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RSS2018 Vol. 37, No. 8
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2018, 37(8): 1149-1155.
doi: 10.13433/j.cnki.1003-8728.20180024
PDF 892KB
Abstract:
The dynamic reliability of mechanical system failure can be described by dynamic Vine Copula model. The Vine Copula function is used to transform the reliability problems of complex and multiple failures related to the analysis of multiple two-dimensional dynamic Copula functions; using the nonparametric estimation algorithm, the empirical distribution function-local maximum likelihood two-step method is proposed to estimate the time-varying parameters in the dynamic Copula function; next, a dynamic Vine Copula model is established to describe the reliability of multi-failure dynamic related mechanical systems. The study focus on the mechanical system of the series system reliability modeling and analysis, then solve out the reliability of the mechanical system. Finally, an example is given to demonstrate the rationality and validity of the method.
The dynamic reliability of mechanical system failure can be described by dynamic Vine Copula model. The Vine Copula function is used to transform the reliability problems of complex and multiple failures related to the analysis of multiple two-dimensional dynamic Copula functions; using the nonparametric estimation algorithm, the empirical distribution function-local maximum likelihood two-step method is proposed to estimate the time-varying parameters in the dynamic Copula function; next, a dynamic Vine Copula model is established to describe the reliability of multi-failure dynamic related mechanical systems. The study focus on the mechanical system of the series system reliability modeling and analysis, then solve out the reliability of the mechanical system. Finally, an example is given to demonstrate the rationality and validity of the method.
2018, 37(8): 1156-1160.
doi: 10.13433/j.cnki.1003-8728.20180048
Abstract:
On account of the manufacturing error of rod length, the expansion mechanism of underwater detection array will produce the position error during extended movement, which leads to the track tracing deviation of transducers and hence affects the detection performance. A underwater expansion mechanism based on the closed-vector method and the principle of independent error function is studied. A position accuracy analysis model for submarine extension mechanism with rod-length error is established. Meanwhile, the effect ofthe eight rod errors and input angles on the position error of underwater expansion mechanism in the process of actual expansion is also studied. A mechanism kinematics analysis method in rod length error is proposed, which makes transducer trace the movement trail in a different ways on different manufacturing accuracy.
On account of the manufacturing error of rod length, the expansion mechanism of underwater detection array will produce the position error during extended movement, which leads to the track tracing deviation of transducers and hence affects the detection performance. A underwater expansion mechanism based on the closed-vector method and the principle of independent error function is studied. A position accuracy analysis model for submarine extension mechanism with rod-length error is established. Meanwhile, the effect ofthe eight rod errors and input angles on the position error of underwater expansion mechanism in the process of actual expansion is also studied. A mechanism kinematics analysis method in rod length error is proposed, which makes transducer trace the movement trail in a different ways on different manufacturing accuracy.
2018, 37(8): 1161-1166.
doi: 10.13433/j.cnki.1003-8728.20180025
Abstract:
As typical biological, the body and the movement of the silkworm is observed and analyzed by the method of shooting measurement, and the shape and dynamic characteristics of silkworm movement are obtained. The structure scheme of the bionic robot was designed by the link mechanism. The scheme of silkworm-robot is established by modular structures. The virtual prototype model of machine silkworm is set up. And throgh ADAMS simulation, the motion form of silkworm-robot is realized. The changes of joint torque is analysed, the two dimension peristaltic prototype is made, and the creeping experiment is carried out.
As typical biological, the body and the movement of the silkworm is observed and analyzed by the method of shooting measurement, and the shape and dynamic characteristics of silkworm movement are obtained. The structure scheme of the bionic robot was designed by the link mechanism. The scheme of silkworm-robot is established by modular structures. The virtual prototype model of machine silkworm is set up. And throgh ADAMS simulation, the motion form of silkworm-robot is realized. The changes of joint torque is analysed, the two dimension peristaltic prototype is made, and the creeping experiment is carried out.
2018, 37(8): 1167-1176.
doi: 10.13433/j.cnki.1003-8728.20180029
Abstract:
In order to solve the traditional interpolation method of manipulator running slowly, this paper adopts a structuring Jacobi function approach to interpolation on the target curve, calculates the Jacobi matrix of each point on the curve according to the target curve, and forms a Jacobi matrix function. Then the target curve is fitted out the end effector speed function and each arm angular velocity function at the joint. Therefore, this paper calculates the Jacobi matrix of each position in real-time to obtain the speed of each joint according to end effector speed, which ensures that the end effector speed is controllable at each position in the workspace. At last, KUKA KR30-3 industrial robot model is used to simulate and validate this method, and its simulation analysis is done in helmet processing. The simulation results show that the speed function of each joint angle of manipulator can be calculated according to the end effector position function, and the continuity of velocity can be guaranteed when the singularity of the manipulator is avoided.
