The effect of the growth ring orientation on spring-back and set-recovery in surface-densified wood

Abstract Wood under thermo-mechanical densification behaves differently depending on the cross-sectional growth ring orientation (GRO) relative to direction of compression. This influences degree cell damage, but also shape-memory effects occurring when compression load is released (spring-back) and timber re-moistened (set-recovery). To study how GRO effects, Scots pine specimens were separated into three distinct groups (Flat, Inclined, Hybrid) then thermo-mechanically surface-densified. Spring-back set-recovery determined by thickness measurements digital image correlation. A parallel densified surface, resulted in a low spring-back high which uniform over width specimen. Specimens with between 15 45° surface showed set-recovery, indicating cell-wall damage. mainly occurred non-plasticised region immediately below heated elasto-plastic rolling-shear deformation along individual rings occurred. The softwood subjected determines if an applied results rolling shear-deformation or radial turn where cross-section process cells deform this occurs above glass-transition temperature.