The experiments were conducted to investigate the behavior of airborne particles adhering to the glass slides which were coated by several reagent films. The results showed that the adhesion level could be significant...The experiments were conducted to investigate the behavior of airborne particles adhering to the glass slides which were coated by several reagent films. The results showed that the adhesion level could be significantly changed by the reagent films. There were no evident rules between the average size of particles and sampling time interval, the placing angle and reagent concentration. The average particle size on the surface coated by composite reagent （2-3 μm） was smaller than that on the single reagent coated surface, while the largest particle size （4-5 μm） was observed on the surface coated with the Tween 60. The experiment also demonstrated that the best adhesive performance was obtained on the surface which was coated with 0.5% SDBS and 0.5% fluorocarbon composite reagents. The experiment results indicated that each reagent had a certain optimum adhesive range to the particle. The composite reagents with different proportion of single reagents exhibited some particular physical and chemical properties, which could effectively change the adhesive performance between the solid surface and the particles.展开更多
The distribution and magnitude of surface substrates were investigated by finite element method and subsurface stresses of the （FEM）. The models of coating single-layer sprayed-coatings on monolithic configurations ...The distribution and magnitude of surface substrates were investigated by finite element method and subsurface stresses of the （FEM）. The models of coating single-layer sprayed-coatings on monolithic configurations with different thicknesses and elastic modulus ratios of coating to substrate were introduced, and the effects of thickness and elastic modulus ratio on the stresses were addressed. The calculation results show that the coating/substrate interface shear stress obviously decreases with increasing coating thickness, due to the location of the maximum shear stress moving away from the coating/substrate interface. At the same time, the magnitude of von Mises stress also declines in the case of thicker coatings. However, the high elastic modulus ratio results in extremely high maximum shear stress and the severe discontinuity of the von Mises stress curves, which leads to the intensive stress concentration on the coating/substrate interface. So the coating configurations with the larger coating thickness and lower difference of elastic modulus between coating and substrate exhibit excellent resistant performance of rolling contact fatigue （RCF）.展开更多
Thermal barrier coating(TBC)systems are widely used in industrial gas-turbine engines.However,premature failures have impaired the use of TBCs and cut down their lifetime,which requires a better understanding of their...Thermal barrier coating(TBC)systems are widely used in industrial gas-turbine engines.However,premature failures have impaired the use of TBCs and cut down their lifetime,which requires a better understanding of their failure mechanisms.In the present study,experimental studies of isothermal cycling are firstly carried out with the observation and estimation of microstructures.According to the experimental results,a finite element model is established for the analysis of stress perpendicular to the TBC/BC interface.Detailed residual stress distributions in TBC are obtained to reflect the influence of mechanical properties,oxidation,and interfacial roughness.The calculated results show that the maximum tensile stress concentration appears at the peak of TBC and continues to increase with thermal cycles.Because of the microstructural characteristics of plasma-sprayed TBCs,cracks initialize in tensile stress concentration(TSC)regions at the peaks of TBC and propagate along the TBC/BC interface resulting in the spallation of TBC.Also,the inclusion of creep is crucial to failure prediction and is more important than the inclusion of sintering in the simulation.展开更多
基金Project (50974132) supported by the National Natural Science Foundation of ChinaProject (2011QNZT094) supported by the Fundamental Research Funds for the Central Universities, China
文摘The experiments were conducted to investigate the behavior of airborne particles adhering to the glass slides which were coated by several reagent films. The results showed that the adhesion level could be significantly changed by the reagent films. There were no evident rules between the average size of particles and sampling time interval, the placing angle and reagent concentration. The average particle size on the surface coated by composite reagent （2-3 μm） was smaller than that on the single reagent coated surface, while the largest particle size （4-5 μm） was observed on the surface coated with the Tween 60. The experiment also demonstrated that the best adhesive performance was obtained on the surface which was coated with 0.5% SDBS and 0.5% fluorocarbon composite reagents. The experiment results indicated that each reagent had a certain optimum adhesive range to the particle. The composite reagents with different proportion of single reagents exhibited some particular physical and chemical properties, which could effectively change the adhesive performance between the solid surface and the particles.
基金Project(2007AA04Z408) supported by the National High-Tech Research and Development Program of ChinaProject(50735006) supported by the National Natural Science Foundation of China
文摘The distribution and magnitude of surface substrates were investigated by finite element method and subsurface stresses of the （FEM）. The models of coating single-layer sprayed-coatings on monolithic configurations with different thicknesses and elastic modulus ratios of coating to substrate were introduced, and the effects of thickness and elastic modulus ratio on the stresses were addressed. The calculation results show that the coating/substrate interface shear stress obviously decreases with increasing coating thickness, due to the location of the maximum shear stress moving away from the coating/substrate interface. At the same time, the magnitude of von Mises stress also declines in the case of thicker coatings. However, the high elastic modulus ratio results in extremely high maximum shear stress and the severe discontinuity of the von Mises stress curves, which leads to the intensive stress concentration on the coating/substrate interface. So the coating configurations with the larger coating thickness and lower difference of elastic modulus between coating and substrate exhibit excellent resistant performance of rolling contact fatigue （RCF）.
基金supported by the National Natural Science Foundation of China(Grant Nos.11232008 and 11372118)the Tsinghua University Initiative Scientific Research Program
文摘Thermal barrier coating(TBC)systems are widely used in industrial gas-turbine engines.However,premature failures have impaired the use of TBCs and cut down their lifetime,which requires a better understanding of their failure mechanisms.In the present study,experimental studies of isothermal cycling are firstly carried out with the observation and estimation of microstructures.According to the experimental results,a finite element model is established for the analysis of stress perpendicular to the TBC/BC interface.Detailed residual stress distributions in TBC are obtained to reflect the influence of mechanical properties,oxidation,and interfacial roughness.The calculated results show that the maximum tensile stress concentration appears at the peak of TBC and continues to increase with thermal cycles.Because of the microstructural characteristics of plasma-sprayed TBCs,cracks initialize in tensile stress concentration(TSC)regions at the peaks of TBC and propagate along the TBC/BC interface resulting in the spallation of TBC.Also,the inclusion of creep is crucial to failure prediction and is more important than the inclusion of sintering in the simulation.
