• 선박안전
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• 제12권
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• pp.36-43
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• 2003

Fatigue life estimation by the theoretical stress concentration factors are, in general, considerably different from test results. And in calculating stress concentration factor, it is very difficult to consider actual geometry and material property which are the notch shapes, imperfections or defects of materials such as porosities inclusions and casting defects, etc. Therefore, the paper deals with the experimental method to find out the more exact stress concentration factors by measuring the strain distributions on each specimen by 3D-ESPI(Electronic Speckle Pattern Interferometry) System. Then the fatigue lives are compared between theoretical calculations using stress concentration factors determined by 3D-ESPI system and fatigue test results

• 한국경영과학회:학술대회논문집
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• 대한산업공학회/한국경영과학회 1995년도 춘계공동학술대회논문집; 전남대학교; 28-29 Apr. 1995
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• pp.677-677
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• 1995

• 한국농업기계학회:학술대회논문집
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• 한국농업기계학회 1998년도 동계 학술대회 논문집
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• pp.36-41
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• 1998

• 한국항공우주학회지
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• 제32권8호
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• pp.91-100
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• 2004

경사기능재료 판에 대한 열탄성 변형과 응력 해석을 위해 Green 함수 방법이 채택되었다. 3 차원 비정상 온도분포에 대한 해는 적층판 이론에 의해 얻어진다. 열탄성 문제에 대한 기본 방정식은 각각 평면외 (out-plane) 변형과 평면내 (in-plane) 힘에 의해 유도되었다. 굽힘과 평면내 힘에 의한 열탄성 변형과 응력분포는 Galerkin 방법에 근거한 Green 함수를 이용하여 해석하였다. 열탄성 변형과 응력분포 해석을 위한 Galerkin Green 함수의 특성함수들은 사각판의 제차 경계조건을 만족시키는 허용함수들의 급수 형태로 근사화되었다. 단수지시된 사각 판에 대한 수치해석이 수행되었으며, 정사기능재료의 물성치가 판의 비정상 열탄성 거동에 미치는 영향이 검토되었다.

• 한국안전학회지
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• 제20권2호
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• pp.26-31
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• 2005

The strong continuous fiber reinforced metal matrix composites (MMCs) are recently used in aerospace and transportation applications as an advanced material due to its high strength and light weight. Unidirectional fiber-metal matrix composites have superior mechanical properties along the longitudinal direction. However, the applicability of continuous fiber reinforced MMCs is somewhat limited due to their relatively poor transverse properties. Therefore, the transverse properties of MMCs are significantly influenced by the properties of the fiber/matrix interface. In order to be able to utilize these MMCs effectively and with safety, it must be determined their elastic plastic behaviors at the interface. In this study, the interfacial stress states of transversely loaded unidirectional fiber reinforced metal matrix composites investigated by using elastic-plastic finite element analysis. Different fiber volume fractions $(5-60\%)$ were studied numerically. The interlace was treated as three thin layer (with different properties) with a finite thickness between the fiber and the matrix. The fiber is modeled as transversely isotropic linear-elastic, and the matrix as isotropic elastic-plastic material. Using proposed model, the effects of the interface region and fiber arrangement in MMCs on the distributions of stress and strain are evaluated. The stress distributions of a thin multi layer interface have much less changes compared with conventional perfect interface. The analyses were based on a two-dimensional generalized plane strain model of a cross-section of an unidirectional composite by the ANSYS finite element analysis code.

• 한국방재학회 논문집
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• 제2권3호
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• pp.101-108
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• 2002

다양한 공법으로 널리 시공되고 있는 프리스트레스트 콘크리트(PSC) 연속 교량의 단면에는 시공이 음이 발생하게 된다. 이러한 시공이음부에서 연속적인 프리스트레스 하중을 도입하기 위해서는 텐던을 겹침이음(overlapping)하거나 텐던 커플러를 사용하는 방법이 사용되며, 후자의 경우는 시공이 음의 정착부 배근의 단순화와 효율적으로 텐던을 사용할 수 있는 장점이 있다. 본 연구의 목적은 텐던 커플러를 사용한 PSC 교량의 시공이음부의 종방향 응력 분포를 규명하는 데 있으며, 이를 위해 텐던 연속과 단면의 분할 시공 효과를 고려한 실험과 유한요소 해석을 수행하였다 연구결과 텐던 커플러를 사용한 시공이음부의 응력 상태는 텐던 커플러를 사용하지 않은 경우에 비해 종방향 응력상태와 다르게 나타나고 있다. 특히 구조적으로 문제가 되는 종방향 압축응력은 시공이음부에서 텐던 연결비율이 증가함에 따라 크게 감소한다.

