Multi-constrained pipes conveying fluid,such as aircraft hydraulic control pipes,are susceptible to resonance fatigue in harsh vibration environments,which may lead to system failure and even catastrophic accidents.In...Multi-constrained pipes conveying fluid,such as aircraft hydraulic control pipes,are susceptible to resonance fatigue in harsh vibration environments,which may lead to system failure and even catastrophic accidents.In this study,a machine learning(ML)-assisted weak vibration design method under harsh environmental excitations is proposed.The dynamic model of a typical pipe is developed using the absolute nodal coordinate formulation(ANCF)to determine its vibrational characteristics.With the harsh vibration environments as the preserved frequency band(PFB),the safety design is defined by comparing the natural frequency with the PFB.By analyzing the safety design of pipes with different constraint parameters,the dataset of the absolute safety length and the absolute resonance length of the pipe is obtained.This dataset is then utilized to develop genetic programming(GP)algorithm-based ML models capable of producing explicit mathematical expressions of the pipe's absolute safety length and absolute resonance length with the location,stiffness,and total number of retaining clips as design variables.The proposed ML models effectively bridge the dataset with the prediction results.Thus,the ML model is utilized to stagger the natural frequency,and the PFB is utilized to achieve the weak vibration design.The findings of the present study provide valuable insights into the practical application of weak vibration design.展开更多
With the advancement of more electric aircraft(MEA)technology,the application of electro-hydrostatic actuators(EHAs)in aircraft actuation systems has become increasingly prevalent.This paper focuses on the modeling an...With the advancement of more electric aircraft(MEA)technology,the application of electro-hydrostatic actuators(EHAs)in aircraft actuation systems has become increasingly prevalent.This paper focuses on the modeling and mode switching analysis of EHA used in the primary flight control actuation systems of large aircraft,addressing the challenges associated with mode switching.First,we analyze the functional architecture and operational characteristics of multi-mode EHA,and sumarize the operating modes and implementation methods.Based on the EHA system architecture,we then develop a theoretical mathematical model and a simulation model.Using the simulation model,we analyze the performance of the EHA during normal operation.Finally,the performance of the EHA during mode switching under various functional switching scenarios is investigated.The results indicate that the EHA meets the performance requirements in terms of accuracy,bandwidth,and load capacity.Additionally,the hydraulic cylinder operates smoothly during the EHA mode switching,and the response time for switching between different modes is less than the specified threshold.These findings validate the system performance of multi-mode EHA,which helps to improve the reliability of EHA and the safety of aircraft flight control systems.展开更多
The cylinder block/valve plate interface is one of the most critical frictional interfaces of the swashplate-type axial piston pump.However,the poor lubrication interface caused rapid wear and high friction loss in an...The cylinder block/valve plate interface is one of the most critical frictional interfaces of the swashplate-type axial piston pump.However,the poor lubrication interface caused rapid wear and high friction loss in an elastohydrodynamic lubrication system,decreasing the pump lifetime.Wear resistant bronze coatings were fabricated on 38CrMoAl substrate by Physical Vapor Deposition(PVD)and Chemical Vapor Deposition(CVD),respectively.Ball-on-disc wear tests were performed to comparatively investigate the wear behaviors of the coatings and bulk ductile iron samples.It can be found that the PVD-bronze coating exhibited better wear resistance than the other two samples.This enhanced wear resistance was attributed to the unique composite microstructure and desired mechanical strength,which could resist to mechanical shear and spallation,decreasing friction loss.The appropriate hardness of(1.33±0.07)GPa could be beneficial for enhancing its wear resistance.The PVD-bronze coating possessed a much lower and stable coefficient of friction(about 0.1)and wear rate(about 6000μm3.N-1.m-1)under the loading forces of about 100 N after 20 min.The wear mechanism was the abrasive wear.展开更多
基金Project supported by the Foundation for Innovative Research Groups of the National Natural Science Foundation of China(No.12421002)the National Science Funds for Distinguished Young Scholars of China(No.12025204)+1 种基金the National Natural Science Foundation of China(No.12372015)China Scholarship Council(No.202206890065)。
文摘Multi-constrained pipes conveying fluid,such as aircraft hydraulic control pipes,are susceptible to resonance fatigue in harsh vibration environments,which may lead to system failure and even catastrophic accidents.In this study,a machine learning(ML)-assisted weak vibration design method under harsh environmental excitations is proposed.The dynamic model of a typical pipe is developed using the absolute nodal coordinate formulation(ANCF)to determine its vibrational characteristics.With the harsh vibration environments as the preserved frequency band(PFB),the safety design is defined by comparing the natural frequency with the PFB.By analyzing the safety design of pipes with different constraint parameters,the dataset of the absolute safety length and the absolute resonance length of the pipe is obtained.This dataset is then utilized to develop genetic programming(GP)algorithm-based ML models capable of producing explicit mathematical expressions of the pipe's absolute safety length and absolute resonance length with the location,stiffness,and total number of retaining clips as design variables.The proposed ML models effectively bridge the dataset with the prediction results.Thus,the ML model is utilized to stagger the natural frequency,and the PFB is utilized to achieve the weak vibration design.The findings of the present study provide valuable insights into the practical application of weak vibration design.
基金supported by the Chinese Civil Aircraft Project(No.MJ-2017-S49).
文摘With the advancement of more electric aircraft(MEA)technology,the application of electro-hydrostatic actuators(EHAs)in aircraft actuation systems has become increasingly prevalent.This paper focuses on the modeling and mode switching analysis of EHA used in the primary flight control actuation systems of large aircraft,addressing the challenges associated with mode switching.First,we analyze the functional architecture and operational characteristics of multi-mode EHA,and sumarize the operating modes and implementation methods.Based on the EHA system architecture,we then develop a theoretical mathematical model and a simulation model.Using the simulation model,we analyze the performance of the EHA during normal operation.Finally,the performance of the EHA during mode switching under various functional switching scenarios is investigated.The results indicate that the EHA meets the performance requirements in terms of accuracy,bandwidth,and load capacity.Additionally,the hydraulic cylinder operates smoothly during the EHA mode switching,and the response time for switching between different modes is less than the specified threshold.These findings validate the system performance of multi-mode EHA,which helps to improve the reliability of EHA and the safety of aircraft flight control systems.
基金supported by the Key Research and Development Program of Zhejiang Province,China(Nos.2020C01153,2022C01139)。
文摘The cylinder block/valve plate interface is one of the most critical frictional interfaces of the swashplate-type axial piston pump.However,the poor lubrication interface caused rapid wear and high friction loss in an elastohydrodynamic lubrication system,decreasing the pump lifetime.Wear resistant bronze coatings were fabricated on 38CrMoAl substrate by Physical Vapor Deposition(PVD)and Chemical Vapor Deposition(CVD),respectively.Ball-on-disc wear tests were performed to comparatively investigate the wear behaviors of the coatings and bulk ductile iron samples.It can be found that the PVD-bronze coating exhibited better wear resistance than the other two samples.This enhanced wear resistance was attributed to the unique composite microstructure and desired mechanical strength,which could resist to mechanical shear and spallation,decreasing friction loss.The appropriate hardness of(1.33±0.07)GPa could be beneficial for enhancing its wear resistance.The PVD-bronze coating possessed a much lower and stable coefficient of friction(about 0.1)and wear rate(about 6000μm3.N-1.m-1)under the loading forces of about 100 N after 20 min.The wear mechanism was the abrasive wear.
