This report describes a mathematical model for fatigue strength of cellulosic materials under sinusoidal loading. The model is based on the Reiner-Weissenberg thermodynamic theory of strength in conjunction with a nonlinear Eyring's three-element model. This theory states that failure depends on a maximum value of the intrinsic free energy that can be stored elastically in a volume element of the material. The three-element mechanical model, which consists of a linear spring in series with a parallel array of another linear spring and an Eyring dashpot, provides a good description of rheological material properties. The strength model system was able to predict rupture occurrence of polymers and wood structural members under constant and ramp loading with satisfactory results. For sinusoidal loading, the present study shows that the strength model system can predict time at fracture as a function of applied mean stress, amplitude of cyclic stress, and stress frequency. Numerical examples with model parameters evaluated for Douglas-fir beams are presented.
|Original language||English (US)|
|Number of pages||9|
|Journal||American Society of Mechanical Engineers, Applied Mechanics Division, AMD|
|State||Published - Jan 1 1995|
|Event||Proceedings of the 1995 Joint ASME Applied Mechanics and Materials Summer Meeting - Los Angeles, CA, USA|
Duration: Jun 28 1995 → Jun 30 1995