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RSS2018 Vol. 37, No. 1
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2018, 37(1): 1-7.
doi: 10.13433/j.cnki.1003-8728.2018.0101
PDF 780KB
Abstract:
Noise source identification and character analysis of a small diesel engine generator set is carried out by experimental ways. Based on the results, the structural optimization measures of sound insulation hood are put forward. For low frequency range, structure mass of noise insulation plate is confirmed to be the key influencing factor of transmission loss, and topological optimization is carried out. Transmission loss below 1 000 Hz is 13.16 dB(A). For middle-high frequency range spread through air vent of the enclosure, considering high-order sound wave propagated in air duct, baffle position and window width are the key factors influencing transmission loss, and optimized by genetic algorithm to suppress high-order sound wave. Transmission loss of air duct silencer is 30.3 dB(A). This method is verified by a test and sound pressure level of the generator set at a distance of 7 m is reduced to 60.7 dB(A).
Noise source identification and character analysis of a small diesel engine generator set is carried out by experimental ways. Based on the results, the structural optimization measures of sound insulation hood are put forward. For low frequency range, structure mass of noise insulation plate is confirmed to be the key influencing factor of transmission loss, and topological optimization is carried out. Transmission loss below 1 000 Hz is 13.16 dB(A). For middle-high frequency range spread through air vent of the enclosure, considering high-order sound wave propagated in air duct, baffle position and window width are the key factors influencing transmission loss, and optimized by genetic algorithm to suppress high-order sound wave. Transmission loss of air duct silencer is 30.3 dB(A). This method is verified by a test and sound pressure level of the generator set at a distance of 7 m is reduced to 60.7 dB(A).
2018, 37(1): 8-12.
doi: 10.13433/j.cnki.1003-8728.2018.0102
Abstract:
On the problem of nonlinear damage identification of frame structures, a damage identification method based on the principal component analysis is put forward. The data compression and feature extraction characteristics in the principal component analysis is used to identify the nonlinear damage. Firstly, the data of health state of the structure is processed to extract the characteristic components, secondly the principal component model is established and the unknown states' experimental data is projected upon principal component model, finally the nonlinear damage is identified by constructing several damage indexes. In this paper, a four-storey frame collision model is used as the experimental subject and the nonlinear damage source is constructed by a bolt and steel column, at last the experimental result shows that the structural damage can be effectively identified.
On the problem of nonlinear damage identification of frame structures, a damage identification method based on the principal component analysis is put forward. The data compression and feature extraction characteristics in the principal component analysis is used to identify the nonlinear damage. Firstly, the data of health state of the structure is processed to extract the characteristic components, secondly the principal component model is established and the unknown states' experimental data is projected upon principal component model, finally the nonlinear damage is identified by constructing several damage indexes. In this paper, a four-storey frame collision model is used as the experimental subject and the nonlinear damage source is constructed by a bolt and steel column, at last the experimental result shows that the structural damage can be effectively identified.
2018, 37(1): 13-18.
doi: 10.13433/j.cnki.1003-8728.2018.0103
Abstract:
To avoid the return tube failure caused by collision and friction between recirculation ball and return tube in the internal recirculation ball screw, we optimized the existing ball-return curve of the return tube, aiming to reduce the collision force and friction torque between recirculation ball and return tube; we also optimized the ratio coefficient of the sine ball-return curve and the five parabolic ball-return curve. After obtaining the optimal ball-return curve, a 3D model was built and the simulation analysis based on the multi-body dynamics was further carried out. The analysis results show that the optimized ball-return curve of the return tube can effectively reduce the collision force and friction torque between recirculation ball and return tube, and that the ball-return smoothness and dynamic behavior of the recirculation ball screw were obviously improved.
To avoid the return tube failure caused by collision and friction between recirculation ball and return tube in the internal recirculation ball screw, we optimized the existing ball-return curve of the return tube, aiming to reduce the collision force and friction torque between recirculation ball and return tube; we also optimized the ratio coefficient of the sine ball-return curve and the five parabolic ball-return curve. After obtaining the optimal ball-return curve, a 3D model was built and the simulation analysis based on the multi-body dynamics was further carried out. The analysis results show that the optimized ball-return curve of the return tube can effectively reduce the collision force and friction torque between recirculation ball and return tube, and that the ball-return smoothness and dynamic behavior of the recirculation ball screw were obviously improved.
