Transactions of Nanjing University of Aeronautics & Astronautics
Volume 34,Issue 3,2017 Table of Contents
2017, 34(3):229-246.
DOI: 10.16356/j.1005-1120.2017.03.229
Abstract:
The scope of this paper is to provide an E2E perspective of health monitoring and management (HMM) and structural health mornitoring (SHM) as an integrated system element of a n integrated system health monitoring and management (ISHM) system. The paper will address two main topics: (1) The importance of a diagnostics and prognostic requirements specification to develop an innovative health monitoring and ma nagement system; (2) The certification of a health monitoring and management system aiming at a maintenance credit as an integral part of the maintenance strategies. The development of a maintenance program which is based on combinati ons of different types of strategies (preventive, conditionbased maintenance (CBM) and corrective maintenance…) for different subsystems or components and st ructures of complex systems like an aircraft to achieve the most optimized solution in terms of availability, cost and safety / certification is a real challeng e. The maintenance strategy must satisfy the technicalrisk and cost feasibility of the maintenance program.
The scope of this paper is to provide an E2E perspective of health monitoring and management (HMM) and structural health mornitoring (SHM) as an integrated system element of a n integrated system health monitoring and management (ISHM) system. The paper will address two main topics: (1) The importance of a diagnostics and prognostic requirements specification to develop an innovative health monitoring and ma nagement system; (2) The certification of a health monitoring and management system aiming at a maintenance credit as an integral part of the maintenance strategies. The development of a maintenance program which is based on combinati ons of different types of strategies (preventive, conditionbased maintenance (CBM) and corrective maintenance…) for different subsystems or components and st ructures of complex systems like an aircraft to achieve the most optimized solution in terms of availability, cost and safety / certification is a real challeng e. The maintenance strategy must satisfy the technicalrisk and cost feasibility of the maintenance program.
2017, 34(3):247-254.
DOI: 10.16356/j.1005-1120.2017.03.247
Abstract:
A set of metallic specimens containing fatigue cracks with different sizes were tested using eddy current pulsed thermography (ECPT), therefore the relations between heating response of the crack area and the crack length was studied. The numerical and experimental results both showed that the increase of the crack length enhanced the crack heating response under specific test conditions. A particular form of calculated response signal, which is linearly related to the crack length, was introduced to provide a quantitative evaluation of crack length.
A set of metallic specimens containing fatigue cracks with different sizes were tested using eddy current pulsed thermography (ECPT), therefore the relations between heating response of the crack area and the crack length was studied. The numerical and experimental results both showed that the increase of the crack length enhanced the crack heating response under specific test conditions. A particular form of calculated response signal, which is linearly related to the crack length, was introduced to provide a quantitative evaluation of crack length.
2017, 34(3):255-264.
DOI: 10.16356/j.1005-1120.2017.03.255
Abstract:
The interfacial debonding in fiberreinforced plastic(FRP) strengthened repair material will affect the bonding strength and lead to failure of the repair without warning. Unfortunately the interfacial damage is normally invisible and often in the form of a patch rather than a throughwidth crack. Therefore, a debonding patch detection technique based on fiber optic interferometry is proposed. A quasiimpulse loading is applied with a rubberhead hammer and the total elongation of a surfacemounted optical fiber along the length of the repair material is measured as a function of load position. When a debonding patch is present, the induced sudden slope or sign change on the plot of fiber integral strain v.s. load position will reveal the extent and the location of the debonded area. The results of the study indicate that the proposed technique is applicable for debonding patch detection in repaired members under various support conditions.
The interfacial debonding in fiberreinforced plastic(FRP) strengthened repair material will affect the bonding strength and lead to failure of the repair without warning. Unfortunately the interfacial damage is normally invisible and often in the form of a patch rather than a throughwidth crack. Therefore, a debonding patch detection technique based on fiber optic interferometry is proposed. A quasiimpulse loading is applied with a rubberhead hammer and the total elongation of a surfacemounted optical fiber along the length of the repair material is measured as a function of load position. When a debonding patch is present, the induced sudden slope or sign change on the plot of fiber integral strain v.s. load position will reveal the extent and the location of the debonded area. The results of the study indicate that the proposed technique is applicable for debonding patch detection in repaired members under various support conditions.
2017, 34(3):265-271.
