• International Journal of Safety
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• v.4 no.2
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• pp.6-11
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• 2005

The goals of the paper are to understand the impact damage behavior and identify the effect of surface protective materials on impact resistance in filament wound composite pressure vessels. For these, a series of low velocity impact tests was performed on specimens cutting from the full scale pressure vessel by the instrumented impact testing machine. The specimens are classified into two types, which are with and without surface protective material. The visualization for impact damage by two different impactors is made by metallurgical microscope. Based on the impact force history and damage, the impact resistance parameters were employed,rod its validity in identifying the damage resistance of filament wound composite pressure vessel was reviewed. As the results, the impact resistance of the filament wound composites and its dependency on the surface protective material were evaluated quantitatively

• Transactions of the Korean Society of Mechanical Engineers A
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• v.29 no.8 s.239
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• pp.1109-1117
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• 2005

To identify damage that develops in filament wound composite pressure vessels subjected to low velocity impact, a series of impact tests was performed on specimens cutting from the full scale pressure vessel. The resulting damages by the three different impactors were assessed by the scanning acoustic and metallurgical microscope. Based on the impact force history and damage, the resistance parameters were proposed and its validity in identifying the damage resistance of CFRP pressure vessel was reviewed. As the results, the impact resistance of the filament wound composites and its dependency on the impactor shape were estimated quantitatively.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.25 no.10
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• pp.1427-1435
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• 2001

Air movement in wokplaces, whether resulting from a forced ventilation system or naturally occurring airflow, has a significant impact on occupational health. In a huge shipbuilding factory building, typical harmful factors such as fume or vaporized gas from welding and cutting of steel plates, and dusts from grinding give unpleasant feeling. From field data survey, the yearly dominant, wind directions for the shipbuilding factory building tested were northwest, northeast and southeast Among the three wind directions, the ventilation improvement was the worst for the northeastern wind. This study was focused on location of the opening vents in order to utilize the natural ventilation effectively. Instantaneous velocity fields inside the 1/1000 scale-down factory building model were measured using a 2-frame PIV system. The factory building model was embedded in an atmospheric boundary layer simulated in a wind tunnel. The modified vents improve the internal Ventilation flow with increasing the flow speed more than two times, compared with that of present vents.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.28 no.7
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• pp.834-841
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• 2004

Experimental study on the three-dimensional topology of hairpin packet structures in turbulent boundary layers were carried out. Two different Reynolds number based on momentum thickness, Re$\sub$$\theta$/=514 and 934 were generated in a blowing type wind tunnel under the condition of zero pressure gradient. Simultaneous measurements of velocity fields at a wall-normal plane and wall-parallel plane by a plane PIV and a Stereo-PIV systems. The two Nd:Yag laser systems and three CCD cameras were synchronized to obtain instantaneous velocity fields at the same time. To avoid optical noise at the crossing line by the two laser light sheets, a new optical arrangement using polarization was applied. The obtained velocity fields show the existence of hairpin packet structure vividly and the idealized hairpin vortex signature is confirmed by experiment. Two counter-rotating vortex pair which reflects the cutting plane of hairpin legs are found both side of a strong streaky structure when the wall-normal plane cuts the hairpin head.

• Journal of the Society of Naval Architects of Korea
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• v.31 no.3
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• pp.129-134
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• 1994

A Laser Cutter is designed for the precise fabrications in the shipyards recently. The cutter is a gantry type one with specified functions of movability and strength in order to satisfy the workability. The gantry frame should move with a certain velocity in a relatively short time for the proper cutting of the object materials. The gantry is fitted with ball screw and the acceleration field is formed by actuating this ball screw. The relative displacement should be within the allowable design criteria to make sure the precise cutting of the materials by the laser. In this paper, modal and structural analysis for a Laser Cutter which is commonly used in the shipyards, is carried out to check the design criteria of the system. The system is modeled by placing the proper shell and soils finite elements and fictitious mass properties to represent the real one. The way how to extract the loading conditions based on the given velocity criteria of the system is presented. Static structural analysis is performed and the results came out as expected. Modal analysis for finding eigen-values and mode shapes of the system is performed and it is shown that the time dependent dynamic analysis is unnecessary for this system for its operating circumstances.

