Learning Forum

[brotherhood]

[SaiD]

Hi,nPivot error means that rigid body motion is occurring in your simulation i.e. the model is under-constrained. Have you applied enough boundary conditions to ensure there is no rigid body displacement or rigid body rotation in any direction?nIf you are not able to figure it out, please share some inline images showing the boundary conditions that you are applying.nnSain

[brotherhood]

i am happy with your response ! but can you elaborate more on those rigid body motion. i mean what rotation or movement should i restrict like restrict support its movement or what ? i am, beginner to ansys. thanksnn

[ciema]

Maybe this quote will help you to understand: Minimum constraints in any given structure are the displacement restraints that are need just to prevet rigid body motion. Any object in space has six independent rigid bodies of freedom consisting of three translations and three rotations. In finite element models one can choose judiciously the constraints (six or three) such that the structure has just the minimum constraints and a static solution becomes possible. If any of the applied displacement constraints are removed the structure becomes insufficiently constrained, and no static solution will be possible as the stifness matrix becomes singular.n

[brotherhood]

thanks for your kind response ! is there any way/tool in ansys which can show where or which part is not constrained?n

[ciema]

I prepared for you a small instruction:nArrayYou can check the exact node by clicking Right Mouse Button on backgroud in Mesh branch and then Select Mesh Nodes by ID and input number taken from Solver Output as presented in gif.nnif you know which node is falling you can identify which body is not constrained.n

[brotherhood]

Thanksn