stress convergence
stress convergence
(OP)
Hello,
I am doing a non linear analysis, displacement controlled.
i am able to get a good residual force convergence & displacement converegnce.
When i have a visual look on the elements, the displacements are well distributed among all elements
However when i check the stresses,stresses are concentrated on few points( like a stress singularity)
although this is not be the real situation. Its a large symmetric structure and stress need to distributed.
Do anybody have a solution to arrive at stress convergence ?





RE: stress convergence
"non linear analysis" - is too vague, what kind of NL , material, large displacement , contact ....?
You are applying displacements, how? To a surface or individual nodes? How is the model restained? Again at a surface or individual nodes?
The normal means to get stress convergence is to increase mesh density, but with stress spikes in your results this is unlikely to help. You need to remove the cause of the spikes first.
RE: stress convergence
corus
RE: stress convergence
Let me give some more information.
its an incompressible FEM simulation using rigid plastic formulation.So its a very unstable simulation.
it is to simulate pressing of glue (glue is modelled as non newtonian fluid & rigid plastic formulation).
The glue is pressed against a large struture with a heavy load. Target is to compute the displacements and stresses on the structure which is still elastic
displacements and loads are applied on the nodes and the model is restrained at nodes only.
My problem is i find stress concentration on this large structure which is not realistic.
Can anyone give me ideas to overcome this problem.
RE: stress convergence
As corus said point loads and restraints create singularities, therefore consider applying the "heavy load" as a distributed pressure on the large structure and forget about the glue. Ideally you should be able to apply pressure loads where the supports are to balance this load out and then use minimal supports, this will eliminate all your singularities.
RE: stress convergence
Is my Crystal Ball working here?
TOP
CSWP
BSSE
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RE: stress convergence
RE: stress convergence
corus
RE: stress convergence
Out of curiosity, is the displacement anywhere in the model a significant portion of the thickness of the element? Particularly where these peaks occur?
If you plot stresses along a continuous edge where these spike occur is it a smooth plot or jagged?
TOP
CSWP
BSSE
www.engtran.com
www.niswug.org
"Node news is good news."
RE: stress convergence
your crystallball is almost there. thats what i am trying to do.i trying to evaluate the stresses on a structure where a heavy load is bonded onto it. i am using a few layers of solid to model the glue and will have a pressed glue at end of simulation but i am not using higher order element but normal(linear) solid elements.my stresses are not at the bondling line. quite far away from the bonding line. but anyway i will follow yur advice and look at the displacment plot and let you know.
gwolf2, i may not be able to give you a picture becoz of confidential work.but i am free to discuss the topic.
corus,
i cannot discard the glue. apart from stress and displacement, i need to evaluate the force required to press the glue.since the bonding is a robot operation, the forces are also of interest.
but yes if i need to evaluate only stress, then i can do it as worst case scenario and neglect the glue.
RE: stress convergence
TOP
CSWP
BSSE
www.engtran.com
www.niswug.org
"Node news is good news."