| 1. |
Andi Hermawan, Noboru Fujimoto, Viscoelastic creep behavior of surface- and inner-layers of sugi boxed-heart timber under various temperatures, Journal of Wood Science, 10.1186/s10086-019-1836-y, 65, 1, 2019.12, This study was conducted to investigate the rheological behavior of sugi boxed-heart timber under constant moisture content (MC) using a cantilever creep test. The focus of the study was the effect of temperature on viscoelastic creep behavior of surface- and inner-layer specimens of the timber. The specimens with dimensions of 75 mm in length, 25 mm wide, and 3 mm thick were prepared. A cantilever creep test with an effective span of 40 mm was conducted under a constant temperature of 20, 65, 80, and 95 °C. The equilibrium moisture content (EMC) of the specimens was set to around 12% at each temperature. A load representing 20% of rupture load of the specimens at each temperature was applied to their free-end and strain gauges were bonded at the fourth span (10 mm) on the upper and bottom surfaces of the specimens. Loading and unloading duration were set for 300 and 180 min, respectively, and a four-element Burgers model was used to model the creep behavior of the timber. It was found that temperature had significant effects on the creep properties of the timber. The surface strain and creep compliance of the surface- and inner-layer specimens tended to increase as the temperature increased. Creep compliance of the surface-layer specimen was higher than that of the inner-layer specimen at each temperature. Fitting the experimental data with the Burgers model used in this study shows good agreement and it was found that elastic (instantaneous) and viscoelastic (delayed) creep compliance of all the specimens tended to increase as the temperature increased. On the other hand, the viscosity of the dashpot element of both the Maxwell and the Kelvin unit tended to decrease as the temperature increased. Although different in magnitude, the creep-recovery compliance parameters had the same tendency as the creep compliance parameters.. |
| 2. |
Hiroki Sakagami, Atsuro Tokunaga, Noboru Fujimoto, Shinya Koga, Isao Kobayashi, Ikuo Momohara, Effects of drying temperature for Cryptomeria japonica on the permeability of wood preservative. I
The permeability of dried logs, BioResources, 10.15376/biores.11.2.4781-4793, 11, 2, 4781-4793, 2016.05, Wood preservative treatments are indispensable for wood used in severe environmental conditions. Decay occurs in preservative-treated woods due to the poor impregnation of sapwood; this problem has recently gained attention for Cryptomeria japonica kiln-dried logs. To clarify the causes of this phenomenon, the influence of drying temperature on the penetration of preservative into sapwood logs was investigated. Sapwood samples taken from logs dried at 20 °C to 120 °C were impregnated with copper azole (CuAz). The bordered pits of these samples were observed by scanning electron microscopy (SEM). These results revealed that CuAz absorption decreased with increased drying temperature. The CuAz penetration was deepest for the samples dried at 20 °C. The occurrence of neutral-position bordered pits tended to decrease with increasing drying temperature. These results indicated that there is a strong relationship between the drying temperature and the appearance of bordered pits. Furthermore, the preservative permeability decreased with increasing drying temperature. This result implies that one factor restraining fluid permeability is the aspiration of bordered pits.. |
| 3. |
Andi Hermawan, Toru Nakahara, Hiroki Sakagami, Noboru Fujimoto, Kiyotaka Uchikura, Performance of Sugi lamina impregnated with low-molecular weight phenolic resin, Journal of Wood Science, 10.1007/s10086-013-1338-2, 59, 4, 299-306, 2013.08, This study was conducted to evaluate the performance of Sugi lamina impregnated with low-molecular weight phenolic (LMWP) resin using the full cell process followed by curing at high temperature. In this study, penetration of LMWP resin into finger-jointed lamina was examined. Physical and mechanical properties, such as surface hardness, dimensional stability, bending and shear strength of LMWP-resin-treated and untreated lamina were investigated. In addition, the bonding quality and nail-withdrawal resistance of 3-ply assembly specimen made from LMWP-resin-treated and untreated lamina bonded using resorcinol-phenol formaldehyde resin adhesive were also investigated. The main results were as follows: LMWP resin was found to have penetrated sufficiently into finger-jointed lamina. The physical properties of LMWP-resin-treated lamina were found to have improved significantly in comparison with untreated lamina. However, no significant difference was found between LMWP-resin-treated and untreated lamina in terms of their mechanical properties. There was an improvement in bonding quality of the assembly made from LMWP-resin-treated lamina when compared with that made from untreated lamina. In the assembly made from untreated lamina, a significant decrease in nail-withdrawal resistance was observed between dry conditions test and after humidity conditioning test. However, the same tendency was not found in the assembly made from LMWP-resin-treated lamina.. |
