• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2006년 제4회 한국유체공학학술대회 논문집
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• pp.345-348
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• 2006

In sheet metal forming process using press and draw die some defect can be made because of the high pressure of air pocket between draw die and the product. The purpose of this study is to develop a program to decide an optimal combination of air vent hole size and number to prevent those defect on product. The air inside air pocket is considered as ideal gas and the compression and expansion is assumed as isentropic process. The mass flow is computed in two flow condition: unchocked and chocked condition. The present computation obtains required cross-sectional area of air vent hole for not exceeding the user specified pressure such as the pressure for yielding strength of the product or the pressure for unchocked flow. To validate the program the present results are compared with the results of other researchers and commercial CFD code.

• 한국자동차공학회논문집
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• 제16권6호
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• pp.10-18
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• 2008

Metal stamping is widely used in the mass-production process of the automobile industry. During the stamping process, air may be trapped between the draw die and the panel. The high pressure of trapped air induces imperfections on the panel surface and creates a situation where an extremely high tonnage of punch is required. To prevent these problems, many air ventilation holes are drilled through the draw die and the punch. The present work has developed a simplified mathematical formulation for computing the pressure of the air pocket based on the ideal gas law and isentropic relation. The pressure of the air pocket was compared to the results by the commercial CFD code, Fluent, and experiments. The present work also used the Bisection method to calculate the optimum cross-sectional area of the air ventilation holes, which did not make the pressure of the air pocket exceed the prescribed maximum value.

• 한국정밀공학회지
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• 제25권1호
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• pp.72-78
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• 2008

Metal stamping is widely used in the mass-production process of the automobile. During the stamping process, air may be trapped between the draw die and the panel and/or between the punch and the panel. Air pocket rapidly not only increases forming load in the final stage, but also deforms the product just formed by compressive air inside the air pocket in knockout process. To prevent these problems air bent holes are drilled in the die to exhaust the trapped air but all processes associated with air bent holes are performed by empirical know-how of workers in the field due to lack of researches. Therefore this study developed an automated design system for predicting the shape and position, and volume of air pocket on the draw die by using the AutoLISP language under AutoCAD circumstance. The system is able to display the shape of air pocket occurred in the draw die and to calculate automatically its volume by strokes. So it makes a stepping stone to calculate theoretical size of an air bent hole and numbers according to it by predicting and analyzing the position and volume of air pocket. Results obtained from the system enable the designers or manufacturers of the stamping die to be more efficient in this field.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2007년도 춘계학술대회 논문집
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• pp.5-6
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• 2007

• 한국대기환경학회:학술대회논문집
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• 한국대기환경학회 2000년도 추계학술대회 논문집
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• pp.261-262
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• 2000

항공기나 발전용 가스터빈(gas turbine) 및 대용량 압축기(compressor) 등과 같이 흡입공기의 유량이 매우 클 경우, 유입되는 공기 내부에 함유된 입자상 오염물질은 터빈의 기계적 성능에 큰 장애를 일으킬 수 있다(Klink and Schroth, 1996, Schroth, 1993). 이러한 입자상 오염물질을 효과적으로 제어하기 위해서는 처리기체의 유입구 부분에 대형 공기 정화용 여과시스템이 요구되며, 일반적으로 카트리지형 에어 필터(cartridge air filter)나 포켓형(pocket), 카세트형(cassette) 에어 필터가 적용 현장의 조건에 따라 사용된다. (중략)

• 한국기계가공학회지
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• 제2권1호
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• pp.51-56
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• 2003

A custom application system, which was based on the finite element analysis, for stress on the head-skirt junction of a hot pressure vessel was developed. This is useful computer-based analysis system which designed to provide an analysis technique and knowledge conveniently available to other people. It was found the evaluation of thermal stress of several typed skirt joint of a pressure vessel could be performed early using this system.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 춘계학술대회
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• pp.998-1002
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• 2003

This paper investigates the characteristics of stiffness and load in the thrust bearing of spindle which could be changeable according to the groove shape of inlet, in order to design a high-stiffness air bearing by selecting a optimal groove shape. In experiments, dead weight and displacement sensor are used to measure the load carrying capacity and the stiffness respectively. Various shapes and different depth of groove of self-restrictor are used as experimental conditions. Comparative study between the theoretical value and the practical one by measuring the value of stiffness and load of the thrust bearing is performed.

• 한국항공우주학회지
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• 제45권5호
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• pp.417-428
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• 2017

본 논문에서는 항공기 조종사 지능형 헬멧시현시스템(IHDS, Intelligent Helmet Display System)의 아키텍쳐 설계, 단위 구성품 설계, 핵심 소프트웨어 설계내용(헬멧 자세추적, 고도오차 보정 소프트웨어)을 기술하며, 단위시험 및 통합시험에 대한 결과를 기술한다. 세계적인 최신 헬멧시현시스템 개발 추세를 반영하여 3차원 전자지도 시현, FLIR(Forward Looking Infra-Red) 영상시현, 하이브리드형 헬멧자세추적, 바이저 반사형광학계, 야시카메라 영상시현 및 경량 복합소재 헬멧쉘 등의 사양을 설계에 적용하였다. 특히 3차원 전자지도 데이터의 고도오차 자동보정 기법, 고정밀 영상정합 기법, 다색(Multi-color) 조명광학계, 회절소자를 이용한 투과형 영상발광면, 헬멧자세 추정시간을 최소화하는 추적용 카메라, 장/탈착형 야시카메라, 머리 밀착용 에어포켓 등의 신개념의 설계를 제안하였다. 모든 시스템 구성품의 시제작을 완료한 후 단위시험과 시스템 통합시험을 수행하여 기능과 성능을 검증하였다.

• 한국해양공학회지
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• 제23권1호
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• pp.67-73
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• 2009

This study presents the results of a slamming experiment using a pneumatic cylinder. The employment of the pneumatic cylinder showed a relatively good repeatability when the results were compared with those of other slamming devices. The experiment was done for various incident angles. An air pocket was believed to cause a reduction in the magnitude of the impact pressure with an incident angle of $0^{\circ}$ for the water entry. A high speed camera was used in an attempt to locate the time of the contact between the bottom of the specimen and the free surface. It seemed that the maximum pressure occurred before the water contacted the bottom of the specimen.

• 한국해양공학회지
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• 제23권4호
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• pp.12-18
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• 2009

The present study focused on the compressibility of partially filled fluids in a sloshing tank. Filling ratios ranging from 18% to 26% were used to find compressible impact on a vertical wall. The model test was for 1/25 scale of a 138 K LNGC cargo tank. To investigate the two dimensional phenomenon of sloshing, a longitudinal slice model was tested. A high speed camera was used to capture the flow field, as well as the air pocket deformation. The pressure time history synchronized with the video images revealed the entire compressible process. Three typical impact phenomena were observed: hydraulic jump, flip through, and plunging breaker. In particular, the pressure time history and flow pattern details for flip through and plunging breaker are presented.