Off-axis fatigue loading of steamed wood

Cyclical off-axis compression was applied to steamed Spruce wood in uniaxial strain under stress control. The strain level is a step function of stress level and test duration. Energy dissipation is negligible when the stress amplitude in relation to the greatest compressive stress is small, regardless of the applied stress level. There is a significant energy dissipation when the stress amplitude in relation to greatest applied compressive stress is large, regardless of stress level. Dynamic stiffness appearing during the dynamic loading strongly depends on applied stress and stress amplitude. Small-strain stiffness deteriorated during any dynamic loading experiment, apparently depending on the greatest compressive strain appearing during loading. Also plastic strain appears to depend on the strain appearing during loading. Thus stiffness decrement and plastic strain do not appear to reflect the variety of material reactions to fatigue treatments.