• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2008.05a
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• pp.547-550
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• 2008

Precipitation characteristics of the Fe-36Ni based high strength Invar alloy for power transmission wire was investigated in this study. High strength can be obtained in this alloy through precipitation hardening and strain hardening by cold working. $FactSage{(R)}$ in this study, revealing that equilibrium phases which can be formed are two kind of MC-type precipitates and MoC carbide. The latter stoichiometric carbide was expected to be formed at relatively lower temperature $770^{\circ}C$. High strength above 1000MPa and 40% of elongation were obtained at room temperature in both cases.

• The Journal of Advanced Prosthodontics
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• v.10 no.4
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• pp.308-314
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• 2018

PURPOSE. Plasma activation of hydrophobic zirconia surfaces might be suitable to improve the bond strength of luting materials. The aim of this study was to analyze the influence of nonthermal argon-plasma on the shear bond strength (SBS) between zirconia and different combinations of 10-MDP adhesive systems and luting composites after artificial aging. MATERIALS AND METHODS. Two hundred forty Y-TZP specimens were ground automatically with $165{\mu}m$ grit and water cooling. Half of the specimens received surface activation with nonthermal argon-plasma. The specimens were evenly distributed into three groups according to the adhesive systems ([Futurabond U, Futurabond M, Futurabond M + DCA], VOCO GmbH, Germany, Cuxhaven) and into further two subgroups according to the luting materials ([Bifix SE, Bifix QM], VOCO GmbH). Each specimen underwent artificial aging by thermocycling and water storage. SBS was measured in a universal testing machine. Statistical analysis was performed using ANOVA and $Scheff{\grave{e}}$ procedure with the level of significance set to 0.05. RESULTS. Surface activation with nonthermal plasma did not improve the bond strength between zirconia and the tested combinations of adhesive systems and luting materials. The plasma-activation trended to reveal higher bond strength if the self-etch luting material (Bifix SE) was used, irrespective of the adhesive system. CONCLUSION. Plasma-activation seems to be suitable to improve bond strength between zirconia and self-etch resin materials. However, further research is necessary to identify the influence of varying plasma-parameters.

• Korean Journal of Materials Research
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• v.12 no.10
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• pp.820-824
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• 2002

It is of importance to know that the bonding strength and interfacial stress of SOI wafer pairs to meet with mechanical and thermal stresses during process. We fabricated Si/2000$\AA$-SiO$_2$ ∥ 2000$\AA$-SiO$_2$/Si SOI wafer pairs with electric furnace annealing, rapid thermal annealing (RTA), and fast linear annealing (FLA), respectively, by varying the annealing temperatures at a given annealing process. Bonding strength and interfacial stress were measured by a razor blade crack opening method and a laser curvature characterization method, respectively. All the annealing process induced the tensile thermal stresses. Electrical furnace annealing achieved the maximum bonding strength at $1000^{\circ}C$-2 hr anneal, while it produced constant thermal tensile stress by $1000^{\circ}C$. RTA showed very small bonding strength due to premating failure during annealing. FLA showed enough bonding strength at $500^{\circ}C$, however large thermal tensile stress were induced. We confirmed that premated wafer pairs should have appropriate compressive interfacial stress to compensate the thermal tensile stress during a given annealing process.

• Journal of the Korea institute for structural maintenance and inspection
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• v.1 no.1
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• pp.107-112
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• 1997

A series of reinforced concrete beams was tested to evaluate the flexural performance of the repaired RC beams. The key parameters for this study were the size and location of the patch, and the repair materials, including polymer, polymer-cementitious and cementitious materials. The repaired specimens failed by a typical flexural mode with minor interfacial bond failure. Beams repaired with polymer, polymer-cementitious and cementitious materials recover 100%, 91%, and 97% of the flexural strength respectively, while beams with cement mortar lose approximately 30% of the strength. Compared with the pressure injection techniques the specimens repaired with patching techniques show low flexural strength, with significant interfacial bond failure. Location and size of the repaired part do not affect the recovering performance. Interfacial behavior between repair and strengthening materials is the major influencing factor for the composite structures.

