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dynamic fracture

Dependence of Equilibrium Griffith Surface Energy on Crack Speed in Phase-Field Models for Fracture Coupled to Elastodynamics

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.

Dependence of fracture energy of ceramic on loading condition?

Literature suggests that the fracture strength of the ceramic tends to be higher in a dynamic loading condition than in static condition. This relates to the increase in the fracture energy in dynamic processes. Literature refers to an inelastic response prior to failure (Hugoniot elastic limit) the reason behind increased strength. Can anyone explain the phenomenon in a more lucid way, or guide me to an appropriate reference to understand this?

Dynamic Brittle Fracture as a Small Horizon Limit of Peridynamics

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

ndaphalapurkar's picture

A Postdoctoral Fellowship is available

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.  

Eran Bouchbinder's picture

A new postdoc position is available

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.

Arash_Yavari's picture

Estimating Terminal Velocity of Rough Cracks

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.

Postdoctoral Fellow in Computational Mechanics

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:

Three postdoctoral positions at Lawrence Livermore National Laboratory

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

POST-DOCTORAL POSITION ON COMPUTATIONAL MECHANICS AT STANFORD UNIVERSITY

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

L. Roy Xu's picture

Intersonic interface crack propagation (two shock waves)

This high-speed photography image recorded a very special fracture mechanics phenomenon: two fast cracks (as demonstrated by two shear shock waves) just met at the specimen center. After a steel projectile hit a model sandwich plate (steel/transparent Homalite -100 polymer/steel), stress wave propagation was observed in the form of photo-elasticity fringe movement. Two interfacial cracks from the two ends of the model sandwich plate, entered the field of view with very high speeds (> 1400m/s) and formed two shock waves (since the crack tip speed exceeded the shear wave speed of the polymer). For further technical details and more photos, click here to read the related paper (Xu and Rosakis, IJSS, 2002) For more real movies recorded from a high-speed camera( click here). It will take a few minutes to access my movie site since the size of each movie is quite large. But the movie resolution and layout from my site is much better than the movie from YouTube (below). © Dr. L. R. Xu (Vanderbilt University) and Dr. A. J. Rosakis (California Institute of Technology)

L. Roy Xu's picture

Interaction between an Interface and a Dynamic Incident Mode-I Crack

This high-speed photography image shows a mode I crack (representing by a symmetric photo elasticity fringe pattern) is approaching a weak interface in a brittle polymer (Homatel-100). The crack tip speed is around 300-400 m/s. There will be three possibly situations for dynamic interfacial failure mode transitions : 1) crack kinks at the interface, 2) crack directly penetrates the interface and 3) interface debonding occurs before the incident crack reaches the interface. Which case will occur?

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