Start from target frequencies and target damping ratios, or enter alpha and beta directly.
The plot separates the mass-proportional and stiffness-proportional contributions so you can see where the total curve comes from.
Input
Plot range
Damping ratio curve
Rayleigh damping uses C = alphaM * M + betaK * K and
zeta(w) = alphaM / (2w) + betaK * w / 2.
The dashed curve is the mass term. The dotted curve is the stiffness term.