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UniVert User Manual
5
Test Phases: The Smallest Unit of Testing
The test phase is the smallest unit of the test specification. There are five phases within a cycle.
Each phase serves a specific purpose:
Preloading - Preloads are applied to bring a test to a well-
defined starting point. Because the dimensions of a
specimen may change as a result of a loading cycle
(stretching of fibers, viscoelastic effects, plastic
deformation, or localized material failure at the attachment
points), the preload adjustment compensates for any of
these changes in specimen geometry.
Stretching - During the stretch phase, a deformation is
applied to the specimen. The deformation can be specified
either in terms of force applied or displacement achieved.
Note that in this context, the stretch phase refers to either
stretching (for a tension test), or compression (for a
compressive test).
Holding - The deformation can be held for a given
duration. The duration for which it is held is dependent on the nature of the testing.
Recovering - The recovery phase is the time during which the force being applied to the
specimen is removed. The duration of the recovery time is configurable and dependent on the
nature of the testing.
Resting - Finally, the rest phase is the time between the end of one cycle and the beginning of
the next. Some tests may specify a short recover time or no recover time, while others may
specify a longer time. The duration is configurable and dependent on the nature of the testing.
Control Modes
There are two control modes which define the basic approach to a given test: displacement
control and force control:
Under displacement control , the displacement of the specimen is predefined. The
UniVert stretches or compresses the specimen until the predefined displacement is
achieved (specified in mm or %). The force required to achieve the displacement is an
output of the test.
Under force control , the force applied to the specimen is predefined. The UniVert
stretches or compresses the specimen until the predefined force is achieved (specified in
newtons [N]). The displacement required to achieve the force is an output of the test.