A methodology is developed based on the coupling of a finite element code with an optimisation module for the design of land vehicle armouring composed of lightweight aluminium alloy and high strength steel plate.Foll...A methodology is developed based on the coupling of a finite element code with an optimisation module for the design of land vehicle armouring composed of lightweight aluminium alloy and high strength steel plate.Following an experiment/simulation correlation,a numerical model has been built and calibrated considering monolithic plates and then verified considering a bi-metal protection against tungsten carbide projectile mimicking the core of a 7.62×51 AP8 ammunition.In addition,a method is proposed to obtain the v_(res)-v_(i) curve for the full 7.62×51 AP8 bullet from the v_(res)-v_(i) curve obtained from the core only.展开更多
This paper proposes a numerical method to analyze the ice protection capability and predict the power requirements of a piezoelectric resonant de-icing system.The method is based on a coupled electro-mechanical finite...This paper proposes a numerical method to analyze the ice protection capability and predict the power requirements of a piezoelectric resonant de-icing system.The method is based on a coupled electro-mechanical finite element analysis which enables the fast computation of the modes of resonance of interest to de-ice curved surfaces and the estimation of the input voltage and current required for a given configuration(defined by its mode,actuator location,ice deposit,etc.).Eventually,the electric power to be supplied can be also assessed.The method is applied to a NACA 0024 leading edge equipped with piezoelectric actuators.First,two extension modes are analyzed and compared with respect to their efficiency and power requirements.Then,tests are carried out in an icing tunnel to verify the effectiveness of the piezoelectric ice protection system and the predictions of the maximal required power.The system allows de-icing the leading edge in less than 2 s for a glaze ice deposit.展开更多
Piezoelectric resonant de-icing systems are attracting great interest.This paper aims to assess the implementation of these systems at the aircraft level.The article begins with the model to compute the power requirem...Piezoelectric resonant de-icing systems are attracting great interest.This paper aims to assess the implementation of these systems at the aircraft level.The article begins with the model to compute the power requirement of a piezoelectric resonant de-icing system sized from the prototype detailed in Part 1/2 of this article.Then the mass,drag,and fuel consumption of this system and the subcomponents needed for its implementation are assessed.The features of a piezoelectric resonant de-icing system are finally computed for aircraft similar to Airbus A320 aircraft and aircraft of different categories(Boeing 787,ATR 72 and TBM 900)and compared with the existing thermal and mechanical ice protection systems.A sensitivity analysis of the main key sizing parameters of the piezoelectric de-icing system is also performed to identify the main axes of improvement for this technology.The study shows the potential of such ice protection systems.In particular,for the realistic input parameters chosen in this work,the electro-mechanical solution can provide a 54% reduction in terms of mass and a 92% reduction in terms of power consumption for an A320 aircraft architecture,leading to a 74% decrease in the associated fuel consumption compared to the actual air bleed system.展开更多
The tribo-characteristics of metal forming at high temperatures have not yet been well understood due to the complex nature of thermal,microstructural,interaction,and process parameters.This is a review paper on the e...The tribo-characteristics of metal forming at high temperatures have not yet been well understood due to the complex nature of thermal,microstructural,interaction,and process parameters.This is a review paper on the effects of temperature,coating,and lubrication to the tribological characteristics in hot forming as well as the tribometers for different metal forming processes at elevated temperatures mainly based on the experimental work.The tribological behaviors of oxides in hot forming,such as rolling and stamping,were reviewed and presented.Some commonly used surface coatings and lubricants in hot forming were given.Many types of tribometer were selected and presented and some of them provided a great potential to characterize friction and wear at elevated temperatures.Nevertheless,more testing conditions should be further investigated by developing new tribometers.Eventually,experimental results obtained from reliable tribometers could be used in theory and model developments for different forming processes and materials at high temperatures.The review also showed the great potential in further investigations and innovation in tribology.展开更多
This paper proposes a model-based prognostics method that couples the Extended Kalman Filter(EKF) and a new developed linearization method. The proposed prognostics method is developed in the context of fatigue crack ...This paper proposes a model-based prognostics method that couples the Extended Kalman Filter(EKF) and a new developed linearization method. The proposed prognostics method is developed in the context of fatigue crack propagation in fuselage panels where the model parameters are unknown and the crack propagation is affected by different types of uncertainties. The coupled method is composed of two steps. The first step employs EKF to estimate the unknown model parameters and the current damage state. In the second step, the proposed efficient linearization method is applied to compute analytically the statistical distribution of the damage evolution path in some future time. A numerical case study is implemented to evaluate the performance of the proposed method. The results show that the coupled EKF-linearization method provides satisfactory results: the EKF algorithm well identifies the model parameters, and the linearization method gives comparable prediction results to Monte Carlo(MC) method while leading to very significant computational cost saving. The proposed prognostics method for fatigue crack growth can be used for developing predictive maintenance strategy for an aircraft fleet, in which case, the computational cost saving is significantly meaningful.展开更多
