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Publication 13-CNA-018

The State of Fractional Hereditary Materials (FHM)

Luca Deseri
Center for Nonlinear Analysis
Department of Mathematical Sciences
Carnegie Mellon University, Pittsburgh, PA
deseri@andrew.cmu.edu

Massimiliano Zingales
Department of Civil, Environmental and Aerospace Engineering
Viale delle Scienze - Build. 8 - 90128 Palermo, Italy
(BM)$^2$-Lab, Mediterranean Center of Human Health and Advanced Biotechnologies
Viale delle Scienze - Build. 18 - 90128 Palermo, Italy
massimiliano.zingales@unipa.it

Pietro Pollaci
Department of Civil, Environmental and Mechanical Engineering
Via Mesiano 77, 38123 Trento, Italy
Department of Civil and Environmental Engineering, Carnegie Mellon University, Pittsburgh, PA
pietro.pollaci@unitn.it

Abstract: The widespread interest on the hereditary behavior of biological and bioinspired materials motivates deeper studies on their macroscopic "minimal" state. The resulting integral equations for the detected relaxation and creep power-laws, of exponent $\beta$, are characterized by fractional operators. Here strains in $SBV_{loc}$ are considered to account for time-like jumps. Consistently, starting from stresses in $L_{loc}^{r}$, $r\in [1,\beta^{-1}], \, \, \beta\in(0,1)$ we reconstruct the corresponding strain by extending a result in [38]. The "minimal" state is explored by showing that different histories delivering the same response are such that the fractional derivative of their difference is zero for all times. This equation is solved through a one-parameter family of strains whose related stresses converge to the response characterizing the original problem. This provides an approximation formula for the state variable, namely the residual stress associated to the difference of the histories above. Very little is known about the microstructural origins of the detected power-laws. Recent rheological models, based on a top-plate adhering and moving on functionally graded microstructures, allow for showing that the resultant of the underlying "microstresses" matches the action recorded at the top-plate of such models, yielding a relationship between the macroscopic state and the "microstresses".

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