• Journal of Biosystems Engineering
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• v.4 no.1
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• pp.1-23
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• 1979

The use of barley seeder attached to rotary tiller in the rural area has a significant meaning not only for the solution of labor peak season, but also for the increase of land utilization efficiency. The facts that presently being used barley seeders are all based on the mechanical principles of the reverse rotation, center drive and are all using forward rotating tine, which is used to be easily and heavily worn out when it rotates reversely, raise problem of recommending them to rural area in Korea. Therefore, the main objective of the study was to develop new type of rotary tine attachable to barley seeders. To attain the objective the following approaches were applied. (1) The kinematic analysis of reverse rotating barley seeders. (2) The studies on the soil bin and artificial soil. (3) The comparative experiment on the power requirement of prototype tine. The results obtained from the studies are summarized as follow: 1. The kinematic analysis of barley seeder attached to rotary tiller: The following results were obtained from the kinematic analysis for deriving general formulae of the motion and velocity characterizing the rotary tine of barley seeders presently being used by farmers. a) The position vector (P) of edge point (P) in the rotary tine of reverse rotating, center drive was obtained by the following formula. $$P=(vt+Rcos wt)i+Rsin wt j+ \{ Rcos \theta r sin \alpha cos (wt- \beta +\theta r) +Rsin \theta r sin \alpha sin (wt-\beta + \theta r) \} lk $$ b) The velocity of edge point $(P^')$ of reverse rotating, center drive rotary tine was obtained by the following formula. $$(P^')=(V-wR sin wt)i+(w\cdot Rcoswt)j + \{ -w\cdot Rcos \theta r\cdot sin \alpha \cdot sin (wt-\beta +\theta r) + w\cdot Rsin \theta r\cdot sin \alpha \cdot cos (wt- \beta + \theta r \} k $$ c) In order to reduce the power requirement of rotary tine, the angle between holder and edge point was desired to be reduced. d) In order to reduce the power requirement, the edge point of rotary tine should be moved from the angle at the begining of cutting to center line of machine, and the additional cutting width should be also reduced. 2. The studies on the soil bin and artificial soil: In order to measure the power requirement of various cutting tines under the same physical condition of soil, the indoor experiments Viere conducted by filling soil bin with artificially made soil similar to the common paddy soil and the results were as follows: a) When the rolling frequencies$(x)$ of the artificial soil were increased, the densIty$(Y)$ was also increased as follows: $$y=1.073200 +0.070780x - 0.002263x^2 (g/cm^3)$$ b) The absolute hardness $(Y)$ of soil had following relationship with the rolling frequencies$(x)$ and were increased as the rolling frequencies were increased. $$Y=37.74 - \frac {0.64 + 0.17x-0. 0054x^2} {(3.36-0.17x + 0.0054x^2)^3} (kg/cm^3)$$ c) The density of soil had significant effect on the cohesion and angle of internal friction of soil. For instance, the soil with density of 1.6 to 1.75 had equivalent density of sandy loam soil with 29.5% of natural soil moisture content. d) The coefficient of kinetiic friction of iron plate on artificial soil was 0.31 to 0.41 and was comparable with that of the natural soil. e) When the pulling speed of soil bin was the 2nd forward speed of power tiller, the rpm of driving shaft of rotary was similar to that of power tiller, soil bin apparatus is indicating the good indoor tester. 3. The comparative experiment on the power requirement of prototype tine of reverse rotating rotary: According to the preliminary test of rotary tine developed with various degrees of angle between holder and edge pcint due to the kinematic analysis, comparative test between prototype rotary tine with $30 ^\circ $ and $10 ^\circ$ of it and presently being used rotary tine was carried out 2nd the results were as follows: a) The total cutting torque was low when the angle between holder and edge point was reduced. b) $\theta r$ (angle between holder and edge point) of rotary tine seemed to be one: of the factors maximizing the increase of torque. c) As the angle between holder and edge point ($\theta r$) of rotary tine was $30 ^\circ $ rather than $45 ^\circ $, the angle of rotation during cutting soil was reduced and the total cutting torque was accordingly reduced about 10%, and the reduction efficiency of total cutting torque was low when the angle between holder and edge point ($\theta r$) of rotary tine was $10 ^\circ $, which indicates that the proper angle between holder and edge point of rotary tine should be larger than $10 ^\circ $ and smaller than $30 ^\circ $ . From above results, it could be concluded that the use of the prototype rotary tine which reduced the angle between holder and edge point to $30 ^\circ $, insted of $45 ^\circ $, is disirable not only decreasing the power requirements, but also increasing the durabie hour of it. Also forward researches are needed, WIlich determine the optimum tilted angle of rotary brocket, and rearrangement of the rotary tine on the rotary boss.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.1678-1681
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• 2005

