Fig. 1

Elastic proportional limit surfaces for all failure planes. Ellipses show the transition from the elastic to the non-elastic region (proportional limit surfaces) calculated using the Tsai and Wu (1971) failure criterion with no interaction terms for all failure planes of green Pinus radiata core- and outer-wood. Axes show stress (σ) in the direction of the subscript, where two subscripts represent a shear stress is in the plane described by the subscripts. All directions not on the displayed axes are set to zero