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RSS2020 Vol. 39, No. 12
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2020, 39(12): 1805-1812.
doi: 10.13433/j.cnki.1003-8728.20190339
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Abstract:
In this paper, the control strategy of torque distribution is designed and optimized based on the composite braking systesm of electric vehicle. In order to meet the multiobjective requiremaents of braking stability and improve brake energy recovery rate at the same time, a multiobjective optimization algorithm with elite strategy (NSGA-II) is adopted in this paper to solve the problem. At the same time, according to the dsecision making process of Pareto solution set, an improved ideal solution based on fuzzy control is proposed to select the optimal solution. Finally, the simulation on composite braking of electric vehicle is carried out based on Simulink-Cruise joint simulation, and the results verify the proposed decision method is more realistic than the other decision methods.
In this paper, the control strategy of torque distribution is designed and optimized based on the composite braking systesm of electric vehicle. In order to meet the multiobjective requiremaents of braking stability and improve brake energy recovery rate at the same time, a multiobjective optimization algorithm with elite strategy (NSGA-II) is adopted in this paper to solve the problem. At the same time, according to the dsecision making process of Pareto solution set, an improved ideal solution based on fuzzy control is proposed to select the optimal solution. Finally, the simulation on composite braking of electric vehicle is carried out based on Simulink-Cruise joint simulation, and the results verify the proposed decision method is more realistic than the other decision methods.
2020, 39(12): 1813-1821.
doi: 10.13433/j.cnki.1003-8728.20190348
Abstract:
The offset, pinion axis distance and shaft angle of hypoid gear have significant influence on its meshing performance. In view of meshing characteristics of hypoid gear pair with the conditions of advancing or retreating, considering adjustment of different relative installation positions, on the basis of the tooth flank machined with duplex helical method, via tooth contact analysis (TCA) and dynamic analysis, the contact trace, transmission error and dynamic characteristics of concave or convex are studied respectively. The results show that value of limit VH has a noticeable effect on the fluctuation of angular acceleration of concave comparing with convex, and the positive limit V is beneficial to the improvement of the dynamic performance of convex, and the negative limit V is easy to cause edge contact of convex, and the positive limit H is easy to cause edge contact of concave and convex. And the correctness of the TCA is verified by the rolling test. Also, the mapping function between the adjustment of installation position and the displacement of contact trace is established, which providesthe reference for the pre-control of the position of contact trace of tooth flank.
The offset, pinion axis distance and shaft angle of hypoid gear have significant influence on its meshing performance. In view of meshing characteristics of hypoid gear pair with the conditions of advancing or retreating, considering adjustment of different relative installation positions, on the basis of the tooth flank machined with duplex helical method, via tooth contact analysis (TCA) and dynamic analysis, the contact trace, transmission error and dynamic characteristics of concave or convex are studied respectively. The results show that value of limit VH has a noticeable effect on the fluctuation of angular acceleration of concave comparing with convex, and the positive limit V is beneficial to the improvement of the dynamic performance of convex, and the negative limit V is easy to cause edge contact of convex, and the positive limit H is easy to cause edge contact of concave and convex. And the correctness of the TCA is verified by the rolling test. Also, the mapping function between the adjustment of installation position and the displacement of contact trace is established, which providesthe reference for the pre-control of the position of contact trace of tooth flank.
2020, 39(12): 1822-1827.
doi: 10.13433/j.cnki.1003-8728.20200006
Abstract:
In the analysis of the factors affecting the machining accuracy of the machine tool, the vibration caused by the dynamic characteristics of the hydrostatic spindle system is an important factor in the surface waviness of the machined surface. The generation model for waviness is established according to the vibration information of the main shaft, and the sensitivity of the six influencing factors is obtained. The position of the radial bearing is the main factor affecting the surface waviness. Then the evaluation system is established, and the relationship between the generated model and the actual processed surface ripple result is evaluated by using the correlation method, and a correlation coefficient above 0.45 is obtained. Finally, with the power spectral density to extract the spectral characteristics of the spindle system, it is found that the spindle vibration is the main factor affecting the machining accuracy.
In the analysis of the factors affecting the machining accuracy of the machine tool, the vibration caused by the dynamic characteristics of the hydrostatic spindle system is an important factor in the surface waviness of the machined surface. The generation model for waviness is established according to the vibration information of the main shaft, and the sensitivity of the six influencing factors is obtained. The position of the radial bearing is the main factor affecting the surface waviness. Then the evaluation system is established, and the relationship between the generated model and the actual processed surface ripple result is evaluated by using the correlation method, and a correlation coefficient above 0.45 is obtained. Finally, with the power spectral density to extract the spectral characteristics of the spindle system, it is found that the spindle vibration is the main factor affecting the machining accuracy.
2020, 39(12): 1828-1835.
doi: 10.13433/j.cnki.1003-8728.20190349
Abstract:
Parallel external fixation is a new treatment method for ankle fracture, which is an essential problem to study the fracture rehabilitation theory with this treatment method. Based on the clinical rehabilitation concept of continuous passive motion, we design a new passive rehabilitation program for ankle fracture, which drives a parallel external fixator' s movement with the normal motion trajectory. With this program, the experiment for measuring the law of ankle movement is designed. The positions of markers under normal motion state were captured by the three-dimensional measurement system called Optotrak Certus. The motion trajectory of an ankle and its range were calculated with the MATLAB software. The rehabilitation trajectory which conforms with the normal ankle motion law is selected to drive the external fixator' s moving platform move according to the trajectory. The length of each branch chain was calculated with the inverse kinematics of parallel mechanism; thus the complete passive rehabilitation program was formed, effectively rehabilitating ankle fracture with a parallel external fixator.
