Acta Scientiarum Polonorum
Silvarum Colendarum Ratio et Industria Lignaria

The study was undertaken to show the possibility of wood swelling pressure determination on the basis of the time course of its mechano-sorptive creep induced by bending stress of different values and simultaneous moistening of the compressed zone.The creep was induced in the conditions of three-point bending of beech wood (Fagus sylvatica L.). The bending pressure applied in the radial direction was of the magnitude of 0.05, 0.1 and 0.15 of the mean destroying stress determined for the samples of moisture content of about 7%. Immediately after application of loading the samples were subjected to asymmetric moistening in the zone of compressive stress. For the sake of comparison also the free sorptive deformation of analogous samples was observed. On the basis of the linear relations between the deformation (recorded at specific time intervals during the process of mechano-sorptive creep) and the bending stress applied, it was possible to determine the values of the stress at which the samples would remain in the non-deformed state despite their asymmetric moistening. The maximum swelling pressure determined in this way is by about 50% greater than that found in the direct way.