Yield behavior of wood under combined static axial force and torque

Abstract

We have examined the yield behavior of wood (Japanese cypress and Japanese beech) under combined static axial force and torque. In order to take the anisotropy of the wood into consideration, the specimen had a rectangular cross-section with one of its major axis lying in the fiber (longitudinal) direction. The axial force was applied in the fiber direction (along L) and torque was applied on an axis lying in the same direction as L. A combined loading test was performed according to the proportional deformation loading method. The results obtained are summarized as follows. (1) The yield condition of wood under combined axial-shear stress can be expressed by several well-known yield criteria. (2) The determinations of yield points are more influenced by torsion than axial force. (3) Japanese cypress deforms elastically compared with Japanese beech. (4) It is suggested that the equivalent stress-equivalent strain relation could be used at the determination of the yield point.