DOI: 10.16356/j.1005-1120.2017.03.265
Abstract:
The key to failure prevention for aeroengine lies in performance prediction and the exhaust gas temperature margin (EGTM) is used as the most important degradation parameter to obtain the operating performance of the aeroengine. Because of the complex environment interference, EGTM always has strong randomness, and the state space based degradation model can identify the noisy observation from the true degradation state, which is more close to the actual situations. Therefore, a state space model based on EGTM is established to describe the degradation path and predict the remaining useful life (RUL). As one of the most effective methods for both linear state estimation and parameter estimation, Kalman filter (KF) is applied. Firstly, with EGTM degradation data, state space model approach is used to set up a state space model for aeroengine. Secondly, RUL of aeroengine is analyzed, and expected RUL and distribution of RUL are determined. Finally, the sate space model and KF algorithm are applied to an example of CFM56 aeroengine. The expected RUL is predicted, and corresponding probability density distribution (PDF) and cumulative distribution function (CDF) are given. The result indicates that the accuracy of RUL prediction reaches 7.76% ahead 580 flight cycles (FC), which is more accurate than linear regression, and therefore shows the validity and rationality of the proposed method.
The key to failure prevention for aeroengine lies in performance prediction and the exhaust gas temperature margin (EGTM) is used as the most important degradation parameter to obtain the operating performance of the aeroengine. Because of the complex environment interference, EGTM always has strong randomness, and the state space based degradation model can identify the noisy observation from the true degradation state, which is more close to the actual situations. Therefore, a state space model based on EGTM is established to describe the degradation path and predict the remaining useful life (RUL). As one of the most effective methods for both linear state estimation and parameter estimation, Kalman filter (KF) is applied. Firstly, with EGTM degradation data, state space model approach is used to set up a state space model for aeroengine. Secondly, RUL of aeroengine is analyzed, and expected RUL and distribution of RUL are determined. Finally, the sate space model and KF algorithm are applied to an example of CFM56 aeroengine. The expected RUL is predicted, and corresponding probability density distribution (PDF) and cumulative distribution function (CDF) are given. The result indicates that the accuracy of RUL prediction reaches 7.76% ahead 580 flight cycles (FC), which is more accurate than linear regression, and therefore shows the validity and rationality of the proposed method.
5 Crack Propagation Path in TwoDirectionally Graded Composites Subjected to MixedMode I+II Loading
2017, 34(3):272-285.
DOI: 10.16356/j.1005-1120.2017.03.272
Abstract:
Crack propagation path in twodirectionally graded composites was investigated by the finite element method. A graded extended finite element method (XFEM) was employed to calculate displacement and stress fields in cracked graded structures. And a postprocessing subroutine of interaction energy integral was implemented to extract the mixedmode stress intensity factors (SIFs). The maximum hoop stress (MHS) criterion was adopted to predict crack growth direction based on the assumption of local homogenization of asymptotic cracktip fields in graded materials. Effects of material nonhomogeneous parameters on crack propagation paths were also discussed in detail. It is shown that the present method can provide relatively accurate predictions of crack paths in twodirectionally graded composites. Crack propagates in the decreasing direction of effective Young′s modulus. The shape and steepness of property gradient perpendicular to the crack surface have great influences on crack paths. Through redesigning material property reasonably, crack growth in graded material can be changed to improve mechanical behaviours of cracked structures.
Crack propagation path in twodirectionally graded composites was investigated by the finite element method. A graded extended finite element method (XFEM) was employed to calculate displacement and stress fields in cracked graded structures. And a postprocessing subroutine of interaction energy integral was implemented to extract the mixedmode stress intensity factors (SIFs). The maximum hoop stress (MHS) criterion was adopted to predict crack growth direction based on the assumption of local homogenization of asymptotic cracktip fields in graded materials. Effects of material nonhomogeneous parameters on crack propagation paths were also discussed in detail. It is shown that the present method can provide relatively accurate predictions of crack paths in twodirectionally graded composites. Crack propagates in the decreasing direction of effective Young′s modulus. The shape and steepness of property gradient perpendicular to the crack surface have great influences on crack paths. Through redesigning material property reasonably, crack growth in graded material can be changed to improve mechanical behaviours of cracked structures.
2017, 34(3):286-295.
DOI: 10.16356/j.1005-1120.2017.03.286
Abstract:
In order to achieve a better understanding of failure behavior of cruciform specimen under different biaxial loading conditions, a threedimensional finite element model is established with solid and interface elements. Maximum stress criterion, two Hashintype criteria and the new proposed criteria are used to predict the strength of plain woven textile composites when biaxial loading ratio equals 1. Compared with experimental data, only the new proposed criteria can reach reasonable results. The applicability of the new proposed criteria is also verified by predicting the tensile and compressive strength of cruciform specimen under different biaxial loading ratios. Moreover, the introduction of interface element makes it more intuitive to recognize delamination failure. The shape of the predicted delamination failure region in the interface layer is similar to that of the failure region in neighboring entity layers, but the area of delamination failure region is a little larger.
