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RSS2020 Vol. 39, No. 7
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2020, 39(7): 985-991.
doi: 10.13433/j.cnki.1003-8728.20190231
PDF 4986KB
Abstract:
In order to study the transient flow of solid-liquid mixed fluid during the vibration stirring process of the flow field in the mixing cylinder of the two-bedroom shaft vibration mixer, based on the calculation method of computational fluid mechanics (CFD), combined with dynamic mesh technology, Euler multiphase phase flow model, realizable k-ε turbulence model and discrete phase model, the user-defined program (UDF) is developed using C language, and linked dynamically to CFD. In the unsteady conditions, the mixing quality of the two-bedroom shaft vibration mixer by the vibration shaft speed, solid particle volume fraction of the influence of the law are numerically simulated. And on this basis, the vibration stirring test is researched. The results show that when the mixing shaft speed is 35 r/min, and the mixture particle volume fraction is 20%, and the particle diameter is 10 mm, 20 mm and 30 mm respectively, the vibration shaft speed is 960 r/min, 1 460 r/min and 1 800 r/min respectively, the stirring quality is the best. The numerical simulation results are basically consistent with the experimental conclusions, which show the accuracy of the numerical calculation results and the feasibility of the calculation method.
In order to study the transient flow of solid-liquid mixed fluid during the vibration stirring process of the flow field in the mixing cylinder of the two-bedroom shaft vibration mixer, based on the calculation method of computational fluid mechanics (CFD), combined with dynamic mesh technology, Euler multiphase phase flow model, realizable k-ε turbulence model and discrete phase model, the user-defined program (UDF) is developed using C language, and linked dynamically to CFD. In the unsteady conditions, the mixing quality of the two-bedroom shaft vibration mixer by the vibration shaft speed, solid particle volume fraction of the influence of the law are numerically simulated. And on this basis, the vibration stirring test is researched. The results show that when the mixing shaft speed is 35 r/min, and the mixture particle volume fraction is 20%, and the particle diameter is 10 mm, 20 mm and 30 mm respectively, the vibration shaft speed is 960 r/min, 1 460 r/min and 1 800 r/min respectively, the stirring quality is the best. The numerical simulation results are basically consistent with the experimental conclusions, which show the accuracy of the numerical calculation results and the feasibility of the calculation method.
2020, 39(7): 992-999.
doi: 10.13433/j.cnki.1003-8728.20200108
Abstract:
An improved adaptive filtering algorithm for active noise control (ANC) is proposed, and the experimental device for ANC of duct noise is set up, in which the controllable thin-plate vibration and loudspeaker are as secondary sound sources, respectively. The results show that:in the low frequency band, the active noise control effect with controllable thin-plate vibration as the secondary sound source is less than that of the traditional loudspeaker, but the noise reduction effect of controllable thin-plate vibration as the secondary sound source is much better in the middle and high frequency. From 1 200 Hz to the cut-off frequency of the duct, the attenuation of the downstream of duct with thin-plate vibration as the secondary sound source before and after controlled, is up to 50 dB, it is about 10 dB higher than the traditional secondary loudspeaker. In duct active noise elimination, the low frequency noise is mainly eliminated, however, due to the good directivity of the plate sound source, it can be extended from the active control of the duct noise to the active control of the space noise, in order to make up the shortcoming of the insufficient sound radiation ability of the plate in the low frequency band.
An improved adaptive filtering algorithm for active noise control (ANC) is proposed, and the experimental device for ANC of duct noise is set up, in which the controllable thin-plate vibration and loudspeaker are as secondary sound sources, respectively. The results show that:in the low frequency band, the active noise control effect with controllable thin-plate vibration as the secondary sound source is less than that of the traditional loudspeaker, but the noise reduction effect of controllable thin-plate vibration as the secondary sound source is much better in the middle and high frequency. From 1 200 Hz to the cut-off frequency of the duct, the attenuation of the downstream of duct with thin-plate vibration as the secondary sound source before and after controlled, is up to 50 dB, it is about 10 dB higher than the traditional secondary loudspeaker. In duct active noise elimination, the low frequency noise is mainly eliminated, however, due to the good directivity of the plate sound source, it can be extended from the active control of the duct noise to the active control of the space noise, in order to make up the shortcoming of the insufficient sound radiation ability of the plate in the low frequency band.
2020, 39(7): 1000-1004.
doi: 10.13433/j.cnki.1003-8728.20200046
Abstract:
The vibration signal of planetary gear tooth surface wear-out failure has some disadvantages such as weak feature and little feature quantity. Therefore, it is difficult to identify the wear-out failure feature of planetary gear tooth surface. In order to solve this problem, a new fault diagnosis method is put forward. Firstly, the amplitude of the original vibration acceleration signal is used as pixels to construct a gray-scale image, and the feature points of the gray-scale image are detected and the detected feature point vectors are described. Then, the feature description vectors of the gray-scale image are clustered to construct a bag of words model. Finally, the histogram intersection kernel support vector machine algorithm is used to classify the gray-scale image. This method not only does not need to decompose the original signal and reduce the signal noise, but also can extract a large number of signal features, and improve the efficiency and accuracy of fault feature detection. Experiments were carried out to diagnose the normal gear teeth, fault gears with two tooth surfaces wear and three tooth surfaces wear, and the diagnosis accuracy was up to 98.55%. Experimental results show that the proposed method is effective.
