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최영휴(Young-Hyu Choi),김수태(Soo-Tae Kim),안호상(Ho-Sang An),최학봉(Hag-Bong Choi),홍종승(Jong-Seung Hong) 한국생산제조학회 2011 한국생산제조시스템학회 학술발표대회 논문집 Vol.2011 No.4
This paper introduces manufacturing technologies for each of the 3 different kind of large scale multi-tasking machine tools; for special examples, a multi-tasking machine tool for large scale marine engine crankshaft, a multi-tasking vertical lathe for windmill parts, and a large scale 5-axis machine tool of gantry type for multi-task machining to machine highly precision large parts.
라우터머신용 랙 피니언 방식 이송시스템의 / 진동해석 및 동적설계 최적화
최영휴(Young-Hyu Choi),최응영(Eung-Young Choi),장성현(Sung-Hyun Jang),하종식(Jong-Sik Ha),조용주(Yong-Ju Cho) 대한기계학회 2005 대한기계학회 춘추학술대회 Vol.2005 No.5
In order to prevent a router machine feed drive system from transient operational vibration, this paper presents vibration analysis and dynamic design optimization of a rack and pinion typed feed drive system for a router machine. The feed drive system was mathematically idealized as a 5-degree-of-freedom lumped parameter model. Stiffness parameters of motor-shaft, rack and pinion gears, and machine structure were appropriately considered in the modeling. Computational experiment was carried out to obtain vibrations of the feed drive system during its transient speed operation. Furthermore, optimum design parameters were successfully obtained by using a Genetic Algorithm based design optimization method.
5-Head Router Machine 구조물의 진동최소화를 위한 동적설계 최적화
최영휴(Young-Hyu Choi),장성현(Sung-Hyun Jang),최응영(Eung-Young Choi),하종식(Jong-Sik Ha),조용주(Yong-Ju Cho) 대한기계학회 2005 대한기계학회 춘추학술대회 Vol.2005 No.5
This paper presents a multi-step design optimization for 5-head router machine using a genetic algorithm. The design problem is to find out the optimum configuration and thickness of structural members which minimize vibrations, the static compliance, dynamic compliance and weights of the machine structure simultaneously under several constraints such as dimensional constraints, maximum deflection limit, safety criterion and maximum vibration amplitude limit. Optimization results showed a great reduction in compliance and vibration amplitude at the spindle nose of the router machine without increase of machine weight.
경사안내면 상에서 이송되는 볼나사-슬라이드 이송계의 마찰기인 진동해석
최영휴(Young Hyu Choi) 한국기계가공학회 2014 한국기계가공학회지 Vol.13 No.6
A moving mass on a skewed linear guideway model to analyze the friction-induced stick-slip behavior of ball-screw-driven slides is proposed. To describe the friction force, a friction coefficient function is modelled as a third-order polynomial of the relative velocity between the slide mass and a guideway. A nonlinear differential equation of motion is derived and an approximate solution is obtained using a perturbation method for the amplitudes and base frequencies of both pure-slip and stick-slip oscillations. The results are presented with time responses, phase plots, and amplitude plots, which are compared adequately with those obtained by Runge Kutta 4th-order numerical integration, as long as the difference between the static and kinematic friction coefficients is small. However, errors in the results by the approximate solution increase and are not negligible if the difference between the friction coefficients exceeds approximately 40% of the static friction coefficient.
최영휴(Young-Hyu Choi),홍민기(Min-Gi Hong) 한국기계가공학회 2016 한국기계가공학회지 Vol.15 No.3
The static and dynamic structural integrity qualification was performed through the seismic analysis of a small-size Savonius-type vertical wind turbine at dead weight plus wind load and seismic loads. The ANSYS finite element program was used to develop the FEM model of the wind turbine and to accomplish static, modal, and dynamic frequency response analyses. The stress of the wind turbine structure for each wind load and dead weight was calculated and combined by taking the square root of the sum of the squares (SRSS) to obtain static stresses. Seismic response spectrum analysis was also carried out in the horizontal (X and Y) and vertical (Z) directions to determine the response stress distribution for the required response spectrum (RRS) at safe-shutdown earthquake with a 5% damping (SSE-5%) condition. The stress resulting from the seismic analysis in each of the three directions was combined with the SRSS to yield dynamic stresses. These static and dynamic stresses were summed by using the same SRSS. Finally, this total stress was compared with the allowable stress design, which was calculated based on the requirements of the KBC 2009, KS C IEC 61400-1, and KS C IEC 61400-2 codes.
최영휴(Young-Hyu Choi),김수태(Soo-Tae Kim),설상석(Sang-Seok Seol),문성춘(Sung-Choon Moon) 한국기계가공학회 2020 한국기계가공학회지 Vol.19 No.4
In this study, a response spectrum analysis of an electric distributing board (EDB) was conducted to investigate seismic integrity in the design stage. For the seismic analysis, the required response spectra of a safe shutdown earthquake with 2% damping (RRS/SSE-2%) specified in GR-63-CORE Zone 4 was used as the ground spectral acceleration input. A finite element method modal analysis of the EDB was also performed to examine the occurrence of resonance within the frequency range of the earthquake response spectrum. Furthermore, static stress caused by deadweight was analyzed. The resultant total maximum stress of the EDB structure was calculated by adding the maximum stresses from both seismic and static loads using the square root of the sum of the squares (SRSS) method. Finally, the structural safety of the EDB was investigated by comparing the resultant total maximum stress with the allowable stress.
랜덤가진시험을 이용한 대형 크랭크샤프트 가공용 복합다기능 선반의 강성 평가
최영휴(Young Hyu Choi),하경보(Gyung Bo Ha),안호상(Ho Sang An) Korean Society for Precision Engineering 2014 한국정밀공학회지 Vol.31 No.7
Machine tool vibration is well known for reducing machining accuracy. Because vibration response of a linear structure generally depends on its transfer function if the magnitude of excitation were kept constant, this study introduces a RET(Random Excitation Test) based on FRF method to evaluate stiffness of a prototype HDMTL(Heavy-Duty Multi-Tasking Lathe) for large crankshaft of marine engine. Firstly, two force loops of the lathe and corresponding structural loops were identified:1) workpiece - spindle - head stock - main bed, 2) workpiece - tool post - carriage bed. Secondly, compliances of each structural loop were measured respectively using RET with a hydraulic exciter and then converted into stiffness. Finally, the measured stiffness was compared with that obtained previously by FEM analysis. As the result, both measured and computed stiffness were closely in agreement with each other. And the prototype HDMTL has evidently sufficient rigidity above ordinary heavy-duty lathes.