• Journal of the Korean Wood Science and Technology
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• 제37권5호
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• pp.465-473
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• 2009

Three failure theories were studied to evaluate the wood strength variation with grain slope. Maximum stress theory, Tsai-Hill theory and Hankinson formula were presented to hypothesize the failure of wood according to grain slope to loading direction. Red pine and Japanese larch were used as materials to simulate failure strength prediction with grain slope. Calculation of strength results was that the strength of wood drops rapidly between parallel to grain orientation (0 degree) and 15 degree grain orientation. The strength of wood with grain orientation were somewhat different at small grain angles among failure theories, and this tendency was due to tension and compression distinction, and shear accounting in each theories. For the above 45 degree grain orientation, the predicted failure strength of wood with grain variation were very close in each failure theories and were useful in assessing failure strength of wood. The applicable these theories should be considered that the wood has different behavior in tension and compression, and this lead to different strength at small grain angles in each theories. Furthermore, reconsideration is needed to assess the failure strength of wood at small grain angles in Hankinson formula and further studies are necessary to accounting for shear behavior at small grain angles.

• Journal of the Korean Wood Science and Technology
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• 제29권2호
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• pp.118-125
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• 2001

본 연구에서는 소나무의 고부가적 이용을 위한 휨가공 특성을 조사하였다. 먼저 휨가공에 영향을 미치는 수종 특성에 대하여 조사하였다. 다음으로 섬유경사각과 휨가공 특성의 관계에 대하여 조사하였다. 시험편은 섬유경사각 $0^{\circ}$, $30^{\circ}$, $45^{\circ}$, $60^{\circ}$, $90^{\circ}$와 치수 $10mm(T){\times}20mm(R){\times}350mm(L)$로 제작하였다. 휨가공 전의 고주파조사 시간은 30, 60, 90, 120초로 하였다. 본 연구의 결과는 다음과 같다. 1. 섬유경사각의 크기는 휨가공에 있어 탄성계수와 높은 상관이 있었으며, 섬유경사각이 커질수록 휨가공 성능이 크게 증가하였다. 2 강도적인 측면을 고려할 때, 지나치게 큰 섬유경사각은 강도가 약하기 때문에 휩가공채의 용도에 따라 적당한 섬유경사각의 크기가 조정되어야 할 것으로 판단되었다. 3. 휨가공성은 수종에 따라 현저하게 차이가 있는 것으로 조사되었고 수종특성이 명백히 존재하였다.

• Journal of the Korean Wood Science and Technology
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• 제31권3호
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• pp.35-41
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• 2003

The mechanical and physical properties of wood are strongly dependent upon the slope of grain. Specially, tensile strength is more severely affected by the slope of grain. Therefore, tension tests were performed on small thin wood samples made from Pinus radiata with varying the slope of grain. Determining the tensile strength for clear thin wood samples the other variabilities associated with material, size, drying, defects, etc were discarded. Slope of grain was measured by the slope of grain indicator and actual slope of grain was also determined by a protractor. Correlation coefficients between machine measured and actual slope of grain for 40 pieces of 2×20 mm, 300 mm long Pinus radiata were 0.84 for wide face measurement. Results also showed that tensile strength and MOE from stress wave tests decreased with increasing the slope of grain. This study did not establish a relationships for tensile strength and MOE from stress wave with slope of grain. However, the trends of MOEs from stress wave test with both slope of grain are agreed well with Hankinson's equation. Predicted tension strength curve by Hankinson's equation was also agreed well with the experimental data over the range from 0 to 13 degrees for slope of grain.

• 한국가구학회지
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• 제22권3호
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• pp.239-243
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• 2011

In this study, the coating properties and surface performance of exotic cherry wood (Prunus serotina) were estimated, reviewing color difference, hardness and abrasion resistibility in order to evaluate probability as construction interior members such as wall and floor. The reduction effect of color difference was represented in the order of water soluble color stain, water soluble transparent stain, and non-coated lumber. However, the tendency of distinct difference according to wood grain pattern was not found. The wavy grain lumber showed better properties in hardness and resistance to abrasion than quarter grain. In conclusion, it was supposed that the application of wavy grain lumber in wall and floor as interior materials would be acceptable in practicality.

• Journal of the Korean Wood Science and Technology
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• 제47권1호
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• pp.40-50
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• 2019

The aim of this study was to investigate the effects of density, temperature, size, and grain direction on measurement of moisture contents (MC) of wood materials non-destructively. The MC of different sizes of solid wood, glulam, and CLT from larch (larix kaempferi, $560kg/m^3$) and pine (pinus koraiensis, $430kg/m^3$) were measured using the dielectric type and resistance type meters. The specimens were conditioned in the environmental chamber to be equilibrium moisture content (EMC) of 12 % and 19 %. When density setting in dielectric type meter was increased from $400kg/m^3$ to $600kg/m^3$, the MCs of specimen (S-L-100-E) were decreased from 13.4 % to 11.3 %. However, when wood group (WG) setting in resistance type meter was changed from WG1 to WG4, the measured MCs were increased from 9.2 % to 12.3 %. When temperature setting in resistance type meters was changed from 0 to $35^{\circ}C$, the MC was decreased from 17.0 % to 13.0 %. The MCs measured by dielectric type meter for larger specimens (S-L-100-E_11.3 %, G-L-240-E_11.7 % and C-L-120-E_12.8 %) were higher than those of small size specimens (S-L-30-E_8.7 %, G-L-150-E_10.3 %, and C-L-90-E_9.7 %). The MCs measured by resistance type meter for larger specimens (G-L-240-E_11.6 % and C-L-120-E_13.3 %) were also higher than those of small size specimens (G-L-150-E_10.4 %, and C-L-90-E_11.8 %). The resistance type meter was not affected by the grain direction but the dielectric type meter were affected by the grain direction. The MC measured by resistance type meter for G-L-120-E perpendicular to grain direction was 11.5 % and the measured MC parallel to grain direction was 11.3 %. The MC measured by dielectric type meter parallel to grain direction (12.1 %) was higher than that measured perpendicular to grain direction (10.7 %).