• Korean Journal of Materials Research
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• v.17 no.12
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• pp.664-668
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• 2007

The magnetron sputtering was used to deposit Ni buffer layers on the polyimide surfaces to increase the adhesion strength between Cu thin films and polyimide as well as to prevent Cu diffusion into the polyimide. The Ni layer thickness was varied from 100 to $400{\AA}$. The adhesion strength increased rather significantly up to $200{\AA}$ of Ni thickness, however, there was no significant increase in strength over $200{\AA}$. The XPS analysis revealed that Ni thin films could increase the adhesion strength by reacting with the polar C=O bonds on the polyimide surface and also it could prevent Cu diffusion into the polyimide. The Cu/Ni/ polyimide multilayer thin films showed a high stability even at the high heating temperature of $200^{\circ}C$, however, at the temperature of $300^{\circ}C$, Cu diffused through the Ni buffer layer into polyimide, resulting in the drastic decrease in adhesion strength.

• Korean Journal of Materials Research
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• v.31 no.10
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• pp.546-551
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• 2021

To improve ferroelectric properties of PZT, many studies have attempted to fabricate dense PZT films. The AD process has an advantage for forming dense ceramic films at room temperature without any additional heat treatment in low vacuum. Thick films coated by AD have a higher dielectric breakdown strength due to their higher density than those coated using conventional methods. To improve the breakdown strength, glass (SiO₂-Al₂O₃-Y₂O₃, SAY) is mixed with PZT powder at various volume ratios (PZT-xSAY, x = 0, 5, 10 vol%) and coating films are produced on silicon wafers by AD method. Depending on the ratio of PZT to glass, dielectric breakdown strength and energy storage efficiency characteristics change. Mechanical impact in the AD process makes the SAY glass more viscous and fills the film densely. Compared to pure PZT film, PZT-SAY film shows an 87.5 % increase in breakdown strength and a 35.3 % increase in energy storage efficiency.

• Geomechanics and Engineering
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• v.23 no.5
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• pp.467-480
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• 2020

The failure behavior and tensile strength of sandstone materials under different strain rates are greatly different, especially under static loads and impact loads. In order to clearly investigate the failure mechanism of sandstone materials under static and impact loads, a series of Brazilian disc samples were used by employing green sandstone, red sandstone and black sandstone to carry out static and impact loading splitting tensile tests, and the failure properties subjected to two different loading conditions were analyzed and discussed. Subsequently, the failure behavior of sandstone materials also were simulated by finite element code. The good agreement between simulation results and experimental results can obtain the following significantly conclusions: (1) The relationship of the tensile strength among sandstone materials is that green sandstone < red sandstone < black sandstone, and the variation of the tensile sensitivity of sandstone materials is that green sandstone > red sandstone > black sandstone; (2) The mainly cause for the difference of dynamic tensile strength of sandstone materials is that the strength of crystal particles in sandstone material, and the tensile strength of sandstone is proportional to the fractal dimension; (3) The dynamic failure behavior of sandstone is greatly different from that of static failure behavior, and the dynamic tensile failure rate in dynamic failure behavior is about 54.92%.

• The Journal of Advanced Prosthodontics
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• v.6 no.3
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• pp.224-232
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• 2014

