• Journal of the Korean Wood Science and Technology
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• 제50권4호
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• pp.237-245
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• 2022

This study examined the structural performance of experimental parallel strand lumber (PSL) from a Larch veneer strand. The prototype of PSL from a Larch veneer strand was manufactured in the experimental laboratory and tested. The bending and dowel bearing strength were determined from the modulus of elasticity (MOE), modulus of rupture (MOR), and dowel bearing strength based on a 5% offset yield load. The test results indicated that the average MOR of PSL was higher than that of 2 × 4 dimension lumber, and the average MOE of PSL was lower than that of 2 × 4 dimension lumber. A linear relationship was observed between the MOR and MOE. The allowable bending stress of PSL was derived as specified in ASTM D2915 and compared with other research. The dowel bearing strength of PSL in parallel to the grain was approximately double that perpendicular to the grain of PSL. A comparison of several theoretical calculations based on each national code for the dowel bearing strength was conducted, and some theoretical equations produced results closer to the experimental results when it was parallel to the grain, but the difference was higher in the case perpendicular to the grain. The test results showed that PSL made with Japanese larch veneer strands appeared to be suitable for a raw material of structural composite lumber (SCL) appeared to be used as a raw material for SCL.

• Journal of the Korean Wood Science and Technology
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• 제33권5호통권133호
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• pp.7-12
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• 2005

The objective of this study is to estimate the mechanical behavior in bending and the anatomical changes of wood under several deflection rates. Sample specimens of water-saturated Japanese cedar (Cryptomeria japonica) were stressed to rupture under several deflection rates. Mechanical properties of wood such as modulus of elasticity, modulus of rupture and stress at proportional limit, and anatomical changes affected by deflection rates were estimated. Microscopic observations on compression side of the test specimens when the specimen was loaded to rupture were carried out by the SEM (scanning electron microscopy). The results are summarized as follows: 1. The mechanical properties of wood were affected by variations of the deflection rates. The modulus of elasticity (MOE), modulus of rupture (MOR) and stress at proportional limit were in proportion to the logarithm of deflection rates. 2. The deflection of wood at rupture in bending increased as deflection rates decreased. 3. The variations of the microscopic deformations of sample specimens were closely related to the deflection of wood at rupture. In case of largely deflected wood by maximum bending load, severe and abundant microscopic deformations were observed.

• Journal of the Korean Wood Science and Technology
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• 제42권2호
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• pp.130-137
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• 2014

Nondestructive evaluation (NDE) method by using a resonance frequency mode was carried out for ceramics made from particle boards with different phenol resin impregnation ratios (30, 40, 50, 60%) at carbonizing temperature of $800^{\circ}C$. The material for ceramics was Miscanthus sinensis var. purpurascens board. Dynamic modulus of elasticity increased with increasing impregnation ratio. There was a close relationship of dynamic modulus of elasticity and static bending modulus of elasticity to modulus of rupture (MOR). However, the result indicated that correlation coefficient is higher in dynamic modulus of elasticity to MOR than that in static modulus of elasticity to MOR. Therefore, the dynamic modulus of elasticity using resonance frequency by free vibration mode is more useful as a nondestructive evaluation method for predicting the MOR of ceramics made from Miscanthus sinensis var. purpurascens particle boards by different phenol resin impregnation ratios.

• Journal of the Korean Wood Science and Technology
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• 제25권1호
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• pp.8-14
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• 1997

