• 한국가구학회지
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• 제12권1호
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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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• 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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• 제18권3호
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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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• 제17권5호
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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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• 제14권2호
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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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• 제41권5호
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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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• 제19권1호
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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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• 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.

• Journal of Plant Biology
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• 제35권3호
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• pp.211-217
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• 1992

본 연구는 중력자극에 대하여 식물체의 일기생장으로부터 이어지는 이기생장 중에 일어나는 생장 반응과 관련지어 유관속조직의 발생상의 변화를 규명하기 위하여, 은단풍 유식물의 제1절간이 수평 위치에서 생장하는 동안에 일어나는 반응조직의 발생과정을 연구하였다. 수평 위치에서 생장한 은단풍 유식물의 제1절간에서 장력재(교질섬유)의 발생과정은 점진적인 과정으로 나타났다. 수평으로 위치한 제1절간의 상부에서 장력재의 발생과정은 기부에서 정단부를 향해 구정적으로 일어났다. 장력재의 해부학적 특성 중 일부는 일기유관속에서도 나타나기 시작하여, 이기생장 전형적인 장력재가 나타나게 되므로 전형성층도 유관속형성층과 마찬가지로 중력에 대하여 반응하는 것으로 볼 수 있다. 이런점으로 보아 전형성층은 유곤속형성층과 동일 분열조직으로 보아야 할 것이다. 도관요소의 길이는 상부에서 길게 나타났고, 도관의 측면무늬에 있어서는 상부와 하부에서 모두 상생으로 차이가 없었다. 방사조직의 폭은 이열방사조직을 이루는 상부가 단열방사조직을 이루는 하부에 비하여 넓고, 높이도 상부에서 다소 높게 나타났다.

• Journal of the Korean Wood Science and Technology
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• 제37권1호
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• pp.29-36
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• 2009

목재 자원의 부족과 가격 상승에 대항할 수 있는 좋은 대안 중 하나가 목재 부산물이나 폐기물의 재활용이다. 조선 산업에서 얻어지는 목재 폐기물의 경우 기존에는 파쇄 되어 보드류 생산에 주로 사용되어 왔다. 하지만 파쇄를 통한 합판 폐기물의 재활용은 재료의 경제적 가치나 자원의 문제 등을 고려할 때 아쉬움이 많이 남는 처리 방법이다. 본 연구에서는 국내 조선 산업에서 파생되는 목재 폐기물들의 재활용 가능성을 알아보고자 하였다. 국내 조선 산업의 목재 관련 폐기물은 합판 폐기물과 소재 폐기물로 나뉜다. 본 연구를 통해 다음과 같은 결론을 얻을 수 있었다. 1. KS 규격에 따라 합판 폐기물과 합판 적층재의 휨성능을 평가하였다. 2. 합판 폐기물과 합판 적층재의 파괴 모드는 두 종류 모두 simple tension 파괴를 나타내었다. 3. 합판 폐기물과 합판 적층재의 재활용 용도로는 크게 외부 시설용, 내부 시설용 그리고 목조건축 자재로의 용도가 적합하다고 판단되었다. 적정 용도로는 인테리어 재료, 목재 파렛트, 마루판, 사이딩재, 판넬, 야외용 탁자, 데크용 재료 등인 것으로 생각된다.