%0 Research article
%T Stress intensity factor of wood from crack-tip displacement fields obtained from digital image processing
%A Samarasinghe, Sandhya
%A Kulasiri, Don
%D 2004
%J Silva Fennica
%V 38
%N 3
%R doi:10.14214/sf.415
%U https://silvafennica.fi/article/415
%X Stress intensity factor of radiata pine (Pinus radiata) in  Tangential-Longitudinal opening mode was determined from crack-tip  displacement fields obtained from digital image correlation in  conjunction with orthotropic fracture theory. For lower loads,  experiments agreed with the linear elastic fracture theory but for  higher loads, stress intensity factor and load relationship was  nonlinear. For 41% of the specimens tested, tip-displacement based  stress intensity factor agreed with that based on the ASTM standard  formula for lower loads but deviated for higher loads closer to failure.  The tip displacement plots showed that the nonlinear behaviour is due  to large displacements which we attributed to large plastic deformations  and/or micro-cracking in this region. The other 59% specimens showed a  similar trend except that the crack-tip based stress intensity factor  was consistently higher than the value obtained from the standard  formula. The fracture toughness from tip displacements was larger than  the standard values for all specimens and the two were related by a  logarithmic function with an R2 of 0.61. The study also established that  fracture toughness increases with the angle of inclination of the  original crack plane to the Radial Longitudinal plane.