• 펄프종이기술
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• 제40권4호
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• pp.66-73
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• 2008

When coated paperboard is printed, pressed into a groove with a creasing rule and folded, white line cracking occurs along the crease due to intensive mechanical pressure. The cracking will deteriorates product quality and waste resources. Effects of creasing pressure and ink dosage on the foldability of coated board were investigated. It was shown that applying an optimum pressure is important during creasing. When the pressure was too low, the crease formed was not sufficiently deep enough to enable precise folding. When an excess pressure was applied, fiber bonding was destroyed, resulted in unsatisfactory cracking. When the coated board was folded in machine direction (MD), long cracks were formed along MD. When it folded in cross direction (CD), the cracks were shorter and formed perpendicular to CD. Printing promoted cracking due to the decrease in flexibility of coated board. In addition, uneven ink film layer on the coating layer caused worse cracking.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2008년도 춘계학술대회 논문집
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• pp.500-502
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• 2008

In generally, a high pressure fuel injection pipe has been often used as a fuel supply line in automobiles or other diesel engines. Such conventional high pressure fuel injection pipe, however, has suffered from the problem that is folding and hair cracks created therein. The defects can be locally formed in the inner wall surface of the pipe at the connecting head leading to a flow path when the pipe is deformed by the heading process. In the study, in order to prevent the folding in the inner wall surface of the pipe during the heading process, FE-analysis has been used in the die design.

• 한국산학기술학회논문지
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• 제20권9호
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• pp.382-389
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• 2019

스털링실버 판재를 콜드-다이 포징(cold-die forging)과 어닐링을 반복하는 폴딩공정을 이용하여 반지모양으로 가공하는 신공정을 제안하였다. 도넛모양으로 재단된 판재에 선폭 $0.43{\mu}m$인 격자를 각인하였다. 그 후 경사가 $45^{\circ}$, $60^{\circ}$, $75^{\circ}$인 다이(die)를 이용한 포징과 어닐링을 반복하여 폴딩하였다. 비교를 위해 어닐링을 생략한 시편 또한 준비하였다. 각인된 격자의 길이 변화를 측정하여, 공정과정에 따른 스트레인을 확인하였다. 버니어캘리퍼스, 비커스 경도 측정기(Vickers hardness tester)와 광학현미경, UV-VIS 컬러미터(colormeter)를 이용하여 크기, 경도, 미세구조, 표면색을 확인하였다. 어닐링을 생략하는 경우 크랙이 발생하였으나, 어닐링을 부가하는 경우 성공적으로 변형이 가능했다. 시편의 거시적인 스트레인을 분석한 결과, 최종공정 후 외경의 길이와 두께는 각각 감소하였지만, 내경의 길이와 폭은 각각 증가하였다. 시편의 미시적인 스트레인은 수평 방향에서 최대 +0.128 만큼 증가하였다. 비커스 경도의 경우, 열처리 시에는 감소하지만 폴딩공정 후에는 증가하는 경향을 나타내었다. 미세구조 관찰 결과 어닐링 직후 결정립의 크기가 증가하고 폴딩공정 직후는 감소하였다. Lab지수를 기준으로 색차는 모든 공정에서 10 이하로 확인되었다. 결국 도넛형태의 은 판재를 폴딩공정을 이용하여 성공적인 반지모양의 주얼리 제조가 가능하였다.

• 펄프종이기술
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• 제46권6호
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• pp.94-102
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• 2014

The physical and chemical properties of recycled fibers from mixed waste paper are more and more deteriorated because of unknown history of recycling times. In order to improve the mechanical properties of liner paper, the recycled fibers from wasted cotton clothes were used in papermaking process, and their applicabilities were evaluated in several points of fiber modification. Thus, two kinds of fiberizing methods from waste cotton clothes were considered by using rotary sandpaper and grinder mill. Finally, the rotary sandpaper method was relatively desirable in preserving longer fiber length and fibrillated fiber surface. The recycled cotton fibers by swelling treatment with NaOH and bleaching with reductive chemicals were mixed with OCC fibers, and the handsheets were prepared to basis weight of $80g/m^2$ and evaluated the mechanical properties of paper. The fibrous properties showed outstanding results in freeness and WRV improvements by alkali treatment and high brightness by reductive bleaching treatment. The physical and mechanical properties of sheet by mixing OCC fibers and recycled cotton fibers were also highly improved in tensile, burst strength and specially folding resistance.