In order to achieve a better understanding of failure behavior of cruciform specimen under different biaxial loading conditions, a threedimensional finite element model is established with solid and interface elements. Maximum stress criterion, two Hashintype criteria and the new proposed criteria are used to predict the strength of plain woven textile composites when biaxial loading ratio equals 1. Compared with experimental data, only the new proposed criteria can reach reasonable results. The applicability of the new proposed criteria is also verified by predicting the tensile and compressive strength of cruciform specimen under different biaxial loading ratios. Moreover, the introduction of interface element makes it more intuitive to recognize delamination failure. The shape of the predicted delamination failure region in the interface layer is similar to that of the failure region in neighboring entity layers, but the area of delamination failure region is a little larger.
2017, 34(3):296-301.
DOI: 10.16356/j.1005-1120.2017.03.296
Abstract:
A wire rope defects detection method based on permanent magnet excitation is proposed. A detection system, mainly composed of permanent magnet excitation, distance detection, multisensor magnetic flux leakage signal acquisition and data analysis device, is set up. According to the different characteristics of the multisensor magnetic flux leakage signal, the localized fault (LF) and loss of metallic crosssectional area (LMA) signal is separated, and then the two defects can be detected. The experiments show that the method can effectively detect the two defects when they appear simultaneously on the wire rope.
A wire rope defects detection method based on permanent magnet excitation is proposed. A detection system, mainly composed of permanent magnet excitation, distance detection, multisensor magnetic flux leakage signal acquisition and data analysis device, is set up. According to the different characteristics of the multisensor magnetic flux leakage signal, the localized fault (LF) and loss of metallic crosssectional area (LMA) signal is separated, and then the two defects can be detected. The experiments show that the method can effectively detect the two defects when they appear simultaneously on the wire rope.
2017, 34(3):302-307.
DOI: 10.16356/j.1005-1120.2017.03.302
Abstract:
In order to monitor deformation of high temperature components for a long time, a sensing device integrating a bridgeshaped mechanical displacement amplifier has been designed. This sensing device has higher resolution and accuracy than conventional extensometers. However, the relation between the magnification ratio and the structure size of the displacement amplifier is a bottleneck of sensing device design. Addressing this, the magnification ratio of a mechanical displacement amplifier is analytically derived based on its geometry structure. Six prototypes of the displacement amplifier made in propathene are manufactured, and an experimental system is set up to validate the accuracy of the established magnification ratio equation. Theoretical magnification ratios and experimental magnification ratios are compared and agree well, which verifies that the proposed equation is reliable. This analytical equation provides an effective design method for bridgeshaped mechanical displacement amplifiers with an expected magnification ratio.
In order to monitor deformation of high temperature components for a long time, a sensing device integrating a bridgeshaped mechanical displacement amplifier has been designed. This sensing device has higher resolution and accuracy than conventional extensometers. However, the relation between the magnification ratio and the structure size of the displacement amplifier is a bottleneck of sensing device design. Addressing this, the magnification ratio of a mechanical displacement amplifier is analytically derived based on its geometry structure. Six prototypes of the displacement amplifier made in propathene are manufactured, and an experimental system is set up to validate the accuracy of the established magnification ratio equation. Theoretical magnification ratios and experimental magnification ratios are compared and agree well, which verifies that the proposed equation is reliable. This analytical equation provides an effective design method for bridgeshaped mechanical displacement amplifiers with an expected magnification ratio.
2017, 34(3):308-317.
DOI: 10.16356/j.1005-1120.2017.03.308
Abstract:
A model based damage identification was proposed by facilitating parameter sensitivity analysis and applied to a general overhead travelling crane. As updating reference data, experimental modal frequency was obtained by operational modal analysis (OMA) under ambient excitation. One dimensional damage function was defined to identify the damage by bending stiffness. The results showed that the model updating method could locate the damage and quantitatively describe the structure. The average error of eigenvalues between updated model analysis and the experimental results was less than 4% which proved the accuracy reliable. The comparison of finite element analysis and the test results of the deflection under the capacity load further verified the feasibility of this method.
A model based damage identification was proposed by facilitating parameter sensitivity analysis and applied to a general overhead travelling crane. As updating reference data, experimental modal frequency was obtained by operational modal analysis (OMA) under ambient excitation. One dimensional damage function was defined to identify the damage by bending stiffness. The results showed that the model updating method could locate the damage and quantitatively describe the structure. The average error of eigenvalues between updated model analysis and the experimental results was less than 4% which proved the accuracy reliable. The comparison of finite element analysis and the test results of the deflection under the capacity load further verified the feasibility of this method.
2017, 34(3):318-325.
