HYGROTHERMAL RECOVERY OF GREEN WOOD .2. T RANSVERSE VARIATIONS IN CHESTNUT AND SPRUCE AND MODELING OF THE STEAMING-INDUCED HEART CHECKING

Hygrothermal recovery of green wood. II. Transverse variations in ches tnut and spruce and modelling of the steaming-induced heart checking. Hygrothermal recovery of green wood (HTR) explains heart checking indu ced by log steaming. If was measured at 80 degrees C in the 3 principa l directions of Chestnut (Castanea sativa Mill) and Spruce (Picea abie s Karst) using 2 complementary cutting procedures to extract clear-woo d specimens from parallel-faced disks. Strain levels obtained were abo ut -0.1% in radial direction and +/-0.1% in longitudinal direction. In the tangential direction the stain level was 0.3-0.4% for Spruce, wit hout influence of radial position. in Chesnut it varied from 0.4% near the periphery to 0.6% near the pith, was higher in tension wood and s maller in opposite wood, and fell by a half after 8 months water stora ge. In the numerical approach of heart checking induced by growth stre ss and steaming, the progress of heart checks was simulated by opening a central hole allowing the transverse stresses to remain within limi ts of strength criteria.