Constitutive modelling for complex loading in metal forming processes
The project aims were to investigate experimentally and by mathematical models the effect of loading path on microstructural evolution and flow stress behaviour and to validate and apply the models in laboratory and industrial hot rolling processes. These aims have been achieved through partner co-operation in sharing expertise and experimental resources for model development and validation. Experimental tension, compression and torsion tests on a range of steel qualities have shown that mechanical loading paths involving abrupt changes in strain, strain rate, strain-reversal, multiple hits in parallel or perpendicular directions can retard recrystallisation and change the flow stress behaviour through a Bauschinger effect, a lag behind the behaviour defined by a mechanical equation of state and the appearance of a plateau. The paths can also give rise, in the case of ferrite, to larger cells, and, for strain reversal, coarser grains and more low-angle boundaries. In contrast, effects of thermal history have been found to be minimal: 1. The difference between the flow stress after a temperature increase and that for isothermal compression at the higher temperature is small. 2. In rolling, the interpass temperature determines the softening much more than the path taken to attain that temperature. In laboratory trials, kinematic (unlike thermal) effects on structural evolution and flow stress were marginal, viz. localised retardation of recrystallisation following interpass stock radiation and slightly increased grain size in high speed rod rolling. Numerical and empirical constitutive models based on underlying mechanisms related to dislocation dynamics, softening, etc. have been formulated by all partners for predicting the effect of the above loading paths on flow stress behaviour, fraction recrystallised, etc. and have been validated in experimental tests and industrial rolling trials.
Bibliographic Reference: EUR 22011 EN (2006), 440 pp. Euro: 45
Availability: Katalogue Number: KI-NA-22011-EN-S The paper version can be ordered online and the PDF version downloaded at: http://bookshop.europa.eu
ISBN: ISBN: 92-79-01112-X
Record Number: 200618705 / Last updated on: 2006-09-14
Original language: en
Available languages: en