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General Mechanical

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Additive Workbench – How to change the porosity of a material within a simulation

    • dingyangyao1995


      I am trying to simulate a DMLS process where a layer of powder is heated up by a moving heat source (laser) and solidifies. The material used in the simulation is constant (TI64) but I need to distinguish and change its porosity from its different states. For example, the porosity would be a function of temperature. At TTm, it would have a porosity of 0.01. How would I do this?

      Also, I assume that if I can do this, then I can also couple it with structural analysis and be able to get the structural solution of the part as it is being built right?

      Thank you for your help.

    • aolleak

      I have seen this being done with COMSOL. But I don't think this is an available option with ANSYS. Changing the element state based on the temperature requires entering /POST1. If you do so, you cannot proceed solving from the last step, unless you quit and restart the problem from the last step.

      As you have three states, you have to define the three states at different material IDs, and do the following.

      1. Solve for a short laser movement (half mm for example, and make sure to enable restart)

      2. Enter /POST1

      3. Use NSEL command to select nodes within temperature range (NSEL,S, for step 1, and NSEL,A, for all following steps), and write these nodes somewhere 

      4. Clear everything

      5. Launch a restart analysis from the last step.

      6. Read the nodes saved in step 3 (you can have a script for that), and select the attached elements.

      7. Change the element material using MPCHG,MAT_NO

      8. Solve again for another shorter scan



      You can use element 227 and run both (thermal and structural) once but It may not converge. 


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