In order to solve the traditional interpolation method of manipulator running slowly, this paper adopts a structuring Jacobi function approach to interpolation on the target curve, calculates the Jacobi matrix of each point on the curve according to the target curve, and forms a Jacobi matrix function. Then the target curve is fitted out the end effector speed function and each arm angular velocity function at the joint. Therefore, this paper calculates the Jacobi matrix of each position in real-time to obtain the speed of each joint according to end effector speed, which ensures that the end effector speed is controllable at each position in the workspace. At last, KUKA KR30-3 industrial robot model is used to simulate and validate this method, and its simulation analysis is done in helmet processing. The simulation results show that the speed function of each joint angle of manipulator can be calculated according to the end effector position function, and the continuity of velocity can be guaranteed when the singularity of the manipulator is avoided.
2018, 37(8): 1177-1182.
doi: 10.13433/j.cnki.1003-8728.20180012
Abstract:
According to the feed system of a CNC machine center, based on the analysis of mechanical properties of a double-drive ball screw feed system, with the friction of its worktable considered, the theoretical model of synchronization error is developed and solved by MATLAB/Simulink. The impact of structural parameters and other factors on the synchronization error is analyzed. The synchronization error of the worktable under uniform motion and S-shaped curve motion is measured with experiments and compared with the results of the theoretical model. The results show that the synchronization error of the feed system is caused by the twist angle due to the geometric error and different structural parameters of the two sides of the worktable during movement. The model can predict well the synchronization error.
According to the feed system of a CNC machine center, based on the analysis of mechanical properties of a double-drive ball screw feed system, with the friction of its worktable considered, the theoretical model of synchronization error is developed and solved by MATLAB/Simulink. The impact of structural parameters and other factors on the synchronization error is analyzed. The synchronization error of the worktable under uniform motion and S-shaped curve motion is measured with experiments and compared with the results of the theoretical model. The results show that the synchronization error of the feed system is caused by the twist angle due to the geometric error and different structural parameters of the two sides of the worktable during movement. The model can predict well the synchronization error.
2018, 37(8): 1183-1189.
doi: 10.13433/j.cnki.1003-8728.20180136
Abstract:
A new robust control strategy is presented for a class of nonlinear piezoelectric actuators subject to external disturbances, hysteresis and other time-varying uncertainties. Based on the fast nonsingular terminal sliding mode control, the proposed controller incorporates the time delay estimation, and can achieve online estimation and compensation for the time-varying system uncertainties without system model. The robust exact differentiator is introduced to estimate the velocity and acceleration information online, which overcomes the limitation of only position measurements. Compared with the traditional time delay control, the proposed control law uses the nonlinear sliding mode surface such that the finite-time convergence of tracking error can be guaranteed. Finally, a Lyapunov function is chosen to prove the stability of controlled system. Theoretical analysis and simulation results show that the proposed control strategy can meet the requirements of high-precision robust tracking in micro/nano positioning applications.
A new robust control strategy is presented for a class of nonlinear piezoelectric actuators subject to external disturbances, hysteresis and other time-varying uncertainties. Based on the fast nonsingular terminal sliding mode control, the proposed controller incorporates the time delay estimation, and can achieve online estimation and compensation for the time-varying system uncertainties without system model. The robust exact differentiator is introduced to estimate the velocity and acceleration information online, which overcomes the limitation of only position measurements. Compared with the traditional time delay control, the proposed control law uses the nonlinear sliding mode surface such that the finite-time convergence of tracking error can be guaranteed. Finally, a Lyapunov function is chosen to prove the stability of controlled system. Theoretical analysis and simulation results show that the proposed control strategy can meet the requirements of high-precision robust tracking in micro/nano positioning applications.
2018, 37(8): 1190-1194.
doi: 10.13433/j.cnki.1003-8728.20180001
Abstract:
The signal denoising preprocessing is very important for extracting weak fault features from mechanical vibration signals in strong noise background. However for wavelet transform (WT) and other traditional signal processing algorithms, the processing of signal denoising is a troublesome thing. The balance between signal denoising and feature preserving is a couple of contradictions. Thus we mean to bring in the Perona-Malik nonlinear anisotropy diffusion filtering model to process signal preprocessing in strong noise. Firstly, the partial differential equation (PDE) theory is introduced, and the Perona-Malik model, as one of important nonlinear anisotropy diffusion filtering algorithms, is brought in. Secondly, from the applications in image denoising, it can be analyzed and inferred that the Perona-Malik model is a perfect solution for wavelet transform and other traditional signal denoiseing algorithms. Lastly, by comparison with the wavelet threshold denoising algorithms in the bearing vibration signals, it can be indicated that the Perona-Malik model is very appropriate for mechanical vibration signals in strong noise. Above all, the Perona-Malik filter can not only realize signal denoising but also preserve signal features with better denoising performance and without signal distortions.
