• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.23 no.3
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• pp.250-258
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• 2014

Due to recent industrial growth and development, there has been a high demand for light and highly durable materials. Therefore, a variety of new materials has been developed. These new materials include carbon fiber reinforced plastic (CFRP or CRP), which is a wear-, fatigue-, heat-, and corrosion-resistant material. Because of its advantageous properties, CFRP is widely used in diverse fields including sporting goods, electronic parts, and medical supplies, as well as aerospace, automobile, and ship materials. However, this new material has several problems, such as delamination around the inlet and outlet holes at drilling, fiber separation, and tearing on the drilled surface. Moreover, drill chips having a fine particulate shape are harmful to the work environment and engineers' health. In fact, they deeply penetrate into machine tools, causing the reduction of lifespan and performance degradation. In this study, CFRP woven and unidirectional prepregs were formed at $45^{\circ}$ and $90^{\circ}$, respectively, in terms of orientation angle. Using a high-speed steel drill and a TiAIN-coated drill, the two materials were tested in three categories: cutting force with respect to RPM and feed speed; shape changes around the input and outlet holes; and the shape of drill chips.

• Tunnel and Underground Space
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• v.18 no.6
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• pp.480-490
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• 2008

The drilling monitoring is a technique to assess rock mass properties by analyzing the mechanical quantities measured by drilling process. Since drilling survey can be conducted on real-time-basis for excavating blast holes or rockbolt holes, it may enables fast and quantitative prediction and evaluation of rock mass. Though a number of studies have been conducted on the drilling data, the selection of drilling parameters and numerical quantification of mechanical quantities or rock mass have not been well established yet. In this study, drilling tests were conducted with homogeneous rock specimen to identify drilling parameters and the relation of the drilling data. As a result, it is verified that above all drilling parameters, the percussion was the most important factor on the excavatability of hydraulic drilling.

• Transactions of the KSME C: Technology and Education
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• v.1 no.1
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• pp.39-47
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• 2013

Top Drive Machine is drilling equipment which transfers motor torque to the drill bit. Kelly Rotary Table of the Derrick Drilling Machine (DDM) is firstly developed at 1983, and the first commercial model DDM 650DC was released at 1984. Offshore drilling business is high value-added industries. "N" Company of U.S.A and "A" company of Norway hold more than 90 percent of the global offshore drill system market, so it is hard to take away market share and develop offshore drilling equipment. Consequently, this paper introduce method for concept design of new reliability machine by limited information. To achieve this, design & analysis tools as CATIA, DELMIA, Pro Engineering, ANSYS were used to evaluate design error and strength/flow analysis at new concept design in Top Drive Machine.

• Transactions of the KSME C: Technology and Education
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• v.1 no.1
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• pp.33-38
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• 2013

Offshore drilling refers to a mechanical process where a wellbore is drilled through a seabed. It is typically carried out in order to explore for and subsequently extract petroleum which lies in rock formations beneath the seabed. There are many different type of facilities from which offshore drilling operations take place. These include bottom founded drilling rigs, combined drilling and production facilities either bottom founded or floating platforms, and deepwater mobile offshore drilling units including semi-submersibles and drillships. These are capable of operating in water depths up to 3,000 m. In this paper, we introduce the drilling system, which is mounted on the offshore drilling facilities.

• Design & Manufacturing
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• v.14 no.2
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• pp.62-68
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• 2020

Recently, research on precise parts required in aerospace, ship, and automobile industries has been actively conducted. In this paper, electron beam drilling machining parameters were selected and experiments were conducted to compare processing characteristics analysis according to machining parameters through machining experiments of a vaporization amplification sheet to which STS 304 was applied. Also, as a result of measuring the machining. As the thickness gradually increased, it was confirmed that the electron beam could not reach the vaporization amplification sheet and thus melted on the surface of the material. As a result of the experimental analysis, it was analyzed that the vaporization explosion reaction of the vaporization amplification sheet was not normally performed due to the working distance (WD) according to the material thickness.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.47 no.12
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• pp.55-67
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• 2010

The electrical properties of a back drilled via-hole (BDH) without the open-stub and the plated through via-hole (PTH) with the open-stub, which is called the conventional structure, in a high-count multi~layered (HCML) printed circuit board (PCB) were investigated for a high-speed digital system, and a selected inner layer to transmit a high-speed signal was farthest away from the side to mount the component. Within 10 GHz of the broadband frequency, a design of experiment (DOE) methodology was carried out with three cause factors of each via-hole structure, which were the distance between the via-holes, the dimensions of drilling pad and the anti-pad in the ground plane, and then the relation between cause and result factors which were the maximum return loss, the half-power frequency, and the minimum insertion loss was analyzed. Subsequently, the empirical formulae resulting in a macro model were extracted and compared with the experiment results. Even, out of the cause range, the calculated results obtained from the macro model can be also matched with the measured results within 5 % of the error.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.14 no.1
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• pp.70-77
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• 2015

