi.org/10.7736/JKSPE.022.003

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The brake squeal noise is a high-frequency noise over 1 kHz range generated by the contact between the brake pad and the disk. The purpose of this paper was to investigate the behavior of the squeal noise characteristics of the brake system from an instability point of view, according to the variation of major parameters such as friction coefficient between the flexible pad and the disk, brake pressure, and Young’s modulus of disk. Full nonlinear perturbed modal analysis using commercial finite element analysis program was performed to derive complex eigenvalue results of the model. And the sensitivity behavior was observed. Increasing the coefficient of friction or Young’s modulus of disk tended to make the squeal mode of the model more unstable. However, the change in brake pressure has a complicated nonlinear relationship with the squeal mode of the model. The judgment technique conducted in this study should be considered to be used in the design of the vibration point of the disk and pad of railway vehicles in the future.

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A Study on Crystallization of Perovskite Using a High-Speed Meniscus Solution Shearing Coating Visualization Device: I-Ji Kim, Hyun Ah Lee, Dong Soo Kim; J. Korean Soc. Precis. Eng. 2021;38(12):965-972.
Published online December 1, 2021; DOI: https://doi.org/10.7736/JKSPE.021.017

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Among the types of new and renewable energy, perovskite solar cells, which are next-generation solar cells, are capable of a solution process at a low temperature of 200oC or less, and have the advantages of high efficiency and low cost; hence, many studies have been conducted. Research has been performed on perovskite solar cells mainly produced using spin coating, but they have a disadvantage of occurrence of pinholes and cracks when fabricated over a large area, reducing the uniformity and density of the thin film. For the production of large-area perovskite solar cells, research is underway using solution shearing process technology among printed electronic process technologies, and most of the processes have been carried out at low speeds. This is due to the size of the crystal, which is one of the most important factors of high efficiency of the solar cell. When printing at high speed for mass production, the size of the crystal is reduced, resulting in charge loss and lower efficiency, making it difficult to apply the roll-to-roll process. In this study, to apply the roll-to-roll process for mass production, perovskite crystallization experiments were performed under high-speed conditions and crystal size changes according to meniscus stability.

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A Study on Aero-Acoustics of High-Speed Turbomachinery for Different Rotational Speeds: Ji-Hun Song, Dong-Ryul Lee; J. Korean Soc. Precis. Eng. 2020;37(12):897-904.
Published online December 1, 2020; DOI: https://doi.org/10.7736/JKSPE.020.072

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This study is to numerically investigate the Aero-Acoustics of Turbocharger compressor. The turbocharger compressor is high-speed turbomachinery that rotates faster than 200,000 RPM. The Aero-Acoustics with five different rotational speeds (120,000, 150,000, 180,000, 200,000, and 220,000 RPM) is used herein. The fluid domain is designed by CATIA V5R21 and analyzed by ANSYS FLUENT V19.1 with compressible momentum equation. The Pressure-velocity coupling method of the solver is the coupled algorithm and calculated by a pressure-based method. Numerical analysis of the aero-acoustics by broadband noise sources model provides calculated sound-source and acoustic-level based on steady RANS. At the industrial site, it is important to quickly analyze the noise source. APL (Acoustic Power Level) with five different rotational speeds and sound characteristics based on flow factor at the compressor wheel was numerically calculated for the noise-based design. The maximum APL is located at blade tips in case of 120,000, 150,000 and 180,000 RPM. In the case of 200,000 RPM, the maximum APL is located at splitter tips. At more than 220,000 RPM, the maximum APL is located at the balancing cutting section of the wheel. In order to optimally design the high-speed turbomachinery, cutting sections and side locations of the wheel are essential factors to reduce physical noise.