The signal denoising preprocessing is very important for extracting weak fault features from mechanical vibration signals in strong noise background. However for wavelet transform (WT) and other traditional signal processing algorithms, the processing of signal denoising is a troublesome thing. The balance between signal denoising and feature preserving is a couple of contradictions. Thus we mean to bring in the Perona-Malik nonlinear anisotropy diffusion filtering model to process signal preprocessing in strong noise. Firstly, the partial differential equation (PDE) theory is introduced, and the Perona-Malik model, as one of important nonlinear anisotropy diffusion filtering algorithms, is brought in. Secondly, from the applications in image denoising, it can be analyzed and inferred that the Perona-Malik model is a perfect solution for wavelet transform and other traditional signal denoiseing algorithms. Lastly, by comparison with the wavelet threshold denoising algorithms in the bearing vibration signals, it can be indicated that the Perona-Malik model is very appropriate for mechanical vibration signals in strong noise. Above all, the Perona-Malik filter can not only realize signal denoising but also preserve signal features with better denoising performance and without signal distortions.
2018, 37(8): 1195-1199.
doi: 10.13433/j.cnki.1003-8728.20180105
Abstract:
An intelligent balancing strategy of influence coefficient table was presented to solve the online active balancing problem of rotor with one balancing plane and one testing point. Mathematical model of influence coefficient table method for rotor online active balancing was established in this paper, its control stability was analyzed and implementation scheme was designed. Numerical simulation of rotor single-plane single-point influence coefficient table method was carried out; the online active balancing iteration process with accurate and inaccurate initial influence coefficient cases was quantitatively given. By contrast analysis of the proposed method with adaptive and self-correcting algorithms, it is proven that the proposed method is feasible for the stable rotor, and it has the significant advantage of improving the online active balancing efficiency.
An intelligent balancing strategy of influence coefficient table was presented to solve the online active balancing problem of rotor with one balancing plane and one testing point. Mathematical model of influence coefficient table method for rotor online active balancing was established in this paper, its control stability was analyzed and implementation scheme was designed. Numerical simulation of rotor single-plane single-point influence coefficient table method was carried out; the online active balancing iteration process with accurate and inaccurate initial influence coefficient cases was quantitatively given. By contrast analysis of the proposed method with adaptive and self-correcting algorithms, it is proven that the proposed method is feasible for the stable rotor, and it has the significant advantage of improving the online active balancing efficiency.
2018, 37(8): 1200-1206.
doi: 10.13433/j.cnki.1003-8728.2018.0801
Abstract:
The end effect exists in envelope fitting during the process of applying EMD method to diagnose mechanical fault. A revised method of boundary extension is proposed based on linear extrapolation method and similar extreme extension method considering the internal signal extreme waving condition in this paper. The variance of internal signal is calculated to evaluate the degree of signal stability. In the case of the signal waves smoothly, similar extreme extension method is conducted to maintain the inherent steadiness at utmost. While the signal that changes abnormally swings violently, the local information at the edges is considered only to conduct linear extrapolation method. Through simulation analysis and tests of fault diagnosis of rolling bearings, results demonstrate this method can suppress end effect of EMD method.
The end effect exists in envelope fitting during the process of applying EMD method to diagnose mechanical fault. A revised method of boundary extension is proposed based on linear extrapolation method and similar extreme extension method considering the internal signal extreme waving condition in this paper. The variance of internal signal is calculated to evaluate the degree of signal stability. In the case of the signal waves smoothly, similar extreme extension method is conducted to maintain the inherent steadiness at utmost. While the signal that changes abnormally swings violently, the local information at the edges is considered only to conduct linear extrapolation method. Through simulation analysis and tests of fault diagnosis of rolling bearings, results demonstrate this method can suppress end effect of EMD method.
2018, 37(8): 1207-1216.
doi: 10.13433/j.cnki.1003-8728.20180009
Abstract:
In this paper, three types of potential field are proposed to solve global congestion and human obstacle avoidance in the practical operation of multiple robots. The social potential field determines the interaction force among the robots and ensures their avoidance foundation. The behavior potential field aims to strike a balance between human safety and the movement productivity of the robots when there are both robots and human in the working environment. The anti-congestion potential field is to distinguish and prevent global congestion. The simulation results verify the validity of the proposed method by using the resultant potential of three kinds of potential field. Moreover, the experimental results on a real robot are presented and further indicate that the improved algorithm is more efficient than the traditional ones.
