4 research outputs found
Fatigue crack propagation in a quasi one-dimensional elasto-plastic model
Fatigue crack advance induced by the application of cyclic quasistatic loads
is investigated both numerically and analytically using a lattice spring model.
The system has a quasi-one-dimensional geometry, and consists in two
symmetrical chains that are pulled apart, thus breaking springs which connect
them, and producing the advance of a crack. Quasistatic crack advance occurs as
a consequence of the plasticity included in the springs which form the chains,
and that implies a history dependent stress-strain curve for each spring. The
continuous limit of the model allows a detailed analytical treatment that gives
physical insight of the propagation mechanism. This simple model captures key
features that cause well known phenomenology in fatigue crack propagation, in
particular a Paris-like law of crack advance under cyclic loading, and the
overload retardation effect.Comment: To be published in the International Journal of Solids and Structure
Can one have preroughening of vicinal surfaces?
We discuss the possibility that, besides roughening, a vicinal surface could
display preroughening (PR), and consider the possible mechanisms for its
promotion. Within the framework of a terrace-step-kink model, it turns out that
a PR transition is possible, and could be induced by a short-range repulsion
between parallel kinks along the same step or on adjacent steps, or even by
some kind of extended range step-step repulsion. We discuss the possible
relevance of this phenomenon to the anomalous roughening behaviour recently
reported for Ag(115).Comment: 9 pages, 3 postscript figures, submitted to Surface Scienc
The Fate of Shear-Oscillated Amorphous Solids
The behavior of shear-oscillated amorphous materials is studied using a
coarse-grained model. Samples are prepared at different degrees of annealing
and then subject to athermal and quasistatic oscillatory deformations at
various fixed amplitudes. The steady-state reached after several oscillations
is fully determined by the initial preparation and the oscillation amplitude,
as seen from stroboscopic stress and energy measurements. Under small
oscillations, poorly annealed materials display shear-annealing, while
ultra-stabilized materials are insensitive to them. Yet, beyond a critical
oscillation amplitude, both kind of materials display a discontinuous
transition to the same mixed state composed by a fluid shear-band embedded in a
marginal solid. Quantitative relations between uniform shear and the
steady-state reached with this protocol are established. The transient regime
characterizing the growth and the motion of the shear band is also studied.Comment: 6 pages, 4 figure