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DHR/AR Rheometer: Setting Up an Oscillation Temperature Sweep

In this topic
Overview
Suggested Use
Test Setup

Overview

In an oscillation temperature sweep, the temperature is varied in steps. The oscillation measurements are performed under isothermal conditions. A temperature equilibrium time can be set to make sure isothermal conditions are fulfilled before doing the measurements. In a temperature ramp, the frequency is typically a constant, while the temperature step test lends itself to do multiple frequencies. As such, it is possible to vary the frequency linearly, logarithmically, or in discrete steps. Strain, stress amplitude, and phase shift are recorded.

Suggested Use

The main application for the temperature sweep is the frequency temperature superposition to extend the experimental frequency range. Viscoelastic materials change from solid-like to fluid-like behavior over a frequency or time range of 10 decades and more. This frequency range is experimentally not accessible, and can only be constructed from frequency sweeps measured over a wide temperature range. The composite curve referenced to one temperature is the master curve. 

Similar to the time sweep, the Axial Force functions to compensate for volume changes due to temperature.

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Test Setup

To select an Oscillation Temperature Sweep test, see Using Experimental Procedures for detailed instructions.

When you perform an Oscillation Temperature Sweep experiment, the following parameters need to be chosen:

Environmental Control

Test Parameters

Set up the following test parameters: 

Frequency Sweep Parameters

Three types of frequency sweeps can be run. Choose the desired method from the list below. The available frequency range is dependent on your instrument type and configuration. 

If you want to edit the values already displayed in the table, place the cursor in the table at the desired point and make your editing changes. The entries will be used in order until the first 0.00 entry is encountered, which is recognized as the end of the table.

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Controlled Stress/Strain Advanced

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Data Acquisition 

There are additional data collection options that can be adjusted to control how data is obtained and what additional information is collected during the measurement. To access these options, click on the “arrow” to display these test fields. 

  1. Select the desired Split data: You can decide how data is to be split during acquisition. This option becomes available if the frequency is to be swept during the test.

  1. Save waveform (point display): Select this option to store a snapshot of the data correlation buffer used for the calculation of the oscillatory data along within the data file for future recall. Note that this waveform snapshot is a small subset of the actual data used in the calculation, and can be used to provide insight into the quality of the stress and strain signals used based on the shape of the waveforms and noise levels present.

See Also

Viewing the Point Display

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Controlled Flow

This is used to superpose a continuous flow onto the oscillation signal (parallel superposition). This option is not available for continuous oscillation in controlled stress and strain mode. Select the flow control below: 

Step Termination  

TRIOS Software allows you to define conditions in which a step is halted ahead of its normal termination conditions (Limit checking). You can use this to ensure that, for instance, the instrument does not over speed or apply excessive strains.

Rather than running a step for a certain amount of time, you may wish to run it until stable data is obtained. You can set an Equilibrium limit (such as the viscosity value becoming constant when running a single shear with time) that will stop the currently active test.


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