Stress wave velocity, wave impedance, and stress wave elasticity of small, clear bending specimens of five domestic softwoods (Pinus densiflora, Pinus koraiensis, Chamaecyparis obtusa, Cryptomeria japonica, and Larix leptolepis) and four tropical hardwoods(Kempas, Malas, Taun, and Terminalia) were correlated with static bending modulus of elasticity(MOE) and modulus of rupture(MOR). The degree of correlation between stress wave parameters and static bending properties was dependent on wood species tested. Stress wave elasticity and wave impedance were better predictors for static bending properties than stress wave velocity for each species individually and for softwood or hardwood species taken as a group, even though elasticity and impedance were nearly equally correlated with static bending properties apparently. Based upon the correlation coefficient between stress wave parameters and static properties, stress wave elasticity and wave impedance were found as stress wave parameters which can be used for the purpose of the reliable and successful prediction of bending properties. The degree of correlation between static MOE and MOR was also different according to wood species tested. Static MOE was nearly as well correlated with MOR as was stress wave elasticity. The results of this research are encouraging and can be considered as a basis for further work using full-size lumber. From the results of this study, it was concluded that stress wave measurements could provide useful predictions of static bending properties and was a feasible method for machine stress grading of domestic softwoods and tropical hardwoods tested in this study.

• Journal of the Korean Wood Science and Technology
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• 제42권6호
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• pp.723-731
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• 2014

공진주파수 모드를 이용하는 비파괴 평가기술법을 거대억새 파티클 보드를 페놀수지로 함침한 후 탄화온도별(600, 800, 1000, $1200^{\circ}C$)로 제조한 세라믹에 적용하였다. 동적 탄성계수와 정적 휨 탄성계수는 탄화온도가 증가할수록 증가하였다. 휨 강도에 대한 동적 탄성계수 및 정적 휨 탄성계수는 밀접한 상관관계를 나타내었다. 그러나 휨 강도에 대한 상관관계에서 정적 탄성계수 보다 동적 탄성계수가 더 밀접한 상관관계를 나타내었다. 따라서 공진 주파수 모드를 사용하는 동적 탄성계수측정법으로 소성온도에 따라 제조된 거대억대 파티클보드의 휨 강도를 예측하는 비파괴 평가 방법으로 유용할 것으로 판단된다.

• Journal of the Korean Wood Science and Technology
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• 제23권2호
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• pp.70-76
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• 1995

본 연구는 왁스첨가순서(添加順序), 첨가량(添加量), 왁스종류(種類)가 Isocyanate 접착(接着) PB의 성질(性質)과 내수성(耐水性)에 미치는 영향(影響)을 구명(究明)하기 위해서 실시(實施)되었다. 왁스첨가순서(添加順序)는 PB의 기계적(機械的) 성질(性質) 및 내수성(耐水性)에 유의적(有意的)인 영향(影響)을 미치지는 않았다. 왁스에멀젼 첨가량(添加量)을 증가(增加)시킴으로써 접착력(接着力) 및 휨강도(强度) 내수(耐水) MOR은 감소(減少)되었지만 상태(常態) MOR 및 MOE는 감소(減少)되지 않았다. 상태접착력(常態接着力), 상태(常態) 및 내수(耐水) MOR과 MOE는 솔리드왁스량(量)을 증가(增加)시킴으로써 감소(減少)되지 않았지만 내수접착력(耐水接着力)은 감소(減少)되었다. 1% 및 1.5% 왁스량(量)을 첨가(添加)한 보드는 0.5% 왁스를 첨가(添加)한 보드와 비교(比較)해 보았을 때 내수성(耐水性)이 증가(增加)되지는 않았다. 솔리드왁스를 첨가(添加)한 보드의 접착력(接着力)은 왁스에멀젼을 첨가(添加)한 보드보다 더 좋은 결과(結果)를 나타내었다. 휨강도(强度)의 MOR 및 MOE, 내수성(耐水性)은 솔리드왁스와 왁스에멀젼간에 유의적(有意的)인 차이(差異)를 보이지는 않았다.

• Journal of the Korean Wood Science and Technology
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• 제24권3호
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• pp.12-17
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• 1996

This study was carried out to investigate some mechanical properties for wood rational utilization of heartwood and sapwood in radiata pine according to basic density, ring width and proportion of latewood which were grown in New Zealand. This result were summarized as follow: Heartwood showed 35.78(MPa) of the compression strength parallel to the grain while sapwood showed 42.08(MPa). The modulus of rupture in static bending was higher in sapwood showing 86.12(MPa) than in heartwood 72.99(MPa) Heartwood had 7.38(GPa) for the modulus of elasticity in static bending and sapwood 8.17(GPa). As the basic density and proportion of latewood increased: compression strength parallel to the grain, MOR and MOE in static bending had a tendency to increase. As ring width increased, the mechanical properties decreased.

