A multi-scale experimental study on failure mechanisms in Dual Phase Steel

Unpredicted failure mechanisms in inhomogeneous materials, such as dual phase steels, leads to the necessity of investigating the interaction between the micro and macro scale phenomena. The current project deals with the interaction of different scales in dual phase steels through a multi-scale experimental study.

PhD Candidate: S. Maraghechi (Siavash)
Supervisor: dr.ir. J.P.M. Hoefnagels (Johan), dr.ir.  R.H.J. Peerlings (Ron)
Promoter: prof.dr.ir. M.G.D. Geers (Marc)
Project Financing: European Research Council (ERC)
Project Period: August 2014 - August 2018

Dual phase steels are considerably used in automotive industry due to their high strength as well as high ductility, which provides the possibility of design with higher crash safety and lower weight and consequently lower CO2 emissions. Unpredicted  failure mechanisms leads to the necessity of investigating the interaction between the micro scale phenomena, such as strain concentration and micro crack formation,  and the macro scale ones, such as localizations, considering the inhomogeneous microstructure of DP steels. These failures can be avoided by the optimization of the microstructures, e.g. to be less vulnerable to the damage mechanisms present. 

Conventional multi-scale methods can be good tools to model inhomogeneous materials, however the scale separation present in such methods, makes them incapable of well representing the material behavior in this case. This PhD project, through an experimental approach, intends to answer the question of what information should be passed between the scales, especially where the assumption of scale separation is not valid. A coupling between  the experimental study and the numerical model at each scale will be pursued in continue. Possibilities such as FEM Updating or digital Image correlation (DIC) will be investigated in detail.