How to Setup a Car Damper Analysis in Nastran

Thermal Analysis Setup

Step-by-Step Guide: Thermal Analysis Setup

Modeling the Car Damper:

1. 1. Copper Cylinder Setup:
      • • Create a copper cylinder supported by two steel plates.
      • • Set initial temperature to 296 K across all components.

1. 1. Convection Coefficient Application:
      • • Apply a convection coefficient to ambient on all surfaces of the assembly.

1. Temperature Fixation:
   • • Fix the temperature at one end of the cylinder to 400 K.

   

Running Steady-State Analysis:

1. 1. Steady-State Analysis Execution:
      • • Run a steady-state thermal analysis to determine temperature distribution at equilibrium.

1. Analyzing Temperature Distribution:
   • • Observe results to understand heat flow and note areas of high thermal gradient.

Static Analysis with Thermal Mapping

Temperature Mapping with MSC Patran:

1. 1. Create a ‘Continuous Scalar Field’:
      • • Generate a field representing temperature interpolation across the model.
      • • Ensure accurate reflection of the steady-state analysis results.

1. 1. Generate Temperature Load:
      • • Create a temperature load using the ‘Continuous Scalar Field’.
      • • Verify thermal load matches boundary conditions and gradients from thermal analysis.

1. Apply Temperature Load for Static Analysis:
   • • Integrate the temperature load into the mechanical analysis setup.
   • • Ensure correct application of thermal loads to the structural model.

Running Static Analysis:

1. 1. Execute the Static Analysis:
      • • Run the static analysis in Nastran using the mapped temperature load.
      • • Monitor solver convergence and thermal load application.

1. Assess Stress from Thermal Expansion:
   • • Evaluate stress, strain, and displacement distributions.
   • • Generate contour plots to visualize structural performance under thermal expansion.

Efficiency with HEATSTAT Parameter

To improve analysis efficiency, leverage the HEATSTAT parameter in Nastran for linear steady-state simulations.

Using the HEATSTAT Parameter:

1. 1. Defining the Thermal and Static Subcases:
      • • Configure Nastran input file with two subcases: thermal and static analysis.

1. 1. Including the HEATSTAT Parameter:
      • • Add HEATSTAT(THERMAL)=YES to the thermal subcase in the case control section.

1. 1. Running a Two-Subcase SOL101 Analysis:
      • • Specify subcase sequence: thermal analysis followed by static analysis.

1. 1. Referencing Thermal Results in Static Analysis:
      • • Ensure thermal analysis outputs are usable by the static analysis.

1. Integrating Results:
   • • Run Nastran analysis with combined subcases.
   • • Verify correct execution and application of thermal results to static subcase.

Benefits of the HEATSTAT Approach:

• • Optimizes simulation time for large-scale models

• • Maintains consistency between thermal and static results

• • Automates linking of thermal and structural analyses

Note: Ensure the linear steady-state assumption is valid for your specific use case before using this approach.

Meshing and Model Setup

Geometry Import and Creation:

1. 1. Importing Geometry:
      • • Use compatible CAD tools to import damper geometry in STEP or IGES format.

1. Creating Geometry:
   • • If necessary, manually create the damper model following technical specifications.

Model Clean-Up:

1. 1. Remove Unnecessary Features:
      • • Simplify minor features that don’t significantly impact analysis.

1. Check for Gaps and Overlaps:
   • • Ensure geometry integrity to prevent meshing issues.

Applying Material Properties:

1. Define Material Properties:
   • • Assign properties to different components, including thermal properties.

Choosing a Meshing Strategy:

1. 1. Mesh Types:
      • • Select appropriate mesh types based on geometry complexity.

1. Mesh Refinement:
   • • Refine mesh in critical stress locations and areas with high thermal gradients.

Meshing Process:

1. 1. Generate Mesh:
      • • Create mesh following the specified strategy, ensuring quality elements.

1. 1. Mesh Quality Check:
      • • Conduct quality checks focusing on element distortion, skewness, and aspect ratio.

1. Boundary Layer Mesh:
   • • Consider using boundary layer meshes for fluid interactions or surface behaviors.

Load Application and Boundary Conditions

Defining Boundary Conditions:

Constraint Type	Application
Fixed Constraints	Apply to points where the damper is rigidly attached.
Roller Constraints	Use for parts that can move in specific directions.
Pinned Constraints	Apply where components are hinged or pivoted.

Applying Loads:

1. 1. Force Loads:
      • • Define static and dynamic forces experienced during operation.

1. 1. Pressure Loads:
      • • Apply to areas experiencing distributed forces.

1. Displacement Loads:
   • • Specify displacements to simulate movements or deformations.

Incorporating Special Loading Conditions:

• • Follower Loads: Use for loads that change direction with structure deformation.

• • Moving Loads: Apply to simulate varying load points during operation.

• • Temperature Loads: Incorporate temperature gradients from thermal analysis.

Accurate boundary conditions and load applications ensure realistic simulation of the damper’s operational scenarios, providing a foundation for precise analysis and performance evaluation. The quality of these inputs directly impacts the reliability of the simulation results, making them crucial for effective damper design and optimization.

References

1. 1. Cook RD, Malkus DS, Plesha ME, Witt RJ. Concepts and Applications of Finite Element Analysis. 4th ed. John Wiley & Sons; 2001.

1. 1. Bathe KJ. Finite Element Procedures. 2nd ed. Klaus-Jürgen Bathe; 2014.

1. 1. MSC Software Corporation. MSC Nastran 2021 Reference Manual. MSC Software; 2021.