• Journal of the Korean Ceramic Society
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• v.49 no.4
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• pp.287-294
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• 2012

Ceramic Matrix Composites (CMCs) represent a class of non-brittle refractory materials for harsh and extreme environments in aerospace and other applications. The quasi-ductility of these structural materials depends on the quality of the interface between the matrix and the fiber surface. In this study, a manufacture route is described where in contrast to most other processes no additional fiber coating is used to adjust the fiber/matrix interfaces in order to obtain damage tolerance and fracture toughness. Adapted microstructures of uncoated carbon fiber preforms were developed to permit the rapid infiltration of molten alloys and the subsequent reaction with the carbon matrix. Furthermore, any direct reaction between the melt and fibers was minimized. Using pure silicon as the reactive melt, C/SiC composites were manufactured with an aim of employing the resulting composite for friction applications. This paper describes the formation of the microstructure inside the C/C preform and resulting C/C-SiC composite, in addition to the MAX phases.

• Journal of Construction Engineering and Project Management
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• v.4 no.1
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• pp.37-44
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• 2014

Comparatively, the construction industry has, on average, a higher rate of fatal and major injuries, work induced ill-health and damage to properties than other industrial sectors; and this is a source of concern to industry stakeholders. The study showed that although subcontracting could be contributory to an increase in workplace accidents in the construction industry, contractual aspects of subcontracting arrangements (such as the power imbalance that exist along the client-customer interface) also present opportunities for improvements in health and safety management (HSM) practices in organisations. This conclusion was reached after an analysis of a questionnaire survey (with a 27% response rate) that assessed the attitudes and perception to health and safety issues.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.11a
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• pp.6-6
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• 2009

We present an alternative process whereby deuterium is delivered to the location where the gate oxide reside by an implantation process. Deuterium ions were implanted using different energies to account for the topography of the overlaying layers and placing the D peak at the top of gate oxide. A short anneal at forming gas was performed to remove the D-implantation damage. We have observed that deuterium ion implantation into the gate oxide region can successfully remove the interface states and the bulk defects.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2004.04a
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• pp.259-266
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• 2004

The vibration of slab causes a sudden change of air pressure in the interface between slab and air to create structure home sound. Floor impact noise induced from the vibration of slab became one of the hottest social issues in these day, and it took the biggest parts of the cause of damage in environmental dispute. Because the structure borne sound of slab is different from the dynamic characteristic of slab, it is required more precise vibroacaustic analysis. In this study, we was trying to understand by what mechanism the slab noise is induced from the slab vibration and the relationship between the dynamic propety of slab and the noise is shown by the numerical simulation.

• Journal of Industrial Technology
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• v.22 no.A
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• pp.3-8
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• 2002

In this study, extremely low cycle fatigue tests were carried out under push-pull loading conditions using graphite cast iron (GCD). In order to clarify the fatigue fracture mechanism of GCD in an extremely low cycle fatigue regime successive observations of internal fatigue damage were performed. The results obtained are as follows. (1) The process of extremely low cycle fatigue can be classified into three stages which are composed of the generation, growth and coalescence of microvoids inside materials. (2) In an extremely low cycle fatigue regime, microvoids originate from debonding of graphite-matrix interface.

• Computers and Concrete
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• v.14 no.6
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• pp.711-725
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• 2014

The purpose of this study is to evaluate the behavior and the strength of SRG (Steel Reinforced Grout) externally strengthened Reinforced Concrete (RC) beams by using a nonlinear numerical analysis. The numerical simulation was carried out by using a three-dimensional (3D) finite element model. An interface element with a suitable damage model was used to model the connection between concrete surface and SRG reinforcing layer. The reliability of the finite element 3D-model was checked using experimental data obtained on a set of three RC beams. The parameters taken into consideration were the external configuration, with or without U-end anchorages, the concrete strength, the amount of internal tensile steel reinforcement. Conclusions were made concerning the strength and the ductility of the strengthened beams by varying the parameters and on the effectiveness of the SRG reinforcing system applied with two types of external strengthening configuration.

• Magazine of the Korea Concrete Institute
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• v.9 no.5
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• pp.157-164
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• 1997

일반적으로 콘크리트와 철근간의 경계면을 나타내는 유한요소법에는 균열의 부근에서 발생하는 부착열화 현상을 고려하지 않고 있다. 이것은 균열 부근에서 과도한 부착을 초래하고 , 국소 변형과 균열의 진전에도 영향을 준다. 본 연구에서는 철근콘크리트 구조물의 균열부근에서 일어나는 부착거동의 변화를 고려한 비선형 부착응력-미끄럼 모델을 제안하였다. 철근과 콘크리트간의 경계면에는 링크요소를 이용하였고, 링크의 특성은 철근을 가로지르는 균열의 상태에 따라 변하도록 조정하였다. 균열의 형성상태를 정량화하고, 부착거동을 두 포락선 1) 균열로부터 충분히 떨어진 위치에서의 부착상태를 모델링한 외연포락선, 2)횡균열면에 있어서의 부착상태를 모델링한 내연포락선의 사이에 변이시키기 위하여 비국소적 손상도 개념을 도입하였다. 이 방법의 유효성을 알아보기 위하여 편재하중을 받는 T형 교각의 실험 및 해석결과를 제시하였다. 제안된 모델의 결과를 실험결과와 비교하여 본 모델의 유용성을 검증하였다.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2005.04a
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• pp.195-198
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• 2005

The role of elastic/plastic mismatch on the contact crack initiation is investigated for designing desirable surface-coated asymmetric layered composites. Various layered composites such as $Si_3N_4$ ceramics on $Si_3N_4+BN$ composite, soda-lime glass on various substrates with different elastic modulus for the analysis. Spherical indentation is conducted for producing contact cracks from the surface or interface between the coating and the substrate layer. A finite element analysis of the stress fields in the loaded layer composites enables a direct correlation between the damage patterns and the stress distributions. Implications of these conclusions concerning the design of asymmetric layered composites indicate that the elastic modulus mismatch is one of the important parameter for designing layered composite to prevent the initiation of contact cracks.

• Proceedings of the KSME Conference
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• 2004.11a
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• pp.297-301
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• 2004

The optimum design against contact crack initiation is investigated to find major parameters in designing desirable surface-coated asymmetric layered components. Hard ceramic coated soft materials with various elastic modulus mismatch are prepared for the analysis. Spherical indentation is conducted for producing contact cracks from the surface or interface between the coating and the substrate layer. A finite element analysis of the stress fields in the loaded layer components enables a direct correlation between the damage patterns and the stress distributions. Implications concerning the design of asymmetric layered components indicate that the coating thickness and the elastic modulus mismatch are important parameters for designing layered component to prevent the initiation of contact cracks.

• Proceedings of the KSME Conference
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• 2001.06c
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• pp.322-326
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• 2001

Hard disk drive(HDD) consists of a head/slider system which flies over the magnetic disk at an extremely low height. As the density of HDD increases the flying height of the head needs to be decreased. This increases the chance for contact between the slider and the disk. This paper addresses some key issues related to surface failure characteristics of HDD. It is shown that flying behavior of the slider during contact-start-stop cycle can be analyzed based on different regimes of air film lubrication, experimental methods for identifying the underlying mechanisms and improving the reliability of HDD are discussed.