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"Jung Ho Lee"

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"Jung Ho Lee"

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A Damping Compensation Method for Suppressing Vibration in a Transient State in a Turret Servo System of a Machine Tools with Low Inertia
Nae Soo Cho, Tae Ho Oh, Woo Hyen Kwon, Jung Ho Lee, Chul Yun
J. Korean Soc. Precis. Eng. 2023;40(6):425-431.
Published online June 1, 2023
DOI: https://doi.org/10.7736/JKSPE.023.012
In general, rotor inertia has an inversely proportional relationship with proportional gain and bandwidth in a turret speed control system of machine tools; thus, this system has a disadvantage, such as weak disturbance caused by a decrease in the damping ratio and an increase in bandwidth due to low rotor inertia. This paper proposes a damping compensator that is resistance to disturbances in order to improve the above problems. The proposed damping compensator reduces the residual vibration induced in the transient state by using a digital high-pass filter. The experimental results showed that the overshoot was reduced by about 5.5% in the speed response and by about 20% in the torque response in the no-load condition. Under the load condition of 4.8 N.m, the torque response showed that the undershoot was reduced by about 26%.
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A Comparative Study on Fracture Property of Aluminum Foam DCB and TDCB Specimens for Type of Mode III on Thickness
Jung Ho Lee, Sung Ki Lyu, Jae Ung Cho
J. Korean Soc. Precis. Eng. 2019;36(3):263-269.
Published online March 1, 2019
DOI: https://doi.org/10.7736/KSPE.2019.36.3.263
This study focuses on these issues and includes the static fracture experiments with two forms of specimens; aluminum foam DCB and TDCB bonded with the type of mode III, a simulation static analysis to verify this experiment, and analysis of fracture behavior of adhesive interface of structures attached with aluminum foam by shape and thickness. The thickness of DCB and TDCB specimens designed in this study are set as variable t, and each thickness is t = 35 mm, 45 mm, 55 mm. According to forced displacements, the maximum reaction forces of DCB specimens due to thickness were approximately 0.35 kN, 0.45 kN, 0.54 kN, and the maximum reaction force of TDCB were approximately 0.4 kN, 0.52 kN, and 0.63 kN respectively. We expect the data according to variables to be easily investigated without a separate testing process, and effective analysis of the mechanical characteristics of aluminum foam DCB and TDCB.
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