• Journal of the Korean Society for Precision Engineering
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• v.28 no.6
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• pp.709-715
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• 2011

Chattering in cutting operations are usually a cumbersome part of the manufacturing process in mechanical. Particular, machining performance such as that of the boring process is limited by cutting condition at the movable components. Among various sources of chatter vibration, detrimental point in cutting condition is found a mechanical condition on overhang. It limits cutting speed, depth, surface roughness and tool wear failure as result because the all properties are varying with the metal removal process. In this case, we have to observe the resonance frequencies of a boring bar for continuous cutting. In the established research, boring bar vibration of cutting system has been measured with the aid of accelerometer. However, the inherent parameters of internal turning operations are severely limit for the real time monitoring on accelerometers. At this point, this paper is proposed other method for real time monitoring during continuous cutting with optical fiber at the inside of boring bar. This method has been used a plastic fiber in the special jig on boring bar by based on experimental modal analysis. In this study, improvement of monitoring system on continuous internal cutting was attempted using optical fiber sensor of inside type because usually chattering is investigated experimentally measuring the variation in chip thickness. It is demonstrated that the optical fiber sensor is possibility to measure of chattering with real time in boring process.

• Explosives and Blasting
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• v.34 no.2
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• pp.1-9
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• 2016

In this study, the field tests were performed on V-cut, PLHBM 1 hole, PLHBM 2 hole in gneiss area in order to compare the effects of the vibration decay of a tunnel cut-hole according to the number of PLHBM holes with scaled distance. Based on the prediction equation of blasting vibration from the result of the tests, the decay rate of vibration were confirmed 21.8~61.1% using PLHBM 1 hole, 35.7~79.3% using PLHBM 2 hole for scaled distance within $10{\sim}100m/kg^{1/2}$ on the basis of V-cut PPV. As the scaled distance was increased, the effect of vibration decay was decreased. The effect of vibration decay of cut-hole for intial PLHBM 1~2 hole was significantly high.

• Journal of the Korean Society for Precision Engineering
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• v.27 no.8
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• pp.62-69
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• 2010

Internal lathe machining with a boring bar is weak with respect to vibration because the bar is long and slender. Therefore, it is important to study the dynamic characteristics of a boring bar. The purpose of this study was to identify the effects of overhang and cutting conditions on the dynamic response characteristics of a boring bar. For an efficient experiment, an $L_g(3^3)$ orthogonal array was applied and the results were quantitatively analyzed by ANOVA. Overhang, feed per revolution, and depth of cut were selected as independent variables. Meanwhile, dynamic stiffness, damping ratio, damping coefficient, and acceleration were chosen as dependent variables. The vibration signal was obtained from an accelerometer attached to the boring bar, followed by visualization by a signal analyzer. The effect of overhang was found to have a significant effect on the dynamic stiffness, damping ratio, and damping coefficient, but the other variables did not. As the length of the overhang increased, the dynamic stiffness decreased and the damping ratio increased. In addition, the damping coefficient increased until the length of the overhang was 4D (where D is the shank diameter), after which it remained constant. The acceleration decreased until the overhang length was 4D, and then increased sharply when the overhang was increased further. From these results, the behavioral trend of the damping characteristics changed when its overhang length was 4D. Consequently, there is a critical point that the dynamic characteristics of boring bar change.

• Journal of the Korean Geosynthetics Society
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• v.22 no.3
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• pp.61-69
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• 2023

As global trade and maritime port environments change, the need to respond to larger and faster ships is increasing. Accordingly, new ports are being built around metropolitan cities such as Busan and Ulsan. In general, a compaction method using sand or gravel is applied to the construction of a new port. However, due to the lack of sand or gravel and the difficulty in securing economic feasibility due to the increase in unit price, the deep mixing method has recently been used. Therefore, in this study, CMD-SOIL using circulating resources was applied to the Ulsan area, and the applicability was determined by analyzing the laboratory mixing test and boring results at in-situ. As a result of the test, it was analyzed that it showed more than the design mixing strength, and it was possible to secure the similar performance as blast furnace slag cement. In addition, it was analyzed that the design standard strength can be sufficiently secured as a result of in-situ boring. Therefore, considering the field applicability in the Ulsan, it is judged that the use of CMD-SOIL is possible.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.10 no.4
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• pp.82-87
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• 2011

