• 한국섬유공학회:학술대회논문집
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• 한국섬유공학회 1987년도 학술발표초록집
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• pp.11-11
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• 1987

Among other poly(4,4'-terephthanilidealkylamide)s (PTAA's), poly (4,4'-terephthanilideadipamide) (PTAd) gave clear critical concentration curves. For PTAA's with methylene units more than 6, the critical concentration (C*) seemed to be beyond the solubility limit of H₂SO₄. Under shearing conditions, the nematic domains were easily oriented and stretched in the direction of shear , and a fibrillar structure resulted. At low frequencies, a monotollous reduction of loss tangent (tan) was observed as concentration increased. At high frequencies, however, tan was increased above C* again, and showed maximum at saturation concentration (Cs). With increasing temperature, viscosity of isotropic and anisotropic phases was normally decreased, while viscosity of biphases was increased. Plot of complex viscosity (If) against temperature based on rheological measurements exhibited a good correlation with phase diagram constructed by polarizing microscope observations. Rheological parameters suggested the optimum dope concentration of PTAd with inherent viscosity 2.02 at 30oc is in the vicinity of 19.2 wt%, which seemed to agree well with spinning experiments (around 19.4 wt%). In general, effects of spinning and annealing conditions on the mechanical properties of PTAA fibres were most pronounced in PTAd fibre spun from anisotropic spinning dope .

• 반도체디스플레이기술학회지
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• 제18권3호
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• pp.133-139
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• 2019

The utilizations of ceramics in the modern industries are increasing due to the desirable combinations of electrical, mechanical and physical properties found in ceramics. Ceramic materials are brittle, hard, strong in compression, weak in shearing and tension which is prone to affect the defects such as scratch, crack and breakage during the machining. Generally, the defects of the ceramic machining are generated from the structural vibrations of the machine. In this study, the dynamic characteristics of a machining center for ceramic machining were investigated to analyze the structural vibrations for the improved stability. Frequency response test and computer simulation have been conducted for the analysis and the design improvement. The improved design is suggested to suppress vibrations for the higher stability of the machine and further to reduce vibrations. And the result shows that simple design alterations without any change of major parts of the machine can reduce the vibration of the machine effectively.

• Advances in materials Research
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• 제5권2호
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• pp.107-120
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• 2016

The static analysis of the simply supported functionally graded plate under transverse load by using a new sinusoidal shear deformation theory based on the neutral surface concept is investigated analytically in the present paper. No transversal shear correction factors are needed because a correct representation of the transversal shearing strain is given. The mechanical properties of the FGM plate are assumed to vary continuously through the thickness according to a power law formulation except Poisson's ratio, which is kept constant. The equilibrium and stability equations are derived by employing the principle of virtual work. Results are provided for thick to thin plates and for different values of the gradient index k, which subjected to sinusoidal or uniformly distributed lateral loads. The accuracy of the present results is verified by comparing it with finite element solution. From the obtained results, it can be concluded that the proposed theory is accurate and efficient in predicting the displacements and stresses of functionally graded plates.

• 한국의류학회지
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• 제31권1호
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• pp.77-84
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• 2007

The purpose of this study was to investigate and to compare the performances of silicone laminated materials sold for swimming cap in market, to get the basic data for product development. We selected 4 specimens and tested their air permeability, waterproofness and breathability. We also tested the physical and mechanical properties of the specimens using KES system. Silicone-laminated material was not bursted on high hydraulic pressure since silicone membrane gave waterproofness while PU/Polyester substrate gave elasticity. It didn't have air permeability and breathability at all. Any toxic materials such as Formaldehyde, Deldrin, PCP, Amin, TDBPP were not detected in silicone-laminated material and other materials. Silicone-laminated material had higher stretchability with the low force but it had lower elastic recovery and shape stability comparing to PU laminated material. It had lower flexibility than PU laminated material. It had lower unrecoverable amount in shearing direction. Friction coefficient was higher in silicone-laminated material than PU laminated material due to its surface stickiness. It was compressed easily and its compression resiliency was higher with compared to PU laminated material.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2005년도 추계학술대회 논문집
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• pp.627-631
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• 2005

In this study, low fatigue behavior of laser welded sheet metal were investigated. Before welding, the cross section of butt joint was prepared only by fine shearing without milling process. Specimens were same sheet metal and welding condition that using automobile manufacturing company at present. Butt joint of cold rolled sheet metal was welded by $CO_2$ laser. It is used that welding condition such as laser welding speed was 5.5m/sec and laser output power was 5kW for 0.8mm and 1.2mm sheet metal. The laser weldments were machined same or different thickness and same or different material. In order to mechanical properties of around welding zone, hardness test was performed. Hardness of welding bead is about 2 times greater than base material. We performed the low cycle fatigue tests for obtaining fatigue properties about thickness and the weld line direction of specimen. The results of strain controlled low cycle fatigue test indicate that all specimens occur cyclic softening, as indicated by the decrease in stress to reach a prescribed strain.

• Geomechanics and Engineering
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• 제11권6호
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• pp.787-803
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• 2016

DDARF (Discontinuous Deformation Analysis for Rock Failure) is a numerical algorithm for simulating jointed rock masses' discontinuous deformation. While its reinforcement simulation is only limited to end-anchorage bolt, which is assumed to be a linear spring simply. Here, several new reinforcement modes in DDARF are proposed, including lining reinforcement, full-length anchorage bolt and equivalent reinforcement. In the numerical simulation, lining part is assigned higher mechanical strength than surrounding rock masses, it may include multiple virtual joints or not, depending on projects. There must be no embedding or stretching between lining blocks and surrounding blocks. To realize simulation of the full-length anchorage bolt, at every discontinuity passed through the bolt, a set of normal and tangential spring needs to be added along the bolt's axial and tangential direction. Thus, bolt's axial force, shearing force and full-length anchorage effect are all realized synchronously. And, failure criterions of anchorage effect are established for different failure modes. In the meantime, from the perspective of improving surrounding rock masses' overall strength, a new equivalent and tentative simulation method is proposed, it can save calculation storage and improve efficiency. Along the text, simulation algorithms and applications of these new reinforcement modes in DDARF are given.

