However, all too often rheometer users give up with creep tests because thefind it difficult to choose the right stress to apply to get meaningful results for a particular sample.
An easy way of identifying a suitable value is to first run a quick oscillation stress sweep. A typical setup would be:
- Method: Oscillatory Stress Sweep
- Frequency: 1Hz (6.28 rad/s)
- Logarithmic data collection.
Plot: Elastic modulus vs stress, log-log scaling.
Below is a typical result for a viscoelastic liquid, clearly showing the linear viscoelastic behaviour plateau up to a yield point, whereupon the elastic modulus drops rapidly.
Now, if you identify a stress that is well below this yield point, and ideally just above the noisy data, you will have a stress that you can comfortably apply in a subsequent creep test, without fear of clobbering your sample.
