• Steel and Composite Structures
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• 제42권2호
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• pp.191-207
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• 2022

Undoubtedly, the employment of direct bond interaction between steel and concrete is preceding the other mechanisms because of its ease of construction. However, the large scatter in the experimental data about the issue has hindered the efforts to characterize bond strength. In the following research, the direct bond interaction and bond-slip behavior of CFTs with circular cross-section were examined through repeated load-reversed push-out tests until four cycles of loading. The influence of different parameters including the diameter of the tube and the use of shear tabs were assessed. Moreover, the utilization of expansive concrete and external spirals was proposed and tested as ways of improving bond strength. According to the results section dimensions, tube slenderness, shrinkage potential of concrete, interface roughness and confinement are key factors in a natural bond. Larger diameters will lead to a considerable drop in bond strength. The use of shear tabs by their associated bending moments increases the bond stress up to eight times. Furthermore, employment of external spirals and expansive concrete have a sensible effect on enhancing bonds. Macro-locking was also found to be the main component in achieving bond strength.

• 한국공간구조학회논문집
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• 제18권4호
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• pp.61-68
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• 2018

Tensile load tests were conducted on High-Shear Ring Anchors (HRAs) after shear load had been applied to the HRAs, which had been developed to reduce the number of the anchors. Test variables include the embedment length of the rod and the width of the specimens and a total of 12 specimens were tested. Test results show that the HRAs pulled out due to bond failure or steel failure occurred in case that the HRAs were installed to the members with 300mm or greater width and the embedment length of 160mm (the actual embedment of rod is 140mm) or deeper. Except 4 HRAs showing steel failure of rod, the minimum and average of test-to-prediction by ACI 318-14 ratios are 1.18 and 1.79, respectively. The tensile strength of HRAs, after shear load was applied to the HRAs, can be safely evaluated by the minimum among the concrete breakout strength and bond strength with the actual embedment length of the rod.

• 대한치과보철학회지
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• 제42권5호
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• pp.501-513
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• 2004

Purpose : The purpose of this study was to evaluate the effects of etching time on shear bond strength of four resin cements to IPS Empress 2 ceramic. Material and Methods: Forty rectangular shape ceramic specimens ($10{\times}15{\times}3.5mm$ size) were used for this study. The ceramic specimens divided into four groups and were etched with 10% hydrofluoric acid for 0, 10, 30, 60, 180, 300, 420, 600, and 900 seconds respectively. Etched surfaces of ceramic specimens were coated with ceramic adhesive system and bonded with four resin cement (Variolink II, Panavia F, Panavia 21, Super-Bond C&B) using acrylic glass tube. All cemented specimens were tested under shear loading untill fracture on universal testing machine at a crosshead speed 1mm/min: the maximum load at fracture (kg) was recored. Shear bond strengh data were analyzed with oneway analysis of variance and Tukey HSD tests (p<.05). Etched ceramic surfaces (0-, 60-, 300-, and 600-seconds etching period) and fracture surfaces after shear testing were examined mophologically using scanning electron microscopy. Results : Ceramic surface treatment with 10% hydrofluoric acid improved the bond strength of three resin cement except for Super-Bond C&B cement. Variolink II (41.0$\pm$2.4 MPa) resin cement at 300-seconds etching time showed statistically higher shear bond strength than the other resin cements (Panavia F: 28.3$\pm$2.3 MPa, Panavia 21: 21.5$\pm$2.2 MPa, Super-Bond C&B: 16.7$\pm$1.6 MPa). Ceramic surface etched with 10% hydrofluoric acid for 300 seconds showed more retentive surface texture. Conclusion: Within the limitation of this study, Variolink II resin cement are suitable for cementation of Empress 2 all-ceramic restorations and etching with 10% hydrofluoric acid for 180 to 300 seconds is required to enhance the bond strength.

• KCI Concrete Journal
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• 제14권1호
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• pp.1-7
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• 2002

This paper reports the experimental and analytical investigations for evaluating the flexural strength of a RC slab strengthened with carbon fiber sheet (CFS). The evaluation of the ultimate flexural strength of a slab is tried under the assumption that the failure occurs when the shear stress mobilized at the interface between the concrete bottom and the glued CFS reaches its bond strength. The shear stress is evaluated theoretically and the bond strength is obtained by a laboratory test. The ultimate flexural strength is obtained by flexural static test of the slab specimen, which corresponds to the part of a real slab. From the results, the new approach based on the bond strength between concrete and CFS looks feasible to evaluate the flexural strength of the CFS and RC composite slab.

