• 한국CDE학회논문집
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• 제18권5호
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• pp.367-373
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• 2013

In this study, the penetration characteristic from the cubic and cylindrical penetrator consisting of tungsten material with the velocity of 2,300 m/s is evaluated and the penetration possibility into the target is confirmed. The design of shape and size of penetrator is directly related to space and weight of the warhead. AUTODYN-3D simulation is used to study the penetration effect of penetrator. The purpose of numerical analysis is to verify the penetration characteristic with various L/D penetrator. The penetration performance of penetrator with identical weight due to the shape is also confirmed. The cylindrical and cubic penetrator has enough penetration energy on constant target body. Because the possibility of 2'nd penetration is important factor after 1'st penetration into target body, residual velocity of residual mass must be existed as much as possible. As geometrical shape ratio increases, penetration performance is confirmed to improve.

• 한국재료학회지
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• 제18권3호
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• pp.128-136
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• 2008

Evaluation of the solid surface properties by an analysis of the liquid penetration rate into powder beds is very important in applications of powder products. The penetration rate is related the surface property in powder beds. In order to analyze the surface property of powders, the contact angle values of several powders were obtained using the Washbun equation and the Wicking method. The surface free energy value ${\gamma}S$ was divided into a polar component ${\gamma}S^p$ and a dispersion component ${\gamma}S^d$. Inorganic powders such as calcite were used as test samples. The effects of the particle size and the type of experimental liquid on the penetration rate were measured. It was confirmed that the surface free energy of the grinding sample is smaller than that of the classification sample.

• 대한금속재료학회지
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• 제46권5호
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• pp.296-303
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• 2008

Hydrogen permeation through dense palladium-based membranes has attracted the attention of many scientists largely due to their unmatched potential as hydrogen-selective membranes for membrane reactor applications. Although it is well known that the permeation mechanism of hydrogen through Pd involves various processes such as dissociative adsorption, transitions to and from the bulk Pd, diffusion within Pd, and recombinative desorption, it is still unclear which process mainly limits hydrogen permeation at a given temperature and hydrogen partial pressure. In this study, we report an all-electron density-functional theory study of hydrogen permeation through Pd membrane (using VASP code). Especially, we focus on the variation of the energy barrier of the penetration process from the surface to the bulk with hydrogen coverage, which means the large reduction of the fracture stress in the brittle crack propagation considering Griffith's criterion. It is also found that the penetration energy barrier from the surface to the bulk largely decreases so that it almost vanishes at the coverage 1.25, which means that the penetration process cannot be the rate determining process.

• 한국해안·해양공학회논문집
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• 제23권1호
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• pp.11-17
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• 2011

항만콘크리트 구조물의 내구성 저하의 중요한 요인은 염소이온침투에 의한 철근의 부식이다. 따라서, 항만콘크리트 구조물의 염소이온 깊이와 깊이별 염소이온농도를 정량적으로 파악할 수 있다면, 구조물의 잔존수명을 사전에 비교적 정확하게 평가할 수 있다. 이러한, 구조물에서의 염소이온농도를 예측하기 위해서는 모델식의 개발이 필요하고 모델식은 정확한 현장데이타를 기반으로 한다. 이에 본 연구에서는 현장 항만구조물에 대한 코어시료를 채취하고 본 시료들에 대한 염소이온침투깊이와 깊이별 염소이온농도를 측정하고자 하였다. 시료는 1차로 완도항, 마산항, 인천항에서 채취하였고, 2차로 여수항과 동해항에서 채취하였다. 수직 높이별 영향을 파악하기 위해서 대기부, 비말대, 간만대로 나뉘어 각 층별 8개의 시료를 획득하였다. 채취된 시료중에서 4개는 강도 실험을 실시하였고, 나머지 4개로 내구성 실험을 실시하였다. 2개의 시료에 대해서는 질산은 변색법을 이용하여 염소이온 침투깊이를 측정 하였다. 나머지 2개의 시료는 깊이별로 5 mm 두께의 절편을 채취하고 이를 ASTM C 114의 시험법에 따라 염화물 이온농도를 측정하였다. 측정결과를 바탕으로 지역과 수직위치에 따른 염소이온 침투의 특성을 파악하였다.

• 지질공학
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• 제31권4호
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• pp.541-547
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• 2021

비탈면의 유실, 붕락사고 등 비탈면에 대한 안정성을 파악하기 위해서 지층의 구성상태, 역학적 특성 등의 지반정보 파악이 필요하다. 이러한 지반정보를 파악하기 위해서 일반적으로 표준관입시험(SPT) 및 콘 관입시험 등이 널리 이용되고 있다. 대부분이 급경사로 이루어지고 진입로가 없는 비탈면에 대한 접근성 문제로 표준관입시험이 널리 활용되지 못하고 있다. 이러한 단점을 보완할 수 있는 있는 휴대용 장비인 Drop Cone Penetrometer(DCP)를 이용한 조사도 여러 가지 문제로 제한적으로 사용되고 있다. 따라서 본 연구에서는 비탈면 현장접근이 용이한 휴대용 시추기와 동적콘관입시험 모듈을 개발하고, 개발된 동적콘관입시험기를 이용한 결과와 동일 현장에서 수행한 표준관입시험값과 상관성을 분석하였다. 에너지전단율로 보정된 동적콘관입시험과 표준관입시험간의 상관식은 N_d' = 3.13 N'으로 나타났다.

