dynamic fracture

The research — We use x-ray phase contrast imaging (XPCI) to study deformation and fracture of materials under dynamic loading on microsecond and sub-microsecond time scales. For example, we might like to measure the change in pore size distribution of a granular material such as sandstone under impact loading.

It gives me great pleasure to announce the mini-symposium titled "Characterization and Modeling of Dynamic Fracture of Composites" at the 2021 Mach conference, to be held virtually from April 7 to April 9 2021.

The Mach Conference showcases the state of the art of multiscale research in materials, with an emphasis on advancing the fundamental science and engineering of materials and structures in extreme environments

Phase-field models for crack propagation enable the simulation of complex crack patterns without complex and expensive tracking and remeshing as cracks grow. In the setting without inertia, the crack evolution is obtained from a variational energetic starting point, and leads to an equation for the order parameter coupled to elastostatics. Careful mathematical analysis has shown that this is consistent with the Griffith model for fracture. Recent efforts to include inertia in this formulation have replaced elastostatics by elastodynamics.

Overview: The peridynamic formulation is a
spatially nonlocal derivative free model for simulating problems of free crack
propagation.Material points interact through short-range forces and the
formulation allows for discontinuous deformations. Here the short-range forces
are initially elastic and soften beyond a critical relative displacement. We
upscale this peridynamic model to find the macroscopic (a.k.a. small horizon)
limit. It is shown that the limiting macroscopic evolution has bounded energy
given by the bulk and surface energies of brittle fracture mechanics. The
macroscopic evolution corresponds to the simultaneous evolution
of the fracture surface and linear elastic displacement away from the crack

Hopkins Extreme Materials Institute (HEMI; hemi.jhu.edu) of The Johns Hopkins University is seeking a Postdoctoral Fellow to work on modeling fragmentation in brittle materials under extreme loading conditions. The potential candidate should have a Ph.D., with some background in fracture mechanics and experience working with the finite element or other numerical methods.  

A new postdoctoral position in continuum mechanics is available at the Weizmann Institute of Science. Candidates should have a strong background in physics and/or theoretical mechanics, as well as experience with analytical and computational methods for solving partial differential equations. Possible projects include the mechanics of frictional sliding, the mechanics of biomaterials, the mechanics of glassy materials and dislocation-mediated plasticity. Highly motivated candidates are requested to send their CV, publications list and statement of research interests to Dr.

In this paper we first obtain the order of stress singularity for a dynamically propagating self-affine fractal crack. We then show that there is always an upper bound to roughness, i.e. a propagating fractal crack reaches a terminal roughness. We then study the phenomenon of reaching a terminal velocity. Assuming that propagation of a fractal crack is discrete, we predict its terminal velocity using an asymptotic energy balance argument. In particular, we show that the limiting crack speed is a material-dependent fraction of the corresponding Rayleigh wave speed.

A postdoctoral fellowship is available in the Duke Computational Mechanics Laboratory, beginning in September of 2009 (with flexibility on timing).  Funding for the fellowship concerns research in the simulation of large-scale fragmentation phenomena.  The ideal candidate will have experience in some combination of the following areas:

The Computational Physics group in the Atmospheric, Earth, and Energy Division at the Lawrence Livermore National Laboratory (LLNL) is solicitating applications for three postdoctoral appointments in the following areas. To access the full description and application instructions, please visit http://jobs.llnl.gov and search for the job numbers below:

008351: geomechanics of fluid-induced fault activation

008374: dynamic impacts into granular materials

008375: mechanics of dynamic impact and penetration into ceramics

The group of Mechanics &
Computation in the Mechanical Engineering department at Stanford University has
an opening for a postdoctoral position in the area of computational mechanics
as part of the new Army High-Performance Computing Research Center (AHPCRC),
under the direction of Adrian Lew. The appointment
is normally made for one year, with the possibility of renewal for a second
year. The ideal candidate would have a strong background on
computational solid mechanics and have programming experience, ideally in C++.
A good background in mathematics, especially numerical analysis, will be