• Steel and Composite Structures
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• 제23권1호
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• pp.17-29
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• 2017

The seismic performance of steel beam to concrete-encased composite column with unsymmetrical steel section joints is investigated and reported within this paper. Experimental and analytical evaluation were conducted on a total of 8 specimens with T-shaped and L-shaped steel section under lateral cyclic loading and axial compression. The test parameters included concrete strength, stirrup ratio and axial compression ratio. The response of the specimens was presented in terms of their hysterisis loop behavior, stress distribution, joint shear strength, and performance degradation. The experiment indicated good structural behavior and good seismic performance. In addition, a three-dimensional nonlinear finite-element analysis simulating was conducted to simulate their seismic behaviors. The finite-element analysis incorporated both bond-slip relationship and crack interface interaction between steel and concrete. The results were also compared with the test data, and the analytical prediction of joint shear strength was satisfactory for both joints with T-shaped and L-shaped steel section columns. The steel beam to concrete-encased composite column with unsymmetrical steel section joints can develop stable hysteretic response and large energy absorption capacity by providing enough stirrups and decreased spacing of transverse ties in column.

• 대한치과교정학회지
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• 제39권4호
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• pp.225-233
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• 2009

본 연구는 도재 수복물에 부착된 단결정 세라믹 브라켓의 전단접착강도와 파절양상에 열순환과 도재 수복물의 종류가 어떤 영향을 미치는지 알아보기 위해 시행되었다. 도재전장관에 사용되는 재료들 중 Ceramco 3, Empress II, Zi-ceram/Vintage ZR 세 가지를 선택하여 각 20개씩 총 60개의 시편을 원반형태(두께 2 mm, 직경 12 mm)로 제작하였다. 동일한 접착 술식으로 세라믹 브라켓을 부착한 후 열순환을 시행한 실험군과 시행하지 않은 대조군, 두 군으로 나누어 전단접착강도와 파절양상을 평가하였다. 열순환을 하지 않은 대조군의 전단접착강도는 Ceramco 3는 $7.06\;{\pm}\;1.76\;MPa$, Empress II는 $7.55\;{\pm}\;2.38\;MPa$ 그리고 Zi-ceram/Vintage ZR은 $7.19\;{\pm}\;1.38\;MPa$로 추천되는 전단접착 강도(6 - 8 MPa)에 적합한 강도를 보였으나 열순환을 시행한 실험군은 전단접착강도가 유의하게 감소하였으며(p < 0.05) 열순환 후의 전단접착강도는 Ceramco 3는 $4.88\;{\pm}\;1.00\;MPa$, Empress II는 $5.46\;{\pm}\;1.35\;MPa$ 그리고 Zi-ceram/Vintage ZR은 $4.84\;{\pm}\;1.01\;MPa$로 임상적으로 추천되는 것보다 다소 낮은 값을 보였다. 도재의 종류에 따른 전단접착강도에는 유의한 차이가 없었다. 파절양상은 대조군에서는 모두 브라켓 기저부와 접착제 사이에서 파절이 일어났으며, 실험군에서는 2개의 시편(Ceramco 3과 Zi-ceram/Vintage ZR군에서 각 1개)만이 접착제내 파절을 보였으며 28개의 시편은 브라켓 기저부와 접착제 사이에서 파절이 일어났다. 이상의 연구 결과에서 보았을 때 도재 수복물의 종류에 따른 차이는 없었으나 열순환에 의해 전단접착강도가 약화되므로 실제 임상에서 고려되어야 할 것이다.

• Advances in concrete construction
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• 제8권4호
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• pp.285-294
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• 2019

In the present paper, the fiber theory has been employed to model the reinforced concrete (RC) deep beams (DBs) considering the reinforcing steel bar-concrete interaction. To simulate numerically the behavior of materials, the uniaxial materials' constitutive laws have been employed for reinforcements and concrete and the bond stress-slip between the reinforcing steel bars and surrounding concrete are taken into account. Because of the high sensitivity of DBs to shear deformations, the Timoshenko beam theory has been applied. The shear stress-strain (S-SS) relationship has been defined by the modified compression field theory (MCFT) model. By modeling about 300 RC panels and employing a produced numerical database, a study has been carried out to show the sensitivity of the MCFT model. This is performed based on the multiple linear regression (MLR) models. The results of this research also illustrate how different parameters such as characteristic compressive strength of concrete, yield strength of reinforcements and the percentages of reinforcements in different directions get involved in the shear behavior of RC panels without applying complex theories. Based on the results obtained from the analysis of the MCFT S-SS model, a relatively simplified numerical S-SS model has been proposed. Application of the proposed S-SS model in modeling and analyzing the considered samples indicates that there is a good agreement between the simulated and the experimental test results. The comparison between the proposed S-SS model and the MCFT model indicates that in addition to the advantage of better accuracy, the main advantage of the proposed method is simplicity in application.