In this paper, three types of potential field are proposed to solve global congestion and human obstacle avoidance in the practical operation of multiple robots. The social potential field determines the interaction force among the robots and ensures their avoidance foundation. The behavior potential field aims to strike a balance between human safety and the movement productivity of the robots when there are both robots and human in the working environment. The anti-congestion potential field is to distinguish and prevent global congestion. The simulation results verify the validity of the proposed method by using the resultant potential of three kinds of potential field. Moreover, the experimental results on a real robot are presented and further indicate that the improved algorithm is more efficient than the traditional ones.
2018, 37(8): 1217-1222.
doi: 10.13433/j.cnki.1003-8728.20180015
Abstract:
The lightweight modular robot is mostly driven by harmonic reducer, and the stiffness of the reducer is relatively low and highly nonlinear. Therefore it is difficult to obtain joint stiffness parameters by linear identification, so a new calibration method is proposed in this paper to improve position accuracy of the robot. Firstly, the static stiffness error model of the robot is established by the stiffness characteristic curve of the harmonic reducer; Then comprehensive position error of the robot is measured using a laser tracker; Next, the error due to joint stiffness is estimated using the static stiffness error model and separated from the comprehensive error; Finally, the actual Denavit-Hartenberg parameters are identified using the least squares method, and the terminal error of the robot is estimated and compensated in real-time combining the stiffness error model. The experimental results show that this method can improve positioning accuracy of the robot effectively.
The lightweight modular robot is mostly driven by harmonic reducer, and the stiffness of the reducer is relatively low and highly nonlinear. Therefore it is difficult to obtain joint stiffness parameters by linear identification, so a new calibration method is proposed in this paper to improve position accuracy of the robot. Firstly, the static stiffness error model of the robot is established by the stiffness characteristic curve of the harmonic reducer; Then comprehensive position error of the robot is measured using a laser tracker; Next, the error due to joint stiffness is estimated using the static stiffness error model and separated from the comprehensive error; Finally, the actual Denavit-Hartenberg parameters are identified using the least squares method, and the terminal error of the robot is estimated and compensated in real-time combining the stiffness error model. The experimental results show that this method can improve positioning accuracy of the robot effectively.
2018, 37(8): 1223-1230.
doi: 10.13433/j.cnki.1003-8728.20180013
Abstract:
The model of wall sheath in an ion thruster with the magnetic field and secondary electrons sputtered by ion is established. The magnetic sheath structural characteristics with emission of secondary electrons were studied with the four-order Runge-Kutta method. The computing results show that the change in the size and angle of magnetic field has a significant influence on the wall sheath. The curves are smoother with secondary electrons. The calculation results on electrons are greatly influenced, while those on ions have little influence. In addition, the potential of wall sheath is the main cause for change in the thickness of wall sheath, which greatly influences the parameters of wall sheath.
The model of wall sheath in an ion thruster with the magnetic field and secondary electrons sputtered by ion is established. The magnetic sheath structural characteristics with emission of secondary electrons were studied with the four-order Runge-Kutta method. The computing results show that the change in the size and angle of magnetic field has a significant influence on the wall sheath. The curves are smoother with secondary electrons. The calculation results on electrons are greatly influenced, while those on ions have little influence. In addition, the potential of wall sheath is the main cause for change in the thickness of wall sheath, which greatly influences the parameters of wall sheath.
2018, 37(8): 1231-1238.
doi: 10.13433/j.cnki.1003-8728.20180005
Abstract:
To improve the radius error compensation accuracy of an on-machine measurement system, an accurate estimation algorithm is presented for the normal vector of a measurement point, which is an important parameter for radius error compensation. When the measurement point is in the vertices of triangular meshes, a normal vector estimation method is proposed based on the angle, centroids distance and perimeter of a triangle and is validated by the triangular mesh models of three quadric surfaces. The experimental results demonstrate that the improved algorithm can effectively improve the accuracy of normal vector estimation. Meanwhile, under the condition that the measurement points planned by the cross-section curve method are located in the interiors of the triangle, the barycenter coordinate method is proposed to compute the normal vectors of measurement points and verified by the density of two different grids with sine-like surfaces. The experimental results show that the improved algorithm decreases the average normal vector error by 53.5% and 61.7% respectively and obviously enhances the accuracy of normal vector estimation and radius error compensation.
