• 한국전산구조공학회논문집
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• 제33권3호
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• pp.179-186
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• 2020

본 연구에서는 복부대동맥류가 발생한 환자들에서의 연령과 복부대동맥류 형상에 따른 벽 응력과 파열 위험성을 평가하였다. 복부대동맥류의 형상은 의료영상 데이터로부터 추출되어 모사되었으며, 재료 물성치 단계에서는 동맥 조직의 이방성 초탄성 성질을 모사하기 위해 Gasser-Ogden-Holzapfel 모델을 적용하였다. 또한, 모델에서 필요한 각 재료 정수들은 환자들의 연령과 정상 조직 및 동맥류 조직의 특성들을 고려하기 위하여 각기 다른 값들로 산정되었다. 게다가 복부대동맥류에서의 대동맥 직경과 목의 각도에 관한 상관관계를 분석하고, 이에 대한 시리즈 시뮬레이션 역시 수행되었다. 그 결과, 복부대동맥류 환자의 연령과 대동맥 직경, 그리고 대동맥 목의 각도에 따른 복부대동맥류의 파열 위험성이 평가되었다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2000년도 제18회 학술발표회 논문개요집
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• pp.163-163
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• 2000

In this research, we used the ion irradiation technique which has an advantae in improving intentionally the properties of surface and interface in a non-equilibrium, instead of the conventional annealing method which has been known to improve the material properties in the equilibrium stat. Cu/Co multilayered films were prepared on SiN4/SiO2/Si substrates by the electron-beam evaporation for the Co layers and the thermal evaporation for the Cu layers in a high vacuum. The ion irradiation with a 80keV Ar+ was carried out at various ion doses in a high vacuum. Hysteresis loops of the films were investigated by magneto-optical polar Kerr spectroscopy at various experimental conditions. The change of atomic structure of the films before and after the ion irradiation was studied by glancing angle x-ray diffraction, and the intermixing between Co and Cu sublayers was confirmed by Rutherford backscattering spectroscopy. The surface roughness and magneto-resistance were measured by atomic force microscopy and with a four-point probe system, respectively. During the magneto-resistance measurement, we changed temperature and the direction of magnetization. From the results of experiments, we found that the change at the interfaces of the Cu/Co multilayered film induced by ion irradiation cause the change of magnetic properties. According to the change in hysteresis loop, the surface inplane component of magnetic easy axis was isotropic before the ion irradiation, but became anisotropic upon irradiation. It was confirmed that this change influences the axial behavior of magneto-resistance. Especially, the magneto-resistance varied in accordance with an external magnetic field and the direction of current, which means that magneto-resistance also shows the uniaxial behavior.

• Geomechanics and Engineering
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• 제4권4호
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• pp.251-262
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• 2012

Triaxial tests are essential to estimate the shear strength properties of the soil or rock. Normally triaxial tests are carried out on samples of 38 mm diameter and 76 mm height. Granular materials, predominantly used in base/sub-base construction of pavements or in railways have size range of 60-75 mm. Determination of shear strength parameters of those materials can be made possible only through triaxial tests on large diameter samples. This paper describes a large diameter cyclic triaxial testing facility set up in the Geotechnical Engineering lab of Indian Institute of Science. This setup consists of 100 kN capacity dynamic loading frame, which facilitates testing of samples of up to 300 mm diameter and 600 mm height. The loading ram can be actuated up to a maximum frequency of 10 Hz, with maximum amplitude of 100 mm. The setup is capable of carrying out static as well as dynamic triaxial tests under isotropic, anisotropic conditions with a maximum confining pressure of 1 MPa. Working with this setup is a difficult task because of the size of the sample. In this paper, a detailed discussion on the various problems encountered during the initial testing using the equipment, the ideas and solutions adopted to solve them are presented. Pilot experiments on granular sub-base material of 53 mm down size are also presented.

• 소성∙가공
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• 제23권4호
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• pp.199-205
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• 2014

The current study examines the effect of the analytical parameter values on the theoretical forming limit diagram (FLD) based on the Marciniak-Kuczynski model (M-K model). Tensile tests were performed to obtain stress-strain curves and determine the anisotropic properties in the rolling, transverse and diagonal direction of SPCC sheet materials. The experimental forming limit curve for SPCC sheet material was obtained by limiting dome stretching tests. To predict the theoretical FLD based on the M-K model, the Hosford 79 yield function was employed. The effects of three analytical parameters - the exponent of the yield function, the initial imperfection parameter and the fracture criterion parameter - on the M-K model, were examined and the results of the theoretical FLD were compared to the experimentally measured FLD. It was found that the various analytical parameters should be carefully considered to reasonably predict the theoretical FLD. The comparison of the acceptable forming limit area between the theoretical and experimental FLD is used to compare the two diagrams.

• Journal of the Korean Wood Science and Technology
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• 제42권5호
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• pp.499-509
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• 2014

Wood filler is a porous and anisotropic material having different size, shape, and aspect ratio. The use of wood fillers such as wood particle, wood flour, and wood pulp in wood plastic composites (WPCs) are growing rapidly because these wood fillers give improved strength and stiffness to WPCs. However, the wood fillers have originally poor compatibility with plastic matrix affecting the mechanical properties of WPCs. Therefore, to improve compatibility between wood and plastic, numbers of physical and chemical treatments were investigated. While the various treatments led to improved performances in WPC industries using petroleum-based plastics, full biodegradation is still issues due to increased environmental concerns. Hence, bio-based plastics such as polylactide and polyhydroxybutyrate having biodegradable characteristics are being applied to WPCs, but relatively expensive prices of existing bio-based plastics prevent further uses. As conventional processing methods, extrusion, injection, and compression moldings have been used in WPC industries, but to apply WPCs to engineered or structural places, new processing methods should be developed. As one system, co-extrusion technique was introduced to WPCs and the co-extruded WPCs having core-shell structures make the extended applications of WPCs possible.

