A PhD vacancy is available in the Mechanics of Materials group led by Prof. Marc Geers (www.tue.nl/mechmat). The candidate will be co-supervised by Dr. Ron Peerlings, Dr. Johan Hoefnagels and Prof. Marc Geers. This PhD project forms a part of the 2-PhD UNFAIL project, in which Materials innovation institute (M2i), Tata Steel Europe,  and several academic partners collaborate to enable development of new generations of advanced materials for e.g. the automotive industry.

 

Project: Unraveling the effect of microstructure statistics on failure of multi-phase steels (UNFAIL)

Advanced multiphase alloys, such as advanced high-strength steels, have the potential to largely replace conventional forming alloys. This will allow designers to engineer products, e.g. cars, to be lightweight and energy-efficient, but nevertheless safer. A limitation of current generations of such materials, however, is their limited ductility. During forming, they tend to fracture unpredictably, at strains which are significantly smaller than those reached with conventional materials. The producers of such materials are able to influence the material's microstructure - or at least its statistics - by, e.g., heat treatments. They however have a limited understanding of how the (statistics of the) microstructure affects the strength and ductility of these advanced alloys. The present project aims to develop precisely this insight, following a systematic experimental-modeling effort at three levels of detail:

1. Nano-tensile tests on specimens containing specific features of the microstructure (e.g. a single grain of a single phase, or a phase boundary between two phases) are modeled in detail by crystal plasticity in order to identify the relevant unit (damage) processes and calibrate the model parameters.
2. Tensile tests on thin sheets reveal the interaction of the phases and the competition between the unit processes. The microstructures and failure processes are fully statistically characterized. The real microstructures are analyzed using the lower-scale crystal plasticity modeling. Additional artificial microstructures will be generated according to the statistics of the real ones - or systematically deviating from these statistics - allowing to draw rigorous conclusions.
3. Our findings based on the small-scale experiments and modeling are confronted with existing experimental data on the level of the (commercial) sheet material. Fracture criteria and/or damage models are formulated, which can be directly implemented in, e.g., forming analyses at this level.

The project uses a commercial grade Dual Phase steel (DP600) as a carrier - ensuring a direct relevance of the insights gained and models constructed. But the work will also implicate a much wider class of advanced multiphase materials.

 

PhD vacancy with a focus on numerical simulations at the micro-, meso-, and macro-scale.

This PhD vacancy concerns the numerical part of the project to unravel how the statistics of phase distribution and phase properties govern the strength and ductility of advanced multiphase alloys. As described above, this includes (i) detailed crystal plasticity simulations to unravel the mechanics of the fundamental damage processes at the smallest scale, (ii) meso-scale crystal plasticity simulations including mechanism-based microstructural damage models of real microstructures as well as statistical variations thereof, and (iii) numerical modeling and simulation of polycrystals in three dimensions to predict failure criteria such as forming and fracture limit diagrams.

 

Research group Mechanics of Materials

The Mechanics of Materials group (www.tue.nl/mechmat) is globally recognized for its research on experimental analysis, theoretical understanding and predictive modelling of a range of phenomena in engineering materials at different length scales, which emerge from the physics and the mechanics of the underlying multi-phase microstructure. A systematic and integrated numerical-experimental approach is generally adopted for this purpose. This focus is closely related to intrinsic material properties (multi-scale plasticity in advanced steels, interfacial properties in laminates, thermo-mechanical fatigue in cylinder heads, etc.), the application of materials in microsystems (i.e. multi-phase functional materials, MEMS, stretchable electronics, etc.) and various systems and processes involving mechanically complex interfaces (e.g. in Systems in Package, flexible displays, electronic textiles).

The group has a unique research infrastructure, both from an experimental and computational perspective. The Multi-Scale Lab allows for quantitative in-situ microscopic measurements during deformation and mechanical characterization within the range of 10-9-10-2 m. In terms of computer facilities, several multiprocessor-multi-core computer clusters are available, as well as a broad spectrum of in-house and commercial software.

Talented, enthusiastic candidates with excellent analytical and communication skills and high grades are encouraged to apply. A MSc degree (or equivalent) in Mechanical Engineering, Applied Mathematics, Physics or a related discipline is required, as is a strong background in continuum mechanics (tensor calculus) and computational methods. Experience in micro-mechanics, non-linear material modelling, finite element techniques, and crystal plasticity are of benefit.

We offer:

• A challenging job at a dynamic and ambitious university and in a world-class team,
• An appointment (1 fte) as a PhD-student for four years,
• Gross monthly salary in accordance with the Collective Labor Agreement of the Dutch Universities (CAO NU), which favorably compares to conditions in the USA or UK,
• An attractive package of fringe benefits, including excellent work facilities, end of the year allowance, and sport facilities.