Help for meshing of the sliding surface

Introduction

A coupled magneto-mechanical finite element model permits to study the kinematics of mobile regions of the computation domain simultaneously subjected to mechanical and magnetic forces.

For such models, where the mobile and fixed mechanical sets slide with respect to one another, the meshing of the device must respect certain constraints.

Sliding surface

Sliding is called the action of a mobile mechanical set, which is in a translation or rotation motion with respect to the fixed one. The interface between the two mobile and fixed mechanical sets is called sliding surface .

Non-conformity of meshing

To permit sliding, the mechanical sets (mobile or fixed) are separated by means of a « duplication» of the geometric and meshing entities.

Moreover, there is no remeshing of the fixed and mobile mechanical sets from one position to another.

Consequently, when the part moves, the nodes of the meshing elements located on one side and on the other side of the sliding surface are no longer necessarily face to face. This is called non-conformity of the mesh . This is illustrated in the figure below.

Example : non-conformity of meshing over the sliding surface for a rotation motion
Position 0°: The mesh nodes of the fixed and moving mechanical sets are face to face at the level of the sliding surface.	Position 35°: The mesh nodes of the fixed and moving mechanical sets are not face to face at the level of the sliding surface.

In this situation, a non-conforming mesh is authorized at the level of the sliding surface.

“Mesh connection” technique

The technique used in order to « connect the meshing » on one side and on the other of the sliding surface consists in an interpolation of the node values of the face to face surface elements by a linear combination with a view to ensure the continuity of the state variable.

Advice for mesh

It is therefore important that the size of the surface elements that are face to face should be approximately the same, irrespective of the amplitude of the displacement. This is illustrated in the figures below.

Example: sliding surface meshing for a rotation motion
Recommended mesh
Non recommended mesh (inhomogeneous density of nodes along the two circumferences)