The vibration signal of planetary gear tooth surface wear-out failure has some disadvantages such as weak feature and little feature quantity. Therefore, it is difficult to identify the wear-out failure feature of planetary gear tooth surface. In order to solve this problem, a new fault diagnosis method is put forward. Firstly, the amplitude of the original vibration acceleration signal is used as pixels to construct a gray-scale image, and the feature points of the gray-scale image are detected and the detected feature point vectors are described. Then, the feature description vectors of the gray-scale image are clustered to construct a bag of words model. Finally, the histogram intersection kernel support vector machine algorithm is used to classify the gray-scale image. This method not only does not need to decompose the original signal and reduce the signal noise, but also can extract a large number of signal features, and improve the efficiency and accuracy of fault feature detection. Experiments were carried out to diagnose the normal gear teeth, fault gears with two tooth surfaces wear and three tooth surfaces wear, and the diagnosis accuracy was up to 98.55%. Experimental results show that the proposed method is effective.
2020, 39(7): 1005-1013.
doi: 10.13433/j.cnki.1003-8728.20190249
Abstract:
Extrusion Free-forming (EFF) is a 3D printing additive manufacturing technology which applies external pressure to the slurry packaged in the cartridge, forcing it to squeeze through the micro flow channel, and stacking layer by layer on the X and Y planes. Direct manufacturing of ceramic parts can be achieved via extrusion forming technology, during the printing process, the smooth transition of the forming platform at the inflection point of the path, the extrusion speed of the material and the scanning speed of the forming platform is one of the important methods to improve the forming precision. Based on the speed matching algorithm and scan path information, a control system with STM32 as the core is established, which can pre-plan the scan speed, match the feed rate and scanning speed, so as to provide certain reference value for improving the forming precision of ceramic parts.
Extrusion Free-forming (EFF) is a 3D printing additive manufacturing technology which applies external pressure to the slurry packaged in the cartridge, forcing it to squeeze through the micro flow channel, and stacking layer by layer on the X and Y planes. Direct manufacturing of ceramic parts can be achieved via extrusion forming technology, during the printing process, the smooth transition of the forming platform at the inflection point of the path, the extrusion speed of the material and the scanning speed of the forming platform is one of the important methods to improve the forming precision. Based on the speed matching algorithm and scan path information, a control system with STM32 as the core is established, which can pre-plan the scan speed, match the feed rate and scanning speed, so as to provide certain reference value for improving the forming precision of ceramic parts.
2020, 39(7): 1014-1021.
doi: 10.13433/j.cnki.1003-8728.20190246
Abstract:
With the large-scale atomic/molecular massively parallel simulator (LAMMPS), the molecular dynamics of molecular motion trajectories of graphene lubricants in the ultrasonic environment is simulated. The diffusion coefficient of graphene molecules is calculated by using the molecular root mean square displacement equation, and the ultrasonic dispersion mechanism is revealed from the microscopic point of view. By adjusting the functional parameters of the ultrasonic disperser and changing its ultrasonic time and frequency, the dispersion stability of the obtained graphene lubricating oil was measured with the zeta potential, and the dispersion stability of graphene in lubricating oil was characterized with the zeta potential. The results show that the dispersion stability of the graphene lubricating oil has a positive correlation curve with ultrasonic time and power to some extent. When the ultrasonic time exceeds 105 min and the ultrasonic power exceeds 600 W, the dispersion stability decreases.
With the large-scale atomic/molecular massively parallel simulator (LAMMPS), the molecular dynamics of molecular motion trajectories of graphene lubricants in the ultrasonic environment is simulated. The diffusion coefficient of graphene molecules is calculated by using the molecular root mean square displacement equation, and the ultrasonic dispersion mechanism is revealed from the microscopic point of view. By adjusting the functional parameters of the ultrasonic disperser and changing its ultrasonic time and frequency, the dispersion stability of the obtained graphene lubricating oil was measured with the zeta potential, and the dispersion stability of graphene in lubricating oil was characterized with the zeta potential. The results show that the dispersion stability of the graphene lubricating oil has a positive correlation curve with ultrasonic time and power to some extent. When the ultrasonic time exceeds 105 min and the ultrasonic power exceeds 600 W, the dispersion stability decreases.
2020, 39(7): 1022-1027.
doi: 10.13433/j.cnki.1003-8728.20190233
Abstract:
In order to solve the problem that the number of decomposition layers K of the variational mode decomposition (VMD) is difficult to select. It is proposed to use the normalized Shannon entropy to optimize the parameters of the variational mode decomposition, so that the number K can be determined adaptively, signal over and lack of decomposition can be avoided. First, the number of decomposition layers in the program is set so that the program can be pre-decomposed. Then Shannon entropy of each intrinsic modal function (IMF) band after decomposition is calculated and normalized, and the normalized entropy value is used as the loop stop condition to adaptively determine the decomposition layer number K. Finally, the envelope analysis of each IMF component is carried out to extract the fault features in the signal. This method is analyzed and verified by using the simulated signal and the actual fault data. The results show that the method can self-adaptively determine the K value, and at the same time, the decomposed IMF components contain regular fault vibration signals or frequency doubling of frequency conversion. It is proved that this fault feature extraction method is effective.
