A numerical simulation tool for wood grading: model validation and parameter studies

Growth irregularities such as knots always result in a pronounced reduction in strength in wooden boards. The presented paper deals with the experimental validation of a newly developed numerical simulation tool (Hackspiel et al., Wood Sci Techol, submitted, 2013 ) which allows the investigation of such defects by means of physically based numerical simulations. Thereby, advanced models for the description of the three-dimensional fiber course and for the mechanical material behavior are used. The stepwise validation covers the validation of the model for the elastic behavior covering the model for the grain course in the first place. For the validation of the model’s strength prediction capabilities, a total number of 52 boards were tested in tension and bending. The corresponding strength predicted by the simulation tool showed good agreement with the test results. The validated tool was then used to perform parameter studies in which the influence of various knot-related parameters on strength was investigated. The observed trends help to identify decisive knot parameters for board strength, which should receive particular attention in the grading process.