Problem Structural Analysis Singularity

[robbedalex]

Hello. I have a problem with singularity on Ansys Mechanical. Would someone help me? I'm trying to simulate two parts joined with a bayonet. on one part there is a pressure. I want to study the resistence of the bayonet. I do a structural analisys with frictionless contacts, and as the mesh is finer, the stress increase. Attached some images with a coarse mesh. The bottom part as a fixed support on the lower face. I need to use weak springs instead the model is underconstrained.

 

[robbedalex]

I know. But imagine that the body is like a cap with a pressure. there is not on this body constrains, but only contact and i put frictional contacts. The results is that there is singularity in the fixed body and also on the cap. The singularity disappear if i put a constrain in the cap. Probably i do some mistake, but i don't know where. I tried with symmetric and asymmetric contact, but nothing change

 

[L_K]

Could you post a section view of the deformation (with scale). Based on the previous pictures the parts
are not entirely symmetric? This might affect the magnitude and direction of resultant forces. Could you
also explain the physics more in detail. You might have to model the (possible) surroundings parts to get
a better boundary condition. For example fixed support is only a simplification of some real life condition.

 

[robbedalex]

here the deformation. the scale is 8. The model is non entirely simmetric. The contact between two bodies are in the bayonet.

 

[robbedalex]

here the fixed body deformation

 

[robbedalex]

here the "cap" deformation. This body has no constrain. So the program tell me that the model is underconstrained and i need week springs. In reality this body can't move because of bayonet. This body is in pressure

 

[karachun]

So why you do not use weak springs?

 

[robbedalex]

I use Thema because It is the only way to solve the model. I tried also without but it' s impossible.