To improve the radius error compensation accuracy of an on-machine measurement system, an accurate estimation algorithm is presented for the normal vector of a measurement point, which is an important parameter for radius error compensation. When the measurement point is in the vertices of triangular meshes, a normal vector estimation method is proposed based on the angle, centroids distance and perimeter of a triangle and is validated by the triangular mesh models of three quadric surfaces. The experimental results demonstrate that the improved algorithm can effectively improve the accuracy of normal vector estimation. Meanwhile, under the condition that the measurement points planned by the cross-section curve method are located in the interiors of the triangle, the barycenter coordinate method is proposed to compute the normal vectors of measurement points and verified by the density of two different grids with sine-like surfaces. The experimental results show that the improved algorithm decreases the average normal vector error by 53.5% and 61.7% respectively and obviously enhances the accuracy of normal vector estimation and radius error compensation.
2018, 37(8): 1239-1245.
doi: 10.13433/j.cnki.1003-8728.20180006
Abstract:
The relationship between the machine setting parameter errors and the surface errors of spiral bevel gears manufactured by duplex helical method are studied. Based on the gear meshing theory,the equations of deviation surfaces are established and the analytic expression of tooth surface error caused by machine setting parameters errors are derived by MATLAB. The deviation topographies corresponding to the machine setting parameter errors are built,the mapping relationship between the each process parameter error and the tooth surface errors is analyzed,the major impact machine setting parameters are obtained. The influence weight of the change in machine setting parameters on the tooth surface error is obtained by using second order surface. Based on the tooth flank error and error sensitivity matrixes,the model for adjusting tooth flank error is developed,the generalized inverse matrix with least square method is adopted to solve the transcendental equations,and the correction quantities is obtained. A spiral bevel gear generated by the duplex helical method is used as an example to validate the effectiveness of the error correction method,the results reveal that the tooth flank errors of both side are greatly reduced.
The relationship between the machine setting parameter errors and the surface errors of spiral bevel gears manufactured by duplex helical method are studied. Based on the gear meshing theory,the equations of deviation surfaces are established and the analytic expression of tooth surface error caused by machine setting parameters errors are derived by MATLAB. The deviation topographies corresponding to the machine setting parameter errors are built,the mapping relationship between the each process parameter error and the tooth surface errors is analyzed,the major impact machine setting parameters are obtained. The influence weight of the change in machine setting parameters on the tooth surface error is obtained by using second order surface. Based on the tooth flank error and error sensitivity matrixes,the model for adjusting tooth flank error is developed,the generalized inverse matrix with least square method is adopted to solve the transcendental equations,and the correction quantities is obtained. A spiral bevel gear generated by the duplex helical method is used as an example to validate the effectiveness of the error correction method,the results reveal that the tooth flank errors of both side are greatly reduced.
2018, 37(8): 1246-1252.
doi: 10.13433/j.cnki.1003-8728.20180004
Abstract:
Carbon fiber reinforced silicon carbide ceramic matrix composites(Cf/SiC) is a kind of widely used fiber reinforced ceramic matrix composite materials. In this paper, the ultrasonic vibration filing was brought up to solve the machining problem of Cf/SiC composites, the mathematical models were taken out to reveal the machining principle of ultrasonic vibration filing, and the feasibility experiment indicates that ultrasonic vibration filing is conducive to lower machining force and enhance surface quality comparing with traditional filing. The single-factor experiment was carried out to investigate the effect of the grain size, ultrasonic power, filing depth and feed speed on the machining force and surface quality. The results shows that machining force decreases with the increasing of ultrasonic power, and increases with the increasing of filing depth and feed speed, and coincides with the theoretical results; the increase in ultrasonic power enhances the surface quality, while the increase in filing depth and feed speed lowers the surface quality.
Carbon fiber reinforced silicon carbide ceramic matrix composites(Cf/SiC) is a kind of widely used fiber reinforced ceramic matrix composite materials. In this paper, the ultrasonic vibration filing was brought up to solve the machining problem of Cf/SiC composites, the mathematical models were taken out to reveal the machining principle of ultrasonic vibration filing, and the feasibility experiment indicates that ultrasonic vibration filing is conducive to lower machining force and enhance surface quality comparing with traditional filing. The single-factor experiment was carried out to investigate the effect of the grain size, ultrasonic power, filing depth and feed speed on the machining force and surface quality. The results shows that machining force decreases with the increasing of ultrasonic power, and increases with the increasing of filing depth and feed speed, and coincides with the theoretical results; the increase in ultrasonic power enhances the surface quality, while the increase in filing depth and feed speed lowers the surface quality.
