Strain rate effects in a high strength dual phase steel
(English)Manuscript (preprint) (Other academic)
This work focuses on strain rate effects in a high strength dual phase steel, DP600. Attention is given to the mathematical formulation of the strain rate sensitivity, and to its influence on the strain at localisation. Both an experimental and a numerical study are presented. In the experimental study, uniaxial and notched tensile tests, as well as shear tests were conducted at various loading rates. Furthermore, strain rate jump tests were conducted in order to further investigate the strain rate sensitivity. It is clearly shown that the material has a positive strain rate sensitivity, and that a multiplicative contribution to the flow stress is a better approximation than an additive one. A material model including a non-linear plastic hardening, a high exponent yield surface, a thermal softening effect and a variety of multiplicative strain rate sensitivity functions is presented and calibrated. This material model is used in finite element simulations of the mechanical tests. The predicted results are in good agreement with the experimental findings. The stabilising effect of the strain rate sensitivity is shown to be important whenever strain localisation becomes an issue in finite element simulations. It is also shown that the strain rate sensitivity index depends on the plastic strain rate, which thus is the case also for the stabilising effect. From a supplementary study, it is concluded that the assumed thermal softening will affect the onset of localisation.
Strain rate, dual phase steel, plastic instability, notched tensile test, shear test
Engineering and Technology
IdentifiersURN: urn:nbn:se:liu:diva-81921OAI: oai:DiVA.org:liu-81921DiVA: diva2:556515