Perpendicular-to-grain mechanical properties and constitutive model of wood under cyclic loading
The cyclic mechanical behavior and constitutive model of wood are the basis for the mechanical analysis of timber structures under earthquake and fatigue loads.A dog bone shaped specimen and its supporting fixture were designed and manufactured for transverse cyclic loading.A total of 44 specimens were tested under cyclic compression and cyclic tension compression based on the three types of transverse samples with radial,off-axis 60° and tangential directions,respectively.The deformation characteristics,failure modes,full stress-strain curve features and unloading stiffness changes under different loading conditions were analyzed.The relationship between the compression unloading residual strain,the strain of tension unloading started points,tension unloading residual strain and the strain of compression unloading control points was quantitatively characterized.The results show that the strain hardening characteristics of the monotonic compression stress-strain curves of the wood specimens with transverse grain and off-axis at 60° are obvious after the yield point,while the tangential compression specimens show an obvious strain softening phenomenon.The characteristics of the cyclic compression skeleton curves are similar to the monotonic compression curves of wood.The stiffness of the reverse reloading curves after unloading is significantly degraded.On this basis,the monotonic and cyclic constitutive model of wood was established,and its correctness was verified by experiments.The research results can provide a good basis for the mechanical analysis of timber structures subjected to cyclic loading.
woodperpendicular-to-graincyclic loadingmechanical testmechanical propertiesconstitutive model
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