• Tribology and Lubricants
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• 제37권6호
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• pp.240-245
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• 2021

Ceramic coatings with high hardness and excellent chemical stability have been successfully applied to various machine elements, tools, and implants. However, in the case of monolayer coating on soft substrates, a high-stress concentration at the interface between the coating and the substrate causes delamination of the coating layer. Recently, to overcome this problem, multilayer coatings with a metal layer with a low modulus of elasticity added between the ceramic and the substrate have been widely applied. This study presents the third part of a recent study and focuses on the effect of the number of coating layers on the Brinell hardness of multilayered coating with TiN/Ti, following the two previous studies on a new Brinell hardness test method for a coated surface and on the influence of substrate and coating thickness. Indentation analyses are performed using finite element analysis software, von Mises stress and equivalent plastic strain distributions, load-displacement curves, and residual indentation shapes are presented. The number of TiN/Ti layers considerably affect the stress distributions and indentation shapes. Moreover, the greater the number of TiN/Ti layers, the higher is the Brinell hardness. The stress and plastic strain distributions confirm that the multilayer coatings improve the wear resistance. The results are expected to be used to design and evaluate various coating systems, and additional study is required.

• 품질경영학회지
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• 제27권3호
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• pp.79-93
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• 1999

The common accelerated life test(ALT) consists of test methods applying a constant stress, higher than the use condition stress, to items. There we, however, situations for which a progressive stress ALT, in which the stress on a test item is continuously increased with time, Is more convenient to perform testing and simpler in analyzing data than a constant stress ALT. When a product under constant stress s follows a Weibull distribution with parameters $\theta$(5) and $\beta$, maximum likelihood(ML) estimators of parameters involved in the model are obtained and their asymptotic distributions are derived under stress bounded ramp tests in which the stress is increased linearly from use condition stress to the stress upper bound. The optimum test plans are also found which minimize the asymptotic variance of the ML estimator of the log mean life at design constant stress. For selected values of the design parameters, tables useful for finding optimal test plans are given. The effect of the pre-estimates of design parameters is studied.

• Journal of Welding and Joining
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• 제4권2호
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• pp.30-39
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• 1986

In manufacturing of pipe walls for boiler units, distortion can result in pipe-web-pipe joints from the nonuniform expansion and contraction of the weld metal and the adjacent base metal during heating and cooling cycle of the welding process. In this study, the stresses and strains during longitudinal welding of the plate-to-pipe joint were investigated. Using the method of successive elastic solution, longitudinal stresses and strains during and after welding were calculated from the information of temperature distributions obtained by Rosenthal's equations. In order to confirm the validity of the numerical results, the temperature and residual stress distributions were measured and compared with the calculated results. In spite of some assumptions, the one-dimensional analytical results of residual stresses were in fairly good agreement with the experimental ones. The residual stresses due to welding of plate-to-pipe joints are tensile near the weld line and compressive in the base metal as in the welding of plates. the amount and distribution of residual stresses were deeply dependent on the heat input ratio of the plate and pipe.

• 대한한의학회지
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• 제24권1호
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• pp.155-168
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• 2003

This study was carried out to investigate the effect of Keuibi-tang (KBT) on the injury of gastric mucous membrane by stress and ethanol in mice. The normal group was non-inflammation elicited mice. The two control groups were mice with gastro-inflammation elicited by stress and ethanol. The two sample groups were mice administered KBT before gastro-inflammation elicitation. In the common morphology and histochemical change, the two control groups were observed with various injuries such as hemorrhagic erosion and ulcer, while the sample group was the same as the normal group. In the immunohistochemical change, the distributions of PNA and COX-1 treated with KBT noticeably increased over the control group (P<0.05). The distributions of $NF-{\kappa}B$ p50, COX-2 and TUNEL in the group treated with KBT were noticeably lower than in the control group (P<0.05). The distribution of KBT was the same as the normal group. According to the above results, it is supposed that KBT is applicable to gastritis and gastric ulcer due to stress and alcoholic drinks.