• The Journal of Korean Academy of Prosthodontics
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• v.41 no.1
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• pp.89-98
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• 2003

Titanium requires special ceramic system for veneering. Low fusing dental ceramics with coefficients of thermal expansion matching that of titanium have been developed. The purpose of this study was determine the bond strengths between cast and noncast pure titanium and two commercial titanium porcelains, and to compare the results with a conventional nickel-chromium alloy-ceramic system. The bond strengths were determined using a 3-point flexure test. Three-point flexure specimens $25{\times}3{\times}0.5mm$ were prepared After removal of ${\alpha}-case$ layer, they were veneered with $8{\times}3{\times}1mm$ of ceramics at the center of the bar. Specimens were tested in a universal testing machine. Within the limits of this study, the following conclusions were drawn: 1. The bond strengths between pure titanium and two commercial porcelains exceeded th lower limit of the bonding strength value in ISO 9693(25MPa). 2. There was no significant difference between cast and noncast titanium-porcelain bonds. 3. There was no significant difference between two commercial titanium porcelains. 4. The bond strengths of the titanium-porcelain systems ranged from 73% to 79% of that of the Ni-Cr-conventional porcelain system.

• Journal of the Korean Society of Hazard Mitigation
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• v.10 no.2
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• pp.39-46
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• 2010

Concrete strength relationship between various strength properties was presented through experimental data from concretes made from different sources of coarse aggregates and fine aggregates, and different amount of cement contents. In the strength relationship were included compression-flexure, compression-split tension, compression-modulus and flexure-split tension. A total of 61~81 data sets were analyzed while each data set is composed of 3 to 4 experimental test data. Using the proposed strength relations, a procedure to reliably estimate modulus values from the LTPP field test section was suggested. Core specimens were taken from 10 LTPP sections on the expressway as well as 4 sections on the national road. Then compressive strengths and modulus were determined in the lab. Finally concrete modulus was averaged with the estimated values by using the derived relationship and experimental values.

• Computers and Concrete
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• v.11 no.6
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• pp.531-539
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• 2013

An experimental investigation of mechanical properties of jute fiber-reinforced concrete (JFRC) has been reported for making a suitable construction material in terms of fiber reinforcement. Two jute fiber reinforced concretes, called jute fiber reinforced normal strength concrete (JFRNSC) and jute fiber-reinforced high-fluidity concrete (JFRHFC), were tested in compression, flexure and splitting tension. Compressive, flexural and splitting tensile strengths of specimens were investigated to four levels of jute fiber contents by volume fraction. From the test results, Jute fiber can be successfully used for normal strength concrete (NSC) and high-fluidity concrete (HFC). Particularly, HFC with jute fibers shows relatively higher improvement of strength property than that of normal strength concrete.

• Composites Research
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• v.12 no.2
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• pp.82-90
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• 1999

The mechanical properties of generally orthotropic materials are conventionally measured by performing off-axis tensile and flexure tests. However, the inevitable coupling between tension and shear in case of tensile test or bending and twisting in flexure test case induces nonuniform displacement and stress fields. Consequential stress concentration along the boundary of specimens would result in inaccurate modulus and underestimated strength. This paper proposes the variation of specimen geometry in terms of appropriate obliquity of loaded boundary. For the purpose, classical lamination theory is transformed into skewed coordinate, and characteristic equations for both of unidirectional and laminated composite specimens are formulated. Finite element analysis is employed to show the validity of the skewedness in tensile and bending test specimens.

• The Journal of Korean Academy of Prosthodontics
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• v.30 no.1
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• pp.65-72
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• 1992

The purpose of this study was to evaluate the flexure stregth of posterior 4-unit acrylic resin bridge with different pontic designs : 1) Conventional pontic 2) Hygienic pontic and 3) Modified hygienic pontic. All specimens were made of self-curing acrylic resin for provisional restorations. Self-curing acrylic resin was filled in a silicone mold by the drop-on technique ; and was polymerized in a pressure spot under 20 psi pressure. The test specimens which were simply shaped posterior 4-unit bridge were 38mm ion 4mm wide, and 35mm thick(connector : 3mm thick). Each specimen was subjected to an increasing load of Instron machine with its tip centered on the specimen at 90-degree angle, and the machine was operated with its load cell of 50kg and its crosshead speed, 2mm/minute : and then the load values at the moment of the fracture of them were recorded. This study was also performed to analyze their stress distributions by the finite element method. The obtained results were as follows : 1. Flexure strength of the hygienic pontic(9.78kg) and the modified hygienic pontic(10.17kg) was higher than that of conventional pontic(6.96kg). But no significant difference was found between the hygienci pontic and the. modified hygienic pontic. The above statistic values were appraised by ANOVA and Duncan's multiple range test 2. Stress was concentrated on the middle portion in every group : and the stress of conventional pontic was found the greatest of all pontic designs.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.05b
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• pp.301-304
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• 2006

