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Goal of this tutorial
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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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Name | Force/Moment/Pressure/Gravity | Direction (depending on local coordinate system) | Value in N/Nmm |
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Force - Moment 3 | Force on faces | x (local coordinate system 1; proposed center is point of application) | 7000 |
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Six Constraints at the bottom of the structure is are created:
To prevent a warning regarding the interfaces, create six single Constraints?
Name | Direction |
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Constraint 1 | x, y, z (=0) |
Constraint 2 | x, y, z (=0) |
Constraint 3 | x, y, z (=0) |
Constraint 4 | x, y, z (=0) |
Constraint 5 | x, y, z (=0) |
Constraint 6 | x, y, z (=0) |
Under Displacement Constraints a “clamped” constraint can be chosen, which locks translations in all three directions. On the left side of the Tool the relevant geometry choice can be selected. In this case the inner surfaces are selected to attach the constraints as shown in the picture below.
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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 “Interface Thickness”(Non-Design Space) 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 are created for the force application and fixation regions. Therefore, an Interface 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.
Step 5: Definition of load cases
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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.
Event1Event 1: Force-Moment 1, Force-Moment 2, Constraint 1Event2, Constraint 2, Constraint 3, Constraint 4, Constraint 5 and Constraint 6
Event 2: Force-Moment 2, Force-Moment 3, Constraint 1
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, Constraint 2, Constraint 3, Constraint 4, Constraint 5 and Constraint 6
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Step 6: Definition of optimisation parameters and Generative Design Settings
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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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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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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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