Effects of Boiling , Steaming , and Chemical Treatment on Solid Wood Bending of Quercus acutissima Carr . and Pinus densiflora S . et Z . = Effects of Boiling , Steaming , and Chemical Treatment on Solid Wood Bending of Quercus acutissima Carr . and Pinus densiflora S . et Z .

다국어 초록 (Multilingual Abstract)

This study was performed to investigate: (i) the bending processing properties of silk worm oak (Quercus acutissima Carr.) and Korean red pine (Pinus densiflora S. et Z.) by boiling and steaming treatments; (ii) the effects of interrelated factors sapwood and heartwood, annual ring placement, softening temperature and time, moisture content, and wood defects - on bending processing properties; (iii) the changing rates of bending radii after release from a tension strap, and (iv) the improving methods of bending process by treatment with chemicals. The size of specimens tested was 15 × 15 × 350㎜ for boiling and steaming treatment and 5 × 10 × 200㎜ for treatments with chemicals. The specimens were green for boiling treatments and dried to 15 percent for steaming treatments. The specimens for treatments with chemicals were soaked in saturated urea solution, 35 percent formaldehyde solution, 25 percent polyethylene giycol -400 solution, and 25 percent ammonium hydroxide solution for 5 days and immediately followed the bending process, respectively. The results obtained were as follows; 1. The internal temperature of silk worm oak and Korean red pine by boiling and steaming time was raised slowly to 30℃ but rapidly from 30℃ to 80-90℃ and then slowly from 80-90℃ to 100℃. 2. The softening time required to the final temperature was directly proportional to the thickness of specimen. The time required from 25℃ to 100℃ for 15㎜-squared specimen was 9.6-11.2 minutes in silk worm oak and 7.6-8.1 minutes in Korean red pine. 3. The moisture content (M.C.) of specimen by steaming time was increased rapidly first 4 minutes in the both species, and moderately from 4 to 20 minutes and then slowly and constantly in silk worm oak, and moderately from 4 to 15 minutes and then slowly and constantly in Korean red pine. The M.C, of 15mm-squared specimen in 50 minutes of steaming was increased to 18.6 percent in the oak and 22.4 percent in the pine from the initial conditioned M.C. of 15 percent. The rate of moisture absorption measured was therefore faster in the pine than in the oak. 4. The mechanical properties of the both species were decreased significantly with the increase of boiling time. The decrement by the boiling treatment for 60 minutes was measured to 36.65.0 percent in compressive strength, 12.5-17.5 percent in tensile strength, 31.640.9 percent in modulus of rupture, and 23.3-34.6 percent in modulus of elasticity. 5. The minimum bending radius (M.B.R.) of sapwood and heartwood was 60-80 ㎜ and 90 ㎜ in silk worm oak, and 260 - 300 ㎜ and 280 - 300 ㎜ in Korean red pine, respectively. Therefore, the both species showed better bending processing properties in sapwood than in heartwood. 6. The M.B.R. of edge-grained and flat-grained specimen in silk worm oak was 60-80 ㎜, but the M.B.R. in Korean red pine was 240-280 ㎜ and 260-360 ㎜, respectively. Comparing the M.B.R. of edge-grained with flat-grained specimen, in the pine the edge-grained showed better bending processing property than the flat-grained. 7. The bending processing properties of the both species were improved by the rising of softening temperature from 40℃ to 100℃. The minimum softening temperature for bending was 90℃ in silk worm oak and 80℃ in Korean red pine, and the dependency of softening temperature for bending was therefore higher in the oak than in the pine. 8. The bending processing properties of the both species were improved by the increase of softening time as well as temperature, but even after the internal temperature of specimen reaching to the final temperature, somewhat prolonged softening was required to obtain the best plastic conditions. The minimum softening time for bending of 15 ㎜-squared silk worm oak and Korean red pine specimen was 15 and 10 minutes in the boiling treatment, and 30 and 20 minutes in the steaming treatment, respectively. 9. The optimum M.C. for bending of silk worm oak 20 percent, and the M.C. above fib