TA Instruments RSA-G2, Manual

Page: 18 / 127

Strain Sweep
In this test, the frequency and temperature are held constant and the strain is varied. Strain Sweep tests are used to identify the linear viscoelastic region, LVR. Testing within the LVR
provides powerful structure-property relationships as a material's molecular arrangements are never far from equilibrium and the response is a reflection of internal dynamic processes.
The right figure shows a strain sweep on a filled elastomer sample tested at 10 Hz in dual cantilever bending geometry. At low strains, within the LVR, the modulus is independent of the
strain amplitude. At about 0.1 % strain the modulus begins to decrease in magnitude showing the end of the LVR. Outside the LVR the output stress response to the input strain is no
longer sinusoidal. Non-linear effects show up as higher odd harmonics which the RSA-G2 is able to collect. The figure shows the intensity ratio of the third to first harmonics at each strain
value. Strain sweep tests can be used for a variety of additional reasons such as understanding the Mullins Effect in a rubber or comparing the resiliency of materials.
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Strain Sweep on Elastomer
108
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Linear Region Non-Linear Region
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Temperature:
25
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Frequency: 10Hz
Dual Cantilever
106
0.01 0.1 1.0
Testing Modes and Applications
17
Strain
(%)
0.25
0.2
0.15
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