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| Dissertation / PhD Thesis/Book | PreJuSER-33059 |
2003
Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag
Jülich
Please use a persistent id in citations: http://hdl.handle.net/2128/201
Report No.: Juel-4088
Abstract: Elastic effects play an important role in phase transitions if at least one solid phase is involved. Complicated processes during the undercooling or melting of multi-component alloys can produce high elastic stresses due to differences in the densities of the involved ingredients. During the segregation of melt inclusions inside an overheated solid, strong elastic interactions can appear and significantly modify the scaling behavior of the coarsening process. The usual mean-field behavior breaks down and several independent length scales have to be taken into account. The scaling laws for the coarsening in a system of parallel inclusions are derived. A closely related problem is the growth of cracks in a uniaxially strained solid. Several cracks can appear in the sample and lead to a relaxation of stresses; situations like this can often be observed in geological systems. A strong interplay between neighboring cracks lets the longer cracks grow at the expense of the shorter ones. Crack propagation exhibits several peculiarities for higher propagation velocities. A continuum theory which describes the fast growth of a crack by surface diffusion is presented. By introducing a fully dynamical theory of elasticity, it is possible to produce a self-consistent selection of thé crack tip radius. This theory describes the complicated dynamics of a crack tip, the saturation of the steady state velocity appreciably below the Rayleigh speed, and the blunting of the crack tip. Furthermore, it includes the possibility of a tip splitting instability for high applied tensions.
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