Tutorial Rolie-Poly

Non-Linear flow prediction

  1. Start RepTate and create a new NLVE Application logo:

    New application
  2. Drag and drop shear (.shear) or uniaxial extension (.uext) data files, e.g. all the .uext files from the folder data/DOW/Non-Linear_Rheology/Start-up_extension/.

    The first column of the file should contain the time and the second column the stress (shear, or tensile, stress growth function).

    Load data
  3. Select the “RoliePoly” theory th_select and press einstein to create it.

    New theory

    At this point, you need to setup the relaxation times, \(\tau_i\), and weights, \(g_i\), for each mode \(i\). You can:

    • Input them manually by clicking:

      Edit modes

      then select the number of modes, enter the values and click “OK”, then “Minimize Error” fit.

    • Alternatively, it is possible to copy the values from a file or spreadsheet from and external program and paste the values into the “Edit Modes” table. Note that you should adjust the number of modes before pasting the values.

    • Obtain the Maxwell modes from a different RepTate application (LVE, TTS, G(t)). In this tutorial we will import Maxwell modes from a LVE application.

  4. Create a new LVE Application logoLVE and open the linear viscoelastic data file corresponding to the same sample at the same temperature. We use the file data/DOW/Linear_Rheology_TTS/DOWLDPEL150R_160C.tts. Then, we create a new Maxwell theory maxwell and “Minimize Error” fit:

    LVE for NLVE
  5. Return to the NLVE application and now click import_modes. We want to import the 6 Maxwell modes of the “LVE2” app. Select from which theory you want to import the modes get_modes and click “OK”. Then click “Minimize Error” fit to find the best values for the tauR parameters:

    Theory prediction
  6. Click the eye button to show (or hide) the linear viscoelastic envelope prediction:

    Show LVE
  7. The number of stretching modes is given by nstretch. \(N_\text{stretch}=0\) means that the non-stretching version of the Rolie-Poly model will be used for all modes. See Rolie-Poly equation for more details. So far, the calculations were done using “infinitely stretching chains” no_fene. Click that button to use finite extensibility fene. The maximum extensibility parameter lmax is now present in the parameter table. You can change its value and click “calculate” calculate to update the theory predictions:

    With fene