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A Review on Flow Regimes and Aeroacoustic Coupling in Subsonic Flow Around Flat Plates
Atef El Khatib, Ahmad Al Miaari, Hassan Assoum, Ahmad Salem, Ali Hammoud
Arabian Journal for Science and Engineering.2025; 50(12): 8753. CrossRef
Aerodynamic Flow Characteristics Inducing Centrifugal Compressor Noise Generation in High-speed Turbomachinery
Jihun Song, Chang Ho Son, Dong-Ryul Lee
Journal of the Korean Society for Precision Engineering.2025; 42(9): 763. CrossRef

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Analysis of Effect of Stirring Process Conditions on Liquid Viscosity in an Overhead Stirrer: Ho Cheol Lee, Gi Dae Kim; J. Korean Soc. Precis. Eng. 2020;37(9):659-665.
Published online September 1, 2020; DOI: https://doi.org/10.7736/JKSPE.020.033

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To monitor the stirring state by on-line estimation of liquid viscosity instead of stopping the stirring process and measuring the viscosity using viscometer, a basic study clarifying the effect of stirring conditions was carried out. For this purpose, the relationship between liquid viscosity and the stirring conditions, such as stirring torque, stirring speed, the duty ratio of PWM, impeller and beaker type, and the blade position in the beaker was analyzed. The second-order relationship between the stirring speed and torque, the linear relationship between viscosity and torque, and the linear relationship between duty ratio of PWM and stirring speed were observed, thereby indicating that the liquid viscosity could be estimated by an experimental formula based on the duty ratio and the stirring speed. In addition, the type of impeller and beaker was identified using the magnetic field inside impeller and RFID technology. For reducing the error in calculating the liquid viscosity, the employment of an impeller blade with a large rotational resistance and stirring with the blade at the center zone of the beaker were found to be necessary.

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A Study on Contactless Identification of Impellers Using a Digital Hall Sensor
Ho-Cheol Lee
Journal of the Korean Society of Manufacturing Process Engineers.2021; 20(12): 71. CrossRef

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Effect of Fused Deposition Conditions on the Fracture Behavior of 3D Printed Tensile Specimens: Bum Joon Kim; J. Korean Soc. Precis. Eng. 2020;37(6):421-428.
Published online June 1, 2020; DOI: https://doi.org/10.7736/JKSPE.020.048

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Three-dimensional printing technology has technical limitations limited to the development of prototypes focusing on functional realization. Because of these limitations, there are problems such as mechanical strength and rigidity in entering the commercialization market. However, the industry is working to overcome these obstacles in the future and apply them directly to the field for mass production in the manufacturing process. In particular, research to secure physical properties such as mechanical strength, the major problem of 3D printing products, has been initiated in the automobile industry, aviation, and medical fields. Thus, this study focused on the mechanical strength required for commercialization of 3D printing technology. To achieve this goal, a tensile specimen was fabricated by an FDM (Fused Deposition Modeling) type 3D printer. Tensile specimens were produced of round bar type and the deposition direction, layer height, and printing speed of the layers were considered. Finally, the effects of variables for each printing condition on tensile strength and fracture behavior were compared and analyzed. Also, the fracture surface of the tensile specimen was observed to investigate the effect of the deposition direction on the fracture behavior.

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Enhanced Analysis Model to account for Equivalent Anisotropic Properties of Parts according to 3D Printing Conditions
Chae-Rim Seon, Da-Yeong Jang, Geung Hyeon Lee, Minho Yoon, Jang-woo Han
Journal of the Computational Structural Engineering Institute of Korea.2025; 38(2): 131. CrossRef
Tensile Behavior of 3D Printed Specimens by Small Punch Test
Bum Joon Kim
Journal of the Korean Society for Precision Engineering.2025; 42(10): 879. CrossRef
Experimental Validation of Topology Design Optimization Considering Lamination Direction of Three-dimensional Printing
Hee-Man Park, Gyu-Bin Lee, Jin-san Kim, Chae-Rim Seon, Minho Yoon
Journal of the Computational Structural Engineering Institute of Korea.2022; 35(3): 191. CrossRef

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Improvement of Punch Life and Contact Stamping Quality in Ultra-High Speed Press: Ju-Hwan Kim, Hyun-Pyo Shin; J. Korean Soc. Precis. Eng. 2019;36(10):961-967.
Published online October 1, 2019; DOI: https://doi.org/10.7736/KSPE.2019.36.10.961