2018, 37(1): 19-23.
doi: 10.13433/j.cnki.1003-8728.2018.0104
Abstract:
This paper deduced the coupling equations of biological heart valve and blood with the Arbitrary Lagrange-Euler(ALE) method, and discretized the momentum equation of blood with the pressure-implicit splitting of operators(PISO) algorithm. The velocity iteration equation of the coupling process is obtained. Then, the PISO was carried out with the Fluent software, and the mathematical model of the valve deformation was obtained. The computer simulation results show that the valve deformation mainly occurs on the free edge of each leaflet and that the abdomen deformation is small and that the free edge curls during the valve opening. The experiments on the pulsatile flow of the valve were also performed, and the experimental results agree with the simulation results. The simulation and experimental results show that this method can be used to analyze the fluid-solid coupling of the bioprosthetic heart valve, providing some reference for its further optimization.
This paper deduced the coupling equations of biological heart valve and blood with the Arbitrary Lagrange-Euler(ALE) method, and discretized the momentum equation of blood with the pressure-implicit splitting of operators(PISO) algorithm. The velocity iteration equation of the coupling process is obtained. Then, the PISO was carried out with the Fluent software, and the mathematical model of the valve deformation was obtained. The computer simulation results show that the valve deformation mainly occurs on the free edge of each leaflet and that the abdomen deformation is small and that the free edge curls during the valve opening. The experiments on the pulsatile flow of the valve were also performed, and the experimental results agree with the simulation results. The simulation and experimental results show that this method can be used to analyze the fluid-solid coupling of the bioprosthetic heart valve, providing some reference for its further optimization.
2018, 37(1): 24-29.
doi: 10.13433/j.cnki.1003-8728.2018.0105
Abstract:
When the arm end of the manipulator moves along the desired trajectory, if some obstacles affect movement of the end, it makes arm deviating from the expected trajectory, even the end maybe be clashed with obstacles. Aiming at this problem, a new method of trajectory planning task priority is put forward in this paper, in which the end of the manipulator can avoid the obstacle and continue to track the desired trajectory. So as to realize the priority transformation between the obstacle avoidance motion and trajectory tracking, when the end of the manipulator trajectory appears obstacles, give priority control to obstacle avoidance movement. Through calculating the terminal position increment makes the arm end effecter produces escape velocity, thus avoiding obstacles; Conversely, giving trajectory tracking as priority control. Based on the desired trajectory and the actual manipulator position error control, which achieve the goal of improving the terminal trajectory tracking precision. Finally, simulation and test verification have been done for the redundant robots. Results show that when the barrier and mechanical arm terminal trajectory are conflict, the trajectory planning method based on task priority can make the end of manipulator effectively avoiding obstacles. At the same time, the arm can still track the desired trajectory after obstacle avoidance.
When the arm end of the manipulator moves along the desired trajectory, if some obstacles affect movement of the end, it makes arm deviating from the expected trajectory, even the end maybe be clashed with obstacles. Aiming at this problem, a new method of trajectory planning task priority is put forward in this paper, in which the end of the manipulator can avoid the obstacle and continue to track the desired trajectory. So as to realize the priority transformation between the obstacle avoidance motion and trajectory tracking, when the end of the manipulator trajectory appears obstacles, give priority control to obstacle avoidance movement. Through calculating the terminal position increment makes the arm end effecter produces escape velocity, thus avoiding obstacles; Conversely, giving trajectory tracking as priority control. Based on the desired trajectory and the actual manipulator position error control, which achieve the goal of improving the terminal trajectory tracking precision. Finally, simulation and test verification have been done for the redundant robots. Results show that when the barrier and mechanical arm terminal trajectory are conflict, the trajectory planning method based on task priority can make the end of manipulator effectively avoiding obstacles. At the same time, the arm can still track the desired trajectory after obstacle avoidance.
State Research and Application of Multiple-pulse Excitation Method in Diagnosis of Bearing Ball Wear
2018, 37(1): 30-35.
doi: 10.13433/j.cnki.1003-8728.2018.0106
Abstract:
The bearing failure in mechanical system has strong non-linear characteristic, and its fault feature extraction is very difficult. In order to solve this problem, a new fault feature extraction method based on the Volterra series kernel under multi-pulse excitation is proposed. The nonlinear system Volterra series model is established through input and output signals of the system. Using low-order nuclear, and the time domain and frequency domain, the status of the bearing is determined and then analyzed whether the bearing in the fault states. The method is validated by taking the fault of rolling bearing in the University of Western Reserve as an example, the wavelet algorithm and multiple pulse excitation method were compared. It is concluded that the multi-pulse excitation method can extract the bearing fault features conveniently and accurately.
