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Mechanical
shocks can be generated by a number of methods.
For shocks of relatively low acceleration (40 g or
less, but depends greatly on the specific
capabilities of the equipment), an electrodynamic
shaker can be used. For higher accelerations (up
to 30,000 g) free-fall or accelerated drop tables
are employed. Other options include long stroke
pneumatic or hydraulic systems and pyroshock
systems to simulate the pulses from explosive
events.
The basic
variables associated with specifying this type of
testing are relatively straightforward:
-
Pulse
shape
-
Acceleration expressed in g's (1 g is the force
of gravity)
-
Pulse
width expressed in milliseconds (ms)
-
Number of
pulses
-
Time
between pulses (seconds; minimum determined by
vibration equipment)
-
Axis to
be tested
Additional
variables include those associated with the tails
and the tolerances of the waveform. The tail
characteristics are typically specified as a
percentage of the peak value of the wave with 40%
being common. This will determine both the
magnitude and resulting duration of the tails.
Tolerances and abort parameters are shown in the
graphs above as yellow and red curves
respectively. They are specified as percentages
of the peak value with 40% and 60% being common.
For most testing, the default values suffice.
Test
Specification Template (Classic Mechanical Shock
Vibration)
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