• Journal of the Korea institute for structural maintenance and inspection
• /
• v.18 no.6
• /
• pp.41-49
• /
• 2014

In order to investigation splitting bond strength of the deformed longitudinal reinforcing bars in the R C members strengthened laterally with the external steel-band, a total 9 sets of test re-bars with and without active confining force given by the external steel-band are pulled monotonically until failure. Test results indicate that the bond strength becomes higher with the increase in number of steel-band sets and their initial stress magnitude. This is due to the active confining force given by the steel-band, and passive confining forces given by the steel-band and transverse reinforcements, in which the passive confinement effect varies depending on the magnitude of active confining force. An equation to estimate the splitting bond strengths for the R C members strengthened laterally with the external steel-band is developed based on the several experimental results of the present study.

• Journal of the korean academy of Pediatric Dentistry
• /
• v.23 no.2
• /
• pp.489-501
• /
• 1996

This study was to evaluate shear bond strength of fluoride-releasing sealant and nonfluoride releasing sealant to enamel surface of bovine tooth. 80 extracted bovine teeth were randomly assigned to four groups, and four kinds of sealants including Teethmate-A(Kuraray Co.), Teethmate-F(Kuraray Co.), Helioseal(Vivadent Co.), Helioseal-F(Vivadent Co.) were bonded to exposed enamel surfaces using silicon plate. Shear bond strength was determined in an instron universal testing machine at a crosshead speed of 1mm/min. Then, the fracture surfaces of test specimens were investigated with scanning electron microscope. The obtained results were as follows; 1. The shear bond strength decreased in the following order : Teethmate-A(18.31MPa), Teethmate-F(11.90MPa), Helioseal (11.74 MPa), Helioseal-F(10.64MPa). 2. The shear bond strength of Teethmate-A showed significantly higher than that of Teethmate-F(P<0.05), but Helioseal and Helioseal-F didn't showed statistically different(P<0.05). 3. According to the SEM, Teethmate-A group showed cohesive failure, and Teethmate-A group & Helioseal group showed mixed pattern of cohesive and adhesive failure and Helioseal-F group showed adhesive failure.

• The Journal of Korean Academy of Prosthodontics
• /
• v.43 no.2
• /
• pp.149-157
• /
• 2005

Statement of problem. Dental ceramics exhibit excellent esthetic property, compressive strength, chemical durability biocompatibility and translucency. However, it suffers from inherent brittle fractures. Various techniques and materials for intraoral porcelain repair has been suggested. Purpose. This study is to compare the tensile bond strength of four commonly used porcelain repair systems (Vivadent, Bisco, Ulttadent, Voco) and to insure the best system for the clinical application to the fractured porcelain. Materials and methods. A total of fifty specimens were fabricated. Specimens were stored in $37^{\circ}C$ distilled water for 7 days and thermocycling was performed(1000 cycles), and subjected to a tensile force parallel to the repair resin and porcelain interface by use of an Universal Testing Machine. Result. 1. Voco showed the highest tensile bond strength. In decreasing order, the tensile bond strength of the other materials was as follows : Ultradent, Bisco, Vivadent. 2. There was a statistically significant difference between the porcelain repair systems(Voco, Ultradent > Bisco, Yivadent) (p<0.05). 3. SEM examination of prepared porcelain surfaces revealed that the surface treated with Voco showed brittle fracture. However, Ultradent, Bisco and Vivadent showed ductile fracture. 4. All specimens treated with four porcelain repair systems showed adhesive failure between porcelain and composite resin.

• Journal of the Korean Chemical Society
• /
• v.17 no.4
• /
• pp.247-255
• /
• 1973

The self supported film specimen of Wyoming montmorillonite as a layer silicate saturated by cations,$Li^{+},\;Na^{+},\;K^{+},\;Ca^{2+},\;Ni^{2+},\;Al^{3+}$and$F^{3+}$ were allowed to contact acetone, methyl-ethyl ketone and diethyl ketone within the heatable gas cell. The i.r. spectra between $4000{\sim}1200cm^{-1}$ at different pressures of adsorbates indicated bond formation through carbonyl oxygen. Two types of carbonyl bond shift with maxima at $1713cm^{-1}$ and $1690cm^{-1}$ are attributed as coordinate bond formation of carbonyl with either surface hydroxyl or cationic hydroxyl group. The intensity of the vOH was analyzed and resonance form of cationic hydroxyl was proposed as an adsorption site. The tendency to form coordinate bond was in good agreement with calculated formal charge of carbonyl oxygen in an increasing order, acetone < methyl-ethyl ketone < diethyl ketone. As an additional mechanism of adsorption, weak hydrogen bonding of methyl hydrogen with surface oxygen was observed.