• 대한치과교정학회지
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• 제22권2호
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• pp.327-343
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• 1992

Metal brackets and ceramic brackets were bonded to natural teeth, porcelain crowns and gold crowns After stored in artificial saliva solution for 72 hours at $37^{\circ}C$, the shear bond strengths were measured by Instron and compared with them, the bonding sites and bracket bases were examined by scanning electron microscope and light optical stereomicroscope. The results were as follows: 1. The shear bond strengths of the group which metal brackets were bonded to natural teeth and the groups which ceramic brackets were bonded to natural teeth and porcelain crowns were comparable to each other, the shear bond strength of the group which metal brackets were bonded to gold crowns was significantly low. 2. The bond failed predominantly at the bracket base/adhesive interface with the bulk of adhesive remaining on enamel in the group which metal brackets were bonded to natural teeth. 3. The bond failed consistently at the crown/adhesive interface with all of adhesive remaining on the bracket babes in the group which metal brackets were bonded to gold crowns. 4. The bond failed at the enamel or crown/adhesive interface with the bulk of adhesive remaining on the bracket bases in the groups which cramic brackets were bonded to natural teeth and porcelain crowns. 5. The shear bond strengths of the groups which ceramic brackets were bonded to porcelain crowns were not affected by etching time.

• 대한치과보철학회지
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• 제56권3호
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• pp.199-205
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• 2018

목적: 이 연구는 저온 플라즈마가 자가중합형 재이장용 레진과 주입형 열가소성 의치상 레진의 결합 강도에 미치는 영향을 다른 표면 처리 방법에서 평가하기 위함이다. 재료 및 방법: 네 가지 열가소성 의치상이 이 연구에서 사용되었다: Acrylic Resin (Acrytone), Polyester (Estheshot-Bright), Polyamide (Valplast), Polypropylene (Weldenz)에 다양한 표면처리를 시행하였다: 대조군, 저온플라즈마, Sandblasting, Sandblasting와 저온플라즈마. 표면 처리 후 모든 시편은 Tokuyama Rebase II를 이용하여 원형의 테플론 관에 접착되었다. 전단강도는 Universal testing machine을 통해 crosshead speed 1 mm/min으로 측정되었다. 통계 분석 방법으로는 이원분산분석을, 사후 검정 방법으로는 Tukey's test가 사용되었다. 결과: Acrytone이 다른 열가소성 의치상 레진 그룹에 비하여 통계적으로 유의한 수준에서 더 높은 전단강도를 보인 반면 Weldenz는 가장 낮은 값을 나타냈다. Sandblast와 저온플라즈마를 순차적으로 시행한 조건에서 모든 레진 그룹 중 통계적으로 유의한 수준에서 가장 높은 전단강도 값을 나타냈다. 결론: 열경화성 의치상 레진과 재이장용 레진 사이의 전단강도에 저온플라즈마는 제한된 효과를 나타내었으며, sandblasting 처리와 함께 처리되었을 때 두 재료간 전단강도는 향상되었다.

• 구강회복응용과학지
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• 제37권3호
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• pp.101-110
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• 2021

목적: 본 연구에서는 3D 프린팅 레진과 임시 수복용 레진의 열순환 처리에 따른 전단결합강도의 변화를 연구하고자 하였다. 연구 재료 및 방법: DLP 방식을 이용하여 3D 프린팅 레진으로 표본을 제작하였다. 표본은 상부에 부착한 임시 수복용 레진(PMMA, bis-acryl resin) 및 열순환 처리 횟수(대조군, 2,000, 3,000, 5,000회)에 따라 8개의 군으로 분류하였다. 만능 재료시험기 상에서 결합된 표본들의 전단결합강도를 측정하였다. 결과: 열순환 처리의 횟수가 증가함에 따라 3D 프린팅 레진에 대한 PMMA와 bis-acryl resin의 전단결합강도는 PMMA에서 3,000회와 5,000회 간을 제외하고 모두 감소하였다. PMMA 그룹에서는 3,000회 미만의 열순환 처리 횟수 간에서 유의한 전단결합강도의 차이를 보였으며(P < 0.05), 3,000회 이상의 열순환 처리 횟수 간에는 유의한 차이를 보이지 않았다(P > 0.05). Bis-acryl resin 그룹에서는 대조군과 2,000회 간, 대조군과 3,000회 간, 대조군과 5,000회 간의 열순환 처리에는 유의한 전단결합강도의 차이가 있었으며(P < 0.05), 2,000회와 3,000회 간, 3,000회와 5,000회 간에는 유의한 차이가 없었다(P > 0.05). 결론: 3D 프린팅 레진에 대한 임시 수복용 레진의 전단결합강도는 열순환 처리를 한 경우 결합강도가 낮아지는 경향을 보였다.