• Journal of the Korean Wood Science and Technology
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• 제41권5호
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• pp.392-398
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• 2013

This study investigated the effect of test zone selection for evaluating bending strength of visually graded lumber. This will contribute to the understanding of two different methods under different standards. In method I, the major defect was randomly placed in the test specimen. In method II, the major defect was randomly placed in the maximum moment zone (MMZ). The results showed that the method II is more accurate for reflecting the effect of defects governing the grade of lumber. Unless the maximum strength-reducing defect (MSRD) is placed in MMZ, the evaluated value would be higher than that of MSRD. For evaluating the modulus of rupture (MOR) of visually graded lumber in test set-up of Method I, the Eq. (5) needs to be considered.

• Journal of the Korean Wood Science and Technology
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• 제46권5호
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• pp.486-496
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• 2018

4점 휨 시험에서 지간 길이에 따른 낙엽송 제재목의 휨 성능 변화를 알아보기 위하여 연구를 진행하였다. 연구에 사용된 시험편의 크기는 38(너비) ${\times}$ 89(깊이) ${\times}$ 3,600(길이) $mm^3$이며, 평균 기건 밀도와 함수율은 각각 $543.5kg/m^3$, 10.5%이었다. 낙엽송 육안 등급 1등급 248본을 두 그룹으로 나눠, 지간 거리 1,650 mm와 3,000 mm에서 휨 실험을 진행하여 휨 강도와 휨 탄성계수를 도출하였다. 휨 탄성계수는 유의 수준 5%에서 지간 거리에 따라 차이가 없다고 판단된 반면 휨 강도는 차이가 있었으며, 지간에 반비례하였다. 지간 거리 1,650와 3,000 mm에서 휨 강도의 5% 하한치는 각각 28.65와 25.70 MPa로 확인되었다. 지간 거리에 따른 휨 강도 차이는 백분위 수가 증가함에 따라 커지는 것으로 확인되었으며, 이는 와이블 최약 링크 파손 이론에 의한 치수 효과 때문으로 사료된다. 따라서 지간 대 깊이 비가 15 이상으로만 제한되어 있는 목구조용 실대재 휨 시험법(KS F 2150)에 치수 효과를 고려할 수 있는 방법이 포함되어야 할 것으로 판단된다. 이를 통해 다양한 치수의 제재목에서 얻어지는 강도를 설계 값에 반영할 수 있을 것으로 기대된다.

• 한국가구학회지
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• 제12권2호
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• pp.1-10
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• 2001

As finger joint method has a high rate of yield and high strength and ease in working, it has been widely used as an end joint method for solid wood and wood based-material. Therefore, we end-joined the material of Pinus densiflora, Quercus variabilis and populus euramericana with polyvinyl acetate adhesive and resorcinol phenol resin adhesive. The effect of difference (0, 0.15, 0.3, 0.45mm) between the dimensions of tip width and root width of the finger (DTRW) on bending strength properties was as follows: 1. In the case of polyvinyl acetate adhesive, DTRW had no effect on bending modulus of elasticity(MOE) and modulus of rupture(MOR) of the three kinds of species, because their bonding layers were destroyed by slippage, not their woody parts. 2. In the case of resorcinol phenol resin adhesive, the material of Quercus variabilis showed an optimal result at 0.15 or 0.3 of DTRW, while the poplar did at 0 of DTRW 3. The differences in efficiency ratio of bending MOR of populus euramericana, Pinus densiflora and Quercus variabilis species according to the kind of adhesive were 13-29%, 23-30% and 45-53%, respectively.