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In recent years, the manufacture connector terminals of electronic devices require an accuracy of several microns and high productivity, thus the need to develop the ultra-high speed press technology. However, increased impulse and vibration of ultra-high speed press have reduced durability of stamping die and induced serious tool wear. To solve this problem, we investigate the changes of vibrations occurring in the die and press machine under ultra-high speed working condition by using a piezoelectric sensor. Moreover, by analyzing the design parameters such as stroke, stripper movement, and collision velocity of the die, impulse and vibration were decreased, thus improving the punch life by 50% under 2,000 SPM (stroke per minute) condition

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A Study on the Design of Rotor for 10 kWh Flywheel Energy Storage System: Beom Soo Kang, Deuk Kyu Lee; J. Korean Soc. Precis. Eng. 2019;36(2):199-208.
Published online February 1, 2019; DOI: https://doi.org/10.7736/KSPE.2019.36.2.199

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The importance of environmentally-friendly energy production has been growing globally, and studies on energy storage technologies are underway, to supply produced energy to consumers. Flywheel Energy Storage System (FESS) is physical energy storage technology, that stores generated electric energy into kinetic energy in the rotor. To design the FESS with a high-strength steel rotor, that is inexpensive, recyclable and easy to manufacture, mechanical and electrical components such as a rotor, bearings, etc. are required. Among these, safety of rotor and bearings is critical, because the rotor with high rotating speed may cause axis failure or fracture of the rotating body. Proper size of a rotor for required energy storage and radial, axial forces generated by the spinning rotor was calculated, considering gyroscopic forces acting on the rotating body. Based on the calculation, adequately sustainable angular ball bearings were selected. As a result, by conducting structural, modal and critical speed analysis, safety verification is presented pursuant to the American Petroleum Institute (API) publication 684.

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An Analytical Study on the Design of Housing Components for 10 kWh Flywheel Energy Storage System
Deuk Kyu Lee, Beom Soo Kang
Journal of the Korean Society for Precision Engineering.2020; 37(1): 59. CrossRef

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Design of a Voice Coil Motor for Active Vibration Isolator of CFRP High Speed Inspection System: Hyo-Young Kim, Hyun-Ho Lee, Seok-Woo Lee, Tae-Gon Kim, Kihyun Kim; J. Korean Soc. Precis. Eng. 2019;36(1):29-35.
Published online January 1, 2019; DOI: https://doi.org/10.7736/KSPE.2019.36.1.29

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The demand for inspection of high-speed systems for machined Carbon Fiber Reinforced Plastics parts for automobileindustry and aviation industry is constantly rising. One of the factors that degrade the performance of an inspection system is micro-vibration from the ground or structure where is placed. Various isolation systems that suppress the vibration have been studied classified as either passive or active system. The passive system is composed of a spring and a damper while the active system suppresses the vibration through an electronic control system using sensors and actuators. In this study, a voice coil motor (force constant 55N/A) acting as the actuator is optimally designed using permeance method and sequential quadratic programming algorithm to suppress the vibration and reaction force by a specimen moving stage. The two optimized voice coil motors are attached to a pneumatic mount that has an advantage in design based on the force and size constraints required by the user for an active vibration isolator with velocity sensors (GS-11d). The active vibration isolation system with the four active vibration isolators -23 dB and -20 dB at resonance frequencies in horizontal and vertical transmissibility performs better than a passive vibration isolation system.

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An Active Geophone Sensor with Optimized State Variable Filter for Measuring Low-Band Frequencies
Jinsoo Choi, Hongki Yoo, Eunjong Choi, Kihyun Kim, Hyo-Young Kim
International Journal of Precision Engineering and Manufacturing.2024; 25(5): 981. CrossRef
Effect of inertia variations for active vibration isolation systems
Jinsoo Choi, Kihyun Kim, Hyoyoung Kim, SeokWoo Lee
Precision Engineering.2020; 66: 507. CrossRef

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Shaping of Micro Scale Features on Metallic Surfaces through the High-Speed Impact of Laser Accelerated Flyers: Dae Cheol Choi, Hong Seok Kim; J. Korean Soc. Precis. Eng. 2018;35(7):729-734.
Published online July 1, 2018; DOI: https://doi.org/10.7736/KSPE.2018.35.7.729

