Surrogate model for energy release rate and structure optimization of double-ceramic-layers thermal barrier coatings system

2021 ◽  
pp. 127989
Author(s):  
Yongqiang Zhu ◽  
Bo Yan ◽  
Mao Deng ◽  
Huachao Deng ◽  
Daoda Cai
Keyword(s):  
Energy Release Rate ◽  
Energy Release ◽  
Thermal Barrier Coatings ◽  
Release Rate ◽  
Surrogate Model ◽  
Structure Optimization ◽  
Thermal Barrier ◽  
Barrier Coatings

scholarly journals The Temperature Distribution in Plasma-Sprayed Thermal-Barrier Coatings During Crack Propagation and Coalescence

Coatings ◽  
2018 ◽  
Vol 8 (9) ◽  
pp. 311 ◽  
Author(s):  
Hui Dong ◽  
Yan Han ◽  
Yong Zhou ◽  
Xiao Li ◽  
Jian-Tao Yao ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Temperature Distribution ◽  
Energy Release Rate ◽  
Thermal Barrier Coatings ◽  
Release Rate ◽  
Temperature Rise ◽  
Maximum Temperature ◽  
Thermal Barrier ◽  
Barrier Coatings ◽  
Ysz Coating

A Finite-Element Model (FEM) for thermal-barrier coatings was employed to elaborate the temperature distribution on yttria-stabilized zirconia (YSZ) free surface during cracks coalescing, then the influence of sintering of YSZ induced by heat-transfer overlapping on energy release rate was quantificationally evaluated. A three-dimensional model including three layers was fabricated. Two types of cracks, with and without depth variations in YSZ coating, were introduced into the model, respectively. The temperature rise of YSZ coating over the crack is independent of each other at the beginning of crack propagation. As crack distance shortens, the independent temperature-rise regions begin to overlap, while maximum temperature is still located at the crack center before crack coalescence. The critical distance that the regions of temperature rise, just overlapping, is the sum of half lengths of two coalescing cracks (i.e., a1 + a2), which is independent of cracking path. The maximum temperature in YSZ sharply increases once cracks coalesce. Compared with one delamination crack, the effective energy-release rate induced by heat-transfer overlapping increases in the range of 0.2%–15%, depending on crack length and crack distance, which is on some level comparable to that of deterioration of thermal expansion misfit induced by temperature jump between crack faces.

scholarly journals The Influence of Transient Thermal Gradients and Substrate Constraint on Delamination of Thermal Barrier Coatings

2012 ◽  
Vol 80 (1) ◽  
Author(s):  
S. Sundaram ◽  
D. M. Lipkin ◽  
C. A. Johnson ◽  
J. W. Hutchinson
Keyword(s):  
Energy Release Rate ◽  
Energy Release ◽  
Release Rate ◽  
Early Stage ◽  
Maximum Energy ◽  
Thermal Barrier ◽  
Substrate Thickness ◽  
Thermal Gradients ◽  
Surface Cooling ◽  
Transient Thermal

A systematic study of factors affecting the delamination energy release rate and mode mix of a thermal barrier coating attached to a substrate is presented accounting for the influence of thermal gradients combined with rapid hot surface cooling. Transient thermal gradients induce stress gradients through the coating and substrate, which produce overall bending if the substrate is not very thick and if it is not constrained. Due to their influences on the coating stresses, substrate thickness and constraint are important aspects of the mechanics of delamination of coating-substrate systems, which must be considered when laboratory tests are designed and for lifetime assessment under in-service conditions. Temperature gradients in the hot state combined with rapid cooling give rise to a maximum energy release rate for delamination that occurs in the early stage of cooling and that can be considerably larger than the driving force for delamination in the cold state. The rates of cooling that give rise to a large early stage energy release rate are identified.

Stress Intensity Factors for Interfacial Cracks in Thick Thermal Barrier Coatings

1998 ◽  
Author(s):  
C. Bjerken ◽  
C. Persson
Keyword(s):  
Energy Release Rate ◽  
Energy Release ◽  
Release Rate ◽  
Thermal Barrier ◽  
Intensity Factors ◽  
Mode Mixity ◽  
Release Rates ◽  
Edge Angle ◽  
Interfacial Cracks ◽  
Energy Release Rates

Abstract A straight-forward method for calculating the stress intensity factors (or the energy release rate and mode mixity) for interfacial cracks in bi-materials has been developed. An existing method for homogeneous materials, based on the computation of the energy release rate from the nodal forces and displacements given by a finite element analysis, was modified to include the mismatch in material properties. Thick thermal barrier coatings usually fail as a result of cracking near the interface. The influence of the thickness and the edge angle of the coating on the energy release rate and mode mixity for a small edge crack at the interface of a TBC system subjected to thermal loading was investigated. It was established that the high energy release rates obtained for thick coatings can be reduced by decreasing the edge angle of the coating. Additionally a comparison with energy release rates given by J-integral computations has been done.

