Example 16 - Look at different models of the disk-shaft interface

In this example, we use the rotor seen in Example 5.8.3 from [Friswell, 2010] and we make the same comparison looking at 4 different ways of modelling the shaft-disk interface:

Consider a hollow shaft carrying a central disk and mounted on
short, rigid bearings at each end. The shaft is 1.2 m long and it has an outside
diameter of 80 mm and an inside diameter of 30 mm. The central disk has a diameter
of 400 mm and a thickness of 80 mm. The shaft and disk have a modulus
of elasticity of 200GN/m2 and a density of 7,800kg/m3. Poisson’s ratio is 0.27.
This is the same as the rotor used in Example 5.8.1. The rotor, consisting of
the shaft and central disk, spins at 3,000 rev/min. Investigate the effect of the
shaft-disk interface models on the natural frequencies of the machine.
import ross as rs
Q_ = rs.Q_
steel = rs.Material("steel", rho=7800, E=200e9, Poisson=0.27)
L = 0.2
idl = 0.03
odl = 0.08
N = 6
shaft = [rs.ShaftElement(L=L, idl=idl, odl=odl, material=steel) for i in range(N)]
bearings = [
    rs.BearingElement(n=0, kxx=1e20, cxx=0),
    rs.BearingElement(n=len(shaft), kxx=1e20, cxx=0),
disks = [
    rs.DiskElement.from_geometry(n=3, material=steel, width=0.08, o_d=0.4, i_d=0.08)

rotor1 = rs.Rotor(shaft_elements=shaft, disk_elements=disks, bearing_elements=bearings)