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INNOVATIVE APPROACHES TO STRUCTURAL HEALTH MONITORING
3. EXPERIMENTAL STUDIES
3.1. Test Description
Validation of the results obtained through the above and additional simulation studies
requires application to experimental data. To accomplish this, a test facility was
developed to test a 10-kip nonlinear viscous damper with a 12-inch stroke and a
velocity rating of 70 ips. The system was excited through an 11-kip MTS Systems
actuator fitted with a 90 gpm servo valve to accommodate high velocities. Figure 3.1
presents a digital image of the test set-up. The damper/actuator connection was
fabricated with linear bearings to only allow motion along the axis of the damper,
thereby avoiding out-of-plane bending.
Figure 3.1 Digital photo of test set-up (damper is approx. 4 feet long)
3.2. Sample Measurements
Figure 3.2 depicts the measured system response of the damper excited by a 4-inch
peak broadband signal. The highly irregular system response captured in the
velocity/restoring force phase plot in the transition range reveals dead-space
fluid/orifice dynamics internal to the damper.
It is important to note that the damper component tested experimentally incorporates a
relatively minor contribution of the stiffness parameter to the measured response. In
contrast, the Duffing oscillator defined in the analytical studies included a significant
stiffness to the restoring force. The simulations were conducted with a sdof
descriptive model, interpreted as a model containing an elastic member and a damper