| 4. |
Andi Hermawan, Noboru Fujimoto, Hiroki Sakagami, A Study of Vacuum-Drying Characteristics of Sugi Boxed-Heart Timber, Drying Technology, 10.1080/07373937.2012.749274, 31, 5, 587-594, 2013.04, In this study, we evaluated the effects of drying under atmospheric and vacuum pressure on the drying time, checking, and color change of sugi boxed-heart timber dried at the same dry-bulb temperature and the same wet-bulb depression. The results obtained were as follows: Sugi boxed-heart timber specimens dried at any temperature under vacuum pressure had a shorter drying time than the specimens dried under atmospheric pressure. At moisture content above fiber saturation point and at the same dry-bulb temperature, the specimens dried under vacuum pressure had a drying rate that was almost twice as fast as that of the specimens dried under atmospheric pressure. Sugi boxed-heart timber specimens dried under both atmospheric and vacuum pressure at a higher drying temperature had a shorter drying time than the specimens dried at a lower drying temperature. Apart from the sugi boxed-heart timber specimen dried at a temperature of 100°C under atmospheric pressure, no surface checks were observed for the specimens dried under vacuum pressure or at the other temperatures dried under atmospheric pressure. Slight internal checks were observed in sugi boxed-heart timber specimens dried at a temperature of 100°C under both atmospheric and vacuum pressure. After planer shaving, there was no significant difference between kiln drying under atmospheric pressure and that done under vacuum pressure in terms of the color change (ΔE*) for both sapwood and heartwood of sugi boxed-heart timber specimens.. |
| 5. |
Takeshi Ohuchi, Andi Hermawan, Noboru Fujimoto, An Experimental study on adhesive condition with sugi block specimen which assumed Finger-joint by block shear test, Journal of the Faculty of Agriculture, Kyushu University, 58, 1, 99-102, 2013.02, In end-jointing of laminae for the glulam timber, finger-joint is generally used. However, the strength properties of the glulam timber greatly decrease by slippage-off and destruction in starved joints of fingerjointed part when the laminae with starved joints in the finger-joint are located on the external layer of the glulam timber. Therefore, for the glulam timber with good strength properties, the evaluation of finger-joint properties after finger-jointing is important, and the method is hoped to be simple and non-destructive. In this study, to examine the optimum adhesive condition in finger-joint part which influences strength properties of the large-scale sugi finger-jointed laminae, the block shear tests with sugi block specimens which assumed finger-joint part and glued under various adhesive conditions was performed. The main results are summarized as follows: In the case of the specimen of W-O (With curing agent, One side spreading) under 40-20 (open assembly temperature and time set to 40'C and 20 min) with resorcinol phenol resin type adhesive, the tendency to decrease of the shear strength was shown. From the fracture morphology, the reason was considered that the adhesive did not transfer on none-spreading side because the surface of the adhesive has stiffened by setting the open assembly temperature and time. In other conditions, an enough glued performance was considered because the shear strength showed a comparatively large value. Moreover, in the case of None-specimen (Without curing agent), the shear strength shows a small value and the tendency to decrease was shown by setting the open assembly temperature and time. In three conditions of W-O, None-B (Without curing agent, Both sides spreading), and None-0 (Without curing agent, One side spreading) under 40-20 with aqueous polymer solution-isocyanate adhesive, the shear strength had decreased remarkably. In other conditions, the difference was not admitted and the tendency to decrease of the shear strength was shown by setting the open assembly temperature and time.. |
