Postdoctoral position in modeling and numerical simulation of shockwaves in porous materials

Modeling and numerical simulation of shockwaves in porous materials

A postdoctoral position is available immediately in the Laboratory of Microstructure Studies and Mechanics of Materials (LEM3) of the University of Lorraine (UL) in Metz, France.

Candidates must be self-starter and have a solid background in numerical simulation of high strain rate phenomena. The candidate must also be familiar with analytical approaches (continuum mechanics, plasticity, viscoplasticity, …).

Keywords:

Dynamic behavior; Shockwaves; Finite Element Modeling and Numerical Simulation; Micro-inertia effects;

Start Date: As soon as possible            Duration: 12 months                      Monthly gross salary: 2 770 €

Application

To be considered, applicants should send an email to Dr. Christophe Czarnota: christophe.czarnota@univ-lorraine.fr with the following documents:

a CV, the list of publications and conferences, a PhD abstract, a motivation letter, a recommendation letter, scientific references.

Note that only applications providing all application requirements will be further considered. Review of applications will begin immediately and continue until the position is filled.

Scientific context and objectives

Dynamic response of porous materials is of primary importance in numerous fields whether it concerns optimization of blast mitigation devices, collision processes in the solar system, clinical applications such as kidney stones fragmentation by shock wave lithotripsy. Upon impact at high velocity, a shockwave is generally formed and propagates in the impacted sample. For porous materials, the structure of steady shockwaves is a complex phenomenon involving in general the interplay of micro-inertia effects with the nonlinear elastic viscoplastic response of the matrix. Micro-inertia effects are due to the important acceleration of material particles near the collapsing voids. An explicit relationship has been derived from a dynamic homogenization approach by the UL team (Molinari and Mercier, 2001) where relationship between the microstructure of the porous material (pore size and mean separation distance) and the dynamic behavior was clearly highlighted. This modeling has been implemented in a FE code (Abaqus) and extended to account for nucleation of voids in an initially dense tantalum material (Czarnota et al., 2008, Versino & Bronkhorst, 2018). Due to the presence of micro-inertia in the modeling, free surface velocity profiles obtained from impact tests under various loading configurations have been successfully restituted from numerical simulations;

More recently, micro-inertia effects were shown to strongly influence shockwave propagation in porous aluminum. An analytical approach has been developed in Czarnota et al. (2017) where the shock width (a true signature of a shockwave) was found to be scaled by the microstructure of the porous material.

The goal of the post-doctoral project is to develop finite element models and conduct numerical simulations of shockwave propagation in porous media. The objectives are to analyze local acceleration fields and to highlight, using a discrete finite element model, the connection between the microstructure and the overall response. The study would also allow to clarify and identify various collapse mechanisms that can occur during shockwave propagation. This work will be useful to develop a better knowledge of the dynamic damage in porous materials, in order to optimize protective devices subjected to dynamic loading.

References

A. Molinari and S. Mercier, J. Mech. Phys. Solids, 49, 1497-1516 (2001).

C. Czarnota, N. Jacques, S. Mercier and A. Molinari, J. Mech. Phys. Solids, 56, 1624-1650 (2008).

C. Czarnota, A. Molinari and S. Mercier, J. Mech. Phys. Solids, 107, 204-228 (2017).

D. Versino, C. A. Bronkhorst, Comput. Methods Appl. Mech. Engng 333, 395–420 (2018).