• Journal of the Korea Furniture Society
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• v.12 no.1
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• pp.47-55
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• 2001

Violin bridge blank cut from maple wood with good quality has typical pattern of the radial direction in the side edge with minimal dispersion. This experimental study was designed and carried out to examine the effect of the physical and macroscopical characteristics on the compressive creep of violin bridge blank which had been imported from European manufacturer. This research arose from the idea that the maple solid wood with heterogeneous wood density and ray direction in the side edge would have uneven rheological property of violin bridge blank which is supposed to be pressed by the tension of strings. Experimentally, the compressive creep of bridge blank became smaller with the higher density of imported maple wood and showed clear density-dependence for the duration of load under the string tension of 5 kgf. Every bridge blank showed the behavior of primary creep stage(stress stabilization) having logarithmic regression creep curve with high correlation coefficient under the designed stress level. Even though the relationship between compressive creep and ray direction on the side edge of bridge was not so clear contrary to expectation, we could conclude that wood density and ray direction should be the quality decisive factors affecting the acoustical characteristics and performance of the bridge, the core member of violin-family bow instruments.

• Journal of the Korean Wood Science and Technology
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• v.37 no.5
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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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• v.18 no.3
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• pp.42-52
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• 1990

In this study, thick 24mm glulams were composed of thick. 3, 4, 6, 8mm Larch laminas to study that the theoretical analysis and the experimental analysis regarding the location of neutral axis of the glulams were compared, and to study on the effect of location of neutral axis on mechanical properties of glulam. The variation of location of neutral axis after proportional limit(or elastical limit) was studied to offer basic data to make the better composition method of glulam. The result obtained can be summarized as follows: 1. The theoretical neutral axis was 0.547 in solid wood, and also 0.547 in glulams because glulams were composed of only Larch laminas. 2. In solid wood, the deviation of the theoretical and the experimental neutral axis location was 0.1%, But in glulams, the deviation from-12.2% to + 7.8% showed nonuniform pattern but no large deviation. Because laminas was only of Larch and so the mechanical properties of laminas were monotonous. 3. The neutral axis exerted no influance on the elasticity of glulam, which meaned that the maximum shear strength in the neutral axis showed no influance on elasticity limit. 4. The only minutely lower elasticities of glulam than that of solid wood were shown. This was because of influance of glue lines of glulam on the elasticlties. 5. The failure type of glulam was wholly simple tension failure and the horizontal shear failure near neutral axis was not taken place, which was that glue line was complete in bonding and the strength of the lamina was not various but uniform. 6. The ratio of tension strain($^{\varepsilon}t$) I compression strain($^{\varepsilon}c$) initially showed uniform level After the elasticity limit. the ratio was increased with the flow of time and so the tension strain was more increased than compression strain. So this proved tension lamination technique, which is that the mechanical properties of glulam could be improved, if the lamina of more superior strength would he added on the bottom side of the glulam.

• Structural Engineering and Mechanics
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• v.17 no.5
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• pp.627-639
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• 2004

The objective of this research was to evaluate the performance of metal-plate-connected truss joints subjected to cyclic loading conditions that simulated seismic events in the lives of the joints. We also investigated the duration of load factor for these joints. We tested tension splice joints and heel joints from a standard 9.2-m Fink truss constructed from $38-{\times}89-mm$ Douglas-fir lumber: 10 tension splice joints for static condition and for each of 6 cyclic loading conditions (70 joints total) and 10 heel joints for static condition and for each of 3 cyclic loading conditions (40 joints total). We evaluated results by comparing the strengths of the control group (static) with those of the cyclic loading groups. None of the cyclic loading conditions showed any strength degradation; however, there was significant stiffness degradation for both types of joint. The results of this research show that the current duration of load factor of 1.6 for earthquake loading is adequate for these joints.

• Journal of the Korean Wood Science and Technology
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• v.14 no.2
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• pp.3-12
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• 1986

The aim of this study is to determine the flexural properties(Modulus of Rupture, Modulus of Elasticity) of Platanus occidentalis L. laminated beams fabricated with 1, 3, 5, 8, 15 lamination and Tension, Compression lamination. The results were as follows: 1. MOR increased with increasing number of lamination in 3, 5, 8, 15-beam and Tension lamination beam. MOR of Compression lamination beam was lower than that of 3-beam, MOR of vertical beam not having Tension or compression lamination was lower than that of horizontal beam, but MOR of vertical beam with tension or compression lamination was same or slightly higher than that of horizontal beam. 2. The allowable working stress showed the same tendency. This stress increased with increasing number of lamination. This value of Tension lamination beam was higher than that of compression lamination beam. 3. MOE of all laminated beams was higher than that of solid beam and Tension lamination beam was higher than that of 3-beam. MOE of Tension lamination beam was higher than that of Compression lamination beam. MOE of all vertical beam was higher than that of horizontal beam except for T-2, T-5, C-3. 4. Most beam failures appeared to begin in tension. These tension failures were classified into Splintering tension, Cross-grained tension, Simple tension, Brittle tension. All test beam failures could be classified into three categories. 1) Tension failure 2) Compression failure 3) Horizontal shear failure.

