Vibration Visualization

The EDM Vibration Visualization feature is available in all modules of EDM software (VCS, DSA and Modal). This option provides fast and efficient structural model generation and full 3D visualization of the online vibration pattern on the structure under test.

Users can select the Vibration Visualization option from the View drop-down menu as shown in the following figure.

There are three tabs to cover geometry model editing, input channel DOF mapping, and operational deformation shape animation. The first tab is the Editor window, which is designed to help users create geometric models to visualize the operational deflection shapes of the test structure (including the addition/deletion of points, lines, surfaces, structure library of line, panel, cube, sphere, cylinder, and circle). Users can model any structure with the geometry editor.

The second tab on the right is Channels, which has two windows: channel table and geometry window. This tab allows the user to assign the corresponding measurement point ID and its DOF information to each enabled input channel. With DOFs defined, each channel will be mapped to a DOF on the geometry model.

The third tab is Animation, which displays the deformation animation of the operational deflection shapes of the structure under test. Block and RMS data from the input channels can be used for the vibration visualization of the operational deflection shapes. This window provides a visualization of the deformation of the test structure while the test is running. Users can select from  several animation types, such as ‘point and arrow’, ‘wireframe’, or ‘surface contour’. Furthermore, the animation equation editor and animation with interpolation options are also available for the operational deflection shapes animation.

A vibration control test is carried out to demonstrate the vibration visualization feature. A plexiglass plate is suspended using bungee cords to produce a free-free boundary condition. Random excitation from a modal shaker is used to excite the rectangular plate. The acceleration response from the impedance head is used to control the vibration test. The response of the plate is monitored using 12 uni-axial accelerometers.

A test profile of 20-2000 Hz with an RMS level of 1 g’s is used for the vibration control test. A pre-test is run to compute the transfer function for closed-loop control. The run schedule is set appropriately to slowly ramp-up the test level.

The following images show the operational deflection shapes of the rectangular plate when the block data of the input channels is used for display. The block data is useful for a more instantaneous display of vibration visualization of the structure under test. The excitation point is changed to obtain different operational deflection shapes of the plexiglass plate.

The RMS data of the input channels can also be used for the vibration visualization of the test unit. To enable the RMS option, the user can enable RMS signals of the input channels in the Statistics Time History tab available under Measured Signals Setup.

The RMS option displays the RMS data of each time block and is useful to observe which measurement DOFs have the maximum deformation. Different operational deflection shapes are obtained when the excitation point is changed.