• Journal of Ocean Engineering and Technology
• /
• v.7 no.2
• /
• pp.121-130
• /
• 1993

A study off riction welding of high speed steel(SKH 51) bar for blade side to carbon steel(STC 3)bar for shank side was carried out experimentally through tensile test, hardness test, microstructure, and acoustic emission (AE) test. So, this paper deals with optimizing the welding conditions and the real-time quality (strength) evaluation of friction weleded joints by acoustic emission technique. The results obtained are summarized as follows: (1) For friction welded joints of SKH 51to STC 3 steel bars, the total upset (U) increases linearly with an increase of heating time (t sub(1)). (2) The determined optimum welding conditions are heating time (t sub(1)) 7-9 sec, upsetting time (t sub(2)) 5 sec, heating pressure(P sub(1)) 12 kg sub(f)mm supper(2), upsetting pressure (P sub(2)) 15 kg sub(f) mm supper(2) and rotating speed (n) 2, 000 rpm, resulting in a computed relationship between the tensile strength of the joint .sigma. (kg sub(f) mm supper(2)) and the heating time t sub(1) (sec) as the following. sigma.=2.39t sub(1)

• Journal of the Korean Society of Manufacturing Process Engineers
• /
• v.11 no.3
• /
• pp.73-79
• /
• 2012

This paper describes the machining characteristics of the sintered carbide and die steel(STD-11) by electric discharge drilling with various tubular electrodes. Electrical discharge machining(EDM) removes material from the workpiece by a series of electrical sparks that cause localized temperatures high enough to melt or vapourize the vicinity of the charge. In the experiment. four types of electrode which have different diameter are used with the application of continuous direct current and axial electrode feed. The controlled factors include the dimension of the electrode. In drilling by EDM, the dielectric flushed down the interior of the rotating tube electrode, in order to order to facilitate the removal of machining debris the hole. The expansion increase with increasing the thickness of material and the diameter of electrode and the expansion of sintered carbide is 1.75 times large then that of die steel. The taper of machined hole decrease with increasing the thickness of material. The crater sixe of die steel is larger then thet of sintered carbide and the surface roughness of sintered carbide is 1.58 tims larger then that of die steel.

• Journal of the Korean Society of Manufacturing Technology Engineers
• /
• v.7 no.4
• /
• pp.56-63
• /
• 1998

The purpose of this is to analyze experimentally how the change of cutting speed have effects on hole over size of cutting hole, surface roughness of workpiece and roundness during the deep hole machining of SM55C with solid BTA drill using BTA drilling system. Conclusion reached is as follows. (1) The diameter was expanded for 25$\mu$m at the first section and then was reduced 0$\mu$m and 15$\mu$m respectively at the 10m and 20m section comparing to the diameter of tool with respect to the variation of cutting length at 70m/min of cutting speed. 0.15mm/rev of feed. (2) It was proved that roughness was below 8.67$\mu$m for the whole section of cutting length. (3) The roundness has been below 12$\mu$m. Regarding the polygon phenomenon, it has been proved that not only uneven best at 70m/min of cutting speed. 0.15mm/rev of feed.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2009.04a
• /
• pp.504-508
• /
• 2009

To obtain high power, diesel engines continuously increase combustion pressure and mean effective pressure each cylinder, and the excitation sources and noisy sources are increased, too. Moreover, to reduce the costs, shipyards make hull structures weaker than before. As above reasons, it is more difficult to control the vibration phenomenon nowadays. In this study, it was investigated why diesel generator sets reached the vibration allowable limits during the FAT and heavy vibration phenomenon of diesel generator sets using ODS test during onboard tests. Also, it is found out the stiffness of deck and common bed using the test result of their structural impedance. To find out the vibratory characteristics of diesel generator sets, MODAL tests were carried out. From the sensitivity analysis after above tests, it was selected points to be reinforced and studied troubleshooting to solve heavy vibration phenomenon of diesel generator sets.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2003.06a
• /
• pp.593-598
• /
• 2003

Ceramic plates containing many micro-holes are used in diverse applications such as MCP (Microchannel Plate). catalytic converters, filters, electrical insulators in integrated circuits, and so on. One of the efficient methods for machining many holes in ceramic plates is wet drilling of ceramic green bodies followed by sintering them. Since the strength of ceramic green bodies is much lower than the strength of sintered ceramic plate, ceramic green bodies can be drilled with high feed rate. The axial force during micro-drilling of ceramic green bodies increases rapidly at high feed rate, which induces the crack in workpiece. Therefore, the tool lift of micro-drill with respect to feed rate may be determined by the predicting increase of axial force. In this work, the axial force during micro-drilling was calculated using the chip flow model on the micro-drill tip. from which the tool life of diamond abrasive micro-drill during micro-drilling of ceramic green bodies was calculated.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2003.06a
• /
• pp.1853-1856
• /
• 2003

Multi-layer printed circuit board(PCB) is being used widely for the product with relatively complex circuits such as TV, VTR and FAX. With the rapid enlargement of electronic and IT industry, the hole machining technology on multi-layer PCB is increasingly required to improve. Thus, the micro drilling with ultrasonic vibration can be a good method for hole machining. Unlike conventional drilling, ultrasonic vibration applied drilling introduces less wear and fracture of not only tool but also internal surface of workpiece due to little cutting resistance, thus, machinability can be improved. The experiment is conducted through the comparison between the results of conventional drilling and ultrasonic micro drilling as well as among each results by the variation according to not only feed rate of drill but also amplitude and frequency of ultrasonic vibration. The multi-layer PCB consists of 6 layers and ${\Phi}$0.3 diameter drill was used. As a result, it was found that the state of internal surfaces of holes on multiple layer PCBs is improved by the application of ultrasonic vibration.