• Journal of the Korean Wood Science and Technology
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• v.41 no.5
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• pp.425-431
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• 2013

Estimation equations of shear modulus in the plane of laminated veneer lumber (LVL) were compared each other through uniaxial tension test results. The equations - basic elastic equation in the dimensional orthotropic case, Hankinson's formula and empirical equation proposed by Salikis and Falk, were applied to determine the elastic constants at various angles to the grain, which were needed for determination of shear modulus. Tensile elastic modulus of LVL predicted from these equations were compared with test data to evaluate the accuracy of the equation. Tensile elastic modulus rapidly decreased at orientations between 0 and 15 degrees and elastic modulus at grain angles of 15, 30, and 45 degrees overestimated in the presented equations. But the proposed equation by Salikis and Falk showed better prediction, especially at 30, and 45 degrees. This proposed formula would be more useful and practical for estimating of shear modulus of wood composites like LVL to minimize the effect of Poisson's ratio term.

• Journal of the Korean Wood Science and Technology
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• v.19 no.1
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• pp.64-70
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• 1991

In order ot obtain the information on wood quality of the Populus nigra $\times$ maximowiczii the distributions of crystalliferous substancess, ty loses and tension woods were examined through light microscopy or scanning electron microscopy. 1. The crystalliferous subtance, presumably calcium oxalate. partially occurred in vessel elements of heartwood, and sporadically in ray parenchyma, but not in the wood fibers The types of crystalliferous subtances were mainly crystal sand, $2-3{\mu}m$ in diameter. 2. The tyloses arranged in a ladder-like series were sporadically formed in the vessel elements of heartwood. 3. Although the woods were cut from the straightly grown stem without any evident disorientation with respect to gravitational axis, single or group of gelatinous fibers were irregularly distributed among normal wood fibers.

• Journal of the Korean Wood Science and Technology
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• v.31 no.3
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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.

• Journal of Plant Biology
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• v.35 no.3
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• pp.211-217
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• 1992

In order to elucidate the formation of reaction tissues during the transition from primary to secondary growth, the developmental anatomy was conducted in the first internode of Acer sacchan'num seedling in horizontal position. During the transition from primary to secondary growth, tension wood(gelatinous fiber) was gradually developed on the upper side only, And the tension wood formation in the upper side of the horizontal first internode proceeds acropetally from base to apical portion. Some of the anatomical features of tension wood start to be in the primary vascular tissue and a typical tension wood show during the secondary growth, Therefore, the procambium seems to respond to the gravity as well as vascular cambium. For this reason, both procambium and vascular cambium has to regard as the same meristem, On the other hand, the upper side vessels were longer than those of the lower side in the horizontal first internode. The lateral-wall pitting of vessel elements, however, showed no differences between upper and lower sides which have alternate type. The width and height of rayon the upper side of horizontal first internode was larger as compared with the lower side.r side.

• Journal of the Korean Wood Science and Technology
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• v.37 no.1
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• pp.29-36
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• 2009

Recycling of wood wastes or residues is a good solution for a shortage of wood resources and a rise in the price. Shipbuilding wood wastes were almost used to produce the boards by milling. However, considering the economic value and insufficient resource, recycling with milling is dissatisfied method. This study has been carried out to investigate the recycling possibility of shipbuilding wood waste. There are two kinds of shipbuilding wastes: plywood waste and solid waste. From the results of this study, the following conclusions have been made: 1. Bending properties of plywood and laminated plywood lumber were tested by Korean Standard. 2. The main fracture mode of plywood waste and laminated plywood lumber is that of simple tension. 3. The recommended application for the recycling of shipbuilding wood waste are outdoor wood furnishings, indoor wood furnishings and some wooden building construction materials: interior raw material, wooden pallet, siding, paneling, flooring. picnic table, deck components, porch swing, landscaping timbers, residential fencing, patios, and boardwalks etc.