| 6. |
Ming Hsun Chan, Shih Te Hu, Han Chien Lin, Noboru Fujimoto, Comparison of COFECHA and TSAPWIN from dendroclimatology for climate change and taiwan fir (abies kawakamii) growth pattern in alpine central Taiwan, Journal of the Faculty of Agriculture, Kyushu University, 58, 1, 115-123, 2013.02, Many tree ring researches have worldwide revealed that climate change influence tree growth pattern in alpine tree-line, but it is still lack of these research in Taiwan. From central Taiwan Mt. Hehuan alpine tree-line Taiwan fir (Abies kawakamii H.) dendroclimatic analysis, we found the relationships of ring width and BAI growth with climate change in 1953-2010. Tree ring width and BAI growth were highly significant correlated to standard chronology, residual chronology and autoregressive chronology, it responded most similar climate signal at the same periods, and tree ring width standard chronology reflected most climate signals. Tree ring width and BAI growth responded temperature decreasing correlation in February, March, April of early spring, it reflected that the later summer temperature increasing correlation in August, September and October, at the same time monthly temperature and season temperature reflect synchrony of most part. Tree ring width and BAI growth reflected monthly accumulated precipitation increasing correlation in January and March, and reflected August and November monthly accumulated precipitation decreasing correlation. It is understand that early spring low temperature with increasing precipitation and later summer high temperature with decreasing precipitation promoted Taiwan fir to grow. The average temperature of recent 60 year later summer (August, September, and October) has increasing trend l'C. The increasing trend of BAI growth was as same as mean temperature in later summer, it had a high linear correlation. Later summer temperature increasing and warming promoted to grow, the research found that the increasing temperature in early spring would suppress the growth. And, the relationship establishment of tree ring width and BAI growth, climate change would help to understand how climate warming influence tree growth pattern in alpine forest tree-line.. |
| 7. |
Andi Hermawan, Noboru Fujimoto, Hiroki Sakagami, Effects of High-Temperature and Low-Humidity Pretreatment on the Drying Properties of Sugi Boxed-Heart Timber with Black-Colored Heartwood, Drying Technology, 10.1080/07373937.2012.663433, 30, 7, 780-786, 2012.06, In this study, the optimal conditions of high-temperature and low-humidity (HT-LH) pretreatment to prevent surface checks of sugi boxed-heart timber with black-colored heartwood were investigated. The focus of this study was on the effects of log diameter, temperature, and pretreatment time on the drying time and checking of the timber dried at a constant temperature and relative humidity. The results obtained were as follows: The drying time of specimens obtained from 22-cm-diameter logs was longer than that obtained from 20-cm-diameter logs. The drying time of specimens obtained from 22-cm-diameter logs was influenced by both pretreatment temperature and time. Higher pretreatment temperature and/or longer pretreatment time resulted in longer drying times. In contrast, in the case of specimens obtained from 20-cm-diameter logs, a longer pretreatment time resulted in a shorter drying time. The average surface check area of specimens tended to decrease and the average total number and length of internal check tended to increase as pretreatment temperature and time increased. Pretreatment at a temperature of 135°C for 10 h or 150°C for 7 h was effective in preventing surface checks of the specimens.. |
| 8. |
Akari Uno, Takeshi Ohuchi, Noboru Fujimoto, Studies on manufacturing of wooden flat pallet by staggered connection using sugi compressed-dowel and its process, Journal of the Faculty of Agriculture, Kyushu University, 57, 1, 175-179, 2012.02, In this study, we manufactured three types of the wooden flat pallet with different in the number of sheets of the top board of the backside. First type (7-7 type); the number of sheets of the top board of the backside was seven pieces. Second type (7-5 type); the number of that was five pieces. Third type (7-3 type); the number of that was three pieces. The number of the surface of three types was all seven pieces. In the manufacturing, the staggered connections using sugi (Cryptomeria japónica D. Don) compresseddowel were applied to the pallet, and the evaluation test in accordance with Japanese Industrial Standard (JIS Z 0602) was