• International Journal of Korean Welding Society
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• 제5권1호
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• pp.15-28
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• 2005

The ball shear test was investigated in terms of the effects of test parameters, i.e., shear height and shear speed, with an experimental and non-linear finite element analysis for evaluating the solder joint integrity of area array packages. Two representative Pb-free solder compositions were examined in this work: Sn-3.5Ag-0.75Cu and In-48Sn. The substrate was a common SMD type with solder bond pad openings of 460 $\mu$m in diameter. The microstructural investigations were carried out using SEM, and the IMCs were identified with EDS. Shear tests were conducted with the two varying test parameters. It could be observed that increasing shear height, at fixed shear speed, has the effect of decreasing shear force for both Sn-3.5Ag-0.75Cu and In-48Sn solder joints, while the shear force increased with increasing shear speed at fixed shear height. Too high shear height could cause some undesirable effects on the test results such as unexpected high standard deviation values or shear tip sliding from the solder ball. The low shear height conditions were favorable for screening the type of brittle interfacial fractures or the degraded layers in the interfaces. The shear speed conditions were discussed with the stress analyses of the solder ball, and we cannot find any conspicuous finding which is related to optimum shear speed from the stress analyses.

• Restorative Dentistry and Endodontics
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• 제43권2호
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• pp.19.1-19.10
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• 2018

Objectives: This study investigated the effect of continuous application of 10-methacryloyloxydecyldihydrogen phosphate (MDP)-containing primer and luting resin cement on bond strength to tribochemical silica-coated yttria-stabilized tetragonal zirconia polycrystal (Y-TZP). Materials and Methods: Forty bovine teeth and Y-TZP specimens were prepared. The dentin specimens were embedded in molds, with one side of the dentin exposed for cementation with the zirconia specimen. The Y-TZP specimen was prepared in the form of a cylinder with a diameter of 3 mm and a height of 10 mm. The bonding surface of the Y-TZP specimen was sandblasted with silica-coated aluminium oxide particles. The forty tribochemical silica-coated Y-TZP specimens were cemented to the bovine dentin (4 groups; n = 10) with either an MDP-free primer or an MDP-containing primer and either an MDP-free resin cement or an MDP-containing resin cement. After a shear bond strength (SBS) test, the data were analyzed using 1-way analysis of variance and the Tukey test (${\alpha}=0.05$). Results: The group with MDP-free primer and resin cement showed significantly lower SBS values than the MDP-containing groups (p < 0.05). Among the MDP-containing groups, the group with MDP-containing primer and resin cement showed significantly higher SBS values than the other groups (p < 0.05). Conclusions: The combination of MDP-containing primer and luting cement following tribochemical silica coating to Y-TZP was the best choice among the alternatives tested in this study.

• 대한치과보철학회지
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• 제27권2호
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• pp.155-172
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• 1989

The purpose of this study is to measure the bonding strength at the enamel and dentin of extracted bovine incisors when they are irradiated by W Nd: YAG, EoQ Nd: YAG, and CW $CO_2$ laser, etched and then attached by composite resin. The laser-irradiated surface, the etched surface after the laser-irradiation and the interface of the treated surface and resin are observed by using scanning electron microscope. The NP Nd:YAG laser is used at the peam power of 207 KW. The EOQ Nd: YAG laser is used at the peak power of 1.15Mk. The CW $CO_2$ laser is used at the energy output of 5W and 10W in enamel; in dentin, at the energy output of 2W. The obtained results were as follows: 1. The shear bond strength of enamel decreased in the following order: EOQ Nd:YAG laser group, NP Nd:YAG laser group, CW $CO_2$ laser groups, unlased group. The unlased group showed a significant difference from EOQ Nd:YAG laser group (P<0.01), NP Nd:YAG laser group (P<0.05), but no significant difference from CW $CO_2$ laser group (P>0.05). 2. The shear bond strength of dentin decreased in the following order: CW $CO_2$ laser group, NP Nd:YAG laser group, unlased group, EOQ Nd:YAG laser group. The unlased group showed a significant difference from CW $CO_2$ laser group (P<0.01), but no significant difference from Nd:YAG laser groups (P>0.05). 3. The scanning electron microscope of enamel revealed irregular microcrack and pore at the surface in the NP Nd:YAG laser group and CW $CO_2$ laser group, but the crackless flat surface in the EOQ Nd:YAG laser group. 4. The scanning electron microscope of dentin revealed obstruction of in most of dentinal tubule and decrease of diameter. 5. The scanning electron microscope of the interface of resin and enamel revealed prominent penetration of resin tag in the EOQ Nd:YAG laser group.