The bearing failure in mechanical system has strong non-linear characteristic, and its fault feature extraction is very difficult. In order to solve this problem, a new fault feature extraction method based on the Volterra series kernel under multi-pulse excitation is proposed. The nonlinear system Volterra series model is established through input and output signals of the system. Using low-order nuclear, and the time domain and frequency domain, the status of the bearing is determined and then analyzed whether the bearing in the fault states. The method is validated by taking the fault of rolling bearing in the University of Western Reserve as an example, the wavelet algorithm and multiple pulse excitation method were compared. It is concluded that the multi-pulse excitation method can extract the bearing fault features conveniently and accurately.
2018, 37(1): 36-42.
doi: 10.13433/j.cnki.1003-8728.2018.0107
Abstract:
Considering this problem that minimum entropy deconvolution (MED) algorithm is unsuitable for strong noise and outliers, a new method of fault feature extraction from gearbox based on maximum correlated kurtosis deconvolution (MCKD) is introduced, which can overcome the shortcoming of MED algorithm. However, the effect of MCKD algorithm is probably poor according to priori information to select fault period. Therefore, an idea of fault period searching is discussed, the fault period can be limited to a certain range of computation period, and the maximum correlated kurtosis(KC) converges to the global maximum about the optimum fault period with large M and suitable L, and ensures the effective results for MCKD algorithm with different M values. The experimental results of gearbox fault feature extraction with a missing tooth and a chipped tooth indicate that the feasibility and effectiveness of optimum fault period searching of MCKD method are testified.
Considering this problem that minimum entropy deconvolution (MED) algorithm is unsuitable for strong noise and outliers, a new method of fault feature extraction from gearbox based on maximum correlated kurtosis deconvolution (MCKD) is introduced, which can overcome the shortcoming of MED algorithm. However, the effect of MCKD algorithm is probably poor according to priori information to select fault period. Therefore, an idea of fault period searching is discussed, the fault period can be limited to a certain range of computation period, and the maximum correlated kurtosis(KC) converges to the global maximum about the optimum fault period with large M and suitable L, and ensures the effective results for MCKD algorithm with different M values. The experimental results of gearbox fault feature extraction with a missing tooth and a chipped tooth indicate that the feasibility and effectiveness of optimum fault period searching of MCKD method are testified.
2018, 37(1): 43-54.
doi: 10.13433/j.cnki.1003-8728.2018.0108
Abstract:
In view of the one-to-one correspondence between the meshing line and the rotor profile,which can reflect some important performance parameters of the rotor profile, and considering that the disadvantage of "rotor method" and "rack method", a new method of profile design are derived based on meshing line for the twin screw compressor, in which B-spline curve is used as part of meshing line in order to modify the rotor profiles and control the shape of the meshing line more conveniently. On the basis of the existing rotor profile, a meshing line is designed based on the B-spline, and the reverse design method is applied to design a pair of male and female rotor profiles. The CFD simulation of the final rotor profile is carried out under different working conditions and compared with the traditional design results, and then the characteristics of its internal flow field are analyzed. Finally, the reliability of the simulation results is verified by experiment, and the results show that the new design method is feasible and reliable for the twin screw compressor.
In view of the one-to-one correspondence between the meshing line and the rotor profile,which can reflect some important performance parameters of the rotor profile, and considering that the disadvantage of "rotor method" and "rack method", a new method of profile design are derived based on meshing line for the twin screw compressor, in which B-spline curve is used as part of meshing line in order to modify the rotor profiles and control the shape of the meshing line more conveniently. On the basis of the existing rotor profile, a meshing line is designed based on the B-spline, and the reverse design method is applied to design a pair of male and female rotor profiles. The CFD simulation of the final rotor profile is carried out under different working conditions and compared with the traditional design results, and then the characteristics of its internal flow field are analyzed. Finally, the reliability of the simulation results is verified by experiment, and the results show that the new design method is feasible and reliable for the twin screw compressor.
2018, 37(1): 55-62.
doi: 10.13433/j.cnki.1003-8728.2018.0109
Abstract:
In order to improve the performance of a loader and reduce its fuel consumption, the power matching and speed sensing control between the hydraulic torque converter and the engine was researched. Based on the loader's operating mode, the best working curve of 154 kW engine and the main operating point of 340 mm hydraulic torque converter were selected for power matching. According to the operating condition identification and the control principle of the loader, the speed sensing control of the engine was carried out. Taking the 5-ton loader as an example, the model of the speed sensing control system based on condition identification was established and the calculation results were compared with the traditional method. The results show that:in the excavation condition, the output torque of the loader increases by 25.6% and the fuel consumption reduces by 21.6%. In the unloading condition, the fuel consumption decreases from 32 g/h to 8.5 g/h. In the driving condition, the efficient economic mode limites the output power by 4%, reduces fuel consumption by 7.5%. In the most economical mode, the power of engine limites by 30%, and the fuel consumption reduced by 36.8%.
