Computational analysis of quality reduction during drying of lumber due to irrecoverable deformation. II: Algorithmic aspects and practical application

This paper describes the development of an efficient numerical integration algorithm for an orthotropic viscoelastic-mechanosorptive-plastic material model for wood, which was presented in Part I of this serial. This development utilizes both a semianalytical algorithm for the viscoelastic parts, and the return-mapping algorithm known from plasticity for the mechanosorptive-plastic part of the model. This yields an easily computed, closed form expression for the consistent tangent operator, and, as a consequence, a quadratic rate of asymptotic convergence on the global level of the incremental-iterative analysis by means of the FEM. To prove the practical applicability of the presented formulation, a numerical study of the so-called case-hardening phenomenon as observed on fast dried pine wood was performed. Selected results are presented and discussed.