• Journal of the Korea Academia-Industrial cooperation Society
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• v.6 no.5
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• pp.412-417
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• 2005

The objective of study is design and structural analysis of multi-axis drill machine for PCB. This is able to reduce the unit cost of manufacture and to ensure safety, that is with the result of analysis by design the multi-axis drill machine for the use of PCB to enhancing suitability and exactitude in mass production the process of PCB.

• Journal of the Korean Society for Precision Engineering
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• v.12 no.8
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• pp.27-38
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• 1995

For solving troubles happened during the drilling process with carbon fiber epoxy composite materials(CFRP) by using HSS drill, a few types of diamond gift electroplated drills are manufactured, and machinability of these drills is experimented with a variety of cutting speed and feed rate. These drills have some advantages of good wear resistant and the conception of grinding process. As a result, using of these drills improves both troubles being caused by tool wear and damage of exit surface depending on fiber stacking angle. It is desirable that cutting conditions for the cutting thickness per revolution must be set under 0.01mm when the size of a diamond grit is # 60 .approx. 80.

• Journal of the Korean Society for Precision Engineering
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• v.12 no.5
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• pp.77-87
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• 1995

In-process detection of drill wear is one of the most important technoligies for automatic, unmaned machining systems. In this study, an on-line drill wear estimation model based on spindle/Z-axis motor currents generated during the drilling process is proposed. The theoretical model is obtained by integrating the drilling process model and the servomechanism model. The drilling process model describes the relationship of drill wear and drilling torque/ thrust force, whereas the servomechanism model describes the relationship of drilling torque/ thrust force applied to motor and spindle/Z-axis motor current. Evaluation tests have shown that the proposed model is a good real-time estimator for drill wear.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.21 no.1
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• pp.9-14
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• 1976

This experiment was conducted to find out the ., effects of various fertilizer level and Drill-seeding on the growth and yield of the two newly bred naked-barley varieties, Kwangsung and $Bangsa^6$ the former that was bred for the first time in Korea in 1972, is resistant to winter and productive, and the latter that was also bred in Korea by radioisotope treatment in 1974, is of short-stem, early maturing and productive. The grain yield in Drill-seeding was 8 percent higher than that in Conventional seeding. $Bangsa^6$ was more resistant to lodging and more adaptable to the amounts of the increased-fertilizer level than Kwangsung. In Drill-seeding, $Bangsa^6$ is thought to be more suitable naked-barley variety than Kwangsung.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2007.11a
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• pp.181-182
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• 2007

• 대한공업교육학회지
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• v.34 no.2
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• pp.331-345
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• 2009

In this research Sagnac interferometer three different types of mandrel are suggested and this fiber optic sensor is using in monitoring of electric transformer. Vibration characteristics of those mandrels were analyzed and finally more sensitivity mandrel are suggested. Three different mandrels using in fiber optic sensor are hollow cylinder with outer bump, pure hollow cylinder, hollow cylinder with inner bump. Natural frequencies and mode shapes are investigated using finite element method. Mode shape are considered at the frequency range from 2 kHz to 20 kHz. Fundamental dimensions of the hollow cylinder type's mandrel are 30 mm in outer diameter, 50 mm in length, 1 mm in cylinder thickness, $2mm{\times}2mm$ in bump size. Based on the finite element results, when the outer acoustic frequency is near 11 kHz outer bump type and hollow cylinder can get higher sensitivity. Near 17 kHz outer bump and inner bump mandrel can get higher sensitivity. Near 20 kHz hollow cylinder and inner bump mandrel is useful. This results can be applied to design of fiber optic sensor using in monitoring the electrical transformer. Several MHz of outer acoustic frequency can be easily detected using more sensitive mandrel in pursuing expand this technique.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.8 no.1
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• pp.17-29
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• 1970

