• Journal of the Korean Society for Precision Engineering
• /
• v.34 no.2
• /
• pp.95-99
• /
• 2017

The recent development of core techniques in the IT industry can be summarized as a technical advancement for safety and convenience, and mechanical technology for being "eco-friendly" and lightweight. Under these circumstances, research of lightweight material has become attractive. In this study, CFRP (Carbon Fiber Reinforced Plastic) laminate specimens are subjected to a tensile test using the UTM(Universal Testing Machine, AG-IS 100 kN) to estimate their mechanical properties in terms of the Hole machining impact evaluation. The FEM (Finite Elements Method) analysis method is applied and the material properties obtained from basic experiments such as the Tensile test, the compressive test, and the shear test. CFRP materials properties from a previous study, as well as a finite element analysis program for Hole machining CFRP was compared with the experiments.

• Journal of the Korean Society of Food Culture
• /
• v.7 no.4
• /
• pp.329-338
• /
• 1992

This study was attempted aimed to prepare of Andong sikhe by pure culture inoculation and to improve storage stability by the addition of stabilizers to the product. Lactobacillus delbreuckii was selected for pure culture inoculation in the fermentation. The effect of stabilizers on the sedimentation, sensory evaluation and viscosity of Sikhe were investigated during the fermentation of traditional Andong Sikhe stored at $4^{\circ}C$ Morphological characteristics of Sikhe were determined by scanning electromicrograpy. Among the stabilizers added to the traditional Andong sikhe Na-alginate was found to be best stabilizers. When the product was evaluated by the sensory panel, the addition of stabilizers up to 0.1% level actually increased the acceptability of the product, while the concentration of more than 0.2% stabilizers affected the acceptability of the negatively. Sikhe added Na-carboxymethyl cellulose and Na-alginate showed highest viscosity on the 2nd day of fermentation, while homogenized Andong sikhe with Carrageenan showed the highest peak in viscosity on the first day of fermentation. Lactic acid bacterial count reached to $3.2{\times}10^8/ml$ after 20 days of storage. The surface and cross section of rice was observed by scanning electron microscope. As the fermentation proceeded holes on the surface increased, and nearly empty cell wall remained at the later stage of fermentation. Use of pure cultured inoculum of L. delbreuckii supported the rapid build up of the lactic acid bacteria and consequently the whole process of the fermentation was shortened. The acceptability and product quality were improved by use of L. delbreuckii inoculum.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
• /
• 1997.10a
• /
• pp.37-42
• /
• 1997

This paper describes result of experiment of parameters affecting the micro hole drilling time, kind of assisting gas and it's pressure. The result reveals that parameter value of 0.08J, 20Hz, dwell time of 300 microseconds can be a good machining condition to make micro hole diameter range of 50-70${\mu}{\textrm}{m}$, Assistant gas such air, O2, Ar, N2 was adapted. Assistant gas of air makes heat affected zone enlarge due to burning of material, also it makes hole irregular and damage because of refusion stick to caused by chemical reaction with Al2O3 ceramic material. O2(99.9%) has good characteristic to get good drilling and smooth surface on pressure of 0.2kgf/$\textrm{cm}^2$, but it is expensive. Ar, N2 makes material burn and crack severely and proved to be an appropriate but, Ar was better than N2.

• Journal of Welding and Joining
• /
• v.6 no.3
• /
• pp.37-42
• /
• 1988

The Hole Drilling Method(HDM) is widely used to measure residual stresses in the welded structures. The purpose of this study is to evaluate the accuracy fo measuring residual stresses when drilling the hole by Air-abrasive Jet machine(AJM). Simulated residual stresses wre introduced by applying known stresses to steel bars. These known streses were then compared with measured stresses relaxed from hole drilling. the obtained results are summarized as follows; 1) It was possible to obtain well defined holes with the nozzle designed for this study. 2) If the hole shape is not cylindrical, critical may occur. 3) In the uniaxial strain field, the measurement error of the maximum principal stress was within .+-.10 percent. The orientation angle of the maximum principal stress was within 8.deg. from the given directioin. 4) meausrements were made varying hole depths. Little or no change of stresses occurs since holse were drilled more than the depth of the 0.6 times diameter. 5) The air-abrasive jet machining for drilling holse does not cause appreciable apparent stresses which si critical to measure residual stresses.