• 한국재료학회지
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• 제26권10호
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• pp.528-534
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• 2016

The aim of this paper is to consider the effect of the manufacturing processes on corrosion and centerline cracking of ancient bronze spoons. The ancient bronze spoons in question were made by several steps of forging, in reheated condition with cast ingots. The manufacturing method is similar to that of the modern spoons. The investigations include observations from light and scanning electron microscopes of the microstructure in terms of the crack propagation. Cracks in the centerline are caused by solute segregation in the center-line region; this solute is solidified in the final stage of bronze spoon manufacture. Centerline cracking is also caused by ${\alpha}$ phase segregation, accompanied by forged overlapping along the longitudinal direction of the spoons. A vertical stripe with cracks along the centerline of the spoon's width is formed by folding in the wrought process. The overlapping area causes crack propagation with severe corrosion on the spoon surfaces over a period of a thousand years. The failure mechanisms of ancient bronze spoons may be similar to that of modern spoons, and the estimation of the failure mechanisms of ancient spoons can be appropriate to determine failure causes for such modern spoons.

• Steel and Composite Structures
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• 제46권3호
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• pp.319-334
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• 2023

Localizing damages is an essential task to monitor the health of the structures since they may not be able to operate anymore. Among the damage detection techniques, non-destructive methods are considerably more preferred than destructive methods since damage can be located without affecting the structural integrity. However, these methods have several drawbacks in terms of detecting abilities, time consumption, cost, and hardware or software requirements. Employing artificial intelligence techniques could overcome such issues and could provide a powerful damage detection model if the technique is utilized correctly. In this study, the crack localization in flat and folded plate structures has been conducted by employing a Backpropagated Artificial Neural Network (BPANN). For this purpose, cracks with 18 different dimensions in thin, flat, and folded structures having 15⁰, 30⁰, 45⁰, and 60⁰ folding angle have been modeled and subjected to free vibration analysis by employing the Classical Plate Theory with Finite Element Method. A Four-nodded quadrilateral element having six degrees of freedom has been considered to represent those structures mathematically. The first ten natural frequencies have been obtained regarding healthy and cracked structures. To localize the crack, the ratios of the frequencies of the cracked flat and folded structures to those of healthy ones have been taken into account. Those ratios have been given to BPANN as the input variables, while the crack locations have been considered as the output variables. A total of 500 crack locations have been regarded within the dataset obtained from the results of the free vibration analysis. To build the best intelligent model, a feature search has been conducted for BAPNN regarding activation function, the number of hidden layers, and the number of hidden neurons. Regarding the analysis results, it is concluded that the BPANN is able to localize the cracks with an average accuracy of 95.12%.

• 소성∙가공
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• 제30권4호
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• pp.165-171
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• 2021

This study was conducted on the manufacturing method of high-strength aluminum bolts. We obtained the displacement-load information by tensile test of the Al 6056 raw material and the T6 heat-treated material and calculated the precise flow stress and fracture limit using repetitive finite element analysis for before and after heat treatment. We designed a multi-stage forging process for T6 heat-treated material, and calculated that the accumulated damage value does not exceed fracture limits by finite element method. We produced the prototype forgings without any harmful defects such as cracks and folding occurring. Bolts made of T6 heat treated material show 9.6%higher tensile strength than T6 heat treated material after wire drawing.

• 한국암반공학회:학술대회논문집
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• 한국암반공학회 2007년도 특별심포지엄 논문집
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• pp.63-79
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• 2007

Several remedial works were attempted to stabilize the collapsed area of the inlet slopes of diversion tunnel, but prevention of any further movement was being only carried out at beginning stage by filling the area with aggregates and rock debris, after several cracks had been initiated and developed around the area. The extra specialty developed folding zone is consisted with highly weathered Greywacke and Black shale. The suggested solution is to improve the properties of the rock mass of failed area by choosing the optimum level of reinforcement through the increment of slope rock support design so as to control the movement of slopes during the re-excavation. The Bakun hydroelectric project includes the construction of a hydroelectric power plant with an installed capacity of 2,520MW and a power transmission system connecting to the existing transmission networks in Sarawak and Western Malaysia. The power station will consist of a 210m height Concrete Faced Rockfill Dam. During the construction of the dam and the power facilities the Balui River has to be diverted of the tunnels is 12m and the tunnel width is 16m at the portal area. This paper describes the stability analysis and design methods for the open cut rock slopes in the inlet area of the diversion tunnels. The geotechnical parameters employed in stability calculations were given as a function of four defined Rock Mass Type (RMT) which were based on RMR system from Bieniawski. The stability calculations procedure of the rock slopes are divided into two stages. In the first stage, it is calculated for the stability of each "global" slope without any rock support and shotcrete system. In the second stage, it is calculated for each "local" slope stability with berms and supported with rock bolts and shotcrete. The monitoring instrumentation was performed continuously and some of the design modification was carried out in order to increase the safety of failed area based on the unforeseen geological risks during the open cut excavation.

