• 한국정밀공학회지
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• 제18권3호
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• pp.182-188
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• 2001

An experiment is carried out to investigate the characteristics of blanking for copper alloy C194 (t=0.254mm), 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 corner radius is used to study the characteristics of blanking for straight side and corner region simultaneously. As the result, the ratios measured from the experiment of roll over, burnish, and fracture zone based on intial blank thickness are compared with those of FE analysis. Both experiment and FE analysis show that the amount of roll over and fracture is increased as the clearance increases. It has been found that larger clearance is required than that of straight region when the radius of corner is less than thickness of blank, in order to maintain same quality of shear profile at the corner region.

• 소성∙가공
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• 제25권1호
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• pp.12-20
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• 2016

Press machines and dies are commonly used for 3D curved sheet forming. Using conventional die forming can cause economic problems since various modifications of the die shape are required depending on the product shape. Various types of flexible forming such as multi-point dieless forming (MDF), flexible incremental roll forming have been developed to improve the needed process flexibility. Although MDF can reduce the production cost using reconfigurable dies, it still has significant material loss. Drawbacks such as wrinkling, dimpling, and forming errors can also occur despite continuous investigations to mitigate these defects. A novel sheet forming process for 3D curved surfaces, a flexibly-reconfigurable roll forming (FRRF), has been recently proposed to overcome the economic and technical limitations of current practice. FRRF has no limitation on blank size in the longitudinal direction, and also minimizes or eliminates forming defects such as wrinkling and dimpling. Feasibility studies of FRRF have been conducted using FE simulations for multi-curved shapes and various sheet thicknesses. Therefore, the fabrication of a FRRF apparatus is required for any follow-up studies. In the current study, experiments with reconfigurable rollers were conducted using a simple design pre-FRRF apparatus prior to fabricating the full size FRRF apparatus. There are three candidates for the reconfigurable roller: a bar-type shaft, a flexible shaft, a ground flexible shaft. Among these candidates, the suitable reconfigurable roller for FRRF is determined through various forming tests.

• 열처리공학회지
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• 제22권1호
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• pp.16-22
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• 2009

The rolling process is an efficient and economical approach for the manufacturing of plate metals. In the rolling process, the temperature variation is very critical for plate thickness accuracy. The main cause of thickness variation in hot plate mills is the non-uniform temperature distribution along the length of the slab. Also the exit plate thickness is mainly affected by the rolling conditions such as mill modulus, plate thickness and plate width. Hence the thickness variation in top-end is also dependent on these factors. Therefore this study has concentrated on determining the correct amounts of thickness variation due to top-end temperature drop and process parameters.

• 대한기계학회논문집A
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• 제34권11호
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• pp.1623-1630
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• 2010

본 연구에서는 자동차용 시트 리클라이너의 주요 부품인 섹터투스 결합부의 롤오버 저감을 위한 효과적인 성형 방법을 제시하였다. 기존의 성형 공정에 의하여 발생한 과도한 롤오버 때문에 섹터투스 내측기어와 결합 부품인 폴투스 외측기어 간의 정확한 결합이 이루어지지 않아 승차감 및 안전성이 저하된다. 따라서 성형 시, 소재를 롤오버 측으로 유동시켜 롤오버량을 최소화 해야 하며, 이를 위하여 국부 돌기형 다이, 코이닝 펀치를 이용한 방법 및 가변 역클리어런스를 통한 롤오버 저감 방법에 대해 유한요소해석으로 비교 평가 하였고, 이를 검증하기 위해 금형 제작 및 실험을 수행하였다. 실험 결과, 가변 역클리어런스를 이용한 방법이 롤오버 저감 및 금형 강도 측면에서 우수한 특성을 가지는 것을 확인할 수 있었다.

• 한국독어학회지:독어학
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• 제4집
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• pp.129-153
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• 2001

In der vorliegenden Arbeit wird das $Verh\"{a}ltnis$ zwischen den syntaktischen und semantischen Typen von $Konditionals\"{a}tzen$ und deren kommunikativen Funktionen untersucht. Nach der $g\"{a}ngigen$ Auffassung haben Konditionalsatze folgende syntaktische und semantische Eingenschaften: 1. Der Konditionalsatz besetzt das Vorfeld des Hauptsatzes. 2. Im Hauptsatz kann ein Korrelat wie dann eingefugt werden. 3. Mit dem Konditionalsatz wird eine Bedingung oder eine Voraussetzung $f\"{u}r$ den im Hauptsatz $ausgedr\"{u}ckten$ Sachverhalt genannt. Aber im Korpus finden sich auch $Konditionals\"{a}tze$ wie folgende, die keine dieser Eigenschaften haben: (1) Wenn du es noch nicht $wu{\ss}test$, Karl ist wieder im Lande. (2) Wenn ich mal kurz einwerfen darf, er muss sich operieren lassen. Ausgehend van der Annahme, dass die syntaktische und semantische Struktur des $Konditionalsatzgef\"{u}ges$ mit der kommunikativen Funktion des Konditionalsatzes $zusammenh\"{a}ngt,\;wird\;zun\"{a}cht$ versucht, die Typen der $Konditionals\"{a}tze$ aus syntaktischer und semantischer Hinsicht herauszustellen. Danach wird jeder Typ auf die kommunikative Funktion hin $\"{u}berpr\"{u}ft$. Daraus haben folgende Ergebnisse resultiert: 1. Hinsichtlich der syntaktischen Relation zwischen dem Konditionalsatz und dessen Hauptsatz wird zwischen zwei Typen von $Konditionalsatzgef\"{u}gen$ unterschieden: $n\"{a}mlich$, die verbundene und die nicht-verbundene Konstruktion. 2. Hinsichtlich der semantischen Relation zwischen dem Konditionalsatz und dessen Hauptsatz wird zwischen zwei Typen von $Konditionalsatzgef\"{u}gen$ unterschieden: $n\"{a}mlich$, die integrierte und die nicht-integrierte Konstruktion. 3. In der Regel weisen die $Konditionalsatzgef\"{u}ge$ mit der integrierten Konstruktion syntaktisch eine verbundene Konstruktion auf, wahrend die $Konditionalsatzgef\"{u}ge$ mit der nicht-integrierten Konstruktion eine nicht-verbundene Konstruktion haben. 4. In Bezug auf die $illokution\"{a}re\;Selbst\"{a}ndigkeit$ wird zwischen zwei Typen van $Konditionals\"{a}tzen$ unterschieden: $n\"{a{mlich,\;Konditionals\"{a}tze$ mit einer $selbst\"{a}ndigen\;illokution\"{a}ren$ Rolle und $Konditionals\"{a}tze$ ohne eine solche. 5. Die $Konditionals\"{a}tze$ in der verbundenen und integrierten Konstruktion haben keine $selbst\"{a}ndige\;illokution\"{a}re\;Rolle,\;w\"{a}hrend\;die\;Konditionals\"{a}tze$ in der nicht-verbundenen und nicht-integrierten Konstruktion eine $selbst\"{a}ndige\;illokution\"{a}re$ Rolle haben. 6. In Bezug auf die kommunikative Funktion der $Konditionals\"{a}tze$ mit einer $selbst\"{a}ndigen\;illokution\"{a}ren$ Roll wird zwischen drei Typen von $Konditional\"{a}tzen$ unterschieden: Relevanz-Konditionale, metakommunikative Konditionale und diskursstrukturierende Konditionale.

