“…Point spall [53,56,57,59,61,62] 2. Circular and elliptical spall [60,64,66] 3. Line (rectangular) spall [54,55,58,63,65,[67][68][69] 303 Building on the 2-DOF model of Fukata et al [40], Feng et al [53] presented a 4-DOF model corre- 304 sponding to the two translational degrees of freedom, in the radial plane, each for the two lumped masses: 305 the rotor and pedestal masses.…”