performed. The main results are summarized as follows: The pallet weight became small in decreasing the number of sheets of the top board and the difference of the weight was about 6 kgf (20%). The bend rate in the bending test for each type pallet was smaller than 2.5% of the standard value of JIS. The residual bend rate in the bending test for each type pallet was also smaller than 0.5% of the standard value of JIS. Therefore, it was confirmed that the condition as the pallet of both the bend rate and the residual bend rate was cleared. In each type pallet, the condition as the pallet in the change rate of the diagonal length in the fall down test was cleared because the change rate of the each value was smaller than 3% of the standard value of JIS. The remarkable difference of the withdrawal strength of each type pallet in the pull-out test for the staggered connections using sugi compressed dowel was not recognized. Moreover, it became clear that approximately 56 minutes in manufacturing process of one pallet can be shortened and the manufacturing cost can be decreased because four top boards of the backside of the pallet were decreased.. |
| 9. |
Andi Hermawan, Takeshi Ohuchi, Noboru Fujimoto, Manufacture of three-layer wood-porcelain stone composite board reinforced with bamboo fiber, Materials and Design, 10.1016/j.matdes.2010.11.008, 32, 4, 2485-2489, 2011.04, The objective of this study was to improve bending strength properties of three-layer wood-porcelain stone composite board. The focus of this study was on the effects of orientations and weight ratios of bamboo fiber in face layer on physical and mechanical properties of the board. Three types of board with different orientation of bamboo fibers in the face layer were manufactured: one in which the fibers were oriented at random orientation (R board), another in which the fibers were oriented at unidirectional orientation (U board), and a third in which the fibers were oriented at cross orientation (C board). The physical and mechanical properties of the boards were evaluated based on the Japanese Industrial Standard for Particleboards. The main results obtained were as follows: Bending strength properties of the board were strongly affected by both orientation and weight ratio of bamboo fibers. Perpendicular specimen of C board has larger bending strength properties than U board and the value become larger with increased weight ratio of bamboo fibers. Internal bond strength value decreased with increasing weight ratio of bamboo fibers. The effect of orientation and weight ratios of bamboo fiber on thickness swelling of the board was not significant.. |
| 10. |
Akihiro Matsumoto, Hisato Oda, Takanori Arima, Noboru Fujimoto, Effect of using a hot-press to suppress surface checks in sugi boxed heart square timbers during the drying process, 11th World Conference on Timber Engineering 2010, WCTE 2010
11th World Conference on Timber Engineering 2010, WCTE 2010, 293-299, 2010.12, The high temperature drying method has become popular for drying sugi (Cryptomeria japonica D.Don) boxed heart square timbers in Japan because it shortens the drying time and suppresses surface checks. However, it is well known that internal cracks and surface discoloration often occur in sugi boxed heart square timbers during the drying process. We investigated the effect of using a hot-press for suppressing surface checks in sugi boxed heart square timbers during the drying process. That is to say, the objective of this study was to reduce the damage of timbers during the drying process by shortening the high temperature drying time. The treatment for suppressing surface checks in timber is to form a surface drying set in it. This report presents the effect of using a hot-press for the formation of a surface drying set in sugi boxed heart square timbers. The results of this study are summarized below. The inside of the sugi boxed heart square timbers showed almost no drying with this surface treatment. Surface drying of the sugi boxed heart square timbers could be carried out uniformly with 30 min of hot-pressing with hardly any influence from the wide variations in moisture content. However, there was no good progress in drying over the 2nd layer under any of the test conditions. Higher plate heating temperatures resulted in deeper heating in the sugi boxed heart square timbers. In this surface treatment, the drying set was formed in the 1st layer under each test condition. However, in the 2nd and 3rd layers, the drying set was hardly formed. In this study, two types of plates were used: a flat plate with a smooth surface and a slit plate with grooves cut into the surface to make it easier for it to release vapor. However in these results, the effect of creating slits was not apparent.. |
