TAILIEUCHUNG - Báo cáo khoa học: "The influence of wood quality on lumber drying distortion*"

Tuyển tập các báo cáo nghiên cứu về lâm nghiệp được đăng trên tạp chí lâm nghiệp quốc tế đề tài: "The influence of wood quality on lumber drying distortion. | Ann Sci For 1996 53 1177-1188 Elsevier INRA 1177 Original article The influence of wood quality on lumber drying distortion DJ Gown AN Haslett MO Kimberley DL McConchie Forest Research Institute PO Box 3020 Rotorua New Zealand Received 4 July 1995 accepted 11 March 1996 Summary - Commercial experience with the sawing of logs from fast-grown plantations has shown that there can be significant drying distortion associated with the presence of juvenile wood. In New Zealand this is a growing concern due to the reduction of rotation ages for radiata pine Pinus radiata D Don to around 25-30 years. The purpose of this analysis was to use the results of sawing studies to identify some of the major factors affecting distortion of the final product structural lumber in this case and test the feasibility of modeling the relationships. Analyses of some 9 000 individual boards 100 X 40 and 100 X 50 mm from 1 000 logs indicated the need to take into account a range of factors relating to the raw material logs secondary processing technology sawing pattern drying method and the influence of planing product lumber dimensions and standards grading rules . The strong propensity for lumber from small diameter and physiologically young logs to degrade was confirmed and over 90 of the problem was related to twist rather than crook or bow. In the worst cases small juvenile logs low temperature drying no planing up to 80 of the boards were categorized as rejects . At the other extreme large diameter mature logs dried according to recommended practices and those that were machined to final size showed around a 5 rate of rejection. Diameter was shown to be the most influential log property. Spiral grain was also important due to its influence on twist during drying it is greatest in juvenile wood which forms a greater proportion in small diameter logs. The analyses showed that both diameter and spiral grain are related to twist. Unfortunately spiral grain is a little known feature of .

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