To ensure the structural integrity of life-limiting component of aeroengines,Probabilistic Damage Tolerance(PDT)assessment is applied to evaluate the failure risk as required by airworthiness regulations and military ...To ensure the structural integrity of life-limiting component of aeroengines,Probabilistic Damage Tolerance(PDT)assessment is applied to evaluate the failure risk as required by airworthiness regulations and military standards.The PDT method holds the view that there exist defects such as machining scratches and service cracks in the tenon-groove structures of aeroengine disks.However,it is challenging to conduct PDT assessment due to the scarcity of effective Probability of Detection(POD)model and anomaly distribution model.Through a series of Nondestructive Testing(NDT)experiments,the POD model of real cracks in tenon-groove structures is constructed for the first time by employing the Transfer Function Method(TFM).A novel anomaly distribution model is derived through the utilization of the POD model,instead of using the infeasible field data accumulation method.Subsequently,a framework for calculating the Probability of Failure(POF)of the tenon-groove structures is established,and the aforementioned two models exert a significant influence on the results of POF.展开更多
A probability-based damage tolerance methodology has been proposed to improve the recognition of material anomalies, especially hard alpha(TiN) anomalies for aeroengine rotor disks. A key input to this method is hard ...A probability-based damage tolerance methodology has been proposed to improve the recognition of material anomalies, especially hard alpha(TiN) anomalies for aeroengine rotor disks. A key input to this method is hard alpha anomaly distribution, which reflects the occurrence rate and size of anomalies present in the finished part material of titanium rotors. Since anomalies rarely occur naturally, an experimental method is proposed to obtain the anomaly distribution for titanium alloy aeroengine disks to reflect and equivalently replace the manufacturing development in titanium industry. In general, the anomaly distribution information can be divided into two parts: the Probability of Detection(POD) curve and the detected anomaly distribution, which contains the size and frequency data of the detected anomalies. The distribution can be established based on several appropriate assumptions and derivation steps with different confidence levels of POD curves and detected anomaly distributions. In this case, the distribution can be obtained in a relatively short time as a key input to the probability-based damage tolerance methodology. Then the Probability of Failure(POF) can be calculated, and the value is found to vary with different confidence levels. On this basis, the conservative estimated POF can be obtained in conjunction with confidence levels.展开更多
Anomaly distribution is an essential input for the probabilistic damage tolerance assessment,which is required by the airworthiness certification criteria Federal Aviation Regulation(FAR)33.70.The default anomaly dist...Anomaly distribution is an essential input for the probabilistic damage tolerance assessment,which is required by the airworthiness certification criteria Federal Aviation Regulation(FAR)33.70.The default anomaly distribution of hole features has been established and published in airworthiness advisory circular 33.70-2 based on historical anomaly data collected from cracked or ruptured parts recorded in laboratory analysis reports of the special industries before 2005.However,for other industries,this default anomaly distribution fails to reflect the machining level of these industries.Besides,insufficient historical maintenance anomaly data makes the mathematical model of the default distribution inapplicable,and few models can deal with the production data.Therefore,this paper proposes a model for achieving the anomaly distribution of hole features induced by machine or maintenance process,including collecting anomaly data,deriving the exceedance number by the probability of detection(POD),conducting the curve fitting process,and calibrating and modifying the anomaly distribution.The anomaly distribution and the probability of failure(POF)are dependent on defect numbers as well as confidence levels.To recommend the number of collected data and the correction factor for the POFs with different sample numbers and confidence levels,the sensitivity analysis is conducted by quantifying the influence of the anomaly distributions of different anomaly numbers on the POFs.Results show that when the anomaly number is 25,the differences between the POFs are less than 32.9%,and a 1.329 correction factor zP is supposed to modify the POF.When the anomaly number is larger than 50,a 1.2 correction factor zP is supposed to obtain the most conservative risk value with a 95%confidence level.展开更多
Anomaly detection plays an important role in ensuring the data quality in wireless sensor networks(WSNs).The main objective of the paper is to design a light-weight and distributed algorithm to detect the data collect...Anomaly detection plays an important role in ensuring the data quality in wireless sensor networks(WSNs).The main objective of the paper is to design a light-weight and distributed algorithm to detect the data collected from WSNs effectively.This is achieved by proposing a distributed anomaly detection algorithm based on ensemble isolation principle.The new method offers distinctive advantages over the existing methods.Firstly,it does not require any distance or density measurement,which reduces computational burdens significantly.Secondly,considering the spatial correlation characteristic of node deployment in WSNs,local sub-detector is built in each sensor node,which is broadcasted simultaneously to neighbor sensor nodes.A global detector model is then constructed by using the local detector model and the neighbor detector model,which possesses a distributed nature and decreases communication burden.The experiment results on the labeled dataset confirm the effectiveness of the proposed method.展开更多
