High-Temperature Drying and Equalizing: Effects on Stress Relief in Yellow-Poplar Lumber
Keywords:
Kiln-drying, growth stresses, lignin plasticizationAbstract
Warp caused by longitudinal growth stress has limited the use of hardwoods for some products such as structural lumber. This study evaluates the effects of high-temperature drying and equalizing times on relief of longitudinal growth stress. Small-diameter yellow-poplar logs were sawn into flitches for evaluation of total stress levels in green flitches and final stress levels in dried flitches.
High temperatures evaluated were 200 F (93 C), 240 F (116 C), 260 F (127 C) and 290 F (143 C). Equalizing times were 10, 20, 40, and 100 hours at 10% equilibrium moisture content.
Average adjusted absolute stresses for center flitches in the green conditions were about 525 psi (362 MPa). Average absolute stresses were 210 psi (145 MPa) for all high-temperature dried materials without equalizing, and 154 psi (106 MPa) for all equalized materials.
There were no well-correlated relationships of stress between the individual high-temperature or equalizing treatments and controls or green flitches. Possible causes for lack of correlation and suggestions for further research are discussed.
References
American Society for Testing and Materials. 1983. Standard methods for establishing structural grades and related allowable properties for visually graded lumber. ASTM Stand. Desig. D 245- 81. Annual Book of ASTM Standards, Part 22. ASTM, Philadelphia, PA.nBoone, R. S., and R. R. Maeglin. 1980. High-temperature drying of 7/4 yellow-poplar flitches for S-D-R studs. USDA Forest Serv. Res. Pap. FPL 365. Forest Prod. Lab., Madison, WI.nBoyd, J. D. 1950. Tree growth stresses. I. Growth stress evaluation. Aust. J. Sci. Res.B3(3):270-293.nBoyd, J. D., and K. B. Schuster. 1972. Tree growth stresses. Part IV: Visco-elastic strain recovery. Wood Sci. Technol.6(2):95-120.nDinwoodie, J. M. 1966. Growth stresses in timber—A review of literature, J. For.39(2): 160-170.nGoring, D. A. I. 1971. Polymer properties of lignin and lignin derivatives. Pages 695-768 in K. V. Sarkanen and C. H. Ludwig, eds., Lignins—Occurrence, formation, structure and reactions. Wiley- Interscience, New York, NY. 916 pp.nHann, R. A. 1969. Longitudinal shrinkage in seven species of wood. USDA Forest Serv. Res. Note FPL-0203. Forest Prod. Lab., Madison, WI.nHaygreen, J. A., and J. L. Bowyer. 1982. Forest products and wood science: An introduction. Iowa State University Press, Ames, IA. 495 pp.nJacobs, M. R. 1938. The fibre tension of woody stems, with special reference to the genus Eucalyptus. Commonw. For. Bur. Aust. Bull. No. 22. Commonwealth Forestry Bureau, Canberra, Australia. 39 pp.nJacobs, M. R. 1945. The growth stresses of woody stems. Commonw. For. Bur. Aust. Bull. No. 28. Commonwealth Forestry Bureau, Canberra, Australia. 67 pp.nKoch, C. B., and W. T. Rousis. 1977. Yield of yellow-poplar structural dimension from log grade logs. Forest Prod. J.27(4):44-48.nKubler, H. 1980. Wood as a building and hobby material. John Wiley and Sons, New York, NY. 256 pp.nMaeglin, R. R. 1978. Yellow-poplar studs by S-D-R. So. Lbrmn.237(2944):58-60.nMaeglin, R. R., and R. S. Boone. 1980. High quality studs from small hardwoods by the S-D-R process. Pages 36-51 in Proc. 23rd Joint Mtg. of Midwest and Wis. Mich. Wood Season. Assoc. [Michicot, WI] Midwest Wood Seasoning Assoc., P.O. Box 5130, Madison, WI.nMaeglin, R. R., and R. S. Boone. 1983. Manufacture of quality yellow-poplar studs using the Saw-Dry-Rip (S-D-R) concept. Forest Prod. J.33(3): 10-18.nNicholson, J. E., W. E. Hillis, and N. Ditchburne. 1975. Some tree growth-wood property relationships of eucalypts. Can. J. For. Res.5:424-432.nNorthern Hardwood and Pine Manufacturers Association. 1978. Standard Grading Rules. NHPMA, Green Bay, WI. 125 pp.nPanshin, A. J., and C. de Zeeuw. 1980. Textbook of wood technology, 4th ed. McGraw-Hill Book Co., New York, NY. 722 pp.nPost, I. L., J. C. Atherton, C. P. Vendhan, and R. R. Archer. 1980. An extension of Jacobs' method for measuring residual growth strains in logs. Wood Sci. Technol.14(4):289-296.nRasmussen, E. F. 1961. Dry kiln operator's manual. USDA Agric. Handb. No. 188. U.S. Gov't. Printing Office, Washington, DC. 197 pp.nSkolmen, R. G. 1967. Heating logs… to relieve growth stresses. For. Prod. J.17(7):41-42.nU.S. Department of Agriculture, Forest Service, Forest Prod. Lab. 1974. Wood handbook—Wood as an engineering material. USDA Agric. Handb. No. 72 rev. U.S. Gov't. Printing Office, Washington, DC.n
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