• 한국도로학회논문집
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• 제19권2호
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• pp.25-34
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• 2017

PURPOSES: The purpose of this paper is to evaluate interface performance while using various tack coat materials for asphalt overlay. METHODS : The evaluation was conducted with tracking test, permeability, and interface bond strength. Tracking test was conducted using an image processing technique, to investigate the susceptibility of the tack coat materials. BBS and pull-off test were conducted to evaluate bond strength. The permeability test was conducted to evaluate the effect of tack coat materials. RESULTS : Results reveal that the trackless tack coat material demonstrates less tracking compared to other materials. Moreover, both BBS and pull-off tests can effectively evaluate the bond strength at the interface. RSC-4 was measured less bond strength. Moreover, tack coat prevents water penetration through the surface and aids the extension of the surface life of asphalt pavement. CONCLUSIONS : Trackless tack coat demonstrated a high and consistent bond strength performance. The tack coat types demonstrate marginally different performance as function of curing times. Field applicability was tested based on visual observation. Therefore, these should be considered when trackless tack coat is slightly enhanced the pavement performance based on limited this study results. Finally, it is necessary to allow reasonable time for the tack coat to completely cure.

• Tribology and Lubricants
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• 제25권2호
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• pp.86-95
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• 2009

Adhesion tests were carried out in order to investigate the effect of temperature on the adhesion behavior between a PMMA film and a fused silica lens in the micro scale. For the tests, a microtribometer system was specially designed and constructed. The pull-off forces on the PMMA film were measured under atmospheric condition as the temperature of the PMMA film was increased from 300 K to 443 K and decreased to 300 K. The contact area between the PMMA film and the lens was observed during the test. The adhesion behavior was changed with the change of the PMMA surface state as the temperature increased. In glassy state below 363 K, the pull-off force did not change with the increase of temperature. In rubbery state from 383 K to 413 K, the pull-off force increased greatly as the temperature increased. In addition, the area of contact was enlarged. In viscous state above 423 K, the fingering instability was observed in the area of contact when the PMMA film contacted with the lens. It was also found that the adhesion behavior can be varied with the thermal history of the PMMA film. The residual solvent in the PMMA film could emerge to the PMMA surface due to the heating and reduced the pull-off force.

• 산업기술연구
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• 제21권B호
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• pp.295-300
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• 2001

Significant improvements in bond strength between new and existing concrete can be achieved through the modification of the new concrete by latex modification. But, no test method has been adopted as a standard to measure the bond strength between the concrete used to repair and the substrate being repaired. The performance of old and the new concrete construction defends upon band strength between old and the new concrete. Current adhesion strength measurement method is inaccurate method that ignore effect of stress concentration by shape of specimens. Therefore, this research calculates stress concentration coefficient using finite element analysis and direction tensile strength test (pull-off test). The result shows that the required core depth is 2.5 cm. Elastic modulus and overlay thickness do not influence in stress concentration.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2002년도 봄 학술발표회 논문집
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• pp.349-354
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• 2002

Significant improvements in bond strength between new and existing concrete can be achieved through the modification of the new concrete by latex modification. But, no test method has been adopted as a standard to measure the bond strength between the concrete used to repair and the substrate being repaired. The performance of old and the new concrete construction depends upon bond strength between old and the new concrete. Current adhesion strength measurement method ignores the effect of stress concentration by shape of specimens. Therefore, this research calculates stress concentration coefficient using finite element analysis and direction tensile strength test (pull-off test). The result shows that the required core depth is 2.5cm. Elastic modulus and overlay thickness do not influence in stress concentration.

• 한국건축시공학회지
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• 제14권3호
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• pp.216-222
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• 2014

단면수복 보수를 실시한 RC조 부재의 내하성능 회복을 예측 평가하기 위하여 FEM해석이 빈도 높게 사용되고 있으나 부착에 대한 정보가 부족하여 정확도 있는 예측이 힘든 실정이다. 수치해석의 입력데이터가 되는 철근과 폴리머 시멘트 모르타르의 부착특성을 평가하기 위하여 폴리머 시멘트 모르타르를 이용한 일련의 인발실험을 실시하였다. 동시에 범용성있는 해석결과 활용을 위하여 부착특성을 부착강성과 부착강도로 정의하고 비선형 FEM 감도 역해석을 실시하였다. 결과를 요약하면 보수재료의 화학적 부착보다 물리적 부착이 지배적이며 폴리머 분말수지의 함유에 의해 다소 부착계면의 성능이 저하하는 것을 알 수 있었다. 부착계면의 물성은 강성과 강도로 구분하여 모델화하는 것이 합리적인 것으로 사료된다.

