Berlin 2008 – wissenschaftliches Programm
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MM: Fachverband Metall- und Materialphysik
MM 7: Diffusion II
MM 7.3: Vortrag
Montag, 25. Februar 2008, 12:30–12:45, H 0111
Steady drift-diffusion model of impurity induced subcritical crack propagation — •Mario Koch1 and Peter Streitenberger2 — 1Institut der Feuerwehr Sachsen-Anhalt, Biederitzer Str. 5, 39175 Heyrothsberge, Deutschland — 2Otto-von-Guericke-Universität Magdeburg, PSF 4120, 39016 Magdeburg, Deutschland
The stress-driven diffusion of point defects to a slowly moving crack under mixed-mode loading is studied by solving the corresponding drift-diffusion equation in a co-moving reference system. Numerical solutions for the quasi-stationary concentration fields and flow field patterns are presented, which reveal important insights into the point-defect migration kinetics near a steadily advancing crack. In particular, it is shown that only impurities within a limited drift-diffusion zone, of which the extension depends on the average crack growth rate, are able to migrate to the crack tip. Considering the existence of a critical impurity concentration per crack length advance as the basic criterion for failure of the material, the crack growth behaviour in form of the crack growth rate versus stress intensity factor curve is calculated. In the case where the size of the plastic zone is very small in comparison with the drift-diffusion zone stage I crack growth is observed, if the size of the plastic zone is very large in comparison with the drift-diffusion zone stage II crack growth is observed.