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Kiwoo Nam - One of the best experts on this subject based on the ideXlab platform.
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Bending Strength and crack healing behavior of al2o3 sic composites ceramics
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2008Co-Authors: Hae Sook Kim, Mi Kyung Kim, Seok Hwan Ahn, Sun Bae Kang, Kiwoo NamAbstract:Five kinds of ceramics were used to evaluate the Bending Strength under three-point Bending. The Bending test was carried out at room temperature. The crack-healing behavior and the Bending Strength of the crack-healed specimens were investigated from room temperature to 1723 K. The Bending Strength of Al 2 O 3 /SiC composite ceramics is higher than that of Al 2 O 3 monolithic. Al 2 O 3 /SiC composite ceramics could completely heal semicircular cracks with diameters 100 μm. The Bending Strength of Al 2 O 3 /SiC composite ceramics significantly increased after heat treatment at 1573 K for 1 h in air. The crack-healing ability of Al 2 O 3 /SiC composite ceramics was the best in additive powder 3 wt.% Y 2 O 3 .
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crack healing behavior and Bending Strength of si3n4 sic composite ceramics by sio2 colloidal
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2007Co-Authors: Kiwoo Nam, Mi Kyung Kim, Seok Hwan Ahn, Sung Won Park, Jong Soon KimAbstract:Abstract Si3N4/SiC composite ceramics were sintered in order to investigate their Bending Strength behavior after crack-healing. Y2O3 and TiO2 powder was added as sintering additives to enhance it's sintering property. A three-point Bending specimen was cut out from sintered plates. About 100 μm semi-circular surface cracks were made on the center of the tension surface of the three-point Bending specimen using Vickers indenter. After the cracked specimen with SiO2 colloidal coating healed from 500 to 1300 °C for 1 h in air, the Bending Strength behavior was carried out systematically at room temperature. Si3N4/SiC ceramics using additive powder (Y2O3 + TiO2) were superior to that of additive powder Y2O3. The additive powder TiO2 exerted influence at growth of Si3N4. The optimum crack-healing conditions coated SiO2 colloidal were 1000 and 1300 °C at Si3N4/SiC using additive powder (Y2O3 + TiO2) and Y2O3, respectively.
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Bending Strength of si3n4 monolithic and si3n4 sic composite ceramics and elastic wave characteristics by wavelet analysis
International Journal of Modern Physics B, 2006Co-Authors: Kiwoo Nam, Mi Kyung Kim, Hae Sook Kim, Jin Wook Kim, Seok Hwan AhnAbstract:This paper describes the investigation of Bending Strength and elastic wave signal characteristics of Si3N4 monolithic and Si3N4/SiC composite ceramics with crack healing ability. The elastic wave signals, generated during the compression load by a Vickers indenter on the brittle materials, were recorded in real time, and the AE signals were analyzed by the time-frequency analysis method. The three-point Bending test was performed on the Si3N4 monolithic and Si3N4/SiC composite ceramic specimens with/without crack-healed. Consequently the Bending Strength of the crack-healed specimens at 1300°C was completely recovered up to that of the smooth specimens. And the frequency properties of crack-healed specimens tended to be similar to the distribution of the dominant smooth specimens frequency. This study suggests that the results of the signal information for the anisotropic ceramics show a feasible technique to guarantee structural integrity of a ceramic component.
Ayhan Özçifçi - One of the best experts on this subject based on the ideXlab platform.
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Effects of scarf joints on Bending Strength and modulus of elasticity to laminated veneer lumber (LVL)
Building and Environment, 2007Co-Authors: Ayhan ÖzçifçiAbstract:Abstract The role of geometry on the mechanical performance of scarf joints in laminated veneer lumber (LVL) bonded with phenol formaldehyde and melamine formaldehyde (MF) adhesives was investigated. Model joints consists of 3, 4 and 5 mm veneer thicknesses at 30°, 45° and 60° of varying scarf joints for LVL produced from brutia pine ( Pinus brutia Ten ) and elm ( Ulmus compestris l.) woods. However, there is little information available concerning the Bending Strength and modulus of elasticity for LVL, and in particular, scarf joints in these field. In this study, it was aimed to determine the Bending Strength and modulus of elasticity for LVL. For this purpose, samples were tested according to TS EN 310 standard. It was observed that the highest Bending Strength (291.5 N/mm 2 ) and modulus of elasticity (28 101 N/mm 2 ) were obtained in control (solid wood) samples having three layered LVL, jointed with 30° angle and bonded with MF adhesive. As a result of the effects scarf joints on Bending Strength and modulus elasticity test, if the scarf angle decreases, the properties of LVL increase.
