• 한국가구학회지
• /
• 제16권2호
• /
• pp.59-65
• /
• 2005

As physical condition of students improves, there is a need to develop human body-friendly desk and chair for students. In this study, desks and chairs were manufactured with curved veneer lamination under high frequency heating and pressing, using ten wood species such as Japanese red pine, Korean pine, pitch pine, Japanese larch, yellow poplar, black locust, oak, radiata pine, beech, and birch. The performance of these products were evaluated. The results obtained were summarized as follows; With high frequency heating, the turned lamination of veneers with full size sheet ($3{\times}6\;feet$) prepared by rotary lathe peeling was successfully applied for making the members of desk top, leg frames of desk and chair. Bending strengths of desk tops were relatively greater for yellow poplar, black locust and red pine, which were similar to those of beech and birch. Bending strengths of desk legs were classified into greater species group (red pine, yellow poplar, larch) and lower species group (radiata pine, Korean pine, pitch pine). Compressive strengths of chair legs in parallel direction to the lamination were greater in black locust and larch. On the other hand, differences between outer and inner gap at the top and drawer bottom of desk top were rather larger for the laminations of birch and beech, and less for those of yellow poplar and pitch pine, showing greater stability of open drawer space. In results, yellow poplar, larch, pitch pine and red pine showed good appearance and strength properties at the curved veneer lamination. Accordingly, it was believed that these domestic woods were able to substitute for birch which was being imported for the use of veneer-laminates type furniture.

• Journal of the Korean Wood Science and Technology
• /
• 제25권4호
• /
• pp.99-107
• /
• 1997

This study was executed to test the possibility of replacement for domestic Japanese larch(Larix leptolepis) for hardwoods and to acquire the information about the effects of drying temperature on internal temperature, moisture content and drying defects. In high-temperature drying, internal temperature increased rapidly to boiling point, immediately after that point the internal temperature rising rate was reduced. In the case of drying at temperature of $125^{\circ}C$, internal temperature could reach at boiling point in a very short time. Moisture content in high-temperature drying showed constant drying rate period and first period of falling rate drying together in 4 hours since experiment begun. There was no strong correlation between initial moisture content and final moisture content. Average drying rate at $115^{\circ}C$, $120^{\circ}C$ and $125^{\circ}C$ was 1.42%/hr, 1.88%/hr and 2.02%/hr, respectively; the case of drying temperature of $125^{\circ}C$ showed most rapid drying rate. Drying rate of $125^{\circ}C$ was so rapid that it showed more severe shrinkage, bow, collapse, end check, and internal check development than in other drying conditions. The result of this study showed the strong possibility of high-temperature drying for Japanese larch, and to dry Japanese larch optimally, dry bulb temperature should not exceed $120^{\circ}C$.

• Journal of the Korean Wood Science and Technology
• /
• 제41권4호
• /
• pp.346-357
• /
• 2013

본 연구에서는 국내 숲가꾸기산물을 이용하여 목재펠릿을 제조하고 품질을 분석하였다. 원료는 일본잎갈나무(Larix kaempferi C.)와 활엽수 혼합 수종을 사용하였으며, 말구직경 6 cm를 기준으로 침엽수와 활엽수로 구분하였다. 분쇄 후 건조된 원료를 이용하여 목재펠릿을 제조하였다. 분쇄와 건조공정을 동일 조건에서 수행하였음에도 불구하고, 원료의 물리 화학적 차이에 따라 생산되는 목재펠릿의 품질에 차이가 발생하였다. 활엽수 혼합수종으로 제조한 목재펠릿은 회분이 1.6% 이상으로 분석되었으며, 일본잎갈나무의 경우에는 직경 6 cm 이하의 소경목에서 회분이 1.0%를 초과하였다. 목재펠릿을 제조하기 이전의 원료 상태에서와 비교하여 제조 후에 회분함량이 0.01~0.1% 정도 상승하는 것을 확인하였다. 발열량에서는 일본잎갈나무가 활엽수 혼합 원료에 비해 약 198 kcal/kg 정도 높았으며, 모든 시료에서 4,300 kcal/kg 이상으로 목재펠릿 원료로 적합한 것으로 분석되었다. 또한, 원료 상태보다 목재펠릿 제조 후 발열량이 일부 상승하는 것을 확인하였다. 원료에 포함된 주요 무기물은 수종 및 분류에 관계없이 Ca, K, Mg, Mn, Fe 등이었으며, 장기 연속 운전을 위해서는 연소기 내 클링커 형성을 억제할 수 있는 연소 방법의 개발이 요구된다. 동일한 펠릿 제조 조건에서 원료에 의해 제품 간의 품질 편차가 크게 발생할 수 있으며, 이를 극복하고 생산성 및 품질 향상을 위해서는 원료에 따른 공정 최적화가 중요한 요소임을 확인하였다.