• 한국전자파학회논문지
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• 제27권1호
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• pp.8-13
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• 2016

본 논문에서는 잉크젯 프린팅 기술을 이용하여 종이 필름 위에 전도성 잉크를 인쇄하여 방사 패턴 변환이 가능한 종이접기 형태의 안테나를 제안한다. 제안된 안테나는 접었을 때와 펼쳤을 때 각각 다이폴 안테나와 루프 안테나로 동작하며, 종이 필름을 접고 펼치는 방식에 따라 상호 변환될 수 있다. 제안된 안테나는 다이폴 상태와 루프 상태일 때 모두 동일하게 1.85 GHz에서 동작하도록 설계되었다. 종이 필름을 접었을 때 종이 필름의 코팅과 그 위에 인쇄된 전도성 잉크가 깨짐 현상을 해결하기 위해 액체금속(liquid metal)중 하나인 EGaIn(Eutectic Gallium Indium)을 사용하였다. 제안된 안테나의 성능은 시뮬레이션과 실제 측정 결과로 확인할 수 있으며, 다이폴 상태와 루프 상태일 때 안테나 이득은 각각 -4 dBi, -5 dBi이다. 또한, 측정 결과, 다이폴 상태와 루프 상태일 때 서로의 Null 부분을 서로 상호 보완해 주는 것을 확인할 수 있다.

• 광물과 암석
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• 제35권4호
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• pp.485-505
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• 2022

2017년 11월 15일 Mw 5.4의 포항지진은 흥해지역 지하 약 4 km의 진원 깊이에서 발생하여 포항시에 막대한 피해를 끼쳤다. 포항분지의 중부에 해당하는 흥해지역은 백악기 경상누층군과 백악기 말~고신생기 초불국사 화성암류를 기반암으로 하여 포항분지 충전물인 신신생기 연일층군이 분포한다. 이 논문에서는 포항분지에서 지각변형물(습곡, 단층, 절리)과 포항지진 동시성 지표변형물(모래화산, 지표균열, 팝업구조)에 대한 구조지질학적 연구를 수행하여 포항분지의 변형작용사와 포항지진 동시성 지표변형의 특성을 고찰해 보았다. 연구지역의 지각변형물은 제4기 단층운동 이전까지 적어도 5회의 변형단계를 거쳐 형성되었다: (북)북동 주향에 고각 경사하는 정이동(곡강단층) 단층 형성단계, 연일층군에 광역적으로 인지되는 동-서 방향의 고각 절리와 이에 (준)평행한 단층 형성단계, 동-서 주향에 중각 내지 저각 경사하는 공액상 정이동 단층(흥해단층과 형산단층)과 이에 수반된 동-서 계열의 습곡 형성단계, (역이동성) 좌수향 주향이동의 (북)북서 방향 단층조와 우수향 주향이동의 동-서(북동) 방향 단층조가 고각으로 경사하는 공액상 주향이동 단층 형성단계, 북북동과 북북서 주향에 중각 경사하는 공액상 역이동 단층과 이에 수반된 남-북 계열의 습곡 형성단계. 포항지진 동시성 지표변형물에서 모래화산은 종종 지표균열과 (준)평행한 선상배열을 보인다. 남-북 내지 (북)북동 방향의 팝업구조와 지표균열, 동-서 내지 서북서 방향의 지표균열 등은 포항지진 발생 응력원의 최대수평응력에 의한 지진원 단층의 역이동성 운동과 이에 수반된 상반지괴의 좌굴습곡작용에 의해 형성되었다. 이러한 구조적 활동은 지진원 단층의 상반지괴에 해당하는 포항시 흥해읍 중심으로 광범위하게 발생하여 이곳에 막대한 재산 피해를 끼쳤다.