• 대한기계학회논문집A
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• 제28권7호
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• pp.992-998
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• 2004

During the tube hydropiercing, the region adjacent to the pierced hole will be deformed and will be drawn away from the die block as the punch advances through the wall of the tube. The deformation in the region may range from a substantially flat form to a countersunk form, so called rollover. In this study, the effects of material properties, shape of piercing punches, roundness of tube surface and internal pressure within the tube during piercing on the rollover have been investigated experimentally. The results provide the quantitative variation of rollover at given hydropiercing parameters, and a relationship between the deformed radius and the rollover caused by the deformation has been established.

• 한국산업융합학회 논문집
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• 제27권1호
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• pp.1-7
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• 2024

This study was investigated the effect of heat treatment on the microstructure and hardness of internally hardened ductile cast iron roll. The following conclusions were obtained. Some of the graphite was decreased and a bainite was produced by heat treatment. It decreased due to the decomposition of some of the cementite precipitated in the as-cast by heat treatment, but there was no significant change when it reached a certain depth. Hardness increased due to formation of bainite by heat treatment. On the surface, the hardness decreased due to the decrease in the amount of transformation of cementite into bainite, but there was no change beyond a certain depth.

• 소성∙가공
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• 제23권2호
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• pp.103-109
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• 2014

Flexibly-reconfigurable roll forming (FRRF), which is a sheet forming process for multi-curved sheet metal, may solve both the economic and technical problems incurred in using a conventional die forming process. In the FRRF process, the multi-curved sheet metal is formed by different strain distributions on the sheet metal, and the reconfigurable rollers are used as tools during the forming. Therefore, a thorough investigation focused on the reconfigurable rollers is required for the realization of the FRRF process prior to the fabrication of FRRF machine. In the current study, a series of finite element simulations were conducted to study the load distributions experienced by the reconfigurable roller. In order to verify the shape design variables, the effect of the metal thickness on the curvatures of sheet is also presented.

• 소성∙가공
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• 제25권3호
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• pp.161-168
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• 2016

Sheet metals are often required to be formed into three dimensional curved shapes for use as skin structures. As a result various sheet metal forming methods, such as press die forming, stretch forming, and line heating have been used over the years in industrial production lines. Although they are extensively used in industry, these methods are not suitable for small quantity batch productions. Studies have been conducted to improve or replace these methods with plausible flexible forming technologies. As a part of these studies, we developed a new and more efficient forming device named flexibly-reconfigurable roll forming (FRRF). The current study presents the process development and experimental verification for the applicability of this device. To improve the efficiency of the FRRF apparatus, several hardware components were invented and a suitable operating program was developed using MFC of visual C++. The ways to make the FRRF apparatus fully functional are also described. Sheet metal was formed into three dimensional shapes using the FRRF apparatus and the final products are presented as evidence for the applicability of the developed device.

• 소성∙가공
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• 제26권6호
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• pp.341-347
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• 2017

Flexibly-reconfigurable roll forming (FRRF) is a novel sheet metal forming technology conducive to produce multi-curvature surfaces by controlling strain distribution along longitudinal direction. Reconfigurable rollers could be arranged to implement a kind of punch die set. By utilizing these reconfigurable rollers, desired curved surface can be formed. In FRRF process, three-dimensional surface is formed from two-dimensional curve. Thus, it is difficult to predict the forming result. In this study, a regression analysis was suggested to construct a predictive model for a longitudinal curvature of FRRF process. To facilitate investigation, input parameters affecting the longitudinal curvature of FRRF were determined as maximum compression value, curvature radius in the transverse direction, and initial blank width. Three-factor three-level full factorial experimental design was utilized and 27 experiments using FRRF apparatus were performed to obtain sample data of the regression model. Regression analysis was carried out using experimental results as sample data. The model used for regression analysis was a quadratic nonlinear regression model. Determination factor and root mean square root error were calculated to confirm the conformity of this model. Through goodness of fit test, this regression predictive model was verified.