In order to improve the performance of a loader and reduce its fuel consumption, the power matching and speed sensing control between the hydraulic torque converter and the engine was researched. Based on the loader's operating mode, the best working curve of 154 kW engine and the main operating point of 340 mm hydraulic torque converter were selected for power matching. According to the operating condition identification and the control principle of the loader, the speed sensing control of the engine was carried out. Taking the 5-ton loader as an example, the model of the speed sensing control system based on condition identification was established and the calculation results were compared with the traditional method. The results show that:in the excavation condition, the output torque of the loader increases by 25.6% and the fuel consumption reduces by 21.6%. In the unloading condition, the fuel consumption decreases from 32 g/h to 8.5 g/h. In the driving condition, the efficient economic mode limites the output power by 4%, reduces fuel consumption by 7.5%. In the most economical mode, the power of engine limites by 30%, and the fuel consumption reduced by 36.8%.
2018, 37(1): 63-69.
doi: 10.13433/j.cnki.1003-8728.2018.0110
Abstract:
In order to improve the cutting performance of shearer drum, the similarity criterion equation of drum cutting system and the similar ratio of parameters were obtained based on dimensional analysis; Aimed at the prototype of the spiral drum of a shearer, a new type of large mining high shearer drum was designed based on similarity theory. The similarity was validated by the shearer drum aided design software, and the comparative analysis was performed with a scaled model. The results show that the similarity model and the prototype maintain a good similarity in cutting performance, the cutting area is increased by 17% compared to the prototype, and the design method based on similarity theory is better than conversion method based on scale theory, which providing a new approach for the rapid design of the spiral drum of shearer.
In order to improve the cutting performance of shearer drum, the similarity criterion equation of drum cutting system and the similar ratio of parameters were obtained based on dimensional analysis; Aimed at the prototype of the spiral drum of a shearer, a new type of large mining high shearer drum was designed based on similarity theory. The similarity was validated by the shearer drum aided design software, and the comparative analysis was performed with a scaled model. The results show that the similarity model and the prototype maintain a good similarity in cutting performance, the cutting area is increased by 17% compared to the prototype, and the design method based on similarity theory is better than conversion method based on scale theory, which providing a new approach for the rapid design of the spiral drum of shearer.
2018, 37(1): 70-75.
doi: 10.13433/j.cnki.1003-8728.2018.0111
Abstract:
Aiming at the geometric error induced by guide surface deformation in precision machine tools assembly process, an idea of deformation pre-elimination is proposed. The final guide surface deformation after assembly can be obtained by the static analysis of the machine tools. Through the reproduction of the deformation in support state, it can be eliminated in advance. A precision horizontal machine center was taken as an example to elaborate this method, the key point of this method is to obtain the final deformation of guide surface in support state. Taking the position dimensions as the variables, a neural network was constructed with the samples which were chosen by the orthogonal experiment, and genetic algorithm was used to get the best locations of the supports, so the surfaces of guides can present the target deformation. The results show that using the optimized support, the static deformation of the guide surface and the target deformation present the same shape and the maximum deformation, which are 7.982 8 μm and 8.2 μm, respectively. The error between them is only 0.21 μm, which denotes that the optimization has good effect.
Aiming at the geometric error induced by guide surface deformation in precision machine tools assembly process, an idea of deformation pre-elimination is proposed. The final guide surface deformation after assembly can be obtained by the static analysis of the machine tools. Through the reproduction of the deformation in support state, it can be eliminated in advance. A precision horizontal machine center was taken as an example to elaborate this method, the key point of this method is to obtain the final deformation of guide surface in support state. Taking the position dimensions as the variables, a neural network was constructed with the samples which were chosen by the orthogonal experiment, and genetic algorithm was used to get the best locations of the supports, so the surfaces of guides can present the target deformation. The results show that using the optimized support, the static deformation of the guide surface and the target deformation present the same shape and the maximum deformation, which are 7.982 8 μm and 8.2 μm, respectively. The error between them is only 0.21 μm, which denotes that the optimization has good effect.
