Modelling Springback of Bent Hydroformed Dual- -

? Is a national laboratory within Department of Natural Resources Canada

– Relocated to Hamilton, Ontario in 2010

? Manages a national user facility for materials and manufacturing

– Pilot-scale processing facilities

– Performance assessment

– Microstructural characterization

– Computational engineering

? Has facilities in Hamilton, Ontario and Calgary, Alberta

? Has a mandate: To improve the competitive, social and environmental performance of Canadian industries that add value to minerals and metals

? Has programs in materials for transportation, pipelines, nuclear power and defense applications

Lightweighting of auto-body structures is a key objective in the materials for transportation program

? Fuel economy regulations of 54.5 mpUSg (eq. GHG) in 2025

? Significant lightweighting >30% by 2025

? One strategy is use of advanced high-strength steels and dual phase steels

? High strength, lower thickness, while retaining crash performance

? Seam-welded, dual-phase steel tubes are often bent and hydroformed

? Springback and its prediction is a key item in deployment of seam-welded dual phase tubes – problem introduced to Canmet by Variform

CanmetMATERIALS initiated a project on springback modeling of DP980 tubes

? Partners – Vari-Form and Arcerlor Mittal Tubular Products

? Funded by OERD (Office of Energy Research and Development), Department of Natural Resources Canada

? Initial proposal was to test tube material directly - can ignore work hardening - owing to tubing – 50-mm diameter, 2-mm thick DP980

? Initial proposal focused on material response and FE modeling

– kinematic hardening

Coiling of sheet and tube forming introduce residual stresses-

? Sheet and tube yield variation as high as ~50 MPa

? Residual stress at weld (ignored in current project)

? Need to use residual stress as initial condition is FE simulations

? Three-fold problem

? Initial hardening in tube

? Residual stresses in tube

? Material behavior

To model springback in DP980 tubes – starting FE mesh for tube must account for initial state owing to tube forming and material model must describe sheet material response

? Abaqus/Explicit + springback step in Abaqus/standard

? User-subroutine VDISP to “weld” edges

? Get residual stress and also work hardening

Cutting plane algorithm in Computational Inelasticity by Simo and Hughes

 Shell algorithm using the secant method (Benson and Schoenfeld)