• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 춘계학술대회
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• pp.273-278
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• 2003

Recently, high-performance hybrid composite materials have been used for various industrial fields because of their superior high strength, high stiffness and lower weight. In this study, manufactured hybrid composite materials are composed of two parts. One is hard-anodized Al5083-O alloy as a face material and the other is high strength aramid fiber ($Twaron^{(R)}$ CT709) laminates as a back-up material. Resistance to penetration is determined by protection ballistic limit($V_{50}$, a static velocity with 50% probability for complete penetration) test method. $V_{50}$ tests with $0^{\circ}$obliquity at room temperature were conducted with 5.56mm ball projectiles that were able to achieve near or complete penetration during high velocity impact tests.

• 한국구조물진단유지관리공학회 논문집
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• 제23권4호
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• pp.86-95
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• 2019

탄소섬유는 경량이면서 높은 기계적 특성 때문에 우주항공, 선박, 자동차, 토목 및 건축과 같은 산업분야에서 그 어느 때 보다 더 광범위하게 적용되고 있다. 본 연구는 섬유혼입률 및 섬유길이 변화에 따른 탄소섬유 보강시멘트 복합재료( CFRC)의 역학적 특성과 휨 거동을 분석하였으며, 또한 자연 낙하시험에 의한 모르타르 시편에 대한 내충격성을 비교, 검토하였다. 더불어, 탄소섬유(CF)의 혼입률은 0.5%, 1.0%, 2.0% 및 3.0%로 변화를 주었으며, 각각의 섬유길이는 6 mm와 12 mm를 사용 하였다. 실험결과, 플로우 값은 탄소섬유의 뭉침현상으로 인해 유동성 측면에서 매우 불리하였으며, 단위용적질량은 다소 감소하였다. 특히, 압축강도는 탄소섬유 혼입량이 증가함에 따라 감소하는 것으로 나타내었다. 반면 휨 강도는 섬유 길이가 12 mm이고 2% 혼입한 것이 가장 높은 휨 강도를 보였다. 내충격성 시험결과, 보통 모르타르 시편은 완전파괴까지의 낙하횟수가 2~3회 정도 걸리지만 반면 CFRC 시편은 섬유혼입량이 증가함에 따라 다소 차이가 있지만, 섬유길이가 12 mm이고 섬유혼입량 2% 인 경우 충격에 대한 저항성이 가장 높았다.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2015년도 추계 학술논문 발표대회
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• pp.36-37
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• 2015

Recently, there has been a rapid increase in demand for lightweight walls for their use as interior partitions, as types of structure have gradually changed from shear wall structures to column structures or flat plate column wall systems. The lack of resisting force in lightweight walls is found by measuring the depth of dents in impact resistance tests, but it is not a direct factor of impact resistance. However, in the user's position, dents of over a certain size are clearly a factor that visually reminds the need for repair. In this study, we reviewed relative methods of assessment of the need for repair based on the visual means of determination (sensory test) on the dents on lightweight walls. Dents were found to stand out starting from depths of about 4mm, and the depth of roughly 5mm was found to be the criterion for determining the necessity of repair for men, while it was 4mm for women.

• 정보저장시스템학회논문집
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• 제9권2호
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• pp.56-61
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• 2013

The recent increased use of mobile phone has resulted in a technical focusing on reliability issues related to drop performance. Since mobile phone may be dropped several times during their use, it is required to survive common drop accidents. The plastic injection parts such as base stopper and carrier in the encoder type actuator can be broken easily in the actual reliability test of 1.5m free drop. So, we analyzed the shock resistance characteristics of auto focus actuator with variables in the material properties using finite element method. By applying the new resin materials, we can decrease the breakage of plastic injection parts and improve the reliability of mobile phone.

• 대한치과보철학회지
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• 제32권3호
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• pp.411-430
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• 1994

The denture may be fractured accidentally by an impact while outside the mouth, or may be cracked or broken while in service in the mouth. The latter is generally a fatigue failure caused by repeated flexure over a period of time. This investigation compared the flexural fatigue resistance, the impact force and the transverse strength of two denture base materials with and without the grid strengthener, the T300, the T800 and the Kevlar fiber to evaluate the fracture resistance. The distribution and behavior of fibers across fracture lines were examined by Hi-Scope Compact Microvision System. Through analyses of the data from this study, the following conclusions were obtained. 1. The flexural fatigue resistance, impact strength and transverse strength of high impact strength resin were higher than those of conventional heat polymerizing resin, but statistically there was no significant difference(p>0.05). 2. All specimens with and without the grid strengthener did not show significant differences in the flexural fatigue, the impact and the transverse strength test(p>0.05). 3. All specimens reinforced with the T300, the T800 and the Kevlar fiber showed significant increase of the fatigue resistance and the impact force(p<0.05). 4. All specimens reinforced with the T800 and the Kevlar fiber showed significant increase of the transverse strength(p<0.05). 5. All specimens reinforced with the T300, the T800 and the Kevlar fiber exhibited greenstick fractures. The fibers tended to remain enveloped in the resin, resisting pull-out.

