Page 155 - Thomson, William Tyrrell-Theory of Vibration with Applications-Taylor _ Francis (2010)
P. 155
142 Systems with Two or More Degrees of Freedom Chap. 5
6.90 9.06
7.07 8 92
7 8 10
Figure 5.3-7. Uncoupled frequencies relative to coupled frequencies.
rotation. This suggests that we could have made a rough approximation for these modes as
two 1-DOF systems.
total vertical stiffness 5000 7.07 rad/s
translational mass 100
rotational stiffness 127,250
rotational moment of inertia 1600 = 8.92 rad/s
Note that these uneoupled values are inside of the coupled natural frequencies by small
amounts, as shown in Fig. 5.3-7.
One other observation is worth mentioning. For the simplified model used, the wheels
and tires had been omitted. This justification is assigned in Prob. 5-27 with data as to
weights of wheels and stiffness of tires.
Figure 5.3-8 shows an inverted laboratory model of the automobile.
Figure 5.3-8. Two-DOF model of an automobile. The auto body is
represented by the meter stiek with adjustable weights. The model is
inverted with the springs and ground above the body. Shakers can be
excited individually to simulate the ground. (Courtesy of UCSB Mechani
cal Engineering Undergraduate Laboratory.)
