• 대한기계학회논문집
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• 제18권7호
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• pp.1759-1772
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• 1994

In this study, we re-examined the Tate's modified Bernoulli equation to study penetration phenomena for long rod projectile into single or multi-layered finite thickness plates. We used the force equlibrium equation at mushroomed nose/target interface instead of conventional pressure equation at the stagnation point. In our penetration model, we considered the velocity dependent $R_t$ value for semi-infinite target and considered only the back face effect for finite target. To compensate for $R_t$ value according to target's thickness and back face effect, we used the spherical cavity expansion theory for semi-infinite plate and used the cylindrical cavity expansion theory for finite plate. Also we developed the experimental technique using make screen to measure the penetration duration time at each layered plate. In 3-layered laminated RHA/mild steel/ A1 7039 plate, we observed that spall had occured around the back face of A1 7039 plate by the stress wave interaction. Through the comparison between theoretical and experimental data including Lambert's results, we conform that our study has good confidences.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2011년도 추계학술대회 초록집
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• pp.81.2-81.2
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• 2011

The gas diffusion layer (GDL) consists of two main parts, the GDL backing layer, called as a substrate and the micro porous layer (MPL) coated on the GDBL. In this process, carbon particles of MPL penetrates to the GDBL consequently forms MPL penetration part. In this study, the micro porous layer (MPL) penetration thickness is determined as a design parameter of the GDL which affect pore size distribution profile through the GDL inducing different mass transfer characteristics. The pore size distribution and water permeability characteristics of the GDL are investigated and the cell performance is evaluated under fully/low humidification conditions. Transient response and voltage instability are also studied. In addition, to determine the effects of MPL penetration on the degradation, the carbon corrosion stress test is conducted. The GDL that have deep MPL penetration thickness shows better performance in high current density region because of enhanced water management, however, loss of penetrated MPL parts is shown after aging and it induces worse water management characteristics.

• Journal of the Korean Wood Science and Technology
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• 제47권5호
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• pp.579-586
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• 2019

This work examined effects of the synthesis method and melamine content of melamine-urea-formaldehyde (MUF) resins on the bond-line features (i.e. resin penetration and bond-line thickness) in plywood. Two synthesis methods (MUF-A and MUF-B) and three melamine contents (5, 10, and 20%) were employed to prepare MUF resins. The MUF-A resins at three melamine contents were prepared by a simultaneous reaction of melamine, urea, and formaldehyde, while the MFU-B resins were prepared by reacting melamine at the same levels with formaldehyde followed by urea. The results showed that higher melamine content increased the viscosity of MUF-A and MUF-B resins. The resin penetration of MUF-A resins decreased by 48% while those of MUF-B resins increased by 16% at 20% melamine content. As a result, the MUF-A resins had greater bond-line thickness than those of MUF-B resins as the melamine content increased. The MUF-B resins resulted in thinner bond-line and greater resin penetration compared to those of MUF-A resins. The results suggested that MUF-B resins prepared with 20% melamine content had a proper combination of resin penetration and bond-line thickness that could produce plywood panel with a better adhesion performance.

• Geomechanics and Engineering
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• 제9권6호
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• pp.743-755
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• 2015

It is well known that the quality of sample significantly determines the accuracy of soil parameters for laboratory testing. Although sampling disturbance has been studied over the last few decades, the theoretical investigation of soil disturbance due to sampling penetration has been rarely reported. In this paper, an analytical solution for estimating the soil disturbance due to sampling penetration was presented using cavity expansion method. Analytical results in several cases reveal that the soil at different location along the sample centerline experiences distinct phases of strain during the process of sampling penetration. The magnitude of induced strain is dependent on the position of the soil element within the sampler and the sampler geometry expressed as diameter-thickness ratio D/t and length-diameter ratio L/D. Effects of sampler features on soil disturbance were also studied. It is found that the induced maximum strain decreases exponentially with increasing diameter-thickness ratio, indicating that the sampling disturbance will reduce with increasing diameter or decreasing wall thickness of sampler. It is also found that a large length-diameter ratio does not necessarily reduce the disturbance. An optimal length-diameter ratio is suggested for the further design of improved sampler in this study.

• 대한기계학회논문집B
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• 제21권11호
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• pp.1458-1465
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• 1997

This study investigated the effects of pressure on the growth of an impinging spray. We obtained the frozen images which were scattered by Nd ; YAG laser light (pulse width : 7 ns) using synchronization circuit made in the laboratory. For an impinging spray a growth of the penetration length was progressed with increase of the injection pressure but an ambient pressure restrained its growth. The effect of an ambient pressure on penetration was larger than that of an injection pressure. The pressure ratio had an effect on the penetration growth rate. The thickness growth rate depended on both the injection pressure and the ambient pressure compositively. A lower injection pressure or a higher ambient pressure was required for spatial distribution of impinging spray.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2002년도 추계학술대회 논문집
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• pp.800-803
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• 2002

This investigation describes and analyses the experimental results proper to the penetration of Al5052-H34 alloy plates of thickness 6, 12 and 16mm(T/D＝1, 2, 3) by 5.56mm ball projectiles over the velocity range 350-750㎧. All the high velocity impact tests were carried out at normal impact angle, i.e. zero obliquity. The experimental results presented the variation of depth of penetration, bulge height and diameter, plugged length and diameter with the velocity fur tests on each plate of a given thickness in order to determine the deformation shapes of 5.56mm ball projectiles and targets. Also the protection ballistic limit($V_50$) tests were conducted.

