Number of points: The rheological curves are discretized into a set of points. Using more points results in a better representation of the curves. The default number of points is 100, which is acceptable for most cases. To change the number of points, click Modify the number of points in the Numerical Parameters menu.

  Modify the number of points

Logarithmic or linear scale: By default, the scale for the curves will be log x, log y. To change to an x,y scale, click Switch to linear distr. of points (steady curves) or Switch to linear distr. of points (transient curves) in the Numerical Parameters menu. The first option applies to steady curves (for example, viscosity vs. shear rate) and the second applies to transient curves (for example, extensional viscosity vs. time).

  Switch to linear distr. of points (steady curves)

  Switch to linear distr. of points (transient curves)

Range of shear rates: If you want to compare rheological curves obtained for a steady shear flow, you will need to specify the minimum and maximum values of shear rate for the curves so that they will all be consistent. To set these values, click Modify the range of shear rates in the Numerical Parameters menu.

  Modify the range of shear rates

Range of extensional strain rates: If you want to compare rheological curves obtained for a steady extensional flow, you will need to specify the minimum and maximum values of extensional strain rate for the curves so that they will all be consistent. To set these values, click Modify the range of exten. strain rates in the Numerical Parameters menu.

  Modify the range of exten. strain rates

Range of times: If you want to compare rheological curves obtained for a transient flow, you will need to specify the minimum and maximum values of time for the curves so that they will all be consistent. To set these values, click Modify the range of times in the Numerical Parameters menu.

  Modify the range of times

Range of angular frequencies: If you want to compare rheological curves obtained for an oscillatory shear flow, you will need to specify the minimum and maximum angular frequencies for the curves so that they will all be consistent. To set these values, click Modify the range of angular frequencies in the Numerical Parameters menu.

  Modify the range of angular frequencies

Time variation of the shear rate: For a transient shear flow, you will need to specify the time variation of the shear rate. First, choose Modify transient shear flow in the Numerical Parameters menu.

  Modify transient shear flow

The shear rate is defined as a piecewise-constant curve. You can specify the number of segments (Modify the number of intervals), and then specify the range of times and the shear rate for each interval (Modify the times and Modify the shear rates).

When you request a curve of the transient shear viscosity, Ansys Polymat actually computes the shear stress. When the shear rate is constant, the shear viscosity can be obtained by dividing the shear stress by the shear rate; when the shear rate is not constant, this calculation is not always valid. Most of the time, the transient shear viscosity corresponds to a start-up experiment, where the shear rate is equal to 0 up to time t, and then it becomes a nonzero constant value (K). In such cases, the shear rate should be set to the constant K. Ansys Polymat will obtain the current shear viscosity by dividing the current shear stress by the current shear rate. For more complex cases, you will need to set the reference shear rate appropriately so that the shear viscosity can be correctly obtained by dividing the shear stress by the shear rate.

Time variation of the extensional strain rate: For a transient extensional flow, you will need to specify the time variation of the extensional strain rate. First, choose Modify transient extensional flow in the Numerical Parameters menu.

  Modify transient extensional flow

The extensional strain rate is defined as a piecewise-constant curve. You can specify the number of segments (Modify the number of intervals), and then specify the range of times and the extensional strain rate for each interval (Modify the times and Modify the extensional strain rates).

When you request a curve of the transient extensional viscosity, Ansys Polymat actually computes the extensional stress. When the extensional strain rate is constant, the extensional viscosity can be obtained by dividing the extensional stress by the extensional strain rate; when the extensional strain rate is not constant, this calculation is not always valid. Most of the time, the transient extensional viscosity corresponds to a start-up experiment, where the extensional strain rate is equal to 0 up to time t, and then it becomes a nonzero constant value (K). Ansys Polymat will obtain the extensional viscosity by dividing the current extensional stress by the current extensional strain rate.

To define the time evolution of the strain rate applied on the fiber you can use either of the following methods.

Reference temperature: For a non-isothermal flow, you will need to provide at least one reference temperature. For each temperature, the rheological curves will be calculated for comparison with experimental data. To add, modify, or remove a reference temperature, use the List of temperatures menu, which is opened by clicking Modify the temperature

  Modify the temperature