In order to improve the knowledge of the precipitation mechanism in martensitic steels containing carbon,XRD synchrotron experiments were performed. Firstly, the influence of Ni,Co and Al were studied and it was found...In order to improve the knowledge of the precipitation mechanism in martensitic steels containing carbon,XRD synchrotron experiments were performed. Firstly, the influence of Ni,Co and Al were studied and it was found that the precipitation of iron carbides occurs in same way as in Fe-C steel. However, with the addition of molybdenum and chromium in same steels, XRD synchrotron investigations clearly showed alloyed carbides directly precipitate, thereby preventing the iron carbides formation.展开更多
A finite element analysis of stress intensity factors （KI） in clamped SE（T）c specimens （dog bone profile） is presented. A J-integral approach is used to calculate the values of stress intensity factors valid for...A finite element analysis of stress intensity factors （KI） in clamped SE（T）c specimens （dog bone profile） is presented. A J-integral approach is used to calculate the values of stress intensity factors valid for 0.125≤a/W≤0.625. A detailed comparison is made with the work of other researchers on rectangular specimens. Different boundary conditions are explored to best describe the real conditions in the laboratory. A sensitivity study is also presented to explore the effects of variation in specimen position in the grips of the testing machine. Finally the numerically calculated SIF is used to determine an FCGR curve for AISI Hll tool steel on SE（T）c specimens and compared with C（T） specimen of the same material.展开更多
The continuous growth in the manufacture of aerospace components such as blisks has led to an increase in the application of different hybrid materials fabricating methods,and thus the requirements for joining and str...The continuous growth in the manufacture of aerospace components such as blisks has led to an increase in the application of different hybrid materials fabricating methods,and thus the requirements for joining and strengthening of dissimilar welds.According to this goal,selective laser melted(SLM)Inconel718 was joined with forged AD730^(TM)Nickel-based superalloy through linear friction welding(LFW)in this study.Microstructure variation,specifically with respect to secondary phases precipitation was investigated.The microhardness and strengthening mechanisms of the weldment were also studied.The precipitation(volume fraction and size of particles)at different regions of both sides of the weld line was characterized.Close to the weld line,the dissolution ofγ’/γ"and Laves phases and grain refinement occurred which reveals the effects of both compression strain and high temperature on recrystallization and high degree of elemental diffusion in the weld zone(WZ).It is shown that the size,volume fraction,and shape of secondary phases increased and changed(from spherical to long-striped for Laves particles)as we went from the WZ toward the base metal.However,the measured microhardness indicated that the strength of AD730^(TM)alloy depends significantly on the grain size,while strength in SLM Inconel 718 was dominated by shape(or size)and the presence of secondary phases(γ’/γ"and Laves).展开更多
Airframe maintenance is traditionally performed at scheduled maintenance stops.The decision to repair a fuselage panel is based on a fixed crack size threshold,which allows to ensure the aircraft safety until the next...Airframe maintenance is traditionally performed at scheduled maintenance stops.The decision to repair a fuselage panel is based on a fixed crack size threshold,which allows to ensure the aircraft safety until the next scheduled maintenance stop.With progress in sensor technology and data processing techniques,structural health monitoring（SHM） systems are increasingly being considered in the aviation industry.SHM systems track the aircraft health state continuously,leading to the possibility of planning maintenance based on an actual state of aircraft rather than on a fixed schedule.This paper builds upon a model-based prognostics framework that the authors developed in their previous work,which couples the Extended Kalman filter（EKF） with a firstorder perturbation（FOP） method.By using the information given by this prognostics method,a novel cost driven predictive maintenance（CDPM） policy is proposed,which ensures the aircraft safety while minimizing the maintenance cost.The proposed policy is formally derived based on the trade-off between probabilities of occurrence of scheduled and unscheduled maintenance.A numerical case study simulating the maintenance process of an entire fleet of aircrafts is implemented.Under the condition of assuring the same safety level,the CDPM is compared in terms of cost with two other maintenance policies：scheduled maintenance and threshold based SHM maintenance.The comparison results show CDPM could lead to significant cost savings.展开更多
基金partly supported by the French Association Nationale de la Recherche et de la Technologie,ANRT (Grant No.2018/0299)。
文摘A methodology is developed based on the coupling of a finite element code with an optimisation module for the design of land vehicle armouring composed of lightweight aluminium alloy and high strength steel plate.Following an experiment/simulation correlation,a numerical model has been built and calibrated considering monolithic plates and then verified considering a bi-metal protection against tungsten carbide projectile mimicking the core of a 7.62×51 AP8 ammunition.In addition,a method is proposed to obtain the v_(res)-v_(i) curve for the full 7.62×51 AP8 bullet from the v_(res)-v_(i) curve obtained from the core only.
