• 소성∙가공
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• 제18권4호
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• pp.304-309
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• 2009

Quenchable boron steel is a new type of high strength steel to reduce the weight of automobiles and maintain the safety conditions. Quenchable blanks can be hot-stamped and hardened in a water-cooled tool to achieve high strength. In this paper, new alloy for hot stamping is designed based on requirement of mechanical properties and two types of surface coating are investigated in viewpoints of oxidization and exfoliation. An automotive part of center pillar is manufactured by hot-stamping using Al-Si coated sheet. The performance of developed part is compared by static compression test and side impact crash test.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part 1
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• pp.244-245
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• 2006

This paper investigates the characteristic of single-layered and multi-layered compacts made by selective laser sintering using titanium powder (TILOP45 and TILOP150, Sumitomo Titanium Corp.) There were few defects in smooth surface of laser sintered specimen in vacuum as compared to the laser sintered specimen in argon. Maximum tensile strength of singlelayered compact was about 200MPa. Multi-layered compacts show the density of around 75% and the adhesive bonding was not observed between layers, resulted in 70MPa of maximum bending strength and 50MPa of maximum tensile strength.

• Steel and Composite Structures
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• 제11권3호
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• pp.183-205
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• 2011

This paper presents the results of an investigation into the post-buckling behaviour and ultimate strength of imperfect corroded steel plates used in ship and other marine-related structures. A series of elastic-plastic large deflection finite element analyses is performed on randomly corroded steel plates. The effects of general corrosion on both sides of the plates are introduced into the finite element models using a random thickness surface model. The effects on plate compressive strength as a result of parametric variation of the corroded surface geometry are evaluated. A proposal on the effective thickness is concluded in order to estimate the ultimate strength and explore the post-buckling behaviour of randomly corroded steel plates under uniaxial compression.

• Journal of Korean Dental Science
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• 제7권2호
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• pp.49-57
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• 2014

Purpose: To evaluate the effect of different surface treatment methods (yttria-tetragonal zirconia polycrystal [Y-TZP] primers, air-abrasion, and tribochemical surface treatment) on the shear bond strength between (Y-TZP) ceramics and etch-and-rinse non-10-methacryloyloxydecyl dihydrogen phosphate (MDP)-containing resin cements. Materials and Methods: Y-TZP ceramic surfaces were ground flat with 600-grit silicone carbide abrasives paper and then divided into seven groups of ten. They were treated as the following: untreated (control), Monobond Plus (IvoclarVivadent), Z-PRIME Plus (Bisco Inc.), ESPE Sil with CoJet (3M ESPE), air-abrasion, Monobond Plus with air-abrasion, and Z-PRIME Plus with air-abrasion. The surface of Y-TZP specimens was analyzed under a scanning electron microscope (SEM). Non-MDP-containing cements were placed on the surface-treated Y-TZP specimens. After thermocycling, shear bond strength test was performed. Bond strength values were statistically analyzed using one-way analysis of variance and Student-Newman-Keuls multiple comparison test (P<0.05). Result: The Z-PRIME Plus treatment in combination with air-abrasion produced the highest bond strength ($14.94{\pm}1.70MPa$) followed by Monobond Plus combined with air-abrasion ($10.70{\pm}1.71MPa$), air-abrasion ($10.47{\pm}1.60MPa$), ESPE Sil after CoJet treatment ($10.38{\pm}0.87MPa$), Z-PRIME Plus application ($10.00{\pm}1.70MPa$), and then Monobond Plus application ($9.25{\pm}0.86MPa$). The control ($6.70{\pm}1.49MPa$) indicated the lowest results (P<0.05). The SEM results showed different surface morphologies according to surface treatment methods compared with the Y-TZP control. Conclusion: The shear bond strength between the Y-TZP ceramic and the non-MDP-containing resin cement was the greatest when the surface was treated with air-abrasion and MDP-containing Z-PRIME Plus primer.

• Advances in concrete construction
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• 제14권2호
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• pp.115-130
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• 2022

This paper presents an application of the maturation effect on the strength of high-strength concrete which is produced with different origin aggregates. While investigating the maturation effect on HSC 384 specimens were prepared with 22 different origin aggregates. These prepared specimens were subjected to the standard compressive tests which were applied after curing for 2, 7, 28, and 56 days under appropriate conditions. The test results revealed that bright surface-low adherence behavior is valid in normal strength concretes, but is not as effective as expected in high-strength concretes. The application of artificial neural networks (ANNs) to predict 2, 7, 28, and 56 day compressive strength of HSC is also investigated in this paper. An ANN model is built, trained, and tested using the available test data gathered from experimental studies. The ANN model is found to predict 2, 7, 28, and 56 days of compressive strength of high-strength concrete well within the ranges of the input parameters considered. These comparisons show that ANNs have strong potential as a feasible tool for predicting the compressive strength of high-strength concrete within the range of the input parameters considered.

