• Journal of The Korean Society of Grassland and Forage Science
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• v.36 no.4
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• pp.271-279
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• 2016

The objective of this study was to determine the effect of the moisture content and pellet mill type on the physical and chemical characteristics of Italian ryegrass (IRG) pellet. Moisture content of raw material significantly (p<0.05) affected IRG pellet formation. Moisture content at 25% was the best condition for IRG pellet formation in terms of shape, power load and temperature changes. The hardness of pellet was decreased when moisture content was increase. However, the hardness of pellet was not affected by pellet mill type. Moisture content at 30% dramatically (p<0.05) decreased the durability compared to moisture content at 25%. Dry matter content of IRG pellet was increased (p<0.05) after pelleting. Total count of microorganism was decreased in pellet due to pressure heat and moisture losses during the pelleting process. These results indicated that the proper moisture content of Italian ryegrass pelleting would be at 25%. In addition, Roll & flat die type would be more suitable than Ring die and Die & flat die type in IRG pelleting. Pelleting works would be beneficial for improving forage quality and long storage.

• Design & Manufacturing
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• v.11 no.3
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• pp.41-45
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• 2017

Drones can be manipulated in a variety of ways. One of the most common controller is joystick method. But joystick controller uses both hands and takes a long time to learn. Particularly, in the case of 8-character flight, it is necessary to use both front and rear flight (pitch), left and right flight (Roll), and body rotation (Yaw). Joystick controller has limitations to intuitively control it. In particular, when the main body rotates, the viewpoint of the forward direction is changed between the drones and the user, thereby causing a mental rotation problem in which the user must control the rotating state of the drones. Therefore, we developed a motion matching controller that matches the motion of the drones and the controller. That is, the movement of the drone and the movement of the controller are the same. In this study, we used a gyro sensor and an acceleration sensor to map the controller's forward / backward, left / right and body rotation movements to drone's forward / backward, left / right, and rotational flight motion. The motor output is controlled by the throttle dial at the center of the controller. As the motions coincide with each other, it is expected that the first drone operator will be able to control more intuitively than the joystick manipulator with less learning.

• Journal of the Korean Society for Precision Engineering
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• v.25 no.10
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• pp.115-121
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• 2008

This paper presents bisymmetric dual iron core lineal motor stage for heavy-duty high precision applications such as large area micro-grooving machines or high precision roll die machines. In this stage, two iron core linear motors are installed in laterally symmetric way to cancel out the attractive forces. Main focus was given to analyzing the effect of cogging force and moment for two different layouts, which are symmetric and half-pitch shifted ones. Experimental results showed that the symmetric layout is more adequate for high precision applications because of its clear moment cancellation effect. It was also verified that the effect of the residual cogging moment can be suppressed further by increasing the bearing stiffness. One problem of the symmetric layout is added cogging force which hinders smooth motion, but its effect was relatively small compared with that of moment cancellation.

• Journal of Powder Materials
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• v.22 no.2
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• pp.105-110
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• 2015

In this study, effect of core-shell structure on compaction behavior of harmonic powder is investigated. Harmonic powders are made by electroless plating method on Fe powders. Softer Cu shell encloses harder Fe core, and the average size of Fe core and thickness of Cu shell are $34.3{\mu}m$ and $3.2{\mu}m$, respectively. The powder compaction procedure is processed with pressure of 600 MPa in a cylindrical die. Due to the low strength of Cu shell regions, the harmonic powders show better densification behavior compared with pure Fe powders. Finite element method (FEM) is performed to understand the roll of core-shell structure. Based on stress and strain distributions of FEM results, it is concluded that the early stage of powder compaction of harmonic powders mainly occurs at the shell region. FEM results also well predict porosity of compacted materials.

• Journal of Industrial Technology
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• v.24 no.A
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• pp.29-35
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• 2004

Fine blanking can be considered as a manufacturing process capable of producing sheet metal parts with completely smooth edges that may be hardly obtained by conventional shear-cutting procedures. This fact, together with the considerable economic advantages offered by this process, has been responsible for the rapid acceptance of fine blanking throughout the manufacturing industry all over the world, and the discovery of many new applications. This study was performed to investigate the effect of clearance and V-ring shape on the quality of sheared surface in a fine blanking process. The critical value needed to apply the normalized Cockcroft-Latham fracture criterion to the simulation of fine blanking is obtained by correlating the result of finite element analysis and that of experiment for the uniaxial tensile test. From finite element analysis of an axisymmetric fine blanking process, it has been found that punch load, die-roll depth, burnish zone size and shape of sheared surface are considerably influenced by clearance and V-ring shape.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.13 no.6
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• pp.87-93
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• 2004

