• 한국정밀공학회지
• /
• 제16권10호
• /
• pp.152-163
• /
• 1999

The problem of eigenvalue and eigenvector for v-notched cracks in pseudo-isotropic and anisotropic dissimilar materials was obtained to discuss stress singularities from traction free boundary and perfect bonded interface conditions assuming like the form of complex stress function for v-notched cracks in an isotropic material. Eigenvalues were solved by a commercial numerical program, MATHEMATICA. The relation between wedged angle and material property for eigenvalue, ${\lambda}$ indicating stress singularities of v-notched cracks in pseudo-isotropic and anisotropic dissimilar materials was examined.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2004년도 추계학술대회
• /
• pp.400-403
• /
• 2004

We present a coarse-graining model to describe the mechanical behaviors of multi-walled carbon nanotubes. To find the atomic configuration in membrane-like nanostructure i.e. carbon nanotube, we employ interpolation functions and the associated element-variables that are defined in the subdivided region. Tersoff-Brenner potential is adopted for interaction of bonded atoms and also van der Waals force for non-bonded interaction. Moreover, we simulate the coarse-graining multi-walled carbon nanotubes with defects and its result is compared with that of perfect multi-walled carbon nanotubes.

• Structural Engineering and Mechanics
• /
• 제56권2호
• /
• pp.275-291
• /
• 2015

Adherence between reinforcement and the surrounding concrete is usually ignored in finite element analysis (FEA) of reinforced concrete (RC) members. However, load transition between the reinforcement and surrounding concrete effects RC members' behavior a great deal. In this study, the effects of bond-slip on the FEA of RC members are examined. In the analyses, three types of bond-slip modeling methods (perfect bond, contact elements and spring elements) and three types of reinforcement modeling methods (smeared, one dimensional line and three dimensional solid elements) were used. Bond-slip behavior between the reinforcement and surrounding concrete was simulated with cohesive zone materials (CZM) for the first time. The bond-slip relationship was identified experimentally using a beam bending test as suggested by RILEM. The results obtained from FEA were compared with the results of four RC beams that were tested experimentally. Results showed that, in FE analyses, because of the perfect bond occurrence between the reinforcement and surrounding concrete, unrealistic strains occurred in the longitudinal reinforcement. This situation greatly affected the load deflection relationship because the longitudinal reinforcements dominated the failure mode. In addition to the spring elements, the combination of a bonded contact option with CZM also gave closer results to the experimental models. However, modeling of the bond-slip relationship with a contact element was quite difficult and time consuming. Therefore bond-slip modeling is more suitable with spring elements.

• Structural Engineering and Mechanics
• /
• 제32권5호
• /
• pp.649-665
• /
• 2009

This paper reports part of a comprehensive research study conducted at the University of Queensland on the ability of CFRP web-bonded systems in strengthening an exterior beam-column joint subjected to monotonic loads. One 1/2.2 scaled plain and four CFRP repaired/retrofitted joints subjected to monotonic loads were analysed using the nonlinear finite-element program ANSYS and the results were calibrated against experiments. The ANSYS model was employed in order to account for tension stiffening in concrete after cracking and a modified version of the Hognestad's model was used to model the concrete compressive strength. The stress-strain properties of main steel bars were modelled using multilinear isotropic hardening model and the FRPs were modelled as anisotropic materials. A perfect bond was assumed as nodes were shared between adjacent elements irrespective of their type. Good agreement between the numerical predictions and the experimental observation of the failure mechanisms for all specimens were observed. Closeness of these results proved that the numerical analysis can be used by design engineers for the analysis of web-bonded FRP strengthened beam-column joints with confidence.

• 비파괴검사학회지
• /
• 제26권5호
• /
• pp.343-352
• /
• 2006

본 논문에서는 금속 연소관, 단열 고무 그리고 내열 복합재로 구성된 연소관 조립체의 접착 체결 상태를 확인하기 위해 변형률, 음향방출 신호 그리고 초음파 시험자료를 이용한 비파괴 시험 방법이 제시되었다. 또한 내압 상태에서 연소관 조립체의 각 계면 접착 상태를 정량적으로 평가하기 위해 유한요소 해석이 수행되었다. 공압 시험 중 계측한 변형률 값과 음향방출 신호 상관관계 연구를 통해 연소관 조립체의 접착 건전성 평가가 가능했다. 그리고 연소관 조립체의 여러 접착 계면 중 첫 번째 계면인 연소관과 고무간의 접착은 초음파 방법으로 분류하였다. 이러한 연구를 통해 연소관 조립체의 모든 접착 계면은 1) 초기 완전 미접착, 2) 공압 시험 중 완전 접착 분리, 3) 공압 시험 중 부분 접착 분리, 4) 완전 접착 등 4가지 형태로 분류 및 검출되었다.

