Creep Investigations of the Lignostone Under Tension and Torsion
Specimens of the beech-wood lignostone are tested for creep under simple tension along the grains and torsion at room temperature. The creep strains 2Е12(t) generated by pure torsion in the shearing stress range σ12 = (0.4 – 0.6)R12 (where R12 is the shearing strength) are found to be nonlinear. Similarly, the creep strains ε11(t) generated by simple tension in the normal stress range σ11 = (0.2 ∕ 0.35) R11 where R11 is the tensile strength, are also nonlinear. To describe those nonlinear behaviour the nonlinear viscoelasticity theory is employed and the similarity of the creep curves is used. Correct description of the considered phenomena is obtained.
M.CZECH, Description of stress relaxation of the lignostone with the use of the standard model [in Polish], II Symp – Rheology of Wood and Timber Structures, 69-75, Poznań 1986.
F.KOLMANN, Rheologie and Strukturfestigkeit von Holz als Rols und Werkstoff, 3, 1961.
B.T.OGARKOV, Theory of elastic behaviour of wood [in Russian], Żur. techn. fiz., 27, 1118-1120, 1957.
W.RYBARCZYK, Studies to formulae a mathematical model of mechanical-moisture properties of some wooden materials, [in Polish], Prace Inst. Technol, Drewna, 20, 2, 17-138, 1973.
M.SZOSTAK, Influence of humidity changes on the rheological properties of pine wood compressed across the grains [in Polish], Prace Inst. Technol. Drewna, 16, 2, 79-128, 1969.