Mechano-sorptive experiments perpendicular to grain under tensile and compressive loads

The present paper is part of a study concerning the long-term deformations and stresses in wood perpendicular to grain when subjected to variations of humidity. Experiments under sustained loading both in tension and compress ion are described. The effect of different humidity cycles, slow and fast c ycles in high and low humidity ranges, on the deformations is studied. It c an be observed from the test results, that the mechano-sorptive strains are highly significant, about five times the elastic deformation, although the load level is low and only a single humidity cycle is induced. The deforma tions are slightly higher in compression than in tension. The moisture rang e, where the humidity cycle occurred, did not have any major influence. The deformation was mostly dependant on the magnitude of the moisture change. The speed of the humidity cycle did not show any effect on the induced defo rmations over most of the humidity range, at the high humidity end some rat e effects could be noticed.