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[Tutorial Template] Thermomechanical Analysis of an Engine Piston

This article provides a step-by-step tutorial for a thermomechanical simulation of an engine piston under maximum pressure and temperatures.

eingine piston thermomechanical simulation cauchy stress distribution
Figure 1: Visualization of the cauchy stress distribution on the piston.

Overview

This tutorial teaches how to:

  • set up and run a thermomechanical simulation
  • assign topological entity sets in SimScale
  • assign boundary conditions, material and other properties to the simulation
  • mesh with the SimScale standard meshing algorithm

We are following the typical SimScale workflow:

  1. Preparing the CAD model for the simulation
  2. Setting up the simulation
  3. Creating the mesh
  4. Run the simulation and analyze the results

1. Prepare the CAD Model and Select the Analysis Type

First of all click the button below. It will copy the tutorial project containing the geometry into your own workbench.

The following picture demonstrates what should be visible after importing the tutorial project.

cad model engine piston tutorial starting point
Figure 2: Imported CAD model of an engine piston in the SimScale workbench.

1.1 Some Heading

[In case topological sets are required, predefine most of them in the tutorial link so that the user only needs to define a few, this shortens the tutorials a lot]

1.2 Create the Simulation

creating a new new simulation menu
Figure 3: Creating a new simulation.

Hitting the ‘Create Simulation’ button leads to the following options:

simscale analysis library
Figure 3: SimScale simulation library.

Choose Thermomechanical as analysis type and create the simulation.

2. Assigning the Material and Boundary Conditions

In order to have an overview, the following picture shows the boundary conditions applied for this simulation:

overview boundary conditions thermomechanical simulation of an engine piston
Figure 4: Overview of the boundary conditions for the engine piston.

2.1 Some Heading

2.2 Define a Material

material library for thermomechanical analysis
Figure 5: Material library.

2.3 Assign the Boundary Conditions

In the next step boundary conditions need to be assigned, for this setup, thermal and mechanical boundary conditions are required.

a. Thermal Conditions

Starting with the thermal conditions, one needs to create a convective heat flux according to the following picture.

boundary conditions available in thermomechanical simulations within simscale
Figure 6: Boundary conditions.

After hitting the ‘+ button’ next to boundary conditions there will pop up a drop down menu where one can choose between different boundary conditions.

assigning a convective heat flux at the top of an engine piston
Figure 7: Assign the first boundary condition.

b) Mechanical Conditions

assigning a remote displacement to fix the engine piston
Figure 8: Define the first remote displacement.

Don’t worry about the numerics and the simulation control settings, as their default values are optimized according to the chosen analysis type, hence valid for the majority of simulations. If you are a simulation expert however, you can have a look at them and change the settings as you like.

You can use result control to observe the convergence behavior of certain items of interest. In this simulation it is not required.

3. Mesh

To get the mesh, we recommend using the standard algorithm, which is a good choice in general as it is quite automated and delivers good results for the most geometries.

The only change you need to do here is changing the sizing to ‘manual’ and define ‘1.8e-3 m’ as a cell size and ‘enable 2nd order elements’. Make sure your setting look like the picture below:

standard mesh setup with manual edge length setting
Fig 9: Standard meshing menu

Did you know?

Often, large changes in the mesh’s cell sizes are only spotted in a few regions. Increasing the global mesh refinements rises the cells drastically.
When using the standard mesher, Simscale offers the option of physics based meshing. This algorithm detects regions which require a finer resolution based on the boundary conditions set.
You can also do this manually, by using one of the local refinement options, foremost being feature, surface and region refinements.

[Add info boxes either about theoretical background or advertising features or other setup possibilities, only for advanced tutorials, though]

The resulting mesh will have about 235k nodes and look like this:

mesh of engine piston
Figure 10: Mesh of the engine piston.

4. Start the Simulation

start a new simulation and what the setup should look like before doing so
Figure 11: Simulation setup tree before starting the simulation.

Now you can ‘start’ the simulation and after about 10 minutes you can have a look at the results.

possibilities of starting the post processor
Figure 12: Possibilities of starting the post processor.

While the results are being calculated you can already have a look at the intermediate results in the post processor. They are being updated in real time!

5. Post-Processing

[For now only show the interested results and link the pp guide, once the new pp is released write about the potential of the pp , as it covers the value for customers]

cauchy stress distribution as a result of the thermomechanical simulation of an engine piston
Figure 13: Cauchy stress distribution.

Analyze your results with the SimScale post processor. Have a look at our post-processing guide to learn how to use the post-processor.

Congratulations! You finished the tutorial!

Note

If you have questions or suggestions, please reach out either via the forum or contact us directly.

Last updated: November 19th, 2020

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