Parallel external fixation is a new treatment method for ankle fracture, which is an essential problem to study the fracture rehabilitation theory with this treatment method. Based on the clinical rehabilitation concept of continuous passive motion, we design a new passive rehabilitation program for ankle fracture, which drives a parallel external fixator' s movement with the normal motion trajectory. With this program, the experiment for measuring the law of ankle movement is designed. The positions of markers under normal motion state were captured by the three-dimensional measurement system called Optotrak Certus. The motion trajectory of an ankle and its range were calculated with the MATLAB software. The rehabilitation trajectory which conforms with the normal ankle motion law is selected to drive the external fixator' s moving platform move according to the trajectory. The length of each branch chain was calculated with the inverse kinematics of parallel mechanism; thus the complete passive rehabilitation program was formed, effectively rehabilitating ankle fracture with a parallel external fixator.
2020, 39(12): 1836-1843.
doi: 10.13433/j.cnki.1003-8728.20200273
Abstract:
To avoid the adverse effects of transformer vibration and noise on residents′ comfort, a dual-nonlinear vibration isolation system for transformer vibration reduction and noise reduction is designed based on the novel magnetic negative stiffness and geometric nonlinear damping. The theoretical model of magnetic negative stiffness spring is established with the current method, and the analysis on magnetic force and negative stiffness performance is carried out. A displacement-velocity-dependent geometric nonlinear damping is proposed based on electromagnetic shunt damping. The electromechanical coupling characteristic of the geometric nonlinear damping is investigated via the equivalent magnetic charge method. The parameter optimization is carried out as well. The dynamics of the dual-nonlinear isolation system for vibration reduction and noise reduction of transformers are studied by harmonic balance method. Then the low frequency vibration attenuation and noise reduction of the transformer are studied. The results show that the magnetic negative stiffness spring reduces the resonance frequency of the system and broadens the isolation bandwidth. And the low-frequency vibration of the transformer is effectively isolated. Moreover, the geometric nonlinear damping can effectively suppress the resonance without affecting the attenuation in the non-resonant region. Finally, the vibration and noise of the transformer can be significantly controlled.
To avoid the adverse effects of transformer vibration and noise on residents′ comfort, a dual-nonlinear vibration isolation system for transformer vibration reduction and noise reduction is designed based on the novel magnetic negative stiffness and geometric nonlinear damping. The theoretical model of magnetic negative stiffness spring is established with the current method, and the analysis on magnetic force and negative stiffness performance is carried out. A displacement-velocity-dependent geometric nonlinear damping is proposed based on electromagnetic shunt damping. The electromechanical coupling characteristic of the geometric nonlinear damping is investigated via the equivalent magnetic charge method. The parameter optimization is carried out as well. The dynamics of the dual-nonlinear isolation system for vibration reduction and noise reduction of transformers are studied by harmonic balance method. Then the low frequency vibration attenuation and noise reduction of the transformer are studied. The results show that the magnetic negative stiffness spring reduces the resonance frequency of the system and broadens the isolation bandwidth. And the low-frequency vibration of the transformer is effectively isolated. Moreover, the geometric nonlinear damping can effectively suppress the resonance without affecting the attenuation in the non-resonant region. Finally, the vibration and noise of the transformer can be significantly controlled.
2020, 39(12): 1844-1851.
doi: 10.13433/j.cnki.1003-8728.20190346
Abstract:
This paper proposes a new supercharger for small reverse osmosis desalination, coupling a free piston Stirling engine with a reciprocating piston pump into a free piston Stirling engine driven booster pump. First, determine the initial design parameters and establish a structural schematic. Then, using the practical isothermal model modeling, the internal working parameters of the Stirling engine are analyzed. After determining the Stirling engine parameters, the reciprocating pump is modeled using the Bernoulli equation and the one-dimensional unstable flow equation, and the pumping and draining pressure and the pressure change in the pump chamber are obtained. At the same time, the influence of the temperature of the Stirling engine heat source on the output work and the influence factors of the discharge port pressure are studied. Then MATLAB software is used to solve the calculation of the established model. Finally, the output power and efficiency of the whole machine are calculated and compared with the initial set value. It is found that the device theoretically meets the initial working conditions of the design and can operate normally.
This paper proposes a new supercharger for small reverse osmosis desalination, coupling a free piston Stirling engine with a reciprocating piston pump into a free piston Stirling engine driven booster pump. First, determine the initial design parameters and establish a structural schematic. Then, using the practical isothermal model modeling, the internal working parameters of the Stirling engine are analyzed. After determining the Stirling engine parameters, the reciprocating pump is modeled using the Bernoulli equation and the one-dimensional unstable flow equation, and the pumping and draining pressure and the pressure change in the pump chamber are obtained. At the same time, the influence of the temperature of the Stirling engine heat source on the output work and the influence factors of the discharge port pressure are studied. Then MATLAB software is used to solve the calculation of the established model. Finally, the output power and efficiency of the whole machine are calculated and compared with the initial set value. It is found that the device theoretically meets the initial working conditions of the design and can operate normally.