| 11. |
Andi Hermawan, Takeshi Ohuchi, Noboru Fujimoto, Manufacture of strand board bonded with disposal expanded polystyrene as binder, Journal of the Faculty of Agriculture, Kyushu University, 55, 1, 107-110, 2010.02, The objective of this study was to evaluate the physical and mechanical properties of strand board bonded with disposal expanded polystyrene (EPS) as binder. The strand board was manufactured using strand made from Douglas-fir beams selected from construction scrap wood. The strands were oriented, and two types of three-layer (face-core-face) strand board were manufactured: one in which the board bonded with only disposal EPS (P board), and the other in which the board bonded with disposal EPS after isocyanate compound adhesive was applied to the strand (M board). The physical and mechanical properties of the boards were evaluated based on the Japanese Industrial Standard for Particleboards (JIS A 5908). The main results obtained were as follows: bending strength properties and internal bond (IB) strength of P board had larger than those of type 18 PB and 24-10 PB standard. However, thickness swelling (TS) of the board was large, and the problem in water-proof property of the board remained. Bending strength properties, IB strength and TS of M board were larger than those of type 24-10 PB standard. The performance of M board showed equal or larger performance than those of control board.. |
| 12. |
Andi Hermawan, Hirokazu Hashiguchp, Takeshi Ohuchi, Noboru Fujimoto, Effect of raw material of core layer on property of wood-porcelain stone composite board, Journal of the Faculty of Agriculture, Kyushu University, 54, 2, 463-466, 2009.10, In a search for an effective use of both scrap wood and porcelain stone scrap, we manufactured threelayer wood-porcelain stone composite board made from both materials. The objective of this study was to improve bending strength properties of the board. Pruned branch with leaf CBL), pruned branch without leaf (B), and root-stump (RS) were prepared as raw material of core layer of the board. In board manufacturing, three types of wood particles were prepared as follows: wood particles processed by using an industrial grinder (IG), by using crushing machine (CM), and wood particles mixed both of IG and CM with weight ratio of 1:1 (IC). The properties of the board were evaluated based on Japanese Industrial Standard. The main results obtained are as follows: the modulus of rupture values of the board manufactured with B and RS were larger than those of BL regardless of processing methods of raw materials. The modulus of elasticity values of the board manufactured with raw materials processed by using CM were smaller than those of processed by using IG and IC regardless of the types of raw materials. The internal bond strength values of composite board manufactured with B and RS were larger than that of standard value of type 18 Particleboard regardless of processing methods of raw materials. The thickness swelling values of all composite boards in this study were smaller than that of type 18 particleboard standard value.. |
| 13. |
Andi Hermawan, Takeshi Ohuchi, Noboru Fujimoto, Yasuhide Murase, Manufacture of composite board using wood prunings and waste porcelain stone, Journal of Wood Science, 10.1007/s10086-008-1000-6, 55, 1, 74-79, 2009.02, The objective of this study was to develop a method for the effective use of both pruned wood and porcelain stone scrap. Thus, we manufactured a wood-porcelain stone composite board, which has excellent waterproof property and incombustibility properties. In addition, we examined the conditions needed to manufacture the wood-porcelain stone composite board as a construction material and evaluated the physical and mechanical properties of this board based on the Japanese Industrial Standard. The main results obtained were as follows: the wood-porcelain stone composite board made from pruned wood and porcelain stone scrap had excellent thickness swelling performance and the board had incombustibility properties that were better than commercial oriented strand board. In both single-layer and three-layer composite boards with weight ratios of porcelain stone particles of 40%, the internal bond strength exceeded the standard value of type 18 particleboard of JIS A 5908. However, the bending properties of the composite board were inferior to the type 18 particleboard standard. Therefore, it will be necessary to improve the bending properties of the board by changing the particle sizes of both the porcelain stone scrap and the pruned wood component.. |
