I’m importing a mesh (no geometry, only nodes and elements) of a model that contains bolts. The bolts are composed by hexahedral elements.
I need to apply pre-tension loads to the bolts. I can’t find a way to select the cross-sectional surface at the center to properly apply the pre-tension load in the longitudinal direction of the bolt.
I’ve tried without success:
Bolts with shared nodes at the center, that’s a complete connected set of elements defining the bolts.
Bolts split into two connected sets of elements, without shared nodes at the center.
Is there any way to apply a pre-tension load in this case?
In what software did you create the mesh and in what format was it imported ? Perhaps you could just create a layer of prismatic elements there and even prepare a surface definition (especially if it’s INP from Gmsh). Then it would be just a matter of adding proper keywords in the editor.
Normally, you need 2 parts for each bolt, then you make a compound and select the surface between the segments for bolt load definition. The thing is that since individual elements can’t be hidden in PrePoMax, parts are needed to select the internal surface. One trick helping in some cases is to convert element sets to parts.
This is what i do when i want to add bolts to a model. When you have some templates, no cad system is necessary to add bolts with individual lenght (thanks to the “thicken shell mesh” feature):
After converting the element sets to parts, the intermediate step “Find model edges by angle” is sometimes necessary, otherwise it can happen that the individual surfaces for BCs will not be recognized correctly during selection.
I’m creating the mesh in python with some custom functions, and exporting to inp with meshio. The approach of defining a surface in the inp file is interesting.
Does this surface need to be an exterior surface of the compound, or any surface works? If any surface works, I could build a bolt with only one set of elements (non split into two), create a surface with the nodes of a cross-section at the center of the bolt length, and apply the pre-tension force to that surface, is that correct?
Converting element sets to parts works perfectly! Now I can apply the pre-tension
It can be pretty much any surface in the cross-section of the bolt shank but the following rules apply:
Notice that in the volumetric case the surface must be defined by element faces, it cannot be defined by nodes. Furthermore, the user should make sure that
the surface does not contain edges or vertices of elements which do not have a face in common with the surface. Transgression of this rule will lead to unrealistic stress concentrations.
the surface is not adjacent to quadratic elements the faces of which belong to a contact surface.
Because of the first point, in PrePoMax we create a layer of prismatic (wedge) elements.
