• Restorative Dentistry and Endodontics
• /
• 제28권6호
• /
• pp.457-466
• /
• 2003

The aim of study was to investigate the effect of flow, specimen geometry and adhesion on the measurement of linear polymerization shrinkage of light cured composite resins using linear shrinkage measuring device. Four commercially available composites - an anterior posterior hybrid composite Z100, a posterior packable composite P60 and two flowable composites, Filtek flow and Tetric flow-were studied. The linear polymerization shrinkage of composites was determined using 'bonded disc method' and 'non-bond-ed' free shrinkage method at varying C-factor in the range of 1∼8 by changing specimen geometry. These measured linear shrinkage values were compared with free volumetric shrinkage values. The viscosity and flow of composites were determined and compared by measuring the dropping speed of metal rod under constant load. In non-bonded method, the linear shrinkage approximated one third of true volumetric shrink-age by isotropic contraction. However, in bonded disc method, as the bonded surface increased the linear shrinkage increased up to volumetric shrinkage value by anisotropic contraction. The linear shrinkage value increased with increasing C-factor and approximated true volumetric shrinkage and reached plateau at about C-factor 5∼6. The more flow the composite was, reduced linear shrinkage was measured by compensation radial flow.

• 터널과지하공간
• /
• 제14권5호
• /
• pp.363-372
• /
• 2004

구마모토 안산암을 대상으로 이중 비틀림(DT) 시험을 통해 유도 홈의 단면 형상이 암석의 응력부식지수에 미치는 영향에 대하여 조사하였다. 정변위속도법에서 변위속도가 증가할수록 균열성장속도는 증가하지만 파괴인성계수는 평균 2.07 MN/m$^{3}$2/로 거의 일정하였다. 정변위법을 통하여 유도 홈의 형상이 사각형, 원형, 삼각형인 시험편을 이용하여 얻은 응력부식지수는 각각 평균 37, 36, 38로 홈의 형상에 관계없이 거의 일정한 값을 보이지만 표준편차는 삼각형 홈에서 가장 크게 나타났다. 암석의 DT시험은 중앙부에 유도 홈이 있는 시험편을 이용하는 것이 효과적이지만 광물의 평균입경 이상의 폭을 가진 사각형 단면의 홈을 이용하는 것이 가장 적절하다.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2004년도 춘계학술대회
• /
• pp.60-65
• /
• 2004

Kim et al. described and compared other methods of measuring stress triaxiality using the displacements near the side necking, proved the validities of these models and explored the effect of location where the displacements are measured using three-dimensional finite element analysis for a standard CT specimen with 20% side-grooves. In this paper, the applicability of these models to various specimen and materials are examined in detail. To consider the effects of side groove, thickness of specimen, crack length, specimen geometry and strain hardening exponents, three-dimensional finite element simulation has been performed for various specimen geometries. For a case without a side groove, in the whole the difference between the stress triaxilaity analytically evaluated and directly determined is similar. For a case with a 20% side groove the stress triaxiality is measured at the area where ${\theta}$ is smaller than $60^{\circ}$, which excludes a side grooved area.

• 대한기계학회논문집
• /
• 제11권3호
• /
• pp.454-464
• /
• 1987

본 연구에서는 충격하중하에서 고변형도 .epsilon.=ln(h/h$_{o}$ )＞1.0, 고변형도율 (.epsilon.＞$10^{3}$m/s/m)로 변형하는 재료에 대하여 응력, 변형도, 변형도율사이의 함수관 계를 유도하고, 다음과 같은 현상들을 규명하였다. (1) 고변형도율에서 응력, 변형 도, 변형도율사이의 함수관계식 유도. (2) 압축하중시 시편과 접촉부재사이의 접촉면 에서 발생하는 마찰영향의 조사. (3) 유동응력과 시편의 기하학적 형상사이의 관계식 유도. (4) 압축하중시 재료의 제동현상(lock-up phenomena)의 해석.

• 한국공작기계학회:학술대회논문집
• /
• 한국공작기계학회 2004년도 추계학술대회 논문집
• /
• pp.225-232
• /
• 2004

Recently, there has been a rapid development in computer technology, which has in turn led to develop the automated welding system using Artificial Intelligence (AI). However, the automated welding system has not been achieved duo to difficulties of the control and sensor technologies. In this paper, the classification of the optimized bead geometry such as bead width, height penetration and bead area in the Gas Metal Arc (GMA) welding with fuzzy logic is presented. The fuzzy C-Means algorithm (FCM), which is best known an unsupervised fuzzy clustering algorithm is employed here to analysis the specimen of the bead geometry. Then the quality of the GMA welding can be classified by this fuzzy clustering technique and the choice for obtaining the optimal bead geometry can also be determined.