DOI: 10.16356/j.1005-1120.2017.03.318
Abstract:
Pipeline plays an indispensable role in process industries, because the progressing cracklike defects of in it may result in serious accidents and significant economic losses. Therefore, it is essential to detect the cracks occurred in pipelines. The axial cracklike defects in elbows with different angle are inspected by using the T(0, 1) mode guided waves, in which different configurations including 45°, 90°, 135°and 180°(straight pipe) are considered respectively. Firstly, the detection sensitivity for different defect location is experimentally investigated. After that, finite element simulation is used to explore the propagation behaviors of T(0, 1) mode in different bend structures. Simulation and experiment results show that the crack in different areas of the elbow can affect the detection sensitivity. It can be found that the detection sensitivity of crack in the middle area of the elbow is higher compared to the extrados and intrados of the elbow. Finally, the mode conversion is also investigated when the T(0, 1) crosses the bend, and the results show that bend is a key factor to the mode conversion phenomenon which presents between the T(0, 1) mode and F(1, 2) mode.
Pipeline plays an indispensable role in process industries, because the progressing cracklike defects of in it may result in serious accidents and significant economic losses. Therefore, it is essential to detect the cracks occurred in pipelines. The axial cracklike defects in elbows with different angle are inspected by using the T(0, 1) mode guided waves, in which different configurations including 45°, 90°, 135°and 180°(straight pipe) are considered respectively. Firstly, the detection sensitivity for different defect location is experimentally investigated. After that, finite element simulation is used to explore the propagation behaviors of T(0, 1) mode in different bend structures. Simulation and experiment results show that the crack in different areas of the elbow can affect the detection sensitivity. It can be found that the detection sensitivity of crack in the middle area of the elbow is higher compared to the extrados and intrados of the elbow. Finally, the mode conversion is also investigated when the T(0, 1) crosses the bend, and the results show that bend is a key factor to the mode conversion phenomenon which presents between the T(0, 1) mode and F(1, 2) mode.
2017, 34(3):326-332.
DOI: 10.16356/j.1005-1120.2017.03.326
Abstract:
In order to achieve the modelbased fault monitoring and diagnosis, an accurate model for the rotor system is necessary to locate and quantify faults. Since the dynamic characteristics of a bladerotor system is influenced by foundation flexibility, the modeling and dynamic analyses on the foundation were sequentially investigated. Firstly, the effect of element size on the model convergence was investigated using the forward difference quotient as the slope of the frequency difference, which found that the model converged when the element size refined to 4 mm. Secondly, a modal analysis and a harmonic response analysis were performed to obtain the dynamic characteristics of the foundation structure. Finally, an optimization to the foundation utilizing an additional stiffener was conducted to reduce the foundation response and make the critical speed far away from the working frequency band of 20—50 Hz.
In order to achieve the modelbased fault monitoring and diagnosis, an accurate model for the rotor system is necessary to locate and quantify faults. Since the dynamic characteristics of a bladerotor system is influenced by foundation flexibility, the modeling and dynamic analyses on the foundation were sequentially investigated. Firstly, the effect of element size on the model convergence was investigated using the forward difference quotient as the slope of the frequency difference, which found that the model converged when the element size refined to 4 mm. Secondly, a modal analysis and a harmonic response analysis were performed to obtain the dynamic characteristics of the foundation structure. Finally, an optimization to the foundation utilizing an additional stiffener was conducted to reduce the foundation response and make the critical speed far away from the working frequency band of 20—50 Hz.
12 Warehouse Environment Parameter Monitoring System and Sensor Error Correction Model Based on PSO-BP
2017, 34(3):333-340.
DOI: 10.16356/j.1005-1120.2017.03.333
Abstract:
The warehouse environment parameter monitoring system is designed to avoid the networking and high cost of traditional monitoring system. A sensor error correction model which combines particle swarm optimization (PSO) with back propagation (BP) neural network algorithm is established to reduce nonlinear characteristics and improve test accuracy of the system. Simulation and experiments indicate that the PSOBP neural network algorithm has advantages of fast convergence rate and high diagnostic accuracy. The monitoring system can provide higher measurement precision, lower power consume, stable network data communication and fault diagnoses function. The system has been applied to monitoring environment parameter of warehouse, special vehicles and ships, etc.
The warehouse environment parameter monitoring system is designed to avoid the networking and high cost of traditional monitoring system. A sensor error correction model which combines particle swarm optimization (PSO) with back propagation (BP) neural network algorithm is established to reduce nonlinear characteristics and improve test accuracy of the system. Simulation and experiments indicate that the PSOBP neural network algorithm has advantages of fast convergence rate and high diagnostic accuracy. The monitoring system can provide higher measurement precision, lower power consume, stable network data communication and fault diagnoses function. The system has been applied to monitoring environment parameter of warehouse, special vehicles and ships, etc.
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