• Proceedings of the Materials Research Society of Korea Conference
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• 2012.05a
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• pp.104.1-104.1
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• 2012

타이타늄(Ti)은 비강도가 높고, 내식성이 우수하여 항공기, 자동차 및 선박과 같은 수송기기의 소재로 사용되고 있다. 이러한 특성을 가진 타이타늄을 이종소재와 결합하여 더 우수한 기계적 특성을 얻을 수 있다면, 그 응용범위를 확대할 수 있을 것이다. 본 연구에서는 타이타늄과 알루미늄(Al) 판재를 적층한 후, 열간압연을 통해 타이타늄/알루미늄 적층재를 제조하였다. 이와 같은 적층재를 다양한 압하율로 냉간 압연한 후 미세조직을 관찰하였으며, 인장시험을 통해 기계적 특성을 조사하였다. 아울러 타이타늄 판재만으로도 유사한 실험을 실시하여 기계적 특성을 적층재와 비교 평가하였다.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.29 no.2 s.233
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• pp.284-292
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• 2005

Material flaws in the from of pre-existing defects can severely affect the crack initiation. Stress distribution and crack initiation life of engineering materials such as monolithic aluminum alloy and Al/Glass fiber laminate may be different according to the defect location. The aim of this study is to evaluate effects of relative location of defects around the circular hole in monolithic aluminum and Al/Glass fiber laminates under cyclic bending moment. Stress distribution and crack initiation behavior near a circular hole are considered. Results of Finite Element (FE) model indicated the features of different stress field due to the relative defects positions. Especially, the defects positions at ${\theta}=0^{\circ}\;and\;{\theta}=30^{\circ}$ was strongly effective in stress concentration factor ($K_t$) and crack initiation behavior.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.05a
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• pp.76-76
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• 2004

하이브리드 복합재료 중에서 적충형태의 Al/GFRP는 단일재 알루미늄에 비해 피로특성, 비강도, 비강성 등이 매우 우수하여 Fig. 1과 같이 항공기 주익 구조에 주로 적용된다. 그러나 이러한 Al/GFRP 적층재 역시 장시간에 걸쳐 비행하중을 받게 되면 다양한 형태의 파손이 발생할 수 있다. 이 중 알루미늄층과 섬유층 사이에서 발생하는 층간분리는 Al/GFRP 적층재의 대표적인 피로파손 형태이며, 현재 이러한 파손은 다 방면으로 연구되고 있다.(중략)

• Proceedings of the KSR Conference
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• 2010.06a
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• pp.1486-1491
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• 2010

Recently, the frequency and magnitude of the earthquake have increased. The structural safety of the public facilities such as bridges and tunnels etc. which were not concerned for earthquake resistant design are increased. Fiber reinforcement polymer that has been frequently studied for seismic retrofit has advantage as seismic reinforcement material, but it has disadvantage of the brittleness. Therefore, the investigation of safety and seismic reinforcement are required. In this study, new FRP-ductile material layered composites proposed to seismic performance reinforced of subway tunnel. Tensile test of FRP-ductile material layered composites showed that Maximum tensile force of FRP-ductile using Aluminum is similar to existing FRP reinforcement material and maximum strain was increased. In case of application of domestic subway tunnel which need ductility, layered composites of FRP-Aluminum is estimated effectively for increase of seismic performance.

• Journal of the Korean Society for Nondestructive Testing
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• v.31 no.1
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• pp.53-61
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• 2011

Edge notched A16061-T6 aluminum was repaired with a GFRP composite patch as a function of the number of stacking, Damage progress of specimen for tension load has been monitored by acoustic emission(AE), AE energy rate, hit rate, amplitude, waveform and 1st peak frequency distribution were analyzed. Fracture processes were classified into Al cracking, Fiber breakage, Resin cracking and Delamination. Displacement of a specimen can be divided into Region I, II and ill according to acoustic emission characteristics. Region II where the patch itself was actually fractured was focused on to clarify the AE characteristics difference for the number of stacking.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.35 no.5
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• pp.567-574
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• 2011

Aluminum extruded panels are widely used instead of corrugated steel panels for weight reduction in high-speed trains. Of the layers in the train body, it makes the largest contribution to the sound insulation. However, compared with that of a flat panel with the same weight, the TL of the aluminum extruded panel is remarkably lower in the local resonance frequency band. We study aluminum extruded panels for next-generation 400-km/h trains. We investigate the problem of sound insulation and propose a practical method to improve the sound-insulation performance. The local resonance frequency region is increased by a modification of the core structure, and urethane foam is placed in the core. The effect on the sound insulation is verified by experiments. Finally, the improvement for the entire sound-transmission loss is estimated for the layered floor panels of express trains.