In order to solve the problem that the number of decomposition layers K of the variational mode decomposition (VMD) is difficult to select. It is proposed to use the normalized Shannon entropy to optimize the parameters of the variational mode decomposition, so that the number K can be determined adaptively, signal over and lack of decomposition can be avoided. First, the number of decomposition layers in the program is set so that the program can be pre-decomposed. Then Shannon entropy of each intrinsic modal function (IMF) band after decomposition is calculated and normalized, and the normalized entropy value is used as the loop stop condition to adaptively determine the decomposition layer number K. Finally, the envelope analysis of each IMF component is carried out to extract the fault features in the signal. This method is analyzed and verified by using the simulated signal and the actual fault data. The results show that the method can self-adaptively determine the K value, and at the same time, the decomposed IMF components contain regular fault vibration signals or frequency doubling of frequency conversion. It is proved that this fault feature extraction method is effective.
2020, 39(7): 1028-1034.
doi: 10.13433/j.cnki.1003-8728.20200107
Abstract:
To realize co-simulation of machine-liquid-control system of high voltage circuit breaker, two servers and clients of TCP communication for hydraulic system model and fluid simulation model were developed by using C and C# programming languages, respectively. The secondary development dynamics model was carried out by using Fortran programming language. The co-simulation system was established to realize the interaction of above software through Shared memory. Secondly, the simulation models of hydraulic control system, operating mechanism and arc extinguishing chamber were built to employ the co-simulation of the circuit breaker. Finally, the velocity characteristics of the operating mechanism in the opening process are analyzed, and the influence of the initial oil pressure of the energy storage cylinder on the movement characteristics of the operating mechanism is discussed. The results show that the co-simulation system realizes the machine-liquid-control co-simulation function.
To realize co-simulation of machine-liquid-control system of high voltage circuit breaker, two servers and clients of TCP communication for hydraulic system model and fluid simulation model were developed by using C and C# programming languages, respectively. The secondary development dynamics model was carried out by using Fortran programming language. The co-simulation system was established to realize the interaction of above software through Shared memory. Secondly, the simulation models of hydraulic control system, operating mechanism and arc extinguishing chamber were built to employ the co-simulation of the circuit breaker. Finally, the velocity characteristics of the operating mechanism in the opening process are analyzed, and the influence of the initial oil pressure of the energy storage cylinder on the movement characteristics of the operating mechanism is discussed. The results show that the co-simulation system realizes the machine-liquid-control co-simulation function.
2020, 39(7): 1035-1039.
doi: 10.13433/j.cnki.1003-8728.20190271
Abstract:
Gantry milling machine is widely used in precision machining of large-scale parts of aviation and aerospace. Geometric and Thermal errors have significant influence on machining accuracy. A compensation method of multiple geometric and thermal deformation for gantry milling machine is proposed, based on SIEMENS 840D numerical control system, and the key error analysis, identification and modeling methods of large machine proposed in this paper, after the establishment of mathematical models of the thermal error of the spindle and the geometric and thermal comprehensive error of the main feed axis. The compensation system was developed, which can realize the real time control compensation of thermal errors of spindle system, and geometric and thermal errors of the main feeding (x) axis.
Gantry milling machine is widely used in precision machining of large-scale parts of aviation and aerospace. Geometric and Thermal errors have significant influence on machining accuracy. A compensation method of multiple geometric and thermal deformation for gantry milling machine is proposed, based on SIEMENS 840D numerical control system, and the key error analysis, identification and modeling methods of large machine proposed in this paper, after the establishment of mathematical models of the thermal error of the spindle and the geometric and thermal comprehensive error of the main feed axis. The compensation system was developed, which can realize the real time control compensation of thermal errors of spindle system, and geometric and thermal errors of the main feeding (x) axis.
2020, 39(7): 1040-1047.
doi: 10.13433/j.cnki.1003-8728.20190237
Abstract:
The straightness variation in precision linear feed system caused by its thermal effect can significantly affect the accuracy stability of machine. For this problem, the effect of the thermal variation on the straightness in precision linear feed system is simulated. Firstly, the model for temperature simulation in feed system is established by using finite element thermal-fluid-solid coupling technology. Based on it, the simulation model for thermal deformation in feed system is established. Then, the simulation results of thermal deformation are analyzed to obtain estimation models for thermal increment of straightness error and thermal drift of its base line in the feed system. Finally, the accuracy of the s analysis model for traightness thermal variation in the precision linear feed system is verified by experiment. The results show that machine comprehensive thermal factor has obvious influence on the thermal drift of straightness error base line in the precision linear feed system, but has a relatively small influence on the thermal increment of straightness error. The main factor causing the effect of the thermal variation on the straightness is the thermal drift of bed-guide assembly surface caused by the thermal deformation of machine bed.
The straightness variation in precision linear feed system caused by its thermal effect can significantly affect the accuracy stability of machine. For this problem, the effect of the thermal variation on the straightness in precision linear feed system is simulated. Firstly, the model for temperature simulation in feed system is established by using finite element thermal-fluid-solid coupling technology. Based on it, the simulation model for thermal deformation in feed system is established. Then, the simulation results of thermal deformation are analyzed to obtain estimation models for thermal increment of straightness error and thermal drift of its base line in the feed system. Finally, the accuracy of the s analysis model for traightness thermal variation in the precision linear feed system is verified by experiment. The results show that machine comprehensive thermal factor has obvious influence on the thermal drift of straightness error base line in the precision linear feed system, but has a relatively small influence on the thermal increment of straightness error. The main factor causing the effect of the thermal variation on the straightness is the thermal drift of bed-guide assembly surface caused by the thermal deformation of machine bed.