2018, 37(8): 1253-1259.
doi: 10.13433/j.cnki.1003-8728.20180030
Abstract:
It is difficult to obtain an effective mathematical model for cutting mechanism by using theoretical analysis. This paper introduces the experimental method of central composite design (CCD), and establishes the experimental scheme of four factors and three levels for single-crystal Silicon wire cutting. The second order mathematical model for single-crystal Silicon surface roughness and material removal rate, such as no-load voltage, pulse width, pulse interval and wire speed, was established by using response surface methodology (RSM). The results show that the prediction model has good fittness and adaptability. Non-dominated sorting genetic algorithm Ⅱ (NSGA-Ⅱ) is used to solve the optimization problem, and the optimal Pareto solution set is obtained. The optimization of the process parameters is carried out to improve the processing quality and material removal rate of the surface of single-crystal Silicon. Experiments show that the present model is accurate for predicting the surface roughness and material removal rate, and which can realize the prediction of roughness and material removal rate during the wire cutting of the corresponding semiconductor materials.
It is difficult to obtain an effective mathematical model for cutting mechanism by using theoretical analysis. This paper introduces the experimental method of central composite design (CCD), and establishes the experimental scheme of four factors and three levels for single-crystal Silicon wire cutting. The second order mathematical model for single-crystal Silicon surface roughness and material removal rate, such as no-load voltage, pulse width, pulse interval and wire speed, was established by using response surface methodology (RSM). The results show that the prediction model has good fittness and adaptability. Non-dominated sorting genetic algorithm Ⅱ (NSGA-Ⅱ) is used to solve the optimization problem, and the optimal Pareto solution set is obtained. The optimization of the process parameters is carried out to improve the processing quality and material removal rate of the surface of single-crystal Silicon. Experiments show that the present model is accurate for predicting the surface roughness and material removal rate, and which can realize the prediction of roughness and material removal rate during the wire cutting of the corresponding semiconductor materials.
2018, 37(8): 1260-1266.
doi: 10.13433/j.cnki.1003-8728.20180019
Abstract:
SKD11 steel is a kind of special and difficult-to-cut materials used as key part of a military missile rack, which service surface needs to meet mirror roughness. Traditional grinding and polishing method is time-consuming and laborious due to the high hardness of SKD11 after quenching. For achieving high material removal rate to the workpiece surface, polishing tests on curved workpiece using elastic abrasive were carried out. The polishing model for curved surface polishing by elastic abrasive was established. The effects of the process parameters on the material removal rate(MRR) and abrasive wear were analyzed. A multi-index optimization based on MRR, abrasive wear and surface roughness(Ra) was realized by grey relation analysis and Taguchi method. The results showed that the setting cut depth and grinding speed are the main influencing factors of MRR and abrasive wear. To guarantee the life of the abrasive tool, the setting cut depth should be less than 0.3 mm and the grinding speed is below 9 000 r/min in polishing by elastic abrasive. The optimal parameter combination is the abrasive of #320, grinding speed of 3 000 r/min, setting cut depth of 0.3 mm and feed rate of 2 mm/min. The mean Ra of the workpiece achieves 0.056 μm and MRR increases 2.6 times with an improvement of abrasive wear under the optimized parameters.
SKD11 steel is a kind of special and difficult-to-cut materials used as key part of a military missile rack, which service surface needs to meet mirror roughness. Traditional grinding and polishing method is time-consuming and laborious due to the high hardness of SKD11 after quenching. For achieving high material removal rate to the workpiece surface, polishing tests on curved workpiece using elastic abrasive were carried out. The polishing model for curved surface polishing by elastic abrasive was established. The effects of the process parameters on the material removal rate(MRR) and abrasive wear were analyzed. A multi-index optimization based on MRR, abrasive wear and surface roughness(Ra) was realized by grey relation analysis and Taguchi method. The results showed that the setting cut depth and grinding speed are the main influencing factors of MRR and abrasive wear. To guarantee the life of the abrasive tool, the setting cut depth should be less than 0.3 mm and the grinding speed is below 9 000 r/min in polishing by elastic abrasive. The optimal parameter combination is the abrasive of #320, grinding speed of 3 000 r/min, setting cut depth of 0.3 mm and feed rate of 2 mm/min. The mean Ra of the workpiece achieves 0.056 μm and MRR increases 2.6 times with an improvement of abrasive wear under the optimized parameters.
2018, 37(8): 1267-1271.
doi: 10.13433/j.cnki.1003-8728.20180113
Abstract:
According to the structural features and dynamics characteristics of light-weight large flexible space cable-net antenna, a new modal testing technique is proposed in this study. A non-contact pneumatic excitation system is designed and applied to excite vibration, which is suitable for cable-net structure. The 3D scanning laser Doppler vibrometer (3D SLDV) is used to conduct non-contact vibration measurement. The structural modal parameters of cable-net antenna are identified based on the time domain modal analysis method of random decrement technique (RDT) combined with Ibrahim time domain method (ITD). As an extension to conventional modal test methods, the current technique has successfully obtained the vibration modes of a light-weight large flexible cable-net structure, showing a promising prospect of applications.