• Journal of the Korean Wood Science and Technology
• /
• 제45권4호
• /
• pp.399-408
• /
• 2017

Research on the rapid and accurate prediction of physical properties of wood using near-infrared (NIR) spectroscopy has attracted recent attention. In this study, partial least squares analysis was performed between NIR spectra and air-dried specific gravity of five domestic conifer species including larch (Larix kaempferi), Korean pine (Pinus koraiensis), red pine (Pinus densiflora), cedar (Cryptomeria japonica), and cypress (Chamaecyparis obtusa). Fifty different lumbers per species were purchased from the five National Forestry Cooperative Federations of Korea. The air-dried specific gravity of 100 knot- and defect-free specimens of each species was determined by NIR spectroscopy in the range of 680-2500 nm. Spectral data preprocessing including standard normal variate, detrend and forward first derivative (gap size = 8, smoothing = 8) were applied to all the NIR spectra of the specimens. Partial least squares analysis including cross-validation (five groups) was performed with the air-dried specific gravity and NIR spectra. When the performance of the regression model was expressed as $R^2$ (coefficient of determination) and root mean square error of calibration (RMSEC), $R^2$ and RMSEC were 0.63 and 0.027 for larch, 0.68 and 0.033 for Korean pine, 0.62 and 0.033 for red pine, 0.76 and 0.022 for cedar, and 0.79 and 0.027 for cypress, respectively. For the calibration model, which contained all species in this study, the $R^2$ was 0.75 and the RMSEC was 0.37.

• Journal of the Korean Wood Science and Technology
• /
• 제13권3호
• /
• pp.41-48
• /
• 1985

In near future about 500,000 hectares of Japanese larch and pitch pine need thinning to improve crop-tree spacing and reasonable species composition in Korea. Although thinned trees show very little high quality wood, in fact, all the sawed products are suitable for construction and farming materials. Studies on the utilization of thinned small-diameter trees have been implemented in order to increase lumber yield and display the skeleton of farm buildings. The results obtained in this study were summarized as follows: 1. According to Korean Conifers Log Grading System, log grade 3 was 87.4 percent in Japanese larch bolts and 95.8 percent in pitch pine bolts from thinned trees. The ability to identify defects was essential for grading logs. 2. Cutting diagrams of sawing were developed for 1-sided sawing, 2-sided sawing and 3-sided sawing by small end diameter class of bolt and cutting sizes also were found to use effectively lumber with wane. 3. Lumber recovery of Pitch pine was a little higher than that of Japanese larch. The maximum lumber yields of pitch pine by sawing patterns were 87.2 percent for 1-sided sawing, 80.8 percent for 2-sided sawing an 64.1 percent for 3-sided sawing, up yield compared with 58.1 percent for 4-sided sawing. The lumber yield of 1, 2 and 3-sided sawing significantly was higher value than that of 4-sided sawing. 4. Lumber was inspected and graded. Lumber quality of diameter class 12cm was a little better than that of diameter class 8cm, but 90 percent of lumber in diameter c1ass 16cm fell into grade 3. The lumber grade was classified by Korean standard grades of confiers lumber. 5. Lumber from 1, 2 and 3-sided sawing was used to build the skeleton of a farm house ($53m^2$) and greenhouse ($60m^2$) in order to display more efficient use of small diameter trees from thinning 6. Total volume of timber for building a farm house was $8.1m^3$ of imported timber. Timber of $7m^3$, 70 percent of total volume would be substituted imported timber for domestic timber.

• Journal of the Korean Wood Science and Technology
• /
• 제35권6호
• /
• pp.13-22
• /
• 2007

주요 조림수종으로 도입 식재된 리기다소나무의 고부가가치 이용을 위한 구조용 집성재 이용 가능성을 검토하고, 이에 적합한 기술을 개발하기 위하여 본 연구를 수행하였다. 국산 리기다소나무 제재목의 기계응력등급은 대부분 E7에서 E9등급으로 집성재 제조에는 다소 불량한 것으로 나타났다. 반면 단일수종 및 혼합수종 구조용 집성재 제조에 필수적인 리기다소나무 및 낙엽소 판재의 접착성을 평가한 결과 전단접착력, 목파율, 침지 및 삶음박리율 모두 KS기준 이상으로 나타났다. 리기다소나무 단일수종 집성재의 휨성능을 측정해본 결과 휨강도는 KS의 집성재 강도등급에 따른 휨성능 합격기준을 만족한 반면 휨 탄성계수는 기준에 다소 못 미치는 결과를 나타내었다. 그러나 낙엽송 층재와의 혼합구성을 통해 리기다소나무 집성재의 휨성능(휨강도와 휨탄성계수)을 20% 향상시킬 수 있었으며, 층재 구성방법에 있어서는 판재의 탄성계수가 높고 품질이 우수한 낙엽송 층재를 외층에 배치하는 방법이 보다 효과적인 것으로 확인되었다. 결론적으로 리기다소나무의 부가가치 증진을 위한 구조용 집성재 이용은 그 가능성이 매우 컸다.

