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A D V A N C E D M A T E R I A L S & P R O C E S S E S | A P R I L 2 0 1 6
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natural frequency of the specimen,
as installed in the test machine. A PID
controller provides a feedback loop
based on mean force (or stress), fre-
quency, and displacement, and tunes
the force exerted by the resonance
drive to the natural frequency of the
testing system.
Froma cost-of-ownership perspec-
tive, magnetic resonance systems can
be installed in most labs without infra-
structure modifications and consume
only 2% of the power of a comparable
servohydraulic test system. Operation
of the Vibrophore is straightforward, re-
quiring minimal training. Furthermore,
with few parts subject to mechanical
wear and tear, Vibrophores are reliable
and low-maintenance machines. As
an example of these machines, Zwick
recently introduced a new generation
of Vibrophore systems available in
50-1000 kN capacities and offering a
frequency range of 30-300 Hz. These
products are the result of decades of
HCF testing experience with the com-
pany’s Amsler line of high-frequency
pulsators.
The new Vibrophores use an elec-
tric drive for controlled static loading
similar to a static materials testing
machine, and a magnetic resonance
drive for controlled dynamic loading.
This design enables both dynamic
HCF evaluations and pure static test-
ing. With up to eight frequency steps
achievable through the activation of
top-mounted weights, tests can sim-
ulate changes such as partial loss
of torque due to thermal effects, or
provide additional system damping
if component heating during the test
is a problem. In addition to testing
by force or strain control, true cross-
head position is available as a control
parameter.
Strain measurement is only rel-
evant when Vibrophore systems are
used for static tests. Operating in static
mode, Zwick’s systems are often con-
figured with makroXtens extensome-
ters. The geometry of the knife edges
in these extensometers enables testing
of both round and flat specimens, mak-
ing them suitable for static testing of
critical components such as aerospace
fasteners. ~AM&P
For more information: Markus Semrau
is product manager, Vibrophore sys-
tems, Zwick/Roell, August-Nagel-Str. 11,
D-89079 Ulm, Germany, +49.7305.100,
, .