Auto Strain Adjustment Guidelines
Introduction
The Auto strain adjustment changes the strain amplitude during oscillation tests automatically in order to maintain the measured torque within a given torque window.
When should Axial Force be used?
Auto Strain control should be used when the stiffness (modulus) of a material changes during a test procedure as a result of temperature or structural changes. Auto Strain permits to measure material properties over a wide modulus range without changing the test geometry and still operating at a torque within the best performance range.
Adjusting Strain During Oscillation Tests
Auto Strain is activated/deactivated by inserting a conditioning step at the desired position in a procedure. Insert a Conditioning > Options step and select Auto strain adjustment:
- Mode: Select either Enabled or Disabled, depending whether you desire to enable or disable the function. Enabling strain adjustment maintains the strain within a strain window as defined by the parameters. Disabling switches off the strain adjustment and the strain defined in the test setup is maintained.
- Strain adjust: The strain adjust parameter is the size of the step in strain in % relative to the applied strain.
- Minimum strain, Maximum strain: Define the window within which the strain is allowed to change in order to retain the torque within the set limits.
- Minimum torque, Maximum torque: Define the desired torque window. Typically the torque window is kept narrow whereas the strain limits are given by test constraints such as resolution for the minimum strain and limit of the linear viscoelastic range for the maximum strain. If both strain and torque reach a limit, the strain will override the torque.
