실험계획법에 의한 초음파가 부가된 자기연마가공의 특성평가

진동현(Dong-Hyun Jin),곽재섭(Jae-Seob Kwak) 대한기계학회 2015 大韓機械學會論文集A Vol.39 No.9

본 논문에서는 고경도의 재료를 효과적으로 가공하기 위하여 초음파-자기연마 복합가공을 제시하고, 초음파-자기연마 복합가공의 효율성을 검증하기 위해. 실험계획법을 적용하여 각 인자의 영향력을 평가하였다. 그 결과, 기존의 자기연마가공보다 초음파-자기연마가공의 가공효율이 더 높게 나타났으며, 초음파-자기연마 복합가공에서 가장 적절한 주파수는 28kHz 인 것으로 나타났다. 또 표면거칠기에 대한 인자의 영향을 평가하였을 때, 초음파의 진폭이 가장 큰 영향을 미치는 것을 확인하였다. 그러나 55μm의 진폭이 적용되었을 때, 자속밀도의 변화에도 불구하고 가공효율이 오히려 떨어지는 것으로 나타났다. 이러한 결과로부터 지나치게 큰 초음파 진폭은 오히려 자기연마가공의 효과를 저하시키는 것임을 알 수 있었다. In this paper, we propose an ultrasonic magnetic abrasive polishing (US-MAP) technique to effectively machine a high-strength material, and we prove the efficiency of hybrid finishing. We use Taguchi`s experimental method to determine the influence of each parameter. Based on the results, US-MAP exhibited a higher polishing efficiency than traditional MAP, and a suitable frequency for hybrid finishing was 28 kHz. When investigating the effect of the parameters on the surface roughness, the ultrasonic amplitude had the greatest effect. However, when machining with 55-Dm amplitude, the machining efficiency decreased as the magnetic flux density varied.

다구찌 방법을 이용한 초음파 가공의 최적가공조건에 관한 연구

유군위(Jun Wei Liu),김건(Jian Jin),고태조(Tae Jo Ko),백대균(Dae Kyun Baek) 대한기계학회 2013 大韓機械學會論文集A Vol.37 No.2

초음파 가공(Ultrasonic Machining:USM)은 새로운 기계가공기술 분야 중의 하나이다. 초음파 가공 과정은 비열, 비화학, 그리고 비전도의 방법이기 때문에 공작물 재료의 물리적, 화학적 변화가 없다. 이러한 특성으로 인해 초음파 가공기술은 유리, 세라믹 등과 같은 취성재료의 가공에 적합하다. 그러나 단점으로는 초음파 진동을 이용하여 취성재료를 가공하는 경우 크랙이 빈번하게 발생한다. 본 논문에서는 유리와 세라믹의 미세 구멍가공에서 다구찌 방법을 이용하여 크랙발생을 최소화하는 최적의 가공조건을 얻고자 하였다. 이를 통해 공작물의 입구 및 출구에서 발생하는 크랙 현상을 감소시켰다. Ultrasonic machining (USM) is a new method used in metal cutting. This process does not involve heating or any electrochemical effects, causes low surface damage, has small residual stress, and does not rely on the conductivity of the workpiece. These characteristics are suitable for the machining of brittle materials such as glass or ceramics. However, the use of USM for brittle materials generates cracks on the workpiece. Therefore, in this study, Taguchi’s method was used to optimize the processing conditions of micro holes drilled in glass and ceramics. This method was used to successfully reduce the number of cracks at the entrance and the exit of the micro holes.