This paper develops and evaluates a mechanical machining process which involves drilling on PVS material. According to the material, two treatment experiments were conducted, one involving drilling in a wet condition or using a lubricant and one involving drilling in a dry condition with no lubricant. Drilling in a dry condition showed better performance in terms of the cutting time than in the wet condition. Otherwise, the wet condition has several advantages. The lubricant influenced the burr diameter size and minimized the temperature on the surface of the work piece. During the wet condition drilling process, a smaller burr diameter size was noted as compared to the dry condition. The temperature showed a linear correlation with the drill bit size, where a least-square analysis provided an $R^2$valuewhichexceeded 0.95. The wet condition required more cutting time than the dry condition. In this condition, the water provides a lubrication effect. A thin layer between the cutting edges and the surface of the work piece is formed. The chip formation is affected by the drilling depth. The color on the tips of the chips was darker than in the initial condition. No correlation between the drilling depth and the bore roughness was noted, but the variation of the cutting speed or the RPM influenced the roughness of the bore. The optimum cutting speed ranged from 40 RPM to 45 RPM in the condition which provided the finest roughness surface.

• Journal of Ocean Engineering and Technology
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• v.16 no.6
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• pp.60-64
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• 2002

This paper describes the machining characteristics of the MoSi$_2$--based composites through the process of electric discharge drilling with various tubular electrodes. In addition to hardness characteristics, microstructures of Nb/MoSi$_2$laminate composites were evaluated from the variation of fabricating conditions, such as preparation temperature, applied pressure, and pressure holding time. MoSi$_2$-based composites have been developed in new materials for jet engines of supersonic-speed airplanes and gas turbines for high-temperature generators. These high performance engines may require new hard materials with high strength and high temperature-resistance. Also, with the exception of grinding, traditional machining methods are not applicable to these new materials. Electric discharge machining (EDM) is a thermal process that utilizes a spark discharge to melt a conductive material. The tool electrode is almost -unloaded, because there is n direct contact between the tool electrode and the work piece. By combining a non-conducting ceramic with more conducting ceramic, it was possible to raise the electrical conductivity. From experimental results, it was found that the lamination from Nb sheet and MoSi$_2$ powder was an excellent strategy to improve hardness characteristics of monolithic MoSi$_2$. However, interfacial reaction products, like (Nb, Mo)SiO$_2$and Nb$_2$Si$_3$formed at the interface of Nb/MoSi$_2$, and increased with fabricating temperature. MoSi$_2$composites, with which a hole drilling was not possible through the conventional machining process, enhanced the capacity of ED-drilling by adding MbSi$_2$, relative to that of SiC or ZrO$_2$reinforcements.

• Journal of Korean Tunnelling and Underground Space Association
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• v.17 no.6
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• pp.605-614
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• 2015

A room-and-pillar underground structure is characterized by its grid-type array of room and pillar. As a result, its construction and economical efficiency can be governed by excavation sequence. In this study, the construction period by the drill and blast method which can be treated as a main sequence for excavation was examined by considering the regulation for blasting and construction standard of estimation in Korea. To evaluate the construction period for the room-and-pillar underground structure constructed in 4 kinds of square-type area ($30{\times}30{\sim}57{\times}57m$), the concurrent excavation pattern which was suggested in the previous researches was used. From the suggested condition, the total construction period by drill-and-blast method can be estimated with the consideration of the construction area, number of jumbo drill and faces in operation.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.33 no.3
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• pp.843-854
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• 2013

This paper presents experimental research work for the evaluation of ultimate flexural behaviors of prestressed concrete beams with a corroded tendon. In order to evaluate the effects of loss of prestress or loss of tendon area on the ultimate flexural strength of prestressed concrete beams, static load tests are conducted using five prestressed concrete beams. After exposing prestressing tendons in two test beams using 25mm drill bit, the exposed tendons were corroded using an accelerating corrosion equipment to simulate loss of tendon area. During the tests, steel strains, concrete strains and displacements at the center of test beams were measured, and acoustic emission measurements were conducted to detect wire fractures. Based on the test results, evaluation method for predicting flexural strength of prestressed concrete beams with corroded tendons is investigated. In addition, evaluation methods for predicting the existence of corroded tendons in post-tensioned prestressed concrete beams at service loads are discussed.