• Smart Structures and Systems
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• v.5 no.6
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• pp.633-644
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• 2009

A simple method has been developed to detect the bonding condition of active fiber composites (AFC) adhered to the surface of a host structure. Large deformation actuating capability is one of important features of AFC. Edge delamination in adhesive layer due to large interfacial shear stress at the free edge is typically resulted from axial strain mismatch between bonded materials. AFC patch possesses very good flexibility and toughness. When an AFC patch is partially delaminated from host structure, there remains sensing capability in the debonded part. The debonding size can be determined through axial resonance measured by the interdigitated electrodes symmetrically aligned on opposite surfaces of the patch. The electrical impedance and modal response of the AFC patch in part adhered to an aluminum plate were investigated in a broad frequency range. Debonding ratio of the AFC patch is in inverse proportion to the resonant frequency of the fundamental mode. Feasibility of in-situ detecting the progressive delamination between AFC patch and host plate is demonstrated.

• Computers and Concrete
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• v.23 no.3
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• pp.155-160
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• 2019

The use of recycled aggregate concrete for the purpose of environmental and resource conservation has gained increasing interest in construction engineering. Nevertheless, few studies have reported on the bonding performance of the bars in recycled aggregate concrete after exposed to high temperatures. In this paper, 72 pull-out specimens and 36 cubic specimens with different recycled coarse aggregate content (i.e., 0%, 50%,100%) were cast to evaluate the bond behavior between recycled aggregate concrete and steel bar after various temperatures ($20^{\circ}C$, $200^{\circ}C$, $400^{\circ}C$, $600^{\circ}C$). The results show that the recycled aggregate concrete pull-out specimens exhibited similar bond stress-slip curves at both ambient and high temperature. The bond strength declined gradually with the increase of the temperature. On the basis of a regression analysis of the experimental data, a revised bond strength mode and peak slip ratios relationship model were proposed to predict the post-heating bond-slip behavior between recycled aggregate concrete and steel bar.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.20 no.3
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• pp.16-23
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• 2021

The fracture characteristic of the bonded interface under the application of a sliding load to a double cantilevered specimen manufactured using lightweight material was examined. Inhomogeneously bonded materials such as Al6061-T6, CFRP, and CFRP-Al were employed. In the experiment, the specimen was loaded on both directions by applying a shearing load to the bonding interface. The experimentally obtained stress, specific strength and energy release rate values were examined. CFRP exhibited excellent specific strength. The experimental results demonstrated that the inhomogeneous bonded material CFRP-Al exhibited an overall high performance in comparison with the single materials.

• Structural Engineering and Mechanics
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• v.85 no.5
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• pp.573-592
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• 2023

This paper presents a careful theoretical investigation into interfacial stresses in composite aluminum-slab reinforced concrete beam bonded by a prestressed hybrid carbon-glass composite material. The model is based on equilibrium and deformations compatibility requirements in and all parts of the strengthened beam, i.e., the aluminum beam, the slab reinforced concrete, the hybrid carbon-glass composite plate and the adhesive layer. The theoretical predictions are compared with other existing solutions. Numerical results from the present analysis are presented both to demonstrate the advantages of the present solution over existing ones and to illustrate the main characteristics of interfacial stress distributions. It is shown that the stresses at the interface are influenced by the material and geometry parameters of the composite beam. This research is helpful for the understanding on mechanical behaviour of the interface and design of the hybrid structures.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2020.11a
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• pp.163-164
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• 2020

The purpose of this study was to evaluate the shrinkage properties of a tile reinforced with epoxy resin, which has the advantages of high adhesion and low shrinkage, and causes a hardening reaction by chemical bonding with cement mortar. As a result, since the epoxy resin adhesive suppresses the moisture evaporation of the mortar, the drying shrinkage of the mortar itself is reduced, accordingly, the shrinkage of the tile itself is greatly reduced, and it is thought that it is possible to prevent a decrease in adhesion due to shear stress.

• Restorative Dentistry and Endodontics
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• v.22 no.1
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• pp.428-446
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• 1997

Restorative procedures can lead to weakening tooth due to reduction and alteration of tooth structure. It is essential to prevent fractures to conserve tooth. The resistance to fracture of the restored tooth may be influenced by many factors, among these are the cavity dimension and the physical properties of the restorative material. The placement of direct composite resin restorations has generally been found to have a strengthening effect on the prepared teeth. It is the purpose of this investigation to study the relationship between the cavity isthmus and the fracture resistance of a tooth in composite resin restorations. In this study, MO cavity was prepared on maxillary first premolar. Three dimensional finite element models were made by serial photographic method and isthmus(1/4, 1/3, 1/2 of intercuspal distance) were varied. Two types of model(B and R model) were developed. B model was assumed perfect bonding between the restoration and cavity wall and R model was left unfilled. A load of 500N was applied vertically at the first node from the lingual slope of the buccal cusp tip. This study analysed the displacement, 1 and 2 direction normal stress and strain with FEM software ABAQUS Version 5.2 and hardware IRIS 4D/310 VGX Work-station. The results were as follows : 1. Displacement of buccal cusp in R model occurred and increased as widening of the cavity, and displacement in B model was little and not influenced by cavity width. 2. There was a significant decrease of stress resulting in increase of fracture resistance in B model when compared with R model. 3. With the increase of the isthmus width, B model showed no change in the stress and strain. In R model, the stress and strain increased both in the area of buccal-pulpal line angle and the buccal side of marginal ridge, therefore the possibility of crack increased. 4. The stress and strain were distributed evenly on the tooth in B model, but in R model, were concentrated on the buccal side of the distal marginal ridge and buccal-pulpal line angle, therefore the possibility of fracture increased.