To research the seeding systems and the varieties adapted to mechanization in barley and wheat culture in Korea, the studies were carried out from October, 1969 to June, 1970 at Suwon. In these studies, six kinds of seeding systems of drilling and dibbling that seems to adapted to mechanization were tested as compared with the customary seeding system, furrowing moderately or widely, using three varieties of barley, Suwon ＃18, Barsoy and Buhufng, and three varieties of wheat, Wonkwang, Yucseung ＃3 and Yeungkwang, under the two fertilizer levels of standard and double. The summarize results gained were as follows; 1. Buhung seemed to be the most suitable variety in barley as it yielded the most and matured early and grew the safest. Barsoy suffered from winter injury. 2. Yeungkwang seemed to be the most suitable variety in wheat as it yielded the most and produced the largest grain ani grew the safest, however it matured late. Wonkwang suffered heavily from lodging injury. 3. More yield were produced and there were no increase of cultural dangers except lodging in double fertilizer level. 4. Seeding system of drilling and dibbling seems to be able to put in practice safely under the double fertilizer level when lodging resistant varieties are selected. 5. Rate of yields increase in comparison with the customary seeding system of moderate furrowing were 16 percent in drilling of 20 centimeter spacing, 13 percent in wide furrowing and 12 percent in dibbling of 20 ${\times}$ 12 centimeter spacing in barley and also 9 percent in wide furrowing, 8 percent in dibbling of 20 ${\times}$ 12 centimeter spacing and 7 percent in drilling of 20 centimeter spacing in wheat. 6. The most important cause of above yields increase seems to be the increase of spike number per unit area. 7. Yields increase by drilling as compared with furrowing was not caused by higher rate of seeding. 8. The plants matured a bit earlier by drilling and dibbling. 9. Better stands of seedling were fount in dibbling due to the promotion of germination by tramping. 10. An increase of yields will be expected by decreasing the spacing in drilling and dibbling.

• Composites Research
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• v.36 no.2
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• pp.132-139
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• 2023

A linerless composite propellant tank was designed and manufactured by using the carbon fiber-reinforced composite materials which have superior strength-to-weight ratio in order to reduce weight of the tank. In this research, we designed a sub-scale composite propellant tank with a diameter of 800 mm to withstand an MEOP of 1.7 MPa. We manufactured the boss of the tank by using the same composite materials to reduce the thermal expansion difference between the boss and the secondary-bonded composite layers of the barrel in the cryogenic environment. We used the collapsible mandrel to manufacture the tank without any liner. The mandrel was made from epoxy-based composite tooling prepregs to reduce weight of the mandrel. We manufactured the test tanks by laying up the carbon fiber fabric prepregs manually on the mandrel and then applying the autoclave cure process. We performed a proof test, a helium tightness test, a repeated pressurization test, and a burst test in room temperature. The test results demonstrate that the proposed design and manufacture process satisfies all strength requirements as well as an anti-leakage requirement.

• The Journal of the Acoustical Society of Korea
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• v.19 no.2
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• pp.8-12
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• 2000

This paper describes the sensitivity stability of a mandrel type fiber optic acoustic sensor with respect to its environmental conditions such as hydrostatic pressure and underwater temperature. The sensors under consideration have various mandrel structures such as a cylindrical mandrel, a concentric composite mandrel, and an air-backed concentric composite mandrel. The analysis results show that the sensors have such good robustness, less than 0.15dB, in its sensitivity with respect to the variation in hydrostatic pressure. Further, the nylon concentric composite mandrel type sensor including an air cavity turns out to have the most superior stability than others to the underwater temperature variations.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.39 no.6
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• pp.575-581
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• 2015

The drill bit, which directly transmits percussive forces and torque to the rock, is the core part of a rock drilling machine. For effective drilling, the button arrangement of a drill bit should be optimized because it is the most important design factor in determining drilling efficiency. Furthermore, a quantitative method is necessary to evaluate the button arrangement for the optimization of the drill bit button. Therefore, we propose a new method for the evaluation of the drill bit button arrangement using new evaluation indices, which include the overlapped impact area, blank area, and moment. Moreover, we verify the suitability of the proposed evaluation method by applying it to the conventional button arrangement.