Learning Forum

[peteroznewman]

Hello Gianluca,

That is a good summary. Yes, for threaded holes, scope the remote point to the face of the threaded hole.

One advantage to using a Beam compared with a Joint is the ease of obtaining correct output. The beam has a line that defines the axial direction and the shear directions are correctly labeled. Forces in Joints are labeled with X, Y, Z coordinate directions, but you have to know which axis is axial and which axes are shear directions.

Another advantage to using a Beam compared with a Joint is that you can apply a Preload force, though you must also define a frictional contact between the faces being clamped together by the fastener.

One difference between a Beam connection (where the beam is automatically created) and a Line body meshed with beam elements is if you have a temperature load, CTE effects such as the beam getting longer or shorter with temperature changes will not be calculated on the Beam connection, but it will be calculated on the beam elements on a Line body.

A significant defect in Ansys compared to Nastran is in the behavior of the spider from the Remote Point to the scoped nodes on the face or edge of the part when a temperature load is applied. In Ansys, for Behavior = Rigid, there is no ability to define a CTE value for the spider. In Nastran, when creating an RBE2 element, you can define the CTE for the spider. This means that when the CTE is the same for the body and the RBE2 element, there can be a stress free thermal expansion of that connection in Nastran. In Ansys, Remote Points will create stress around the hole under a temperature load.

I hoped that changing the Remote Point to Behavior = Deformable would deliver a stress free result under a temperature load, but I was disappointed to see stress on the edge of the hole when I tried that.

The workaround in Ansys to avoid stress around the hole under a temperature load is to create the spider using beam elements meshed on line bodies, which is an unacceptable amount of work. It is less work to put a solid model of the fastener and use Bonded Contact for the bolt head and threads to obtain a stress free result under a temperature load when all the CTE values are equal.