2018, 37(1): 76-80.
doi: 10.13433/j.cnki.1003-8728.2018.0112
Abstract:
This study presents the influence of the electrode materials, electrical discharge parameters including discharge peak current and pulse time on the surface integrity of 8418 steel in EDM process. The surface roughness (Ra), average white layer thickness (WT) and surface micro cracks of workpiece have been measured after EDM. The experimental results reveal that Ra and WT obtained with copper electrode is bigger than that with CuW70 electrode, but there is slight difference in Ra and WT in the finish process of EDM. The value of Ra and WT increase with the increasing of discharge current and pulse duration, the pulse current plays a major role on WT. There is no micro cracks on the workpiece surface under lower discharge energy and the better surface integrity is obtained. The number of micro cracks with copper electrode is more than that with CuW70 electrode under high discharge energy, the width of micro cracks are almost the same.
This study presents the influence of the electrode materials, electrical discharge parameters including discharge peak current and pulse time on the surface integrity of 8418 steel in EDM process. The surface roughness (Ra), average white layer thickness (WT) and surface micro cracks of workpiece have been measured after EDM. The experimental results reveal that Ra and WT obtained with copper electrode is bigger than that with CuW70 electrode, but there is slight difference in Ra and WT in the finish process of EDM. The value of Ra and WT increase with the increasing of discharge current and pulse duration, the pulse current plays a major role on WT. There is no micro cracks on the workpiece surface under lower discharge energy and the better surface integrity is obtained. The number of micro cracks with copper electrode is more than that with CuW70 electrode under high discharge energy, the width of micro cracks are almost the same.
2018, 37(1): 81-88.
doi: 10.13433/j.cnki.1003-8728.2018.0113
Abstract:
In this paper, the error components and the causes of the trigger probe measurement results in the on-line measurement system is analyzed, and the mathematical models for the probe calibration which is calculated by the least square method is established. To reduce the measurement error by the probe is put forward, which has considered the pre travel error, the anisotropy of the probe, probe eccentric error and other influence factors, and using bilinear interpolation method to establish the mapping relationship between the compensation value of the radius of the probe and the normal direction of the measuring point, to calculate the radius compensation value of the fitting of any normal vector direction. Finally, the measurement results show that the measurement precision of the compensation measurement system is greatly improved after the experiment.
In this paper, the error components and the causes of the trigger probe measurement results in the on-line measurement system is analyzed, and the mathematical models for the probe calibration which is calculated by the least square method is established. To reduce the measurement error by the probe is put forward, which has considered the pre travel error, the anisotropy of the probe, probe eccentric error and other influence factors, and using bilinear interpolation method to establish the mapping relationship between the compensation value of the radius of the probe and the normal direction of the measuring point, to calculate the radius compensation value of the fitting of any normal vector direction. Finally, the measurement results show that the measurement precision of the compensation measurement system is greatly improved after the experiment.
2018, 37(1): 89-99.
doi: 10.13433/j.cnki.1003-8728.2018.0114
Abstract:
In order to improve the surface quality of high-speed cold rolling lines technology, the cause of residual height of tooth profile of the theoretical analysis and analytic calculation and geometric simulation are studied. The basic principle of high-speed cold rolling technology are briefly discussed, the factors that influence the residual height of the block side teeth are analyzed. The model for residual height is established by calculating the residual height of flank. With MATLAB, the effects of various factors on the residual height geometry are studied. On the self-developed equipment for cold rolling tooth block cold test, the flank residual height were measured so as to verify the correctness of analytic geometry and accuracy reliability.
In order to improve the surface quality of high-speed cold rolling lines technology, the cause of residual height of tooth profile of the theoretical analysis and analytic calculation and geometric simulation are studied. The basic principle of high-speed cold rolling technology are briefly discussed, the factors that influence the residual height of the block side teeth are analyzed. The model for residual height is established by calculating the residual height of flank. With MATLAB, the effects of various factors on the residual height geometry are studied. On the self-developed equipment for cold rolling tooth block cold test, the flank residual height were measured so as to verify the correctness of analytic geometry and accuracy reliability.
2018, 37(1): 100-107.
doi: 10.13433/j.cnki.1003-8728.2018.0115
Abstract:
The synchronous data capturing of stress and strain, and the fast accurate acquision of strain are the key steps for measuring stress-strain curve. Firstly, a hardware circuit is designed for the synchronous acquisition of loading force and images, which can guarantee the accurate synchronization of the stress and strain in timing sequence. Subsequently, a grid-propagting method to realize topology build-up and precise coordinate extraction of grid nodes is proposed. After that, a binocular stereo vision technology is thus leveraged to track 3D deformation of the grids and to measure strain combining with the finite strain theory. The experimental results demonstrate the present method has the integrated advantage on the accuracy and efficiency comparing with the traditional method.
