Laserextensometer - Multi Point System

Multi-Point Scanning

The 'Multi-Point-System' allows the observation of up to 63 markers during an experiment.
The number and position of the stripes is user defined. So the experiments allows a flexible examination of the deformation distribution. The areas of interest can be freely chosen among the applied stripes after the experiments are finished. The preparation of an experiment giving locally resolved strain information is very simple. All features supported for the Two-Point System are included in the Multi-Point System.

The sample was loaded in a standard tensile test. The software recorded the positions of all stripes on the sample, allowing the calculation of strain between arbitrary chosen stripes.

Three strain time diagrams are shown below. After the experiment, three zones were selected (zone 1-44, zone 1-22, zone 11-22). Furthermore, the three diagrams have been combined into a single diagram:

(Zone 1-44)

(Zone 1-44, Zone 1-22, Zone 11-22)

(Zone 1-22)

(Zone 11-22)

In the elastic range, all zones show nearly identical behaviour. However, leaving the elastic range after about one quarter of the experiments duration, the three zones clearly show significantly different behaviour.

The figure on the left hand side shows the strain distribution along the sample. The strain was determined between marker 1 and 2, 2 and 3, ..., 43 and 44. These zones are shown on the horizontal axis, strain is shown on the vertical axis and time is shown as the third dimension going to the background.

Our laser extensometers for locally resolved strain analysis allow a very flexible examination of samples with inhomogenous strain distribution. Recording locally resolved strain is straight forward by simply applying a number of stripes on the samples. The data acquisition software stores the position of all stripes during the experiment.

Using the data evaluation software, strain can be analysed between arbitrary stripes chosen by the user. Multiple data curves are available in 2D strain-time- or stress-strain-diagrams. Strain distributions are available as 3D strain-time- or stress-strain-diagrams. The area of interest can be chosen after the experiment. Choosing the wrong area for observation during the measurement is not an issue, because any area can be selected using the data evaluation software.

With a distance between the single stripes of down to 0.5 mm and the laser extensometer type P-50, very fine details can be measured (e.g. metals, components or any samples with low strain). With the scanners for larger scanning range (W-80 or W-160), the strain distributions of polymers, elastomers and similar materials can easily be measured.

The maximum or minimum local strain is available as a set value for the tensile testor. The simple application of just some more stripes for a locally resolved strain analysis makes our laser extensometers a perfect choice for analysing inhomogeneous materials.