Documentation

Static stress analysis: Underrun protection device

In the following you find a step-by-step instruction for a static stress analysis of an underrun protection device. Note that the complete analysis is static, dynamic effects are neglected.

Import tutorial case into workbench

Step-by-step

Import tutorial project

  • To start this tutorial, you have to import the tutorial project into your ‘Dashboard’ via the link above.

The CAD model

  • Once the ‘Work bench’ is open you will be in the ‘Geometries’ tab.
  • The CAD model named “underrun-protection_design-1” would be displayed in the viewer, as shown below
  • You can interact with the CAD model as in a normal desktop application
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CAD model displayed in the viewer

Create a Static Analysis

  • To create a new simulation click on the ‘+’ option next to the ‘Simulations’ tab
  • In our case we are interested in running a static stress analysis, so select the Static Analysis option and press ‘Ok’
  • After clicking ‘Ok’, a new tree will be automatically generated in the left panel with all the parameters and settings that are necessary to completely specify such an analysis.
  • All parts that are completed are highlighted with a green check. Parts that need to be specified have a red circle. While, the blue circle indicates an optional settings that does not need to be filled out
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Analysis Type

 Create a mesh

  • As Finite Element analyses are carried out on discretized domains, we have to generate a Mesh for our CAD model.
  • Therefore as the next step select the Mesh option
  • Default mesh parameters are used, as shown in figure
  • The Tet-dominant is the only algorithm available for FEA cases such as ours
  • First order elements are used here
  • Note that the results generated with First order elements might not be as accurate as with Second order elements. But choosing a Second order mesh will lead to longer computing times so is avoided here.
  • As for the fineness of the mesh, Coarse is sufficient. As a rule of thumb, one should make sure, that the resulting mesh does have more than one volume layer across the cross section of the model.
  • For actually starting the mesh operation hit the ‘Generate’ button, highlighted in the figure below
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Generating the mesh
  • The resulting mesh is shown in figure below
  • There is also a Meshing log (highlighted below) available which provides quantitative information about the mesh in terms of its node and element count and other relevant data
  • That completes the mesh generation.
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Generated Mesh

Material selection and assignment

  • Next, add the materials from the ‘Material Library’ for fluid and the solid phases. First, we start with clicking on sub-tree “Materials”, click on ‘+’ from the options panel as shown.
  • This pops-up a ‘Material Library’ from which we select “Steel” and click on ‘Ok’. This will then load the standard properties for steel.
  • Then, assign the material to the domain and save.
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Adding a new material
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Assigning the material to the domain

Boundary conditions

Now, we come to define the boundary conditions.

  • To create a boundary condition, click on the ‘+’ option next to the Boundary conditions and select the required boundary condition from drop down menu, as shown in figure.
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Creating a new boundary condition
  • We start with the Constraint boundary conditions at the fixation holes
  • For this select the ‘Fixed Value’ boundary condition from the drop down menu
  • Set the displacement to zero in all directions, as shown on figure.
  • Next, assign this boundary condition to the fixation holes
  • Clicking on Save completes the definition of this boundary condition
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Fixed Value boundary condition
  • The second boundary condition is the actual pressure load that acts on the shield of the underrun protection
  • So we select the ‘Pressure’ boundary condition from the drop down menu
  • Enter a pressure value of 25 bar or 2.5*10e6 Pa
  • Assign the boundary condition to ‘solid_0_face_7’, as shown in figure below
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Pressure Boundary condition
  • The next two tree items Numerics and Simulation Control are already indicated as complete via the green checks. This means that reasonable default values are already chosen for it, so we leave them as they are.

Start a simulation run

  • The last thing to do for running this simulation is to create a run.
  • The new run is created by clicking on the ‘+’ symbol next to ‘Simulation Runs’
  • Give a name to the run and start the run
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Creating a new run

 Post-Processing

  • Once the simulation is finished, select the ‘Solution fields’ under the Run to post process the results on the platform. Or they can be downloaded and post-processed locally (e.g. with ParaView)
  • Some post processing images from the SimScale platform post processor are shown below.
  • Select the results and click “Von mises stresses” to visualize the Von mises stresses in the structure
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Von Mises stress distribution
  • Similarly the displacement field can be visualized as shown below
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Displacement Field

 

 

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