Anisotropic viscoelastic properties of cortical bone

Relaxation Young’s modulus of cortical bone was investigated for two different directions with respect to the longitudinal axis of bone (bone axis, BA): the modulus parallel (P) and normal (N) to the BA. The relaxation modulus was analyzed by fitting to the empirical equation previously proposed for cortical bones, i.e., a linear combination of two Kohlraush–Williams–Watts (KWW) functions (Iyo et al., 2003. Biorheology, submitted):E(t)=E0{A1 exp[−(t/τ1)β]+(1−A1) exp[−(t/τ2)γ]}, [0