Lubrication has an important role to reduce frictional forces and temperature between cutting chips and the face of a tool. However, it has harmful effects to workers' health and working environment. The purpose of this thesis is to find cutting conditions through the quality analysis in boring for SM45C steel using MQL(Minimum Quantity Lubrication). Machining process is super drill, tip drill, end mill and boring in order. Experimental factors of boring and the quantity of mist air are properly selected. With the analysis of experimental data, this thesis shows that boring with MQL improves the surface roughness when spindle speed is 934rpm or feeding speed is 74mm/min.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.20 no.4
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• pp.495-501
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• 2011

The purpose of this study is to improve the roundness of CNC turning so that helps the operator to choose the right turning conditions to produce a product with the given parameters. This paper focuses on determining the optimal levels of machining factors for circular shaft with CNC turning. For this purpose, the optimization of factors is performed based on experimental design method. A design and analysis of experiments are conducted to study the effects of these factors on the roundness by using the SIN ratio, analysis of ANOVA, and F-test. Factors, namely, fixed pressure, wall thickness, depth of cut, and feed rate are optimized with consideration of the roundness. The boring tool used in this study is a tungsten carbide coated. The material of workpiece is Al6061 and the machining method is dry cutting.

• 한국정보통신설비학회:학술대회논문집
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• 2004.08a
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• pp.215-218
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• 2004

통신서비스를 제공하는 전송매체인 동케이블(copper cable)은 외륵 전자기적 영향으로부터 작업자 및 시설보호를 위해 $300{\sim}500m$ 마다 접지를 하고 있다. 접지는 일반 보안용 접지와 차폐용 접지로 구분할 수 있는데 보안용 접지는 100옴 이하의 접지저항을 요구하지만 차폐용 접지는 10옴 이하의 낮은 접지저항을 필요로 한다. 차폐용 접지는 대표적으로 전력선 또는 전철시설로부터 발생하는 통신선에서의 유도전압(Induced voltage)을 경감시키기 위해 사용되는 것으로 차폐케이블, 유도중화코일, 차폐선 등의 선로시설에 필요하다. 본 논문은 차폐용 접지를 시공하기 위해 적용하는 접지저감재를 활용한 보링접지 시공기술에 관한 것으로 접지저항 산출방법과 산출식에 필요한 파라메터와의 관계 등을 실제 시공결과와 비교하며 분석하였다.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.9 no.3
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• pp.143-149
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• 2000

Grinding technology in morden industry society is focusing on research and development for grinding stone and machin-ing parts for the purpose of high accuracy and high efficiency of products. But in order to equip the high technology and high accuracy of micro stone which is one of grinding stone a continuous effort on R& D is require. In this study the honing processing work of 2 cycle engine cylinder for motorcycle which has an open hole is carried out so as to investigate the boring and hone stone effects on accuracy of honing. As the experimental result of this study we could conclude that it is possible to secure good conditions of honing by controlling and keeping appropriate cycle-time in the stage of boring for the prior step of honing.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.06a
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• pp.1796-1802
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• 2000

The purpose of this work is to analyze the vibration characteristic of boring bar with dynamic vibration absorber and find out the effective design parameters. Using the finite element method and modified optimum design concept, conventional optimum design based on approximate lumped parameter model is checked and practical design to be measured with modal analysis is compared with optimum design from numerical analysis. Also, the performance of reducing vibration is investigated with variation of shape of boring bar. The considered model of boring bar with dynamic vibration absorber is selected among manufactured boring bars with the best performance.

• Journal of the Korean Geotechnical Society
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• v.16 no.2
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• pp.13-22
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• 2000

서해안에 위치한 특정 연구현장에서 연약지반의 압밀거동을 파악하기 위한 소산시험을 포함한 콘관입시험을 수행했다. 연구현장에서 시험시공으로 적용한 연약지반개량공법으로는 압성토공법, 두 종류의 페이퍼드레인 공법, 팩드레인 공법이었으며 각각의 공법들에 있어 현장에서의 지반개량에 따른 압밀거동을 판정하기 위해서 적용되었다. 콘관입시험은 근본적으로 지반개량 전과 후에 보링, 표준관입시험, 압밀시험과 함께 수행되었다. 실내실험과 피조콘관입시험을 비교한 결과, 연약지반의 표층에서는 상당한 지반개량효과가 있었으나 표층아래 심층지반에서는 그렇치 않았다. 그리고 지반개량 후, 10개월이 지난 시점에 압밀시험과 소산시험 결과를 통하여 분석한 수평압밀계수는 압성토 방법을 제외한 3가지 개량공법을 적용한 지점에서 압밀계수는 감소하여 개량효과를 간접적으로 판단할 수 있었다.