According to the structural features and dynamics characteristics of light-weight large flexible space cable-net antenna, a new modal testing technique is proposed in this study. A non-contact pneumatic excitation system is designed and applied to excite vibration, which is suitable for cable-net structure. The 3D scanning laser Doppler vibrometer (3D SLDV) is used to conduct non-contact vibration measurement. The structural modal parameters of cable-net antenna are identified based on the time domain modal analysis method of random decrement technique (RDT) combined with Ibrahim time domain method (ITD). As an extension to conventional modal test methods, the current technique has successfully obtained the vibration modes of a light-weight large flexible cable-net structure, showing a promising prospect of applications.
2018, 37(8): 1272-1279.
doi: 10.13433/j.cnki.1003-8728.20180033
Abstract:
In this paper, a theoretical analysis of the accelerated pressure drop and the frictional pressure drop of the Venturi divergent section was carried out. Based on the long throat Venturi with a diameter of 50 mm and beta ratio of 0.55, 4 kinds of structures were designed from the divergent angle and the shape of divergent section by numerical simulation method of computational fluid dynamics (CFD). Finding the optimal structure used in wet-gas flow can improve the linear identification of up and down differential pressure ratio K with liquid volume fraction (LVF). Simulation data coincide with theoretical analysis results. The results showed that the value of K rises with the increase of the divergent angle, but it is difficult to realize the linear identification. The elliptical arc divergent section can improve resolving power of K to liquid phase by decreasing the accelerated pressure drop and increasing the friction pressure drop. It is necessary to ensure the smooth connection between the divergent section and straight pipe section, so as to ensure the stability of the flow pattern. The divergent section of the elliptic arc structure connects with linear structure smoothly ensuring the stability of wet-gas flow, meanwhile the linearity between K and LVF is broadened from the original 1.5% to 4.5%.
In this paper, a theoretical analysis of the accelerated pressure drop and the frictional pressure drop of the Venturi divergent section was carried out. Based on the long throat Venturi with a diameter of 50 mm and beta ratio of 0.55, 4 kinds of structures were designed from the divergent angle and the shape of divergent section by numerical simulation method of computational fluid dynamics (CFD). Finding the optimal structure used in wet-gas flow can improve the linear identification of up and down differential pressure ratio K with liquid volume fraction (LVF). Simulation data coincide with theoretical analysis results. The results showed that the value of K rises with the increase of the divergent angle, but it is difficult to realize the linear identification. The elliptical arc divergent section can improve resolving power of K to liquid phase by decreasing the accelerated pressure drop and increasing the friction pressure drop. It is necessary to ensure the smooth connection between the divergent section and straight pipe section, so as to ensure the stability of the flow pattern. The divergent section of the elliptic arc structure connects with linear structure smoothly ensuring the stability of wet-gas flow, meanwhile the linearity between K and LVF is broadened from the original 1.5% to 4.5%.
2018, 37(8): 1280-1285.
doi: 10.13433/j.cnki.1003-8728.20180008
Abstract:
In order to predict the engine intake noise accurately, transient analysis is used in aero-acoustics calculations of intake manifold flow, and the acoustics field distribution is simulated in acoustics software. Establish a one-dimensional engine model which is calibrated by experimental data to output reliable pressure and velocity results for flow field calculation. Two turbulence models, the large eddy simulation (LES) and detached eddy simulation (DES) methods are used separately to simulate the flow field in the manifold accurately. The aerodynamics noise is calculated by acoustic FEM method using surface pressure distribution. Comparisons between two algorithms indicate that DES can get results of similar accuracy with LES while DES using less time. The results are compared with NVH test data and the accuracy of simulation method is verified. The spectrum analysis between simulation results and pressure boundary in frequency domain make the design of vacuum filter and intake manifold more specific.
In order to predict the engine intake noise accurately, transient analysis is used in aero-acoustics calculations of intake manifold flow, and the acoustics field distribution is simulated in acoustics software. Establish a one-dimensional engine model which is calibrated by experimental data to output reliable pressure and velocity results for flow field calculation. Two turbulence models, the large eddy simulation (LES) and detached eddy simulation (DES) methods are used separately to simulate the flow field in the manifold accurately. The aerodynamics noise is calculated by acoustic FEM method using surface pressure distribution. Comparisons between two algorithms indicate that DES can get results of similar accuracy with LES while DES using less time. The results are compared with NVH test data and the accuracy of simulation method is verified. The spectrum analysis between simulation results and pressure boundary in frequency domain make the design of vacuum filter and intake manifold more specific.