Ozan Uzunkavak - One of the best experts on this subject based on the ideXlab platform.
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the effects of ply organization and loading direction on Bending Strength and modulus of elasticity in laminated veneer lumber lvl obtained from beech fagus orientalis l and lombardy poplar populus nigra l
Construction and Building Materials, 2007Co-Authors: Erol Burdurlu, Murat Kilic, Abdullah Cemil Ilce, Ozan UzunkavakAbstract:Abstract The effects of ply organization and loading direction on Bending Strength and modulus of elasticity in laminated wood materials produced from 3 mm thick veneers, of beech ( Fagus orientalis L.) and lombardy poplar ( Populus nigra L.) placed one on top of the other in various arrangements were examined in this study. Kleiberit 303 (PVAc), a vinyl (polyvinyl acetate – PVAc) based glue was used in lamination. Eight hundred samples were prepared in order to measure oven-dry specific gravity, Bending Strength and modulus of elasticity values perpendicular and parallel to the glue line of a total of 10 different arrangements, eight of which have different laminated ply organizations, namely (AAAAAAA) (7A), (BBBBBBB) (7B), (ABBBBBA), (ABABABA), (AABBBAA), (AABABAA), (ABBABBA), (BABABAB), in which (A) represents beech wood and (B) represents poplar wood and the other two, which consist of solid beech and solid poplar wood in same dimensions as control samples. The samples were subjected to tests perpendicular and parallel to the glue line in accordance with the ISO 16978 standard. As a result of statistical analysis of the data obtained from the tests, the Bending Strength and modulus of elasticity values of solid woods both perpendicular and parallel to the glue line were observed to be smaller than those values of laminated woods made of the same species of woods. It was also observed that as contribution rate of beech in lamination increases, the Bending Strength and modulus of elasticity values increase.
Bo Källsner - One of the best experts on this subject based on the ideXlab platform.
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prediction of timber Bending Strength and in member cross sectional stiffness vartiation on basis of local wood fibre orientation
European Journal of Wood and Wood Products, 2013Co-Authors: Anders Olsson, Jan Oscarsson, Marie Johansson, Bo Källsner, Erik Serrano, Bertil EnquistAbstract:Machine Strength grading of structural timber is based upon relationships between so called indicating properties (IPs) and Bending Strength. However, such relationships applied on the market today are rather poor. In this paper, new IPs and a new grading method resulting in more precise Strength predictions are presented. The local fibre orientation on face and edge surfaces of wooden boards was identified using high resolution laser scanning. In combination with knowledge regarding basic wood material properties for each investigated board, the grain angle information enabled a calculation of the variation of the local MOE in the longitudinal direction of the boards. By integration over cross-sections along the board, an edgewise Bending stiffness profile and a longitudinal stiffness profile, respectively, were calculated. A new IP was defined as the lowest Bending stiffness determined along the board. For a sample of 105 boards of Norway spruce of dimension 45 × 145 × 3,600 mm³, a coefficient of determination as high as 0.68–0.71 was achieved between this new IP and Bending Strength. For the same sample, the coefficient of determination between global MOE, based on the first longitudinal resonance frequency and the board density, and Strength was only 0.59. Furthermore, it is shown that improved accuracy when determining the stiffness profiles of boards will lead to even better predictions of Bending Strength. The results thus motivate both an industrial implementation of the suggested method and further research aiming at more accurately determined board stiffness profiles.
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prediction of timber Bending Strength and in member cross sectional stiffness vartiation on basis of local wood fibre orientation
European Journal of Wood and Wood Products, 2013Co-Authors: Anders Olsson, Jan Oscarsson, Marie Johansson, Bo Källsner, Erik Serrano, Bertil EnquistAbstract:Machine Strength grading of structural timber is based upon relationships between so called indicating properties (IPs) and Bending Strength. However, such relationships applied on the market today ...
