Applying Multiple Load Steps to a Topology Optimization Problem in Heat Sink

DM_21595
DM_21595 Altair Community Member
edited August 2022 in Community Q&A

I am trying to perform Topology Optimization of a Heat Sink with a Baseplate using OptiStruct. I will try to define my setup below to the best of my abilities:

1. Define material, properties and connect these to each other as well the component.

2. Mesh the geometry.

3. Define a load collector 'Ambient' - create a node for ambient temperature with a value of temperature as 0 and all DOF turned off (Load Type = SPC).

4. Define a load collector 'Temp' - select the Baseplate face as the nodes for this temperature load with a value of temperature as 100 (Load Type = SPC).

5. Define a load collector 'X-Constraint' - select the sides of the Baseplate's face as the nodes for this load with this lateral dimension as the DOF turned on (in my model it is the X- direction) (Load Type = SPC).

6. Create a Load Collector SPCADD with Type as SPCADD and put Temp and Ambient in there.

7. Create 'Convection' interface and add all the elements of the Heat Sink FINS in this group. Go to CARD EDIT to make appropriate changes and connect Ambient Temperature node in the TA field under Edit section which creates the CHBDYE elements.

8. Add extra CARDS for the optimization to run on topology for CHBDYE elements.

9. Create a Load Step 'HTSS' with type as Linear Heat Transfer Steady State and SPC selected as SPCADD

10. Create another Load Step 'STRUCT' with type as Linear Static and SPC selected as X-Constraint. Turn on TEMP_LOAD and select the SubcaseID 1 'HTSS'. This takes the thermal loading conditions into consideration for the final solution.

BEGIN TOPOLOGY OPTIMIZATION :

1. Create DESIGN VARIABLE and choose the property of the fins in the required domain.

2. Create two responses : Thermal Compliance and Volume Fraction

3. Create a constraint : Volume Fraction less than 0.3

4. Create an Objective : Minimize Thermal Compliance. THIS IS WHERE I AM RUNNING INTO A PROBLEM. HOW DO I SELECT MULTIPLE LOAD STEPS HERE? SELECTING ONLY THE LINEAR HEAT TRANSFER STEADY STATE 'HTSS' DOES NOT GIVE ME CORRECT RESULTS AND SELECTING 'STRUCT' SHOWS ERROR.

Please let me know what can be done as a workaround. The optimized results are not what I expect them to be with little to no optimization in the fins visible. 

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Answers

  • Robert Hoglund
    Robert Hoglund
    Altair Employee
    edited August 2022

    Hi DM,

    For the thermal compliance response (TCOMP) you can only choose a heat transfer subcase.  That may be why you see the error selecting the static subcase. Optimizing the thermal compliance is useful if you want to improve the cooling performance of the structure.

    If you want to minimize the mechanical compliance, then you need to define a response of type 'static compliance' and formulate the problem to minimize compliance for the linear static subcase (with TEMP_LOAD from heat transfer subcase) with a constraint on volume fraction less than 0.3.

    Thanks,

    Rob H.

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