Linear and nonlinear fractional Voigt models
  We consider fractional generalizations of the ordinary differential equation that governs the creep phenomenon. Precisely, two Caputo fractional Voigt models are considered: a rheological linear model and a nonlinear one. In the linear case, an explicit Volterra representation of the solution is found, involving the generalized Mittag-Leffler function in the kernel. For the nonlinear fractional Voigt model, an existence result is obtained through a fixed point theorem. A nonlinear example, illustrating the obtained existence result, is given. 
Amar Chidouh, Assia Guezane-Lakoud, Rachid Bebbouchi, Amor Bouaricha,   Delfim F. M. Torres
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