2020, 39(7): 1048-1052.
doi: 10.13433/j.cnki.1003-8728.20190250
Abstract:
Using the RD8000 to map pipeline routing, a non-contact metal magnetic memory detector is used to collect the tube segment signal directly above the buried ferromagnetic pipeline. The data is filtered through the Savitzky-Golay filter. It is found that when the magnetic induction normal component change gradient Kz crosses zero and the magnetic induction tangential component change gradient Ky has an extreme value, the feature position can be judged as the girth weld position. By comparing the relative distance ΔL1 of the adjacent ring welds in the magnetic signal diagram with the length ΔL2 of the construction period, the construction period number corresponding to the girth weld in the magnetic signal diagram can be matched. Finally, the GPS information collected by the magnetic memory tester is combined to determine the geographical position of the target ring weld.
Using the RD8000 to map pipeline routing, a non-contact metal magnetic memory detector is used to collect the tube segment signal directly above the buried ferromagnetic pipeline. The data is filtered through the Savitzky-Golay filter. It is found that when the magnetic induction normal component change gradient Kz crosses zero and the magnetic induction tangential component change gradient Ky has an extreme value, the feature position can be judged as the girth weld position. By comparing the relative distance ΔL1 of the adjacent ring welds in the magnetic signal diagram with the length ΔL2 of the construction period, the construction period number corresponding to the girth weld in the magnetic signal diagram can be matched. Finally, the GPS information collected by the magnetic memory tester is combined to determine the geographical position of the target ring weld.
2020, 39(7): 1053-1059.
doi: 10.13433/j.cnki.1003-8728.20190238
Abstract:
To study the material removal mechanism in the electrochemical discharge drilling (ECDD) process, a series of experimental investigation for ANSI 304 stainless steel work-pieces were carried out with a high-speed rotating tungsten carbide helical tool-electrode, and high-speed camera was used to observe the bubbles generation, the gas film formation and the electric spark discharge phenomenon in the drilling process. The material removal mechanism in the electrochemical discharge drilling is further revealed by analyzing the signal waveform of the drilling current and the spark discharge phenomena at different rotational speed. The experimental results show that at the high rotational speed of tool-electrode, the material of work-piece is mainly eroded via the combination of the electrical discharge machining(EDM) and the electrochemical machining(ECM); at the extremely lower or stationary rotational speed of tool-electrode, the material of work-piece is merely etched via ECM.
To study the material removal mechanism in the electrochemical discharge drilling (ECDD) process, a series of experimental investigation for ANSI 304 stainless steel work-pieces were carried out with a high-speed rotating tungsten carbide helical tool-electrode, and high-speed camera was used to observe the bubbles generation, the gas film formation and the electric spark discharge phenomenon in the drilling process. The material removal mechanism in the electrochemical discharge drilling is further revealed by analyzing the signal waveform of the drilling current and the spark discharge phenomena at different rotational speed. The experimental results show that at the high rotational speed of tool-electrode, the material of work-piece is mainly eroded via the combination of the electrical discharge machining(EDM) and the electrochemical machining(ECM); at the extremely lower or stationary rotational speed of tool-electrode, the material of work-piece is merely etched via ECM.
2020, 39(7): 1060-1065.
doi: 10.13433/j.cnki.1003-8728.20190245
Abstract:
Because it is difficult to calibrate the parameters of the airbag polishing tool of an industrial robot, a new method for calibrating the parameters of the tool's coordinate system is presented. This paper first introduces the calibration principles of the coordinate system, establishes each coordinate system. Then according to the position relationship between workpiece turntable and robot, it puts forward the tool's parameter calibration algorithm that depends on only the robot system itself and can be realized by attitude transformation and simple geometric mathematical calculation. Finally, the ER20D-C10 robot is used as the test platform to calibrate the parameters of the airbag polishing tool and to compare our calibration method with the traditional calibration method. The results show that our calibration method is easy to use and highly precise, thus meeting the technical requirements for robot airbag polishing.
Because it is difficult to calibrate the parameters of the airbag polishing tool of an industrial robot, a new method for calibrating the parameters of the tool's coordinate system is presented. This paper first introduces the calibration principles of the coordinate system, establishes each coordinate system. Then according to the position relationship between workpiece turntable and robot, it puts forward the tool's parameter calibration algorithm that depends on only the robot system itself and can be realized by attitude transformation and simple geometric mathematical calculation. Finally, the ER20D-C10 robot is used as the test platform to calibrate the parameters of the airbag polishing tool and to compare our calibration method with the traditional calibration method. The results show that our calibration method is easy to use and highly precise, thus meeting the technical requirements for robot airbag polishing.
2020, 39(7): 1066-1070.
doi: 10.13433/j.cnki.1003-8728.20200106
Abstract:
For off-shore oil and gas exploitation requirements, a thin-walled optical-fiber air-bubble pressure sensor and its fabricating method is proposed. Ethanol is locked in the optical-fiber air-bubble by splicing a single mode fiber to a silica tube with electric arc discharge method. The optical fiber air bubble is expanded by using various intensity electrical arc discharges. The thin-walled optical fiber air bubble with a thickness of several hundred nanometers can be achieved, which shows greatly improved pressure and temperature sensing characteristics compared with some conventional fiber bubbles. Experimental results indicate that the proposed new sensors based on thin-walled optical-fiber air-bubble shows a high pressure sensitivity of 1 313 pm/MPa, meanwhile the temperature cross-sensitivity is 8.644 kPa/℃.
