4 Replies Latest reply on Jun 14, 2013 5:26 PM by Jared Conway

    constraints and contact

    Emil Tietje
    Emil Tietje Jun 14, 2013 12:02 PM

      Recently, I finished a FEA model for a pressure vessel.  the solid model was developed by another engineer.  it had one very high stress location in an unexpected location.  the constraints he use to locate the parts i found unusual.  The pressure vessel had a bolt flat end cap on one end a weld head on the other.  The flat end cap was not constrained using the features in the welded housing.  The end cap was constrained using a part that would normally be installed later in the assembly process.  I would think it not make a difference.  The FEA modeler locates all the parts using connections, etc.  Has anyone an issue between constrains and connection causing high stress location?

        • Re: constraints and contact
          Jared Conway
          Jared Conway Jun 14, 2013 1:53 PM (in response to Emil Tietje)

          hi emil, a picture of the setup and the model might be helpful

           

          regarding connections and constraints, remember they are idealized. they act as infinitely rigid in most cases which can develop high stresses around them. if your interest is right in that area, you need to add the next component in your assembly. there are many conversations about this on the forum. look for stress singularity or stress concentrations.

            • Re: constraints and contact
              Emil Tietje
              Emil Tietje Jun 14, 2013 3:29 PM (in response to Jared Conway)

              the high stress is in an area of low interest.  other areas of the end cap have high stress as expected. my real interest is whether the constraints in the model and effect the contact definitions in the fea model.  i would think there the constraints in the have no effect on the contact definitions.

                • Re: constraints and contact
                  Jared Conway
                  Jared Conway Jun 14, 2013 3:36 PM (in response to Emil Tietje)

                  i'm not following your question.

                   

                  can you post a picture?

                   

                  can you upload a sample model that shows the question?

                   

                  can you elaborate on a specific example of what kind of constraint and what type of contact/connection?

                    • Re: constraints and contact
                      Jared Conway
                      Jared Conway Jun 14, 2013 5:26 PM (in response to Jared Conway)

                      Connected with Emil, his question was whether the mates applied in the simulation. The answer is nope. Only restraints and contact/connecctions in solidworks simulation hold things together.

                       

                      His high stress area we think is either a solver problem or a bad element. He's going to improve the mesh and see if it gets better. If the displacements level out, it could just be a bad element.