Abstract

An integral calculation method (ICM) is presented for fully estimating the fiber orientation and fundamental physical and mechanical properties of softwood (SW) logs and lumber. The proposed ICM reproduces with great detail the most important anatomical features of SW, including annual rings, seasonal variations, main growth patterns (straight, spiral, and interlocked grain), and especially fiber distortions due to knot clusters for each annual ring. The failure load of the lumber has been predicted with an absolute error of 10.2%. In addition, the ICM has shown very strong robustness and high calculation speed as most of the calculations are performed analytically, and only one final simplistic computation is conducted by finite element analysis (FEA). This article describes the proposed ICM in detail and shows the initial verification with experiments. The ICM should contribute not only to lumber research and grading but also to research and optimization of logging and sawing industrial processes.