For off-shore oil and gas exploitation requirements, a thin-walled optical-fiber air-bubble pressure sensor and its fabricating method is proposed. Ethanol is locked in the optical-fiber air-bubble by splicing a single mode fiber to a silica tube with electric arc discharge method. The optical fiber air bubble is expanded by using various intensity electrical arc discharges. The thin-walled optical fiber air bubble with a thickness of several hundred nanometers can be achieved, which shows greatly improved pressure and temperature sensing characteristics compared with some conventional fiber bubbles. Experimental results indicate that the proposed new sensors based on thin-walled optical-fiber air-bubble shows a high pressure sensitivity of 1 313 pm/MPa, meanwhile the temperature cross-sensitivity is 8.644 kPa/℃.
2020, 39(7): 1071-1076.
doi: 10.13433/j.cnki.1003-8728.20190223
Abstract:
This paper studies the image clarity evaluation of the film hole encountered during the visual measurement of cooling film hole (hereinafter referred to as:film hole) in the high pressure turbine blade. Using optical imaging system to analyze the influence of the system defocus on the image clarity, and the evaluation method of image clarity combining Sobel operator and threshold is proposed. Aiming at small pore size of gas film, reflection of single crystal material, difficulty in obtaining focal plane and difficulty in identifying the edge of film hole, and a measurement method combining normalization of image clarity evaluation function with threshold selection has been designed by designing the contrast experiments. This method ensures the authenticity of the evaluation function and eliminates high-frequency noise. The experimental results show that the present evaluation method can accurately evaluate the clarity of the film hole image. The method has strong unimodality, unbiasedness, and also has a good signal to noise ratio.
This paper studies the image clarity evaluation of the film hole encountered during the visual measurement of cooling film hole (hereinafter referred to as:film hole) in the high pressure turbine blade. Using optical imaging system to analyze the influence of the system defocus on the image clarity, and the evaluation method of image clarity combining Sobel operator and threshold is proposed. Aiming at small pore size of gas film, reflection of single crystal material, difficulty in obtaining focal plane and difficulty in identifying the edge of film hole, and a measurement method combining normalization of image clarity evaluation function with threshold selection has been designed by designing the contrast experiments. This method ensures the authenticity of the evaluation function and eliminates high-frequency noise. The experimental results show that the present evaluation method can accurately evaluate the clarity of the film hole image. The method has strong unimodality, unbiasedness, and also has a good signal to noise ratio.
2020, 39(7): 1077-1085.
doi: 10.13433/j.cnki.1003-8728.20190241
Abstract:
Aiming at the nonlinear and non-stationary characteristics of the vibration signal of the ball mill, and the shortcomings of the overall average empirical mode decomposition denoising method (CEEMDAN) neglecting the high-frequency component and the wavelet threshold denoising method, a CEEMDAN-wavelet threshold combined denoising method is proposed to process ball mill vibration signal. Firstly, the CEEMDAN algorithm is used to decompose the signal into a series of IMF components. Secondly, the continuous mean square error criterion is used to determine the high-frequency IMF components with more noise. Then the wavelet threshold denoising method is used to denoise the high-frequency IMF components with more noise. Finally, the denoised IMF component and the denoised IMF component are reconstructed to obtain a denoised vibration signal. The denoising analysis of the vibration signal of the measured ball mill barrel shows that the combined signal denoising method proposed in this study has higher signal-to-noise ratio and lower root mean square error, which proves that the method has higher denoising.
Aiming at the nonlinear and non-stationary characteristics of the vibration signal of the ball mill, and the shortcomings of the overall average empirical mode decomposition denoising method (CEEMDAN) neglecting the high-frequency component and the wavelet threshold denoising method, a CEEMDAN-wavelet threshold combined denoising method is proposed to process ball mill vibration signal. Firstly, the CEEMDAN algorithm is used to decompose the signal into a series of IMF components. Secondly, the continuous mean square error criterion is used to determine the high-frequency IMF components with more noise. Then the wavelet threshold denoising method is used to denoise the high-frequency IMF components with more noise. Finally, the denoised IMF component and the denoised IMF component are reconstructed to obtain a denoised vibration signal. The denoising analysis of the vibration signal of the measured ball mill barrel shows that the combined signal denoising method proposed in this study has higher signal-to-noise ratio and lower root mean square error, which proves that the method has higher denoising.
2020, 39(7): 1086-1093.
doi: 10.13433/j.cnki.1003-8728.20190230
Abstract:
In order to optimize the hydraulic performance of an artificial heart pump and reduce blood damage, the influence of its main structural parameters on efficiency, head and hemolysis values was analyzed with computational fluid dynamics. The univariate feature selection method was used to select the outlet diameter D2, the blade wrap angle ψ and the outlet width b2. Variables were based on the efficiency, head and hemolysis values of the artificial heart pump. The response surface method was used to fit the multiple regression model of design variables and the objective function. Finally, multi-objective optimization was performed with the NSGA-Ⅱ genetic algorithm. The optimal impeller outlet sizes are determined as:D2=41.68 mm, ψ=101.8°, b2=2.4 mm. At this time, the performance parameters of the artificial heart pump are:efficiency 0.753 6, head 100.219 mmHg, hemolysis value 0.018 1 g/100L. The hydraulic efficiency and hemolysis performance are superior to the original model, while the head meets the design requirements.