Geological anomaly is a geological body or geological body combination different from its surroundings in composition, structure, or genetic sequence. If there is a value (value interval ) that works as a valve repres...Geological anomaly is a geological body or geological body combination different from its surroundings in composition, structure, or genetic sequence. If there is a value (value interval ) that works as a valve representing the background field, exceeding or lower than the valve value,it is called a geological anomaly. Geological anomalies can be divided into high geological anomaly and low geological anomaly .The former shows the area that is more complex in composition, Structure or genetic sequence than its surroundings; while the latter just gives an opposite indication, i. e. much simpler. According to their distribution and delimitation markers, geological anomalies can be classified into (1)global geological anomaly; (2)regional geological anomaly; (3) local geological anomaly; (4) minor geological anomaly and (5)micro-geological anomaly .The methods for delimiting geological anomalies include (1)crustal elevation-subsidence coefficieat (G value ) determination; (2) geological complex coefficient (C value ) determination; (3) entropy (H value ) determination; (4) geological similarity coefficient (S value ) determination and (5 ) geological correlation coefficient (R value ) determination. As the result of the movements of Eurasian, Pacific and Indian Plates, the Chinese geological anomalies, including 11 regional ones and 32 main local ones, most Paleozoic in age, are distributed in strip on the margin or the outer and inner folded zones in the east and west arcs of the block symmetric arc tectonic system (BSATS), which controls the distribution of various minerals in China. Thus, geological anomaly theory is of great significance in searching for large, super-large and very large ore deposits.展开更多
Probabilistic damage tolerance is a critical method to understand and communicate risk and safety.This paper reviews recent research on the probabilistic damage tolerance design for life-limited parts.The vision of th...Probabilistic damage tolerance is a critical method to understand and communicate risk and safety.This paper reviews recent research on the probabilistic damage tolerance design for life-limited parts.The vision of the probabilistic damage tolerance assessment is provided.Five core parts of the probabilistic damage tolerance method are introduced separately,including the anomaly distribution,stress processing and zone definition,fatigue and fracture calculation method,probability of failure(POF)calculation method,and the combination with residual stress induced by the manufacturing process.The above currently-available risk assessment methods provide practical tools for failure risk predictions and are applied by the airworthiness regulations.However,new problems are exposed with the development of the aeroengines.The time-consuming anomaly distribution derivation process restricts the development of the anomaly distribution,especially for the developing aviation industries with little empirical data.Additionally,the strong transient characteristic is prominent because of the significant temperature differences during the take-off and climbing periods.The complex loads then challenge the fatigue and fracture calculation model.Besides,high computational efficiency is required because various variables are considered to calculate the POF.Therefore,new technologies for the probabilistic damage tolerance assessment are provided,including the efficient anomaly distribution acquisition method based on small samples,the zone definition method considering transient process,and stress intensity factor(SIF)solutions under arbitrary stress distributions combined with the machine learning method.Then,an efficient numerical integration method for calculating failure risk based on the probability density evolution theory is proposed.Meanwhile,the influence of the manufacturing process on residual stress and the failure risk of the rotors is explored.The development of the probabilistic damage tolerance method can meet the requirement of the published airworthiness regulation Federal Aviation Regulation(FAR)33.70 and guide the modification or amendment of new regulations to ensure the safety of the high-energy rotors.展开更多
In this paper,a three-dimensional EOF technique is used to analyze the precipitation and its anomaly over whole China and sanely selected regions,i.e.the Changjiang Valley,the Huanghe Valley and the South part of Chin...In this paper,a three-dimensional EOF technique is used to analyze the precipitation and its anomaly over whole China and sanely selected regions,i.e.the Changjiang Valley,the Huanghe Valley and the South part of China in last decades.The structural characteristics of spacial distribution,seasonal and interannual variation are revealed.As a better technique than 2-D EOF,the 3-D EOF alse provides a way to expose interac- tions between temporal and spacial variations.展开更多
基金supported by the National Major Science and Technology Project,China(No.J2019-Ⅳ-0007-0075)the Fundamental Research Funds for the Central Universities,China(No.JKF-20240036)。
文摘To ensure the structural integrity of life-limiting component of aeroengines,Probabilistic Damage Tolerance(PDT)assessment is applied to evaluate the failure risk as required by airworthiness regulations and military standards.The PDT method holds the view that there exist defects such as machining scratches and service cracks in the tenon-groove structures of aeroengine disks.However,it is challenging to conduct PDT assessment due to the scarcity of effective Probability of Detection(POD)model and anomaly distribution model.Through a series of Nondestructive Testing(NDT)experiments,the POD model of real cracks in tenon-groove structures is constructed for the first time by employing the Transfer Function Method(TFM).A novel anomaly distribution model is derived through the utilization of the POD model,instead of using the infeasible field data accumulation method.Subsequently,a framework for calculating the Probability of Failure(POF)of the tenon-groove structures is established,and the aforementioned two models exert a significant influence on the results of POF.