• Restorative Dentistry and Endodontics
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• 제29권2호
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• pp.177-184
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• 2004

본 연구는 광중합형 상아질 접착제에서 광조사 시간의 증가가 접착제 표면의 미중합층에 대한 영향과 그에 따른 전단접착강도에 대해 연구하고자 120개의 치아를 아크릴 몰드에 식립한 후 상아질이 노출되도록 연마하였다. 3종류의 접착제 〔All Bond2 (AB2), One-Step (OS) and Adper Prompt (AP)〕를 40개 치아에 제조사의 지시대로 도포한 후 각각 다른 광조사 시간 (10, 20, 30 and 60sec)동안 광조사 하고 복합레진을 접착한 24시간 후 전단접 착강도를 측정하였다. 미중합층의 두께와 중합률은 슬라이드 글라스와 FT-NIR을 이용하여 FT-NIR spectrum에서의 peak height를 비교 측정하여 다음과 같은 결론을 얻었다. 1. 전단접착강도에서 AB2는 20초 이후 감소하고, AP는 30초까지 증가하였으며,OS는 차이를 보이지 않았다. 2. 미중합층 두께는 3가지 접착제 모두 유의성 있는 차이를 보이지 않았다. 3. 중합률에서 OS는 10초와 나머지군 사이에 유의성 있는 차이를, AP는 60초에서 유의성 있게 증가되고, AB2의 경우 차이를 나타내지 않았다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2005년도 봄학술 발표회 논문집(I)
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• pp.243-246
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• 2005

This paper focuses on the flexural behavior of RC beams externally reinforced using Carbon Fiber Reinforced Plastics plates (CFRP). A non-linear finite element (FE) analysis is proposed in order to complete the experimental analysis of the flexural behaviour of the beams. This paper is a part of a complete program aiming to set up design formulate to predict the strength of CFRP strengthened beams, particularly when premature failure through plates-end shear or concrete cover delamination occurs. An elasto-plastic behaviour is assumed for reinforced concrete and interface elements are used to model the bond and slip.

• 대한금속재료학회지
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• 제50권1호
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• pp.71-77
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• 2012

We studied the effect of heat treatment on the microstructures and mechanical strength of the solder joints in the Light Emitting Diode (LED) packages. The commercial LED packages were mounted on the a flame resistance-4 (FR4) Printed Circuit Board (PCB) in the reflow process, and then the joints were aged at $125^{\circ}C$ for 100, 200, 300, 500 and 1000 hours, respectively. After the heat treatment, we measured the shear strength of the solder joints between the PCB and the LED packages to evaluate their mechanical property. We used Pb-free Sn-3.0Ag-0.5Cu solder to bond between the LED packages and the PCBs using two different surface finishes, Electroless Nickel-Immersion Gold (ENIG) and Electroless Nickel-Electroless Palladium-Immersion Gold (ENEPIG). The microstructure of the solder joints was observed by a scanning electron microscope (SEM). (Cu,Ni)6Sn5 intermetallic compounds (IMCs) formed between the solder and the PCB, and the thickness of the IMCs was increased with increasing aging time. The shear strength for the ENIG finished LED package increased until aging for 300 h and then decreased with increasing aging time. On the other hand, in the case of an ENEPIG finished LED package, the shear strength decreased after aging for 500 h.

• 대한치과기공학회지
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• 제36권3호
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• pp.171-177
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• 2014

Purpose: The dental medicine has been preparing the custom-made service to meet the requirements of the aged society, while the average span of human life is growing more and more, and the full denture is a representative of them. It is causing great concern in these atmosphere of society, and demands for it are expected to increase. The full denture is a uniform combination of denture base and artificial teeth using polymerization, and is most influenced by change of physical properties of denture base and bonding strength with artificial teeth. Methods: In this study, the samples were made of composite resin combined with occlusion surface of artificial teeth undergone mechanically surface treatment to evaluate the bonding strength of composite resin for repairing artificial teeth. The resin teeth used in this study are 3 types artificial teeth. And 3 types of composite resins are used that are various polymerization resin. The shear strength of composite resins made in various polymerization ways to resin teeth was measured to evaluate bonding strength of artificial teeth to each composite resins. Results: Surface hardness's results on Trubyte Biotone(74.58Hv), Biotone IPN(70.06Hv), Endura Posterio (64.48Hv). Results of bonding strength of artificial teeth to composite resins on ES samples(8.73Mpa), IF(4.37Mpa) and IZ(3.84Mpa). Conclusion: 1. The Trubyte Biotone(74.58Hv) was first, followed by Biotone IPN(70.06Hv), and Endura Posterio(64.48Hv) in surface hardness's results of worn sides using hardness test. 2. The ES samples(8.73Mpa) showed significant differences with IF(4.37Mpa) and IZ(3.84Mpa) (p<0.05), but not other samples(p>0.05) in results of bonding strength of artificial teeth to composite resins.