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Generally speaking, the high speed forming process is suitable for the precise manufacturing of hard-to-form and high strength materials. This study conducted microscale embossing and punching experiments by establishing a forming system that uses a laser induced acceleration. The changes in the flyer velocity with the laser energy, flyer thickness, and flyer diameter were measured using a high speed camera, and the effects of the noted acceleration characteristics of flyers on processing performance were investigated. It is particularly important that in the case of punching, the advantages of high speed processing, in which the accuracy was improved by increasing the shear zone of the workpiece, were identified. Significantly in the case of embossing, it was observed that the formability improved by increasing the flyer velocity as the flyer diameter decreased. However, in the case when the flyer thickness was decreased, increased energy was consumed in the plastic deformation of the flyer, and the advantages of high speed forming could not be realized. For this reason, further research is needed to take advantage and optimize the forming process using the laser induced acceleration through experiments which are noted as considering the various process variables and materials.

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Performance evaluation of laser shock micro-patterning process on aluminum surface with various process parameters and loading schemes
Dae Cheol Choi, Hong Seok Kim
Optics and Lasers in Engineering.2020; 124: 105799. CrossRef

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Adaptive Model Free Speed Control Algorithm of DC Motors Based on Recursive Least-Squares with Forgetting Factor: Kwang Seok Oh, Ja Ho Seo; J. Korean Soc. Precis. Eng. 2018;35(3):311-318.
Published online March 1, 2018; DOI: https://doi.org/10.7736/KSPE.2018.35.3.311

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This paper describes an adaptive model free speed control algorithm for DC motors, based on a recursive least-squares with forgetting factor. In order to control the speed of a DC motor, only the factors of output speed and voltage values have been used without a mathematical model of the DC motor. As the relationship between the input voltage and the DC motor speed in a specific region can be approximated as a first order system, the coefficient that represents the approximated first order system has been estimated by using a recursive least-squares approach with a forgetting factor model. Also, the error between the actual system and the approximated first order system has been estimated by a disturbance observer. Based on the estimated coefficient of the first order system, as well as this disturbance, an optimal input for tracking the desired velocity has been computed by using the Lyapunov direct method. Weighting factor adaptation rules have been proposed to enhance control performance. This performance evaluation has been conducted in a MATLAB/Simulink environment using a DC motor dynamic model for realistic evaluation. The evaluation results show that the developed adaptive DC motor speed control method ensures good tracking performance by using only the input voltage and the output speed information.

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A Study on the Accelerated Life Test of Axle Bearing for Railway Vehicles Using Rotational Speed-Temperature Variation Curve: Jae Won Lee, Young Sam Ham, Chang Sung Seok; J. Korean Soc. Precis. Eng. 2017;34(12):867-872.
Published online December 1, 2017; DOI: https://doi.org/10.7736/KSPE.2017.34.12.867

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Domestic railway-maintenance technologies have been developed over more than 100 years of railway operation. Based on these technologies, we are striving to localize the vehicular parts, while the component localization is currently from 90-95%. Foreign manufacturers’ products, however, are still used in the manufacturing of major core components. Bearings are one of the key components in the support of the rotating shaft, and they are the essential components of major railway parts, like axles, electric motors, and gears, as they ensure the running stability of railway vehicles at high speeds. Among them, the axle bearings need to be protected against damage not only due to the possibility of a failure, but also to avoid railway accidents, so a high reliability and stability are required. Therefore, the durability test of axle bearings is both costly and time-consuming. In South Korea, the development of axle bearings has not occurred, but several test benches for a bearing-durability test have recently been developed. The characteristic curve was created using the temperature change according to the rotational speed of the bearing, and the acceleration index was obtained from this characteristic curve.

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An Experimental Study of the Lifetime of a Tripod Shaft with Torsional Fatigue Using an Accelerated Life Test Method
Joo-Hong Lee, Hae-Yong Cho
International Journal of Precision Engineering and Manufacturing.2018; 19(9): 1399. CrossRef
A Review of Recent Advances in Design Optimization of Gearbox
Zhen Qin, Yu-Ting Wu, Sung-Ki Lyu
International Journal of Precision Engineering and Manufacturing.2018; 19(11): 1753. CrossRef