## Laser absorption in lens and thermo-elastic analysis

Numerical methods and mathematical models of Elmer
Jonas231
Posts: 2
Joined: 03 Sep 2022, 21:47
Antispam: Yes

### Laser absorption in lens and thermo-elastic analysis

Hello,
I am a beginning user of Elmer and would like to apply fem for thermo-mechanical analysis.

A laser beam shall hit a glass volume (or several ones, lenses). Intensity distribution will be determined in a raytracing program. In this case a 3d temperature profile would result and the body (lens) would be deformed. I am wondering how to simulate this deformation and how to setup the initial temperature distribution (volume heating source) for the fem simulation. Say I know the initial energy / temperatue of the laser beam for each node, how do I input it in elmer? The body is a step or iges file.

Has anyone here experience with this kind of thermo-elastical fem analysis? Do you know a close example from which to learn?

Regards,
Jonas
Rich_B
Posts: 227
Joined: 24 Aug 2009, 20:18

### Re: Laser absorption in lens and thermo-elastic analysis

Hello,

As a new user of Elmer, be sure to review the GetStartedElmer.pdf document, it is helpful for Linux users as well as Windows users.

https://www.nic.funet.fi/pub/sci/physics/elmer/doc/

For your case, you may want to look in the ElmerTutorials-nonGUI.pdf document for the tutorial 'Thermal actuator driven with
electrostatic currents'. This tutorial uses StatCurrentSolve, HeatSolve, and StressSolve and calculates thermally induced displacement and stress. You would not need to use StatCurrentSolve, so that could be removed.

If you would like to start with a simple geometry, look in the ElmerTutorials.pdf for the tutorial 'Magnetic field induced by harmonic
current in a wire'. This tutorial uses a 3D wire model, with two concentric bodies. Apply the same glass material to both bodies. Set the outermost boundary to room temperature, so there will be a sink for the heat.

For a first attempt, apply different initial temperature conditions to the two bodies. Start with the outer body at room temperature, and the inner wire body at an elevated temperature as the heat source.

For a second attempt, instead of applying different initial temperatures, set both bodies to room temperature and apply a body heat source to just the inner wire body.

It always helps if you have a simple model that you can post, preferably a complete solution, with geometry and a sif file.

Rich.
Rich_B
Posts: 227
Joined: 24 Aug 2009, 20:18

### Re: Laser absorption in lens and thermo-elastic analysis

Hello,

Attached is an example using a body force to heat the inner wire using a pulsed approach.
wire-model.png (162.7 KiB) Viewed 248 times
Rich.
Attachments
body-force.7z
Rich_B
Posts: 227
Joined: 24 Aug 2009, 20:18

### Re: Laser absorption in lens and thermo-elastic analysis

and here are some of the results of the simulation.

Rich.
body-force-von-mises.png (174.67 KiB) Viewed 247 times
body-force-temp.png (142.62 KiB) Viewed 247 times
body-force-temp.mp4
kevinarden
Posts: 1583
Joined: 25 Jan 2019, 01:28
Antispam: Yes

### Re: Laser absorption in lens and thermo-elastic analysis

and if instead of body force you wanted to specify a temperature for each node then instead of a body force load you would write a boundary condition to target a node or nodes such as

Boundary Condition 3
Name = "Target Nodes"
Target Nodes(4) = 895 897 899 901
Temperature = 350.0
End

Example sif attached.
case2.sif