I am working on additive manufacturing simulation and at last step I need to remove all constraints and apply spring to avoid rigid body motion. I have applied spring through interaction module but it allow rigid body motion. I am looking for a appropriate solution for spring boundary condition after unclamp the part. Need your kind guidance Thank You
Did you apply the appropriate restraints to the 2nd node of each spring element?
What type of analysis are you carrying out that poses problems with rigid body motion? Are you imposing loads which could explain the large displacement, given the spring stiffness you chose?
I am doing coupled temp-displacement analysis in additive manufacturing all of my dimensions are in mm and chose 1 N/mm stiffness but it allows rigid body motion
So thermal loads only. At the end of Step 4 just before removing the clamped BC, do you observe significant stresses at the clamped boundary? Could it be that the thermal loading and additive manufacturing builds up a stress state within the model, and that upon release of the BC these stresses lead to a secondary deformation? I've had similar issues, which were solved by adopting more realistic BCs instead of the perfectly clamped state. Perhaps post a sketch of your real model as well as a picture of your FEA representation.
I have this boundary condition before unclamp step. I want to add spring at the four corner of base-plate to avoid rigid body motion by removing bottom-surface pinned boundary condition. I tried through interaction-special-spring/dash-pot but it allows rigid body motion and analysis aborted. Could you please guide how to apply spring boundary condition in unclamp step to realize actual conditions.thank you
Your problem is the pinned bottom surface which constrains the material from lateral expansion / contraction. You need the following BCs:
- bottom surface UZ = 0
- bottom corners 1 and 2 UX = 0
- bottom corners 2 and 3 UY = 0
That will mimic a perfectly sliding BC, but will prevent warping of the material at the edges due to UZ = 0.
A more accurate way would be to activate gravity and use the bottom surface as the master surface of a friction contact to a fully pinned ground surface. That will be the bees' knees' in terms of modelling accuracy.
Not yet actually your proposed boundary condition is not like spring. I am still in the middle of nowhere
What exactly do you want to analyse? An overview of your steps and the type of loads and analysis will be helpful to understand the problem better.
I am doing coupled temp-displacement analysis for electron beam cladding to analyze residual stress and distortion. I have five steps Heat source moves in 1st and 3rd step on cladding layers to heat the material up to melting point 2 and 4 step is for cooling the cladding and 5th step is un clamp step to remove cladding base from table. I have to remove all mechanical boundary conditions in un clamp step and put springs at the corners of base plate during this step to avoid rigid body motion. Hope you got my point. Figure in above comment shows base plate boundary condition before unclamp
At the end of Step 4, check the forces and moments transferred into your boundary conditions. If they are non-zero, your model has stored potential energy which causes the sudden deflection upon removel of the BC in step 5. If this is the case, you won't be able to apply truely weak springs. The question you have to ask yourself is this - is the workpiece truely clamped during steps 1 to 4? From what you are telling, the material rests on a flat plate during additive manufacturing - hence my suggestions for more appropriate BCs for steps 1 to 4.
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