Symmetry Optimisation - Bridge
- Lennart Krueger
- SHK
Goal of this tutorial
Get to know the optimisation model setup with symmetry constraint
Training:
Relevant data for this tutorial:
Step 1: Start MSC Apex Generative Design
The program starts and you can directly create your optimisation model
Step 2: Model generation
You can either create the geometry directly in MSC Apex Generative Design or import already existing files. You can import for example .xb, .xt, .step, and .sldprt files into the program.
Import/create the Design Space including the Interfaces (Non-Design Spaces) in MSC Apex Generative Design as one solid. For this Bridge the already prepared Design Space was imported.
Open the Design Space Tool in the Optimization Tools to select the imported Geometry as the Design Space. Activate the Symmetric Design Constraint and select the XZ and YZ planes to set up the symmetric optimisation.
If symmetry is activated, the Z-direction of the symmetry coordinate system is the build direction. Therefore the symmetry coordinate system needs to be adjusted. For this the transformation option can be changed to rotating the coordinate system with “R”. Select the red ring for rotation about the x-axis (-90°). The Z-direction shouldn’t be orientated normal to a symmetry plane. Further information regarding build direction and support reduction can be found here.
Create the material in the Materials editor and assign it to the Design Space. In this case the material behaviour is Isotropic.
The specific values needed are the Young's Modulus (192372 MPa), Poisson ratio (0.3) and Density (7.97E-6 kg/mm3).
The Tension Strength is the maximum allowable stress for the material and is set to 320 MPa.
Step 3: Definition of boundary conditions
With the view display controls in the left top corner the Design Space can be activated to visualize the mirrored geometry. Boundary Conditions can be applied only on the Design Space solid and are mirrored as well.
Go to the Loads & Boundary Condition Tool to enter the loads and fixations. Displacements, Forces, Moments, Gravity and Pressure Loads can be applied using different selection options.
In this case one force is defined (on the top plate volume):
Name | Force/Moment/Pressure/Gravity | Direction | Value in N |
|---|---|---|---|
Force - Moment 1 | Force on surface | y | -4000 |
One constraint on the foot is created and attached on the Non-Design Space:
Name | Direction |
|---|---|
Constraint 1 | x, y, z (=0) |
Step 4: Interface Creation
Interfaces have to be created for every functional surface - so every surface where a boundary condition is applied to. With this Tool an offset to the inside with the input “Non-Design Space Thickness” and an offset to the outside with the input “Machining Allowance” is created. The Offset Distance is expanding the Interface to the set value to create material on front faces.
One Interface is created on the same surface the force is applied to. Therefore, an Non-Design Space Thickness of 1 mm and a Machining Allowance of 1 mm is entered. Now select the surface and confirm the selection (MMB)
One Interface is created on all surfaces, except the top one, of the fixation Non-Design Space. Therefore, an Non-Design Space Thickness of 3 mm and a Machining Allowance of 2 mm is entered. Now select the surfaces and confirm the selection (MMB).
Step 5: Definition of Events (load cases)
The next steps are defined in the Studies area.
All boundary conditions must be assigned to the specific load cases, which are defined as Events. The number of Events can be changed by adding/deleting Events to the GD Scenario. The assignment of the boundary conditions to the Events can be made in the Loads & Constrains Window. The already created loads and constraints that concern the Design Space are listed in this window and can be activated for each Event individually.
Active in Event1: Force-Moment 1 and Constraint 1
Step 6: Definition of optimisation parameters
The optimisation parameters are selected in the Studies Area as well.
Manufacturing Method: Generic AM
Failure Criteria: Von Mises
Safety Factor: 6 (Stress Goal: 53,33 MPa)
You can switch between the Safety Factor and Stress Goal in the properties panel by clicking the gear wheel.Strut Density: Medium
Shape Quality: Balanced
Don’t forget to save the project!
Step 7: Starting the optimisation and visualizing the results
If all data is correct, the optimisation can be started and tracked in the Post Processing. The Analysis Readiness function checks if all information is provided and the optimisation can start.
All result iterations are displayed as soon as they are available. Furthermore, you are able to stop the optimisation in this selection area. However, a Restart is not directly possible.
The optimisation is finished after 64 iterations (Shape Quality: Balanced).
You can check the status of the optimisation in the GD Status and get more information on Warning and Error messages. This can be done directly in the Post-Processing as well as in the Studies tab for an optimisation that has already run.
Step 8: Visualization of Stresses, Displacements & Mass
The legend can be influenced in different ways. You can add and reduce the stress/displacement steps, enlarge different steps and set new minimum and maximum values. The picture below shows the stress distribution with a scale spectrum from 0 to 2 times the stress goal, which is a good fit for all optimisations. This displays the even distribution of the selected stress goal with the colour range of green and critical points are viewable in red.
You can go back to the model setup by clicking the Exit button in the right bottom corner.
The whole MSC Apex Generative Design project with all results can be downloaded here:
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