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Goal of this tutorial
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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 GD-Bracket the already prepared Design Space was imported.
Open the Optimization Tools to select the imported Geometry as the Design Space.
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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.
To apply the forces the Force Moment Tool from the Loads & Boundary Condition Tools is needed. By disabling the Flash (selection of the execution mode for the tool) on the top left corner of the Tool, multiple faces can be selected simultaneously. Select the Faces as shown in the pictures below for each load.
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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.
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All surfaces on which a boundary condition is applied can be selected directly as an interface with the “Select Faces from Loads and Boundary Conditions” button. The Boundary Condition surfaces will be highlighted and can be selected/deselected. With “Apply” the Non-Design Space Thickness, Machining Allowance and if available Offset Distance values will be applied to the selected surfaces.
In this case a 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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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 Eventscan be changed by adding/deleting Eventsto the GD Scenario. The assignment of the boundary conditions to the Eventscan 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 Eventindividually.
Event 1: Force-Moment 1, Force-Moment 2, Constraint 1, Constraint 2, Constraint 3, Constraint 4, Constraint 5 and Constraint 6
Event 2: Force-Moment 2, Force-Moment 3, Constraint 1, Constraint 2, Constraint 3, Constraint 4, Constraint 5 and Constraint 6
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The optimisation parameters are selected in the Studies Area as well.
Manufacturing Method: Generic AM
Failure Criteria: Von Mises
Strut Density: Medium
Shape Quality: Balanced
Keep Non-Design Spaces: All Constraints and Interfaces 5-10 are deactivated
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Don’t forget to save the project!
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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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.
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.
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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 and for every Event
The Scale can be influenced individually
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The whole MSC Apex Generative Design project with all results can be downloaded here:
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How the Complexity, Keep-Non-Design Spaces function and Event Specific Safety Factors influence the design is covered in the second part of the Tutorial: Generative Design - GD-Bracket Part 2
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