• 한국철도학회논문집
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• 제19권4호
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• pp.506-514
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• 2016

철도 현장에 실험용 자갈궤도와 콘크리트궤도를 설치한 후 겨울철에 동결심도와 동상량을 측정하였다. 그 결과 같은 동결지수일 때 자갈궤도보다 콘크리트궤도의 동결심도가 깊게 나타나는 경향을 보였다. 또한 자갈궤도는 하부에 XPS, PE골재층을 포설할 경우 동결심도가 크게 감소하였고, 콘크리트궤도에서는 입도조정층의 두께를 늘릴 경우 동결심도가 감소하는 경향을 보였다. 동상량 역시 자갈궤도에서는 하부에 XPS, PE골재층을 설치할 경우 감소하였고, 콘크리트궤도에서는 입도조정층의 두께를 증가시킬 경우 감소하는 경향을 보였다.

• 한국기계기술학회지
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• 제20권6호
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• pp.858-864
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• 2018

Graphene oxide (GO) laminate is a new promising material for water purification system, which has extraordinary permeability only for water molecule. It consists of numerous nano-channels, in which water molecules could be nano-confined, resulting in slip of the molecules for very fast transportation speed. In this study, water penetration rate via different thickness of GO membrane according to driven pressures are measured experimentally, so that speed of water molecules and permeability are evaluated. Generally, water penetration rate via a membrane with macroscopic-sized channel increases linearly with pressure difference between up and bottom side of the membrane, but that via GO membrane approaches asymptotic value (i.e. saturation) as like a log function. Moreover, the permeability of GO membrane was observed in inverse proportion to its thickness. Based on the experimental observations, a correlation for volume flux via GO membrane was suggested with respect to its thickness and external pressure difference.

• Nuclear Engineering and Technology
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• 제35권2호
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• pp.144-153
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• 2003

The object of this paper is the probabilistic failure analysis on the cladding performance of WPF(Whole Pin Furnace) test fuel pins under transient conditions, and analysis of the KALIMER fuel pin using the preceding analysis. The cumulative damage estimation and Weibull probability estimation of WPF test are performed. The probabilistic method was adapted for these analyses to determine the effective thickness thinning due to eutectic penetration depth. In the results, it is difficult to assume that a brittle layer depth made by eutectic reaction is all of the thickness reduction due to cladding thinning. About 93% cladding thinning of the eutectic penetration depth is favorable as an effective thickness of cladding. And the unreliability of the KALIMER driver fuel pin under the same WPF test condition is lower than that of the WPF pin because of the higher plenum-fuel volume ratio and lower cladding inner radius vs. thickness ratio. KALIMER fuel pin developed from conceptual design has a more stable transient performance for a failure mechanism due to fission gas buildup than the WPF pin.

• 지질공학
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• 제26권1호
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• pp.143-152
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• 2016

토석류 지반의 안정성은 일반적으로 표토층의 중량, 점착력, 사면의 각도 그리고 내부 마찰각 등의 물성치를 통해서 예측된다. 그 중 표토층의 중량은 표토층 깊이와 단위중량으로 추정할 수 있으며, 이때 광범위한 지역에서 표토층 깊이를 예측하는 것이 선행적으로 필요하다. 본 연구에서는 탄성파 탐사를 통해 표토층 깊이를 추정하고자 하였으며, 표토층 깊이를 예측할 수 있는 속도 범위 결정방법도 함께 제시하고자 하였다. 대상지역은 세종시 인근의 토석류 발생지역으로 전체적인 표토층 깊이를 예측하기 위하여 총 4개의 측선에서 속도 분포를 관찰하였다. 또한 토석류 위험 지역에서의 표토층 깊이를 알기 위하여 동적 콘관입(dynamic cone penetration) 시험도 함께 실시하였으며, 총 18개의 원위치 시험을 수행하였다. 탄성파 탐사 결과 대상지역은 총 3~4개의 지층으로 구성되어 있으며, 기존의 속도값을 통해 표피심도를 예측하였다. 기존 속도 기준 값으로 예측된 결과는 DCP 결과와 큰 차이를 보였으며, 차이를 감소시키고 신뢰성을 높이기 위해 새로운 속도 기준값을 제시하였다. 이와 같은 결과는 표피심도를 예측하기 위하여 기존 기준 값을 현장 조건에 맞게 조절해야 함을 암시하며, 추가적인 실험으로 더욱 정밀한 기준값을 제시할 수 있을 것으로 사료된다.