Flatness control in the rolling of sheet metal – PLATFORM

Delivering metallurgical strips with increasing mechanical properties at the right price is one of the major stakes of the industry of metallurgy. For the transformation step, it induces an increasing difficulty to roll perfectly flat sheets and preventing from the occurrence of major defects due to buckling of strips. This high level of quality is required for downstream operations like stamping.
To support industrialisation of new high performance grades of aluminium and steel strips, we propose to develop innovative measurement methods and predictive models to assess flatness of rolled strips. The Project consists of two intrinsically coupled phases:

1) A significant improvement of the flatness measuring tools
i) for the residual stresses, by developing a new concept of flatness roll using Optical Fibre Sensors based on Fiber Bragg Gratings embedded under a roll surface, providing a high spatial resolution combined with an intrinsic compensation of thermal effects,
ii) for wave defects, a global measurement using laser scanners giving a high spatial resolution and allowing combined measurement of both latent and manifest shape

2) Development of predictive models for flatness. Two modelling approaches will be assessed:
i) an integrated approach where buckling is taken into account using a defined material law integrated in a 3D FE model for rolling
ii) a “hybrid” one using “Arlequin” methodology to couple the above FE model with a shell FE model.

Results from numerical models will be compared to experimental ones, allowing for a very fine validation of flatness (not available today) in particular at the very edges of the products, where significant stress gradients are observed. Project management will allow for a strong interaction of the complementary know-how of the seven highly skilled partners in their respective field.

The main project innovations are:

1) On the experimental side, the development of a residual stresses measurement method using high resolution Optical Fiber birefringent Bragg Gratings and the development of innovative rigs to study the relation between buckling and residual stresses in a controlled environment
2) Advanced numerical modelling to allow for the coupled analysis between roll gap mechanics and buckling instabilities occurrence at the exit of the roll gap.

These researches are highly strategic for the French industry in the field of rolling. Short term economical benefits are expected after the completion of this project. The associated aim is to guarantee the metallurgical plants competitiveness and sustain a high level of excellence on flatness control tools for rolling of thin gauge products. The projects results will contribute to shorten the ramp-up of new technical products from current and future market demands for wider, thinner and stronger products.