Wednesday, November 25, 2015

FEA : Solving element interference in mesh model | Ansys, Hypermesh, Solidworks, Nastran NX

To solve Element Interference

Interference Check tools are used to check the mesh model for element interference, the Element Interference Result/Fix form allows us to view, manipulate, and try to solve the areas where interference occurs.

The tools on the Element Interference Result/Fix form should only be used to repair regions where the amount of interference is relatively small, relative to the elements' size and thickness.
Usually, the Element Interference Result/Fix form does not allow we to fix areas of self-intersection within a single component.

The Element Interference Result/Fix form divides the model into separate "problem areas" that represent the regions where interference occurs. Generally the pre-processor software designates these regions by finding each interfering element and then clustering an interconnected set of elements that interfere with each other. Because resolving interference on a large model can be a difficult and iterative process, working with one problem area at a time can help we manage the scope of the problem. Each problem area is comprised of multiple components.

To actually repair the interference between components, the pre-processor moves the nodes on the interfering elements as well as on the elements surrounding them based on a percentage of the elements' thickness. Different options on the Element Interference Result/Fix form allow we to constrain either specific nodes or entire components to control this movement. If we're repairing the interference on a model that contains associated geometry, the software maintains the geometry association.

Process of Interference Repair

The following is a general process to guide we through the basic steps of identifying and repairing element-based interference:

  1. Use Interference Check to check the model for interference. Use the Interference Check Options form to specify options for performing the check.
  2. If the software detects interfering elements, pick Result/Fix Form from the right hand menu to open the Element Interference Result/Fix form.
  3. Use the different display and grouping icons at the top of the form to examine the different problem areas and determine in which order we're going to try to address them.
  4. Use the constraint icons at the bottom of the form to view the existing nodal constraints on each component and modify them if necessary.
  5. When we are satisfied with the nodal constraints,we can pick Fix Interference to repair selected components.
  6. Select OK to accept the changes to mesh model, or Select Undo to undo the interference repairs between selected components.

Nodal Movement during Interference Repairs

With Fix Interference, the software moves the nodes in the direction of their constraints. In order to prevent the drastic changes in curvature that could by caused by moving just the nodes on the interfering elements, the software also moves nodes on four surrounding rings of elements.
Interference Repairs Performed in a Series of Iterations

The pre-processor would move the nodes on the rings of elements in a series of up to ten iterations. After we use Fix Interference, the software reports the number of iterations performed in the List region. If the software is unable to repair the interference in ten iterations, we can pick Re Iterate from the right hand menu to have the software perform up to ten additional iterations.