scholarly journals Microcrack propagation induced by dynamic infiltration of calcium-magnesium-alumino-silicate in columnar structures for thermal barrier coatings

2020 ◽  
Author(s):  
Shaochen Tseng ◽  
Chingkong Chao ◽  
Weixu Zhang ◽  
X.L. Fan
Keyword(s):  
Energy Release Rate ◽  
Energy Release ◽  
Release Rate ◽  
Thermal Barrier ◽  
High Porosity ◽  
Columnar Microstructure ◽  
Premature Failure ◽  
Barrier Coating ◽  
Microcrack Propagation ◽  
Calcium Magnesium

Abstract Columnar-structured thermal barrier coating systems (TBCs) possess a strain tolerant columnar microstructure wherein the gaps between the columns are filled with high-porosity oxides. At high temperatures, columnar-structured TBCs may be eroded via contact with a significant amount of calcium-magnesium-alumina-silicate (CMAS). A numerical model is proposed to estimate the temperature and stress fields of the microcracks induced by the CMAS infiltration. The energy release rate is evaluated to understand the influence of CMAS on the microcracks in the columnar microstructure. The effects of CMAS on the microcrack propagation are discussed in detail by using the extended finite element method. The results demonstrate that both the stress and energy release rate near the microcrack were found to dramatically increase when the CMAS reached the microcrack. Moreover, increasing the time of CMAS infiltration could destroy the thermal insulation provided by the top coat and considerably increase the energy release rate. The present analysis reveals that the vertical cracks are easily to initiate from the microstructure column and coalesce with adjacent horizontal and vertical pores, thereby resulting in premature failure of TBCs via delamination.

Characterization of thermal barrier coatings formed by electon-beam physical vapor deposition (EB-PVD)

1989 ◽  
Vol 47 ◽  
pp. 426-427
Author(s):  
Ozer Unal
Keyword(s):  
Thermal Barrier Coatings ◽  
Physical Vapor Deposition ◽  
Ceramic Coating ◽  
High Vacuum ◽  
Ceramic Coatings ◽  
High Energy ◽  
Thermal Barrier ◽  
Protective Oxide ◽  
Barrier Coatings ◽  
Energy Beam

Interest in ceramics as thermal barrier coatings for hot components of turbine engines has increased rapidly over the last decade. The primary reason for this is the significant reduction in heat load and increased chemical inertness against corrosive species with the ceramic coating materials. Among other candidates, partially-stabilized zirconia is the focus of attention mainly because ot its low thermal conductivity and high thermal expansion coefficient.The coatings were made by Garrett Turbine Engine Company. Ni-base super-alloy was used as the substrate and later a bond-coating with high Al activity was formed over it. The ceramic coatings, with a thickness of about 50 μm, were formed by EB-PVD in a high-vacuum chamber by heating the target material (ZrO2-20 w/0 Y2O3) above its evaporation temperaturef >3500 °C) with a high-energy beam and condensing the resulting vapor onto a rotating heated substrate. A heat treatment in an oxidizing environment was performed later on to form a protective oxide layer to improve the adhesion between the ceramic coating and substrate. Bulk samples were studied by utilizing a Scintag diffractometer and a JEOL JXA-840 SEM; examinations of cross-sectional thin-films of the interface region were performed in a Philips CM 30 TEM operating at 300 kV and for chemical analysis a KEVEX X-ray spectrometer (EDS) was used.

Calculating Energy Release Rate as a Function of Crack Length Using a Multiple-Step Crack Closure Technique in Tire Finite Element Models

2018 ◽  
Vol 46 (3) ◽  
pp. 130-152
Author(s):  
Dennis S. Kelliher
Keyword(s):  
Finite Element ◽  
Energy Release Rate ◽  
Crack Length ◽  
Energy Release ◽  
Crack Closure ◽  
Release Rate ◽  
Fatigue Behavior ◽  
Three Dimensions ◽  
Quantitative Prediction ◽  
Closure Technique

ABSTRACT When performing predictive durability analyses on tires using finite element methods, it is generally recognized that energy release rate (ERR) is the best measure by which to characterize the fatigue behavior of rubber. By addressing actual cracks in a simulation geometry, ERR provides a more appropriate durability criterion than the strain energy density (SED) of geometries without cracks. If determined as a function of crack length and loading history, and augmented with material crack growth properties, ERR allows for a quantitative prediction of fatigue life. Complications arise, however, from extra steps required to implement the calculation of ERR within the analysis process. This article presents an overview and some details of a method to perform such analyses. The method involves a preprocessing step that automates the creation of a ribbon crack within an axisymmetric-geometry finite element model at a predetermined location. After inflating and expanding to three dimensions to fully load the tire against a surface, full ribbon sections of the crack are then incrementally closed through multiple solution steps, finally achieving complete closure. A postprocessing step is developed to determine ERR as a function of crack length from this enforced crack closure technique. This includes an innovative approach to calculating ERR as the crack length approaches zero.

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