• The Journal of Advanced Prosthodontics
• /
• v.11 no.2
• /
• pp.95-104
• /
• 2019

PURPOSE. To evaluate the effect of surface treatments and repair materials on the shear bond strength and to measure the fracture toughness of CAD/CAM provisional restoration materials. MATERIALS AND METHODS. Four CAD/CAM (3D printing: Nextdent C&B and ZMD-1000B Temporary, CAD/CAM resin block: Yamahachi PMMA disk and Huge PMMA block) and four conventional (monometacrylate: Jet and Alike, dimetacrylate: Luxatemp and Protemp 4) materials were selected to fabricate disk-shaped specimens and divided into six groups according to surface treatment (n=10). CAD/CAM materials were repaired with Jet or Luxatemp, while conventional materials were repaired with their own materials. The shear bond strength was measured by using universal testing machine. Ten rectangular column-shaped specimens for each material were fabricated to measure the fracture toughness by single edge v notched beam technique. Statistical analysis was performed by one-way ANOVA. RESULTS. The highest shear bond strength of CAD/CAM materials was achieved by SiC paper + sandblasting. It was also accomplished when repairing 3D printing materials with Luxatemp, and repairing CAD/CAM resin blocks with Jet. Yamahachi PMMA disk showed the highest fracture toughness. Nextdent C&B showed the lowest fracture toughness value but no statistically significant difference from Alike and Luxatemp (P>.05). CONCLUSION. In order to successfully repair the CAD/CAM provisional restoration, mechanical surface treatment and appropriate repair material according to the CAD/CAM material type should be selected. The CAD/CAM provisional materials have proper mechanical properties for clinical use as compared to conventional materials.

• Journal of IKEEE
• /
• v.26 no.4
• /
• pp.537-544
• /
• 2022

This paper analyzes the occurrence and cause of bond wires fusing used in the manufacture of pulsed high power amplifiers. Recently GaN HEMT has been spotlight in the fields of electronic warfare, radar, base station and satellite communication. In order to produce the maximum output power, which is the main performance of the high-power amplifier, optimal impedance matching is required. And the material, diameter and number of bond wires must be determined in consideration of not only the rated current but also the heat generated by the transient current. In particular, it was confirmed that compound semiconductor with a wide energy band gap such as GaN trigger fusing of the bond wire due to an increase in thermal resistance when the design efficiency is low or the heat dissipation is insufficient. This data has been simulated for exothermic conditions, and it is expected to be used as a reference for applications using GaN devices as verified through IR microscope.

• Steel and Composite Structures
• /
• v.51 no.5
• /
• pp.509-527
• /
• 2024

Bonding carbon fiber-reinforced polymer (CFRP) laminates have been extensively employed in the restoration of steel constructions. In addition to the mechanical properties of the CFRP, the bond strength (P_U) between the CFRP and steel is often important in the eventual strengthened performance. Nonetheless, the bond behavior of the CFRP-steel (CS) interface is exceedingly complicated, with multiple failure causes, giving the P_U challenging to forecast, and the CFRP-enhanced steel structure is unsteady. In just this case, appropriate methods were established by hybridized Random Forests (RF) and support vector regression (SVR) approaches on assembled CS single-shear experiment data to foresee the P_U of CS, in which a recently established optimization algorithm named Aquila optimizer (AO) was used to tune the RF and SVR hyperparameters. In summary, the practical novelty of the article lies in its development of a reliable and efficient method for predicting bond strength at the CS interface, which has significant implications for structural rehabilitation, design optimization, risk mitigation, cost savings, and decision support in engineering practice. Moreover, the Fourier Amplitude Sensitivity Test was performed to depict each parameter's impact on the target. The order of parameter importance was t_c> L_c > E_A > t_A > E_c > b_c > f_c > f_A from largest to smallest by 0.9345 > 0.8562 > 0.79354 > 0.7289 > 0.6531 > 0.5718 > 0.4307 > 0.3657. In three training, testing, and all data phases, the superiority of AO - RF with respect to AO - SVR and MARS was obvious. In the training stage, the values of R² and VAF were slightly similar with a tiny superiority of AO - RF compared to AO - SVR with R² equal to 0.9977 and VAF equal to 99.772, but large differences with results of MARS.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.36 no.1
• /
• pp.39-47
• /
• 2016

Repair methods of aging concrete pavement are generally used composite structure pavements, such a composite structure is subjected to a large impact on the mechanical behavior and ensure long-term commonality integrated under vehicle loads, environmental loads of the public in accordance with the bond strength between old and new concrete. A common of bonded concrete overlays that are currently available is Interface arrangements using a variety of equipment to ensure the excellent bond strength between old and new concrete than standard concrete, mixed with a material such as a polymer in order to improve the adhesion with the material itself. However, these method of constructions are being applied, depending on the developer site presents no special specifications apply when a specific application criteria objectively, this is due to the situation of each individual method, which is based on the difficulty in quality control of the site manager. In this study by performing a field test for polymer content via the variables that contribute most significantly to ensure bond strength and the field element core of the interface processing method and materials to ensure bond strength between the old and the new concrete, it was to derive the construction site construction method that can improve the performance of the bond strength through a review of the construction around the correlations and the bond strength according to the effective performance analysis of the conventional surface treatment process and variation of polymer volume fraction.

