Perfect Forming with Adaptive Meshing

by Paul-Louis George and Houman Borouchaki

The Japanese steel manufacturer Nippon Steel Corporation has selected BL2D, a bidimensional mesh generator software package, to better simulate and optimize thin sheet cut-outs and forming. BL2D was jointly developed by INRIA and UTT, the Troyes University of Technology.

BL2D is a robust, rapid, reliable and adaptive bidimensional mesh generator. Nippon Steel called on BL2D's talents to improve the simulation of thin sheet forming - destined above all for automotive markets - using methods such as stamping and orthogonal cutting, or machining techniques such as planning. Such simulations have been used for many years in industry for all part-forming operations, and employ finite element methods. This 'virtual forming' is used to measure the rapidity and quality of forming methods. This makes it possible to optimize the machines' real operating parameters, such as stamping or planning speed, or the impact of wear and tear on cutting matrices. All of these factors can have a major impact on the cost of industrial processes that involve the manufacture of millions of parts. Until now however, simulations were hindered by the quality of meshes that were implemented manually.

In the current version of BL2D-V2 (coupled with the computing software 'Abaqus'), the meshing is automatically adapted and is deformed by refining the meshes (equilateral triangles that are as regular as possible) at key stages of the simulation. Of interest to steel manufacturers is the ability to simulate sheet forming using a highly accurate mesh. Thanks to its automatic remeshing, this can adapt to areas in which the majority of constraints and deformations are found; for example, where the part is in contact with the tool or where it is most damaged. With BL2D, this operation has become almost transparent. Some 3000 remeshes are needed to simulate orthogonal cutting (a matrix cold-cuts the sheet by moving from top to bottom). In total, this requires only one hour from the two weeks required to complete the mechanical simulation computation. The result is improved quality and rapidity for the simulation.

Apart from this example, the strength of our automatic meshing solution lies in its generic nature. This unique approach has enabled the development team to address a large number of industrial problems in both solid mechanics (such as this particular case) and fluid mechanics. This explains why BL2D has been adopted by Alcatel and Snecma, and why BLSurf, a piece of surface-meshing software based on parametric patches that is well suited to solid and fluid mechanics, is used by Dassault Aviation, or more unexpectedly, by Lectra for a virtual clothing application.

Simulation of orthogonal cutting using standard Abaqus behaviour law. © Projet GAMMA / UTT

These licence loans provide the means by which new challenges can be tackled. For example, the collaboration with Nippon Steel should extend into the hitherto unexplored field of 3D simulation. Ten researchers are currently involved in one way or another, as well as three jointly supervised doctoral students. The agreement with Nippon Steel provides yet more proof of the quality of solutions developed as part of this collaboration, which is enhancing skills in mesh generation in INRIAs Gamma (Automatic Mesh Generation and Adaptation Methods) research team and in mechanical and thermal simulations at Lasmis..

Links:
http://www-rocq1.inria.fr/gamma/eng.php
http://www-lasmis.utt.fr/

Please contact:
Paul-Louis George
INRIA, France
Tel: +33 1 39 63 56 03
E-mail: Paul-Louis.Georgeinria.fr