9,189 research outputs found
Numerical modeling of black holes as sources of gravitational waves in a nutshell
These notes summarize basic concepts underlying numerical relativity and in
particular the numerical modeling of black hole dynamics as a source of
gravitational waves. Main topics are the 3+1 decomposition of general
relativity, the concept of a well-posed initial value problem, the construction
of initial data for general relativity, trapped surfaces and gravitational
waves. Also, a brief summary is given of recent progress regarding the
numerical evolution of black hole binary systems.Comment: 28 pages, lectures given at winter school 'Conceptual and Numerical
Challenges in Femto- and Peta-Scale Physics' in Schladming, Austria, 200
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
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