• 펄프종이기술
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• 제42권1호
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• pp.64-73
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• 2010

This study was conducted to modify the surface properties of papers by formation of hydrophobic self-assembled monolayer(SAM) on paper surface with silanes. A base paper I(0.5% AKD) and base paper II(1.0-1.5% AKD) were reacted with silanes(PFDTES, DMDCS, MODDCS) by immersion method and vapor deposition method. Hydrophobic SAMs(contact angle value>$120^{\circ}C$) were obtained on all papers after treatment with $10^{\mu}l$ PFDTES for 15min, with $50^{\mu}l$ DMDCS for 30min, with $50^{\mu}l$ MODDCS for 300min. When applying PFDTES to paper surface, lower silane concentration and shorter reaction time were required, whereas MODDCS with long alkyl chain required the longest reaction time of 300min. The st$\ddot{o}$ckight sizing degree of silane treated papers were increased between 105sec(base paper I) and 130sec(base paper II). The wet tensile strength of PFDTES-treated base papers(I, II) increased by 10-34% after SAM formation. However, the wet tensile strength of the DMDCS-treated base paper(I) was found to decrease from 0.067kN/m to 0.038kN/m; this may due to the cellulose degrading as a result of generated hydrogen chloride when hydroxyl group of cellulose were reacted with DMDCS. No apparent changes of PPS roughness on silane-treated papers are observed. The ATR-IR spectrum showed absorption peak located at 465 and 1200cm-1 which can be assigned to the Si-O-C asymmetric stretching and Si-O-C bonds, respectively.

• Restorative Dentistry and Endodontics
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• 제19권2호
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• pp.447-459
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• 1994

The purpose of this study is to evaluate of shear bond strength of light-curing composite resin to light-curing glass ionomer cement. Composite resin and glass ionomer cement have been widely used as an esthetic filling materials in dental clinics. To achieve better clinical results, sandwich technic was developed with conpensating for disadvantages of these two materials. Especially, light-curing glass ionomer cement provided greately improved bonding strength of teeth or composite resin, and then excellent clinical results can be acquired. In this study, 6 commercial light-curing glass ionomer cements(3 commercial restorative materials : Fuji II LC, Variglass VLC, Vitremer, and 3 commercial lining materials : Fuji Lining LC, Baseline VLC, Vitrebond) were devided two groups. According to manufacturer's appointment, no surface treatment was referred to N groups. Supposing. of clinical practice, surface grinding with water spray at 320 grit sand paper, 40 seconds etching with 37% phosphoric acid, 20 seconds washing, 20 seconds air drying was referred to N groups. Totally 12 experimental groups were devided, and all 120 specimens from 10 specimens of each groups were made. After light-curing composite resin was bonded to light-curing glass ionomer cement, shear bond strength was tested by Instron universal testing machine between glass ionomer cement and composit resin. The data were analyzed statistically by Student's t-test and ANOVA. The obtained results were as follows; 1. In light-curing glass ionomer cement, restorative materials showed higher shear bond strength to composite resin than lining materials(p<0.05). 2. Variglass VLC of restorative material group and Baseline VLC of lining material group have highest shear bond strength to composite resin(p<0.001). 3. In light-curing glass ionomer cement, surface grinding and acid etching reduced shear bond strength to composite resin(p<0.001)}. 4. VGN group 1s highest shear bond strength to composite resin, VBE group is lowest shear bond strength to composite resin(p<0.001).

• 한국펄프종이공학회:학술대회논문집
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• 한국펄프종이공학회 1999년도 Pre-symposium of the 10th ISWPC Recent Advances in Paper Science and Technology
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• pp.227-231
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• 1999

Condebelt drying provides opportunities not only of improving the strength properties and saving of drying energy but also of reducing the basis weight or increasing the utilization of recycled furnishes. In this paper general overview of the Condebelt press drying will be described and the effects of the process variables in Condebelt press drying including drying temperature, pressure, drying time and moisture content of the sheets on the paper properties is discussed. The experiment was performed with a static rig and Korean OCC was used as a principal raw material. Significant improvement in sheet density, compression strength, tensile strength, surface smoothness, etc. was obtained when Condebelt drying was applied. Control of pressure and inlet dryness was found to be very critical in improving sheet properties. Mill experiences from Dong Il Paper Mfg. Co., Ltd is briefly described.

• 펄프종이기술
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• 제46권4호
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• pp.44-53
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• 2014

This research were aimed at developing starches which have high preservability and high bonding strength from corn starch, modified cationic and oxidized corn starches, as compared to the fermented wheat starch. On the lining that attaching the base paper on the back of the work with paste, the coating weight was determined by the solid contents of the paste rather than the viscosity of paste. Adhesive strength and stiffness were also determined by the solid contents of the paste. Corn starch had lower solid contents, higher viscosity, and higher adhesive strength than other starches. In the iodine stain to the surface of peeled base paper off, paste deeply penetrated into the traditional Hanji than modern Hanji. And oxidized starch paste deeply penetrated into the paper layer than the cationic starch.

• 펄프종이기술
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• 제31권1호
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• pp.23-30
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• 1999

The effects of polyelectrolytes and enzyme, alone and in combination, were investigated in OCC recycling system. Four types of the polyelectrolytes based on acrylamide, cationic and anionic monomers were applied to the enzyme-treated KOCC stock to improve the strength and drainage properties of testliner. The polyelectrolytes used in this work were designed in terms of molecular weight and charge density. The water conditions used for recycling were also varied. The results showed that the hydrolytic action of enzyme gave reduced surface area and amorphous region of fiber, and as a result, the cationic polymer was lost apparently its flocculating power due to the reduced bonding site of fiber surface. When the hardness and conductivity of water had been controlled to the conditins of OCC paper mill, the application of amphoteric polyelectrolyte to the enzyme-treated recycled stock was the most effective with respect to the strength and drainage properties of testliner.