The disk cam mechanism cam produce a positive motion with a relatively few components. In the present paper a shape design of cam using the relative velocity method and the machining information analysis using the circular interpolation are introduced. In the first part of the paper a machining information at each point using the circular interpolation is taken. This study purposes the analysis method of the cutting error due to the moving path of the cutter, so that we can lead to the optimum design in a disk cam mechanism..

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.24 no.6
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• pp.599-604
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• 2015

Currently, the coolant system in industrial sites is an efficient process to keep clean cutting oils. However, the damage to a pump occurs due to a chip and debris when inhaled into the pump, and thus problems such as the reduction of both efficiency and lifespan might arise. In this study, a new type of filter was developed in order to primarily prevent the damage from the pump impeller and make it unnecessary to have the replacement and cleaning at the same time. This study found the problem reducing the suction volumetric efficiency and cavitation when inhaled, and conducted a method to solve the problem compared to the result of fluid analysis according to two velocity conditions. As a result, this study achieved the effect of lowering the pressure and meeting the suction flow rate by connecting the four filters.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.18 no.10
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• pp.99-103
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• 2019

Recently, as the high-precision machinery industry has developed rapidly, peripheral equipment has been developed to improve machining efficiency. Peripheral equipment for machining includes cooling units, housings, oil separators, and much more. Oil, such as cleaning and cutting fluids, is used for machining. When waste oil is reused, the contamination of the workpieces and reduction in machining accuracy are generated by the waste oil, including sludge. Therefore, the development of an oil separator is necessary for efficiently separating oil, water, and sludge. The purpose of this study is to analyze the oil separation efficiency and flow characteristics of a high-speed centrifugal separator according to the rotation velocity and diffusion plate. The oil separation efficiency and flow characteristics were analyzed using hydrodynamic theory and computational fluid dynamics (CFD). The results of this study will be used as basic data for the development of a high-speed centrifugal separator.

• Journal of Biosystems Engineering
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• v.35 no.6
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• pp.373-379
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• 2010

This study was carried out to develop a belt pick-up type one-row soybean cutter, using physical properties and production conditions of soybeans. The prototype soybean cutter consisted of 4 parts: cutting part, conveying part, collecting part, and travelling part. The prototype soybean cutter was designed to cut soybeans planted with a row spacing of 600 mm, and at a height of 30 mm from the bed bottom using a disk saw. Through various trials with different peripheral velocities of the disk saw and forward speed of the cutter, determined ranges of the peripheral velocity of the disk saw cutting soybeans stems were greater than 18.3 m/s. Spacing between pick-up belts (clearance) was in a range of 60~90 mm so that soybeans could be picked at heights greater than 25 cm, and the size and shape of the pick-up belt were determined the conventional manual harvesting method. The optimal ratio between the forward speed of cutter and the peripheral speed of pick-up belts were from 1 to 1.2 by theoretical analysis. the pick-up belts had a $35^{\circ}$ of tilted angle and $90^{\circ}$ of twisted angle to pick up soybeans safely from the plant input to the lower end of the belts and convey soybeans to the upper end of belts nearby a container. The soybeans at the rear container were dropped down on the soybean row with an interval. The effective field capacity of the prototype soybean cutter was 0.136 ha/h, reducing the working hour by 92% when compared with the manual cutting.