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FreeCAD: Stress Analysis (3/3)

Update: July 13, 2021
FreeCAD 0.19

Viewing result

Select "CCX_Results" in model tree and click FEM resultsfem-result to show result view dialog.

First we view the deformation. Select "Displacement Magnitude" on task tab to show deformation as color. Large deformations are shown in red, and small deformations are shown in green.

And minimum and maximum value of deformation will be shown on task tab. In this analysis, we find that the minimum value is zero and the maximum value is 6.95 mm.

Selecting Displacement Magnitude
Selects "Displacement Magnitude"
Show displacement with color
Show displacement with color

Then we view the actual deformation. Check "Show" on task tab and set "Factor" to 5. Now the shape will be deformed by five times its actual size.

Sets Factor to 5
Sets "Factor" to 5
Deformation of the shape
Deformation of the shape

Next we view the sress. Select "von Mises Stress" to show von Mises Stress (equivalent stress) as color.

And minimum and maximum value of the Mises Stress will be shown on task tab. In this analysis, we find that the minimum value is 3627.49 Pa and the maximum value is 74.27 MPa.

Selects von Mises Stress
Selects "von Mises Stress"
Show von Mises Stress with color
Show von Mises Stress with color

In this analysis, we use ABS as the material, and the yield stress (tensile yield stress) of ABS is generally around 35 MPa to 59 MPa. As a result of the analysis, the maximum stress was 74.27 MPa, which indicates that irreversible deformation occurs in this shape. When we view the Mises stress distribution, we can see that the stress is concentrated in the L-shaped corner where be painted with red. Therefore, we try to improve the shape to avoid the concentration of stress.

Shape improvement and checking the results

Double-click "Sketch" in model tree to edit the sketch which the shape based on.

Model tree
Model tree

Click "R 5 mm" for radius at the corner and change the radius to 30 mm.

Original sketch
Original sketch
Modified sketch
Modified sketch

When sketch editing is finished by clicking Close on task tab, the mesh will be automatically recreated.

Switch workbench to FEM workbenchWorkbench_FEM and delete resultfem-purge-results to remove old calculation result. Then Double-click "fem-solverSolverCcxTools" and re-run the calculation.

When the calculation is finished, select FEM resultsfem-result as before to check the deformation and stress.

The maximum value of deformation decreased from 6.95 mm to 4.89 mm.

View settings for displacement
View settings for displacement
Viewing displacement
Viewing displacement

The maximum value of Mises stress decreased from 74.27 MPa to 46.90 MPa and is about 40 % lower. It's not perfect yet, but it's stronger for the load than the first shape.

View settings for von Mises stress
View settings for von Mises stress
Viewing von Mises stress
Viewing von Mises stress

Saving and Loading Analysis

When you save the FreeCAD document as file, all analysis data will be saved to the file. And if you read the file that include analysis result, you should right-click the analysis in model tree and activate it to view the calculation result.

Activate the analysis
Activate the analysis
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