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Modal Impact Testing: User Defined Impact Sequence

Siemens Experimenter Siemens Experimenter
Siemens Experimenter


Doing an impact test and want to define a custom impact sequence? This is possible with Simcenter Testlab (previously called LMS Test.Lab) version 16 and later.


When performing an impact test, it is typically required to hit the structure multiple times or in several locations.


With the User Defined Impact Sequence, the increment button can now increment the accelerometer Point IDs in any custom fashion, no longer just numerically.


Imaging doing an impact on a simple plate.

  • There are 15 points defined on the plate (Figure 1).
  • The test engineer has 3 uniaxial accelerometers.
  • It is desired to rove all 3 accelerometers 5 times (5 runs).
  • The test engineer wants to move the accelerometers in groups of three down the structure. He wants the accelerometers at the red locations for run 1, the yellow locations for run 2, the green locations for run 3, etc.

1.pngFigure 1: The geometry of the plate. The plate is defined with 15 points.

The desired impact sequence is as follows:


2.pngFigure 2: The desired impact sequence.

Essentially, the desired sequence is to hit at plate:1 each run and then rove the accelerometers down the plate.


By default, Test.Lab increments numerically. After each run, each accelerometer location is incremented numerically by 1. 


3.pngFigure 3: The default incremented impact sequence.

To create the custom impact sequence, turn on the desired number of channels in channel setup. In this instance, one hammer and three uniaxial accelerometers are used.


4.pngFigure 4: Ensure the channel setup has the desired number of channels turned on.

In the measure workbook, click “All Settings”.


5.pngFigure 5: Open “All Settings” in the Measure workbook.

In the “All Settings” pop-up window, select “User Defined Increment Sequence” and then close the window.  


6.pngFigure 6: The “All Settings” window has many custom options for running the impact test.

Back on the “Measure” screen, select “Edit Points…”.


7.pngFigure 7: Open “Edit Points…” from the Measure workbook.

This will open the “Edit points…” pop-up window.


In this case, 5 runs are desired. It is desired to hit the hammer at plate:1 for every run. The response locations and direction are then input for all the following runs.


8.pngFigure 8: The “Edit Points…” window is where the user creates the custom impact sequence.

Back on the measure screen, when the increment button is pushed the proper impact sequence is used (see below video).  



(view in My Videos)



Compare this with the default increment sequence (see below video).


(view in My Videos)


Enjoy the flexibility the User Defined Increment table offers.


Questions? Email or contact Siemens PLM GTAC support


Modal Data Acquisition Links:

Modal Analysis and Operational Deflections Shapes Links:


I think this feature would work for me, but I have a simpler request/need.  Instead of a custom sequence, I just want to increment my measurement point ids by 20 instead of 1.  Currently between runs, I have to hit the increment button twenty times because there is only a increment of 1.  It is a little laggy and sometimes I mess up.


Rather than define the custom sequence, it there something simpler I could do?

Siemens Phenom Siemens Phenom
Siemens Phenom

It is possible to set the default increment to a value other than 1. Just select the "Edit Points..." button in the Measure worksheet of impact testing. There you can change the default increment from 1 to 20 as shown below.




Just in case - you can choose whether the increment affects measurement channels or your force impact hammer channel under "Settings" in the upper right corner of the Measure worksheet (you cannot increment both):




Hope that helps!