Nondestructive Testing And Steam Explosion Pre-Treatments For Sub-alpine Fir Wet-pocket Lumber

(1) Stress wave nondestructive evaluation method for detection of wetwood in sub-alpine fir boards at different drying phases is investigated . The results show that stress wave travel time has potential to be used to identify wet-wood in green lumber in parallel to grain at sawmills.(2) A newly designed high x-ray energy industrial computed tomography ( CT) scanner provide a new nondestructive detection method for sub-alpine fir wetwood lumber. The results show that comparing to the stress wave method, CT scanning provides clear interior features of wood and wood defect images. The higher moisture content in the lumber is, the more intensity (light density) in CT image is observed.(3) Bacterial ,like flakily, water socked, and mass are found in pit membrane in. wetwood of Sub-alpine Fir by using Scanning Electronic Microscope. Most of bordered-pit membranes in normal wood are un-aspirated at green condition and the proportions of aspirated pits in early wood and latewood counted only 6.8% and 13.4% respectively. Nevertheless, most of bordered-pit membranes in wet wood are aspirated at green condition and the proportions of aspirated pits counted at 77.7% and 72.1% respectively. The problem of hard-to-dry for sub-alpine fir could be reasoned from the considerable amount of aspirated pit membranes in wetwood.(4) Five types of partial reposition and damages of aspirated pits membrane were generalized from the steam explosion treated groups. The treatments in Groups A, B, C and D, made some aspirated pits un-aspirated with different extents so that the moisture passages were opened.(5 ) Comparing to the control Group E, permeability of Groups A, B and C is amplified after steam explosion treatment. And the permeability enlarges as the pressure / temperature / cycles of explosion increase. A statistical analysis shows that there is a significant difference in permeability between the steam-explosion treated groups and control group.(6) The dryability of sub-alpine fir was increased and more uniform final MC distribution is obtained through the steam explosion treatment.There is no significant difference in shrinkage of width and thickness between the conservation and accelerated schedules for treated lumber drying. The most drying shrinkage is found in Group D. No significant differences in drying shrinkage are found in this study...