• Geomechanics and Engineering
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• 제28권6호
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• pp.599-611
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• 2022

Tendon reinforced cemented soil is applied extensively in foundation stabilisation and improvement, especially in areas with soft clay. To solve the deterioration problem led by steel corrosion, the glass fiber-reinforced polymer (GFRP) tendon is introduced to substitute the traditional steel tendon. The interface bond strength between the cemented soil matrix and GFRP tendon demonstrates the outstanding mechanical property of this composite. However, the lack of research between the influence factors and bond strength hinders the application. To evaluate these factors, back propagation neural network (BPNN) is applied to predict the relationship between them and bond strength. Since adjusting BPNN parameters is time-consuming and laborious, the particle swarm optimisation (PSO) algorithm is proposed. This study evaluated the influence of water content, cement content, curing time, and slip distance on the bond performance of GFRP tendon-reinforced cemented soils (GTRCS). The results showed that the ultimate and residual bond strengths were both in positive proportion to cement content and negative to water content. The sample cured for 28 days with 30% water content and 50% cement content had the largest ultimate strength (3879.40 kPa). The PSO-BPNN model was tuned with 3 neurons in the input layer, 10 in the hidden layer, and 1 in the output layer. It showed outstanding performance on a large database comprising 405 testing results. Its higher correlation coefficient (0.908) and lower root-mean-square error (239.11 kPa) were obtained compared to multiple linear regression (MLR) and logistic regression (LR). In addition, a sensitivity analysis was applied to acquire the ranking of the input variables. The results illustrated that the cement content performed the strongest influence on bond strength, followed by the water content and slip displacement.

• Journal of Mechanical Science and Technology
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• 제16권7호
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• pp.911-918
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• 2002

The tribological performance of A1$_2$O$_3$/NiCr coating deposited on steel (SH45C) was investigated under lubrication. The parameters of sliding wear consist of normal load and coating thickness. Test result showed that there was no evidence of an improved bonding strength in the coating. However, the wear resistance of the A1$_2$O$_3$/NiCr coaling was significantly greater than that of the Al$_2$O$_3$ coating. It was eviclent that the residual stress for the A1$_2$O$_3$coating was higher than that of the A1$_2$O$_3$/NiCr coating from the Scratch test failure of coating. The bond coating played an important role in decreasing the residual stress. Also, it was found that the residual stress had d notable influence on the wear mechanism.

• Structural Engineering and Mechanics
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• 제53권6호
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• pp.1183-1200
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• 2015

Reinforcement corrosion can cause serious safety deterioration to aging concrete structures exposed in aggressive environments. This paper presents an approach for reliability analyses of deteriorating reinforced concrete structures affected by reinforcement corrosion on the basis of the representative symptoms identified during the deterioration process. The concrete cracking growth and rebar bond strength evolution due to reinforcement corrosion are chosen as key symptoms for the performance deterioration of concrete structures. The crack width at concrete cover surface largely depends on the corrosion penetration of rebar due to the expansive rust layer at the bond interface generated by reinforcement corrosion. The bond strength of rebar in the concrete correlates well with concrete crack width and decays steadily with crack width growth. The estimates of cracking development and bond strength deterioration are examined by experimental data available from various sources, and then matched with symptom-based lifetime Weibull model. The symptom reliability and remaining useful life are predicted from the predictive lifetime Weibull model for deteriorating concrete structures. Finally, a numerical example is provided to demonstrate the applicability of the proposed approach for forecasting the performance of concrete structures subject to reinforcement corrosion. The results show that the corrosion rate has significant impact on the reliability associated with serviceability and load bearing capacity of reinforced concrete structures during their service life.

• International Journal of Reliability and Applications
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• 제6권2호
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• pp.79-85
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• 2005

We show how comparative mean residual life functions (MRL) can be used to give unique insights into strengths of materials data. Recall that Weibull's original reliability function was developed studying and fitting strengths for various materials. This creative comparing of MRL functions approach can be used for regular life data or any time to response data. We apply graphical MRL's to real data from tests of tensile strength of high quality engineered wood.

