displacement constraints

[ice_man]

Hey guys:
I have a chassis that twists, and i know the approximate displacement, but what i need to find out is the forces, required to cause that dispacement. Is there a way in Mechanica to do that?

TIA

 

[deepakbhat_nie]

Hi,


Create a parameter for load and include the load parameter in the Design Parameters.Run a static analysis for any load and then run the sensitivity or optimization analysis to find the load for a specified deflection.


Hope it helps.


Regards,


Deepak Bhat

 

[rmckinley]

Just do an enforced displacement: Set up a constraint on the surface which moves by the known amount and applythat specific translation value in your constraint. Then, create measures toreport the reaction forces in the constraints. Run the analysis as normal (you will haveno forces in your analysis - only constraints). This method will take the same time as a regular spa -- no need to run an optimization.


Hope this helps.

 

[KurtStark]

You can do a static analysis with any force F0.
You get the corresponding deflection D0.
Because Pro/Mechanica calculates linear, you can calculate the required force F to get your deflection D:


F =F0 * D / D0

 

[CaptnPea]

Just do an enforced displacement: Set up a constraint on the surface which moves by the known amount and applythat specific translation value in your constraint.

Carefull, tried to use this for snap fit designs in the past, it sort of works, but, has bigtime limitations. For example if you load a cantiliver beam that is lying in the horizontal plane, with a vertical force, the displacement at the end is not completely in the vertical direction (the point moves toward the supported end). If you enforce a displacement you essencially add anouther tensile component to your load.

 

[rmckinley]

Just do an enforced displacement: Set up a constraint on the surface which moves by the known amount and applythat specific translation value in your constraint.

Carefull, tried to use this for snap fit designs in the past, it sort of works, but, has bigtime limitations. For example if you load a cantiliver beam that is lying in the horizontal plane, with a vertical force, the displacement at the end is not completely in the vertical direction (the point moves toward the supported end). If you enforce a displacement you essencially add anouther tensile component to your load.

This is true. I usually use it in contact analyses, though -- in which case the odd way that the displaced constraint affects the geometry is negated or ignored because it is not in the area of concern. I would only recommend the technique for small displacements relative to the geometry.

 

[mecbat]

Also try putting measures at the point to test Force. Mechanica will show Force only in the Analysis Run Tabel, at the end of run. You have to have forced displacement to get force measure though...