• Journal of the Korean Society of Industry Convergence
• /
• v.26 no.4_2
• /
• pp.629-637
• /
• 2023

This study aimed to evaluate the effect of post-curing equipment and time on the flexural strength of 3D printing resins produced by a liquid crystal display(LCD) printer. The three 3D printing resins(DENTCA Denture Teeth, DT; C&B 5.0 hybrid, CH; C&B Permanent A2, CP) were divided into four groups according to post-curing time(10 min and 30 min) and equipment with or without vacuum treatment. For the three-point flexural strength test and biaxial strength test were prepared by method according to ISO 10477, ISO 6872, respectively. Flexural strength was measured with universal testing machine. Comparison between post-curing time of each post-curing equipment was analyzed by independent sample t-test and Mann-Whitney U test(α=.05), and comparison between groups according to each 3D printing resin was performed by Kruskal-Wallis test and post-hoc by Bonferroni-Dunn test(α=.05). The flexural strength of the resin post-curing under vacuum was higher than that of the resin post-curing in air. In the comparison according to the post-curing time, in the case of the post-curing equipment without vacuum, the 30 minute curing time showed significantly higher flexural strength than the 10 minute curing time, except for the biaxial flexural strength of CH(P<.05). In the post-curing equipment with vacuum, the three-point flexural strength of all 3D printing resins(DT, CH, and CP) showed a higher value at 30 minute curing time than at 10 minute curing time.

• Journal of the Microelectronics and Packaging Society
• /
• v.18 no.1
• /
• pp.15-21
• /
• 2011

In this study, flexural strength and fracture behavior of silicon die from single crystalline silicon wafer were investigated as a function of thickness. Silicon wafers with various thickness of 300, 200, 180, 160, 150, and 100 ${\mu}m$ were prepared by mechanical grinding and polishing of as-saw wafers. Flexural strength of 40 silicon dies (size: 62.5 mm${\times}$4 mm) from each wafer was measured by four point bending test, respectively. For statistical analysis of flexural strength, shape factor(i.e., Weibull modulus) and scale factor were determined from Weibull plot. Flexural strength reflecting both statistical fracture probability and size (thickness) effect of brittle silicon die was obtained as a linear function of die thickness. Fracture appearance was discussed in relation with measured fracture strength.

• Journal of Technologic Dentistry
• /
• v.33 no.4
• /
• pp.283-289
• /
• 2011

Purpose: The purpose of this study was to evaluate flexural strength of full zirconia crown using block after clinical work. Methods: The three point bending test was used to measure the flexural strength of zirconia block. Statistical analysis was done using the Statistical Package for Social Sciences version 19.0 for Windows. As for the analysis methods, the study used analysis of variance, Tukey's test. Results: The ave Rage value of flexural strengths of WIELAND, Zirkonzahn, Hass, D-MAX were 516.2 MPa, 612.6MPa, 566.2MPa, 744.6MPa. The ave Rage value of Surface Roughness of WIELAND, Zirkonzahn, Hass, D-MAX were 0.39Ra, 0.33Ra, 0.33Ra, 0.47Ra. Conclusion: Flexural strength of zirconia block decreased after clinical work. Flexural strength of zirconia block is equal to or higher than flexural strength of dental metal, so zirconia block can be used as dental material.

• The Journal of Advanced Prosthodontics
• /
• v.4 no.1
• /
• pp.1-6
• /
• 2012

PURPOSE. The aim of this study was to compare the flexural strength of polymethyl methacrylate (PMMA) and bis-acryl composite resin reinforced with polyethylene and glass fibers. MATERIALS AND METHODS. Three groups of rectangular test specimens (n = 15) of each of the two resin/fiber reinforcement were prepared for flexural strength test and unreinforced group served as the control. Specimens were loaded in a universal testing machine until fracture. The mean flexural strengths (MPa) was compared by one way ANOVA test, followed by Scheffe analysis, using a significance level of 0.05. Flexural strength between fiber-reinforced resin groups were compared by independent samples t-test. RESULTS. For control groups, the flexural strength for PMMA (215.53 MPa) was significantly lower than for bis-acryl composite resin (240.09 MPa). Glass fiber reinforcement produced significantly higher flexural strength for both PMMA (267.01 MPa) and bis-acryl composite resin (305.65 MPa), but the polyethylene fibers showed no significant difference (PMMA resin-218.55 MPa and bis-acryl composite resin-241.66 MPa). Among the reinforced groups, silane impregnated glass fibers showed highest flexural strength for bis-acryl composite resin (305.65 MPa). CONCLUSION. Of two fiber reinforcement methods evaluated, glass fiber reinforcement for the PMMA resin and bis-acryl composite resin materials produced highest flexural strength. Clinical implications. On the basis of this in-vitro study, the use of glass and polyethylene fibers may be an effective way to reinforce provisional restorative resins. When esthetics and space are of concern, glass fiber seems to be the most appropriate method for reinforcing provisional restorative resins.

