• Journal of Advanced Marine Engineering and Technology
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• 제26권2호
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• pp.192-199
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• 2002

In continuous galvanizing process, the mass of zinc deposited and its distribution are controlled by the air pressure, effective distance from the air knife nozzle to the steel strip surface and line speed. Coating defects are resulted from the unbalance of these control factors and the inaccuracy of coating equipments. This paper investigates the main cause of coating deviation and a new air knife system for control of coating thickness was developed. We investigate dynamic pressure variation by air knife types. It is found that the coating deviation is caused by the unbalance of dynamic pressure, the irregularity of strip position, and the strip vibration. Formulating a useful coating model by using present working condition, an optimal working condition is suggested. The productivity and coating quality are improved by applying the result of this research at the shop floor.

• 대한소아치과학회지
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• 제26권2호
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• pp.240-247
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• 1999

치아우식증, 외상, 발육성 결함으로 광범위한 수복이 필요한 유전치의 치료는 소아치과의사에게 있어 매우 까다로운 문제이다. 이상적인 수복술식은 강도, 내구성, 심미성과 장착의 효율성을 모두 갖추어야 한다. 이에 행동조절문제가 있는 어린이를 치료하는 기술적 문제를 더하면, 여러 가능한 수복 방법 중에서 적절한 술식을 선택하는 것은 어려운 일이다. 현재 사용되는 수복술식에는 복합레진의 접착을 사용한 celluloid strip crown, conventional stainless steel crown, open-faced stainless steel crown, commercially 및 chairside veneered stainless steel crown과 epoxy-coated stainless steel crown 등이 있다. 이 모든 술식이 나름대로의 기술적, 기능적 또는 심미적 단점을 갖고 있어 각각의 효율적이고 효과적인 사용을 위해서는 적절한 선택이 중요하다. 이에 저자는 이러한 여러 가지의 전장피개수복 방법을 사용해 유전치를 치료하여 그 결과를 보고하는 바이다.

• 대한기계학회논문집A
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• 제20권9호
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• pp.2901-2907
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• 1996

Flatness of cold rolled strip is vital to the quality of the product and productivity of the mill. Therefore, in recent year requirement for flatness control in strip rolling have become increasingly severe. The necessity for more accurate automatic gauge control and automatic flatness control(AFC) has increased by customer's requirement for cold rolled steel sheets with thinner gauge and better flatness quality. In this paper, the performance and functions of AFC system installed on the 4 hi-reversing mill has been investigated under actual conditions. The test results are as follows : The more strip thickness is thick, the smaller the I-value. The I-value is a strain measured by stressometer. Complex distributions of strip tension are controlled to remove not only a quarter buckle but also a simple center wave and edge wave. The defects caused by poor flatness have been drastically decreased. And a proper coolant temperature for work roll cooling system on the AFC system is about $50~55^{\circ}C$.

• 소성∙가공
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• 제23권7호
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• pp.425-430
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• 2014

The aim of the current study was to predict the plastic deformation behavior of a heated slab during hot rough rolling. FE-simulations were performed to investigate the metal flow and to locate the position of surface material from the slab through the rough rolling and onto the strip, using a material point tracking technique. In addition, experimental hot rolling trials were conducted where artificial defects were impressed onto a heated slab in order to validate the FE-simulation results. The simulated results show the same tendency of deformation behavior as the experimental measurements. The movement of slab defects from the side surface towards the strip center is directly linked to the extent of lateral spread during the rolling.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1996년도 춘계학술대회 논문집
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• pp.541-545
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• 1996

In this paper, The performance and functions of automatic flatness control system installed on the 4 hi-reversing mill and has been investigated under actualconditions. A new automatic flatness control system incorporates a measuring roll for measurement and correction calculations, hydraulic roll benders, selective roll cooling, and a programmable controller for interface and data logging. The test results are as following. The more the exit steel strip thickness is thick, the smaller the I value, and the more it is thin, the larger the I value. And, a complex distribution of strip tension was controlled, for example, not only a quarter buckle but also a simple center wave and edge wave. Because the tension deviation is larger at acceleration speed and deceleration speed than steady speed, so automatic flatness control system of contact type is better to adopt over 450 m/min, automatic flatness control system reduces rapidly large flatness deviation. The maximum I value of strip has been decreased to 13 I, and defects caused by poor flatness have been drastically decreased. And coolant temperature for work roll cooling system on the automatic flatness control system is better to adopt about 50-55 .deg. C.

• 한국정밀공학회지
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• 제13권5호
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• pp.67-73
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• 1996

The necessity for more accurate automatic flatness control(AFC) system has increased of customers' requirement for cold rolled steel sheet. Therefore, many cold rolling mills replaced its AFC system with a measuring roll of the contact type form the non-contact type. In this paper. The performance of AFC system of contact type has been investigated under industrial conditions. It has two kinds of actuator: roll bender, spot cooling system. The test results are as follows: The more strip thickness is thick, the smaller the I value, and the more it is thin, the bigger the I value. And a complex distribution of strip tension was controlled, for example, not only a pocket wave but also a simple center wave and edge wave. Because the tension deviation is larger at acceler- ation speed and decelerationspeed than steady speed, AFC system of contact type is better to adopt over 50m/mim. AFC system reduces rapidly large flatness deviation. The maximum I value of strip has been decreased to 13 I, and sticker, defects caused by poor flatness, have been decreased about 60%.

