Dynamically loaded bolts and fasteners play
a vital role in the aerospace and automobile
industries, and even in automotive racing
applications. Fasteners subjected to alternating
loads are commonly found in combustion
engines, aircraft turbines, landing gears
and in the structural airframe components.
The desired design goal of these fasteners is
to provide adequate joint strength, low
weight and fatigue resistance. Therefore,
dynamic testing of the fasteners and bolted
structures is required to ensure proper materials
properties and manufactured quality.
Fatigue testing in research and development
applications is necessary to understand the
behavior of fasteners which are constructed
with new materials or manufacturing processes.
The fasteners are tested at various loads
to determine a “S-N” curve or endurance limit
generally up to several million load cycles.
The Zwick Vibrophore provides a cost-effective
method for performing these dynamic tests.
Its electromagnetic resonant operation
results in high-testing frequencies with low
energy and maintenance requirements. The
high testing frequencies shorten overall
testing durations and therefore allow important
quality or development projects to be
supported in an efficient manner. For example,
the test duration for 2 million load cycles
and a testing frequency of 120 Hz is less
than 5 hours. Intervention by the user is only
necessary when changing specimens, which
can be done simply and safely. The set-up,
control and monitoring of the test procedure
is conducted by the testing software
testXper.

After the operator loads the sample in the
machine, the desired testing parameters are
input into testXpert®, including the static
preload and loading rate, alternating load (or
displacement), desired number of cycles,
end-test criteria. After the test is started, the
test parameters are displayed and updated
on an online graph within testXpert®. The
software provides various possibilities for
post-test data evaluation, e.g., the compilation
of an individual testing procedure, or
export into Excel or Word.

Naturally, the Vibrophore is also suited for
use in other dynamic tests to determine the
fatigue endurance and fatigue strength of
materials and even components such as
connecting rods, camshafts, crankshafts,
chains, and other components subject to
repetitive loading. The Vibrophore may also
be used for fracture toughness (KIc) testing.
The nominal force of a Vibrophore varies
between 5 and 500 kN, depending on the
model, and test frequencies generally range
between 80 and 300 Hz – generally much
faster than for servo-hydraulic systems at
only 5% of the energy requirement. Due to
the fast testing speeds, low energy costs
and low maintenance, the Vibrophore has a
rapid return on its original capital investment.
Zwick offers a full line of accessories for the
Vibrophore including grips, bend fixtures, fixturing
to allow torsional fatigue, strain and
extensometry, and environmental chambers.
Consider a Zwick Vibrophore to meet the
requirements of your next dynamic test program!