Abstract
A new test method for wood splitting was invented, in that hydrostatic pressure is introduced into a circular hole of a wood plate until splitting fracture takes place. Water pressure is applied to the wall of the hole through a soft balloon made of rubber, which generates uniform radial compression on the circumferential wall without friction. The splitting occurred at the coordinate where the tangent of the circle is right-angled to the grain of the wood, which was observed in the all specimens of Japanese cedar and SPF. The stresses around the hole were analyzed by means of Ikeda's formula in consideration of orthotropic elasticity of the woods, which revealed that the stress distribution around the circular hole is nearly equal to that of an isotropic plate. The stress criteria of fracture by Norris, Tsai-Hill, and Hoffman were examined, which demonstrated that the Hoffman equation incorporating tensile and compressive strengths is most favorable to predict the splitting strength of the holed wood plates subjected to the interior pressure.
