Learning Forum

[emmanouil.trachanas]

Hello!

I am performing a coupled Transient thermal and Transient Structural Analysis. In transient thermal I model a "grated" Gaussian laser beam that strikes the surface of a metal and excites spatial temporal variations of temperature. The simulation domain is part of a bigger sample (25mmx25mmx2mm) so in reality the metal surface is much larger compared to the grating period (6.4 um) so due to computational expense I cannot simulate it all.

 

The resulted temperature profile (see picture below) is then imported as external load to transient structural analysis in order to monitor the generated Surface acoustic waves that propagate and decay (SAWs).  The expected directional deformation along the z axis should in theory be like the second picture from experimental data. Although the signal that I get from Ansys transient structural either with Fixed or open boundary conditions (3rd picture) contains higher harmonics and it seems full of reflections. Is it possible to advice  what type of boundary conditions I should use in order to avoid these reflections and clean the signal?. Because I need to use 20 elements per wavelength to correctly catch the thermal grating and the SAW it is not easy to infinitely enlarge my domain 

 

thank you for alla your help and support

 

 

 

 

[emmanouil.trachanas]

this is an example of the theoretical expected displacement sisgnal

[Erik Kostson]

 

 

Hi 

We do not have an easy way to absorb these elastic waves in transient structural  – only thing is to use infinite elements (see einfin command)

 

Perhaps this will help:

/forum/forums/topic/transient-analysis-with-infinite-element/

 

Because it is hard to use these elements and command (einfin) I would sugget to couple a Transient Thermal -> LS-Dyna and in there (LS-DYna) use the keyword manager and keyword:

*BOUNDARY_NON_REFLECTING

 

All the best

Erik