PURPOSE. The purpose of the present study was to evaluate the effect of thermocycling and mechanical loading on the biaxial flexural strength and the phase transformation of one Ce-TZP/$Al_2O_3$ and two Y-TZP core materials. MATERIALS AND METHODS. Thirty disc-shaped specimens were obtained from each material. The specimens were randomly divided into three groups (control, thermocycled, and mechanically loaded). Thermocycling was subjected in distilled water for 10000 cycles. Mechanical loading was subjected with 200 N loads at a frequency of 2 Hz for 100000 times. The mean biaxial flexural strength and phase transformation of the specimens were tested. The Weibull modulus, characteristic strength, 10%, 5% and 1% probabilities of failure were calculated using the biaxial flexural strength data. RESULTS. The characteristic strengths of Ce-TZP/$Al_2O_3$ specimens were significantly higher in all groups compared with the other tested materials (P<.001). Statistical results of X-ray diffraction showed that thermocycling and mechanical loading did not affect the monoclinic phase content of the materials. According to Raman spectroscopy results, at the same point and the same material, mechanical loading significantly affected the phase fraction of all materials (P<.05). CONCLUSION. It was concluded that thermocycling and mechanical loading did not show negative effect on the mean biaxial strength of the tested materials.

• The Journal of Korean Academy of Prosthodontics
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• v.43 no.4
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• pp.478-486
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• 2005

Statement of problem : Fracture and dimensional change of an acrylic resin denture are a rather common occurrence. Purpose : The purpose of this study was to compare differences in dimensional changes and flexural strength of separate maxillary complete dentures after immediate deflasking by injection molding and conventional compression processing. Material and method: To evaluate dimensional stability, the maxillary dentures were fabricated by using different materials and methods. Lucitone 199(Dentsply Trubyte. york, pennsylvania, USA) and Vertex(Dentimex, zeist, Netherlands) were used as materials. Compression and injection packing methods were used as processing methods. The impression surface of the dentures was measured by 3D Scann-ing System(PERCEPTRON USA) and overlapped original impression surface of the master cast. To evaluate flexural strength, resin specimens were made according to the different materials, powder/liquid ratio and processing methods. Flexural strength of the complete resin specimens (64mm$\times$10mm$\times$3.3mm) were measured by INSTRON 4467. (INSTRON, England) The data was analyzed by ANOVA, t-test and Tukey test. (p<.05 level of significance) Result: The results were as follows 1. There was no significant differences between master model and denture base for each group in overall dimensional changes. 2. Palatal area was more stable than flange or alveolar area in dimensional stability. but. there was no significant differences among each area. 3. Materials and power/liquid ratio had an effect on flexural strength. (P<.05) Especially materials was most effective. (P<.05) 4. Lucitone 199(powder/liquid ratio followed by manufacturer's direction) showed higher flexural strength than Vertex. Conclusion : Dimensional stability or flexural strength are affected by materials rather than packing techniques.

• The Journal of Advanced Prosthodontics
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• v.2 no.1
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• pp.14-17
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• 2010

PURPOSE. The purpose of this study was to investigate the diametral tensile strength of polymer-based temporary crown and fixed partial denture (FPD) materials, and the change of the diametral tensile strength with time. MATERIAL AND METHODS. One monomethacrylate-based temporary crown and FPD material (Trim) and three dimethacrylate-based ones (Protemp 3 Garant, Temphase, Luxtemp) were investigated. 20 specimens (${\phi}\;4\;mm\;{\times}\;6\;mm$) were fabricated and randomly divided into two groups (Group I: Immediately, Group II: 1 hour) according to the measurement time after completion of mixing. Universal Testing Machine was used to load the specimens at a cross-head speed of 0.5 mm/min. The data were analyzed using one-way ANOVA, the multiple comparison Scheff$\acute{e}$ test and independent sample t test ($\alpha\;=\;0.05$). RESULTS. Trim showed severe permanent deformation without an obvious fracture during loading at both times. There were statistically significant differences among the dimethacrylate-based materials. The dimethacrylate-based materials presented an increase in strength from 5 minutes to 1 hour and were as follows: Protemp 3 Garant (23.16 - 37.6 MPa), Temphase (22.27 - 28.08 MPa), Luxatemp (14.46 - 20.59 MPa). Protemp 3 Garant showed the highest value. CONCLUSION. The dimethacrylate-based temporary materials tested were stronger in diametral tensile strength than the monomethacrylate-based one. The diametral tensile strength of the materials investigated increased with time.