• 콘크리트학회논문집
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• 제13권2호
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• pp.168-174
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• 2001

탄소섬유쉬트는 고강도, 경량 및 고 내구성 등의 우수한 재료적 성질을 가지고 있어 철근콘크리트 건축물의 보수 .보강재료 장범위하게 사용되어져 왔다. 탄소섬유쉬트와 콘크리트 사이의 부착강도 즉, 부착거동은 탄소섬유쉬트에 의해 보수.보강되는 철근콘크리트 부재의 보강성능을 좌우하는 매우 중요한 요소이다. 따라서, 탄소섬유쉬트와 콘크리트의 접합면에서 발생되는 부착파괴의 메카니즘은 명확히 구명될 필요가 있다. 본 연구에서는 양생온도, 콘크리트의 표면상태 및 함수율 등의 환경요소변화에 따른 탄소섬유쉬트와 콘크리트의 인발접착강도을 파악함으로써 환경요소의 영향을 평가하였으며 아울러, 탄소섬유쉬트와 콘크리트와의 부착성능을 결정하는 유효부착길이 및 평균부착응력도를 평가하였다. 연구결과, 인발접착강도에 미치는 환경요소에서 양생온도가 가장 중요한 영향인자로 나타났으며, 인장전단부착 실험으로부터 얻어진 유효부착길이 및 평균부착응력도는 각각 15 cm 및 9.78~11.88kgf/$\textrm{cm}^2$ 내외라고 사료된다.

• Restorative Dentistry and Endodontics
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• 제30권4호
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• pp.283-293
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• 2005

본 연구는 합착 술식에 따른 레진 합착제의 상아질에 대한 미세전단결합강도를 비교 연구하여 이중 접착 술식의 유용성을 평가하고자 시행되었다. 합착 술식은 전통 합착 술식과 이중 접착 술식, 임시 합착제는 Propac과 Freegenol, 상아질 접착제는 All-Bond 2, One-Step, Clearfil SE Bond를 사용하였다. 이중 접착 술식을 적용한 군에서만 상아질 접착제 처리 후, 모든 시편에 임시 합착제를 도포하였다. 이후 임시 합착제를 제거하고 상아질 접착제 적용 후 유리봉에 레진 합착제를 도포하여 상아질 면에 접착하였다. 미세전단결합 강도를 측정하고 접착 계면을 주사전자현미경으로 관찰하였다. 1. 전통 합착 술식이 이중 접착 술식보다 높은 미세전단결합강도를 보였으나 통계학적 유의 차가 없었다. 2. Freegenol이 Propac보다 높은 미세전단결합강도를 보였으나 유의차가 없었다. 3. 미세전단결합강도는 이중 접착 술식 을 적용한 경우 Clearfil SE Bond가 One-step, All-Bond 2보다 유의성 있게 높았으나(p<0.05) One-step, All-Bond 2 간 유의차는 없었다. 4. 전자현미경 소견에서 All-Bond 2와 One-Step을 사용한 군은 길고 수많은 resin tag가 관찰되었다. 본 연구 결과 전통 합착 술식과 비교하여 이중 접착 술식의 우수함을 확인하지 못하였다.

• 대한치과보철학회지
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• 제35권2호
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• pp.365-372
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• 1997

This study was executed to measure the shear bond strength of Panavia EX and Panavia 21 when the Ni-Cr-Be alloy castings were cemented to the enamel surfaces with these cements. The cast metal plates of Ni-Cr-Be alloy were sandblasted and cemented to acid etched enamel surface with Panavia EX or Panavia 21. Their shear bond strength were measured with Instron Universal Testing machine. Within the limits of this study, following conclusions were withdrawn. 1. The mean shear bond strength were 26.85.7MPa, in Panavia EX and 28.35.2MPa, in Panavia 21. 2. t-Test revealed no statistical significance between two groups(.05 level) 3. Macroscopically, bond failures were revealed compound fracture at metal and enamel interfaces, in cases of both cements, as the cement attached partly on both metal and enamel surface.