278 research outputs found
New universality class for the fragmentation of plastic materials
We present an experimental and theoretical study of the fragmentation of
polymeric materials by impacting polypropylene particles of spherical shape
against a hard wall. Experiments reveal a power law mass distribution of
fragments with an exponent close to 1.2, which is significantly different from
the known exponents of three-dimensional bulk materials. A 3D discrete element
model is introduced which reproduces both the large permanent deformation of
the polymer during impact, and the novel value of the mass distribution
exponent. We demonstrate that the dominance of shear in the crack formation and
the plastic response of the material are the key features which give rise to
the emergence of the novel universality class of fragmentation phenomena.Comment: 4 pages, 4 figures, appearing in Phys. Rev. Let
Crackling noise in three-point bending of heterogeneous materials
We study the crackling noise emerging during single crack propagation in a
specimen under three-point bending conditions. Computer simulations are carried
out in the framework of a discrete element model where the specimen is
discretized in terms of convex polygons and cohesive elements are represented
by beams. Computer simulations revealed that fracture proceeds in bursts whose
size and waiting time distributions have a power law functional form with an
exponential cutoff. Controlling the degree of brittleness of the sample by the
amount of disorder, we obtain a scaling form for the characteristic quantities
of crackling noise of quasi-brittle materials. Analyzing the spatial structure
of damage we show that ahead of the crack tip a process zone is formed as a
random sequence of broken and intact mesoscopic elements. We characterize the
statistics of the shrinking and expanding steps of the process zone and
determine the damage profile in the vicinity of the crack tip.Comment: 11 pages, 15 figure
Universality class of the fragmentation of plastic materials
We carry out an experimental and theoretical study of the fragmentation of polymeric materials by impacting polypropylene (PP) particles of spherical shape against a hard wall. Our experiments revealed that the mass distribution of fragments has a power law behavior with an exponent close to 1.2, which is significantly different from the known exponents of threedimensional bulk materials. To understand the fragmentation of plastic
materials we developed a threedimensional discrete element model where the sample is represented as a random packing of spherical particles connected by elastic beams. The model reproduces both the large permanent deformation of the polymer during impact, and the novel value of the mass distribution exponent. Computer simulations revealed that the dominance of shear in the crack formation and the healing of compressed crack surfaces are the key features which give rise to the emergence of the novel universality
class of fragmentation phenomena
Universality class of the fragmentation of plastic materials
We carry out an experimental and theoretical study of the fragmentation of polymeric materials by impacting polypropylene (PP) particles of spherical shape against a hard wall. Our experiments revealed that the mass distribution of fragments has a power law behavior with an exponent close to 1.2, which is significantly different from the known exponents of threedimensional bulk materials. To understand the fragmentation of plastic
materials we developed a threedimensional discrete element model where the sample is represented as a random packing of spherical particles connected by elastic beams. The model reproduces both the large permanent deformation of the polymer during impact, and the novel value of the mass distribution exponent. Computer simulations revealed that the dominance of shear in the crack formation and the healing of compressed crack surfaces are the key features which give rise to the emergence of the novel universality
class of fragmentation phenomena
Observation of Anomalous Internal Pair Creation in Be: A Possible Signature of a Light, Neutral Boson
Electron-positron angular correlations were measured for the isovector
magnetic dipole 17.6 MeV state (, ) ground state
(, ) and the isoscalar magnetic dipole 18.15 MeV (,
) state ground state transitions in Be. Significant
deviation from the internal pair creation was observed at large angles in the
angular correlation for the isoscalar transition with a confidence level of . This observation might indicate that, in an intermediate step, a
neutral isoscalar particle with a mass of 16.70 (stat)
(sys) MeV and was created.Comment: 5 pages, 5 figure
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