ECAP 가공한 알루미늄합금의 결정립 미세화에 대한 비파괴평가

안석환,남기우,김진환,강석봉 한국비파괴검사학회 2002 한국비파괴검사학회지 Vol.22 No.2

최근 구속전단가공(Equal-Channel Angular Pressing)이라는 가공법을 이용하여 결정립을 미세화시키는 유효한 수단이 널리 이용되어지고 있다. 이러한 구속전단가공법을 이용해서 알루미늄합금의 결정립을 submicrometer 수준으로 미세화가 가능하게 되었다. 본 연구에서는 인장시험, 경도시험, 미세조직 관찰, 초음파탐상 및 음향방출 시험을 통해 알루미늄합금의 결정립 미세화 정도를 평가하였다. ECAP 가공 후 결정립 미세화에 의하여 강도 및 경도가 확실히 증가하였다. 초음파 탐상으로부터 초음파 음속은 ECAP가공 후의 음속이 빠르게 나타났으며, 시간-주파수 분석에서는 ECAP 가공 전의 시험편이 고주파수의 감쇠가 컸다. 그리고 ECAP가고 후의 시험편에서 음향방출의 높은 중심주파수 대역이 나타났다. 본 논문은 비파괴적인 기법을 사용하여 결정립 미세화를 판단하는데 기초적인 자료로서의 활용이 기대된다. The grain size of aluminum alloy was refined to the submicrometer level by using equal-channel angular pressing(ECAP). The effect of grain size refinement was evaluated by the tensile test, micro-hardness test, microstructure observations, ultrasonic test and acoustic emission test. The strength and the Vickers hardness were increased significantly according to grain size refinement after equal-channel angular pressed. The ultrasonic velocity was faster after equal-channel angular pressed, and high frequency range appeared. The results of the ultrasonic velocity and the frequency range are expected to be basic data that can prove the grain size refinement.

전도성을 가지는 탄소나노튜브강화 알루미나복합소재의 마이크로방전가공에서 초음파진동 부가에 의한 가공특성

강명창(Myung-Chang Kang),탁현석(Hyun-Seok Tak),이창훈(Chang-Hoon Lee),김남경(Nam-Kyung Kim) 한국기계가공학회 2014 한국기계가공학회지 Vol.13 No.6

Micro-holes of conductive ceramic are required in micro structures. Micro-electrical discharge machining (Micro-EDM) is an effective machining method since EDM is as process for shaping hard metals and complex-shaped holes by spark erosion in all kinds of electro-conductive materials. However, as the depth of micro hole increases, the machining condition becomes more unstable due to inefficient removal of debris between the electrode and the workpiece. In this paper, micro-EDM was performed to evaluate machining characteristic such as electrode wear, machining time, taper angle, radial clearance with varying voltage and ultrasonic vibration on 10 vol.% Carbon-nanotube reinforced conductive Al₂O₃ composite fabricated by spark plasma sintering in previous research.

초음파 홀 가공에서 공구 형상 디자인에 관한 연구

이항(Hang Li),고태조(Tae Jo Ko) 대한기계학회 2014 대한기계학회 춘추학술대회 Vol.2014 No.11

초음파 가공(Ultrasonic Machining: USM)은 비열 비화학 그리고 비전도의 방법이기 때문에 공작물 재료의 물리적 화학적 변화가 발생하지 않는다. 이러한 특성으로 인해 초음파 가공기술은 전기 전도성과 관련 없는 고경도 재료, 유리나 세라믹과 같은 취성 재료의 가공에 적합하다. 그러나 단점으로는 초음파 진동을 이용하여 취성재료를 가공하는 경우 크랙이 빈번하게 발생한다. 본 연구에서는 초음파 가공의 공구 형상을 디자인 하여 홀 입구 및 출구에 크랙을 감소시켰다. Ultrasonic machining (USM) does not involve heating or any electrochemical effects and so, it causes low surface damage, has small residual stress, and does not rely on the conductivity of the workpiece. These characteristics are suitable for the machining of brittle materials such as glass or ceramics. However, USM for brittle materials generates cracks on the workpiece. Therefore, in this study, the shape of tool is designed to decrease the occurrence of cracks in the entrance and exit of holes in USM .

초음파 진동을 하는 다이아몬드 연삭공구의 알루미나 세라믹 연삭 가공에 관한 연구

최영재(Young-Jae Choi),송기형(Ki-Hyeong Song),박경희(Kyung-Hee Park),홍윤혁(Yun-Hyuck Hong),김경태(Kyeong-Tae Kim),이석우(Seok-Woo Lee),최헌종(Hon-Zong Choi) 한국기계가공학회 2012 한국기계가공학회지 Vol.11 No.1

In this study, ultrasonic vibration tool designed and made by using FEM analysis. And machining test was carried out in various machining conditions using ultrasonic vibration capable CNC machine. For work material, alumina ceramic (Al₂O₃) was used while for tool material diamond electroplated grinding wheel was used. To evaluate ultrasonic vibration effect, grinding test was performed with and without ultrasonic vibration in same machining condition. In ultrasonic mode, ultrasonic vibration of 20㎑ was generated by HSK 63 ultrasonic actuator. The two grinding speeds, 1.67㎧ and 3.35㎧, were applied. On the other hand, grinding forces were measured by KISTLER dynamometer.

