The origin of nonlinear elasticity and hysteresis in complex medium is a subject of intensive studies since the last decades. In the case of biological medium, this mechanism of ageing occurs at different time and space scales. The ageing behavior of skin was less studied in a multiscale framework, since it was studied several times within research devoted to concrete[1]. It was found that degradation processes can be coupled with the viscoelastic behavior of the medium itself.

The multiscale properties should be extracted with multiscale experimentations. The chosen experimentation presented elsewhere[2] enables to extract the multiscale properties of the skin. The use of TR-NEWS ultrasonic device developed for Non Destructive Testing (NDT) was chosen in order to measure damage or aging coming from hysteresis behavior.

The corresponding hysteresis behavior coming from the complex loading of a porcine skin tissues was assessed by means of Preisach-Mayergoyz (PM) space, which can be expressed in the form of weight combination of various hysterons. The specific statistical distances called $\phi$-divergences were used as the alternative convergence criterion, mainly the Hellinger divergence $H$.

The principle advantage of our approach is the employing of distribution mixtures which might well comply with the structure of real medium. It was found that the final PM space (containing 1000 hysterons) is distributed along the mixture of two Guyer distributions and phenomenological hysteretic parameters extracted from the PM space model are presented. Detailed analysis of data coming from six different porcine skin hysteresis behavior shows that the PM space identification can be considered as a new tool for estimating multiscale parameters containing rather exact information about the aging viscoelastic properties of the skin under testing.

[1] J. Lubliner, J.L. Sackman, J. Mech. Phys. Solids 14 (1966) 25–32

[2] D. Remache, et al, submitted to The Journal of Biomechanics.