Modelling of a
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Screw Fixation
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A fixation can be applied to surfaces, edges and nodes
If a fixation is created for a volume the whole volume is considered fixed in the according directions. (Apex?) The fixation, considered during the optimization, can be compared to an RBE2 bracket. This means the nodes are stiff and cannot be deformed in any way.
Bilder
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Opportunity 1:
A screw fixation can be modelled by using a
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Nondesign space (red) around the screw
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as a shell. The Nondesign space is constrained using a clamped fixation.
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Opportunity 2:
To simulate the reality it is also possible to
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import/create an extra volume that’s representing the screw.
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The screw (blue) will be used as a fixation and is
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clamped. Additionally, there should be a
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Nondesign space around the screw (red), which
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is included in the design space
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but
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will not be used as a fixation in the
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optimisation model. This way the
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Nondesign space does not experience an artificial stiffening, which represents the reality much more accurately.
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Bilder vom Modellaufbau (Apex?)
Modelling of very smooth transitions between the design space and the fixed nondesign spaces:
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The transition between design and nondesign regions can be enhanced even further by adjusting the Youngs Modulus of the nondesign spaces. While reducing the Youngs Modulus by a factor of 10 the material is considered more pliant and therfore needs more material to absorb the stresses. This results in softer material transitions between the different materials and spaces
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Especially for parts where the fatigue strength plays a role, this method is good to strengthen the transitions betwenn the different spaces and thus extend the durability
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However, keep in mind that the screw becomes a part of the Design space, so you need the original Design space without the screw to create a good intersection with the optimisation results. Further information regarding the intersection here.