In order to optimize the hydraulic performance of an artificial heart pump and reduce blood damage, the influence of its main structural parameters on efficiency, head and hemolysis values was analyzed with computational fluid dynamics. The univariate feature selection method was used to select the outlet diameter D2, the blade wrap angle ψ and the outlet width b2. Variables were based on the efficiency, head and hemolysis values of the artificial heart pump. The response surface method was used to fit the multiple regression model of design variables and the objective function. Finally, multi-objective optimization was performed with the NSGA-Ⅱ genetic algorithm. The optimal impeller outlet sizes are determined as:D2=41.68 mm, ψ=101.8°, b2=2.4 mm. At this time, the performance parameters of the artificial heart pump are:efficiency 0.753 6, head 100.219 mmHg, hemolysis value 0.018 1 g/100L. The hydraulic efficiency and hemolysis performance are superior to the original model, while the head meets the design requirements.
2020, 39(7): 1094-1099.
doi: 10.13433/j.cnki.1003-8728.20190247
Abstract:
In order to improve driving stability of intelligent vehicle in the process of trajectory tracking, a trajectory tracking and stability control method is proposed for four-wheel steering (4WS) vehicle. Firstly, the three-degree-of-freedom dynamic model of the 4WS intelligent vehicle is established. Then the model predictive control algorithm is used to design the trajectory tracking controller. Considering the dynamic characteristics of 4WS vehicle and the influence of different road surface on tire slip angle control, zero side slip angle control and dynamic tire slip angle boundary control methods are introduced to achieve stability control of the vehicle. Finally, through the simulation of the joint road conditions, it is verified that the proposed control method can ensure the driving stability of the vehicle in the trajectory tracking process.
In order to improve driving stability of intelligent vehicle in the process of trajectory tracking, a trajectory tracking and stability control method is proposed for four-wheel steering (4WS) vehicle. Firstly, the three-degree-of-freedom dynamic model of the 4WS intelligent vehicle is established. Then the model predictive control algorithm is used to design the trajectory tracking controller. Considering the dynamic characteristics of 4WS vehicle and the influence of different road surface on tire slip angle control, zero side slip angle control and dynamic tire slip angle boundary control methods are introduced to achieve stability control of the vehicle. Finally, through the simulation of the joint road conditions, it is verified that the proposed control method can ensure the driving stability of the vehicle in the trajectory tracking process.
2020, 39(7): 1100-1106.
doi: 10.13433/j.cnki.1003-8728.20190225
Abstract:
In order to improve the safety and comfort of drivers, a hierarchical cruise control system is proposed. The system divides the cruise condition into several different modes, which can realize the control of the vehicle speed by adjusting the engine's rotation speed. In the upper controller, studying the cruise control mode decision problem, and checking whether the cruise mode to be entered is allowed. In the middle controller, studying whether the cruise control condition is established; if it is established, exit the cruise; if it is not established, continue the strategy. In the lower controller, the PID is used to control the cruising target speed, the actual speed and the engine speed. On this basis, the real-time hardware-in-the-loop of strategy is carried out, mainly verifying the deceleration-hold mode, acceleration-hold mode, and acceleration-deceleration-set up mode. The test results show that the strategy can achieve the purpose of acceleration and deceleration according to the driver's intention, which can improve the safety and comfort of the vehicle.
In order to improve the safety and comfort of drivers, a hierarchical cruise control system is proposed. The system divides the cruise condition into several different modes, which can realize the control of the vehicle speed by adjusting the engine's rotation speed. In the upper controller, studying the cruise control mode decision problem, and checking whether the cruise mode to be entered is allowed. In the middle controller, studying whether the cruise control condition is established; if it is established, exit the cruise; if it is not established, continue the strategy. In the lower controller, the PID is used to control the cruising target speed, the actual speed and the engine speed. On this basis, the real-time hardware-in-the-loop of strategy is carried out, mainly verifying the deceleration-hold mode, acceleration-hold mode, and acceleration-deceleration-set up mode. The test results show that the strategy can achieve the purpose of acceleration and deceleration according to the driver's intention, which can improve the safety and comfort of the vehicle.
2020, 39(7): 1107-1113.
doi: 10.13433/j.cnki.1003-8728.20190248
Abstract:
The double-gradient drilling technology can be used to solve the problems in the development of deep-sea oil and gas and shallow gas hydrate, and the low pressure of the formation leakage and the like. In order to study the mechanical properties of the pressure-blocking packer rubber tube in the double-gradient drilling casing, the effects of different friction coefficient, thickness of the rubber tube, working pressure, ring space and other factors on the deformation of the rubber cylinder were analyzed by means of the finite element simulation software. The maximum Mises stresses value and the contact pressure value of the rubber tube under the four factor groups were analyzed with the orthogonal test. The results show that the contact pressure between the rubber tube and the casing can be obtained with a friction coefficient of 0.3, the thickness of the rubber tube of the double-gradient drilling packer is preferably 15 mm, and the minimum friction force of the packer rubber tube with the drill string is 33 845 N under the condition of effective sealing of the working pressure of 2 MPa. The main factors that affect the maximum Mises stresses of the rubber tube are the working pressure and the ring space; and the main factors that influence the maximum contact pressure between the rubber tube and the casing are the working pressure and thickness of the rubber tube.
