Machined surface integrity of workpieces in harsh environments has a remarkable influence on their performance.However,the complexity of the new type of machining hinders a comprehensive understanding of machined surf...Machined surface integrity of workpieces in harsh environments has a remarkable influence on their performance.However,the complexity of the new type of machining hinders a comprehensive understanding of machined surface integrity and its formation mechanism,thereby limiting the study of component performance.With increasing demands for high-quality machined workpieces in aerospace industry applications,researchers from academia and industry are increasingly focusing on post-machining surface characterization.The profile grinding test was conducted on a novel single-crystal superalloy to simulate the formation of blade tenons,and the obtained tenons were characterized for surface integrity elements under various operating conditions.Results revealed that ultrasonic vibration-assisted grinding(UVAG)led to multiple superpositions of abrasive grain trajectories,causing reduced surface roughness(an average reduction of approximately29.6%)compared with conventional grinding.After examining the subsurface layer of UVAG using transmission electron microscopy,the results revealed that the single-crystal tenon grinding subsurface layer exhibited a gradient evolution from the near-surface to the substrate.This evolution was characterized by an equiaxed nanocrystalline layer measuring 0.34μm,followed by a submicrocrystalline grain-forming zone spanning 0.6μm and finally,a constituent phase-twisted dis-torted deformation zone over 0.62μm.Under normal grinding conditions,the tenon exhibited low surface hardening(not exceeding 15%),and residual compressive stresses were observed on its surface.In cases where grinding burns occurred,a white layer appeared on the tenon's surface,which demonstrated varying thicknesses along the teeth from top to root due to thermal-force-structural coupling effects.Additionally,these burns introduced residual tensile stresses on the tenon's surface,potentially substantially affecting its fatigue life.This paper enhances our understanding of UVAG processes and establishes a foundation for their application in manufacturing singlecrystal turbine blades for next-generation aero-turbine engines.展开更多
The undeformed chip thickness and grinding force are key parameters for revealing the material removal mechanism in the grinding process.However,they are difficult to be well expressed due to the ununiformed protrusio...The undeformed chip thickness and grinding force are key parameters for revealing the material removal mechanism in the grinding process.However,they are difficult to be well expressed due to the ununiformed protrusion height and random position distribution of abrasive grains on the abrasive wheel surface.This study investigated the distribution of undeformed chip thickness and grinding force considering the non-uniform characteristics of abrasive wheel in the grinding of K4002 nickel-based superalloy.First,a novel grinding force model was established through a kinematic-geometric analysis and a grain-workpiece contact analysis.Then,a series of grinding experiments were conducted for verifying the model.The results indicate that the distribution of undeformed chip thickness is highly consistent with the Gaussian distribution formula.The increase in the grinding depth mainly leads to an increase in the average value of Gaussian distribution.On the contrary,the increase in the workpiece infeed speed or the decrease in the grinding speed mainly increases the standard deviation of Gaussian distribution.The average and maximum errors of the grinding force model are 4.9%and 14.6%respectively,indicating that the model is of high predication accuracy.展开更多
基金supported by the National Natural Science Foundation of China(Nos.92160301,92060203,52175415,52205475,and 52322510)the Science Center for Gas Turbine Project(No.P2023-B-IV-003-001)+1 种基金the Huaqiao University Engineering Research Center of Brittle Materials Machining(No.2023IME-001)the Natural Science Foundation of Jiangsu Province(No.BK20210295).
文摘Machined surface integrity of workpieces in harsh environments has a remarkable influence on their performance.However,the complexity of the new type of machining hinders a comprehensive understanding of machined surface integrity and its formation mechanism,thereby limiting the study of component performance.With increasing demands for high-quality machined workpieces in aerospace industry applications,researchers from academia and industry are increasingly focusing on post-machining surface characterization.The profile grinding test was conducted on a novel single-crystal superalloy to simulate the formation of blade tenons,and the obtained tenons were characterized for surface integrity elements under various operating conditions.Results revealed that ultrasonic vibration-assisted grinding(UVAG)led to multiple superpositions of abrasive grain trajectories,causing reduced surface roughness(an average reduction of approximately29.6%)compared with conventional grinding.After examining the subsurface layer of UVAG using transmission electron microscopy,the results revealed that the single-crystal tenon grinding subsurface layer exhibited a gradient evolution from the near-surface to the substrate.This evolution was characterized by an equiaxed nanocrystalline layer measuring 0.34μm,followed by a submicrocrystalline grain-forming zone spanning 0.6μm and finally,a constituent phase-twisted dis-torted deformation zone over 0.62μm.Under normal grinding conditions,the tenon exhibited low surface hardening(not exceeding 15%),and residual compressive stresses were observed on its surface.In cases where grinding burns occurred,a white layer appeared on the tenon's surface,which demonstrated varying thicknesses along the teeth from top to root due to thermal-force-structural coupling effects.Additionally,these burns introduced residual tensile stresses on the tenon's surface,potentially substantially affecting its fatigue life.This paper enhances our understanding of UVAG processes and establishes a foundation for their application in manufacturing singlecrystal turbine blades for next-generation aero-turbine engines.
基金financially supported by the National Natural Science Foundation of China(Nos.92160301,92060203,52175415 and 52205475)the Science Center for Gas Turbine Project(Nos.P2022-AB-Ⅳ-002-001 and P2023-B-Ⅳ-003-001)+3 种基金the Jiangsu Key Laboratory of Precision and Micro-Manufacturing Technology(No.JSKL2223K01)the Natural Science Foundation of Jiangsu Province(No.BK20210295)the Superior Postdoctoral Project of Jiangsu Province(No.2022ZB215)the Henan Science and Technology Public Relations Project(No.212102210445).
文摘The undeformed chip thickness and grinding force are key parameters for revealing the material removal mechanism in the grinding process.However,they are difficult to be well expressed due to the ununiformed protrusion height and random position distribution of abrasive grains on the abrasive wheel surface.This study investigated the distribution of undeformed chip thickness and grinding force considering the non-uniform characteristics of abrasive wheel in the grinding of K4002 nickel-based superalloy.First,a novel grinding force model was established through a kinematic-geometric analysis and a grain-workpiece contact analysis.Then,a series of grinding experiments were conducted for verifying the model.The results indicate that the distribution of undeformed chip thickness is highly consistent with the Gaussian distribution formula.The increase in the grinding depth mainly leads to an increase in the average value of Gaussian distribution.On the contrary,the increase in the workpiece infeed speed or the decrease in the grinding speed mainly increases the standard deviation of Gaussian distribution.The average and maximum errors of the grinding force model are 4.9%and 14.6%respectively,indicating that the model is of high predication accuracy.
