• Journal of the Korean Wood Science and Technology
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• 제46권2호
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• pp.149-154
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• 2018

The changes in sound absorption capability and air permeability of Malas wood after high temperature heat treatment were investigated. The average air permeability of Malas in longitudinal direction after heated under the temperature of $190^{\circ}C$ during 3 hours was about 23.48 darcys and that of control was about 3.11 darcys. The noise reduction coefficients of Malas specimens were 17% for treatment and 10% for control. The means of sound absorption coefficient of specimens in the frequency range of 50~6,400 Hz were 42% for treatment and 17% for control, respectively.

• Journal of the Korean Wood Science and Technology
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• 제44권1호
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• pp.19-29
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• 2016

본 연구는 국내에서 주로 사용되는 수입 목재 수종의 화재 안전성 평가에 대한 기초 자료를 구축하기 위하여 연소 및 열적 특성을 분석하였다. 연소 특성은 KS F ISO 5660-1 규정에 의거한 콘 칼로리미터 시험 방법으로 열방출률, 총 방출열량, 연소 가스 발생, 그리고 중량 감소를 분석하였다. 열적 안정성은 열중량 분석(Thermogravimetric analysis)을 통해 시료의 열분해 온도 및 시점을 확인하였다. 분석된 수종은 국내 유용 수입 수종으로 멀바우(Merbau), 멤페닝(Mempening), 가로가로(Garo Garo), 말라스(Malas), 그리고 딜레니아(Dillenia)로 총 5수종을 선정하여 실험을 실시하였다. 열방출률 값은 말라스 > 멤페닝 > 가로가로 > 멀바우 > 딜레니아 순으로 확인되었다. 총 방출열량을 분석한 결과, 멤페닝 > 말라스 > 가로가로 > 멀바우 > 딜레니아 순으로 측정되었다. 가스분석 결과에서는 딜레니아가 $CO/CO_2$ 비율이 최대치로 0.034로 확인되었고, 멤페닝과 말라스가 0.020으로 최소치를 나타내었다. 중량감소율의 최솟값은 딜레니아가 74.79%로 나타났으며, 말라스가 83.52%로 CO와 $CO_2$의 발생과 목재 연소의 거동과의 상관관계를 나타내었다. 수종별 열분해 온도는 멀바우 $348.07^{\circ}C$, 멤페닝 $367.57^{\circ}C$, 가로가로 $350.59^{\circ}C$, 말라스 $352.41^{\circ}C$, 딜레니아 $364.33^{\circ}C$로 확인되었다.

• Journal of the Korean Wood Science and Technology
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• 제16권3호
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• pp.5-16
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• 1988

This experiment was executed to investigate the effect of activation of veneer surface by oxidizing agents, hydrogen peroxide and nitric acid, on bonding characteristics of Malas(Homalium foetidum Benth) plywood, in which the effects of these oxidizing agents amount, pretreatment time, and pressing time and temperatue on shear strength of the plywood were examined and discussed. In this research the activation of veneer surface by oxidants was effective in raising shear strength but the difference in shear strength was not observed between hydrogen peroxide and nitric acid treatment. Hydrogen peroxide treatment, however, seemed to be more profitable to industrial application because of its lower concentration and easier handling than nitric acid. The bonding method by lignin-phenol adhesive through surface activation revealed inferior shear strength to phenol- and urea-formaldehyde adhesive but superior water resistance to urea-formaldehyde adhesive and this bonding method, in addition, have the advantage of lower cost compared with phenol-formaldehyde adhesive, Therefore, this bonding method by lignin-phenol adhesive through surface activation seemed to economical in manufacturing of water-resistant wood panel materials in future.

• 한국가구학회지
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• 제28권2호
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• pp.111-117
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• 2017

Recently, as people's interest in wood has increased, the use of wood as household and landscape decking materials has increased. As the deck material, imported wood such as synthetic wood, Ipe, and Malas was used in addition to the existing preserved wood, but recently deck use has been activated as part of the activation of domestic materials. As an important quality factor in the selection of such decking materials, various durability along with weatherability for long - term use is required for maintenance. Generally used tropical hardwoods have excellent weatherability and durability without additional preservative treatment. However, the domestic larch is a wood species with a higher specific gravity and durability than ordinary conifers. However, it has not yet been used as a deck material due to lack of comparative studies on its characteristics. Therefore, hardness and durability of wood were measured using six specimens of Ipe, Massaranduba, Malas, Douglas-fir, Larch and Torrefied-Larch. Density Profile was used to measure the density, and Brinell hardness test and resistance test against momentary impact were carried out for the test of resistance to static load. Also, The hardness and durability of wood were measured by castor test with resistance test against dynamic load, as well as, nail down test by experiment on surface hardness and durability. As a result of the experiment, the hardness was increased in proportion to the density, and it was confirmed that the imported lumber was harder and durable than the domestic larch.

