• 한국운동역학회지
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• 제16권4호
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• pp.13-20
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• 2006

A platform diving with categorizing 624C motion was video taped and 3D kinematic variables were analyzed. This motion is consist of 3 parts from the headstand position to the act of turning after take-off. The results indicated that it took a very short time from the moment of take-off to the act of 1/2 turning because the turning motion has already started from preparing motion even before the fingertips have parted from the ground. Also, there was barely any jumping height due to the use of upper limbs segment and there was little difference in the moving distance compared to the standing events judging from horizontal movement of 1.1m. The horizontal velocity of the center of human body was increased before take-off while the vertical velocity was decreased right after take-off and the velocity of lower limbs segment was faster than the upper limbs segment showing contrary results to the standing events. In the aspects of angular velocity, the upper limbs segment starts the turning motion when take-off by rapidly extending its angular velocity while lower limbs segment make large angular velocity even before take-off.

• 한국결정성장학회지
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• 제24권6호
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• pp.274-278
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• 2014

가공정밀도 요구특성의 지속적인 향상에도 불구하고, 공작기계와 절삭공구를 이용한 절삭가공공정에서의 채터진동은 아직도 개선의 여지가 많이 남아있다. 특히, 더욱 고속화, 고정밀화 되고 있는 가공현장에서 채터진동의 효과적인 감소대책에 대한 다양한 연구가 필요하다. 본 연구에서는 이러한 문제점을 해결하기 위해 고정밀 공구동력계를 이용한 실시간 절삭력 측정과 유한요소해석 방법을 이용해 사용 빈도와 활용이 매우 큰 터닝센터(turning center)에서 폭넓게 적용되고 있는 3종의 절삭공구 툴링에서의 채터진동 특성을 평가하여, 공구형상 및 툴링 특성에 따른 채터진동과의 상관성을 연구하고, 향후 채터진동 저감형 공구개발을 위한 근간 기술자료로 활용코자 한다.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2001년도 춘계학술대회 논문집
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• pp.938-941
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• 2001

A tool holder system has been designed and builted to measure cutting forces in diamond turning. This system design includes a 3-component piezo-electric tranducer. Initial experiments with tool holder system included verification of its predicted dynamic characteristics as well as a detailed study of cutting parameters. In this research, tool holder system is modeled by considering the element dividing, material properties, and boundary conditions using MSC/PATRAN. Mode and frequency analysis of structure is simulated by MSC/NASTRAN, for the purpose of developing the effective design. In addition, tool holder system is verified by vibration test using accelerometer. Many cutting experiments have been conducted on 6061-T6 aluminum. Tests have involved investigation of velocity effects, and the effects of depth and feedrate on tool force. Cutting velocity has been determined to have negligible effects between 4 and 21㎧.(6) Forces generally increase with increasing depth of cut. Increasing feedrate does not necessarily lead to higher forces. Results suggest that a sample model may not be sufficient to describe the forces produced in the diamond turning process.

• 한국정밀공학회지
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• 제26권1호
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• pp.138-145
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• 2009

High-efficiency and high-quality machining has become a fact of life for numerous machine shops in recent years. And high-efficiency machining is the most significant tool to enhance productivity. In this study, to achieve high-efficiency machining in turning process, a spindle speed optimization method was proposed based on a cutting power model. The cutting force and power were estimated from the cutting parameters such as specific cutting force, feed, depth of cut, and spindle speed. The time delay due to the acceleration or deceleration of spindle was considered to predict a more accurate machining time. Especially, the good agreement between the predicted and measured cutting forces showed the reliability of the proposed optimization method, and the effectiveness of the proposed optimization method was demonstrated through the simulation results associated with the productivity enhancement in turning process

• 한국정밀공학회지
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• 제31권9호
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• pp.799-804
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• 2014

Hard turning is a machining process for hardened materials with high surface quality so that grinding process can be eliminated. Therefore, the hard turning is capable of reducing machining time and improving productivity. In this study, hardened AISI4140 (high-carbon chromium steel) that has excellent yield strength, toughness and wear resistance was finish turned using CBN tools. Wear characteristics of CBN tool was analyzed in dry and MQL mixed with nano-particle (Nano-MQL). The dominant fracture mechanism of CBN tool is diffusion and dissolution wear on the rake surface resulting in thinner cutting edge. Abrasive wear by hard inclusion in AISI4140 was dominant on the flank surface. Nano-MQL reduced tool wear comparing with the dry machining but chip evacuation should be considered. A cryogenically treated tool showed promising result in tool wear.

