P. Helnwein, J. Eberhardsteiner, A. Hanhijärvi:
"Constitutive Model for the Short-Term Failure Analysis of Wood Under Multiaxial States of Stress: Effect of Radial Compression";
in: "Proceedings of the First International Conference of the European Society for Wood Mechanics", P. Navi (Hrg.); European Society for Wood Mechanics, Swiss Federal Institute of Technology (EPFL), Repographie EPFL, Lausanne, Switzerland, 2002, ISBN: 2-9700377-0-x, S. 285 - 294.
Recent biaxial experiments by Eberhardsteiner, et al. on spruce show that consideration of an elliptic failure surface after Tsai and Wu and an elastic model for stress states within this envelope causes an insufficient description of the mechanical behavior. As compression perpendicular to grain occurs, a nonlinear stress path results from a proportional biaxial strain path. Investigation of a characteristic sample with respect to loading-unloading-reloading cycles for states of stress below failure reveals behavior similar to what is known as hardening type plasticity.
The experimentally observed mechanical behavior will be described by means of a multi-surface plasticity model addressing both failure and nonlinear stress response below failure as separate mechanisms. Prediction of failure will be performed by means of a second-order failure envelope according to Tsai and Wu. The nonlinear stress response has to be covered by an orthotropic hardening type plasticity model.
Since available experimental data cover only plane stress in the LR-plane, both orthotropic failure and yield surfaces, resprespectively, are restricted to this case.
Keywords: plasticity, model, wood, radial compression, failure, wood