• Journal of the Korean Society for Precision Engineering
• /
• v.17 no.3
• /
• pp.114-121
• /
• 2000

A new concept drill was developed recently (or increasing accuracy and productivity in drilling operation. The burr formation in drilling causes many problems in deburring operation because burrs are formed inside holes and it is difficult to remove them. Burr formations are observed in drilling operation with a new concept drill and are compared with conventional HSS drill. Several workpieces with different materials are drilled with several cutting conditions, velocity and feed rate. The burr in drilling can be classified into three types according to the location of crack. To observe the burr formation mechanism, the cap which is formed with the new concept drill is observed and measured.

• Proceedings of the KIEE Conference
• /
• 2007.11c
• /
• pp.128-130
• /
• 2007

외과수술용 핸드피스는 현재 국내 외 병원에서 사용되고 있는 수술 장비 중 필수 보유 장비이다. 선진 수술 기법인 인공관절 대체 수술 시 뼈(Bone)절단, 다듬질 구멍 등, 초 섬세 가공을 목적으로 하는 기기이다. 기존의 공압식(Air Type)은 수술 시 많은 양의 질소(N2 Gas)가 소모됨으로써 질소탱크 보관에 많은 공간이 필요하고 잦은 교체를 필요로 한다. 또한 기계소음과 공압식 호스의 이동으로 시술자와 환자사이에 불편함이 발생하고 감염의 위험성이 있으므로 최근에는 충전식을 선호하고 있다. 이러한 이유로 기존의 공압식을 대체할 배터리형 외과수술용 핸드피스를 연구하게 되었다.

• Proceedings of the KSME Conference
• /
• 2003.04a
• /
• pp.1344-1348
• /
• 2003

It is generally known to be difficult to etch a surface of a transparent material such as fused silica by conventional laser ablation in which the surface is simply irradiated with a laser beam. A lot of studies have been done to provide a method capable of efficiently etching transparent materials without defects such as cracks. One of the promising methods or the micro-machining of optically transparent materials is laser induced etching. In this study, micro-drilling of fused silica by laser induced wet etching was conducted. KrF excimer and YAG laser were used as light sources. Acetone solution pyrene and ethanol solution of rhodamine were used as etchant.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2003.06a
• /
• pp.1780-1783
• /
• 2003

Burrs formed in micro drilling with Ø 1.0 and 0.5 are observed. The changes of burr geometry are compared when feed rate and velocity changes. Characteristics of burr formation in 4 different workpiece materials are analyzed. The coefficient of burr geometry, CB is introduced to classify burrs according to burr height and burr types. Finally control charts are produced using the coefficient of burr geometry and burr types in each workpiece material. Data base is constructed to be used for burr expert system.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 1997.10a
• /
• pp.911-914
• /
• 1997

This Experiment was carried out for bur minimization in drilling. New drill geometries are proposed to minimize the burr formation in drilling operation. Three types of drills are made, champer, round and step drill. The burr formed in first cutting by front cutting edge ca be removed in second cutting by the cutting edges in chamfer, round edge and step. New burrs are formed by second cutting and can be minimized according to the change of drill geometry like, chamfer size and angle, corner radius in round drill and step size and angle in step drill. To measure the burr formed in drilling, laser sensor is used.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2001.11b
• /
• pp.89-92
• /
• 2001

In this paper, we studied on drilling a microscopic hole of glass using electro-chemical discharge methode. In this research, we fabricated a electro-chemical discharge machine for drilling glass hole. The used parameters to get a fine microscopic hole are the concentration of NaOH solution from 5wt% to 50wt%, the supply voltage from 10V to 40V and the fabricating time from 5 second to 50 second. Also, we used a 0.16mm glass plate. We learned from our experiment that, the fabrication most efficient when supply voltage is 25V-30V and concentration of NaOH solution 35wt% or less.