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Raphael R

Displacement constraints for shape optimization

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Hi,

 

After doing the HyperMesh morphing tutorials and the Optistruct shape optimization tutorials, I created a shape optimization file on my own.

It consists of a cylindrical cantilever which is loaded sideways at the free end. The goal is to find an optimized cross section.

 

The inner part remains unchanged, for the outer part (connected using equivalence) three different shapes are defined (elliptical morphing along x, along y and circular stretching).
When minimizing the volume of the cantilever while limiting the stress in z-direction, the expected elliptical cross section results and the optimization constraint is fulfilled:

 

Shape_opt_stress_constr.png

 

Shape_opt_stress_constr.hm

 

When limiting the displacement in load direction at the end of the cantilever, the cross section shrinks to a circle of minimum diameter and the displacement is much larger than the specified 0.15.

 

Shape_opt_disp_constr.png

 

Shape_opt_disp_constr.hm

 

Isn't it possible to use displacement dconstraints for shape optimization? The solver (Optistruct) doesn't recognise the constraint violation and minimizes the volume to the extreme, leading to very high displacements.

 

Shape_opt_disp_constr_solver.png

 

Thanks in advance for any inputs.

 

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The displacement constraint is defined for node 2 of your model, but node 2 is a temp node that is not attached to any structure.  Since this node never moves the optimizer can take all design variables to their minimum values and still meet the constraint.  I think you want the constraint to apply to node 962 of the model.

 

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3 hours ago, KevinEldridge said:

The displacement constraint is defined for node 2 of your model, but node 2 is a temp node that is not attached to any structure.  Since this node never moves the optimizer can take all design variables to their minimum values and still meet the constraint.  I think you want the constraint to apply to node 962 of the model.

 

Thanks for your input, the model now works as desired.

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