Friday, November 27, 2015

FEA: Dragging Nodes in FEA mesh (thin shell 2D elements) | Ansys | Hypermesh | Solidworks

To meet the quality criteria like threshold angles, Jacobian ratio, aspect ratio, warp, distortion etc, we can manually drag the nodes of the elements.

Therefore, Dragging a Node can interactively re-position nodes associated with 2D type elements, such as thin shell, plane strain, plane stress, axis symmetric solid, plate, and membrane.

When you drag a node, it maintains associativity with the surrounding elements and the underlying geometry. As you drag the node, the software previews how the elements associated with the node will be affected.

In general, we can only drag one node at a time. However, any mid-nodes adjacent to the selected node will also move. If you drag a node in a mesh that contains higher order elements, such as parabolic or cubic elements, the pre processor software (Hypermesh, Ansys, Solidworks) translates the mid-nodes to preserve their initial characteristics.

Requirements for Dragging a Node on Geometry

If a node is constrained to:
  • an edge or a wireframe curve, you can reposition the node along that edge or curve.
  • a surface, you can reposition the node on that surface.
  • a section, you can reposition the node on any surface within that section.
Note: You can't drag a node past the edge of a hole or fillet.

You can't use Drag (Node) to re-position:
  • nodes on anchor nodes
  • nodes associated with vertices, connectors, or centerpoints
  • nodes associated with geometry-based other elements (such as a spring, rigid bar, or lumped mass)
  • nodes associated with point-based geometric boundary conditions

Dragging a Node on Geometry

  1. Pick the node you want to reposition.
  2. Move the cursor to drag the node. As you move the mouse, the software updates all adjacent element edges in real time.
  3. Use mosue buttons to drop the node in its new location,

Requirements for Dragging a Node Not Associated with Geometry

Drag (Node) also lets you drag nodes in FE models that don't contain any geometry, such as those FE models created with the bottom up meshing technique. Before you can reposition a node that isn't associated with geometry, you must first pick the plane in which you want to drag the node. The default drag plane is the average of the local normals of the adjacent elements.
Dragging a Node Not Associated with Geometry
  • Pick the node to reposition.
  • Pick the plane in which you want to drag the node.
  • Move the mouse to drag the node or use the mouse button options 
  • Use mouse buttons to place the node.

We can also pick Drag (Node) from the Element Quality Checks form to improve particular aspects of element quality. For example, if a quality check reveals a high amount of skew in a particular region, we can try repositioning nodes in that area to reduce skew.