In their paper 1, the authors investigate the vibration damping of a beam by means of a permanent magnet whose axis is perpendicular to the vibration direction. They acknowledge the fact that only the radial magnetic field will participate in the damping, while the axial magnetic field has no effect.
They then propose an improved concept consisting of two magnets positioned on opposite sides of the beam, rather than a single magnet: “It is realized that when two similar magnetic poles are placed close to each other, the magnetic flux of each magnet is compressed in the poling direction, causing the intensity in the radial direction to be enhanced as shown in Fig. 2” (p. 295). This calls for the following comments:
Magnetic fields add vectorially. It is then misleading to say that using two opposite magnets...