Rayleigh Damping for Dynamic Relaxation

M \frac{d^{2} u}{{dt}^{2}} + C \frac{du}{dt} + K (u) u = f

C = αM + β [\begin{matrix} K_{11} (u) & 0 & \dots \\ 0 & K_{22} (u) & \dots \\ ⋮ & ⋮ & ⋱ \end{matrix})]

\{M, C) \in ℕ \times ℕ\}

\{u, f) \in ℕ \times 1\}

M	Concentrated (diagonal) mass matrix
C	Diagonal damping matrix
K	Stiffness matrix
f	Vector of external forces
u	Discretized displacement vector

Do you have any questions?