Accurate Numerical Methods – Key for Accurate Virtual Prototyping

Accurate contact permanently prohibits the nodes of the blank sheet from any penetration of the volume of the element of the tool during a calculation. The nodes are kept exactly at the surface of the element owing to the contact forces being precisely calculated.

Today, all explicit simulations in PAM-STAMP are carried out with accurate contact and high quality numerical settings, no matter if in the feasibility or validation stage. Accurate contact is applied to huge simulation models with one million or more elements. At the same time, the explicit method with many short time steps allows for the precise integration of the material history in the drawing phase. It is not possible to run accurate contact with many short time steps on large models with implicit solutions because it would be too time consuming.

Working with accurate contact, short time steps to integrate the material law accurately and from the beginning accurate numerical settings has several advantages:

• There is no risk of finding - late and thus costly - issues like cracks or wrinkles in the validation phase, just because of different (contact or numerical) settings in the feasibility stage. Accurate contact in all simulation stages and providing an accurate representation of the tool topology and tool mesh from the beginning helps to avoid this problem, which otherwise can take a lot of time to compensate for the encountered issues.
• The accurate computation of plasticity and residual stresses after forming is guaranteed, which is the pre-condition of accurate springback.
  • This accurate springback is the best basis for predictive distortion compensation on the forming side of life or in the final assembly process (hot and cold joining)
  • Accurate springback means accurate residual stresses and plastic history – which are the required basis for predictive performance simulations
• The ironing effect can be taken into account
• The press force is predicted precisely
• Accurate contact and ironing are the basis for accurate die spotting – which can save a lot of time especially in the development of a press hardening die

Accurate contact is relatively computational intensive. However, with the new triple speed mode in PAM-STAMP (referred to later on in this document), simulations with accurate numerical settings are now also possible even in the earliest stage of the project. Consequently, any numerical compromises in the feasibility stage can now be discarded.