Effect of temperature on thermal stresses across the grain of wood. Preliminary study

The values of maximal thermal stresses in oven dry beech wood (Fagus sylvatica L.) was determinated by means of dumping thermal linear deformations in the radial and tangential directions during heating samples from the room temperature 20 degrees C to the temperature of 40, 60, 80 and 100 degrees C. It results from the experimental data that with the rise of heating temperature of wood the value of thermal stresses increases. The maximal thermal stresses determined for beech wood heated in the given of temperatures are ranging for the radial direction from 0.39 MPa (at 40 degrees C) to 1.40 MPa (at 100 degrees C), and for the tangential direction from 0.30 MPa to 1.21 MPa respectivelly. The time needed for appearance of the maximal thermal stresses is 5 to 6 minutes find does not depend on the anatomical direction of wood or heating temperature. The time necessary for wood to achieve to maximal value of sigma* depends on the size of cross-section of the heated sample.