STRENGTH GRADING OF WET NORWAY SPRUCE SIDE BOARDS BY USE OF AXIAL DYNAMIC EXCITATION

摘要

Strength grading of Norway spruce side boards in the wet state was investigated. For a batch of 58 boards, densities and dynamic modulus of elasticity in the axial direction, MOE_(dyn), were determined in the wet state. The boards were then split into two parts and the procedure of determining MOE_(dyn) was repeated both before and after the boards were dried to a target moisture content of 12 %. Tensile strength of the split boards was measured and its relation to MOE_(dyn) for both split and unsplit boards determined. A so called reversed lamination effect on the stiffness caused by the splitting of boards into two parts was also evaluated. The results show that strength grading of split boards in the wet state could give just as good results as grading performed after drying. The reversed lamination effect on the stiffness of split boards was found to be of lower order.