• 한국소성가공학회:학술대회논문집
• /
• 한국소성가공학회 1997년도 추계학술대회논문집
• /
• pp.158-163
• /
• 1997

In this paper the tool geometry of the PSS test were optimized in order to assure the reliability of the test. Considering many factors for optimization of the tool geometry, computer-simulation technique using three-dimensional finite element method(FEM) was used. Three design variables -the punch length, punch crown and punch corner radius- are chosen to be optimized according to the Taguchi's experiment technique with the L9 orthogonal array. The optimum condition to ensure the plane strain mode over the overall area of the specimen was clarified. Moreover the simulation results are confirmed by experiment.

• 대한기계학회논문집A
• /
• 제20권11호
• /
• pp.3415-3423
• /
• 1996

The compact tension specimen geometry has been widely used for measuring fatigue crack growth rates at elevated temperature when the fatigue load is under tension/tension condition. However, most of the elevated temperature components which have significant crack growth life experience fatigue load under tension/compression conditions. Thus test techniques are required since the compact tension specimen cannot be used for tension/compression loading. In this paper, a simplified test procedure for measureing fatigue crack growth rates is proposed, which employs a round bar specimen with a small surface crack. Fatigue crack growth rates under tension/ tension loading conditions at elevated temperature were measured according to the proposed procedure and compared with those previously measured by C/(T) specimens. Since both the measured crack growth rates were comparable, the fatigue crack growth rates under tension/ compression load can be reliably measured by the proposed procedure. For monitoring crack depth. DC electric potential method is employed and an optimal probe location and current input conditions were proposed.

• 한국마린엔지니어링학회:학술대회논문집
• /
• 한국마린엔지니어링학회 2000년도 추계학술대회 논문집(Proceeding of the KOSME 2000 Autumn Annual Meeting)
• /
• pp.15-20
• /
• 2000

Filament winding process is a comparatively simple operation in which continuous reinforcements in the form of roving are wound over a rotating mandrel. And it is now well established as a versatile method for storage tanks and pipe for the chemical and other industries. In this study, tensile strength of a filament wound ring specimens were evaluated by split disk test fixture and dress disk test fixture. The results obtained from experiments were compared with the theoretical values obtained by the rule of mixtures in composites . And the purpose of this paper is the suggestion of an appropriate test method for the evaluation of tensile properties of filament wound structures. The tensile strength of a ring specimen tested by the dress disk test showed better agreement with the theoretical values than that of a ring specimen tested by the split disk test because the stress concentration in edges of a split disk test fixture is more severe than that of dress disk test fixture. The results showed that the tensile strength of a ring specimen was influenced by the geometry of test fixture, the continuity of fibers, fiber-tension, fiber-end and stress concentration in specimen.

• 한국복합재료학회:학술대회논문집
• /
• 한국복합재료학회 2000년도 추계학술발표대회 논문집
• /
• pp.203-207
• /
• 2000

Filament Winding Process is a comparatively simple operation in which continuous reinforcements in the form of roving are wound over a rotating mandrel. And now well established as a versatile method for storage tanks and pipe for the chemical and other industries . In this study, tensile strength of a filament wound ring specimens were evaluated by split disk test fixture and dress disk test fixture , The results obtained from experiments were compared with the theoretical values obtained by the rule of mixtures. And the purpose of this paper is the suggestion of an appropriate test method for the evaluation of tensile properties of filament wound structures .The tensile strength of a ring specimen tested by the dress disk test showed better agreement with the theoretical values than of a ring specimen tested by the split disk test because the stress concentration in edges of a split disk test fixture is more severe than that of dress disk test fixture. The results showed that the tensile strength of a ring specimen was influenced by the geometry of test fixture, the continuity of fibers, fiber-tension, fiber-end and stress concentration in specimen.

• 한국윤활학회:학술대회논문집
• /
• 한국윤활학회 2002년도 proceedings of the second asia international conference on tribology
• /
• pp.367-368
• /
• 2002

The design of capsule body for self-propelled endoscope is important from the frictional resistance point of view. The capsule should be able to overcome the frictional resistance in order to move along the intestine. The motivation of this work was to gain a better understanding of the capsule body design on the frictional resistance of the capsule inside an intestine. A special experimental set-up was built to measure the frictional resistance as the capsule was being pulled inside the pig intestine specimen. Tests were performed with open and closed intestine specimens. Experimental data showed that smooth cylindrical capsule geometry resulted in the least frictional resistance. The resistance inside the closed intestine specimen was about four times higher than that of the open specimen. It is expected that the results of this work will be used to design the optimum propulsion system for the microendoscope.