| 14. |
Jinji Piao, Noboru Fujimoto, Yasushi Yamamoto, Soji Nagata, Hybrid kiln drying system with radio frequency heating for hinoki boxed-heart timber with round edges, Journal of the Faculty of Agriculture, Kyushu University, 53, 2, 505-509, 2008.10, To avoid the formation of checks during the drying of hinoki (Chamaecyparis obtusa Endl.) boxedheart timber with round edges, a comparative investigation on the kiln drying and the hybrid drying, the high temperature and low humidity (HT/LH) treatment stage combined with radio frequency (RF) heating, was carried out in this study. The results showed that the hybrid drying could effectively prevent the occurrence of both surface checks and internal checks in the hinoki boxed-heart timber with round edges. Moreover, the hybrid drying time was significantly shortened to 15 hours. The combination of RF heating at the stage of HT/LH treatment resulted in at least following beneficial consequences: reduction of the surface temperature decreasing, attenuation of the tensile stress, promotion of the internal drying, relaxation of the moisture gradient, and inhibition on the extreme drying stress. Therefore, a wood drying strategy with high speed, free of both surface and internal checks could be realized through hybrid drying.. |
| 15. |
Takeshi Ohuchi, Han Chien Lin, Noboru Fujimoto, Yasuhide Murase, Development of automatic system for monitoring and removing of burr in side milling process of wood and wood-based materials, Journal of the Faculty of Agriculture, Kyushu University, 53, 1, 101-105, 2008.02, Computerized numerically controlled (CNC) routers have been used under hard processing conditions with the aim of raising productivity. Therefore, tool wear progresses rapidly, and burr formation occurs on the surface of wood and wood-based materials frequently. Because this burr formation greatly influences product quality and productivity, the development of a system that can monitor it automatically is needed. In this study, to monitor the burr formed because of tool wear, a charge-coupled device (CCD) vision sensor with high reliability in monitoring was installed in a CNC router, and a system for monitoring the burr formation in side milling and for removing it automatically was developed. In addition, verification experiments of this system were carried out. The main results obtained are as follow: The side milling system for monitoring burr formation was composed of a CCD vision sensor, a personal computer (PC) for CNC router control, and a monitoring PC to control other devices and collect sampling data for the burr formation. From the result of our verification experiment, it was found that this system could measure the area of the burr formed in side milling and remove it automatically.. |
| 16. |
Y. Katagiri, Noboru Fujimoto, Y. Murase, Effect of the treatment temperature on the surface drying set of sugi boxed-heart square timber, Drying Technology, 10.1080/07373930601184080, 25, 3, 507-510, 2007.03, High-temperature and controlled humidity treatment before drying has proven to be highly effective in preventing surface checks by forming drying sets in the surface layer of boxed-heart square timber in Japan. In this study, we examined the differences of the surface drying sets on sugi timber under different treatment temperatures. As a result, the width of a surface check after drying was much smaller at a treatment temperature of 120°C than at 80°C, and this indicates that the drying set with 120°C treatment would be larger than that with 80°C treatment. Also we observed that treatment temperature had a greater effect on the drying set as the drying advanced.. |
| 17. |
Jinji Piao, Noboru Fujimoto, Yasushi Yamamoto, Soji Nagata, Development of hybrid kiln drying system with radio frequency heating for the sugi boxed heart timber, Journal of the Faculty of Agriculture, Kyushu University, 52, 1, 117-121, 2007.02, In this study, proper applied stage of the radio-frequency (RF) heating during kiln drying based on the quality concerning the surface checks of the boxed heart timbers was examined. At the stage of the RF heating the moisture contents decreased clearly at the internal parts of timbers. The surface stress of the sugi (Cryptomeria japonica D. Don) boxed heart timber changed into the compression stress by the RF heating in any drying stage. The surface checks increased according to the decrease of the moisture content. However, the increase of the area and the width of the surface checks in the Link 3 were comparatively low, and the quality of these boxed heart timbers seemed relatively good. The amount of electric energy of RF heating in the Link 3 was fewer than that in the Link 1, 2.. |