The synchronous data capturing of stress and strain, and the fast accurate acquision of strain are the key steps for measuring stress-strain curve. Firstly, a hardware circuit is designed for the synchronous acquisition of loading force and images, which can guarantee the accurate synchronization of the stress and strain in timing sequence. Subsequently, a grid-propagting method to realize topology build-up and precise coordinate extraction of grid nodes is proposed. After that, a binocular stereo vision technology is thus leveraged to track 3D deformation of the grids and to measure strain combining with the finite strain theory. The experimental results demonstrate the present method has the integrated advantage on the accuracy and efficiency comparing with the traditional method.
2018, 37(1): 108-114.
doi: 10.13433/j.cnki.1003-8728.2018.0116
Abstract:
A novel differential steering system with in-wheel motor was proposed, by which active steering (AFS) function and direct yaw-moment control (DYC) function can be realized. System structure and basic operation principle of the novel differential steering system with in-wheel motor were described in detail, as well as dynamic models of electro-mechanical coupling for the novel steering system and vehicle were built. Then, combination control strategy of active steering and direct yaw-moment control was proposed, as well as controller was designed based on linear quadratic regulator (LQR) control theory. To verify the effectiveness of the combination control strategy of AFS and DYC, simulation test in limiting condition with the intervention of lateral wind force was conducted. Simulation results indicate that the combination control strategy of AFS and DYC proposed in this paper is effective, which can further improve the lateral stability of the vehicle that driving at the limiting condition.
A novel differential steering system with in-wheel motor was proposed, by which active steering (AFS) function and direct yaw-moment control (DYC) function can be realized. System structure and basic operation principle of the novel differential steering system with in-wheel motor were described in detail, as well as dynamic models of electro-mechanical coupling for the novel steering system and vehicle were built. Then, combination control strategy of active steering and direct yaw-moment control was proposed, as well as controller was designed based on linear quadratic regulator (LQR) control theory. To verify the effectiveness of the combination control strategy of AFS and DYC, simulation test in limiting condition with the intervention of lateral wind force was conducted. Simulation results indicate that the combination control strategy of AFS and DYC proposed in this paper is effective, which can further improve the lateral stability of the vehicle that driving at the limiting condition.
2018, 37(1): 115-119.
doi: 10.13433/j.cnki.1003-8728.2018.0117
Abstract:
Based on the advanced characters of ensemble empirical mode decomposition (EEMD) and Hilbert transform (HT) method, it is applied to the fault diagnosis of high speed train gear box. The vibration characteristics of the gear box are analyzed with EEMD and HT methods, including the characteristics of time domain and frequency domain. The application and performance of EEMD and HT methods in identifying and diagnosing the defect of high-speed EMU gearbox is explored by compared with that of the continuous wavelet method. There are two conclusions coming from the research work:1) The EEMD and HT method can better identify the fault feature of the High-speed EMU gear than the often used continuous wavelet transform, and it has a nice application and performance in dealing with practical problems. 2) The vibration amplitude of the defective gearbox is significantly much larger than the normal gearbox, and the vibration character has changed dramatically.
Based on the advanced characters of ensemble empirical mode decomposition (EEMD) and Hilbert transform (HT) method, it is applied to the fault diagnosis of high speed train gear box. The vibration characteristics of the gear box are analyzed with EEMD and HT methods, including the characteristics of time domain and frequency domain. The application and performance of EEMD and HT methods in identifying and diagnosing the defect of high-speed EMU gearbox is explored by compared with that of the continuous wavelet method. There are two conclusions coming from the research work:1) The EEMD and HT method can better identify the fault feature of the High-speed EMU gear than the often used continuous wavelet transform, and it has a nice application and performance in dealing with practical problems. 2) The vibration amplitude of the defective gearbox is significantly much larger than the normal gearbox, and the vibration character has changed dramatically.
2018, 37(1): 120-124.
doi: 10.13433/j.cnki.1003-8728.2018.0118
Abstract:
A method for increasing the micro extrusion mold heating cooling rate and shortening the hot pressing molding cycle was put forward. By coating graphene layers on the silicon wafer surface by CVD(Chemical vapor deposition), according to the properties of graphene with high electrical conductivity and thermal conductivity and so on, the influence of the graphene layer electric coupling on the mold's temperature was studied. The simulation results indicated that the higher voltage and thicker graphene layer would cause a relatively higher temperature rising rate. When the graphene layer has a thickness of 40 nm and the applied voltage is 150 V, the temperature of silicon wafer surface increases quickly to a heating rate of 9.87 K/s from room temperature. When the temperature of the silicon mold temperature is stable, the temperature of the microstructure is higher than the bulk silicon wafer surface.
