Studies on Birch Wood Viscoelastic Properties

The paper presents study methodic on birch wood viscoelasticity. For the study, specimens of (0.35×0.04×0.014) m dimensions were used. They were sawn in a certain order from different places of a log, called the “butt end”, “centre” and “top”. For this purpose a log of five meter was used. The studies were based on the methodic of resonance vibrations of a beam type body. Having ascertained the value of resonance frequency, dynamic modulus of elasticity (elastic properties) of the specimen and coefficient of damping tgδ (viscous properties) were calculated. In this way, dependencies of the change of these parameters in different directions of the log, evaluating the character of annual rings and distribution pattern, were obtained. It was found, that the greatest modulus of elasticity value (25201 MPa) is obtained in the centre of the log, while the least (20942 MPa) is in the butt end. Coefficient of damping going from the butt end towards the top changes from 0.011 to 0.013. In most cases elastic properties are exchanged by damping properties. The obtained data may be used selecting wood to produce separate details of wooden articles