2018, 37(8): 1286-1292.
doi: 10.13433/j.cnki.1003-8728.20180011
Abstract:
The operating sounds radiated from internal combustion engine include tonal noise components caused by rotating mechanical parts such as the gears, fan and so on. The negative effects of tonal noise components need to be considered for the quantitative evaluation of users' subjective preference. However, it is found that the correlation between Aure's tonality and subjective preference is too low to fully reflect the influence of tonal characteristics on subjective feelings. In this paper, the calculation model of Aure's tonality is analyzed in detail to find the cause of decreasing correlation. Based on the tone-to-noise ratio, which can better express the energy ratio of tonal components in noise and has a higher correlation with the subjective feelings, an improved tonality evaluation model is proposed. As a result, it has been confirmed that the proposed tonality evaluation model has sufficient correlation and improves the accuracy of the tonality model in the research on sound quality of internal combustion engine.
The operating sounds radiated from internal combustion engine include tonal noise components caused by rotating mechanical parts such as the gears, fan and so on. The negative effects of tonal noise components need to be considered for the quantitative evaluation of users' subjective preference. However, it is found that the correlation between Aure's tonality and subjective preference is too low to fully reflect the influence of tonal characteristics on subjective feelings. In this paper, the calculation model of Aure's tonality is analyzed in detail to find the cause of decreasing correlation. Based on the tone-to-noise ratio, which can better express the energy ratio of tonal components in noise and has a higher correlation with the subjective feelings, an improved tonality evaluation model is proposed. As a result, it has been confirmed that the proposed tonality evaluation model has sufficient correlation and improves the accuracy of the tonality model in the research on sound quality of internal combustion engine.
2018, 37(8): 1293-1298.
doi: 10.13433/j.cnki.1003-8728.20180010
Abstract:
In order to improve bolt axial force of automotive aluminum alloys wheel to ensure safety and reliability of bolt connection, mechanical analysis model for wheel cone connection in the tightening process was established to study influencing factors of bolt structural design on axial force improvement and analyze elastic-plastic state of wheel cone hole. Axial force distribution of coupling threads and relationship between bolt axial force and tightening torque were analyzed via Abaqus, improving methods and measurement of axial force were proposed. Simulation results show to reduce nut cone friction force, increasing nut cone angle, tightening torque and changing nut cone structure can improve bolt axial force, improving degree of bolt axial force is influenced by the loading capacity of wheel and coupling threads. Theoretical analysis results are verified by bolt connection experiment.
In order to improve bolt axial force of automotive aluminum alloys wheel to ensure safety and reliability of bolt connection, mechanical analysis model for wheel cone connection in the tightening process was established to study influencing factors of bolt structural design on axial force improvement and analyze elastic-plastic state of wheel cone hole. Axial force distribution of coupling threads and relationship between bolt axial force and tightening torque were analyzed via Abaqus, improving methods and measurement of axial force were proposed. Simulation results show to reduce nut cone friction force, increasing nut cone angle, tightening torque and changing nut cone structure can improve bolt axial force, improving degree of bolt axial force is influenced by the loading capacity of wheel and coupling threads. Theoretical analysis results are verified by bolt connection experiment.
2018, 37(8): 1299-1305.
doi: 10.13433/j.cnki.1003-8728.20180035
Abstract:
Shape memory alloy is widely used due to shape memory effect and other excellent properties. In this paper, the shape memory alloy ring is assembled to the electric power fittings. The mechanical properties of the common material with shape memory alloy ring were obtained comparing with the common material. Through the tensile curve of the linear trend analysis, the shape memory alloy ring of defective hardware repair and improvement demonstrate to enhance the mechanical properties of common materials and reduce the material deformation.
Shape memory alloy is widely used due to shape memory effect and other excellent properties. In this paper, the shape memory alloy ring is assembled to the electric power fittings. The mechanical properties of the common material with shape memory alloy ring were obtained comparing with the common material. Through the tensile curve of the linear trend analysis, the shape memory alloy ring of defective hardware repair and improvement demonstrate to enhance the mechanical properties of common materials and reduce the material deformation.
2018, 37(8): 1306-1312.
doi: 10.13433/j.cnki.1003-8728.20180107
Abstract:
The data sharing of aircraft engines is a system engineering, which contains the aspects of policy guarantee, databases and platform support etc. This paper analyzes the data resources at two components level (compressor and turbine), one property level (strength and life) and one process level (engine maintenance), defines the basic format of aircraft engines data, develops the architecture of sharing platform, distinguish the interest subjects and interest demands of the data sharing.
The data sharing of aircraft engines is a system engineering, which contains the aspects of policy guarantee, databases and platform support etc. This paper analyzes the data resources at two components level (compressor and turbine), one property level (strength and life) and one process level (engine maintenance), defines the basic format of aircraft engines data, develops the architecture of sharing platform, distinguish the interest subjects and interest demands of the data sharing.