基金funded by the National Natural Science Foundation of China and Civil Aviation Administration of China(No.U1833109)the Innovation Team of Complex System Safety and Airworthiness of Aero Engine from the Co-Innovation Center for Advanced Aeroengine of China。
文摘A probability-based damage tolerance methodology has been proposed to improve the recognition of material anomalies, especially hard alpha(TiN) anomalies for aeroengine rotor disks. A key input to this method is hard alpha anomaly distribution, which reflects the occurrence rate and size of anomalies present in the finished part material of titanium rotors. Since anomalies rarely occur naturally, an experimental method is proposed to obtain the anomaly distribution for titanium alloy aeroengine disks to reflect and equivalently replace the manufacturing development in titanium industry. In general, the anomaly distribution information can be divided into two parts: the Probability of Detection(POD) curve and the detected anomaly distribution, which contains the size and frequency data of the detected anomalies. The distribution can be established based on several appropriate assumptions and derivation steps with different confidence levels of POD curves and detected anomaly distributions. In this case, the distribution can be obtained in a relatively short time as a key input to the probability-based damage tolerance methodology. Then the Probability of Failure(POF) can be calculated, and the value is found to vary with different confidence levels. On this basis, the conservative estimated POF can be obtained in conjunction with confidence levels.
基金funded by the National Natural Science Foundation of China,grant number U2233213The work was supported by the Innovation Team of Complex System Safety and Airworthiness of Aero Engine from the Co-Innovation Center for Advanced Aero-engine of ChinaIn addition,the authors wish to thank the financial support of the Tianmushan Laboratory(Laboratory of Aviation in Zhejiang Province),Hangzhou,China.
文摘Anomaly distribution is an essential input for the probabilistic damage tolerance assessment,which is required by the airworthiness certification criteria Federal Aviation Regulation(FAR)33.70.The default anomaly distribution of hole features has been established and published in airworthiness advisory circular 33.70-2 based on historical anomaly data collected from cracked or ruptured parts recorded in laboratory analysis reports of the special industries before 2005.However,for other industries,this default anomaly distribution fails to reflect the machining level of these industries.Besides,insufficient historical maintenance anomaly data makes the mathematical model of the default distribution inapplicable,and few models can deal with the production data.Therefore,this paper proposes a model for achieving the anomaly distribution of hole features induced by machine or maintenance process,including collecting anomaly data,deriving the exceedance number by the probability of detection(POD),conducting the curve fitting process,and calibrating and modifying the anomaly distribution.The anomaly distribution and the probability of failure(POF)are dependent on defect numbers as well as confidence levels.To recommend the number of collected data and the correction factor for the POFs with different sample numbers and confidence levels,the sensitivity analysis is conducted by quantifying the influence of the anomaly distributions of different anomaly numbers on the POFs.Results show that when the anomaly number is 25,the differences between the POFs are less than 32.9%,and a 1.329 correction factor zP is supposed to modify the POF.When the anomaly number is larger than 50,a 1.2 correction factor zP is supposed to obtain the most conservative risk value with a 95%confidence level.
