Offline determination of profile and flatness by applying pseudo-steady-state elasto-viscoplastic simulation concepts in flat hot rolling
Sprache des Titels:
METEC InSteelCon 2011 Proceedings
For the prediction of material flow behavior of wide strips and plates in hot and cold rolling, highly sophis-ticated procedures are essential, which are able to couple the deformation of the rolled stock with the elastic response of the rolls. Especially for thin, wide strips, where the aspect ratio width over thickness is extremely unfavorable, the determination of profile transfer and flatness obviously leads to extremely high calculation times with commercial FEM-programs. Therefore, a tailor-made FEM-code for the efficient simulation of the elasto-viscoplastic material flow inside the roll gap was de-veloped. It is based on pseudo-steady-state and fully implicit stress-update approaches, where the incremental material objectivity is satisfied exactly. Special emphasis was put on the coupling of strip models with routines for the elastic roll stack deflection, which is a precondition to get reliable results concerning strip profile transfer and residual strain and stress distributions inside the strip. Such data allow the evaluation of strip-flatness based on buckling analysis and of the effectivity and adjustment ranges of profile and flat-ness actuators. The developed model is physically based with a robust numerical algorithm, the results of which were compared to data attained by commercial FEM-calculations and will be validated against practical data from industrial hot rolling mills. The model is well suited for systematic parameter studies to investigate flatness of strips and plates in more detail and to develop enhanced flatness criteria for thin hot and cold strips. Of particular interest is the dependence of the longitudinal stress and strain dis-tributions and of the corresponding specific rolling force-distribution across the strip width on the under-lying constitutive elasto-viscoplastic laws including work hardening and softening between consecutive passes.