• Proceedings of the KSME Conference
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• 2000.11b
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• pp.162-167
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• 2000

Soot formation and oxidation is closely related to the combustion phenomena inside a diesel engine. Laser-based diagnostics provide a means for improving our understanding of diesel combustion, because they have highly temporal and spatial ability. To understand the soot behavior we did preliminary study by taking flame luminosity photographs and 2-D imaging soot distribution using Laser Elastic Scattering(LIS) and Laser-Induced Incandescence(LII). From the data we found that soot concentration was high in the bowl and disappeared from the central region in the late combustion stage.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2007.11a
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• pp.379-380
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• 2007

• Asia-pacific Journal of Multimedia Services Convergent with Art, Humanities, and Sociology
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• v.7 no.2
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• pp.437-444
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• 2017

Stress concentrations around discontinuities, such as a hole in cross section of a structural member, have great importance because the most materials failure around the region may be occurred. Stress on the point applied by concentrated load reaches much larger value than the average stress in structural member. In this paper, stress analysis was performed for the plate with a partial through-hole to find the difference of the principal stress distribution. The difference between maximum principal stress and minimum principal stress in photoelasticity is equal to the value obtained by multiplying the isochromatic fringe order by the fringe constant of the material divided by the distance through which the light passes, that is, the thickness of the specimen. Since the difference of principal stress is proportional to the photoelastic fringe order, the distribution of the principal stress difference by the finite element analysis can be compared with the photoelasticity experimental result. ANSYS Workbench, that is the finite element software, is used to compute the differences of principal stresses at the specific points on the measured lines. The computation values obtained by ANSYS are compared with the experimental measurements by photoelasticity, and two results are comparable to each other. In addition, the stress concentration factor is obtained using the stress distribution analyzed from the variation of hole depth. Stress concentration factor is increasing, as the depth of hole increase.

• Polymer(Korea)
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• v.35 no.1
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• pp.1-6
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• 2011

Pressurized high temperature plastic resin flows into the cavity of mold and is solidified in injection molding process. Residual stress is being developed in injection molded part because of high temperature variations and high pressure. Developed residual stress relaxes as time goes. Consequently this makes part deformed and deteriorates quality of product. A measurement method of residual stress for injection molded transparent articles has been investigated using photoelasticity. Light, a composite of electromagnetic waves, is purified into a single wave by a polarized film. When this wave passes through the specimen, birefringence is developed according to the level of residual stress in the specimen and color fringed pattern appears after the second polarized film. Residual stress in the injection molded transparent flat a part has been measured quantitatively using the color fringed pattern. Optical characteristics have been a part also predicted by computer simulation and compared with experimental results.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.36 no.3
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• pp.471-491
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• 2016

Traditional limit equilibrium method needs an assumption of the failure surface to calculate the bearing capapcity of the shallow foundation. From the viewpoint of the mechanics of granular materials, however, the failure of the soil mass is initated by the local buckling of the contact force chains. In this study we observed the directional distribution of the contact force chains in the granular assembly stacked by model particles subjected to the model shallow foundation during loading. Two sets of the assemblies with a regular structure and initially local imperfection were prepared for tests. Existence of the initial local imperfection has a significant effect on the directional distribution of the contact force chains. The bearing capacity of the assembly with local imperfection is only 67% the capacity of the assembly with the regular structure.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2000.04a
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• pp.34-34
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• 2000

재료에 따라 기계적 특성들은 하중속도에 의존하는 경우가 많다. 이런 기계적 특성들 중 파괴인성은 기계구조물을 파괴 역학적으로 안전하게 설계하는 경우뿐만 아니라, 운전되고 있는 기계 건전성의 측면에서 매우 중요한 파라미터이다. 또한 파괴인성은 작용하는 하중의 속도에 따라 정적파괴인성($K_{IC}$)과 동적파괴인성($K_{ID}$)으로 구분하고 이들의 측정 방법과 인성의 크기 또한 매우 상이하다. 동적파괴인성의 평가방법으로는 광탄성법, 모아레법 및 스트레인게이법을 이용한 충격실험방법들이 이용되고 있다.