2020, 39(12): 1852-1858.
doi: 10.13433/j.cnki.1003-8728.20190352
Abstract:
To understand the characteristics of the configurationnon-uniqueness in the course of trajectory planning, this paper systemically studied the multi-objective trajectory optimization of a redundant manipulator and established a multi-objectiveoptimization model so as to reduce its motion amplitude, energy consumption and joint motion impact. With the double-mode hybrid differential evolution algorithm (DHDE), the trajectory of the manipulator is optimized, and the numerical solution of inverse kinematics is obtained. The DHDE algorithm uses the principles of the beetle antennae search algorithm to optimize the factor K in the DE/current-to-best/1/bin mode, and the DE/rand/1/bin modeis used as the secondary mode. It has the characteristics of high accuracy, less evolutionary algebra and strong robustness. Simulation and experimental results verify the correctness and practicability of the proposed method.
To understand the characteristics of the configurationnon-uniqueness in the course of trajectory planning, this paper systemically studied the multi-objective trajectory optimization of a redundant manipulator and established a multi-objectiveoptimization model so as to reduce its motion amplitude, energy consumption and joint motion impact. With the double-mode hybrid differential evolution algorithm (DHDE), the trajectory of the manipulator is optimized, and the numerical solution of inverse kinematics is obtained. The DHDE algorithm uses the principles of the beetle antennae search algorithm to optimize the factor K in the DE/current-to-best/1/bin mode, and the DE/rand/1/bin modeis used as the secondary mode. It has the characteristics of high accuracy, less evolutionary algebra and strong robustness. Simulation and experimental results verify the correctness and practicability of the proposed method.
2020, 39(12): 1859-1864.
doi: 10.13433/j.cnki.1003-8728.20190337
Abstract:
The air intake filter of a Roots blower is chosen as the study object, the acoustic finite element method and the computational fluid dynamics method are applied to the numerical simulation of the sound field and flow field in the air filter to analyze the effects of the filter core and its height, inner diameter and outer diameter under different inlet velocities on the transmission loss and pressure loss. Results show that the air filter with filter core has a great improvement on the acoustic performance of high frequency noise above 1200 Hz, which can provide better broadband noise reduction performance than that without a filter core; however, the existence of filter core will result in additional pressure loss. When the height of the filter core varies in the range of 300 to 350 mm, the filter has better acoustic performance and less pressure loss. To improve the acoustic performance of the filter, within the allowable range of pressure loss, increasing the outer diameter of the filter core is a priority option while keeping the filter core thickness constant. This work may provide guidance for the structural design and optimization of air intake filters.
The air intake filter of a Roots blower is chosen as the study object, the acoustic finite element method and the computational fluid dynamics method are applied to the numerical simulation of the sound field and flow field in the air filter to analyze the effects of the filter core and its height, inner diameter and outer diameter under different inlet velocities on the transmission loss and pressure loss. Results show that the air filter with filter core has a great improvement on the acoustic performance of high frequency noise above 1200 Hz, which can provide better broadband noise reduction performance than that without a filter core; however, the existence of filter core will result in additional pressure loss. When the height of the filter core varies in the range of 300 to 350 mm, the filter has better acoustic performance and less pressure loss. To improve the acoustic performance of the filter, within the allowable range of pressure loss, increasing the outer diameter of the filter core is a priority option while keeping the filter core thickness constant. This work may provide guidance for the structural design and optimization of air intake filters.
2020, 39(12): 1865-1871.
doi: 10.13433/j.cnki.1003-8728.20200023
Abstract:
The working conditions of the torque-limited hydrodynamic coupling are always partially filled with liquid, and the internal gas-liquid two-phase flow medium spirally circulates around pump channel and turbine channel. To study the YOX500 hydrodynamic coupling, the transient analysis of the internal flow field of the hydrodynamic coupling is carried out with the sliding grid method and the volume of fluid in the CFD (computational fluid dynamics) software. The changes and rules of its flow field structure are simulated in terms of its two phases, velocity and pressure distribution inside the hydrodynamic coupling. The external characteristics of the hydrodynamic coupling are also calculated and compared with the experimental results. The effectiveness of the CFD numerical calculation method is evaluated, providing a method for the design and optimization of the internal flow passage of the hydrodynamic coupling.
The working conditions of the torque-limited hydrodynamic coupling are always partially filled with liquid, and the internal gas-liquid two-phase flow medium spirally circulates around pump channel and turbine channel. To study the YOX500 hydrodynamic coupling, the transient analysis of the internal flow field of the hydrodynamic coupling is carried out with the sliding grid method and the volume of fluid in the CFD (computational fluid dynamics) software. The changes and rules of its flow field structure are simulated in terms of its two phases, velocity and pressure distribution inside the hydrodynamic coupling. The external characteristics of the hydrodynamic coupling are also calculated and compared with the experimental results. The effectiveness of the CFD numerical calculation method is evaluated, providing a method for the design and optimization of the internal flow passage of the hydrodynamic coupling.
2020, 39(12): 1872-1876.
doi: 10.13433/j.cnki.1003-8728.20190350
Abstract:
In order to overcome the lack of information in the data processing and redundancy and low defect on the fault detection accuracy, using functional principal component with the advantages of strong robustness and stability to fill the extreme learning machine in the lack of stability, combined with the RBF-ELM, a new gear fault detection model was proposed based on FPCA (principal component analysis)-RBF(radial basis function)-ELM(extreme learning machine) method. First, the basis function was used to preprocess the original gear vibration data, and then FPCA was used to extract the characteristic information as the training set to establish the ELM gear fault diagnosis model. Finally, the planetary gear box experimental data were used to verify the fault detection performance, and the fault detection results of the planetary gear box were compared with those of FPCA, FPCA-SVDD and PAC-RBF-ELM. The results show that the FPCA-RBF-ELM method has the highest detection rate and fastest detection efficiency, which can be used for fault detection of planetary gear box. This method is effective and feasible.
