Fatigue and Heating in the Non-Linear Region for Wood

Fatigue behavior and heating under cyclic deflection in the non-linear region is examined. Cyclic deflection in cantilever bending causes a local temperature increase and a characteristic reduction in relative stress, σ/σ 0 . Temperature increase versus the logarithmic cyclic deflection number, log N, shows a curve with a peak. This maximum is explained by the viscosity change due to moisture movement and vaporization by heating. The σ/σ 0 curves with log N consist of three regions : the first plateau (process A), the slanting straight line (process B), and the second plateau (process C). Process A is the retardation period for sufficient heating. Process B and process C are due to the mechano-sorptive effect and due to residual deflection increasing, respectively.