• Proceedings of the Korean Geotechical Society Conference
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• 2000.11a
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• pp.729-736
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• 2000

For nonhomogeneous and anisotropic rocks such as schist, shale, etc, a method to determine the anisotropic elastic constants was proposed. Many authors have investigated in detail the behavior elastic constants of anisotropy rocks(Pinto 1970, Amadei 1983, 1992, Amadei & Savage 1989). They concluded that equations of elastic constants E$_1$, E$_2$ and G$_2$ can be derived from the measured strains in arbitrary three directions. And, modulus of elasticity varies according to the inclination of discontinuity in specimens. If we attach three strain gages in accordance with the directions of anisotropy on the rock specimen under uni-axial compression and diametral compression tests, anisotropy elastic constants can be determined by these equations. With this method, the degree of anisotropy will be easily evaluated by simple laboratory test. This paper presents the results of elastic constants due to the angle of bedding planes of anisotropic rock, such as shale, in uni-axial compression and diametral compression tests

• Tunnel and Underground Space
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• v.30 no.1
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• pp.87-97
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• 2020

Fracture toughness of rock is a constant that can indicate the initiation and propagation of cracks due to blasting, excavation, etc. Scaled model tests have been applied to the behavior of tunnels and the stability of limestone mines. Through the scaled model, damaged zone evaluation due to blasting is also carried out, and the scale factor is not applied to the failure-related factors. In this study, DCT (diametral compression test) and finite element method ATENA2D numerical analysis results were compared to determine whether the scale factor could be applied to the fracture toughness of rock. The theoretical values of the scale factor applied to the fracture toughness of the rock and the DCT test results and the numerical results are 0.21~0.46, 0.40, and 0.99MPa ${\sqrt{m}}$ respectively, so these three values should be considered when determining scale factor. It is necessary to derive a suitable scale factor in consideration of the length, time, and mass to which the scale factor is applied, as well as the values of the scale factor of major design factors such as uniaxial compressive strength and density.

• Tunnel and Underground Space
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• v.7 no.3
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• pp.221-229
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• 1997

Disc-type and ring-type specimens of four different materials were tested to investigate the tensile characteristics and their brief results are presented. Materials tested were marble, granite, cement mortar and plaster. Unizxial tensile strengths are compared with Brazilian and ring test strengths. It was found that Brazilian strengths were usually greater than uniaxial tensile strengths and affected by loading rates. In the ring tests, tensile strengths were generally found to be decreased as relative hole radius being increased. Ring test strengths, however, converged to some value in r$\geq$0.45 of marble, r$\geqq$0.29 of cement mortar and r$\leq$0.5 of plaster specimens. In such range of r, furthermore, transverse cracking of specimens were observed.

• Journal of the Optical Society of Korea
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• v.19 no.6
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• pp.643-648
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• 2015

By comparing the results calculated by atan() and atan2() functions, the correctly estimated region of isoclinic phase map is determined using morphological techniques. The isoclinic phase map is automatically unwrapped in the true phase range -π/2 to π/2. Demonstrations of the method on a disc and a ring under diametral compression are performed. Test results compare well with the theoretical results. Furthermore, the influences of principal stress direction and the range of isoclinic phase upon stress separation are discussed.

• Journal of the Korean Ceramic Society
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• v.36 no.2
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• pp.178-185
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• 1999

For the process control of silicon nitride gelcasting, the composition effect of acryamide system on the viscosity of slip and mechanical property of gelcast green body were investigated. The slip was prepared by ball milling of silicon nitride suspension prepared with acrylamide monomer and polyelectrolyte dispersant after premixing them by attritor. The slip mixed with initiator was vacuum deaired and cast into molds, and then polymerized. The consolidated green body was obtained by drying the gelated slip. The viscosity measument and the diametral compression test was done to evaluate the rheological behaviro of slip and mechanical property of gelcast body, respectively. Experimental results showed that the high solid loading of silicon nitride slip was obtained up to 46 vol% with a low viscosity. The mechanical property of gelcast body mainly increased with increasing the concentration of monomer. The gelcast body was machinable above the ∼3 MPa of tensile strength. The relative density of pressured-sintered body was 98.5% at 1760$^{\circ}C$, 3 h.

• Korean Journal of Materials Research
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• v.10 no.10
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• pp.677-683
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• 2000

Three- and five-layer 3Y-YZP/12Ce- TZP composites prepared by a slip casting method have been char­acterized in terms of mechanical properties. The fracture strength of mutilayer c$\alpha$nposites determined in a diametral compression test was 327~534 MPa. Although the indentation strength of the materials was generally reduced with i increasing Vickers indentation load up to 300 N, the damage resistance of multilayer composites was superior com­pared to monolithic layer TZP material. The four-point bend strength of the layered material remained at the values of 620~674 MPa after indentation with a load of 49 N, while that of the monolithic TZP material was 129~339 MPa. The microindentation toughness of the multilayer material was $7.7~13.1\;MPa{\cdot}m^{1/2}$.