MTS Fundamental Video Extensometer User Manual
Page 22
Fundamental Video Extensometer
22
Starting the Video Extensometer
3. Numbers of markers: According to the version, it is possible to choose
different types of tests (see
“Principle of Markers Tracking”
•
A 2-markers test allows you to track the distance between the 2
markers onto a sample, and to calculate the longitudinal strain.
•
A 4-markers test is the same procedure of that for the 2 markers, with
the addition of 2 horizontal markers for calculating the transverse
strain.
•
A 7-markers testis a special test for the determination of volumetric
strain.
•
A sand-glass test allows you to prepare a tensile test on a cylindrical
sample with a follow-up of the strain starting from the minimum
diameter of the sample.
•
A N-markers test allows you to record the coordinates of the barycenter
of each markers in a file. You must specify the number of markers
present on the specimen, not to exceed 200 markers. By default the
software records the first image with the classification of the markers
in order to link each marker with the data file. You can change the
default name of the file image by checking the Start box.
4. The strains are:
•
The true strain which is calculated as Ln(L/L0).
•
The nominal strain which is calculated as (L – L0)/L0.
•
The relative strain which is calculated as L- L0.
•
The length corresponding to the new length.
Relative strain and length are available only after a calibration procedure.
5. Average provides averaging the image number before sending it to the
testing machine. To activate this choice, check the Activating box and
indicate the number of measures to be taken into account.
6. The channel of communication is the method the testing machine uses to
receive the strain(s). If the choice of the channel is the RS232 or the 10
Volts, the values can be entered by clicking Parameters.
OR