The double-gradient drilling technology can be used to solve the problems in the development of deep-sea oil and gas and shallow gas hydrate, and the low pressure of the formation leakage and the like. In order to study the mechanical properties of the pressure-blocking packer rubber tube in the double-gradient drilling casing, the effects of different friction coefficient, thickness of the rubber tube, working pressure, ring space and other factors on the deformation of the rubber cylinder were analyzed by means of the finite element simulation software. The maximum Mises stresses value and the contact pressure value of the rubber tube under the four factor groups were analyzed with the orthogonal test. The results show that the contact pressure between the rubber tube and the casing can be obtained with a friction coefficient of 0.3, the thickness of the rubber tube of the double-gradient drilling packer is preferably 15 mm, and the minimum friction force of the packer rubber tube with the drill string is 33 845 N under the condition of effective sealing of the working pressure of 2 MPa. The main factors that affect the maximum Mises stresses of the rubber tube are the working pressure and the ring space; and the main factors that influence the maximum contact pressure between the rubber tube and the casing are the working pressure and thickness of the rubber tube.
2020, 39(7): 1114-1120.
doi: 10.13433/j.cnki.1003-8728.20190235
Abstract:
Through low cycle fatigue experiments of the cast magnesium alloy AZ91D and the wrought magnesium alloy AZ31B at room temperature under stress control, the low cycle fatigue damage evolution of magnesium alloys was divided into the initial damage stage, the stable damage stage and the rapid damage stage at the end of the cycle by selecting the change of the mean strain as the damage variable based on the continuum damage mechanics. And the damage of each stage above mentioned was mainly caused by nucleation damage, micro-crack damage and main crack damage respectively. On this basis, the three stage damage model and the two stage damage model were developed. And then, the low cycle fatigue damage evolution was analyzed by using the above-mentioned damage models. Results show that comparing with the classic model for low cycle fatigue damage, the damage curves obtained by the three stage damage model and the two stage damage model are in a better agreement with the experimental, and which can better reflect the low cycle fatigue damage evolution process of magnesium alloys.
Through low cycle fatigue experiments of the cast magnesium alloy AZ91D and the wrought magnesium alloy AZ31B at room temperature under stress control, the low cycle fatigue damage evolution of magnesium alloys was divided into the initial damage stage, the stable damage stage and the rapid damage stage at the end of the cycle by selecting the change of the mean strain as the damage variable based on the continuum damage mechanics. And the damage of each stage above mentioned was mainly caused by nucleation damage, micro-crack damage and main crack damage respectively. On this basis, the three stage damage model and the two stage damage model were developed. And then, the low cycle fatigue damage evolution was analyzed by using the above-mentioned damage models. Results show that comparing with the classic model for low cycle fatigue damage, the damage curves obtained by the three stage damage model and the two stage damage model are in a better agreement with the experimental, and which can better reflect the low cycle fatigue damage evolution process of magnesium alloys.
2020, 39(7): 1121-1127.
doi: 10.13433/j.cnki.1003-8728.20190243
Abstract:
The stress-magnetization effect of the pipeline under internal pressure and geomagnetic field is simulated via ANSYS, and the model for stress distribution and magnetic signal distribution of pipeline under different corrosion spacing and different corrosion depths were obtained. At the same time, the small buried pipeline of the pipe section under the jurisdiction of Qinghai Oilfield was tested with the weak magnetic detector of pipeline. The location of the corrosion defect was determined by analyzing the waveform characteristics of the gradient values of the magnetic induction components of the pipeline surface dBX, dBY and dBZ. Comparing the test results with the simulated, it is proved that the two results have a good consistency. The results show that it is reasonable to use the waveform characteristics of the magnetic signal of the pipeline to judge the corrosion defects. It can early diagnose the buried pipelines under trenchless conditions, and provide theoretical basis for the weak magnetic detection technology.
The stress-magnetization effect of the pipeline under internal pressure and geomagnetic field is simulated via ANSYS, and the model for stress distribution and magnetic signal distribution of pipeline under different corrosion spacing and different corrosion depths were obtained. At the same time, the small buried pipeline of the pipe section under the jurisdiction of Qinghai Oilfield was tested with the weak magnetic detector of pipeline. The location of the corrosion defect was determined by analyzing the waveform characteristics of the gradient values of the magnetic induction components of the pipeline surface dBX, dBY and dBZ. Comparing the test results with the simulated, it is proved that the two results have a good consistency. The results show that it is reasonable to use the waveform characteristics of the magnetic signal of the pipeline to judge the corrosion defects. It can early diagnose the buried pipelines under trenchless conditions, and provide theoretical basis for the weak magnetic detection technology.
