Environmental Engineering Reference
In-Depth Information
No. 2 terminal
National Instruments
BNC-2110
No. 2 power supplies
BOP 50-4 M
from Kepco Inc.
Digital multimeter
National Instruments
PXI-4065
(b)
(c)
(d)
(a)
Embedded controller
National Instruments
PXI-8196 RT
No. 2 data acquisition
National Instruments
PXI-6259
Fig. 13.6
Electronic equipment for acquisition and semi-active control
13.4 Magnetorheological Dampers
The devices adopted for the tests were two full-scale prototype SA MR dampers
(Fig.
13.7
) designed and manufactured by the German company Maurer Söhne.
The overall dimensions of each device are 675 mm (length) 9 100 mm (external
diameter), with a mass of about 16 kg. A maximum force of about 30 kN can be
developed along the longitudinal axis, whereas the presence of special spherical
pin joints at both ends prevents the rise of bending, shear, and torsional moment in
the piston rod. The dampers have a stroke of ±25 mm. The external diameters of
the piston head and of the piston rod are 100 and 64 mm, respectively. A magnetic
circuit composed of coils, in series with a global resistance of 3.34 X, can generate
the magnetic field in the device. The current in the circuit can be provided in the
range 074A.
The MR dampers were first experimentally tested by using a self-balanced
testing apparatus (Fig.
13.8
). Some general information is provided herein. Further
details can be found in [
14
].
Figure
13.9
shows the results of four ''passive'' (constant value of current) tests
done imposing the same harmonic displacement at the mobile end of the device
(frequency 1.5 Hz, amplitude 20 mm) with four different current levels (0.0, 0.9,
1.8, and 2.7 A).
The force-displacement and force-velocity cycles clearly show how the dam-
per's mechanical behavior strongly depends on the magnetic field inside the device
and, in turn, on the current intensity inside the coils. In particular, the maximum
