Some Physical Processes Involved in Deformation and Fracture

The effects of strain rate, of moisture content, and of tracheid structure on the transverse fracture properties of Pinus Radiata have been studied. Small rectangular blocks were loaded to failure in transverse tension, with the conditions of fracture being varied as follows: (i) strain raite - at 2 x 10 caret-6 sec caret-1, and from 10 caret-5 to 10 caret 2 sec caret-1 in decade steps , (ii) moisture content - airdry (12.7%) and saturated, and (iii) structure - springwood and summerwood. Microscopical examination (both scanning electron and optical) of the surfaces produced by the facture showed that the cellular level, either of two types of failure could occur. These are called transwall and intrawall; transwall is the longitudinal splitting of a tracheid wall, and intrawall is a splitting between adjacent tracheids.