• Journal of the Korean Wood Science and Technology
• /
• 제21권2호
• /
• pp.9-14
• /
• 1993

Weathering of wood in a region of acid rain was performed by the test which thin veneers of Sitka spruce were exposed to outdoor weathering for a total of 18 weeks, with a daily soaking for 30 minutes in acidified water in the pH range 2~5.6. The weathering measured by weight loss and loss in maximum failure load in tension was accelerated by the increase in the acidity of acidified water and in the period of outdoor exposure. It was also shown that the weathering was accelerated even with low acidic conditions in the case of long exposure period, although the weathering was rapidly accelerated with high acidic conditions. When compared the degree of weight loss with that of loss in failure load by weathering, the latter was much greater. From the results of this research, it could be concluded that at pH 4.0 or below of precipitation, the acceleration of weathering of exterior wood would become serious problems, which would be caused deterioration in performance of exterior wood.

• Journal of the Korean Wood Science and Technology
• /
• 제33권5호통권133호
• /
• pp.1-6
• /
• 2005

The anatomical structure of fusiform ray was examined by scanning electron microscopy (and microscopic images were analysed by image analyser) to explain the differences in radial fluid uptake between the extremes in the radial treatment data, i.e. between the selected trees of QCI (Queen Charlotte Islands in Rhondda, South Wales) and SO (South Oregon in Dalby, North-East England) planted in the UK. The ray structure of these two seed origins was examined microscopically and different patterns of ray composition were observed. The most important anatomical features influencing radial permeability were the nature of fusiform ray, and the condition of the resin canals, epithelial cells and intercellular spaces in particular.

• Journal of the Korean Wood Science and Technology
• /
• 제19권1호
• /
• pp.71-80
• /
• 1991

This study was carried out to investigate replaceable species with the conventional sounding board sitka spruce. by comparing the dynamic properties such as density, dynamic Young's modulus and internal friction Dynamic Young's modulus. internal friction of longitudinal and radial direction measured in free mass-free boundary condition for facile vibration analysis and measured by forced vibration method. Dynamical properties of four species were measured on squared plate specimen that the four edges were hung vertically by threads and driven magnetically through an iron piece glued on the specimen, by the use of condenser microphone as vibration transducer, and analyzed by FFT analyzer. The results obtained were as follows: 1. Chaldni method using aluminum powder was proper to identify the vibration mode in the plate vibration and it was possible to verify the resornance mode. 2. It was considered that it was necessary to investigate the influence of adhesive part on the plate vibration when the sounding board was made by two or three small board adhesion. 3. It was considered that plate vibration method, which was a superior to the vibration test of beam, was suitable for selecting suounding board because dynamic Young's modulus and internal friction show different order according to longitudinal and radial direction. 4. Paulownia tomentosa Thunb.) Steudel has been considered to be replaceable species with sitka spruce because it has high dynamic Young's modulus compared with low density, low internal friction, and K value of Paulownia tomentosa (Thunb.) Steudel is greater than that of sitka spruce.

• Journal of the Korean Wood Science and Technology
• /
• 제30권1호
• /
• pp.18-24
• /
• 2002

시트카스프루스 50×133×10 mm³ 시편을 340 mm 제논광과 주기적 강우장치를 갖춘 장치 내에서 촉진열화 시켰다. 시편은 자외선만 조사하거나 자외선을 조사하면서 동시에 강우를 병행하였으며 처리시간도 10시간과 20시간으로 구분하였다. 촉진열화 처리재의 물리적 성질을 색도, 흡습성 그리고 초음파 전달속도를 측정하여 조사하였다. 자외선 조사시간이 길수록 표면 명도가 낮아졌다. 강우처리는 표면 명도의 감소를 촉진하였으며 흡습성을 증가시켰다. 자외선과 강우 병행 처리재 중에 10시간 처리재의 흡습성이 20시간 처리재보다 높았는데 이는 20시간 처리재의 표면이 과도하게 열화된 때문일 가능성이 있다. 촉진열화 처리재의 초음파 전달속도는 무처리재보다 높았는데 이는 촉진열화에 의해 목재의 탄성계수가 높아졌거나 밀도가 감소했다고 할 수 있다.