• Proceedings of the KSME Conference
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• 2001.11a
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• pp.278-285
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• 2001

Aluminum/Aramid Fiber Reinforced Plastic(Al/AFRP) laminates are applied to the fuselage-wing intersection. The main objective of this study was to evaluate the delamination zone behavior of Al/AFRP with a saw-cut and circular hole using average stress criterion and the effect of notch geometry. Mechanical tests were carried out to determine the cyclic-bending moment and delamination zone observed ultrasonic C-scan pictures. In case of Al/AFRP containing saw-cut specimen, the shape and size of the delamination zone formed along the fatigue crack. However, in case of Al/AFRP containing circular hole specimen, the shape and size of delamination zone formed two types. first type, delamination zone formed along the fatigue crack. Second type, not observed fatigue crack. Therefore, delamination zone was formed dependently of the circular hole shape.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.31 no.3 s.258
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• pp.344-354
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• 2007

The objective of this study is to investigate the effect of arbitrarily located defect around the circular hole in the aircraft structural material such as Al/GFRP laminates and monolithic Al alloy sheet under cyclic bending moment. The fatigue behavior of these materials may be different due to the defect location. Material flaws in the from of pre-existing defects can severely affect the fatigue crack initiation and propagation behavior. The aim of this study is to evaluate effects of relative location of defects around the circular hole in monolithic Al alloy and Al/GFRP laminates under cyclic bending moment. The fatigue behavior i.e., the stress concentration factor($K_t$), the crack initiation life($N_i$), the relationship between crack length(a) and cycles(N), the relationship between crack growth rate(da/dN) and stress intensity factor range(${\Dalta}K$) near a circular hole are considered. Especially, the defects location at ${\theta}_1=0^{\circ}\;and\;{\theta}_2=30^{\circ}$ was strongly effective in stress concentration factor($K_t$) and crack initiation life($N_i$). The test results indicated the features of different fatigue crack propagation behavior and the different growing delamination shape according to each location of defect around the circular hole in Al/GFRP laminates.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 1998.10a
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• pp.19-19
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• 1998

라이너를 포함한 필라멘트 와인딩 복합재 압력용기의 성능향상을 위한 효율적인 구조최적 설계방안을 제시하였다. 이를 위해 온도효과가 고려된 비선형 유한요소법을 이용하여 각 층에서의 응력해석과 파손해석을 수행하였다. 또한 설계변수로 라이너의 두께와 헬리컬 적층두께, 실린더를 따라 변하는 직각 적층두께를 설정하였다. 모든 설계변수들에 대한 강도비 민감도를 유도하였으며 헬리컬 적층두께에 대한 강도비 민감도를 유지하기 위해 측지 등장력 돔설계 방법을 고려하였다. 구조 최적설계결과, 실린더를 따라 직각 적층두께를 최적으로 분포시켜 강성을 효과적으로 배열하였으므로 적층두께를 일정하게 고려한 경우보다 더 경량화 시킬 수 있었다.

• Journal of the Korean Society for Railway
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• v.15 no.4
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• pp.315-322
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• 2012

In a tunnel, interior noise of a high speed train increases by 5dB~7dB. The reason is that the sound intensity of the acoustic field in the tunnel significantly increases by the reflected waves occurred in the closed space. Especially, the incident acoustic power largely increases on the outside of the compartment side panel and large transmission of noise is available through the side panel and the glass window. In this paper, the sound insulation strategy in the tunnel is proposed for the next generation high speed train under development. Specimens of the aluminum extruded panels, layered panels and double glazed window are manufactured and intensity transmission loss is measured according to ASTM E2249-02. Based on the measured data, problems in the sound insulation performance are diagnosed and the sound insulation strategy is reviewed on each panel and layered structures.