Module 08: Coupled Thermal- Structural Analysis

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

3 © 2019 ANSYS, Inc.33

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

4 © 2019 ANSYS, Inc.4

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

5 © 2019 ANSYS, Inc.5

• 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

6 © 2019 ANSYS, Inc.66 © 2019 ANSYS, Inc.6

• 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


• 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


• 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


• 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


• 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


• 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



• 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.



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


• 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


• You can apply both structural and thermal boundary conditions on the same geometry

08.06 Coupled Field


• The contacts will also give you the possibility to define a thermal conductance

08.06 Coupled Field


• Structural and thermal post-processing is available in the same project

08.06 Coupled Field


Please refer to your Workshop Supplement for instructions on:

Workshop 08.1 – External Data

08.07 Workshop 08.1 – External Data

../workshops/Mech-BNL_14.0_WS-02A-Large-Defl.ppt



Workshop 08.2 – Fluid Thermal Element FLUID116

08.08 Workshop 08.2 – Fluid Thermal Element FLUID116




Workshop 08.3 – Coupled Field

08.09 Workshop 08.3 – Coupled Field




Workshop 08.4 – Electro-Thermo-Mechanical Reliability For PCB ANSYS Mechanical Trace Mapping Solution

08.10 Workshop 08.4 – PCB Trace Mapping Solution

Module 08: Coupled Thermal- Structural Analysis

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