Bs. Liebst et Pj. Torvik, ASYMPTOTIC APPROXIMATIONS FOR SYSTEMS INCORPORATING FRACTIONAL DERIVATIVE DAMPING, Journal of dynamic systems, measurement, and control, 118(3), 1996, pp. 572-579
Viscoelastic constitutive relationships incorporating fractional deriv
atives have been previously shown to be extremely useful in describing
the frequency dependent behavior of common damping materials. However
, the implementation of such models in the analysis of damped mechanic
al systems is some,what complicated by the fact that polynomial equati
ons with noninteger order exponents must be solved. This paper develop
s accurate approximations from which the damping factor and damped nat
ural frequency of such systems may be obtained by evaluating relativel
y simple algebraic expressions.