A method for increasing the micro extrusion mold heating cooling rate and shortening the hot pressing molding cycle was put forward. By coating graphene layers on the silicon wafer surface by CVD(Chemical vapor deposition), according to the properties of graphene with high electrical conductivity and thermal conductivity and so on, the influence of the graphene layer electric coupling on the mold's temperature was studied. The simulation results indicated that the higher voltage and thicker graphene layer would cause a relatively higher temperature rising rate. When the graphene layer has a thickness of 40 nm and the applied voltage is 150 V, the temperature of silicon wafer surface increases quickly to a heating rate of 9.87 K/s from room temperature. When the temperature of the silicon mold temperature is stable, the temperature of the microstructure is higher than the bulk silicon wafer surface.
2018, 37(1): 125-131.
doi: 10.13433/j.cnki.1003-8728.2018.0119
Abstract:
The dynamic tensile experiments of S580B at intermediate and low strain rates were developed with the high velocity hydraulic servo-testing machine. An indirect method of measuring dynamic load by aid of static calibration experiment was proposed, and the strain field was calculated with digital speckle correlation method. Therefore, the true stress-strain curves at different strain rates were obtained, and the results showed the material behaved apparent strain-hardening effect and strain rate sensitivity. The dynamic constitutive equation of S580B was fitted with Johnson-Cook model and the corresponding material parameters were applied to the finite element simulation of the test specimen, and the simulation result demonstrated the constitutive equation could exactly illustrate dynamic mechanical property of the material.
The dynamic tensile experiments of S580B at intermediate and low strain rates were developed with the high velocity hydraulic servo-testing machine. An indirect method of measuring dynamic load by aid of static calibration experiment was proposed, and the strain field was calculated with digital speckle correlation method. Therefore, the true stress-strain curves at different strain rates were obtained, and the results showed the material behaved apparent strain-hardening effect and strain rate sensitivity. The dynamic constitutive equation of S580B was fitted with Johnson-Cook model and the corresponding material parameters were applied to the finite element simulation of the test specimen, and the simulation result demonstrated the constitutive equation could exactly illustrate dynamic mechanical property of the material.
2018, 37(1): 132-137.
doi: 10.13433/j.cnki.1003-8728.2018.0120
Abstract:
A "spring-mass" model is established for the tethered satellite system, and the dynamic equations of the system are derived in the Hamiltonian system with the introduction of generalized coordinates and generalized momenta. The classic Runge-Kutta method and symplectic Runge-Kutta method are applied to discretize the dynamic equations. The advantages of symplectic Runge-Kutta method are examined through long-time numerical simulations. Finally, the impact of J2 perturbation and solar radiation pressure on the orbital radius, true anamaly, attitude angle and elastic deformation of the tether are discussed. The results show that there exist obvious effects of J2 perturbation and solar radiation pressure on the tethered satellite system.
A "spring-mass" model is established for the tethered satellite system, and the dynamic equations of the system are derived in the Hamiltonian system with the introduction of generalized coordinates and generalized momenta. The classic Runge-Kutta method and symplectic Runge-Kutta method are applied to discretize the dynamic equations. The advantages of symplectic Runge-Kutta method are examined through long-time numerical simulations. Finally, the impact of J2 perturbation and solar radiation pressure on the orbital radius, true anamaly, attitude angle and elastic deformation of the tether are discussed. The results show that there exist obvious effects of J2 perturbation and solar radiation pressure on the tethered satellite system.
2018, 37(1): 138-147.
doi: 10.13433/j.cnki.1003-8728.2018.0121
Abstract:
The effects of the hole-perpendicularity error on the inter-laminar stress and the mechanical performance of the joint are investigated. It is found that the stress distribution around the hole is heavily affected by the mentioned error. The bolt's posture may adjust when it is fastened in a bolt hole with perpendicularity error, during which the bolt shank bearing the hole wall plays an important role. Moreover, the inter-laminar shear stress increases with the increasing of hole perpendicularity error, which is the main reason for inducing delamination failure. Finally, to increase the fastening torque can help to reduce the negative effects caused by hole perpendicularity error, which was proved by the experimental results.
The effects of the hole-perpendicularity error on the inter-laminar stress and the mechanical performance of the joint are investigated. It is found that the stress distribution around the hole is heavily affected by the mentioned error. The bolt's posture may adjust when it is fastened in a bolt hole with perpendicularity error, during which the bolt shank bearing the hole wall plays an important role. Moreover, the inter-laminar shear stress increases with the increasing of hole perpendicularity error, which is the main reason for inducing delamination failure. Finally, to increase the fastening torque can help to reduce the negative effects caused by hole perpendicularity error, which was proved by the experimental results.
