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Simulation of laser drilling

  1. Sep 17, 2008 #1
    Does anyone know how to simulate the pulse laser drilling?

    I am trying to use Comsol or matlab to simulate the laser interaction with a specified piece of material.

    Following, plot the time (X axis) versus temperature (Y axis) diagram
    to see the temperature distribution.

    Any help in comsol or matlab is deeply appreciated.

    Rgds
     
  2. jcsd
  3. Sep 17, 2008 #2

    Mech_Engineer

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    If you have data on the diffraction/absorbtion properties of the material being drilled at the specific wavelength of the laser, modeling will basically be a transient thermal model with the laser modeled as a heat flux at a spot on an external surface of the part. Actually modeling the melting and/or drilling of the material could be a good bit more difficult however, and will probably be too involved for a beginner.
     
  4. Sep 17, 2008 #3
    Hi Mech_Engineer,

    The thing is that I am very new to the COMSOL and my project is to simulate this laser drilling. I have been trying to ask around on how to work out the simulations as well as entering the correct syntax at the correct places.


    Right now I am using Conduction>Steady State Analysis. I then create a rectangle to simulate a piece of material.

    Then there is this subdomain and boundary settings which I do not know what to key into the empty fields provided to simulate the laser drilling, especially when the laser 'goes deeper' into the material until a hole is created.

    I think its more complex to solve this using matlab.

    Any one can help???
     
  5. Sep 17, 2008 #4

    Mech_Engineer

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    I would say that simulating a complex operation like laser drilling would be a very difficult problem to accurately model, even for an experienced team of FEA analysts. Material properties like absorbtivity and thermal conductivity can change drastically with large temperature ranges, and modeling the liquid/vapor phase changes occuring in the melt/vaporization pool of the laser would be to say the least daunting.

    This would be a transient problem, since the material is heated very quickly to melting using the laser. A steady state analysis will just end up giving you a bunch of useless gibberish that is not even close to a laser drilling operation.

    What aspects of a laser drilling operation are you specifically trying to gain insight into? Things like how long it takes the local area to begin melting given a certain power laser would probably be able to be modeled with a certain degree of accuracy, but modeling the entire operation including material melting and vaporization would be huge undertaking with questionably accurate results.
     
  6. Sep 17, 2008 #5
    Oh dear, this really sounds difficult.

    Sorry, my mistake. I did choose transient analysis so as to plot the temperature over time. What I am looking at, is just like what you have mentioned, the time and temperature that the local area begins melting given a specific laser intensity.

    Subsequently this process is repeated until a hole is being created at the bottom of the 'rectangle'.

    I will skip the vaporization part and assume material melting only.

    Any help anyone?

    Rgds
     
  7. Sep 18, 2008 #6

    Mech_Engineer

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    Certain aspects of it can be very difficult, depending on what you are trying to achieve with the model...

    Well finding how long an area takes to heat to melting temperature is fairly straightforward; however, the analysis is only valid until any part of the plate gets close to the melting temperature. Once parts are melting, in my opinion things probably get a lot fuzzier. How accurate does this model have to be? Are you just trying to size an appropriate laser for a laser drilling machine given a material thickness?

    Are you taking into account temperature dependence of material properties like thermal conductivity and radiative properties like absorbtivity and emissivity? Are you including radiation heat transfer in your model at all?
     
  8. Sep 19, 2008 #7
    I am only doing a simple simulation whereby I assume that the laser is the heat source. Upon interataction with the material for a specified time, the material will reach melting point at that particular location.

    I assume that the material is vapourised by the laser and there will be no molten. The second assumption is that there will be no heat loss due to convection and radiation. Heat loss is only due to conduction.

    Do you mind if you pm me you email address? Maybe a picture will be clearer what I hope to simulate.

    Rgds
     
  9. Sep 19, 2008 #8
    And to make things easier, I will choose the materials in the drop down box in COMSOL.
     
  10. Sep 25, 2008 #9
    I want to create a material in COMSOL. Lets assume its rectangular in shape.

    There is this part where when we open the COMSOL, there is a drop down box whereby we can choose "2D" or "Axial Symmetry (2D)"

    Whats the difference between the 2?
     
  11. Sep 26, 2008 #10

    Mech_Engineer

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    ALL of this I'm sure is covered in the Comsol help files...

    Axisymmetric modeling is used to model geometries that are symmetric about a central axis, such as a pipe with flanges on the ends, or a cylindrical pressure cylinder.

    2-D modeling would be for simplified modeling of long geometries with the same cross-sectional geometry along their length, like a pipe or perhaps the cross-section of a dam.
     
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