module 08: coupled thermal- structural analysis
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1 © 2019 ANSYS, Inc.11
Module 08: Coupled Thermal-Structural Analysis
ANSYS Mechanical Heat Transfer
Release 2019 R3
2 © 2019 ANSYS, Inc.2
Module 08 Topics
1. What is a Coupled Field Analysis
2. Coupling Thermal-Structural Analyses
3. Coupling Multi-Step Analyses
4. Coupling Using Dissimilar Meshes
5. Postprocessing
6. Coupled Field
7. Workshop 08.1 – External Data
8. Workshop 08.2 – Fluid Thermal Element FLUID116
9. Workshop 08.3 – Coupled Field
10. Workshop 08.4 – PCB Trace Mapping Solution
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08.01 What is Coupled Field Analysis
A coupled field analysis is a combination of analyses from different engineering disciplines. Each field has DOFs associated with it.
• Thermal Stress Problems – Loose Coupling
– temperature distribution from a thermal analysis induces thermal strains in a structural analysis.
– Often deformation rarely influence the temperature distribution →this is referred to as one-way coupling.
– In Mechanical the temperatures resulting from a thermal analysis are mapped to the structural analysis as a thermal load.
– In this type of coupling – a one way or weakly coupled system - the thermal analysis precedes the structural.
• Fully coupled analysis, where the fields are solved simultaneously
– Tight, full or direct coupling, is possible with the ANSYS Coupled Field Element (22X series).
– Possible within ANSYS Mechanical via Command Objects or ACT Extension.
– Usage is outside the scope of this seminar.
𝑻 ≠ 𝒇(𝒖)
𝒖 = 𝒇 𝑻
𝑻 = 𝒇(𝒖)
𝒖 = 𝒇 𝑻
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Method 1
Load transfer‐ Structural and thermal physics are solved
sequentially. Two or more analyses are coupled by applying results from one analysis as loads to another.
‐ Separate models and meshes possible.
Technology‐ System coupling.
Method 2
Direct coupled-field analysis‐ Structural and thermal physics are solved
simultaneously in a single analysis.
‐ Single model, mesh and set of results.
Technology‐ Coupled-field element.
Thermal
Structural ThermalStructural
08.01 What is Coupled Field AnalysisThermal-Mechanical Solutions
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• Implemented as a coupled-field element type with structural and thermal degrees-of-freedom (MAPDL 22X elements).
• Typically used for highly nonlinear thermo-mechanical static and transient problems with.
- Material and geometric nonlinearities.
- Temperature dependent material properties.
- Multiphysics contact.
• Allows a harmonic analysis for linear thermo-mechanical problems.
• Access in ANSYS Mechanical through command objects or ACT extensions.
08.01 What is Coupled Field AnalysisDirect Thermal-Mechanical Analysis
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• Mechanical can couple a thermal model to a structural one where the meshes are shared or dissimilar.
• The setup is achieved in the Workbench Project Schematic by dragging/dropping a structural system onto the Solution cell in a thermal system.
• From the schematic we can see the solution transfer from thermal to structural. In addition, Engineering Data, Geometry and Model are shared as well.
• In this specific example the thermal and structural models will have identical meshes.• You can also import temperature load from another solver via ‘External Data’. Please
refer to workshop 08.1.
𝒖 = 𝒇 𝑻
𝑻 ≠ 𝒇(𝒖)
08.02 Coupling Thermal-Structural Analyses
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• Within the Mechanical application the structure of the tree indicates the coupling of environments.
• An “Imported Load” branch is automatically inserted to the structural environment when coupled analyses are setup in the project.
• The imported load branch, in this case, contains an “Imported Body Temperature”.
• The details of the body temperature branch indicate the source of the data.
08.02 Coupling Thermal-Structural Analyses
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• In cases where the thermal analysis is a multi-step or transient analysis the structural analysis can be coupled to any solution point from the thermal.
• In this example a transient thermal analysis is coupled to a static structural one.
• In cases of multi-step or transient thermal solutions, different “Source Times” can be chosen to apply to the structural solution.
08.03 Coupling Multi-Step Analyses
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• In cases where both thermal and structural analyses are multi-step or transient, the imported load can be configured as desired.
• Here a thermal transient analysis has been coupled to a multi-step structural.
• As shown, the temperatures from T=4s in the thermal transient have been mapped to the third structural load step.
08.03 Coupling Multi-Step Analyses
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• Shown here are several variations on schematic setup.
• In each case the Model cell for each analysis type is independent.
• This means different mesh controls can be applied on the thermal and structural models.
• Where dissimilar meshes exists a load mapping technique is used to interpolate temperatures from the thermal model onto the structural.
08.04 Coupling Using Dissimilar Meshes
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• When dissimilar meshes are used a mapping technique is employed to transfer temperatures to the structural model.
• The default “Program Controlled” setting chooses the most accurate mapping based on an evaluation of both meshes.
• A series of manual mapping controls are available. In general these controls are used in special cases like fluid structure interaction (FSI), 2D to 3D projection, etc.
- For information on these advanced controls, see the appendix section “Appendix B. Data Transfer Mesh Mapping and Validation” in the “Mechanical User’s Guide” documentation.
For example, the “weighting” algorithms are:• Triangulation• Distance-based average• Shape function• Kriging
08.04 Coupling Using Dissimilar Meshes
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• Prior to solving the structural model, the temperature loads can be imported and reviewed.
• Once complete, the temperature distribution can be displayed graphically as shown here.
08.04 Coupling Using Dissimilar Meshes
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Both Solutions are available for post processing.
In this example, the models/meshes are shared and results are simultaneously available in the same model tree.
08.05 Postprocessing
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• Couple field will allow you to simulate a strong thermo-mechanical coupling
• It means that the displacements and the temperature are degrees of freedom in the same element. No imported load to the structural analysis
08.06 Coupled Field
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• You can apply both structural and thermal boundary conditions on the same geometry
08.06 Coupled Field
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• The contacts will also give you the possibility to define a thermal conductance
08.06 Coupled Field
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• Structural and thermal post-processing is available in the same project
08.06 Coupled Field
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Please refer to your Workshop Supplement for instructions on:
Workshop 08.1 – External Data
08.07 Workshop 08.1 – External Data
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Please refer to your Workshop Supplement for instructions on:
Workshop 08.2 – Fluid Thermal Element FLUID116
08.08 Workshop 08.2 – Fluid Thermal Element FLUID116
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Please refer to your Workshop Supplement for instructions on:
Workshop 08.3 – Coupled Field
08.09 Workshop 08.3 – Coupled Field
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Please refer to your Workshop Supplement for instructions on:
Workshop 08.4 – Electro-Thermo-Mechanical Reliability For PCB ANSYS Mechanical Trace Mapping Solution
08.10 Workshop 08.4 – PCB Trace Mapping Solution
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