2018, 37(1): 148-151.
doi: 10.13433/j.cnki.1003-8728.2018.0122
Abstract:
Rigid body dynamics model of landing gear shimmy is first built in LMS Virtual. Lab Motion platform, and this model is preliminary checked through the drop test. Secondly, key parts of landing gear are processed again into flexible parts in finite element software PATRAN, so the multi-body dynamics model of landing gear shimmy is built. Then shimmy work condition simulation is conducted, the working modal is identified, and modal result is repeatedly compared with flight test result in time-frequency domain, the model is modified and updated continually, finally the model correlation work is finished. At last, test envelope is expanded by initial model, the stability of landing gears in the whole envelope is validated, and shimmy flight test state points are optimized.
Rigid body dynamics model of landing gear shimmy is first built in LMS Virtual. Lab Motion platform, and this model is preliminary checked through the drop test. Secondly, key parts of landing gear are processed again into flexible parts in finite element software PATRAN, so the multi-body dynamics model of landing gear shimmy is built. Then shimmy work condition simulation is conducted, the working modal is identified, and modal result is repeatedly compared with flight test result in time-frequency domain, the model is modified and updated continually, finally the model correlation work is finished. At last, test envelope is expanded by initial model, the stability of landing gears in the whole envelope is validated, and shimmy flight test state points are optimized.
2018, 37(1): 152-157.
doi: 10.13433/j.cnki.1003-8728.2018.0123
Abstract:
Aircraft structural test is affected greatly by the environmental conditions, so that testing control error may be changed largly. The traditional PID controller cannot control testing error effectively. To solve the problem, a closed-loop compensation control technique is developed. Based on the control parameter optimization technique, PID self-adaptive technique and open-loop compensation control scheme, the effect mechanism of environmental conditions was analyzed. A closed-loop compensation control algorithm was designed. Using this control algorithm, the output signal of controller can be compensated in real time to decrease the environmental effect, and the loading system can be controlled precisely. On the other side, the closed-loop compensation control technique may result in system instability, so Hurwitz stability criterion was used to verify the stability of this method. In order to validate the method, two test setups were designed and the verification experiments were perofrmed. The results showed that the present method was effective and reasonable to improve the testing control accuracy, and could be widely used in relevant tests in the future.
Aircraft structural test is affected greatly by the environmental conditions, so that testing control error may be changed largly. The traditional PID controller cannot control testing error effectively. To solve the problem, a closed-loop compensation control technique is developed. Based on the control parameter optimization technique, PID self-adaptive technique and open-loop compensation control scheme, the effect mechanism of environmental conditions was analyzed. A closed-loop compensation control algorithm was designed. Using this control algorithm, the output signal of controller can be compensated in real time to decrease the environmental effect, and the loading system can be controlled precisely. On the other side, the closed-loop compensation control technique may result in system instability, so Hurwitz stability criterion was used to verify the stability of this method. In order to validate the method, two test setups were designed and the verification experiments were perofrmed. The results showed that the present method was effective and reasonable to improve the testing control accuracy, and could be widely used in relevant tests in the future.
2018, 37(1): 158-164.
doi: 10.13433/j.cnki.1003-8728.2018.0124
Abstract:
Based on statistical energy analysis (SEA) and VA-One software platform, the sound pressure level of domestic turboprop aircraft was obtained. By comparing the sound pressure level in the condition of unilateral acoustic load for the turboprop aircraft, the performance of sound insulation for the wall panels of turboprop aircraft was investigated at different acoustic processing conditions. The results show that the pressure level of cabin can decrease by 27 dB(A) by wall panel acoustic treatment; By comparing the sound pressure level in the cabin at four kinds of acoustic processing, the results show that the differences between process 1, process 2 and process 3 are very small; The pressure level of cabin can reduce about 0.4~0.5 dB(A) with the damping material C3202-25(process 4). Therefore, it is an effective way of acoustic processing to use the damping material on the wall panels.
Based on statistical energy analysis (SEA) and VA-One software platform, the sound pressure level of domestic turboprop aircraft was obtained. By comparing the sound pressure level in the condition of unilateral acoustic load for the turboprop aircraft, the performance of sound insulation for the wall panels of turboprop aircraft was investigated at different acoustic processing conditions. The results show that the pressure level of cabin can decrease by 27 dB(A) by wall panel acoustic treatment; By comparing the sound pressure level in the cabin at four kinds of acoustic processing, the results show that the differences between process 1, process 2 and process 3 are very small; The pressure level of cabin can reduce about 0.4~0.5 dB(A) with the damping material C3202-25(process 4). Therefore, it is an effective way of acoustic processing to use the damping material on the wall panels.