초음파를 이용한 CVD-SiC 미세 홀 가공기술에 관한 연구

허찬(Chan Hur),채승수(Seung-Su Chae),이충석(Choong-Seok Lee),김택수(Taeck-Soo Kim),이종찬(Jong-Chan Lee) 한국기계가공학회 2007 한국기계가공학회 춘추계학술대회 논문집 Vol.2007 No.-

The ultra-sonic technology has been developed along with development of the IT industry that needs precision parts in semiconductors, aerospac, PDP, LCD and automobile. The application of ultra-sonic vibration is one of the most useful solution in dealing with problems of chipping and cracks during the machining of brittle and difficult-to-cut materials. This study is about machining technology of micro drilling for CVD-SiC using ultra-sonic machining. The experiments of the ultra-sonic machining, in which abrasive particles in slurry with water are presented to the work surface in the presence of an ultra-sonic vibrating tool, were carried out under various normal forces from 5N to 20N. The experimental results show that the ultra-sonic machining technology can be effectively utilized in micro drilling of CVD-SiC

A Study on the Development of Rotary Ultrasonic Machining Spindle

Chang-Ping Li(이상평),Min-Yeop Kim(김민엽),Jong-Kweon Park(박종권),Tae-Jo Ko(고태조) 한국기계가공학회 2015 한국기계가공학회지 Vol.14 No.4

Ultrasonic machining (USM) has been considered a new, cutting-edge technology that presents no heating or electrochemical effects, with low surface damage and small residual stresses on brittle workpieces. However, nowadays, many researchers are paying careful attention to the disadvantages of USM, such as low productivity and tool wear. On the other hand, in this study, a high-performance rotary ultrasonic drilling (RUD) spindle is designed and assembled. In this system, the core technology is the design of an ultrasonic vibration horn for the spindle using finite element analysis (FEA). The maximum spindle speed of RUM is 9,600 rpm, and the highest harmonic displacement is 5.4 μm noted at the frequency of 40 ㎑. Through various drilling experiments on glass workpieces using a CVD diamond-coated drill, the cutting force and cracking of the hole entrance and exit side in the glass have been greatly reduced by this system.

치과용 골 수술기의 초음파 진동자 설계 및 평가

박기문(Ki-Moon Park),김정현(Jung-Hyun Kim),고태조(Tae Jo Ko) 한국기계가공학회 2016 한국기계가공학회지 Vol.15 No.3

A dental ultrasonic surgical instrument, commercially known as a scaler, is a high-value-added advanced technology that is used for tartar removal, implant operations, and gum and jaw bone surgery. In this study, the piezoelectric phenomenon for making linear motion associated with input electrical signals was studied, and the behavior of the ultrasonic vibrator was investigated by using the commercially available finite element program ANSYS® for the purpose of designing dental surgery tools. Modal analysis was carried out, and the optimal frequency range was calculated from the analyzed results. The ultrasonic vibrator was then redesigned based on the calculated optimal frequency range. The performance of the system was tested, and consequently, the proposed methodology was proven useful in vibrator design.

미세구멍의 방전가공에 관한 연구

윤재웅,양민양 대한기계학회 1990 대한기계학회논문집 Vol.14 No.5

본 연구에서는 초음파 화학 가공(ultrasonicassisted chemical mahining)을 이용하여 100$\mu\textrm{m}$이하의 전극봉을 제작하였고 제작한 전극을 이용하여 미세구멍을 방전 가공함으로써 가공특성을 파악하고, 방전액을 각각 등유(kerosene)와 물로하여 구멍의 표면을 비교, 분석하였으며 전극의 지름, 가공물의 두께에 대한 오버컷과 경사도(tap- er) 그리고 전극의 마멸을 조사하였다. Micro-hole drilling by EDM and production of fine rods for the tool electrode or other purpose have become very important in industry. This paper suggests a new method for production of very fine rods by ultrasonic-assisted chemical machining and describes the machining characteristics of micro-hole drilling by EDM. For fine rods, copper wires of initial diameter of 250.mum are used and successfully machined into a diameter of less than 30.mum with good repeatability. The ultrasonic agitation not only accelerated the material removal rate uniformly, but also produced smooth surfaces of fine rods. To drill the micro-hole, kerosene and pure water is used as a dielectric. From the experiment, water is superior to kerosene with respect to surface roughness of inlet and outlet of hole and machined surface as well as electrode wear. However, due to the electrochemical reaction of water, small pits are remained on the workpiece surface.