• Restorative Dentistry and Endodontics
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• 제38권4호
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• pp.234-240
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• 2013

Objectives: This study evaluated the effects of intraradicular moisture on the pushout bond strength of a fibre post luted with several self-adhesive resin cements. Materials and Methods: Endodontically treated root canals were treated with one of three luting cements: (1) RelyX U100, (2) Clearfil SA, and (3) G-Cem. Roots were then divided into four subgroups according to the moisture condition tested: (I) dry: excess water removed with paper points followed by dehydration with 95% ethanol, (II) normal moisture: canals blot-dried with paper points until appearing dry, (III) moist: canals dried by low vacuum using a Luer adapter, and (IV) wet: canals remained totally flooded. Two 1-mm-thick slices were obtained from each root sample and bond strength was measured using a push-out test setup. The data were analysed using a two-way analysis of variance and the Bonferroni post hoc test with p = 0.05. Results: Statistical analysis demonstrated that moisture levels had a significant effect on the bond strength of luting cements (p < 0.05), with the exception of G-Cem. RelyX U100 displayed the highest bond strength under moist conditions (III). Clearfil SA had the highest bond strength under normal moisture conditions (II). Statistical ranking of bond strength values was as follows: RelyX U100 > Clearfil SA > G-Cem. Conclusions: The degree of residual moisture significantly affected the adhesion of luting cements to radicular dentine.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2005년도 추계 학술발표회 제17권2호
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• pp.283-286
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• 2005

Recently, the deterioration of concrete structures have been increased by the damage from salt, carbonization, freezing & thawing and the others. Reinforcement corrosion is the principal cause of deterioration of reinforced concrete. Unfortunately, full bond is assumed in all existing shear models, a condition which is often not fulfilled when assessing damaged structures. It is therefore very important to increase the understanding of how reduced bond influences the load carying capacity particularly for shear. Therefore in this study an equation is proposed to evaluate the residual shear strength considered deterioration.

• Restorative Dentistry and Endodontics
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• 제39권4호
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• pp.303-309
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• 2014

Objectives: Hydrogen peroxide ($H_2O_2$) surface treatment of fiber posts has been reported to increase bond strength of fiber posts to resin cements. However, residual oxygen radicals might jeopardize the bonding procedure. This study examined the effect of three antioxidant agents on the bond strength of fiber posts to conventional and self-adhesive resin cements. Materials and Methods: Post spaces were prepared in forty human maxillary second premolars. Posts were divided into five groups of 8 each: G1 (control), no pre-treatment; G2, 10% $H_2O_2$ pre-treatment; G3, G4 and G5. After $H_2O_2$ application, Hesperidin (HES), Sodium Ascorbate (SA) or Rosmarinic acid (RA) was applied on each group respectively. In each group four posts were cemented with Duo-Link conventional resin cement and the others with self-adhesive BisCem cement. Push-out test was performed and data were analyzed using 2-way ANOVA and tukey's post-hoc test (${\alpha}=0.05$). Results: There was a statistically significant interaction between the cement type and post surface treatment on push-out bond strength of fiber posts (p < 0.001, F = 16). Also it was shown that different posts' surface treatments significantly affect the push-out bond strength of fiber posts (p = 0.001). $H_2O_2$ treated posts (G2) and control posts (G1) cemented with Duo-link showed the highest ($15.96{\pm}5.07MPa$) and lowest bond strengths ($6.79{\pm}3.94$) respectively. Conclusions: It was concluded that $H_2O_2$ surface treatment might enhance the bond strength of fiber posts cemented with conventional resin cements. The effect of antioxidants as post's surface treatment agents depends on the characteristics of resin cements used for bonding procedure.

• 대한치과보철학회지
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• 제34권3호
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• pp.620-631
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• 1996