| 18. |
Jinji Piao, Noboru Fujimoto, Kanehiro Oohashi, Mitsuru Tanikawa, Masashi Kitada, Hozumi Sonobe, Yo Ueda, Drying properties of Sugi round timber with microwave heating, Journal of the Faculty of Agriculture, Kyushu University, 51, 2, 345-349, 2006.10, Sugi round timbers injected with preservative are useful for outdoor playing and construction materials. To dry the Sugi round timbers for preservative injection, three drying methods including microwave drying, kiln drying and air drying were compared in this study. Using microwave drying, the timbers were dried within one day, but the other two drying methods required a much longer time. During most of the microwave drying process, the wood temperature appeared to be higher in the inner layer than in the outer layer. As a result, the inner layer moisture contents were significantly reduced by microwave drying, while kiln drying produced almost no decline in the inner layer moisture contents. In addition, although significant surface checks often occurred in timbers dried by kiln drying and air drying, microwave drying caused few surface checks. In contrast, internal checks were only observed in timbers treated by microwave drying. These results suggested that the microwave drying technique can improve the effectiveness of preservative injection in Sugi round timbers.. |
| 19. |
Noboru Fujimoto, Yuusuke Morita, Takeshi Oouchi, Han Chien Lin, Kanehiro Oohashi, Kazuyuki Kondo, Drying of sugi logs with microwave heating, Zairyo/Journal of the Society of Materials Science, Japan, 10.2472/jsms.54.371, 54, 4, 371-376, 2005.04, Sugi logs were dried with the microwave (MW) heating. The temperature and moisture content distributions in the logs were measured during MW heating. And the surface stresses were measured at the same time as released strains on the surfaces. As a result, the temperature in the center layer was higher than that in the outside layer during drying because of rapid temperature decrease for irradiation stop in intermittent heating system of MW. The moisture content in the center layer was relatively low at the end of drying. The surface stress of dried log was compression for the tangential direction related to surface checks. During seasoning after MW drying, the moisture was removed mainly in the surface layer, and the surface stress changed to tensile stress. As a result, the surface checks occurred for all logs after seasoning in about two or three months. Some dried logs had been sawn into the boxed-heart square timbers. Many surface checks appeared on these timbers because of the existence of internal checks of sugi logs, which occurred by the MW drying. These check widths did not change largely for the efficiently dried timbers as the core part of sugi logs after MW drying.. |
| 20. |
Hisato Oda, Yoshifumi Ebihara, Tadayoshi Sakoda, Noboru Fujimoto, Yasuhide Murase, Variation in Moisture Content of Sugi Boxed Heart Timber in Miyazaki Prefecture during Kiln Drying under High Temperature and Low Humidity II ‡. Distribution and change of moisture content, Mokuzai Gakkaishi/Journal of the Japan Wood Research Society, 10.2488/jwrs.51.227, 51, 4, 227-233, 2005.01, Sugi (Cryptomeria japonica D. Don) boxed heart timbers from Miyazaki prefecture were kiln-dried at low humidity under two high-temperature conditions. The distribution of moisture content, changes in moisture content and the generation of internal checks were examined. Our findings are summarized as follows: 1) In the examination with an intermediate period of steaming, a large difference in moisture content was observed depending on green timber weight. Each layer of timbers of 34 to 36 kg had a moisture content of about 6%, and layers of timber of 37 to 39 kg had a final moisture content ranging from about 6 to 40%. 2) In the examination with a surface-drying stage at a dry-bulb temperature of 75°C and a wet-bulb temperature of 68°C, variation of moisture content in the cross section were almost equalized during the steaming process that followed this stage. 3) The amount of moisture content reduction per hour during drying at a dry-bulb temperature of 120°C was about equal at 1.2 to 1.6% for both drying methods. 4) Internal checks seemed to be generated near moisture content of 30 to 40%.. |
| 21. |