In order to overcome the lack of information in the data processing and redundancy and low defect on the fault detection accuracy, using functional principal component with the advantages of strong robustness and stability to fill the extreme learning machine in the lack of stability, combined with the RBF-ELM, a new gear fault detection model was proposed based on FPCA (principal component analysis)-RBF(radial basis function)-ELM(extreme learning machine) method. First, the basis function was used to preprocess the original gear vibration data, and then FPCA was used to extract the characteristic information as the training set to establish the ELM gear fault diagnosis model. Finally, the planetary gear box experimental data were used to verify the fault detection performance, and the fault detection results of the planetary gear box were compared with those of FPCA, FPCA-SVDD and PAC-RBF-ELM. The results show that the FPCA-RBF-ELM method has the highest detection rate and fastest detection efficiency, which can be used for fault detection of planetary gear box. This method is effective and feasible.
2020, 39(12): 1877-1881.
doi: 10.13433/j.cnki.1003-8728.20190351
Abstract:
In order to study the nonlinear frictional vibration of automotive multi-ribbed belts, firstly, a two-degree-of-freedom model of V-ribbed belt nonlinear friction vibration is established. The influence of nonlinear stiffness and preload force on the local stability of the equilibrium point is analyzed by solving the eigenvalue of the system. Secondly, the numerical analysis of the separation and contact state of the belt and the pulley during the vibration process is carried out, and the influence of nonlinear stiffness and preload force on the vibration of the V-ribbed belt is studied. The results of numerical analysis show that the effect of nonlinear stiffness and preload force on system stability is complex. With the increase of nonlinear stiffness, the critical coefficient of friction corresponding to the fork point decreases, the vibration amplitude of the V-ribbed belt decreases gradually, and the vibration stability of the system is gradually improved. However, the excessive nonlinear stiffness will cause large amplitude of the vibration during separation, which will affect the stability of the system. This study provides a theoretical basis for the control of the frictional vibration of the V-ribbed belt.
In order to study the nonlinear frictional vibration of automotive multi-ribbed belts, firstly, a two-degree-of-freedom model of V-ribbed belt nonlinear friction vibration is established. The influence of nonlinear stiffness and preload force on the local stability of the equilibrium point is analyzed by solving the eigenvalue of the system. Secondly, the numerical analysis of the separation and contact state of the belt and the pulley during the vibration process is carried out, and the influence of nonlinear stiffness and preload force on the vibration of the V-ribbed belt is studied. The results of numerical analysis show that the effect of nonlinear stiffness and preload force on system stability is complex. With the increase of nonlinear stiffness, the critical coefficient of friction corresponding to the fork point decreases, the vibration amplitude of the V-ribbed belt decreases gradually, and the vibration stability of the system is gradually improved. However, the excessive nonlinear stiffness will cause large amplitude of the vibration during separation, which will affect the stability of the system. This study provides a theoretical basis for the control of the frictional vibration of the V-ribbed belt.
2020, 39(12): 1882-1888.
doi: 10.13433/j.cnki.1003-8728.20200187
Abstract:
The performance of the feed system is the basic guarantee of the machining accuracy of the machine tool. In order to study the influence of inertia ratio on the motion accuracy and dynamic characteristics of the feed system in operation, the dynamic model of the feed system is established by taking the vibration characteristics of the lead screw and the working table into consideration. Based on Simulink, the mechanical structure dynamics model is combined with the servo drive system model to build the electromechanical coupling simulation model of the feed system. On this basis, the influence law of inertia ratio on the feed system performance is studied. The simulation analysis results show that the inertia ratio has a great influence on the dynamic characteristics of the feed system. The inertia ratio is directly related to the positioning accuracy. The inertia ratio of the optimal positioning accuracy corresponding to the specific feed system mechanical structure has its own characteristics. The dynamic stiffness of feed system decreases with the increase of inertia ratio. The conclusions provide reference for the design of feed system and selection of working conditions.
The performance of the feed system is the basic guarantee of the machining accuracy of the machine tool. In order to study the influence of inertia ratio on the motion accuracy and dynamic characteristics of the feed system in operation, the dynamic model of the feed system is established by taking the vibration characteristics of the lead screw and the working table into consideration. Based on Simulink, the mechanical structure dynamics model is combined with the servo drive system model to build the electromechanical coupling simulation model of the feed system. On this basis, the influence law of inertia ratio on the feed system performance is studied. The simulation analysis results show that the inertia ratio has a great influence on the dynamic characteristics of the feed system. The inertia ratio is directly related to the positioning accuracy. The inertia ratio of the optimal positioning accuracy corresponding to the specific feed system mechanical structure has its own characteristics. The dynamic stiffness of feed system decreases with the increase of inertia ratio. The conclusions provide reference for the design of feed system and selection of working conditions.
2020, 39(12): 1889-1897.
doi: 10.13433/j.cnki.1003-8728.20200002
Abstract:
The flow field around the repair robot in the pipelinevia Fluentwas simulated and analyzed.The influence of the super-heavy oil fluid on the velocity field around the robot was simulated under the environment of super-heavy oil with different viscosity, and the related parts were improved. The influence of the viscosity of super heavy oil on the pressure and viscous force in the surface of the robot is discussed by calculating the surface integral via ANSYS post-processing, and it is concluded that the viscous force also exists as a form of thrust in the environment of super heavy oil. The motion state of robot under different pressure difference is analyzed.
