Papers by Author: Pentti O. Kettunen

Abstract: Two man-made wooden objects, called here a “boat” and an “outrigger”, were found above one another in 2004 and 2006 in Kuusamo, Finland. A layer of shore front mud and turf covered them entirely. With partial excavations, samples were taken for age determination and structural studies from both of the items. As measured by the radiocarbon method with a probability of 95.4 %, the items appear to be from periods 5480 – 5300 CalBC and 5025 – 4770 CalBC for the boat and the outrigger, respectively.

Abstract: Strength values of the sapwood of Siberian yellow pine were measured in a system with orthogonal coordinates along the axial, radial, and tangential directions of the cell structure. Highest strength was the axial normal strength and lowest the tangential normal strength. The difference between these two values was 87-fold. Shear strength values remained between the two normal strength values. The highest shear strength appeared in tangential direction across the reinforcing fibers, i.e., on the plane perpendicular to the axial direction. Lowest shear strength appeared in tangential direction on the plane perpendicular to radial direction. The variations are due to orientation of cells and of fiber reinforcement in the cell wall laminas, especially in the middle layer of the secondary cell wall.

Abstract: The present background description concentrates on the structure of wood xylem, on the mechanical strength properties under monotonic external loading, on the degradation of the structure of wood and somewhat also on the influence of thermal treatment (heat treatment) on the structure and properties of wood. The presentation is largely based on a recent publication of the author /1/. In this manner, the description tries to illustrate the status of the present general knowledge in the fields, into which the present papers bring new results and ideas for a better understanding of the structure and behavior of wood.