• International Journal of Precision Engineering and Manufacturing
• /
• 제3권2호
• /
• pp.33-44
• /
• 2002

The problem of eigenvalues and eigenvectors is obtained from a v-notched crack in pseudo-isotropic dissimilar materials by the traction free boundary and the perfect bonded conditions at interface. The complex stress function of the two-term William's type is used. The eigenvalues are solved by a commercial numerical program, MATHEMATICA. Stress singularities for v-notched cracks in pseudo-isotropic dissimilar materials are discussed. The RWCIM(Reciprocal Work Contour Integral Method) is applied to the determination of eigenvector coefficients associated with eigenvalues with egenvalues. The RWCIM algorithm is also coded by the MATHEMATICA.

• 보존과학연구
• /
• 통권7호
• /
• pp.48-55
• /
• 1986

The gold crown unearthed from the ancient tombs at Imdang-dong, Kyongsan-gun, Kyongsangbuk-do was in a state of severe corrosion that its original pattern couldn't be identified. Therefore, for the conservation of the relics, the following methods are employed :1. With 10% formic acid are used for the elimination of the bronze-rust and then plated them with gold.2. As a rust-proof treatment, 1% Benzotriazole is used for stem corrosion as well3. For protection and reinforcement of the surface of the relics, 30% incralac agentsare used.4. Pieces of fragments are bonded together by cyanoacrylate and on the backside are coated partially with Araldite for the reinforcement of the glass-wool.5. Silica-gels are kept into the acryl box for perfect maintenance.

• 대한기계학회논문집
• /
• 제16권8호
• /
• pp.1513-1518
• /
• 1992

본 연구에서는 참고문헌 8의 해법을 응용하여 다발 보의 마찰 접촉 문제를 푸는 방법에 대하여 설명한다. 각 보 요소의 변형은 미소변형 및 Bernoulli-Euler이 론을 이용하여 계산하며, 마찰력 계산을 위하여는 Coulomb 마찰 법칙을 이용한다. 보의 종류와 형상 및 보를 묶는 클램프(clamp)의 종류에 따라서 수 많은 종류의 스프 링이 얻어 질 수 있다. 여기에서는 편의상 보 다발이 클램프에 의하여 강하게 묶여 있으며, 그 묶인 점에서는 각 보의 법선 방향(normal direction) 상대 운동은 없는 것 으로 간주한다.

• 한국정밀공학회지
• /
• 제17권11호
• /
• pp.129-139
• /
• 2000

The problem of eigenvalue and eigenvector is obtained from a V-notched crack in pseudo-isotropic dissimilar materials by the traction free boundary and the perfect bonded interface conditions. The complex stress function is assumed as the two-term William's type. The eigenvalue is solved by a commercial numerical program, MATHEMATICA to discuss stress singularities for V-notched cracks in pseudo-isotropic dissimilar materials. The RWCIM(Reciprocal Work Contour Integral Method) is applied to the determination to eigenvector coefficients associated with eigenvalues. The RWCIM algorithm is also coded by the MATHEMATICA.

• Advances in nano research
• /
• 제12권4호
• /
• pp.405-414
• /
• 2022

In this study, the elastic plane problem of a layered composite containing an internal or edge crack perpendicular to its boundaries in its lower layer is examined using numerical analysis. The layered composite consists of two elastic layers having different elastic constants and heights. Two bonded layers rest on a homogeneous elastic half plane and are pressed by a rigid cylindrical stamp. In this context, the Finite Element Method (FEM) based software called ANSYS is used for numerical solutions. The problem is solved under the assumptions that the contacts are frictionless, and the effect of gravity force is neglected. A comparison is made with analytical results in the literature to verify the model created and the results obtained. It was found that the results obtained from analytical formulation were in perfect agreements with the FEM study. The numerical results for the stress-intensity factor (SIF) are obtained for various dimensionless quantities related to the geometric and material parameters. Consequently, the effects of these parameters on the stress-intensity factor are discussed. If the FEM analysis is used correctly, it can be an efficient alternative method to the analytical solutions that need time.