• Journal of the Korean Wood Science and Technology
• /
• 제16권3호
• /
• pp.48-64
• /
• 1988

This study was carried out to investigate the free vibrational properties of traditional and replaceable species for sounding board, using piezoelectrical accelerometer and signal analyzer. In the study, the frequency equations of free-free beam carrying a concentrated mass in the transverse vibration and of free-mass beam in the longitudinal vibration were used. The results obtained were as follows. 1. Average values of dynamic modulus of rigidity of Korean commercial species measured were as follows. Paulownia tomatosa (Thunb.) Steudel: $5.590\times10^9\;dyne/cm^2$ Tilia amurensis Rupr.: $5.414\times10^9\;dyne/cm^2$ Macckia amurensis Rupr.: $10.044\times10^9\;dyne/cm^2$ Fraxinus mandshurica Rupr.: $8.876\times10^9\;dyne/cm^2$ Ulmus davidiana var.japonica Nakai: $8.677\times10^9\;dyne/cm^2$ Pinus rigida Miller: $6.33\times10^9\;dyne/cm^2$ Fraxinus rhynchophylla Hance: $4.666\times10^9\;dyne/cm^2$ 2. The ratio of dynamic transverse Young's modulus to dynamic modulus of rigidity, $E_T/G_{LT}$, was 24.922 for Fraxinus rhynchophylla Hance, which was the highest, 7.317 for Paulownia tomentosa (Thunb.) Steudel, which was the lowest among Korean commercial species measured. 3. The value of longitudinal dynamic Young's modulus was about 3.7% and 19.8%, respectively, higher than those of transverse dynamic and static Young's modulus. The value of transverse dynamic Young's modulus was about 15.5% higher than that of static Young's modulus. 4. Predicted value of MOR in terms of correlation coefficient by transverse dynamic Young's modulus was slightly higher than that of static Young's modulus, but no significance was found out. 5. Transverse dynamic Youne's modulus was $(2.002\pm0.288)\times10^{11}\;dyne/cm^2$ for Fraxinus mandshurlca Rupr., which was the highest, $(0.601\pm0.100)\times10^{11}\;dyne/cm^2$ for Paulownia tomentosa (Thunb.) Steudel, which was the lowest among Korean commercial species measured. The sound velocity of sitka spruce was 5,685 m/sec, which was the highest. 6. Internal friction of Paulownia tomentosa (Thunb.) Steudel was shown the lowest value among Korean commercial species, $(8.795\pm1.795)\times10^{-3}$, but was higher than that of sitka spruce, $(7.331\pm0.991)\times10^{-3}$. Internal friction was shown negative correlation with density and dynamic Young's modulus, respectively. 7. K value was affected largely by internal friction and was the highest, $2.225\times10^8$ for Paulownia tomentosa (Thunb.) Steudel and was the lowest, $0.550\times10^8$ for Fraxinus rhynchophylla Hance. K value of Paulownia tomentosa (Thunb.) Steudel was higher than that of sitka spruce and K values of melapi and cottonwood, which have been considered to be replaceable species with sitka spruce in the piano industry, were lower than those of Paulownia tomentosa (Thunb.) Steudel and mill amurensis Rupr.

• 한국재난정보학회 논문집
• /
• 제10권1호
• /
• pp.1-14
• /
• 2014

본 연구에서는 탄성이론에 근거하여 3차원 spline 대판법을 이용하여 직교이방성판의 3차원 응력해석을 제시한다. 직교이방성판은 아라고나이트 결정과 시트카 스프러스로 구성되어 있다. 해석에 대한 수렴섬과 정밀도의 정확성을 수치해석 예를 들어 검증하고, 탄성이론에 근거하여 이산화된 수치해석법에 의해 결과을 비교 검토한다. 해석법에 따라 해의 수렴성과 정밀도를 구할 수 있으며, 두께폭 비, 종횡비와 아라고나이트 결정과 시트카 스프러스판의 수직응력분포에 대한 경계조건의 영향을 검토하고, 응력 분포의 특성에 미치는 직교이방성과 강한 이방성의 특징의 차를 비교 검토한다.

