Fig. 10. Renormalized damping force Fd versus velocity v ¼ _y , F d ¼ av bv3: for the examined case (see Eqs. (6) and (7)) – ‘1’
(c1 = 250 N s/m, c2 = 25Ns3/m3) and for opposite signs of the damping coefficients – ‘2’ (c1 = 250 N s/m, c2 = 25 N s3/m3).