The flow field around the repair robot in the pipelinevia Fluentwas simulated and analyzed.The influence of the super-heavy oil fluid on the velocity field around the robot was simulated under the environment of super-heavy oil with different viscosity, and the related parts were improved. The influence of the viscosity of super heavy oil on the pressure and viscous force in the surface of the robot is discussed by calculating the surface integral via ANSYS post-processing, and it is concluded that the viscous force also exists as a form of thrust in the environment of super heavy oil. The motion state of robot under different pressure difference is analyzed.
2020, 39(12): 1898-1905.
doi: 10.13433/j.cnki.1003-8728.20190345
Abstract:
With the increasing application of carbon fiber reinforced plastics (CFRP) in aircrafts, CFRP milling has become a research hotspot. A set of experiments in UD-CFRP milling for multiple helix tools has been carried out by using hybrid robot at different fiber angle, and the cutting force coefficients in tangential and radical directions are calculated. The results demonstrate that cutting force coefficients can be presented as a sine function of fiber cutting angle. The force model is capable of predicting cutting forces in the milling of CFRP with different process parameters. The effects of the fiber cutting angle on the milling surface quality of CFRP have been investigated. In the milling of CFRP, there are two different types of fiber burrs according to different deflection mechanisms of fiber, type Ⅰ and type Ⅱ. Type Ⅰ fiber burrs are related to the bending of fiber in the laminate plane, type Ⅱ related to the bending of fiber in the laminate plane as well as perpendicular to the laminate plane. The results show that the length of type Ⅰ fiber burrs decreases with the increasing of initial fiber cutting angle βs, the length of type Ⅱ fiber burrs increases with increasing of final fiber cutting angle βe.
With the increasing application of carbon fiber reinforced plastics (CFRP) in aircrafts, CFRP milling has become a research hotspot. A set of experiments in UD-CFRP milling for multiple helix tools has been carried out by using hybrid robot at different fiber angle, and the cutting force coefficients in tangential and radical directions are calculated. The results demonstrate that cutting force coefficients can be presented as a sine function of fiber cutting angle. The force model is capable of predicting cutting forces in the milling of CFRP with different process parameters. The effects of the fiber cutting angle on the milling surface quality of CFRP have been investigated. In the milling of CFRP, there are two different types of fiber burrs according to different deflection mechanisms of fiber, type Ⅰ and type Ⅱ. Type Ⅰ fiber burrs are related to the bending of fiber in the laminate plane, type Ⅱ related to the bending of fiber in the laminate plane as well as perpendicular to the laminate plane. The results show that the length of type Ⅰ fiber burrs decreases with the increasing of initial fiber cutting angle βs, the length of type Ⅱ fiber burrs increases with increasing of final fiber cutting angle βe.
2020, 39(12): 1906-1911.
doi: 10.13433/j.cnki.1003-8728.20200010
Abstract:
Nowadays, the metal additive manufacturing is developing rapidly, and the speed of data processing is also increasing. The traditional serial slicing algorithm cannot meet the requirement of industrial manufacturing. The improvement of heterogeneous parallelization of traditional slice-based topological-based slicing algorithms in the field of metal additive manufacturing is studied. Firstly, the patch topological relationship based data structure is modified, and then the GPU (Graphics processing unit) general parallel architecture CUDA (Compute unified device architecture) technology is used to accelerate the algorithm. In order to use the CUDA architecture for parallel computing, a series of preparations for the data are obtained to improve the performance. It is verified by experiments that the present algorithm greatly improves the intersection time between the triangular patch and the tangent plane, and the efficiency of the whole slicing process is also greatly improved. With the increasing of data amount, the efficiency of the algorithm is more obvious.
Nowadays, the metal additive manufacturing is developing rapidly, and the speed of data processing is also increasing. The traditional serial slicing algorithm cannot meet the requirement of industrial manufacturing. The improvement of heterogeneous parallelization of traditional slice-based topological-based slicing algorithms in the field of metal additive manufacturing is studied. Firstly, the patch topological relationship based data structure is modified, and then the GPU (Graphics processing unit) general parallel architecture CUDA (Compute unified device architecture) technology is used to accelerate the algorithm. In order to use the CUDA architecture for parallel computing, a series of preparations for the data are obtained to improve the performance. It is verified by experiments that the present algorithm greatly improves the intersection time between the triangular patch and the tangent plane, and the efficiency of the whole slicing process is also greatly improved. With the increasing of data amount, the efficiency of the algorithm is more obvious.
2020, 39(12): 1912-1917.
doi: 10.13433/j.cnki.1003-8728.20200008
Abstract:
New Al2O3/La2O3/(W,Mo)Cbinderless tools weremanufactured with spark plasma sinteringfor dry cutting of TC4 alloy comparing with YG8 tool. The results showed that under the same cutting amount, the cutting force and roughness with the Al2O3/La2O3/(W,Mo)Cbinderless cemented carbide toolswere less than that with YG8.Binderless tools had better cutting performance for TC4alloy and were less affected by cutting parameters. Binderless tools had a wider range of cutting amount. The wear of binderless tools for dry cutting TC4 alloy were lower than that with YG8 tool. Wear resistance was better. The wear mechanism of binderless toolswas mainly boundary wear and a small amount of adhesive wear, and a little bit of chipping damage. The wear of YG8 tool was adhesive wear, abrasive wear, and crater wear.