• 한국지반환경공학회 논문집
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• 제11권12호
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• pp.13-18
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• 2010

본 연구는 최근 개발된 실리카졸 그라우팅재의 환경영향성 및 내구성을 규명한 것으로써 연구에 사용된 그라우트재는 3차원 겔 형성재인 실리카졸 그라우팅제와 규산나트륨 그라우팅제에 대한 공학적 특성을 비교하기 위하여 전자현미경 촬영, 내화학성시험, 용탈시험, 투수시험 등을 통해 친환경성과 내구성을 규명하고자 하였다. 전자현미경 촬영 결과 실리카졸 그라우팅제의 표면 및 내부조직이 규산나트륨보다 치밀함을 확인할 수 있었다. 용탈시험 결과 용탈되는 원소의 총량도 극히 작아 친환경적인 재료임을 입증되어 지반주입재로써 적용성을 확인하였다. 투수시험 결과 실리카졸이 차수성면에서 현장에 적용하는데 무리가 없다고 판단되어 차수성을 요구하는 현장에 적용이 가능하다고 판단된다.

• Steel and Composite Structures
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• 제46권3호
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• pp.345-352
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• 2023

A thermal-mechanical coupling finite element model of the steel-plate concrete composite (SC) wall is established, taking into account the strain rate effect and variation in mechanical and thermal properties under different temperatures. Verifications of the model against previous fire test and impact test results are carried out. The impact response of the SC wall under elevated temperatures is further investigated. The influences of the fire exposure time on the impact force and displacement histories are discussed. The results show that as the fire exposure time increases, the deflection increases and the impact resistance decreases. A formula is proposed to calculate the reduction of the allowable impact energy considering the fire exposure time.

• 한국안전학회지
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• 제30권3호
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• pp.7-12
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• 2015

CFRP composites are used as primary structural members in various industrial fields because their specific strength and specific stiffness are excellent in comparison to conventional metals. Their usage is expanding to high added-value industrial fields because they are more than 50% lighter than metals, and have excellent heat resistance and wear resistance. However, when CFRP composites suffer impact damage, destruction of fiber and interface delamination occur. This causes an unexpected deterioration of strength, and for this reason it is very difficult to ensure the reliability of the excellent mechanical properties. Therefore, for the destruction mechanism in bending with impact damage, this study investigated the reinforcement data regarding various external loads by identifying the consequential strength deterioration. Specimens were damaged by impact with a steel ball propelled by air pressure. Decrease in bending strength caused by the tension and compression of the impact side, and depending on the lamination direction of fiber and interface inside the specimen. From the bending test it was found that the bending strength reduced when the impact energy increased. Especially in the case of compression on the impact side, as tensile stress occurred at the damage starting point, causing rapid failure and a substantially reduced failure strength.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제52권6호
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• pp.286-290
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• 2003

The high temperature superconducting bulk can be used as the bearing of induction motors. This paper presents the fabrication and test results of an induction motor with superconducting bearings using HTS bulks. The bearing had eight hexahedron type YBCO bulks. Height, width and thickness of the HTS bulk were 30mm, 30mm and 10mm, respectively. Single phase induction motor was used to drive the shaft made of aluminum and the rotor of a conventional induction motor. To estimate the performance of the HTS bulk magnetic bearing, no load test, load test and Impact test were carried out. Load tests were performed by using air resistance caused by the shaft-mounted thin cylinder with buckets. Impact tests by axial direction and vertical direction impact showed that the vibration of the shaft gradually decayed. The induction motor with HTS bulk magnetic bearing rotated silently and smoothly throughout the tests. According to the test results, conventional bearings can be replaced with superconducting magnetic bearings made of HTS bulks.

• 한국정밀공학회지
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• 제20권3호
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• pp.178-186
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• 2003

In order to investigate the fracture behaviors (penetration modes) and the resistance to penetration during ballistic impact of Al 5052-H34 alloy laminates, cold-rolled Al 5052-H34 alloy laminates, anodized Al 5052-H34 alloy laminates, and anodized Al 5052-H34 alloy after cold-rolling, a ballistic testing was conducted. In general, superior armor materials are brittle materials which have a high hardness. Ballistic resistance of these materials was measured by a protection ballistic limit (V$_{50}$), a statistical velocity with 50% probability fur incompletete penetration. Fracture begaviors and ballistic tolerance, described by penetration modes, ate observed from the results from the results of V$_{50}$ test and Projectile Through Plates (PTP) test at velocities greater than V$_{50}$, respectively. PTP tests were conducted with 0$_{\circ}$obliquity at room temperature using 5.56mm ball projectile. V$_{50}$ tests with 0$_{\circ}$obliquity at room temperature were concucted with projectiles that could achieve neat or complete penetration during PTP tests. Surface hardness, resistance to penetration, and penetration modes of Al 5052-H34 alloy laminates are compared to those of cold-rolled Al 5052-H34 alloy laminates and anodized Al 5052-H34 alloy laminates and anodized Al 5052-H34 cold-rolled alloy.