• Proceedings of the KIEE Conference
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• 2008.04a
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• pp.133-134
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• 2008

우리나라의 당뇨병 유병률은 경제발전과 식생활의 급속한 서구화로 빠른 속도로 증가하고 있다. 특히 당뇨병은 유병기간이 길수록 여러 합병증을 초래하는데 그 중 하나가 혈관경화증이다. 혈관 경화증은 신체 부위별로 그 진행 속도가 다르다. 광혈류측정법(PPG, photoplethysmogram)은 간편한 혈류량 측정방법으로 PPG 2차 미분 방법을 이용해서 혈관의 경화도를 진단할 수 있다. 이러한 PPG 2차 미분방법을 이용하여 당뇨병환자의 왼손과 오른손의 말초혈관 탄성도 차이를 정상인과 비교해 보았다. 실험결과 당뇨병환자와 정상인의 양 손가자 말초혈관 탄성도의 유의한 차이를 확인 할 수 있었다.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.44 no.9
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• pp.769-774
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• 2016

Epoxy polymer exposed to solar radiation on long-term is required to a long-term environmental test in order to ensure the reliability of operation performance. In this paper, the solar aging experiment is performed for 7, 14, 28, 56, and 84 cycles, using solar simulator designed according to MIL-STD-810. After the aging experiment, measuring RGB values and using the CIE1976 color space, each RGB decreasing rates and total color shift are calculated. In addition, using a universal testing machine, mechnical properties according to ASTM-D638 are measured. As a result, by increasing solar aging period, total color shift is increased, and the tensile strength and elongation are decreased, but the elastic modulus and the poisson's ratio are slightly changed.

• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.4
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• pp.723-736
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• 1992

Most degeneating diseases and back pains in the orthopaedic disease are originated from the unbalance of stress distribution in the low-lumbar spine. Therefore the stress analysis of lowerback is indispensible to the clinical diagnosis for the developing reason and the developing process of diseases. Therefore the same model materials as following are eveloped to analyze the stress distributions of lower-back by photoelastic experiment. The verterbral body and the process are molded from epoxy resin(the weight ratio of Araldite and hardner is 10 to 3), models are geometrically identical to them in vivo respectively and the ratio of their elastic modulus to that of model material is 1 to 10. It is assured that KE-1300 Silicon(E=0.8MPa), TSE-3562 Silicon(0.5MPa) and the composite silicon(3MPa) (the weight ratio of KE-1300 silicon and Jioreal : 10 to 4) are respectively effective as the model materials of ligament, musles and intervertevral disc which is essential to the movement of low-lumbar spine. All the elements associated with the movement of the low-lumbar spine are molded through the molding method developed in this research and assembled with the angles between the verterbra and the disc in the normal human lumbosacral spine. The stress distributions of the assembled model are analyzed by photoelastic experiment. It is certified by comparing the results of photoelastic experimebt with the clinical situations that the loading dveice and the loading conceptions used in this paper are effective.

• Transactions of the Korean Society of Mechanical Engineers
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• v.15 no.2
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• pp.424-435
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• 1991

To develop the photoelastic experiment method for the orthotropic material under pure torsional moment is the main objective of this research. In the development of photoelastic experiment for orthotropic material under pure torsional moment, the important problems and their solutions are the same as following. In the model material for photoelastic experiment, it was found that C.F.E.C.(Copper Fiber Epoxy Composite) can be used as the model material of photoelastic experiment for orthotropic material. In the stress freezing cycle, it was assured that stress freezing cycle for epoxy can be used as the stress freezing cycle of the photoelastic experiment for orthotropic material. In the slicing method, it was found that the negative oblique slicing method can be effectively used as slicing method in 3-dimensional photoelastic experiment. In the measuring method of stress fringe values and physical properties in the high temperature, it was found that stress fringe values can be directly measured by experiment and physical properties can be directly or indirectly by equation between stress fringe values and physical properties developed by author. In the stress analysis method of orthotropic material under pure torsional moment by photoelastic experiment, it will be studied in the second paper.