Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
7169785 | Engineering Fracture Mechanics | 2015 | 15 Pages |
Abstract
This work describes a mechanism for the initiation of delamination cracks in Al-Li alloys based on the soft/stiff character of adjacent grains. Small-scale-yielding, crystal plasticity simulations of divider grain configurations (L-T) reveal an elevated mean stress on grain boundaries. This mean stress increase drives a sharp localization of the Rice-Tracey parameter to the grain boundaries - elevation of the RT parameter indicates favorable conditions for void growth and triggering of delamination cracking, in agreement with the fractography of Ritchie and co-workers. Our simulation results and available experimental evidence indicate delamination initiates typically between soft/stiff grain pairs, often Bs (Bunge-convention Euler angles Ï1=131°, Φ=83°,Ï2=307°) or S (Ï1=233°, Φ=151°,Ï2=105°) orientations. The crystal plasticity results and a simple model of a soft/stiff material interface show that mean stress accumulation is a consequence of the mechanics of such an interface, and not necessarily tied to material inhomogeneities near the GBs (such as precipitate free zones).
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Authors
M.C. Messner, A.J. Beaudoin, R.H. Jr.,