• Steel and Composite Structures
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• 제3권4호
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• pp.289-306
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• 2003

A series of tests was conducted to study the behaviour of steel-composite sandwich beams under low velocity hard impact. Damage characteristic and performance of sandwich beams with different spacing of shear connector were evaluated under impact loading. Thin steel plates were used as top and bottom skins of the sandwich beams and plain concrete was used as the core material. Shear connectors were provided by welding of angle sections on steel plates. The sandwich beams were impacted at their midpoint by a hemi-spherical nose shaped projectile dropped from various heights. Strains on steel plates were measured to study the effects of impact velocity or impact momentum on the performance of sandwich beams. Spacing of shear connectors is found to have significant effects on the impact response of the beams.

• 항공우주시스템공학회지
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• 제6권4호
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• pp.12-17
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• 2012

This paper is focusing on the define the safety of high speed projectiles from aerodynamic load. The Fin loaded from aerodynamic is the roll of high speed projectile's gide. The Fin can rotate about 25deg as maximum, and it has maximum aerodynamic load with 25deg position. For finite element analysis from aerodynamic load, fluid analysis will be conducted before structure analysis and export pressure data. The pressure data will be used as load condition at structure analysis of Fin. The result of structure analysis of Fin, there is some stress concentration and stress closed with yield stress of material. But this problem will be solved with change to another material.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2009년 춘계학술대회논문집
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• pp.310-314
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• 2009

A numerical code for the interior ballistics has been investigated. The method of the ghost cell extrapolation has been used for the moving boundary with the projectile movement. The porosity effect and the Ergun's Equation have been used in the numerical calculation for the grain combustion. The calculation results of the numerical code have been compared and verified through those of the lumped parameter method. Computerization techniques of the numerical analysis for the interior ballistics have been developed.

• 한국세라믹학회지
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• 제29권4호
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• pp.312-318
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• 1992

Two kinds of alumina specimens with different grain size (1 and 51 $\mu\textrm{m}$) but same density were prepared by hot-pressing. Fracture strength and fracture toughness of these specimens at low strain rate, sonic velocity, and elastic property were evaluated. Ballistic performance against Cal. 50 AP projectile was characterized by thick-backing method by using A16061-T6 reference block. Mechanical properties measured at low strain rate showed that the specimen with samll grain (SG) were better than specimen with large grain (LG). Fracture strength and fracture toughness of LG specimen were 131 MPa and 3.01 MPa{{{{ SQRT { m} }}, but those of SG specimen were 349 and 4.23, respectively. Sonic velocity and elastic properties of these specimen were similar, but bulk velocity and bulk modulus were different at amount of 4 and 9%. The tendency of ballistic performance was not consistent with the mechnaical properties at low strain rate. The ballistic performance based on quantitative efficiency revealed that the LG specimen (5.13) was ballistically better than the SG specimen (4.00) in spite of their lower mechanical properties.

• 한국항공우주학회지
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• 제45권6호
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• pp.473-480
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• 2017

군용 헬리콥터는 피탄에 의한 폭발을 방지하기 위한 OBIGGS System을 장착하고 있다. OBIGGS 경고등은 이상감지 시에만 작동해야 하나, 초도생산 과정에서 빈번하게 이상 작동을 하여 설계개선이 요구되었다. 본 논문에서는 OBIGGS 경고등 이상 점등 원인을 검토하고 개선방안을 수립 및 입증하였다.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2001년도 춘계 학술대회논문집
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• pp.60-65
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• 2001

The projectile afterbodies for zero-lift drag reduction has been analyzed using the Navier-Stokes equations with the $\kappa-\epsilon$ turbulence model. The numerical method of a second order upwind scheme has been used on unstructured adaptive meshes. Base drag reduction methods that have been found effective on axisymmetric bodies include boattailing, base bleed, base comustion, locked vortex afterbodies and multistep afterbodies. In this paper, the charateristics of turbulence flow have been studied for geomeries of multistep afterbodies. The important geometrical and flow parameters relevant to the design of such afterbodies have been identified by number, length and height of step. The flow over multistep afterbodies has been analyzed including expansion waves, recompression waves, recirculating flow, shear flow and wake flow. The numerical results have been compared and analyzed with the experimental datum.

• 한국연소학회지
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• 제1권1호
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• pp.83-91
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• 1996

A numerical study is carried out to examine the ignition and propagation process of detonation wave in SCRam-accelerator operating in superdetonative mode. The time accurate solution of Reynolds averaged Navier-Stokes equations for chemically reacting flow is obtained by using the fully implicit numerical method and the higher order upwind scheme. As a result, it is clarified that the ignition process has its origin to the hot temperature region caused by shock-boundary layer interaction at the shoulder of projectile. After the ignition, the oblique detonation wave is generated and propagates toward the inlet while constructing complex shock-shock interaction and shock-boundary layer interaction. Finally, a standing oblique detonation wave is formed at the conical ramp.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2003년도 제21회 추계학술대회 논문집
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• pp.145-150
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• 2003

The present study aims to optimize the performance of the Two-Stage Gas Gun by using the experimentally obtained data. RSM(Response Surface Method) was adopted in the optimization process to find the operating parameter than can maximize the projectile speed with the minimum number of tests. To decide the test points which results can consist of the response surface, 3$^{k}$ full factorial method was used, and the design variables were chosen with piston mass and 2$^{nd}$ driver fill pressure. The response surface was composed by nine test results and consequently the optimization was done with GENOCOP III, inherently GA code, in order to seek the optimal test point. The optimal test condition from the response surface was verified by the experiment. Results showed that the optimization process with response surface can successfully predict the test results fairly well. This study shows the possibility of performance optimization for the experimental facilities using numerical optimization algorithm.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2008년도 제30회 춘계학술대회논문집
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• pp.244-247
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• 2008

ISL의 초폭굉 모드 램 가속기 실험을 바탕으로 하여 혼합기 강도를 조정하여 수치해석을 수행하였다 ($3.0CO_2$ 희석과 $2.5CO_2$ 희석). 계산결과 $3.0CO_2$ 희석의 경우는 초기 점화가 이루어지지 않아 탄체가 가속되지 않은 반면 $2.5CO_2$ 희석을 한 경우에는 점화가 이루어지고 높은 가속을 보임을 알 수 있었다. 이것은 탄체의 가속성능이 혼합기의 강도에 단순히 비례하지 않으며 점화가 가능한 최소한의 혼합기 강도 이상에서만 초폭굉 모드 램 가속기가 정상적으로 작동함을 알 수 있었다.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2009년도 춘계학술대회 논문집
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• pp.211-214
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• 2009

강내탄도 전산 해석 코드를 사용하여 점화제 주입 특성에 따른 강내탄도의 성능을 연구하였다. 점화제 주입 최대위치가 Base에 가까울수록 균일한 압력 분포가 나타났고 탄자의 탈출 속도도 증가하였다.