文摘This paper proposes a numerical method to analyze the ice protection capability and predict the power requirements of a piezoelectric resonant de-icing system.The method is based on a coupled electro-mechanical finite element analysis which enables the fast computation of the modes of resonance of interest to de-ice curved surfaces and the estimation of the input voltage and current required for a given configuration(defined by its mode,actuator location,ice deposit,etc.).Eventually,the electric power to be supplied can be also assessed.The method is applied to a NACA 0024 leading edge equipped with piezoelectric actuators.First,two extension modes are analyzed and compared with respect to their efficiency and power requirements.Then,tests are carried out in an icing tunnel to verify the effectiveness of the piezoelectric ice protection system and the predictions of the maximal required power.The system allows de-icing the leading edge in less than 2 s for a glaze ice deposit.
文摘Piezoelectric resonant de-icing systems are attracting great interest.This paper aims to assess the implementation of these systems at the aircraft level.The article begins with the model to compute the power requirement of a piezoelectric resonant de-icing system sized from the prototype detailed in Part 1/2 of this article.Then the mass,drag,and fuel consumption of this system and the subcomponents needed for its implementation are assessed.The features of a piezoelectric resonant de-icing system are finally computed for aircraft similar to Airbus A320 aircraft and aircraft of different categories(Boeing 787,ATR 72 and TBM 900)and compared with the existing thermal and mechanical ice protection systems.A sensitivity analysis of the main key sizing parameters of the piezoelectric de-icing system is also performed to identify the main axes of improvement for this technology.The study shows the potential of such ice protection systems.In particular,for the realistic input parameters chosen in this work,the electro-mechanical solution can provide a 54% reduction in terms of mass and a 92% reduction in terms of power consumption for an A320 aircraft architecture,leading to a 74% decrease in the associated fuel consumption compared to the actual air bleed system.
文摘The tribo-characteristics of metal forming at high temperatures have not yet been well understood due to the complex nature of thermal,microstructural,interaction,and process parameters.This is a review paper on the effects of temperature,coating,and lubrication to the tribological characteristics in hot forming as well as the tribometers for different metal forming processes at elevated temperatures mainly based on the experimental work.The tribological behaviors of oxides in hot forming,such as rolling and stamping,were reviewed and presented.Some commonly used surface coatings and lubricants in hot forming were given.Many types of tribometer were selected and presented and some of them provided a great potential to characterize friction and wear at elevated temperatures.Nevertheless,more testing conditions should be further investigated by developing new tribometers.Eventually,experimental results obtained from reliable tribometers could be used in theory and model developments for different forming processes and materials at high temperatures.The review also showed the great potential in further investigations and innovation in tribology.
基金partially funded by the National Natural Science Foundation of China (No.51805262)
文摘This paper proposes a model-based prognostics method that couples the Extended Kalman Filter(EKF) and a new developed linearization method. The proposed prognostics method is developed in the context of fatigue crack propagation in fuselage panels where the model parameters are unknown and the crack propagation is affected by different types of uncertainties. The coupled method is composed of two steps. The first step employs EKF to estimate the unknown model parameters and the current damage state. In the second step, the proposed efficient linearization method is applied to compute analytically the statistical distribution of the damage evolution path in some future time. A numerical case study is implemented to evaluate the performance of the proposed method. The results show that the coupled EKF-linearization method provides satisfactory results: the EKF algorithm well identifies the model parameters, and the linearization method gives comparable prediction results to Monte Carlo(MC) method while leading to very significant computational cost saving. The proposed prognostics method for fatigue crack growth can be used for developing predictive maintenance strategy for an aircraft fleet, in which case, the computational cost saving is significantly meaningful.
