Toe-in Compensate in MCalibration
Most experimental data files that I receive do not start with time, strain, and stress all equal to zero. To fix this I often use and recommend the toe-in compensate feature that is part of the data-tab in MCalibration. To activate this feature you simply need to right-click in the data-tab table, and then select “Toe-in Compensate the 1st Point” (see the short video below). In this tutorial I will explain exactly what MCalibration does when you select this feature.
Start by reading in the experimental data into the data tab. In this example the stress and strain do not start from zero. It is usually OK to shift the data horizontally, but not vertically (since the strain is often not accurate, but he force is).
Draw a straight line between points 2 and 3, extend the line back to to where it crosses the stress axis (Point A in the figure).
Shift all data points horizontally (with the same amount) so that Point A is at the origin.
Remove the original points 1 and 2, and add the new Point A as the first data point. This first data point will now have a zero time, strain, and stress value. Note that this toe-in compensation algorithm removes one data point from the data set. In this example it would be beneficial to run the toe-in compensate algorithm one more time in order to improve the data further.