Noboru Fujimoto, K. Tachiwana, K. Oouchi, Y. Mataki, Tension creep of surface layer and compression creep of inner layer perpendicular to the grain in sugi boxed-heart square timber, Zairyo/Journal of the Society of Materials Science, Japan, 10.2472/jsms.50.914, 50, 8, 914-919, 2001.01, Some creep tests were conducted to clarify the effect of temperature on the drying check of sugi (Cryptomeria japonica D. Don) boxed-heart square timbers during kiln drying. The tensile creep behaviors of tangential direction at the outside layer parts of sugi boxed-heart square timbers and the compression creep behaviors of radial direction at the inner parts of them were investigated. Creep strain and residual strain were larger at 80°C than at 40°C under constant moisture content. Under drying condition, these mechano-sorptive creep strains at 80°C and 40°C were almost same. The creep strains increased approximately like a straight line as the moisture content reduced in the area of moisture content less than 30%. Its gradient can be considered that there is no effect of the temperature. But initial elastic deformation at 80°C was larger than at 40°C. As a result, the relative creep in the high temperature showed lower than in the low temperature. After all, it was supposed that the temperature dependence factor for the restraint of surface check of boxed-heart square timber of sugi was elastic characteristic and was not creep characteristic. The value of creep compliance in compression for the radial direction at the part far from the pith showed relatively low during drying.. |
| 22. |
Noboru Fujimoto, Kensuke Goto, Yoshihiro Mataki, Fracture toughness of the surface layer of the boxed-heart square timber of sugi associated with drying check, Zairyo/Journal of the Society of Materials Science, Japan, 10.2472/jsms.48.223, 48, 3, 223-228, 1999.03, Fracture toughness tests were performed on the surface layer of boxed-heart square timber of sugi, after and during drying. Experiments were carried out using of notched tensile specimens with single edge. The critical stress intensity factor (KIc) in the TR system was investigated to clarify effects of drying temperature on resistance against drying surface check of the boxed-heart square timber of sugi. Timbers dried with temperatures of 20 °C and 80 °C had higher resistance against drying check than dried with temperature of 40 °C and 60 °C. AE cumulative events increased slowly at the occurrence state for the tension tests of the specimens dried with temperature of 20 °C and 80 °C, whose KIc values were relatively high. On the other hand, AE cumulative events increased relatively fast for the specimens dried with temperature of 40 °C and 60 °C. Cell-wall break type of micro-fracture occupied the most of fracture in the early wood, when the large amplitude of AE were detected in the early state. Therefore, it was found that the characteristics of AE were closely concerned with KIc values and micro-fracture. The KIc values of the fracture toughness decrease with drying until moisture content of 20%, because of drying stresses. After then, the KIc values increase rapidly with drying under moisture content of 20%. In the drying processes the KIc values have a tendency to be higher with lower drying temperature within this experiment conditions.. |
| 23. |
Noboru Fujimoto, Shuuzou Arita, Yoshihiro Mataki, Changes of dimension and stress in surface layer of sugi dried boxed-heart square timbers with a split liner under cyclic environment, Zairyo/Journal of the Society of Materials Science, Japan, 10.2472/jsms.46.390, 46, 4, 390-394, 1997.01, Dried boxed-heart square timbers of sugi with a split liner were tested for the dimensional stability and tangential stress in surface layer during environmental change. The tests were made under several cyclic conditions of temperature and humidity with reference to the actual day and night condition. The results obtained were as follows ; (1) The change in moisture content with environment was less than 1 % by the oven drying method and less than 4 % by the high frequency moisture meter method. At the same time, the shrinkage chandes of width were less than 0.4 % in the opposite directions for the fluted face and for the other three faces. (2) When the difference of equilibrium moisture content (ΔE.M.C.) between daytime and nighttime was over 4 %, tension stress appeared clearly in the surface layer after changing to the daytime condition. (3) The above daily change in stress behavior depended on the moisture condition of the dried timber. For the insufficient dried timber with a large moisture gradient, the tension stress in surface layer during the daytime condition increased enough to develope into check.. |
