• Proceedings of the Korea Concrete Institute Conference
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• 2003.05a
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• pp.741-744
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• 2003

In this study, the influence of chemical admixture on early strength development of concrete is discussed. According to the results, fluidity with variation of kinds of chemical admixture is lower in the case of acceleration type than in the case of normal type. Setting time of naphthalene acceleration type is shortened by I hour, and that of melamine is nearly same, but that of polycarbonic acid is somewhat retarded in comparison with that of naphthalene normal type. Early compressive strength gains 5MPa in about 18hours regardless of the kinds of chemical admixture. But as time elapses, compressive strength is higher in order of polycarbonic acid, naphthalene and melamine type. The relativity between compressive strength and the rebound value of P-type schmidt hammer is also favorable at early age, and compressive strength of 5MPa is estimated at the rebound value of 22.

• Journal of the Korea Concrete Institute
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• v.12 no.6
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• pp.99-108
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• 2000

The size effect on axial compressive strength in notched concrete specimens was experimentally investigated. Based on the concept of the fracture mechanics and size effect law, theoretical studies for axial compressive failure of concrete were reviewed, and two failure modes of concrete specimens under compression were discussed. In this study, experiments of axial compressive failure, which is one of the two failure modes, was carried out by using cylindrical specimens. Adequate notch length was taken from the experimental result of strength variation based on the notch length. And, by taking various sizes of specimens the size effect on axial compressive strength of concrete was investigated. Also, model equations were suggested by modified size effect law (MSEL). The test results show that size effect appears conspicuously for all series of specimens. Additionally, the effect of initial notch length on axial compressive strength was also apparent.

• Electrical & Electronic Materials
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• v.5 no.4
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• pp.393-399
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• 1992

In order to increase the coupling strength between bisphenol-A type epoxy resin and filler SiO$_{2}$ it was treated to filler with silane coupling agent[KBM-603]. To observe how silane coupling agent effects on dielectric breakdown strength of Epoxy/SiO$_{2}$ compound material, specimens of eight type were made like following. (A-1, A-2), (B-1, B-2), (C-1, C-2), (D-1, D-2) (see 2-2. Specimen) Specimen treated with silane coupling agent had always bigger dielectric breakdown strength than non-treated specimen. Under the influence of silane coupling agent, increment ratio of dielectric breakdown strength at specimen manufactured by hand drill was very bigger than that of specimen inserted spherical electrode. Therefore, as the specimen shape was varied, it was studied on effect that silane coupling agent affects on dielectric breakdown strength of Epoxy/SiO$_{2}$ compound material.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2015.05a
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• pp.73-74
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• 2015

As this study is one related to ultra high strength concrete using crushed coarse limestone aggregates among the series of experiments for improving the economic inefficiency of the ultra high strength concretes used for high rise structures, it has analyzed the flowability of ultra high strength concrete according to the variation of blended fine aggregates. As a result of analyzing the characteristics of fresh concrete, it is determined that the application of ultra high strength concrete would be difficult in case of a mix using blended fine aggregates as lower flowability than the mix using limestone crushed fine aggregate only was shown in all mixes using blended fine aggregates.

• Journal of Ocean Engineering and Technology
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• v.15 no.1
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• pp.85-91
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• 2001

A study for the structural strength analysis on the doubler plate subjected biaxial in-plane compression and shear load has been performed through the systematic evaluation process. In order to estimate the proper static strength of the doubler plate, non-linear elasto-plastic analysis is introduced. Gap element modeling for contact effect between the main plate and the doubler is prepared and nonlinear analysis procedures are illustrated based on MSC/N4W. In addition, some design guides are suggested through the consideration of several important effects such as corrosion of main plate, doubler width, doubler length and doubler thickness. Finally, theses result are compared with a developed design formula based on the buckling strength and general trends. The design guides, according to the variation of design parameters are discussed.

• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.2
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• pp.200-206
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• 1992

The effect of fiber diameter and gauge length on pull-out test for the interfacial properties in fiber reinforced resin composites have been investigated and these results have been arranged as statistical analysis. The fiber and matrix resins used for this study were stainless steel fiber (SUS316) and carbon fiber (high strength type), epoxy and high density polyethylene resin. From this study, it has been found that shear strength are constant regardless of gauge length of pull-out test and coefficient of variation depend on fiber diameter. In addition, it has been found that the interfacial shear strength decreased with the increasing fiber diameter, and in all case, Weibull parameter (m) has approximately 1.2/C.O.V.

• Steel and Composite Structures
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• v.14 no.5
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• pp.473-491
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• 2013

The primary objectives of this paper are to describe the buckling patterns and to determine the squash load of steel plate-concrete (SC) walls. The major variables in this study were the width-thickness (B/t) ratio and yield strength of surface steel plates. Six SC walls were tested, and the results include the maximum strength, buckling pattern of steel plates, strength of headed studs, and behavior of headed studs. Based on the test results, the effects of the B/t ratio on the compressive strength are also discussed. The paper also presents recommended effective length coefficients and discusses the effects of varying the yield strength of the steel plate, and the effects of headed studs on the performance of SC structures based on the test results and analysis.

• Journal of the Korean Society for Heat Treatment
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• v.7 no.2
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• pp.88-95
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• 1994

In order to compare mechanical properties of ausformed martensite with those of marformed martemsite in Fe-30%Ni-0.1%C alloy and to investigate their strengthening mechanisms, ausformed martensite and marformed martensite were prepared by ausforming treatment and marforming treatment respectively. The microstructures were observed and the quantities of retained austenite, hardness, yield strength, ultimate tensile strength and elongation were examined. The strength of ausformed martensite was mainly increased because of the lattice defects inherited from austenite. The ductility of ausformed martensite was constant at the rate of 7-8% by ductile matrix formation of the retained austenite in spite of the increase in strength. The strength of marformed martensite was increased by the increment in dislocation density, the crossing of transformation twin with deformation twin and the mutual crossing of deformation twin. The ductility of mar formed martensite was slightly lower than that of ausformed martensite, but the strength of mar formed martensite was prominently higher.

• Transactions of Materials Processing
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• v.33 no.2
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• pp.123-131
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• 2024

Plastic, the main material of FFF-type 3D printing, exhibits lower strength compared to metal. research aimed at increasing strength is needed for use in various industrial fields. This study analyzed three X-shape infill patterns(grid, lines, zigzag) with similar internal lattice structure. Moreover, tensile test considering weight and printing time was conducted based on the infill line multiplier and infill overlap percentage. The three X-shape infill patterns(grid, lines, zigzag) showed differences in nozzle paths, material usage and printing time. When infill line multiplier increased, there was a proportional increase in tensile strength/weight and tensile strength/printing time. In terms of infill overlap percentage, the grid pattern at 50% and the zigzag and lines patterns at 75% demonstrated the most efficient performance.

• International Journal of Highway Engineering
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• v.20 no.3
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• pp.19-26
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• 2018

PURPOSES : The main purpose of this study is suggest of field bond strength evaluation method for more objective evaluation method through Evaluation of Bond Strength Properties with changing aspect ratio and temperature. METHODS : The evaluation is laboratory bond strength test. Using the core machine, the pull-off test method ; the bond strength test of interface layer the universal testing machine. RESULTS : As a result of the laboratory bond strength evaluation, it was verified that the bond strength by aspect ratio decreases linearly with increasing aspect ratio and the bond strength properties by temperature change existed at high and low temperature condition relative to odinary temperature condition. CONCLUSIONS : According to the results of laboratory bond strength evaluation, the field bond strength evaluation results suggest applying the proposed correction factor (0.8, 1.0, 1.4, 1.9) according to aspect ratio(0.5, 0.1, 1.5, 2.0), For more objective evaluation of the bond strength, it is analyzed that the evaluation value is within $6{\sim}32^{\circ}C$ and the result can be obtained within 5% of the coefficient of variation.