New Al2O3/La2O3/(W,Mo)Cbinderless tools weremanufactured with spark plasma sinteringfor dry cutting of TC4 alloy comparing with YG8 tool. The results showed that under the same cutting amount, the cutting force and roughness with the Al2O3/La2O3/(W,Mo)Cbinderless cemented carbide toolswere less than that with YG8.Binderless tools had better cutting performance for TC4alloy and were less affected by cutting parameters. Binderless tools had a wider range of cutting amount. The wear of binderless tools for dry cutting TC4 alloy were lower than that with YG8 tool. Wear resistance was better. The wear mechanism of binderless toolswas mainly boundary wear and a small amount of adhesive wear, and a little bit of chipping damage. The wear of YG8 tool was adhesive wear, abrasive wear, and crater wear.
2020, 39(12): 1918-1922.
doi: 10.13433/j.cnki.1003-8728.20190312
Abstract:
In the milling, most of the cutting tools are radial feed and the peripheral cutting edge is the main cutting edge. There are many researches on the peripheral cutting edge, but there is a lack of research on the end cutting edge. Therefore, the simulation and experimental research on the condition that only the end cutting edge engages in the cutting is conducted. By analyzing the chip morphology in simulation and the surface roughness in experiment, the minimum undeformed chip thickness in simulation and cutting experiments are determined respectively. Simulation and experimental results show that there is no significant difference between the simulation value and the experimental of the minimum undeformed chip thickness, and the minimum undeformed chip thickness is 0.61 ~ 0.70 times of the cutting edge radius. According to the simulation results, it is found that the chip formation is affected by the cutting speed. The present study can be used to guide the selection and quantification of different cutting edge radius and machining parameters of workpiece materials in micro milling, which has an important guiding for reducing the tool wear and improving the processing quality of workpiece.
In the milling, most of the cutting tools are radial feed and the peripheral cutting edge is the main cutting edge. There are many researches on the peripheral cutting edge, but there is a lack of research on the end cutting edge. Therefore, the simulation and experimental research on the condition that only the end cutting edge engages in the cutting is conducted. By analyzing the chip morphology in simulation and the surface roughness in experiment, the minimum undeformed chip thickness in simulation and cutting experiments are determined respectively. Simulation and experimental results show that there is no significant difference between the simulation value and the experimental of the minimum undeformed chip thickness, and the minimum undeformed chip thickness is 0.61 ~ 0.70 times of the cutting edge radius. According to the simulation results, it is found that the chip formation is affected by the cutting speed. The present study can be used to guide the selection and quantification of different cutting edge radius and machining parameters of workpiece materials in micro milling, which has an important guiding for reducing the tool wear and improving the processing quality of workpiece.
2020, 39(12): 1923-1929.
doi: 10.13433/j.cnki.1003-8728.20200052
Abstract:
In order to investigate the effect of the ultrasonic rolling extrusion on the surface work hardening of 42CrMo bearing steel. With the orthogonal test, range analysis and variance analysis, the influence rule, significance and contribution rate of the process parameters on the work hardening degree were explored, and the prediction model for the work hardening degree of the ultrasonic roll extrusion surface was established with the stepwise regression method. The results show that the ultrasonic amplitude and static pressure are the main factors affecting the strain of 42CrMo bearing steel, while the rotational speed and feed speed of workpiece affect the strain distribution; the amplitude surface work hardening degree has the greatest influence, the contribution rate is of 71.61%, the feed speed is the smallest, the contribution rate is only of 0.41%; the surface hardening degree increases with the increasing of ultrasonic amplitude and static pressure, and increases firstly with the increasing of workpiece rotational speed. The prediction model based on the stepwise regression prediction model is basically consistent with the measured results, and the prediction model has strong overall significance, high reliability and prediction ability.
In order to investigate the effect of the ultrasonic rolling extrusion on the surface work hardening of 42CrMo bearing steel. With the orthogonal test, range analysis and variance analysis, the influence rule, significance and contribution rate of the process parameters on the work hardening degree were explored, and the prediction model for the work hardening degree of the ultrasonic roll extrusion surface was established with the stepwise regression method. The results show that the ultrasonic amplitude and static pressure are the main factors affecting the strain of 42CrMo bearing steel, while the rotational speed and feed speed of workpiece affect the strain distribution; the amplitude surface work hardening degree has the greatest influence, the contribution rate is of 71.61%, the feed speed is the smallest, the contribution rate is only of 0.41%; the surface hardening degree increases with the increasing of ultrasonic amplitude and static pressure, and increases firstly with the increasing of workpiece rotational speed. The prediction model based on the stepwise regression prediction model is basically consistent with the measured results, and the prediction model has strong overall significance, high reliability and prediction ability.
2020, 39(12): 1930-1936.
doi: 10.13433/j.cnki.1003-8728.20200009
Abstract:
The large impact and wear of the latch lock mechanism is caused by closing the vehicle door under the large sealing reaction force. A novel ratchet pawl lock mechanism with main and auxiliary pawls is proposed, and the auxiliary pawl composed of the spring linkage mechanism is constructed. The novel lock mechanism replaces the rigid impact of the conventional lock mechanism by the auxiliary pawl flexible impact and the delayed main pawl rigid impact, in which loads reduce the impact and wear during the lock process of the lock mechanism, and the singular configuration of the spring linkage mechanism enables fast switching between the main and auxiliary pawls. Through the force transmission characteristic analysis, the hinge position of the pawl on the main pawl is ensured, the initial state and motion characteristics of the main and auxiliary pawls are guaranteed, and the influence of the stiffness of the auxiliary pawl spring on the delay and contact force of the main pawl is discussed. Finally, the Adams simulation results show that when the auxiliary ratchet spring stiffness is 2.75\begin{document}${\rm{N/mm}}$\end{document} ![]()
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The large impact and wear of the latch lock mechanism is caused by closing the vehicle door under the large sealing reaction force. A novel ratchet pawl lock mechanism with main and auxiliary pawls is proposed, and the auxiliary pawl composed of the spring linkage mechanism is constructed. The novel lock mechanism replaces the rigid impact of the conventional lock mechanism by the auxiliary pawl flexible impact and the delayed main pawl rigid impact, in which loads reduce the impact and wear during the lock process of the lock mechanism, and the singular configuration of the spring linkage mechanism enables fast switching between the main and auxiliary pawls. Through the force transmission characteristic analysis, the hinge position of the pawl on the main pawl is ensured, the initial state and motion characteristics of the main and auxiliary pawls are guaranteed, and the influence of the stiffness of the auxiliary pawl spring on the delay and contact force of the main pawl is discussed. Finally, the Adams simulation results show that when the auxiliary ratchet spring stiffness is 2.75
2020, 39(12): 1937-1943.
