Modelling crack propagation due to growth stress release in round wood

Abstract
The propagation of heart cracks at log-ends due to growth stress release was simulated numerically based on the application of Griffith theory. The elastic properties of the green wood were described through empirical correlations with density distinguishing hardwoods and softwoods. Fixed levels of surface residual strains and a given type of initial growth stress distribution were assumed. The propagation criteria was based on the maximisation of elastic release energy rate (G). Perfect axisymmetry was compared to the case of a marked reaction wood sector : the simulation confirmed the observed fact that in hardwoods, the presence of tension wood increases considerably the cracking risk, while it is reduced with the compression wood of softwoods. By comparison of the calculated G to experimental data of toughness (G ), our calculations suggest that not only higher log diameter but also higher wood density should result in more severe log-end cracks.