Lomové chování povlakovaných materiálů

Failure behavior of coated materials

conference paper

en

Results concerning the influence of a through coating crack on the substrate failure are reported. The problem is studied under the assumptions corresponding to small scale yielding conditions and calculations are performed by the finite element method. An approximate approach based on calculations of crack mouth opening displacement for thin protective layers is suggested. It is concluded that in the case of a stiffer coating on a more compliant substrate, the through coating cracks represent dangerous stress concentrators, and as a consequence of elastic mismatch of both materials, the critical applied stress for substrate failure decreases. Traditional approaches may have underestimated this effect and estimations of the service life of coated structures neglecting this phenomenon could lead to non-conservative values, with unexpected failures.

V práci je vyšetřován odpor povlakovaných součástí vzhledem k únavovému porušení podkladu. Je zde navržen zjednodušený přístup, který je založen na otevření trhliny na povrchu součásti, umožňující kvantifikovar vliv elastického mismatch povlakovaných součástí na prahovou únavovou hodnotu napětí. Je ukázáno, že odpor podkladu vůči únavovému poškození výrazně klesá pro tvrdý povlak na poddajnějším podkladu. Tradiční přístupy mohou podhodnotit tento vliv a zanedbání této skutečnosti při hodnocení zbytkové životnosti povlakovaných součástí může vést k nekonzervativním hodnotám a způsobit tak neočekávné havárie.

Results concerning the influence of a through coating crack on the substrate failure are reported. The problem is studied under the assumptions corresponding to small scale yielding conditions and calculations are performed by the finite element method. An approximate approach based on calculations of crack mouth opening displacement for thin protective layers is suggested. It is concluded that in the case of a stiffer coating on a more compliant substrate, the through coating cracks represent dangerous stress concentrators, and as a consequence of elastic mismatch of both materials, the critical applied stress for substrate failure decreases. Traditional approaches may have underestimated this effect and estimations of the service life of coated structures neglecting this phenomenon could lead to non-conservative values, with unexpected failures.

crack mouth opening displacement, crack propagation, bimaterial interface

2005

23.08.2005

University of Zilina

Žilina

80-969165-4-8

10 th International Conference on Numerical Methods in Continuum Mechanics

47–48

2