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Prediction of timber Bending Strength on basis of Bending stiffness and material homogeneity assessed from dynamic excitation
Wood Science and Technology, 2012Co-Authors: Anders Olsson, Jan Oscarsson, Marie Johansson, Bo KällsnerAbstract:The potential of utilizing resonance frequencies corresponding to edgewise Bending modes for predicting the Bending Strength of timber is investigated. The research includes measurements of axial and transversal resonance frequencies, laboratory assessment of density, static Bending stiffness and Bending Strength of 105 boards of Norway spruce of dimensions 45 × 145 × 3,600 mm³. It is shown that E _ b,1 , (MOE based on the resonance frequency of the first Bending mode) gives a higher coefficient of determination to the Bending Strength than what E _ a,1 (MOE based on the first axial resonance frequency) does. It is also shown that resonance frequencies corresponding to higher Bending modes can be used in the definition of a new indicating property, the measure of inhomogeneity (MOI). This is a scalar value representing the lack of fit between the true, measured resonance frequencies and the expected (assuming homogeneity) resonance frequencies of a board. The results show that using the MOI as a third indicating property, in addition to E _ b,1 and density, increases the coefficient of determination with respect to Bending Strength from R ^2 = 0.69 to R ^2 = 0.75.
Seok Hwan Ahn - One of the best experts on this subject based on the ideXlab platform.
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Bending Strength and crack healing behavior of al2o3 sic composites ceramics
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2008Co-Authors: Hae Sook Kim, Mi Kyung Kim, Seok Hwan Ahn, Sun Bae Kang, Kiwoo NamAbstract:Five kinds of ceramics were used to evaluate the Bending Strength under three-point Bending. The Bending test was carried out at room temperature. The crack-healing behavior and the Bending Strength of the crack-healed specimens were investigated from room temperature to 1723 K. The Bending Strength of Al 2 O 3 /SiC composite ceramics is higher than that of Al 2 O 3 monolithic. Al 2 O 3 /SiC composite ceramics could completely heal semicircular cracks with diameters 100 μm. The Bending Strength of Al 2 O 3 /SiC composite ceramics significantly increased after heat treatment at 1573 K for 1 h in air. The crack-healing ability of Al 2 O 3 /SiC composite ceramics was the best in additive powder 3 wt.% Y 2 O 3 .
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crack healing behavior and Bending Strength of si3n4 sic composite ceramics by sio2 colloidal
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2007Co-Authors: Kiwoo Nam, Mi Kyung Kim, Seok Hwan Ahn, Sung Won Park, Jong Soon KimAbstract:Abstract Si3N4/SiC composite ceramics were sintered in order to investigate their Bending Strength behavior after crack-healing. Y2O3 and TiO2 powder was added as sintering additives to enhance it's sintering property. A three-point Bending specimen was cut out from sintered plates. About 100 μm semi-circular surface cracks were made on the center of the tension surface of the three-point Bending specimen using Vickers indenter. After the cracked specimen with SiO2 colloidal coating healed from 500 to 1300 °C for 1 h in air, the Bending Strength behavior was carried out systematically at room temperature. Si3N4/SiC ceramics using additive powder (Y2O3 + TiO2) were superior to that of additive powder Y2O3. The additive powder TiO2 exerted influence at growth of Si3N4. The optimum crack-healing conditions coated SiO2 colloidal were 1000 and 1300 °C at Si3N4/SiC using additive powder (Y2O3 + TiO2) and Y2O3, respectively.
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Bending Strength of si3n4 monolithic and si3n4 sic composite ceramics and elastic wave characteristics by wavelet analysis
International Journal of Modern Physics B, 2006Co-Authors: Kiwoo Nam, Mi Kyung Kim, Hae Sook Kim, Jin Wook Kim, Seok Hwan AhnAbstract:This paper describes the investigation of Bending Strength and elastic wave signal characteristics of Si3N4 monolithic and Si3N4/SiC composite ceramics with crack healing ability. The elastic wave signals, generated during the compression load by a Vickers indenter on the brittle materials, were recorded in real time, and the AE signals were analyzed by the time-frequency analysis method. The three-point Bending test was performed on the Si3N4 monolithic and Si3N4/SiC composite ceramic specimens with/without crack-healed. Consequently the Bending Strength of the crack-healed specimens at 1300°C was completely recovered up to that of the smooth specimens. And the frequency properties of crack-healed specimens tended to be similar to the distribution of the dominant smooth specimens frequency. This study suggests that the results of the signal information for the anisotropic ceramics show a feasible technique to guarantee structural integrity of a ceramic component.