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Goal of this tutorial
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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 Elastic Modulus (192e3 MPa), Poisson’s 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.
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Creation of local coordinate systems to apply forces
For this model one Local Coordinate System needs to be created to easily apply the corresponding force to the model.
By opening the Coordinate Tools a local coordinate system is created by entering the three orientations (alpha = 75°, beta = 90°, gamma = 315°) and placing it on the front plane (coordinate system 1).
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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.
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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 “Interface Thickness”(Non“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.
Ten interfaces Interfaces are created for the force application and fixation regions. Therefore, an Interface Non-Design Space Thickness of 3 mm and a Machining Allowance of 1 mm is entered. Because not only the inner faces touching the screw but also the front and back face are supposed to contain material and have sharp, functional faces, an Offset Distance of 3 mm is entered. Now select the inner surfaces of the fixation and confirm the selection (MMB).
Note: the Interface Offset (usually displayed in red) is not visualized due to a limitation. The correct value will be considered in the optimisation.
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Manufacturing Method: Generic AM
Failure Criteria: Von Mises
Select the Strut Density: Medium
Select the Shape Quality: Balanced
Set the Complexity Setting: 67
Keep Non-Design Spaces: All Constraints and Interfaces 5-10 are deactivated
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Don’t forget to save the project!
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The chosen Safety Factor calculates automatically with the entered maximum allowable Tension Strength the Stress Goal for the optimisation. By clicking on the Gear-Button behind the Safety Factor the detailed menu for the Safety Factor and Stress Goal shows up.
The maximum allowable stress is shown (320 MPa) and the calculated Stress Goal (80 MPa). By changing the Failure Definition to Stress Goal, the Stress Goal can be entered manually as well.
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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.
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Generative Design
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Changing the complexity setting:
By changing the Complexity value from 6 (left image below) to 22 (right image below) the resulting structure changes as well because the optimisation is carried out with a higher resolution. The emerging structure is more detailed and defined, but it also takes more time to get to this result. It depends on the model, the field of application and other non-quantifiable conditions which complexity setting is best suited for the part. We suggest starting with a low Complexity value for the first optimisations and after receiving the results consider whether a higher value is appropriate for the model.
You can see the results for the two Complexity settings and the deactivation of Keep Non-Design Spaces below.
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Reduce fixation points vs. Keep all Non-Design Spaces
To realize an optimisation with as much freedom as possible you should disable the Keep Non-Design Spaces function for the six fixations points as well as the constraint created with them. You can also create six separate constraints and deactivate all of them as well as the six Non-Design Spaces.
This way the algorithm works at its best and creates the most fitting results to the boundary conditions. With this approach it is possible to let the algorithm decide which and how many fixation points are necessary and needed for the applied boundary conditions. The reduction of fixation points almost always results in a more lightweight design by still taking into consideration the Safety Factor/Stress Goal of the structure.
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In another cases, it is important to keep defined fixation points and this can be realized with the activated Keep Non-Design Spaces function.
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The result in this example includes all six fixation points (Complexity 6). As shown in the left image the first optimisation reduced one of the fixation points and by choosing the presented function all of the six fixation points are included in the result.
Introducing Event Specific Safety Factors
To prioritize Events differently, Event Specific Safety Factor can be placed on single Events. It is also possible to prioritize only one Event. In this case the other event will take the global Safety Factor/Stress Goal into consideration for the optimisation.
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It can be seen clearly that the prioritization of the first Events changes the design. The geometry in the left picture shows more material in the structure because of the higher Safety Factor/ lower Stress Goal for the first Event. The enveloped stress for both Events clearly shows a gradation between front and back structure. You can also have a look at the stress distribution for each Event separately. By activating the Lock Spectrum Range, the stresses can be compared more easily.
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Step 7: Starting the optimisation and visualize 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.
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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.
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Step 8: Visualization of Stresses & Displacements
Inside the Post Processing the von Mises stress and the displacements are visible for all iterations
The Scale can be influenced individually
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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: Coming Soon!
You might also be interested in these tutorials:
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