• The Journal of Advanced Prosthodontics
• /
• v.11 no.4
• /
• pp.202-208
• /
• 2019

PURPOSE. Fabrication of zirconia restorations with ideal mechanical properties in a short period is a great challenge for clinicians. The purpose of the study was to investigate the effect of heating rate on the mechanical and microstructural properties of monolithic zirconia. MATERIALS AND METHODS. Forty monolithic zirconia specimens were prepared from presintered monolithic zirconia blanks. All specimens were then assigned to 4 groups according to heating rate as Control, Group $15^{\circ}C$, Group $20^{\circ}C$, and Group $40^{\circ}C$. All groups were sintered according to heating rates with the sintering temperature of $1500^{\circ}C$, a holding time of 90 minutes and natural cooling. The phase composition was examined by XRD analysis, three-point bending test was conducted to examine the flexural strength, and Weibull analysis was conducted to determine weibull modulus and characteristic strength. Average grain sizes were determined by SEM analysis. One-way ANOVA test was performed at a significance level of 0.05. RESULTS. Only tetragonal phase characteristic peaks were determined on the surface of analyzed specimens. Differences among the average grain sizes of the groups were not statistically significant. The results of the three-point bending test revealed no significant differences among the flexural strength of the groups (P>.05). Weibull modulus of groups was ranging from 3.50 to 4.74. The highest and the lowest characteristic strength values were obtained in Group $20^{\circ}C$ and Control Group, respectively. CONCLUSION. Heating rate has no significant effect on the flexural strength of monolithic zirconia. Monolithic zirconia restorations can be produced in shorter sintering periods without affecting the flexural strength by modifying the heating rate.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2006.05b
• /
• pp.57-60
• /
• 2006

The purpose of this study is to assess performance of prepacked DFRCC material compared with the DFRCC material which is made by using general mixing method. From 4r-point bending test, bond strength test and chlorine ion penetration test, flexural stress, -deflection relations, bond strengths, and durability assessment have been obtained. From the experiments, premixed DFRCC shows relatively good performance.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.24 no.2
• /
• pp.111-118
• /
• 2020

In this paper, the flexural creep behavior of hooked-end steel fiber reinforced high-strength concrete was evaluated to investigate the steel fiber content influence on long-term behavior of flexural members. An experimental program consisted of nine prismatic beam specimens with dimensions of 150 × 150 × 600mm reinforced with different contents of steel fiber (0, 0.75 and 1.5% at the volume fraction). To introduce flexural creep loading to notched prismatic beam specimens, a four-point bending test setup was used. The sustained load with 40% of the flexural strength was applied by means of a lever system and controlled by a load cell for 90 days. During sustained loading, crack mouth opening displacement (CMOD) was monitored. Conventional flexural test after creep tests were carried out to evaluate the residual capacity of each specimen. Test results showed that steel fiber content has a significant effect on the flexural creep behavior of high-strength concrete and long-term flexural load with 40% of flexural strength doesn't generate negative effects on the residual capacity of steel fiber reinforced high-strength concrete.

• Journal of the Korean Geotechnical Society
• /
• v.28 no.10
• /
• pp.17-25
• /
• 2012

Shotcrete, rockbolt, and steel rib are installed to support ground after tunnel was excavated. These are important supports for NATM applied tunnels. Recently, lattice girder is increasingly used because it is easily installed. In this study, we developed a new lattice girder by increasing contacting area between spider and rod. To verify the effect of the new lattice girder, the 3-point and 4-point flexural strength tests were carried out for LG-$50{\times}20{\times}30$, LG-$70{\times}20{\times}30$, LG-$95{\times}22{\times}32$. As a result, in case of contacting area, strength of new SGS lattice girder is 17.95% higher than that of original lattice girder. In case of weakness point, strength of new SGS lattice girder is 19.37% higher than that of original lattice girder.

• Journal of Technologic Dentistry
• /
• v.30 no.1
• /
• pp.65-71
• /
• 2008

The use of titanium in the field of dentistry has increased, due to their excellent biocompatibility, appropriate mechanical properties, corrosion-resistance and low price. However, many difficulties with the use of titanium for metal-ceramic crowns remain to be solved. The objective of this study was to evaluate the influence of surface modifications on the bonding characteristics of specific titanium porcelain bonded to cast titanium. The surfaces of Titanium were prepared with 4 test groups, i) sandblasted with particles of different size, ii) sandblasted after treated oxidization and oxidized after sandblast. We observed the bond strength and node aspect of titanium and ceramic, and respect to the methods of modifying surface of titanium by the test of mean roughness of surface, Scanning Electron Microscope, and 3-point flexural bend test. The results show that, 1. The specimens, which treated oxidization after process of sandblast with particles of 50um size, were the better for the bond strength in comparison with other specimen. 2. The specimen with process of sandblasting after oxidization treatment were the better for stability of the bond strength. 3. The wettability of titanium surface affect the bond strength.

• Magazine of the Korea Concrete Institute
• /
• v.11 no.1
• /
• pp.221-230
• /
• 1999

A study was conducted to investigate the flexural behavior of reinforced high-strength concrete beams using Belite cement. In this study, fourteen reinforced Belite and control beams were tested. The major experimental variables are compressive strength(350kgf/$cm^2$ and 600kgf/$cm^2$)of concrete and reinforcement ratios(0.0086~0.0345). They were tested by three point loading method. Comparing with flexural behavior of normal reinforced concrete beams, the investigation were to : (1) determine experimentally the load-displacement relationships and the strain distribution on the section of test beams : (2) determine experimentally the moment-curvature and the load-neutral axis relationship of Belite ; (3) investigate the flexural ductility of Belite ; (4) estimate the ratio of the capacities of nominal moment strength as a function of ACI to as a experiment. From the test results, the flexural behavior of reinforced high-strength concrete beams using Belite cement are similar to flexural behavior of normal reinforced concrete beams.