• 한국군사과학기술학회지
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• 제9권3호
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• pp.88-94
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• 2006

In order to substitute current aluminum sabot and to increase the penetration performance of the kinetic energy projectiles, the research and development program for composites sabot has been conducted. For carbon/epoxy composites sabot, unidirectional carbon fiber reinforced epoxy prepreg was chosen and thick sectioned composites preforms with the different fiber angles along the circumferential direction of sabot were prepared by compression molding under the careful processing conditions at $150^{\circ}C$ for 1hour with $70kgf/cm^2$ curing pressure. The composites sabot demonstrated a weight reduction by approximately 30% than that of current aluminum sabot. The muzzle velocity of a kinetic energy projectile with composites sabot was measured to be about 63m/s higher than that with aluminum sabot. These results imply that the penetration performance is expected to be considerably increased when the composite sabot is applied to the kinetic energy projectiles.

• 에너지공학
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• 제17권1호
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• pp.31-37
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• 2008

현재 에너지 효율프로그램에 대한 수요관리 목표량과 투자비는 과거 실적 데이터를 바탕으로 단일한 Bass 확산 모형을 이용하여 산정되고 있다. 국내외적으로 제품 등의 보급량 예측에 널리 사용되는 Bass 확산 모형은 시간과 세 가지 계수들에 대한 함수로 표현되며, 계수들의 추정에 있어서 제품의 과거 실적 데이터의 충분한 확보가 필수적이다. 국내의 경우 에너지 효율 측면에서 고효율기기의 수요관리 목표량 산정을 위해 기기별 보급량 예측이 선행되어야 하며, 기기별 보급량 예측은 Bass 모형을 근간으로 하고 있다. 그러나 현재 진행 중인 고효율기기 보급 프로그램의 조명기기, 인버터, 자판기와 전동기는 그 진행이 길지 않아 Bass 확산 모형을 이용한 보급량 예측에 필수요건인 충분한 실적 데이터가 존재하지 않은 실정이다. 이는 기기의 미래 보급량 예측에 큰 오차가 발생할 수 있으며 보급 예측량에 대한 정확성을 기대하기 어려우므로 앞으로의 고효율기기의 보급 예측의 방식에 제도적 개선이 필요한 상황이라 할 수 있다. 본 논문에서는 Bass, virtual Bass, Logistic과 Lawrence & Lawton 확산 모형을 이용하여 각 고효율 기기의 미래 보급 확산 추이를 살펴보았다. 또한 기기별 특성에 따른 모형 선호도 평가를 위해 통계랑 기준에 근거하여 실적 데이터와의 오차 범위를 산정하였다. 이 결과를 바탕으로 각 확산 모형을 이용한 기기 보급량 예측에 있어서 확산 모형의 단순 적용에 따른 오차 발생 원인과 기기별 특성에 따른 확산 모형 선호도를 분석하였다.

• Geomechanics and Engineering
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• 제12권5호
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• pp.771-783
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• 2017

Using a transparent fracture replica with aperture size and water-cement ratio (w/c), the factors affecting the penetration behavior of rock grouting were investigated through laboratory experiments. In addition, the waterproof efficiency was estimated by the reduction of water outflow through the fractures after the grout curing process. Penetration behavior shows that grout penetration patterns present similarly radial forms in all experimental cases; however, velocity of grout penetration showed clear differences according to the aperture sizes and water-cement ratio. It can be seen that the waterproof efficiency increased as the aperture size and w/c decreased. During grout injection or curing processes, air bubbles formed and bleeding occurred, both of which affected the waterproof ability of the grouting. These two phenomena can significantly prevent the successful performance of rock grouting in field-scale underground spaces, especially at deep depth conditions. Our research can provide a foundation for improving and optimizing the innovative techniques of rock grouting.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2004년도 추계학술대회 논문집
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• pp.274-279
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• 2004

Currently, carbon-fiber reinforced plastics(CFRP) are widely used in both space and civil aircraft due to their superior stiffness and strength to weight ratios compared to conventional metallic materials. This paper is to study the effects of curvature and stacking sequence on the penetration characteristics of composite laminated shell. And were performed to investigate the penetration characteristics of composite laminated shells by the oblique impact. They are stacked to [0$_3$/90$_3$]s, [90$_3$/0$_3$]s and [0$_2$/90$_3$/0]s, [90$_2$/0$_3$/90]s their interlaminar number two and fore. They are manufactured to varied curvature radius (R=100, 150, 200mm and $\infty$). When the specimen is subjected to transverse impact by a steel ball, the velocity of the steel ball was measured both before and after impact by determining the time for it to pass two ballistics-screen sensor located a known distance apart. In general, the critical penetration energy interface decrease and slope angle on the impact surface increased. [0$_3$/90$_3$]s and [0$_2$/90$_3$]s specimens higher than [90$_3$/0$_3$]s and [90$_2$/0$_3$/90]s specimens.

• 비파괴검사학회지
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• 제28권4호
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• pp.372-376
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• 2008

We report experimental results on the correlations between welding penetration depth and the frequencies of the radiation from the welding pool. Various welding samples such as SUS304, brass, SUS316, etc. have been investigated with 2 kW CW Nd:YAG laser welding machine. The radiation signals from the plume generated by the interactions between the welding sample and laser with respect to the defocusing length was measured with fiber system collecting the plume signal. Analysis of the frequencies by using fast Fourier transform (FFT) shows that the penetration depth is deep as plume signal frequencies are low, shallow penetration depth for high frequencies. Frequencies up to 250 Hz for obtained signals can be analyzed with the discrete FFT. This is the useful method fur closed loop control of the laser power with respect to the welding penetration depth and is used for real time inspection of the welding quality.