• Journal of the Korean Wood Science and Technology
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• 제26권1호
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• pp.63-69
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• 1998

This study was carried out to get some basic information on mechanical properties of Korea Lepidobalanus for rational utilization of wood. Five species of Quercus variabilis, Q. aliena, Q. serrata, Q. mongolica, Q. acutissima belong to Lepidobalanus were investigated in this research. Relationship of anatomical characteristics to compression strength parallel to grain was analyzed using stepwise regression technique. All possible combination of 21 independent variables were regressed on compression strength parallel to grain. The summarized results in this study were as follows: I. In the proportion of wood structural elements, the factors that had the greatest influence on compression strength parallel to grain appeared to be proportion of ray in earlywood in Q. variabilis and Q. acutissima, proportion of wood fiber in latewood in Q. aliena and Q. serrata and proportion of vessel in earlywood in Q. mongolica respectively. 2. In the size of wood element and its structure, the factors that had the greatest influence on compression strength parallel to grain were microfibril angle in Q. variabilis, Q. serrata and Q. mongolica and length of wood fiber in Q. aliena and Q. acutissima.

• 한국가구학회지
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• 제25권1호
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• pp.36-44
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• 2014

This study was investigated to sensible characteristic and physical characteristic to estimate value of the craft for Pinus densiflora and Pinus densiflora for. erecta Uyeki wood. The sensual characteristics of wood are evaluated by wood figure, wood grain, odor, and the physical characteristics by weathering, abrasion, surface roughness and hardness. The wood figure of these species were observed at flat grain in the radial section and edge grain in the tangential section. Also, burl's figure was observed in Burl of Pinus densiflora wood. Pinus densiflora for. erecta Uyeki wood had volatile aroma compounds such as Camphene, Thymyl ether, ${\alpha}$-Longipinene, etc. Pinus densiflora wood had volatile aroma compounds such as ${\alpha}$-Longipinene, (+)-Cedrol, etc. The moisture soption, abrasion, hardness and roughness were very different between the two species.

• Journal of the Korean Wood Science and Technology
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• 제49권6호
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• pp.541-549
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• 2021

This paper reports a method to evaluate the residual strength of insect-damaged radiata pine lumber, such as the screw withdrawal strength as a semi-destructive method and a compression parallel to the grain test to assess the density changes after exposure to outdoor conditions. The screw withdrawal strength test was used as a semi-destructive method to estimate the residual density of decayed lumber. A compression parallel to the grain test was applied to evaluate the residual density. Three variables, such as the screw withdrawal strength, compression parallel to the grain, and residual density, were analyzed statistically to evaluate their relationships. The relationship between the residual density and screw withdrawal strength showed a good correlation, in which the screw withdrawal strength decreased with decreasing density. The other relationship between the residual density and compression parallel to the grain was also positively correlated; the compression parallel to the grain strength decreased with decreasing density. Finally, the correlation between the three variables was statistically significant, and the mutual correlation coefficients showed a strong correlation between the three variables. Hence, these variables are closely correlated. The test results showed that the screw withdrawal strength could be used as a semi-destructive method for an in situ estimation of an existing wood structure. Moreover, the method might approximate the residual density and compression parallel to the grain if supplemented with additional data.

• 한국가구학회지
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• 제12권1호
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• pp.21-26
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• 2001

This study was carried out to get some basic information on mechanical properties of Platanus orientalis L. for the rational utilization of this wood. Relationship of anatomical characteristics with compression strength parallel to grain was analyzed using stepwise regression technique. All possible combination of 8 independent variables were regressed on compression strength parallel to grain. The summarized results in this study were as follows: 1. The compression strength parallel to grain increased with the increase of wood fiber length and wood fiber width. The strength, however, decreased with increase of number of pore per $\textrm{mm}^2$ and tangential diameter of pore. 2. The major factors affecting compression strength parallel to grain in heartwood were length of wood fiber and number of pore $per{\;}{\textrm{mm}^2}$ but width of wood fiber and length of vessel element were the important factors in sapwood.

• Journal of the Korean Wood Science and Technology
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• 제41권2호
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• pp.100-104
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• 2013

Bearing occurs by the rotations of members induced from horizontal or vertical load at traditional wooden joint in frame. The bearing between wooden members is not occurring at the whole surface of joint, but occurring only at the particular bearing area. In this study, partial bearing according to the different grain direction was evaluated. The partial compressive strength showed 3 times higher than pure compressive strength perpendicular to grain, 1.5 times higher than parallel to grain and 3.3 times higher than both of them. It is expected that this result can be very importantly applied when evaluating and analyzing the actual behavior of traditional wooden mortise and tenon joint.