An experimental is carried out to investigate the characteristics of blanking for nickel alloy Alloy42 (t=0.203mm), a kind of IC lead frame material. By varying clearance between die and punch the shapes of shear profile are examined. Finite element analysis with element deletion algorithm for ductile fracture mode is also carried out to study the effect of clearance theoretically and to compare with experimental results. The rectangular shape specimen with four different comer radius is used to study the characteristics of blanking for straight side and comer region simultaneously. As the result the ratios measured k(m experiment of roll over, burnish and fracture zone based on initial blank thickness are compared with those of FE analysis. Both experiment and FE analysis show that the amount of mil over and fracture is increased as the clearance increases. When the radius of comer is less than thickness of blank it has been found that larger clearance is required than that of straight region in order to maintain same quality of shear profile at the comer region.

• Transactions of Materials Processing
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• v.25 no.2
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• pp.116-123
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• 2016

Press-brake bending is used to shape flat and thick plates into a targeted circular configuration without excessive localized thinning or thickening. A brake bending press called 'a knife press bending apparatus' has been widely adopted to manufacture thick, large and long pipe from initially thick plate. Submerged Arc Welded (SAW) pipes are also produced by employing press-brake bending. These pipes are mainly used for oil, natural gas and water pipelines. The principal process variables for press-brake bending can be summarized as stroke of the press-brake knife, the distance between both roll in the lower die, and the feeding length of the plate. Many combinations of these process variables are available, thus various pipe diameters can be realized. In the current study, a series of repetitive numerical simulations by feeding a thick plate with initial thickness of 25.4mm were conducted with the consideration of elastic recovery. Furthermore, an index for SAW pipe production is proposed which can be widely used in industry.

• 한국초전도학회:학술대회논문집
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• v.10
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• pp.276-279
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• 2000

When high temperature superconducting tapes is fabricated using the PIT (Powder In Tube) method, the length of HTS tapes is increased more than 500 ${\sim}$ 1,000 times of initial powder packed billet. On mechanical processing, heterogeneous properties between the ceramic superconducting core and Ag/Ag alloy sheath occur the non-uniformity deformation as like sausaging that deteriorate the critical current properties of HTS tapes. In this study, we investigated the workability of Bi-2223/Ag/Ag alloy sheath tapes fabricated by the PIT method involving a number of different mechanical processes, multi drawing and rolling. In order to obtain the high critical current density and high uniformity of Bi-2223/Ag sheath tapes, the influences of powder packing density, drawing die angle and rolling parameters were studied. We found that the roll diameter is an important variable in the rolling process, as critical current of tapes rolled using 250 mm rolls was higher than that using 150 mm rolls.

• Transactions of Materials Processing
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• v.25 no.4
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• pp.268-274
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• 2016

In the automotive seat industry, the use of a fine blanking press is important for manufacturing of high precision products. Among them, a gear part which is a main component of an automotive seat recliner is generally manufactured by fine blanking press. However, the use of conventional mechanical press has been increasing in manufacture of gear part because of low productivity of fine blanking press. In this study, new forming process is suggested to fabricate the gear part with high precision by using mechanical press. The effect of flow restriction die (FRD) which has the restriction of blank edge on dimensional accuracy is investigated by FE-analysis. FE-analysis results for different conditions of FRD indicated that FRD has high dimensional accuracy with the lowest roll-over and the highest perpendicularity of gear part. After application to fabrication of the gear part using mechanical press, the measured dimensional characteristic was compared with the required specification of final product. In addition, results of the performance test showed that the product fabricated by developed process satisfied the required strength and durability. The results show that the suggested forming process by using FRD and mechanical press can replace fine blanking on the viewpoint of dimensional accuracy and productivity.

• Transactions of Materials Processing
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• v.18 no.1
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• pp.67-72
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• 2009

This paper covers finite element simulations to evaluate tube bending process of auto chassis component i.e. trailing-arm product. The rear of the auto chassis structure is primarily composed of CTBA and trailing-arm. When a car rolls into a corner, the trailing arm reacts to roll in the same degree as the car body. During the bending process of trailing arm the tube undergoes significant deformation. Thus forming defects such as excessive thinning and flattening of the tube will be formed in the outside of the tube. In this paper, we analyzed the effect of process parameters in rotary draw bending process and searched the optimized combination of process parameters using orthogonal arrays method to minimize the forming defects. In this process we analyzed several parameters which are displacement of pressure die, boosting force, initial position of mandrel bar, dimensions of mandrel in regarding to the thinning and flattening of the tube.