• Journal of the Korean Wood Science and Technology
• /
• 제36권6호
• /
• pp.88-95
• /
• 2008

내구성과 관련하여 구조부재의 수축문제가 목구조에서는 커다란 관심사가 되고 있다. 특히, 목재 소재를 적극 활용하는 전통공법에서는 짜맞춤 부위, 부재와 벽 등에서 발생하는 건조수축에 의한 갈라짐 등의 결함이 더욱 문제시되고 있다. 또한, 최근 기둥-보 공법에서 많이 사용되고 있는 국내산 낙엽송 집성재의 이용에 있어서도 함수율변화로 인한 수축과 팽윤에 대한 검토를 행할 필요성이 제기되고 있다. 낙엽송 소재와 접착층수를 달리한 낙엽송 집성재의 시험편에 대해 다양한 함수율상태에서의 치수변화율을 살펴보았다. 건조수축에 의한 치수변화 억제효과는 3층 이상의 접착층을 가지는 시험편에서 그 효과가 현저함을 알 수 있었다. 그리하여, 소재를 사용할 경우 최종사용조건에 맞추어 건조를 충분히 행하거나, 구조부재로 집성재를 이용함으로써 건조수축 문제를 어느 정도 해결할 수 있는 것으로 판명되었다.

• Journal of the Korean Wood Science and Technology
• /
• 제46권1호
• /
• pp.93-99
• /
• 2018

국내산 낙엽송 소경각재의 휨 강도 성능을 예측하기 위하여 비파괴적인 지표의 검토가 필요하다. 본 연구에서는 낙엽송 소경각재(단면 $89{\times}120mm$)를 초음파법, 종진동법, 소하중법의 비파괴 방법으로 탄성계수를 측정하였다. 실측 탄성계수와 유의성이 높은 비파괴 측정 방법을 결정 후 휨 파괴계수 예측 지표로 적용하였다. 종진동법으로 측정된 탄성계수가 실측 탄성계수와 가장 높은 유의성을 나타냈다. 휨 파괴계수와 실측 탄성계수의 유의성도 매우 밀접하게 측정되었으므로 종진동법에 의한 비파괴 탄성계수로 소경각재의 휨 파괴계수를 예측하였다.

• Journal of the Korean Wood Science and Technology
• /
• 제44권4호
• /
• pp.607-615
• /
• 2016

The delamination along the annual ring on the cross-section of laminae and the bonding strength according to the tangential angle between laminae were evaluated for the production of 3-ply cross-laminated timber (CLT) using domestic larch. Since there is no standard for CLT in Korea, the production and test of specimens for bonding strength followed the standard procedure of "Structural glued laminated timber" (KS F 3021). The standard specifies to exclude any measurement from the cracks of timbers resulted from drying or knots during delamination test of the glued laminated timbers. However, the failure of cross-sectional tissues along the annual rings was observed near the glue-line of all specimens during the delamination test. Because this phenomenon can generate defects in the CLT that may be exposed to various temperatures and relative humidities after the actual construction, the delamination percentage was measured by including this wood failure. As a result, the delamination percentage of the CLT which had been combined in such a way that the annual rings of outer lamina were directed inward was the lowest, which was around 13%, regardless of the annual ring direction of the middle lamina. On the other hand, the delamination percentage of the CLT which had been combined in such a way that the annual rings of outer lamina were directed outward was the highest, which was around 26%. Furthermore, end-split occurred in the outer lamina during the drying process of the boiling delamination test, which affected the delamination percentage. Therefore, the soaking delamination test was found to be more appropriate for evaluating the delamination strength of CLT. The block shear strength of larch CLT was $3.9{\pm}0.9$ MPa on average, which was 46% lower than the block shear strength requirement (7.1 MPa) of the standard, but satisfied the criteria of the block shear strength (3.5 MPa) of the European Standard (prEN 16351: 2013).

• Journal of the Korean Wood Science and Technology
• /
• 제38권2호
• /
• pp.94-100
• /
• 2010

This study was performed to develop an LRFD (Load Resistance Factored Design) Code for Domestic Larch. To accomplish his, we evaluated bending, compression, tension and shear strength. The results of the strength evaluation were utilized to verify the distribution and code conversion. For bending, tension and compressive strength, the Weibull distribution was well-fitted, but for shear strength we observed a normal distribution. For evaluating the bending and compressive strength, a full-sized specimen was used. A small clear specimen was used to test tension and shear strength. Compressive strength in particular was found to be affected by tight knots, although there was little difference between grades. In the code conversion, the design value of the LRFD was larger than the existing allowable stress value in the Korean Building Code. However, the allowable stress in this study was about two times higher than the value listed in the Korean Building Code. This result induced the difference between the soft and hard conversions. For greater reliability, the accumulation of additional data is necessary and further studies should be performed