Model of Internal Friction Damping in Solids
  A model for harmonic oscillator damping due to the internal friction of solids has been developed, based on considerations of a long period pendulum. The assumption of a complex elastic modulus to describe stress-strain hysteresis in the support structure of the pendulum yields an expression for the figure of merit Q that agrees with many experiments involving material damping. As such, the approximations of this linear model stand in contrast with common theory. 
Randall D. Peters