کد مقاله کد نشریه سال انتشار مقاله انگلیسی نسخه تمام متن
1452524 988839 2017 14 صفحه PDF دانلود رایگان
عنوان انگلیسی مقاله ISI
On the propagation and coalescence of delamination cracks in compressed coatings: with application to thermal barrier systems
ترجمه فارسی عنوان
درباره انتشار و همبستگی ترک های لایه لایه شدگی در پوشش های فشرده: استفاده کاربردی از سیستم های مانع حرارتی
موضوعات مرتبط
مهندسی و علوم پایه مهندسی مواد سرامیک و کامپوزیت
چکیده انگلیسی

Coatings subject to residual compression eventually fail by buckle-driven delamination. The phenomenon is most vivid in thermal barrier coatings (TBCs) used in gas turbines. The failure evolution commences with the formation of a large number of small cracks at geometric imperfections near the interface. These cracks spread upon thermal exposure, particularly upon thermal cycling, because of the formation of a thermally grown oxide (TGO) beneath the TBC, which introduces normal and shear stress near the interface. Experimental observations indicate that some of these cracks coalesce to form large-scale delaminations susceptible to buckling. The mechanics governing crack coalescence and the consequent failure are addressed in the present analysis.A model is introduced that simulates stresses induced in the TBC by spatial variations in TGO growth. Energy release rates for cracks evolving in this stress field are determined. Two related scenarios are considered, which differ in the way the TGO shape evolves. In both, contact between the crack faces and the consequent wedging action is responsible for ultimate coalescence. The wedging force induces a mode I stress intensity that becomes infinite as the cracks coalesce. The consequence is that, for some TGO shapes, the energy release rate is always non-zero, with a minimum at a characteristic crack length. This minimum establishes a criterion for crack coalescence and failure.Based on these insights, finite element simulations have been used to predict cyclic crack growth rates in a TBC system that correlate well with experimental observations.

ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Acta Materialia - Volume 51, Issue 7, 18 April 2003, Pages 2017–2030
نویسندگان
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