• 한국표면공학회지
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• 제25권4호
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• pp.165-172
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• 1992

Filler, popularly used in the polymer materials, was dispersed randomly and irregularly. For the study of dispersed behavior, the specimen which have two particles in polystyrene was prepared. And the tensile strength, modulus and SEM picture were measured. When the distance between particles increased, the tensile strength and modulus increased, but particle size did not affect the values. And when the am-bient temperature increased, the tensile strength and modulus decreased, but the distance did not affect the tensile strength and modulus.

• 한국생산제조학회지
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• 제8권6호
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• pp.113-118
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• 1999

In order to evaluate strength of spot welded joint, at first it is importent that we should know strain distribution near nugget zone. During loading, in HAZ, compressive strain increase with Increase of load, but in nugget zone tensile strain increase. During unloading, on the other hand, even through the decreases, the strain variation is not almost appeared in nugget zone and HAZ. In nugget boundary zone, the strain range increases continuously along with load increase on outer surface, but the strain increases continunously and decreases rapidly beyond yield strength on inner surface. In this paper, strain distribution are measured in inner and outer surface with variation of thickness and load under tensile-shear load. Tensile-shear strength increased as with increase of specimen thickness. As for thickness increase rates are 25%, 50%, 100%, and 150%, tensile-shear strength in crease rates are 40%, 81%, 130% and 228%.

• 폴리머
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• 제37권2호
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• pp.196-203
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• 2013

Surface modification of meta-aramid fibers was performed by phosphoric acid treatment. Surface morphology and element composition of untreated and treated fibers were analyzed by scanning electron microscope (SEM) and X-ray photoelectron spectroscopy (XPS). Effects of surface modification on the mechanical strength of aramid papers made from meta-aramid fibers and fibrid were investigated. Surface modification conditions were optimized by response surface analysis (RSA). Results show that phosphoric acid treatment increases the surface roughness and oxygen content of aramid fibers. They improve the interface bonding strength between aramid fibers and fibrid, which improves the tensile strength of aramid papers. The results of response surface analysis indicate that the tensile strength of aramid papers increases by 47.5% and reaches the maximum when meta-aramid fibers are treated with 21.1wt% phosphoric acid solution at $39.3^{\circ}C$ for 36.7 min.

• 대한치과보철학회지
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• 제40권4호
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• pp.344-351
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• 2002

The purpose of this study is to compare tensile bond strength between Cr-Co alloy and three denture base resins after surface treatment. Following the manufacturer's instructions, 180 bonded specimens were made from three denture base resins (Lucitone 199. Paladent 20. POSS resin) and three surface treatment methods (sandblasting. metal primer. silicoating) 20 samples were made in each group and a half was ther-mocycled 1000 times between $5^{\circ}C$ and $55^{\circ}C$. The tensile bond strength was measured using an Instron with 5mm/min crosshead speed. Data was analyzed with one-way ANOVA, T-test and Duncan test. The results were as follows : 1. Samples with metal primer coating had significantly high tensile bond strength than the other surface treated groups (p<.05). Significantly low tensile bond strength was shown in sand blasted groups (p<.05). 2. No significant difference was observed in metal primer coating groups before and after ther-mocycling (p>.05) 3. Tensile bond strength was decreased in silicoated samples after thermocycling (p<.05). 4. Of the surface treated groups with metal primer, Lucitone 199 had the greatest bond strength and POSS resin and Paladent 20 were followed (p<.05). 5. Of the surface treated groups with silicoating, POSS resin and Lucitone 199 had greater bond strength than Paladent 20 (p<.05).

• 한국구조물진단유지관리공학회 논문집
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• 제25권3호
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• pp.100-109
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• 2021

본 연구에서는 부식에 의하여 발생하는 표면 단면손상을 고려하여 인위적인 표면 단면손상이 도입된 원형인장 부재의 인장성능 변화를 평가하였다. 인장성능 평가를 위하여 부식수준에 따른 인위적인 단면손상을 손상 폭과 높이를 변화시켜 원형강관 시험체 표면에 도입하였으며, 단면손상 수준에 따른 인장성능 변화를 평가하였다. 인장강도 실험 결과, 원형단면 강관부재의 인장강도는 강관부재의 길이 방향 손상이 아닌 부재 둘레 방향 손상의 영향을 받는 것으로 나타났으며, 부재의 파괴는 손상이 발생한 부재의 최소 단면에서 발생하는 것으로 나타났다. 표면에 불규칙한 손상이 도입된 강관 시험체의 단면조건을 명확하게 평가할 수 없으므로, 단면손상으로 인한 인장강도 변화를 정량적으로 비교하기 위하여 동일 단면 감소효과가 고려된 강관 부재에 대한 비선형 구조해석을 실시하였다. 비선형 구조해석 결과, 실제 부재 표면에 국부적 단면손상이 발생한 부재의 인장강도는 동일 단면 감소효과를 고려한 부재의 인장강도에 비하여 상대적으로 급격하게 저하하는 것으로 평가되었다. 국부부식과 같이 표면에 불규칙한 단면손상이 발생한 부재의 잔존인장성능은 인장시험과 등가손상 단면과 구조해석 결과로부터 평가된 상관계수를 이용하여 평가 및 예측될 수 있을 것이다.