The purpose of this study is to evaluate bonding properties of PMMA mortars using EPS with silane coupling agent. PMMA mortars are prepared with various silane coupling agent, and tested for flexural strength test, adhesion test in flexure and tensile strength in underwater and air. It is estimated that the application of silane coupling agent to PMMA mortar is more effective in underwater than air.

• Journal of the Korean Society of Industry Convergence
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• v.12 no.2
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• pp.107-112
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• 2009

The effective reinforcement methods of structure is required to improve the durability of existing structures. Recently, the continuous fiber sheets to the concrete structures are widely used in the earthquake-proof reinforcement method. This study examines suitability and effect to concrete structure of fiber by FEM analysis. The result of analysis is as follows; All specimens occurred bending tensile failure at the middle span. Ultimate strength of specimen in the RC and reinforced RC specimen were 53.9 kN, 56.3 kN respectively and it was some low by degree 0.89, 0.82 to compare with calculated result. The deflection of specimen at the middle span occurred in approximately 0.2 mm, and did linear behavior in load 20 kN by seat reinforcement. Stiffness did not decrease by occurrence in the finer crack and reinforcement beam's flexure stiffness was increased until reach in failure. To compare calculated value and analysis value, it almost equal behavior in the elastic reign and can confirm effectiveness of analysis. Crack was distributed uniformly by reinforcement of fiber seat at failure and it do not occurred stiffness decreases.

• Steel and Composite Structures
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• v.19 no.3
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• pp.615-633
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• 2015

Composite steel-concrete beams are used frequently in situations where axial forces are introduced. Some examples include the use in cable-stayed bridges or inclined members in stadia and bridge approach spans. In these situations, the beam may be subjected to any combination of flexure and axial load. However, modern steel and composite construction codes currently do not address the effects of these combined actions. This study presents an analysis of composite beams subjected to combined loadings. An analytical model is developed based on a cross-sectional analysis method using a strategy of successive iterations. Results derived from the model show an excellent agreement with existing experimental results. A parametric study is conducted to investigate the effect of axial load on the flexural strength of composite beams. The parametric study is then extended to a number of section sizes and employs various degrees of shear connection. Design models are proposed for estimating the flexural strength of an axially loaded member with full and partial shear connection.

• Korean Journal of Metals and Materials
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• v.47 no.1
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• pp.50-58
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• 2009

In this study, alumina matrix composites reinforced with carbon nanotubes (CNTs) were fabricated by ultrasonic dispersion, ball milling, mixing, compaction, and sintering processes, and their relative density, electrical resistance, hardness, flexure strength, and fracture toughness were evaluated. 0~3 vol.% of CNTs were relatively homogeneously dispersed in the composites in spite of the existence of some pores. The three-point bending test results indicated that the flexure strength increased with increasing volume fraction of CNTs, and reached the maximum when the CNT fraction was 1.5 vol.%. The fracture toughness increased as the CNT fraction increased, and the fracture toughness of the composite containing 3 vol.% of CNTs was higher by 40% than that of the monolithic alumina. According to observation of the crack propagation path after the indentation fracture test, a new toughening mechanism of grain interface bridging-induced CNT bridging was suggested to explain the improvement of fracture toughness in the alumina matrix composites reinforced with CNTs.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2002.03a
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• pp.297-305
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• 2002

As advanced earthquake analysis/design methods such as the nonlinear static analysis are developed, it is required to estimate precisely the cyclic behavior of reinforced concrete members that is characterized by strength, deformability, and capacity of energy dissipation. However, currently, estimation of energy dissipation depends on empirical equations that are not sufficiently accurate, or experiment and sophisticated numerical analysis which are difficult to use in practice. In the present study, nonlinear finite element analysis was performed to investigate the behavioral characteristics of flexure-dominant RC members under cyclic load. The effects of axial force, arrangement of reinforcing bars, and reinforcement ratio on the cyclic behavior were studied. Based on the investigation, a simplified method to estimate the capacity of energy dissipation was proposed, and it was verified by the comparison with the finite element analyses and experiments. The proposed method can estimate the energy dissipation of RC members more precisely than currently used empirical equations, and it is easily applicable in practice.