• 한국지반공학회논문집
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• 제20권7호
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• pp.207-215
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• 2004

본 연구는 보강사면에 상계이론를 적용하여 실제 한계상태에 가까운 신뢰성이 높은 해석방법을 개발하는데 목적이 있으며 상계해석의 유한요소공식화를 전개하는데 있어 거시적인 관점으로부터 비등방성이면서 균질한 재료에 대한 수치해석의 기본 개념은 얻을 수 있다. 보강토는 뒷채움한 성토와 보강재 경계면의 상호작용으로 보강토의 강도가 보강재의 재료적 특성에 의존하고 있기 때문에 흙의 역학적 특성과 보강토의 전체 거동은 보강재의 기하학적인 배열과 상대적인 면적에 의해서 조절할 수 있다. 따라서, 상계이론은 보강사면의 한계상태 거동을 효과적으로 산정할 수 있어 국부적으로 발생하는 소성파괴를 예측할 수 있다.

• 한국생산제조학회지
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• 제19권2호
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• pp.235-240
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• 2010

The recent trend of vehicle design aims at crash safety and environmentally-friendly aspect. For the crash safety aspect, energy absorbing members should be absorbed with collision energy sufficiently. But vehicle structure must be light weight for the environmentally-friendly aspect, in order to improve fuel efficiency and to reduce tail gas emission. Therefore, the light weight of vehicle must be achieved in a status of securing safety of crash. An aluminum or CFRP (Carbon Fiber Reinforced Plastics) is representative one among the light-weight materials. In this study, impact collapse behavior of circular hybrid thin-walled member is evaluated. The hybrid members are manufactured by wrapping CFRP prepreg sheets outside the aluminum circular members in the autoclave. Because the CFRP is an anisotropic material whose mechanical properties change with its stacking condition, special attention is given to the effects of the stacking condition on the collapse behavior evaluation of the hybrid thin-walled member. Collapse mode and energy absorption capability of the hybrid thin-walled member are analyzed with change of the fiber orientation angle and interface number.

• 패션비즈니스
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• 제7권3호
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• pp.60-70
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• 2003

Textile scientists have regarded the material appearance of natural fibers, especially that of silk or wool fibers, as the benchmark for reinventing the look and feel of the long term, friendly companion of mankind. The appearances or textures of the materials surrounding us in everyday life have long been interesting topics to many people.from scholars to painters. Even the simplest questions may require careful pondering. Why is the silk fabric so lustrous with subtlety? Recently, appearance models have become increasingly important in textile products. They are needed to model and simulate different models. In this study, the optical characteristics of filament yarns and knitted fabrics were investigated using images taken at various angles and illumination conditions. Then the images were analyzed using some image analysis techniques, such as thresholding and measuring luster blobs. The anisotropic nature of the filamentous specimens was studied based on the images acquired at different incident illumination and observing angles with several alignment positions of the fabric specimens. A few cylindrical models were generated using commercially available software, Rhinoceros, and then on the models, a ray-tracing algorithm based on a software, POV-Ray, was applied to simulate the appearance or lustrous images of the monofilament models.

• ETRI Journal
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• 제38권6호
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• pp.1163-1171
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• 2016

Integration technologies involving flexible substrates are receiving significant attention owing the appearance of new products regarding wearable and Internet of Things technologies. There has been a continuous demand from the industry for a reliable bonding method applicable to a low-temperature process and flexible substrates. Up to now, however, an anisotropic conductive film (ACF) has been predominantly used in applications involving flexible substrates; we therefore suggest low-temperature lead-free soldering and bonding processes as a possible alternative for flex-on-flex applications. Test vehicles were designed on polyimide flexible substrates (FPCBs) to measure the contact resistances. Solder bumping was carried out using a solder-on-pad process with Solder Bump Maker based on Sn58Bi for low-temperature applications. In addition, thermocompression bonding of FPCBs was successfully demonstrated within the temperature of $150^{\circ}C$ using a newly developed fluxing underfill material with fluxing and curing capabilities at low temperature. The same FPCBs were bonded using commercially available ACFs in order to compare the joint properties with those of a joint formed using solder and an underfill. Both of the interconnections formed with Sn58Bi and ACF were examined through a contact resistance measurement, an $85^{\circ}C$ and 85% reliability test, and an SEM cross-sectional analysis.

• Advances in concrete construction
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• 제3권2호
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• pp.127-143
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• 2015

Steel fibre reinforced concrete (SFRC) is an anisotropic material due to the random orientation of the fibres within the cement matrix. Fibres under different inclination angles provide different strength contribution of a given crack width. For that the pull-out response of inclined fibres is of great importance to understand SFRC behaviour, particularly in the case of fibres with hooked ends, which are the most widely used. The paper focuses on the numerical modelling of the pull-out response of this kind of fibres from high-strength cementitious matrix in order to study the effects of different inclination angles of the fibres to the load-displacement pull-out curves. The pull-out of the fibres is studied by means of accurate three-dimensional finite element models, which take into account the nonlinearities that are present in the physical model, such as the nonlinear bonding between the fibre and the matrix in the early stages of the loading, the unilateral contact between the fibre and the matrix, the friction at the contact areas, the plastification of the steel fibre and the plastification and cracking of the cementitious matrix. The bonding properties of the fibre-matrix interface considered in the numerical model are based on experimental results of pull-out tests on straight fibres.