Generalized thermoviscoelastic novel model with different fractional derivatives and multi-phase-lags

In the current investigation, we introduce a generalized modified model of thermoviscoelasticity with different fractional orders. Based on the Kelvin–Voigt model and
generalized thermoelasticity theory with multi-phase-lags, the governing system equations
are derived. In limited cases, the proposed model is reduced to several previous models in
the presence and absence of fractional derivatives. The model is then adopted to investigate
a problem of an isotropic spherical cavity, the inner surface of which is exposed to a timedependent varying heat and constrained. The system of governing differential equations has
been solved analytically by applying the technique of Laplace transform. To clarify the effects
of the fractional-order and viscoelastic parameters, we depicted our numerical calculations
in tables and figures. Finally, the results obtained are discussed in detail and also confirmed
with those in the previous literature.