• Journal of the Korean Society of Manufacturing Technology Engineers
• /
• v.24 no.5
• /
• pp.502-507
• /
• 2015

In this study, a microscale drilling process was conducted to evaluate the cutting characteristics of functionally graded materials. A mixture of M2 and Cu powders were formed and sintered to produce disk specimens of various compositions. Subsequently, a microscale hole was created in the specimen by using a desktop-size micro-machining system. By using design of experiments and analysis of variance, it was found that the M2-Cu composition, spindle speed, and the interactions between these two factors had significant effects on the magnitude of cutting forces. However, the influence of feed rate on the cutting force was negligible. A mathematical model was established to predict the cutting force under a wide range of process conditions, and the reliability of the model was confirmed experimentally. In addition, it was observed that increasing the wt% of Cu in an M2-Cu specimen increased the high-frequency amplitude of cutting forces.

• JOURNAL OF ELECTRICAL WORLD
• /
• s.310
• /
• pp.62-66
• /
• 2002

오늘날의 빌딩이나 역사(驛舍)는 쾌적함을 위해 조명설비, 공조설비, 위생설비, 엘리베이터, 에스컬레이터, 방범방재설비, 통신정보설비 등이 잘 정비되어 있으며, 그 기기 모두는 전기로 작동되고 있다. 빌딩이나 교통전원설비의 리뉴얼공사를 하는 데는 어떻게 빌딩과 교통설비의 기능을 정지하지 않고 단기간에 완성하는가가 중요 포인트가 된다. 미쓰비시(삼릉)전기 플랜트건설총괄부에서는 고객니즈에 대한 검토뿐만 아니라 주변지역에 주는 영향도 충분히 조사하여 빌딩이나 철도 역사에 출입하는 사람들의 안전과 일상생활을 배려한 계획을 세워, 그 시공장소에 적합한 공법 개선과 최적의 기자재 공법을 개발하고 추진하여 안전$\cdot$품질을 충분히 고려한 현지시공을 실시하고 있다. (1) 반입공법 빌딩과 교통시설의 전원설비는 고층이나 지하에 설치되는 일이 많고 건물의 성질상, 전용 반입설비가 확보되어 있지 않는 것이 통상적이다. 동사에서는 고소반입용기기 ''뉴톤밸런스''((1))와 계단용반입기기 ''계단승강기''((2))를 개발하여 단(短)공기로 지역주민이나 빌딩 이용자에게 지장을 주지 않는 공법을 채용하여 높은 평가를 받고 있다. (2) 설치$\cdot$조립공법 건물 내의 작업은 환경을 악화시키지 않는 것이 중요하다. 저소음으로 배기가스를 발생시키지 않도록 ''전동크레인''((3))과 ''돔보(잠자리)크레인''((4))을 채용하고 있다. 또 소음$\cdot$진동을 발생시키지 않는 콘크리트용의 앵커구멍 뚫기장치 ''라구라구(樂樂)드릴''((5))과 앵커타설장치 ''라구라구(樂樂)햄머''((6)) 그리고 앵커강도확인장치 ''라구라구(樂樂)체커''((7)) 등의 기기를 개발하여 작업환경을 향상시켰다. $\divideontimes$ 위의 (1)$\~$(7)과 다음 페이지의 그림 중 (1)$\~$(7)은 대응하고 있다.

• Explosives and Blasting
• /
• v.34 no.2
• /
• pp.10-17
• /
• 2016

Drilling operation for blasting is an important factor to determine blast effect. Drilling errors that arise from performing drilling for blasting purposes can reduce blasting effect causing residual holes, overbreak, and heterogeneous fragmentation, etc. Automatic drilling system was induced for precise drilling. As a result, drilling error caused by spaces between holes and burden was minor at 0~2.6% and accordingly, blasting effect was improved with over 90% drilling rate, the ratio of overbreak amount to total drilling amount at 4.3%, proportion of fragmentation rock under 50cm at 89~95% and so from this analyses, it was estimated to reduce the total cycle times related to blasting process.

• Journal of the Korean Society for Precision Engineering
• /
• v.23 no.9 s.186
• /
• pp.47-53
• /
• 2006

An Experiment was carried out to find the scheme far minimization of burr formation on inclined exit surface in drilling. Several drills with different geometry are used for drilling the workpiece with inclined exit surface. Step drills are specified with step angle and step size. The influence of the inclination angle of exit surface on burr formation was observed, which enables to analyze the burr formation mechanism on inclined exit surface. Along the edge on the inclined exit surface, burrs are formed by the bending deflection to feed direction and also burrs are formed in exit direction of cutting edge. To minimize the burr formed in feed direction, the corner angle which is formed by the inclination angle and step angle must be large enough not to be bent to burr. By decreasing step angle of drill and decreasing the distance between two axes of two holes, burr formation at the intersecting holes can be minimized. Burr formation mechanisms are analyzed according to the drill geometries and cutting conditions. Several schemes far burr minimization on inclined exit surface were proposed.