• 한국조경학회지
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• 제40권3호
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• pp.81-90
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• 2012

국민 생활수준의 향상으로 안전과 환경에 대한 인식이 고조됨에 따라 조경시설물에 환경 재료의 하나인 목재가 널리 이용되고 있으나, 미송을 사용한 목재 조경시설물은 틀어짐, 균열 등의 하자가 많이 발생하고 있어, 수입목재인 활엽수재(hardwood)를 사용하는 사례가 늘고 있다. 그러나 수입 목재는 고가이며, 실제 하자 발생이 미송에 비해 얼마나 저감되는지에 대한 정보나 실태조사 없이 사용되고 있어, 시공자에게 목재 수종별 특성과 품질 하자 발생 정도에 대한 정보가 매우 필요한 실정이다. 따라서 본 연구는 목재 조경시설물에 사용되는 미송, 부켈라, 니아토, 말라스 목재 4종류를 대상으로 목재의 균열 하자현황을 조사 분석하여 시공자로 하여금 적절하게 목재를 사용할 수 있는 기초자료를 제공하는데 목적을 두었다. 본 연구의 주요 결과를 요약하면 다음과 같다. 첫째, 휴게시설물 목재기둥의 목재 표면적 당 균열 하자는 미송 1.90개소/$m^2$, 말라스 0.83개소/$m^2$, 부켈라 0.14개소/$m^2$, 니아토 0.04개소/$m^2$로 조사되어 니아토가 가장 적은 것으로 나타났다. 둘째, 목재 종류별 강도와 하자율 비교를 보면 목재의 강도는 말라스가 우수하였으나, 하자율은 니아토가 더 적게 발생한 것으로 보아 목재 강도가 높은 것이 하자가 적게 발생하는 것은 아니라는 것을 알 수 있었다. 셋째, 목재 종류별 단가와 하자율 비교를 보면 미송이 가장 저렴하고 부켈라가 가장 고가로 조사되었으며, 하자처리 비용을 감안할 때 하자가 적게 발생하는 니아토를 사용하는 것이 경제적인 측면에서 유리하다고 판단된다. 본 연구는 목재 조경시설물 설치 시 시공자로 하여금 적절한 목재를 선택할 수 있는 기초자료를 제공한다는데 그 의의가 있으며, 조경시설물의 품질 향상과 하자 저감에 기여할 수 있을 것이다.

• Journal of the Korean Wood Science and Technology
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• 제25권3호
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• pp.16-23
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• 1997

This study was carried out to discuss feasibility of high density polyethylene(HDPE) as a new substitute for the conventional adhesives in plywood manufacture. Plywood was composed of radiata pine(Pinus radiata) and Malas(Homallium feotidium) veneers and bonded by HDPE. Adhesion characteristics and anatomical scanning has been examined through tensile-shear strength test and scanning electron microscopy(SEM). The results are as follows; 1. Optimum loading quantity was 15g/$(30.3{\times}30.3)cm^2$, and tensile-shear strength increased with the increase of loading quantity. 2. Even at the hot pressing time of 1 minute, tensile-shear strength met the value of KS(over the 7.5kgf/$cm^2$), and tensile-shear strength increased with the increase of hot pressing time. 3. Plywood composed of veneer at moisture content of 19.6% showed similar tensile-shear strength to that at air conditioned moisture content of 11.4%. 4. Under the same condition of hot pressing time, tensile-shear strength of plywood bonded by HDPE met the KS value of boil and wet test and proved the same group as phenol formaldehyde adhesive. 5. HDPE films showed mechanical adhesion through penetration into the lathe check and ray of veneer.

• 대한금속재료학회지
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• 제46권7호
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• pp.449-457
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• 2008

Compression deformation behaviors at high temperature as a function of temperature and strain rate were investigated in the 6061 aluminum alloy, which is used for automobile wheel. Compression tests were carried out in the range of temperatures $300{\sim}475^{\circ}C$ and strain rate $10^{-3}{\sim}10^{-1}sec^{-1}$. By analyzing these results, strain rate sensitivity, deformation temperature sensitivity, the efficiency of power dissipation, Ziegler's instability criterion, etc were calculated, which were plastic deformation instability parameters as suggested by Ziegler, Malas, etc. Furthermore, deformation processing map was drawn by introducing dynamic materials model (DMM) and Ziegler's Continuum Criteria. This processing map was evaluated by relating the deformation instability conditions and the real microstructures. As a result, the optimum forging condition for the automobile wheel with the 6061 aluminum alloy was designed at temperature $450^{\circ}C$, strain rate $1.0{\times}10^{-1}sec^{-1}$. It was also confirmed by DEFORM finite element analysis tool with simulation process.

• 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.