doi: 10.13433/j.cnki.1003-8728.20190353
Abstract:
The topological and geometric control of the morphology of a rope belt in the knotting process iskeyto the development of a new knotting mechanism. Based on the Reidemeister fundamental transformation of the knot theory, the equivalent operation and formation principles of the rope beltduring the overhand knot forming process are proposed. A new knotting mechanism is built with the non-integral hollow gear disk that drives rope belt winding and the arc facade cam thatsupports the rope belt. The movable arm gripper picks up and fixes the rope belt. The topological and geometric combination index is constructed by using the cross-points of the rope belt and the extreme points of the catenary, and the knotting process is divided into four key stages. The geometric form of the boundary transient rope belt is solved by using the catenary theory. The experimental results show that the topological and geometriccontrol of the morphology of the boundary transient rope belt is realized and that the shape of the rope belt is maintained in the knotting process of the new knotting mechanism.
The topological and geometric control of the morphology of a rope belt in the knotting process iskeyto the development of a new knotting mechanism. Based on the Reidemeister fundamental transformation of the knot theory, the equivalent operation and formation principles of the rope beltduring the overhand knot forming process are proposed. A new knotting mechanism is built with the non-integral hollow gear disk that drives rope belt winding and the arc facade cam thatsupports the rope belt. The movable arm gripper picks up and fixes the rope belt. The topological and geometric combination index is constructed by using the cross-points of the rope belt and the extreme points of the catenary, and the knotting process is divided into four key stages. The geometric form of the boundary transient rope belt is solved by using the catenary theory. The experimental results show that the topological and geometriccontrol of the morphology of the boundary transient rope belt is realized and that the shape of the rope belt is maintained in the knotting process of the new knotting mechanism.
2020, 39(12): 1944-1951.
doi: 10.13433/j.cnki.1003-8728.20190338
Abstract:
Aiming at the problem of excessive noise in shearer pick load signal, a wavelet denoising algorithm based on smooth condensation function was proposed in this paper. In order to evaluate the denoising effect more comprehensively, a comprehensive evaluation index S was constructed. According to the characteristics of pick load signal, noise blocks, bumps and leleleccum were respectively selected as test signals. The denoising effect of the test signal was the best when the sym5 wavelet base was decomposed into three layers by comprehensive evaluation. The results show that this method has the best denoising effect when compared with the soft and hard threshold wavelet denoising algorithms. The synthetical evaluation indexes S of block, bumps and lelccum signals are 0.31, 021 and 0.15 respectively. Compared with traditional methods, the denoising effect of this method is improved by 0.02-0.09. Finally, this method is applied to the denoising of pick load signals and good results are obtained.
Aiming at the problem of excessive noise in shearer pick load signal, a wavelet denoising algorithm based on smooth condensation function was proposed in this paper. In order to evaluate the denoising effect more comprehensively, a comprehensive evaluation index S was constructed. According to the characteristics of pick load signal, noise blocks, bumps and leleleccum were respectively selected as test signals. The denoising effect of the test signal was the best when the sym5 wavelet base was decomposed into three layers by comprehensive evaluation. The results show that this method has the best denoising effect when compared with the soft and hard threshold wavelet denoising algorithms. The synthetical evaluation indexes S of block, bumps and lelccum signals are 0.31, 021 and 0.15 respectively. Compared with traditional methods, the denoising effect of this method is improved by 0.02-0.09. Finally, this method is applied to the denoising of pick load signals and good results are obtained.
2020, 39(12): 1952-1956.
doi: 10.13433/j.cnki.1003-8728.20190341
Abstract:
A simulation platform for the two-way coupling of computational fluid dynamics (CFD) and multi-body dynamics (MBD) was established for transient analysis of the aerodynamic characteristics of the van semi-trailer in bridge and tunnel connection section under crosswind conditions. On the basis of considering the relative movement of the tractor and the semi-trailer, the aerodynamic loads and the surrounding flow fields of the vehicle are analyzed when the vehicle travels through different positions, and the crosswind stability of the vehicle is evaluated by the yaw angle and the lateral displacement. The simulation results show that the relative motion of the tractor and semi-trailer will increase the amplitude of yaw angle, lateral displacement and aerodynamic load of the van semi-trailer when driving on the bridge and tunnel connection, and fixing tractor and semi-trailer can improve the crosswind stability of the vehicle.