• 한국도로학회논문집
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• 제6권1호
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• pp.47-56
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• 2004

신 구 콘크리트의 부착강도 시험시 두 재료의 계면에서 파괴가 유도되어 순수한 부착강도를 측정할 수 있도록 계면에 원형의 비부착면을 삽입하여 직접인발시험에 의해 부착강도를 측정하는 실험방법을 제시하였다. 먼저, 새로 제안한 실험방법에 의해 계면에서 응력이 집중되는 정도를 파악하기 위해 유한요소해석을 수행하여 두 재료의 탄성계수비 및 비부착면의 면적 (균열률)에 따른 계면에서의 파괴에너지를 산정하였으며, 부재의 크기 및 하중에 대한 보정을 감안하여 무차원함수로 환산하였다. 그리고 본 연구에서 제시된 부착강도 시험방법의 신뢰성을 입증하기 위해, 3가지 크기의 원형 비부착면(균열률 0.2, 0.4. 0.6)이 삽입된 신 구 콘크리트 복합시편(유황 폴리머 콘크리트+보통 콘크리트)을 사용하여 부착강도를 측정하였고 앞서 전개된 무차원함수로부터 계면 파괴에너지를 역산하였다. 시험결과, 모든 시편이 계면에서 파괴가 유도되었다. 또한 실험 데이터 및 해석결과를 분석하여 균열률이 0.4$\sim$0.6인 경우에 부착강도의 오차가 가장 적게 발생될 수 있음을 파악하였다.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2010년도 추계학술대회 논문집
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• pp.881-882
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• 2010

• The Journal of Advanced Prosthodontics
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• 제13권3호
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• pp.152-159
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• 2021

Purpose. The aim of this study was to investigate to what extent cyclic load affects the screwless implant-abutment connection for Morse taper dental implants. Materials and Methods. 16 implants (SICvantage max) and 16 abutments (Swiss Cross) were used. The screwless implant-abutment connection was subjected to 10,000 cycles of axial loading with a maximum force of 120 N. For the pull-off testing, before and after the same cyclic loading, the required force for disconnecting the remaining 6 implant-abutment connections was measured. The surface of 10 abutments was examined using a scanning electron microscope 120× before and after loading. Results. The pull-off test showed a significant decrease in the vertical force required to pull the abutment from the implant with mean 229.39 N ± 18.23 before loading, and 204.30 N ± 13.51 after loading (P<.01). Apart from the appearance of polished surface areas and slight signs of wear, no visible damages were found on the abutments. Conclusion. The deformation on the polished abutment surface might represent the result of micro movements within the implant-abutment connection during loading. Although there was a decrease of the pull-off force values after cyclic loading, this might not have a notable effect on the clinical performance.

• Korea-Australia Rheology Journal
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• 제16권4호
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• pp.219-226
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• 2004

In this study the deformation of liquid-air interface of Newtonian or Boger fluids filled between two par­allel-plates geometry was investigated when two surfaces were separated at a constant speed. The interface between the fluid and air showed either stable or unstable deformation depending on experimental con­ditions. Repeated experiments for a wide range of experimental conditions revealed that the deformation mode could be classified into three types: 'stable region', 'fingering' and 'cavitation'. The experimental condition for the mode of deformation was plotted in a capillary number vs. Deborah number phase plane. It has been found that the elasticity of Boger fluids destabilize the interface deformation. On the other hand, the elasticity suppresses the formation and growth of cavities.

• Composites Research
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• 제31권6호
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• pp.323-331
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• 2018

스테인리스 강으로 제작된 요철핀의 보강이 복합재 모자형 체결부의 풀오프 강도에 미치는 영향을 시험으로 연구하였다. 요철핀에는 물리적, 화학적 표면처리를 수행하였고, 체결부의 외피와 보강재가 만나는 영역에 두께방향으로 핀을 삽입하였다. 모자형 체결부 시편은 요철핀을 포함하여 일체성형으로 제작하였다. 사용된 요철핀의 지름은 0.3, 0.5, 0.7 mm로 세 가지이다. 핀의 삽입밀도는 외피와 보강재가 만나는 면적 기준으로 0.5, 2.0% 두 가지이다. 요철핀과 일반핀의 효과를 비교하기 위하여 0.3 mm 일반핀을 2.0% 밀도로 삽입한 시편을 추가로 제작하여 시험을 수행하였다. 0.3, 0.5, 0.7 mm의 요철핀을 0.5%의 밀도로 삽입한 시편의 강도는 보강되지 않은 시편 대비 각각 45, 19, 9% 높게 나타났고, 2.0% 밀도의 경우 강도는 각각 127, 45, 11% 높게 나타났다. 시험 결과 지름이 동일할 경우 밀도가 높을수록, 밀도가 동일할 경우 지름이 작을수록 보강효과가 더 높게 나타나는 것을 알 수 있었다. 요철핀과 일반핀의 효과를 비교한 결과 2.0% 밀도로 0.3 mm 직경의 핀을 이용하여 보강할 경우, 요철핀 보강시편이 일반핀 보강 시편보다 64% 높은 강도를 보였다. 본 연구의 결과로부터 요철핀 보강이 복합재 모자형 체결부의 풀오프 강도 향상을 위한 효과적인 방법이 될 수 있음을 확인하였다.