CAPABILITIES OF THE INTERNAL FRICTION METHOD FOR DETECTING INTERNAL STRESSES IN WOOD

The paper investigates the capabilities of the internal friction method for detecting and determining internal stresses in wood based on the analysis of the logarithmic damping decrement δ of bending vibrations. The experiment was conducted on a free bending vibration test setup using samples of natural and bog oak in the radial and tangential directions. It was found that an increase in internal stresses leads to a corresponding increase in δ by 6–9%, with the highest values found for the tangential direction of bog oak. The results confirm the sensitivity of the internal friction method to microdefects and anisotropy of wood, which is consistent with the mechanisms of internal energy dissipation at the level of wood fibers. This method may be promising for non-destructive testing of stresses in building and loaded wooden structures.