• 방사성폐기물학회지
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• 제20권2호
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• pp.209-229
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• 2022

This work provided a review of three techniques-(1) spectrochemical, (2) electrochemical, and (3) spectroelectrochemical-for molten salt medias. A spectroelectrochemical system was designed by utilizing this information. Here, we designed a spectroelectrochemical cell (SEC) and calibrated temperature controllers, and performed initial tests to explore the system's capability limit. There were several issues and a redesign of the cell was accomplished. The modification of the design allowed us to assemble, align the system with the light sources, and successfully transferred the setup inside a controlled environment. A preliminary run was executed to obtain transmission and absorption background of NaCl-CaCl₂ salt at 600℃. It shows that the quartz cuvette has high transmittance effects across all wavelengths and there were lower transmittance effects at the lower wavelength in the molten salt media. Despite a successful initial run, the quartz vessel was mated to the inner cavity of the SEC body. Moreover, there was shearing in the patch cord which resulted in damage to the fiber optic cable, deterioration of the SEC, corrosion in the connection of the cell body, and fiber optic damage. The next generation of the SEC should attach a high temperature fiber optic patch cords without introducing internal mechanical stress to the patch cord body. In addition, MACOR should be used as the cell body materials to prevent corrosion of the surface and avoid the mating issue and a use of an adapter from a manufacturer that combines the free beam to a fiber optic cable should be incorporated in the future design.

• Geomechanics and Engineering
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• 제37권6호
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• pp.615-627
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• 2024

Direct simple shear test is an effective method to measure strength and deformation properties of soil. However, existing direct simple shear apparatus have some shortcomings. The paper has developed a novel dual stress/strain-controlled direct simple shear apparatus. The novel apparatus has the following advantages: A rectangular specimen is used that effectively avoid common issues associated with conventional cylindrical specimens, such as specimen tilting. The utilization of deformation control rods ensures a uniform shear deformation of the specimen. Vertically integrated force transmission structure is improved that avoids issues arising from changes in pivot points due to lever tilting. Incorporating this novel direct simple shear apparatus, shear strength and shear creep tests of clay were performed. Shear strength parameters and shear creep behaviors are analyzed. The results of these experiments show that the novel apparatus can measure accurately the shear rheological properties of soil. This study provides strong guidance for studying the mechanical properties of soil in engineering practice.

• 한국의류학회지
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• 제20권6호
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• pp.975-982
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• 1996

This study was conducted to examine the fatigue phenomenon of mechanical properites in denim fabrics for slacks during repeated shear and tensile deformation by analysing the change in the basic dynamic properties of fabrics on the basic of experiments to obtain the basic data necessary to measure their fatigue. In addition, this study was carried out by allowing these denim fabrics at market to go through the repeated deformation under such different loads as 500 gf/cm2 and 1000 gf/cm2 by using a simulated fatigue tester, by calculating both dynamic properties and hand value (HV) of these fabrics with KES-F system and then by obtaining the THV through these calculated properties. The results are as follows: 1 The fatigue phenomenon of dynamic properties was remarkably shown by the repeated shear and tensile deformation, while the increase of hysterical plastic substances was also remarkable in these shearing and bending properties. 2. The elasticity values of tensile, bending and compression properties, such as, B and G were reduced: whereas RT and RC values increased. It was shown, then, that those fabrics lost their elasticity and became flexible and soft with the increase of fatigue. 3. The fatigue phenomenon of hand value also showed that those fabrics became soft in relation with the change of all dynamic properties, and that their performance was also change to flexible hand value. 4. TRhe degree of fatigue was also shown by the loads given to the repeated deformation. It was shown that the fatigue was higher for the tensile load of 1000 gf/cm3 than did the standard load of 500 gf/cm3 It is necessary, therefore, to consider the load in accordance with their usage when examining the fatigue phenomenon with respect to the dynamic properties of clothing materials. 5. The loads were nearly not influenced by the change in the general hand value tended to show a little of increase with the increase of fatigue, Based on those results, it seems that the fatigue phenomonon is related to the loads given to the repeated deformation.

• 터널과지하공간
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• 제26권2호
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• pp.68-86
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• 2016

암반 구조물의 안정성을 분석하기 위해서는 암반 내 존재하는 불연속면의 전단거동 특성을 파악하는 것이 필수적이다. 특히 심부 지하에서의 암석 불연속면 마찰 거동 특성은 역학적, 수리적, 열적 및 화학적 조건과 각각의 조건들의 상호작용에 의해 영향을 받게 된다. 본 연구에서는 다양한 열-수리-역학적 조건에서 불연속면의 전단 거동 특성을 파악하기 위해 매끈한 화강암 불연속면 시험편과 거칠기를 포함한 유사암석 불연속면 시험편을 대상으로 삼축압축장비를 이용한 전단실험을 수행하였다. Coulomb의 전단강도 예측식을 이용하여 실험결과를 분석한 바 화강암 시험편의 경우 실험 조건의 변화에 따라 마찰 거동에 큰 변화를 보이지 않았으나 유사암석 시험편의 경우 응력 수준에 따라 변화를 보였다. 실험 조건의 변화에 따른 강성 및 팽창각의 변화를 분석한 결과 온도 및 수압 조건의 변화에 따라서 크게 변화하지 않음을 알 수 있었다.