2020, 39(7): 1128-1132.
doi: 10.13433/j.cnki.1003-8728.20190232
Abstract:
Powder metallurgy was an advanced manufacturing technology in saving energy, saving material, high efficiency and near-net forming, while the mechanical theory of powder metallurgy in the pressing process was the key problem that determined the compactness and uniformity of the pressed blank and has a decisive influence on the quality of the final product. A numerical analytical model for uniaxial pressing of powder metallurgy was established via discrete element method (DEM). Using the present model, the force chain evolution law, the stress variation law, as well as the variation of coordination number and the variation of sliding fraction were studied. The research results showed that the strength of microscopic force chain among powder granules gradually increased with the descending of upper die. In addition, the meso-force chains in the later pressing stage also showed obviously directional characteristics along the y-axis. The stress in x and y direction was smaller in the initial pressing stage, moreover, the stress in x and y direction increased linearly with the descending of upper die in the later pressing stage. The coordination number was smaller in the initial pressing stage, moreover, the coordination number increased with the descending of upper die in the later pressing stage. The sliding fraction was smaller in the initial and later pressing stage, moreover, the sliding fraction was larger at the middle pressing stage.
Powder metallurgy was an advanced manufacturing technology in saving energy, saving material, high efficiency and near-net forming, while the mechanical theory of powder metallurgy in the pressing process was the key problem that determined the compactness and uniformity of the pressed blank and has a decisive influence on the quality of the final product. A numerical analytical model for uniaxial pressing of powder metallurgy was established via discrete element method (DEM). Using the present model, the force chain evolution law, the stress variation law, as well as the variation of coordination number and the variation of sliding fraction were studied. The research results showed that the strength of microscopic force chain among powder granules gradually increased with the descending of upper die. In addition, the meso-force chains in the later pressing stage also showed obviously directional characteristics along the y-axis. The stress in x and y direction was smaller in the initial pressing stage, moreover, the stress in x and y direction increased linearly with the descending of upper die in the later pressing stage. The coordination number was smaller in the initial pressing stage, moreover, the coordination number increased with the descending of upper die in the later pressing stage. The sliding fraction was smaller in the initial and later pressing stage, moreover, the sliding fraction was larger at the middle pressing stage.
2020, 39(7): 1133-1138.
doi: 10.13433/j.cnki.1003-8728.20190242
Abstract:
Space net is a new on-orbit acquisition technology, it is of great significance to solve its increasingly tense space environment problems. Based on the finite element method, the space net is discretized into several rope segment elements. Its dynamic model is deduced through analyzing the force of the elements. The dynamics model of the collision between the space net and its acquisition target is established with the penalty method. Their simulation model is established with the ABAQUS finite element software, and the dynamics of the acquisition process is simulated. The evaluation index of the acquisition effect of the space net is put forward. The difference between different targets in the acquisition process of the space net is discussed in detail. The simulation results show that the collision force between the space net and the spherical object is the largest, the encapsulation of the cube object is the best, and the increment of the velocity and the displacement of the cube object after collision are the largest.
Space net is a new on-orbit acquisition technology, it is of great significance to solve its increasingly tense space environment problems. Based on the finite element method, the space net is discretized into several rope segment elements. Its dynamic model is deduced through analyzing the force of the elements. The dynamics model of the collision between the space net and its acquisition target is established with the penalty method. Their simulation model is established with the ABAQUS finite element software, and the dynamics of the acquisition process is simulated. The evaluation index of the acquisition effect of the space net is put forward. The difference between different targets in the acquisition process of the space net is discussed in detail. The simulation results show that the collision force between the space net and the spherical object is the largest, the encapsulation of the cube object is the best, and the increment of the velocity and the displacement of the cube object after collision are the largest.
2020, 39(7): 1139-1148.
doi: 10.13433/j.cnki.1003-8728.20190236
Abstract:
The nonlinear dynamic model of the double-span rotor system under the rolling bearing bearing is established. The fourth-order-five-step fixed-step Runge-Kutta method is used to analyze the nonlinear dynamic model. The dynamic responses of the rotor with the change of the speed under the five conditions of no fault, rubbing fault, crack fault, one end loose fault and rubbing-crack-loose coupling fault are compared respectively. The effects of rotor unbalance, rubbing stiffness and loose bearing housing quality on system response under rubbing-crack-loose coupling failure conditions are numerically analyzed. The results show that when the system has a rubbing fault, the first-order critical speed is increased slightly and the dynamic behavior is more complicated; when there is a crack fault, the first-order critical speed is reduced; when there is a loose fault, the response chaotic area becomes larger; when there are three kinds of coupling faults, the super first-order critical speed response appears large-area chaos; with the increase of rotor unbalance and rubbing stiffness, the response tends to chaos, and the quality of the loose end bearing seat is sensitive at high speed.
The nonlinear dynamic model of the double-span rotor system under the rolling bearing bearing is established. The fourth-order-five-step fixed-step Runge-Kutta method is used to analyze the nonlinear dynamic model. The dynamic responses of the rotor with the change of the speed under the five conditions of no fault, rubbing fault, crack fault, one end loose fault and rubbing-crack-loose coupling fault are compared respectively. The effects of rotor unbalance, rubbing stiffness and loose bearing housing quality on system response under rubbing-crack-loose coupling failure conditions are numerically analyzed. The results show that when the system has a rubbing fault, the first-order critical speed is increased slightly and the dynamic behavior is more complicated; when there is a crack fault, the first-order critical speed is reduced; when there is a loose fault, the response chaotic area becomes larger; when there are three kinds of coupling faults, the super first-order critical speed response appears large-area chaos; with the increase of rotor unbalance and rubbing stiffness, the response tends to chaos, and the quality of the loose end bearing seat is sensitive at high speed.
