| Thermal barrier coatings?TBCs?systems have been widely used to protect metallic components exposed to extreme temperature in gas turbine,thus improving the inlet temperature and lifespan of metallic components.A typical TBC system consists of a thermal barrier coating?TBC?,a thermally grown oxide?TGO?,a bond coat?BC?and a supperalloy substrate?SUB?.TGO is formed during preparation of TBCs,the morphology and chemical composition of which evolve during high temperature dwell in service.Partial delamination of TBC is strongly influenced by TGO growth and rumpling.In this paper,2D and 3D models of TBCs including TGO,BC and SUB are created by SOLIDWORKS and the subroutine UEXPAN used to simulate the growth of TGO is developed based on commercial finite element software ABAQUS.The influence of material parameters,calculation methods,applied mechanical load and thermomechanical phase angle on TGO rumpling behavior and are investigated in 2D models,while the influence of material parameters and applied mechanical load on TGO rumpling behavior are investigated in 3D models.Cmparison between 2D finite element results,3D finite element results and analytical solution are conducted to probe the applicable range of analytical solution for multi-layer continuum.The main results are as follows:?1?2D finite element results calculated under generalized plane strain are similar to 3D finite element results,which prove the applicability of generalized plane strain in our research.?2?Finite element results and analytical solution are comparable when?BC?thermal expansion coefficient of BC?=2.1×10-5/K at 1423.15K,A?creep power law multiplier of BC?=1.35×10-10 and?g?lateral growth strain?=0.00038.The influence of these material parameters on TGO rumpling are different and can be concluded as follows:?1?The increasing of thermal expansion coefficient of BC contribute to the increasing of TGO amplitude in both directions.?2?The increasing of lateral growth strain also result in the increasing of TGO amplitude in both directions,but TGO amplitude in the perpendicular direction almost keeps the same when?g?0.00038.?3?Creep power law multiplier of BC is not a sensitive parameter influencing TGO amplitude.?3?The influence of thermomechanical phase angle on TGO rumpling is studied in 2D model.Under tensile mechanical load:TGO amplitude shows the largest value when phase shift60oand the smallest value when phase shift 0o.Under compressive mechanical load:TGO amplitude shows the largest value when phase shift 300oand the smallest value when phase shift 120o.?4?TGO rumpling performs slight anisotropy characteristics in finite element model when-60MPa??max?60MPa,while TGO rumpling exhibits no anisotropy in analytical model under the same range of applied load.When?max?60MPa,TGO amplitude in the parallel direction decreases with the increase of applied tension,but TGO amplitude in the perpendicular direction increases with the the increase of applied tension.Under the same range of applied load,TGO amplitude in two directions show the same tendency with the change of applied load in analytical model.The difference lies in that the anisotropy degree increase in a faster speed with the increase of applied tension in analytical model compared with that in the finite element model.When?max?-60MPa,TGO amplitude in the parallel direction increases with the increase of applied compression,but TGO amplitude in the perpendicular direction decreases with the the increase of applied compression.Under the same range of applied load,TGO amplitude in two directions show the same tendency with the change of applied load in analytical model.The difference lies in that the anisotropy degree decreases in a slower speed with the increase of applied compression in analytical model compared with that in the finite element model. |
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