• Korean Journal of Materials Research
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• v.9 no.10
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• pp.962-969
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• 1999

Elastic and elasto-plastic stress analyses of AlN/Cu and AlN/W pints produced by active-metal brazing method using Ag-Cu-Ti insert-metal were performed with use of Finite-Element-Method(FEM). The results of stress analyses were compared with those from the pint strength tests and the observations of fracture behaviors. It was shown that a remarkably larger maximum principal stress is built in the AlN/Cu pint compared to the A1N/ W joint. Especially, the stress concentration with tensile component was confirmed at the free surface close to the bonded interface of AlN/Cu. The elasto-plastic analysis under consideration of stress relaxation effect of Ag-Cu-Ti insert possessing a so-called 'soft-metal effect' showed that the insert leads to a lowering of maximum principal stress in AlNiCu pint, even though an increase of the insert thickness above 100$\mu\textrm{m}$ could not bring its further decrease. The maximum pint strengths measured by shear test were 52 and 108 MPa for AlNiCu and AlN/W pints. respectively. Typical fractures of AlN/Cu pints occurred in a form of 'dome' which initiated from the free surface of AlN close to the bonded interface and proceeded towards the AlN inside forming a large angle. AlN/W pints were usually fractured at AlN side along the interface of AlN/insert-metal.

• Korean Journal of Materials Research
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• v.9 no.10
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• pp.970-977
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• 1999

Effect of Mo interlayer on the relaxation of residual stress in AlN/Cu pint bonded by active-metal brazing method was investigated. The stress analyses by finite-element-method, the measurement of pint strength and the observation of fracture surface were carried out and their results were compared with each other. From the results of stress analysis it is confirmed that a Mo interlayer led to a shift of maximum stress concentration site from AlN/insert-metal interface$\rightarro$ insert-metal/Mo$\rightarro$Mo interlayer. Additionally, with increase of the Mo interlayer thickness the stress concentration with tensile component was separately built both at the interface of Cu/Mo and AlN/Mo. whereby the residual stress in the free surface of AlN close to the bonded interface was drastically reduced. The AlN/Mo/Cu pints with Mo interlayer thickness of above 400$\mu\textrm{m}$ showed the strengths higher than 200 MPa. upto max. 275 MPa, while the AlN/Cu pint only max. 52 MPa.

• 제어로봇시스템학회:학술대회논문집
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• 2005.06a
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• pp.139-144
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• 2005

A rigorous research is underway in our team, for the design and development of high figure of merits (ZT= 1.5${\sim}$2.0) micro-thermoelectric coolers. This paper discusses the fabrication process that we are using for developing the $Sb_2Te_3-Bi_2Te_3$ micro-thermoelectric cooling modules. It describes how to obtain the mechanical properties of the thin film TEC elements and reports the results of an equation-based multiphysics modeling of the micro-TEC modules. In this study the thermoelectric thin films were deposited on Si substrates using co-sputtering method. The physical mechanical properties of the prepared films were measured by nanoindentation testing method while the thermal and electrical properties required for modeling were obtained from existing literature. A finite element model was developed using an equation-based multiphysics modeling by the commercial finite element code FEMLAB. The model was solved for different operating conditions. The temperature and the stress distributions in the P and N elements of the TEC as well as in the metal connector were obtained. The temperature distributions of the system obtained from simulation results showed good agreement with the analytical results existing in literature. In addition, it was found that the maximum stress in the system occurs at the bonding part of the TEC i.e. between the metal connectors and TE elements of the module.

• Structural Engineering and Mechanics
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• v.61 no.3
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• pp.407-417
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• 2017

RC shear walls are considered one of the main lateral resisting members in buildings. In recent years, FRP has been widely utilized in order to strengthen and retrofit concrete structures. A number of experimental studies used CFRP sheets as an external bracing system for retrofitting of RC shear walls. It has been found that the common mode of failure is the debonding of the CFRP-concrete adhesive material. In this study, behavior of RC shear wall was investigated with three different micro models. The analysis included 2D model using plane stress element, 3D model using shell element and 3D model using solid element. To allow for the debonding mode of failure, the adhesive layer was modeled using cohesive surface-to-surface interaction model at 3D analysis model and node-to-node interaction method using Cartesian elastic-plastic connector element at 2D analysis model. The FE model results are validated comparing the experimental results in the literature. It is shown that the proposed FE model can predict the modes of failure due to debonding of CFRP and behavior of CFRP strengthened RC shear wall reasonably well. Additionally, using 2D plane stress model, many parameters on the behavior of the cohesive surfaces are investigated such as fracture energy, interfacial shear stress, partial bonding, proposed CFRP anchor location and using different bracing of CFRP strips. Using two anchors near end of each diagonal CFRP strips delay the end debonding and increase the ductility for RC shear walls.