October 1, 2021 at 11:35 am

Erik Kostson

Ansys Employee

Hi

See the comments and the video, where they actually use a guided wave in the rod (force excitation always) in 3D.

If you do this in 2D which is fine for the symmetric type of modes in the rod, you would need to have the radius (direction) of the rod along x, and the length dimension of the rod along y direction (so opposite of what you have). Use then a Y force excitation on the bottom of the rod (constant to excite S0 type of waves), since this is transient one does not need BC (fixed), start with a 5 cycle burst of 5 MHz, then you should see the guided wave going up or down along y direction. X=0 and the axis are the symmetry axis of the model so the centre line of the rod should be on the y-axis.

The dt, so time step (fixed time step and small deflections) should be in your transient 0.1 *(1/5MHz) (so 0.1*1/f_centre_excite). THe mesh size should be about wavelength_guidedwave/8. Search the internet for guided waves and finite elements and you will get lots of hits to look at (e.g., Imperial College NDE group has many publications and thesis that are available online)

The above are illustrated below.

And the S0 type mode is shown below, propagating along the pipe (so y-dir).

All the best

Erik

See the comments and the video, where they actually use a guided wave in the rod (force excitation always) in 3D.

If you do this in 2D which is fine for the symmetric type of modes in the rod, you would need to have the radius (direction) of the rod along x, and the length dimension of the rod along y direction (so opposite of what you have). Use then a Y force excitation on the bottom of the rod (constant to excite S0 type of waves), since this is transient one does not need BC (fixed), start with a 5 cycle burst of 5 MHz, then you should see the guided wave going up or down along y direction. X=0 and the axis are the symmetry axis of the model so the centre line of the rod should be on the y-axis.

The dt, so time step (fixed time step and small deflections) should be in your transient 0.1 *(1/5MHz) (so 0.1*1/f_centre_excite). THe mesh size should be about wavelength_guidedwave/8. Search the internet for guided waves and finite elements and you will get lots of hits to look at (e.g., Imperial College NDE group has many publications and thesis that are available online)

The above are illustrated below.

And the S0 type mode is shown below, propagating along the pipe (so y-dir).

All the best

Erik