• Steel and Composite Structures
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• 제28권1호
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• pp.25-37
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• 2018

For the first time, the parametric instability characteristics of tow-steered variable stiffness composite laminated (VSCL) cylindrical panels is investigated using B-spline finite strip method (FSM). The panel is considered containing geometrical defects including cutout and delamination. The material properties are assumed to vary along the panel axial length of any lamina according to a linear fiber-orientation variation. A uniformly distributed inplane longitudinal loading varies harmoni-cally with time is considered. The instability load frequency regions corresponding to the assumed in-plane parametric load-ing is derived using the Bolotin's first order approximation through an energy approach. In order to demonstrate the capabili-ties of the developed formulation in predicting stability behavior of the thin-walled VSCL structures, some representative results are obtained and compared with those in the literature wherever available. It is shown that the B-spline FSM is a proper tool for extracting the stability boundaries of perforated delaminated VSCL panels.

• 한국컴퓨터정보학회논문지
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• 제25권3호
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• pp.19-26
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• 2020

일반적으로 품질 관리는 많은 제조 공정, 특히 주조 또는 용접과 관련된 공정의 기본 구성 요소가 된다. 그러나 사람이 일일이 수동으로 품질 관리 절차를 하는 것은 종종 시간이 걸리고 오류가 발생하기 쉽다. 최근 고품질 제품에 대한 요구를 만족시키기 위해 지능형 육안 검사 시스템의 사용이 생산 라인에서 필수적이 되고 있다. 본 논문에서는 이를 위해 딥 러닝 기반의 ShuffleDefectNet 결함 감지 시스템을 제안하고자 한다. 제안된 결함 검출 시스템은 NEU 데이터 세트의 결함 검출에 대한 여러 최신 성능들보다 높은 평균 정확도 99.75% 정도를 얻는다. 이 논문에서 여러 다른 트레이닝 데이터로부터 최상의 성능을 탐지하고 탐지 성능을 관찰하였다. 그 결과 ShuffleDefectNet의 전체 아키텍처를 사용할 때 정확성과 속도가 크게 향상됨을 알 수 있었다.

• 비파괴검사학회지
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• 제17권3호
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• pp.162-173
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• 1997

최근 산업 발전에 따라 철강 제품의 수요 증가와 함께 품질의 고급화에 대한 요구도 점차 증가하고 있는데, 이러한 수요자의 요구에 부응하기 위해 철강업계는 냉연 강판 표면결함검출기(surface defect detector; SDD)를 도입 운용하고 있다. 그러나 현재 국내 철강 제조업체들이 보유하고 있는 상용 SDD는 결함의 검출에는 매우 효율적이지만 결함의 분류에는 아직 만족할만한 성능을 보여주지 못하고 있다. 그 이유는 SDD가 결함 분류를 위해 채택한 분류표분류기(classification table; CT)는 시험 표본의 모든 특징값들이 분류표의 범위 내에 있을 때만 결함의 분류를 정확히 수행하기 때문에 결함 분류 정확도가 낮을 뿐 아니라, 분류 법칙의 설정을 작업자의 수작업에 의존하고 있어 현장 적용을 더욱 어렵게 하고 있다. 이러한 단점을 극복하기 위해 본 연구에서 학습 표본으로부터 확률밀도함수를 추정하고 여기에서 분류 법칙을 자동적으로 결정하는 방법을 제시하였고, 강화분류표분류기(enhanced classification table; ECT)와 확률신경회로망분류기(probabilistic neural network; PNN)를 새롭게 제안하여 이들 분류기를 실제적인 문제에 적용하였다. 그 결과 ECT와 PNN 모두 결함 분류 성능을 획기적으로 높일 수 있는 좋은 방법이며, 특히 PNN은 아주 구별하기 어려운 결함도 구별해내는 능력이 있을 뿐 아니라, 병렬 처리 능력을 가지고 있기 때문에 다량의 데이터를 실시간으로 처리해야 하는 경우에 적용할 수 있는 매우 효율적인 분류기임을 확인하였다.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2002년도 Proceedings of the International Welding/Joining Conference-Korea
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• pp.355-360
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• 2002

ElectroSlag Strip Overlaying (ESSO) process has been around since 1970. ESSO process had limited acceptance due to a few problems associated with the use of this process in its very early stage. Limited knowledge and, most significantly, poor quality of the equipment and welding flux gave the ESSO process a bad name. However, this process is well accepted today and used in North America, Europe and Japan. The ESSO process provides low dilution overlays at high deposition rates, excellent and consistent deposit chemistry with excellent surface quality, and virtually no defects. Capitan has taken this process one step further through extensive research and development of the process itself as well as the equipment. The improvement brought to the process warranted the issuance in May 2000 of an US patent. This study demonstrates the feasibility of this process with immediate positive production results. The main achievements of this work are as follows: $\textbullet$ Development of six various strip-flux combinations on three different base materials: carbon steel, $\frac{1}{4}$ Cr/.5 Mo and 2 $\frac{1}{4}$ Cr/l Mo, fully tested with: penetrant, ultrasound, bends, hardness, overlay chemistry, corrosion and hydrogen disbonding. $\textbullet$ 12" dia. 90 hot formed elbows from straight pipe electroslag overlayed with "1 layer" and "2 layer" Alloy 625 $\textbullet$ a very unique development of miniaturized overlaying equipment able to perform overlay in pipe with diameters as low as 10" (254 mm). This development has large applications in the field of offshore, petrochemical, refining, pulp and paper and power generation industries. The aftermath of this development was its immediate acceptance by major end users with the completion of four projects of overlayed pipe in the USA and Far East Asia.