基金supported by the National High Technology Research and Development Program of China(No.2011AA040103-7)the National Key Scientific Instrument and Equipment Development Project(No.2012YQ15008703)+3 种基金the Zhejiang Provincial Natural Science Foundation of China(No.LY13F020015)National Science Foundation of China(No.61104089)Science and Technology Commission of Shanghai Municipality(No.11JC1404000)Shanghai Rising-Star Program(No.13QA1401600)
文摘Anomaly detection plays an important role in ensuring the data quality in wireless sensor networks(WSNs).The main objective of the paper is to design a light-weight and distributed algorithm to detect the data collected from WSNs effectively.This is achieved by proposing a distributed anomaly detection algorithm based on ensemble isolation principle.The new method offers distinctive advantages over the existing methods.Firstly,it does not require any distance or density measurement,which reduces computational burdens significantly.Secondly,considering the spatial correlation characteristic of node deployment in WSNs,local sub-detector is built in each sensor node,which is broadcasted simultaneously to neighbor sensor nodes.A global detector model is then constructed by using the local detector model and the neighbor detector model,which possesses a distributed nature and decreases communication burden.The experiment results on the labeled dataset confirm the effectiveness of the proposed method.
文摘Geological anomaly is a geological body or geological body combination different from its surroundings in composition, structure, or genetic sequence. If there is a value (value interval ) that works as a valve representing the background field, exceeding or lower than the valve value,it is called a geological anomaly. Geological anomalies can be divided into high geological anomaly and low geological anomaly .The former shows the area that is more complex in composition, Structure or genetic sequence than its surroundings; while the latter just gives an opposite indication, i. e. much simpler. According to their distribution and delimitation markers, geological anomalies can be classified into (1)global geological anomaly; (2)regional geological anomaly; (3) local geological anomaly; (4) minor geological anomaly and (5)micro-geological anomaly .The methods for delimiting geological anomalies include (1)crustal elevation-subsidence coefficieat (G value ) determination; (2) geological complex coefficient (C value ) determination; (3) entropy (H value ) determination; (4) geological similarity coefficient (S value ) determination and (5 ) geological correlation coefficient (R value ) determination. As the result of the movements of Eurasian, Pacific and Indian Plates, the Chinese geological anomalies, including 11 regional ones and 32 main local ones, most Paleozoic in age, are distributed in strip on the margin or the outer and inner folded zones in the east and west arcs of the block symmetric arc tectonic system (BSATS), which controls the distribution of various minerals in China. Thus, geological anomaly theory is of great significance in searching for large, super-large and very large ore deposits.
基金the National Natural Science Foundation of China,grant number U2233213.
文摘Probabilistic damage tolerance is a critical method to understand and communicate risk and safety.This paper reviews recent research on the probabilistic damage tolerance design for life-limited parts.The vision of the probabilistic damage tolerance assessment is provided.Five core parts of the probabilistic damage tolerance method are introduced separately,including the anomaly distribution,stress processing and zone definition,fatigue and fracture calculation method,probability of failure(POF)calculation method,and the combination with residual stress induced by the manufacturing process.The above currently-available risk assessment methods provide practical tools for failure risk predictions and are applied by the airworthiness regulations.However,new problems are exposed with the development of the aeroengines.The time-consuming anomaly distribution derivation process restricts the development of the anomaly distribution,especially for the developing aviation industries with little empirical data.Additionally,the strong transient characteristic is prominent because of the significant temperature differences during the take-off and climbing periods.The complex loads then challenge the fatigue and fracture calculation model.Besides,high computational efficiency is required because various variables are considered to calculate the POF.Therefore,new technologies for the probabilistic damage tolerance assessment are provided,including the efficient anomaly distribution acquisition method based on small samples,the zone definition method considering transient process,and stress intensity factor(SIF)solutions under arbitrary stress distributions combined with the machine learning method.Then,an efficient numerical integration method for calculating failure risk based on the probability density evolution theory is proposed.Meanwhile,the influence of the manufacturing process on residual stress and the failure risk of the rotors is explored.The development of the probabilistic damage tolerance method can meet the requirement of the published airworthiness regulation Federal Aviation Regulation(FAR)33.70 and guide the modification or amendment of new regulations to ensure the safety of the high-energy rotors.
文摘In this paper,a three-dimensional EOF technique is used to analyze the precipitation and its anomaly over whole China and sanely selected regions,i.e.the Changjiang Valley,the Huanghe Valley and the South part of China in last decades.The structural characteristics of spacial distribution,seasonal and interannual variation are revealed.As a better technique than 2-D EOF,the 3-D EOF alse provides a way to expose interac- tions between temporal and spacial variations.