• The Journal of Advanced Prosthodontics
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• 제10권4호
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• pp.259-264
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• 2018

PURPOSE. The purpose of this study was to evaluate the effect of the zirconia surface architecturing technique (ZSAT) on the bond strength between veneering porcelain and zirconia ceramic. MATERIALS AND METHODS. 20 sintered zirconia ceramic specimens were used to determine the optimal surface treatment time, and were randomly divided into 4 groups based on treatment times of 0, 1, 2, and 3 hours. After etching with a special solution, the surface was observed under scanning electron microscope, and then the porcelain was veneered for scratch testing. Sixty 3 mol% yttria-stabilized tetragonal zirconia polycrystal ceramic blocks were used for tensile strength testing; 30 of these blocks were surface treated and the rest were not. Statistical analysis was performed using ANOVA, the Tukey post-hoc test, and independent t-test, and the level of significance was set at ${\alpha}=.05$. RESULTS. The surface treatment of the zirconia using ZSAT increased the surface roughness, and tensile strength test results showed that the ZSAT group significantly increased the bond strength between zirconia and veneering porcelain compared to the untreated group (36 MPa vs. 30 MPa). Optimal etching time was determined to be 2 hours based on the scratch test results. CONCLUSION. ZSAT increases the surface roughness of zirconia, and this might contribute to the increased interfacial bond strength between zirconia and veneering porcelain.

• Steel and Composite Structures
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• 제24권5호
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• pp.635-641
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• 2017

Safety service improvement and development of efficient maintenance strategies for corroded steel structures are undeniably essential. Therefore, understanding the influence of damage caused by corrosion on the remaining load-carrying capacities such as tensile strength is required. In this study, artificial neural network (ANN) approach is proposed in order to produce a simple, accurate, and inexpensive method developed by using tensile test results, material properties and finite element method (FEM) results to train the ANN model. Initially in reproducing corroded model process, FEM was used to obtain tensile strength of artificial corroded plates, for which surface is developed by a spatial autocorrelation model. By using the corroded surface data and material properties as input data, with tensile strength as the output data, the ANN model could be trained. The accuracy of the ANN result was then verified by using leave-one-out cross-validation (LOOCV). As a result, it was confirmed that the accuracy of the ANN approach and the final output equation was developed for predicting tensile strength without tensile test results and FEM in further work. Though previous studies have been conducted, the accuracy results are still lower than the proposed ANN approach. Hence, the proposed ANN model now enables us to have a simple, rapid, and inexpensive method to predict residual tensile strength more accurately due to corrosion in steel structures.

• 한국구조물진단유지관리공학회 논문집
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• 제6권4호
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• pp.201-207
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• 2002

An advanced fiber sheet has been widely used for strengthening of the concrete structures due to its excellent properties such as high strength and light weight. Bond strength is very important in strengthening the concrete structures using an advanced fiber sheet. This research examines the bond behavior between fiber sheet and concrete, investigates the bond strength by the direct pull-out test and the tensile-shear test. To obtain the tensile-shear strength a double-face shear type bond test is conducted. The primary test variables are the types of concrete surface roughness (disk-grinding/chipping) and retrofitting methods (bonding/injection). Thirty specimens were tested to evaluate the bond strength. It is shown that the average bond strength between fiber sheet and concrete by the direct pull-out test and the tensile-shear test is $22.3{\sim}23.1kgf/cm^2$ $17.92{\sim}19.75kgf/cm^2$, respectively.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1997년도 추계학술대회 논문집
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• pp.782-785
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• 1997

In this study, the spectra was surface-treated using $Ar^+$ ion beam to improve the tensile property of spectra/vinylester composites. The effect of surface treatment on the tensile property of spectra/vinylester composites was investigated comparing tensile strength and stiffness of surface-treated spectra/vinylester composites with those of untreated spectra/vinylester composites. The results showed that the tensile strength and stiffness of surface-treated s spectra/vinylester composites were 12% and 22% higher than those of untreated spectra/vinylester composites.

• Journal of Pharmaceutical Investigation
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• 제38권1호
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• pp.1-8
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• 2008

Planetary ball mill was used to decrease and control the particle size of excipients. The effects of the weight of sample and the revolution number of mill, and grinding time on the particle size of the ground sample were analyzed by response surface methodology. The optimum conditions for the milling of microcrystalline cellulose were 38.82 g of the weight of sample and 259 rpm of the revolution number of mill, and 45 minutes of grinding time. The predicted value of the particle size at the these conditions was $19.02{\mu}m$, of which the experimental value at the similar conditions was $18.68{\mu}m$. The tensile strength of tablets of single-component powders, such as microcrystalline cellulose, hydroxypropylmethyl cellulose and starch, binary mixtures and ground binary mixtures of these powder were measured at various relative densities. It was found that the logarithm of the tensile strength of the tablets was proportional to the relative density. A simple model, based upon Ryshkewitch-Duckworth equation that was originally proposed for porous materials, has been developed in order to predict the relationship between the tensile strength and relative density of ground binary tablets based on the properties of the constituent single-component powders. The validity of the model has been verified with experimental results for ground binary mixtures. It has demonstrated that this model can well predict the tensile strength of ground binary mixtures based upon the properties of single-component powders, such as true density, and the compositions. When the tensile strength of the mixture of microcrystalline cellulose hydroxypropylmethyl cellulose (90:10) and the ground mixture of them were compared, the tensile strength of the ground mixture decreased widely from 45.3 to 5.6% compared to the mixture in case the relative density of tablets was in the range of $0.7{\sim}0.9$. When the tensile strength of the mixture of microcrystalline cellulose starch (80:20) and the ground mixture of them were compared, the tensile strength of the ground mixture decreased widely from 31.0 to 11.6% compared to the mixture in case the relative density of tablets was in the range of $0.7{\sim}0.9$.