• Journal of Technologic Dentistry
• /
• v.33 no.4
• /
• pp.349-357
• /
• 2011

Purpose: In this study, for the reasons of observing the changes when using bonding agent with Ni-Cr alloy and Co-Cr alloy and using VM13 and Vintage MP ceramic which have the disparity in coefficient of thermal expansion, it is carried out to evaluate the characteristics of the bonding agent through the analysis of the interface between metal and ceramic and the analysis of bond strength by variable. Methods: The surface treatment was performed on the two kinds of alloy(Ni-Cr alloy and Co-Cr alloy) specimens, which were sandblasted and were treated with bonder application. The metal-ceramic interfaces were analyzed with EPMA in order to ionic diffusion, and the shear test was performed. Results: As a result of observation of metal-ceramic interfacial properties, it was observed that Cr atoms were spread from the alloy body to the ceramic floor in the specimen of Group B. It was also seen that Cr, W atoms were spread from the alloy body to the ceramic floor in the specimen of Group S. In consequence of observing Shear bond strength, it was calculated that the specimen of BSV was 27.75(${\pm}11.21$)MPa, BSM was 27.02(${\pm}5.23$)MPa, BCV was 30.20(${\pm}5.99$)MPa, BCM was 27.94(${\pm}10.76$)MPa, SSV was 20.83(${\pm}2.58$)MPa, SSM was 23.98(${\pm}3.94$)MPa, SCV was 32.32(${\pm}4.68$)MPa, and SCM was 34.54(${\pm}10.63$)MPa. Conclusion: In the metal-ceramic interface of Bellabond plus sample group, diffusion of Cr atoms was incurred and diffusion of C Cr atoms and W atoms in the sample group of $Starloy{(R)}\;C$ was observed. Using bonding agent showed the higher bond strength than using the sand blasting treatment. In the Bellabond plus alloys, the specimen group with the use of binding materials showed higher shear bond strength, but didn't show statistically significant differences (p>0.05). In the $Starloy{(R)}\;C$ alloys, the specimen group with the use of binding materials showed higher shear bond strength and statistically significant differences(p<0.05). In terms of VM13 ceramic, it was in the Bellabond plus alloys that the high shear bond strength was showed, but there's no statistically significant differences(p>0.05). In terms of Vintage MP ceramic, it was in the $Starloy{(R)}\;C$ alloys that the high shear bond strength was showed and statistically significant differences(p<0.05). Metal-ceramic to fracture of the shear strength measurements and an analysis of all aspects of military usage fracture of the composite, respectively.

• Restorative Dentistry and Endodontics
• /
• v.27 no.5
• /
• pp.493-501
• /
• 2002

This study evaluated the microleakage performance of four self-etcing primer adhesives(Clearfil SE Bond, Clearfil Liner Bond 2, UniFil Bond, and FL Bond) and one self-etching adhesive(Prompt L-Pop). Class V cavity preparations with occlusal margins in enamel and gingival margins in dentin were prepared on both buccal and lingual surfaces of 50 extracted human molar teeth. Prepared teeth were randomly divided into five groups and restored using one of five adhesives and composite resins: Prompt L-Pop/Filtek Z 250(Group 1), Clearfil SE Bond/Clearfil AP-X(Group 2), Clearfil Liner Bond 2/Clearfil AP-X(Group 3), UniFil Bond/UniFil F(Group 4), and FL Bond/Filtek Z 250(Group 5). Following one day storage in room temperature water, the restored teeth were thermocycled for 500 cycles between 5$^{\circ}C$ and 55$^{\circ}C$. Marginal microleakage was assessed by dye penetration using 2% methylene blue dye. After 24 hours, the teeth were sectioned longitudinally and evaluated for microleakage under steromicroscope The data were statistically analysed by Kruskal-Wallis Test, Mann-Whitney and Wilcoxon signed ranked tests. The results of this study were as follows ; 1. The microleakges at both enamel and dentinal mal$.$gins were the lowest in group 4. increasing among groups in the following order: group 2, follwed by group 5, follwed by group 1, and the highest in group 3. 2. At the enamel margins, the microleakage of group 3 was significantly higher than those of groups 2. 4 and 5(p<0.05), and also the microleakage of group 1 was statistically higher than those of groups 2 and 5(p<0.05). 3. At the dentinal margins, microleakage of group 3 was signincantly higher than microleakages of groups 1, 2, 4 and 5(p<0.05). 4. Compared with microleakages between the enamel and dentinal margins of each group, groups 1, 4 and 5 at enamel margin and group 2 and group 3 at dentinal margin were higher microleakage. But there was no significant difference between enamel and dentinal microleakages of each group(p>0.05).