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On the evaluation of interfacial crack initiation by means of finite fracture mechanics

 
: Müller, A.; Hohe, J.; Becker, W.

11th International Conference on Fracture 2005, ICF11. Vol.3 : Proceedings of a meeting held 20-25 March 2005, Turin, Italy
Red Hook, NY: Curran, 2005
ISBN: 978-1-617-82063-2
S.2055-2060
International Conference on Fracture <11, 2005, Turin>
Englisch
Konferenzbeitrag
Fraunhofer IWM ()

Abstract
The evaluation of the degree of criticality of crack nucleation, initiation and propagation in the vicinity of bimaterial notches and the reliability of the junctions is a demanding problem, since bimaterial wedge or notch configurations are identified as potential weak locations. The singular character of the stress field at cracks or notches can be investigated analytically or numerically, the angle of the direction of potential crack initiation may also be determined, but the decisive question is whether crack initiation and subsequent crack arrest will really occur or not. An essential requirement in this context is a dependable criterion for crack nucleation. For that aim, the hypothesis of Leguillon is modified. Herein, the crack is assumed to be initiated and to grow if and only if both the released energy and the local stress reach critical values. Thus, simulating virtual crack growth along an interface, the integrity of the joint is revisable and finite charac teristic crack lengths can be determined and assessed. This concept is transferred to a bimaterial interface configuration of a thin layer on a substrate under high thermal loading, as required for modern high temperature Solid Oxide Fuel Cell Stacks. Within the fuel cell stack, multilayered ceramic components have to be embedded in metallic interconnect frames. Due to the mismatch of the individual layers and the interconnect in the mechanical and thermal properties, the joints, as regions of material and geometrical discontinuities, are highly demanded and are potential weak locations.

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