文摘In order to improve the knowledge of the precipitation mechanism in martensitic steels containing carbon,XRD synchrotron experiments were performed. Firstly, the influence of Ni,Co and Al were studied and it was found that the precipitation of iron carbides occurs in same way as in Fe-C steel. However, with the addition of molybdenum and chromium in same steels, XRD synchrotron investigations clearly showed alloyed carbides directly precipitate, thereby preventing the iron carbides formation.
文摘A finite element analysis of stress intensity factors （KI） in clamped SE（T）c specimens （dog bone profile） is presented. A J-integral approach is used to calculate the values of stress intensity factors valid for 0.125≤a/W≤0.625. A detailed comparison is made with the work of other researchers on rectangular specimens. Different boundary conditions are explored to best describe the real conditions in the laboratory. A sensitivity study is also presented to explore the effects of variation in specimen position in the grips of the testing machine. Finally the numerically calculated SIF is used to determine an FCGR curve for AISI Hll tool steel on SE（T）c specimens and compared with C（T） specimen of the same material.
基金The authors gratefully acknowledge the support from the Natural Sciences and Engineering Research Council of Canada(NSERC)2018–03889 through a Discovery Grant.Thanks to Mr.Adrien Lieurey(IMT-Mines Albi ICA-site Albi)for his involvement and fabrication of SLM parts.They would also like to express their gratitude to Aubert&Duval Co.,Dr.Alexandre Devaux,and Prof.Cormier for providing forged AD730™samples and discussions on the definition of the scope of the project.Special thanks to TWI Ltd.for carrying out the LFW of the samples.
文摘The continuous growth in the manufacture of aerospace components such as blisks has led to an increase in the application of different hybrid materials fabricating methods,and thus the requirements for joining and strengthening of dissimilar welds.According to this goal,selective laser melted(SLM)Inconel718 was joined with forged AD730^(TM)Nickel-based superalloy through linear friction welding(LFW)in this study.Microstructure variation,specifically with respect to secondary phases precipitation was investigated.The microhardness and strengthening mechanisms of the weldment were also studied.The precipitation(volume fraction and size of particles)at different regions of both sides of the weld line was characterized.Close to the weld line,the dissolution ofγ’/γ"and Laves phases and grain refinement occurred which reveals the effects of both compression strain and high temperature on recrystallization and high degree of elemental diffusion in the weld zone(WZ).It is shown that the size,volume fraction,and shape of secondary phases increased and changed(from spherical to long-striped for Laves particles)as we went from the WZ toward the base metal.However,the measured microhardness indicated that the strength of AD730^(TM)alloy depends significantly on the grain size,while strength in SLM Inconel 718 was dominated by shape(or size)and the presence of secondary phases(γ’/γ"and Laves).
基金supported by UT-INSA Program(2013)the support of the China Scholarship Council(CSC)
文摘Airframe maintenance is traditionally performed at scheduled maintenance stops.The decision to repair a fuselage panel is based on a fixed crack size threshold,which allows to ensure the aircraft safety until the next scheduled maintenance stop.With progress in sensor technology and data processing techniques,structural health monitoring（SHM） systems are increasingly being considered in the aviation industry.SHM systems track the aircraft health state continuously,leading to the possibility of planning maintenance based on an actual state of aircraft rather than on a fixed schedule.This paper builds upon a model-based prognostics framework that the authors developed in their previous work,which couples the Extended Kalman filter（EKF） with a firstorder perturbation（FOP） method.By using the information given by this prognostics method,a novel cost driven predictive maintenance（CDPM） policy is proposed,which ensures the aircraft safety while minimizing the maintenance cost.The proposed policy is formally derived based on the trade-off between probabilities of occurrence of scheduled and unscheduled maintenance.A numerical case study simulating the maintenance process of an entire fleet of aircrafts is implemented.Under the condition of assuring the same safety level,the CDPM is compared in terms of cost with two other maintenance policies：scheduled maintenance and threshold based SHM maintenance.The comparison results show CDPM could lead to significant cost savings.