Bonding of resin to cast alloy has traditionally been provided by mechanical retention. But, chemical bonding methods such as silicoating, tin plating, heat treatment, application of 4-META adhesives, have been developed to overcome the problems of the mechanical bonding methods. Silicoating has been used availaby in fixed prosthodontics, but is also reported to be used in removable prosthodontics. The aim of this study is to measure the tensile bond strength between resin and metal, and compare the effect of the type of metal and the grain size of the aluminum oxide on the bond strength, after metal surface roughening, coating of the opaque resin, and curing of heat-curing resin were performed. The test groups were divided into 4 groups according to the cast alloys and the aluminum oxide particles used. Group 1 : Type 4 gold alloy(DM66) blasted with $$50{\mu}m\;Al_{2}O_3$$ Group 2 : Type 4 gold alloy(DM66) blasted with $$250{\mu}m\;Al_{2}O_3$$, Group 3 : Co-Cr alloy(Nobilium) blasted with $$50{\mu}m\;Al_{2}O_3$$ Group 4 : Co-Cr alloy(Nobilium) blasted with $$250{\mu}m\;Al_{2}O_3$$ * 10 test specimens were made on each group. The specimens were thermocycled, and Instron Universal testing machine was used to measure the tensile bond strength of the finished specimens. The results were as follows : 1. Bond strengths showed that the group of gold alloy blasted with $250{\mu}m$ aluminum oxide particle had higher bond strength, and the group of gold alloy blasted with $50{\mu}m$ aluminum oxide particles had lower bond strength than any of the other groups. 2. Gold alloy had significantly higher bond strength when blasted with $250{\mu}m$ aluminum oxide particles than $50{\mu}m$, but. Co-Cr alloy showed no statistically significant difference between the two particle sizes. 3. When blasted with $50{mu}m$ aluminum oxide particles, Co-Cr alloy showed significantly higher bond strength than gold alloy. And, when blasted with $250{\mu}m$ aluminum oxide particles, gold alloy had significantly higher bond strength than Co-Cr alloy. 4. On the examination of the fractured sites, only the group of Co-Cr alloy blasted with $50{\mu}m$ aluminum oxide particles showed a part of residual opaque resin, but all the samples of the other groups fractured between the resin and the metal.

• 콘크리트학회논문집
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• 제12권1호
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• pp.13-22
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• 2000

This paper describes the results obtained from 11 direct tension tests to explore the influence of concrete strength on tension stiffening behavior in reinforced concrete axial members. Three different concrete compressive strengths, 250, 650, and 900kgf/$\textrm{cm}^2$, were included as a main variable, while the ratio of cover thickness-to-rebar diameter was kept constant to be 2.62 to prevent from splitting cracking. As the results, it was appeared that, as higher concrete strength was used, less tension stiffening effect was resulted, and the residual deformation upon unloading was larger. In addition, the spacing between adjacent transverse cracks became smaller with higher concrete strength. The major cause for those results may be attributed to the fact that nonuniform bond stress concentration at both loaded ends and crack sections becomes severer as higher concrete is used, thereby local bond failure becomes more susceptible. From these findings, it would be said the increase in flexural stiffness resulting from using high-strength concrete will be much smaller than that predicted by the conventional knowledge. Finally, a factor accunting for concrete strength was introduced to take account for the effect of HSC on tension stiffening. This proposed equation predicts well the tension stiffening for the effect of HSC on tension stiffening. This proposed equation predicts well the tension stiffening behavior of these tests.

• 대한치과교정학회지
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• 제37권4호
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• pp.283-292
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• 2007

새로운 접착 시스템의 개발로 브라켓의 접착 과정이 단순화되고 있는 추세이다. 본 연구에서는 통상적인 산 부식 방법과 더불어 수종의 교정용 및 수복용 self etching primer를 이용하여 브라켓을 접착한 후 전단결합강도를 측정하고 접착 파절 양상을 비교함으로써 self etching primer 유용성을 평가하였다. 교정 치료를 위해 발거한 상, 하악 소구치 75개를 레진 블록에 매몰하여 시편을 제작하였고, 산 부식이 필요한 Transbond XT primer와, 4종의 self etching primer (Transbond Plus Self Etching Primer, Unifill Bond, Clearfil SE bond, Adhese)를 각각 이용하여 브라켓을 접착한 후, 만능시험기로 전단결합강도를 측정하고, 브라켓 기저면을 광학현미경으로 관찰하여 접착 파절 양상을 관찰하였다. 접착제 잔류지수를 비교한 결과, 통계적으로 유의한 차이는 없었으나, 인산 처리군이 self etching primer 처리군에서 보다 낮은 값을 보여, self etching primer 처리군이 인산 처리군 보다 법랑질-레진 접착계면 부위에서의 파절이 많이 일어나는 경향이 있었음을 알 수 있었다. Self etching primer 처리군에서의 전단결합강도는 37% 인산 처리군의 전단결합강도보다 낮았지만(p < 0.05), 임상적으로 유용한 수준 이상이었으며, self etching primer 처리군 내에서 각각의 전단결합강도는 유의한 차이를 보이지 않았다 (p > 0.05). 따라서 self etching primer를 이용할 경우, 기존의 산 부식법에 비하여 다소 낮은 전단결합강도를 보이지만 임상적으로 충분히 사용 가능하다고 생각된다.