A simulation platform for the two-way coupling of computational fluid dynamics (CFD) and multi-body dynamics (MBD) was established for transient analysis of the aerodynamic characteristics of the van semi-trailer in bridge and tunnel connection section under crosswind conditions. On the basis of considering the relative movement of the tractor and the semi-trailer, the aerodynamic loads and the surrounding flow fields of the vehicle are analyzed when the vehicle travels through different positions, and the crosswind stability of the vehicle is evaluated by the yaw angle and the lateral displacement. The simulation results show that the relative motion of the tractor and semi-trailer will increase the amplitude of yaw angle, lateral displacement and aerodynamic load of the van semi-trailer when driving on the bridge and tunnel connection, and fixing tractor and semi-trailer can improve the crosswind stability of the vehicle.
2020, 39(12): 1957-1962.
doi: 10.13433/j.cnki.1003-8728.20200272
Abstract:
To improve the properties of the friction welded joints of TiAl and GH3039 dissimilar alloys, the key welding parameters were optimized. The temperature of the welding interface was measured in real-time by using the semi-natural thermocouple. The interfacial microstructure and fracture morphology of the friction welded joint were investigated by using the scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). It is found that the length out of the constraint sleeve of GH3039 had a great influence on the tensile strength of the joint. The joint strength reached 374 MPa at a length of 4.1 mm. The relationship between the thermoelectric potential of NiSi-GH3039 hot junction and the temperature was established. During the quasi-stabilized friction stage, the interfacial temperature at 960 −1 030 °C was consistent with the superplastic temperature of TiAl alloy. No defect such as crack and cavity was found in the welding interface. Five intermediate phase layers were formed in the welding zone. The fracture of the joint was mainly occurred in the Al3NiTi2 brittle phase layer, and the primary fracture morphology was in the form of the uneven friction ring.
To improve the properties of the friction welded joints of TiAl and GH3039 dissimilar alloys, the key welding parameters were optimized. The temperature of the welding interface was measured in real-time by using the semi-natural thermocouple. The interfacial microstructure and fracture morphology of the friction welded joint were investigated by using the scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). It is found that the length out of the constraint sleeve of GH3039 had a great influence on the tensile strength of the joint. The joint strength reached 374 MPa at a length of 4.1 mm. The relationship between the thermoelectric potential of NiSi-GH3039 hot junction and the temperature was established. During the quasi-stabilized friction stage, the interfacial temperature at 960 −1 030 °C was consistent with the superplastic temperature of TiAl alloy. No defect such as crack and cavity was found in the welding interface. Five intermediate phase layers were formed in the welding zone. The fracture of the joint was mainly occurred in the Al3NiTi2 brittle phase layer, and the primary fracture morphology was in the form of the uneven friction ring.
2020, 39(12): 1963-1968.
doi: 10.13433/j.cnki.1003-8728.20190347
Abstract:
Surface extension has a wide application of the composite materials mold design in the aviation industry. A novel method is proposed for complex surfaces which cannot be directly extended by using CAD software. Complex surfaces are discretized into triangular meshes and expressed in STL files. The topological relationships among the patches are used to reconstruct STL files so as to detect the inner holes and outer boundaries of the surface, and then the meshes are generated alongside the boundaries. In order to avoid the generation of gap and intersection, the concave and convex angular points of the surface are detected and processed separately. In order to improve the quality of extension and avoid unexpected grids, a step-by-step extension algorithm is adopted and appropriate step length is calculated. Finally, the data is reconstructed by using CATIA' s reverse engineering module so as to verify the effectiveness of the algorithm.
Surface extension has a wide application of the composite materials mold design in the aviation industry. A novel method is proposed for complex surfaces which cannot be directly extended by using CAD software. Complex surfaces are discretized into triangular meshes and expressed in STL files. The topological relationships among the patches are used to reconstruct STL files so as to detect the inner holes and outer boundaries of the surface, and then the meshes are generated alongside the boundaries. In order to avoid the generation of gap and intersection, the concave and convex angular points of the surface are detected and processed separately. In order to improve the quality of extension and avoid unexpected grids, a step-by-step extension algorithm is adopted and appropriate step length is calculated. Finally, the data is reconstructed by using CATIA' s reverse engineering module so as to verify the effectiveness of the algorithm.
2020, 39(12): 1969-1974.
doi: 10.13433/j.cnki.1003-8728.20200001
Abstract:
In view of the problem that the current Remaining Useful Life (RUL) prediction method does not consider the influence of maintenance factors in the engine performance degradation stage, a new method for predicting the civil aviation engine' s RUL by considering the performance degradation model under imperfect maintenance is proposed. The performance degradation of civil aviation engines was modeled using a Wiener process with drift points. According to the historical performance degradation data and the historical maintenance record data, the model parameters are estimated by the maximum likelihood estimation algorithm to realize the RUL prediction of the aeroengine. The actual monitoring data of the engine is used to verify the prediction results. The results show that the method can better track the actual performance degradation process of the engine, and the prediction accuracy is higher, which can provide a basis for the formulation of the civil aviation engine maintenance plan analysis.
In view of the problem that the current Remaining Useful Life (RUL) prediction method does not consider the influence of maintenance factors in the engine performance degradation stage, a new method for predicting the civil aviation engine' s RUL by considering the performance degradation model under imperfect maintenance is proposed. The performance degradation of civil aviation engines was modeled using a Wiener process with drift points. According to the historical performance degradation data and the historical maintenance record data, the model parameters are estimated by the maximum likelihood estimation algorithm to realize the RUL prediction of the aeroengine. The actual monitoring data of the engine is used to verify the prediction results. The results show that the method can better track the actual performance degradation process of the engine, and the prediction accuracy is higher, which can provide a basis for the formulation of the civil aviation engine maintenance plan analysis.