• Journal of the Korean Wood Science and Technology
• /
• 제35권5호
• /
• pp.7-15
• /
• 2007

To evaluate the durability of finger-jointed woods according to change of humidity conditions, four types of finger-jointed woods glued with different kinds of adhesives and finger pitches were made with Sitka spruce, and the effect of humidity conditions on creep performances was investigated. The shape of creep curves differed among humidity conditions, and the inclination of creep curves was greatest in 85%RH, and lowest in 65%RH. Their creep curves showed a linear behavior beyond approximately one hour, regardless of humidity conditions. The A values of the creep curves fitted to power law increased with increasing relative humidity, whereas the A' values were in order of 30 > 85 > 65%RH unlike the A values. The initial deformation increased with increasing relative humidity, whereas the creep deformation unlike the initial deformation was in order of 85 > 30 > 65%RH, and it was found that the creep deformation of finger-jointed woods indicated the smaller amount in air-dry moisture content rather than in a low moisture content less than 30%RH. Finger-jointed woods with 6.8 mm (L) pitch had the greater creep amount than in those with 4.4 mm (S) pitch in all humidity conditions. The difference of creep amount between both adhesives in all humidity conditions was small. Relative creep at 240 hr was greatest as 62.2~71.9% in 85%RH, and the values indicated 2.1~2.6 times that of 30%RH and 3.0~3.6 times that of 65%RH and were equal or slightly greater than that of solid spruce.

• Journal of the Korean Wood Science and Technology
• /
• 제17권2호
• /
• pp.26-33
• /
• 1989

The acoustic absorption coefficient and acoustic impedance of 5 species of softwood(sonamoo, sam namoo, gusang namoo, hwaback, sitka spruce) and 5 species of hardwood (Mulgusul namoo, Italian popular, white meranti, red meranti, kalantas) were measured by the standing wave method. which is simple in the setup and gives more accurate result than does any other measuring method. The dependence of the absorption coefficient and complex acoustic impedance on the wood sections. thickness of the sample itself and the back air gap was investigated experimentally in the frequency range from 200Hz to 1800Hz, and the result are as follows: 1. The acoustic absorption coefficient of wood sections was higher on the cross section than radial and tangential sections. 2) The acoustic absorption coefficient were higher in the frequency range from 400Hz to 600Hz, but decreased in the frequency above 600Hz. 3. The genenal tendency of the variation of the normal acoustic impedance was increased according to the frequency. 4. The acoustic absortion coefficient was increased in the to 7mm-thick sample and decreased in 9mm-thick sample. 5. The higher acoustic absorption coefficient was shown in the case with the backing an gap than in the case without the gap.

• Journal of the Korean Wood Science and Technology
• /
• 제26권3호
• /
• pp.16-25
• /
• 1998

This study was carried out to compare vibrational properties and adsorption among shellac, cashew finished plate and untreated plate of Sitka spruce(Picea sitchensis Carr). By the method of statistical regression modeling, the fundamental resonance frequency of finished plate was higher than that of untreated plate. The fundamental resonance frequency of cashew finished plate was higher than that of shellac finished plate. By the method of modal analysis, mode frequency ratio of cashew finished plate was higher than that of shellac finished plate. Amounts of adsorption of finished plate was lower than that of untreated plate, and amount of adsorption of cashew finished plate was lower than that of shellac finished plate. It was clarified that the vibrational properties and adsorption of finished plate were superior to those of untreated plate. The vibrational properties and adsorption of cashew finished plate was superior to those of shellac finished plate.

• Journal of the Korean Wood Science and Technology
• /
• 제33권5호통권133호
• /
• pp.57-65
• /
• 2005

Following our previous reports for finger-jointed woods with various finger profiles studied for the efficient use of small diameter logs and woods containing various defects, twelve types of finger-jointed woods glued with three kinds of adhesives and with two sizes of finger pitches were made with sitka spruce and red pine. The effects of the adhesives and finger pitches on bending creep performances of finger-jointed woods were investigated. The shape of creep curves differed among the used adhesives and finger pitches of finger-jointed woods for both tested species. Their creep curves showed a linear behavior beyond about one hour, and the N values fitted to power law increased with increasing finger pitches. The initial deformation increased with increasing finger pitches, regardless of the tested species and kinds of adhesives, whereas the effect of finger pitches on the creep deformation was not clear. For finger-jointed woods glued with polyvinyl acetate (PVAc) resin, creep failure occurred in 106 hours after the load was applied. And the difference of the creep compliance between finger-jointed woods glued with resorcinol-phenol formaldehyde (RPF) resin and aqueous vinyl urethane (AVU) resin was small. The ratios for creep performances of finger-jointed woods glued with RPF resin and AVU resin versus solid wood were higher in creep deformation than initial deformation for both species, and the difference between both adhesives was not found. The relative creep decreased with increasing finger pitches, and the marked differences was not found between RPF resin and AVU resin.