• 한국공작기계학회논문집
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• 제15권4호
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• pp.83-91
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• 2006

At present, industry and researchers are looking for ways to reduce the use of lubricants because of ecological and economical reasons. Therefore, metal cutting is to move toward dry cutting or semi-dry cutting. One of the technologies is known as MQL(Minimum Quantity Lubrication) machining. This research presents an investigation into MQL machining with the objective of deriving the optimum cutting conditions for the turning process of SM4SC. To reach these goals several finish turning experiments were carried out, varying cutting speed, feed rate, oil quantity and so on, with MQL and flood coolant. The surface roughness and cutting force results of tests were measured and the effects of cutting conditions were analyzed by the method of Analysis of Variance(ANOVA). From the experimental results and ANOVA, this research proposed optimal cutting conditions to improve the machinability in MQL turning process.

• 대한기계학회논문집
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• 제17권1호
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• pp.38-45
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• 1993

본 연구에서는 선반작업에서의 피삭체의 형상을 특징형상(feature)단위로 정 의하였고, 이 특징형상을 이용하여 형상정의를 수행한 후 가공순서 및 가공조건을 대 화형식으로 입력하면 공구위치 데이터(CL data)를 자동으로 산출하고 이를 기계제어데 이터(MC data)로 변화시켜 주는 NC선반가공 프로그래밍시스템 FeaTURN (Feature-based TURNing system)을 개발하였다.

• 한국기계가공학회지
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• 제12권1호
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• pp.63-69
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• 2013

Many researchers are trying to reduce the use of lubrication fluids in metal cutting to obtain safety, environmental and economical benefits. The aim of this study is to determine the optimization lubrication conditions in minimum quantity lubrication(MQL) turning of workpieces with taper angle. This study has been considered about various conditions of MQL. The objective functions are cutting force and surface roughness. Design factors are nozzle diameter, nozzle angle, MQL supply pressure, distance between tool and nozzle and length of supply line. The cutting force and surface roughness were statistically analyzed by the use of the Box-Behnken method. As a results, optimum lubrication conditions were suggested and verification experiment has been performed. The results of this study are expected to help the selection of lubrication conditions in MQL turning.

• 수산해양기술연구
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• 제51권2호
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• pp.245-256
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• 2015

This study is intended to provide navigator with specific information necessary to assist the avoidance of collision and the operation of ships to evaluate the maneuverability of dead weight tonnage 8,000 tons Oil/Chemical tanker. The actual maneuvering characteristics of ship can be adequately judged from the results of typical ship trials. Author carried out sea trials based full scale for turning test in ballast condition and full load condition, semi balanced rudder and flap rudder. The turning circle maneuvering were performed on the starboard and port sides with $35^{\circ}$ rudder angle at the normal continuous rating. The results from tests could be compared directly with the standards of maneuverability of IMO and consequently the maneuvering qualities of the ship is full satisfied with its.

• 한국측량학회:학술대회논문집
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• 한국측량학회 2009년도 춘계학술발표회 논문집
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• pp.15-17
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• 2009

본 연구에서는 건설 CAD 도면을 수치지도 갱신을 위한 공간데이터로 변환하는데 있어서 선회함수를 활용하여 선형 데이터를 단순화시키는 기법에 대한 연구를 수행하였다. 이 기법은 선형의 형상을 수치적으로 표현하는데 유용한 선회함수 기법을 기반으로 절점 사이의 거리와 각을 정량적으로 평가하여 효율적으로 절점을 제거하는 선형 단순화 기법이다. 적용결과, 높은 형상 보존 효과와 절점 감소율을 보였으며 수치지도 작성내규에 대해 100%의 만족율을 보여 건설도면을 활용하여 수치지도 갱신을 위한 단순화 기법으로 유용하게 사용될 가능성이 높을 것으로 판단된다.