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RSS2022 Vol. 41, No. 11
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2022, 41(11): 1641-1649.
doi: 10.13433/j.cnki.1003-8728.20200502
PDF 3286KB
Abstract:
The SIMP method has become an efficient method to solve the topology optimization issue of the continuum because of its advantages such as less design constraints and high performance. In the traditional SIMP method, numerical instability often occurs during the optimization process, and the optimization results often have gray units, which make it difficult to extract the optimization model and have not good manufacturability. Although the Sigmund sensitivity filtering method can effectively improve the checkerboard phenomenon, this method is prone to the problem of boundary diffusion. In order to achieve the topological optimization results with clear boundaries, a partition density correction sensitivity filtering method for continuum structure is proposed in this study. This method divides the original filtering area, uses a new mixed convolution index to process different areas, and further adopts a method with preset density correction weights that effectively weakens the problem of boundary diffusion. By combining and analyzing multiple analytical examples and different filtering methods, the feasibility and reliability of the method are verified.
The SIMP method has become an efficient method to solve the topology optimization issue of the continuum because of its advantages such as less design constraints and high performance. In the traditional SIMP method, numerical instability often occurs during the optimization process, and the optimization results often have gray units, which make it difficult to extract the optimization model and have not good manufacturability. Although the Sigmund sensitivity filtering method can effectively improve the checkerboard phenomenon, this method is prone to the problem of boundary diffusion. In order to achieve the topological optimization results with clear boundaries, a partition density correction sensitivity filtering method for continuum structure is proposed in this study. This method divides the original filtering area, uses a new mixed convolution index to process different areas, and further adopts a method with preset density correction weights that effectively weakens the problem of boundary diffusion. By combining and analyzing multiple analytical examples and different filtering methods, the feasibility and reliability of the method are verified.
2022, 41(11): 1650-1657.
doi: 10.13433/j.cnki.1003-8728.20200531
Abstract:
As the output of the working characteristics of the cutting system, the dynamic behavior of the tool tip point shows strong nonlinearity and differentiation characteristics, which directly affect the machining quality and production efficiency of workpieces. At this stage, the research on the dynamic characteristics of tool tip points based on theoretical or experimental methods has limitations such as complex modeling or high testing costs. To this end, based on the theoretical basis of the semi-theoretical method of solving the inverse stability, and fully considering the double flexibility of the tool tip point and the workpiece in the cutting system, a method for distinguishing the dynamic behavior of the tool tip point is proposed. This method transforms the identification of the differential characteristics of the dynamic behavior of the tool tip under different operating conditions into a kind of optimization design problem, that is, the dynamic parameters of the tool tip under different operating conditions are used as variables. An optimization model was established to minimize the comprehensive deviation of the ultimate cutting depth and chatter frequency obtained from theoretical prediction and experimental calibration, so as to reveal the differentiation characteristics and evolution law of the dynamic behavior of the tool tip. Through the implementation of variable cutting depth milling experiments, the results obtained are verified. The comparative analysis shows that the proposed method can obtain the differentiation characteristics of the dynamic behavior of the tool tip point more accurately, which is conducive to the accurate prediction of the cutting stability under the operation state.
As the output of the working characteristics of the cutting system, the dynamic behavior of the tool tip point shows strong nonlinearity and differentiation characteristics, which directly affect the machining quality and production efficiency of workpieces. At this stage, the research on the dynamic characteristics of tool tip points based on theoretical or experimental methods has limitations such as complex modeling or high testing costs. To this end, based on the theoretical basis of the semi-theoretical method of solving the inverse stability, and fully considering the double flexibility of the tool tip point and the workpiece in the cutting system, a method for distinguishing the dynamic behavior of the tool tip point is proposed. This method transforms the identification of the differential characteristics of the dynamic behavior of the tool tip under different operating conditions into a kind of optimization design problem, that is, the dynamic parameters of the tool tip under different operating conditions are used as variables. An optimization model was established to minimize the comprehensive deviation of the ultimate cutting depth and chatter frequency obtained from theoretical prediction and experimental calibration, so as to reveal the differentiation characteristics and evolution law of the dynamic behavior of the tool tip. Through the implementation of variable cutting depth milling experiments, the results obtained are verified. The comparative analysis shows that the proposed method can obtain the differentiation characteristics of the dynamic behavior of the tool tip point more accurately, which is conducive to the accurate prediction of the cutting stability under the operation state.
2022, 41(11): 1658-1664.
doi: 10.13433/j.cnki.1003-8728.20200556
Abstract:
In order to solve the problems of complex structure and limited use scene of high-torque magnetorheological fluid (MRF) device, this paper proposes a method of multi-disc MRF transmission through electromagnetic extrusion. The method uses the electromagnetic force generated after the excitation coil is electrified to squeeze the MRF, so that the structure of the MRF device is simpler and more compact while transmitting high torque. The Maxwell software and ABAQUS software were used to analyze the magnetic field and structural field of the MRF device. Shear yield stress, electromagnetic force and extrusion stress of MRF in each working gap under different input current were calculated; shear yield stress of MRF after extrusion was analyzed, and the torque transmitted by the MRF device was calculated. The comparison of experimental results shows that the transmission performance of the MRF device is significantly enhanced with electromagnetic extrusion. When 3 A input current and 7 241.4 N electromagnetic force are applied, the transmission torque of the MRF device increases by 78.6% compared with the non-extrusion state.
In order to solve the problems of complex structure and limited use scene of high-torque magnetorheological fluid (MRF) device, this paper proposes a method of multi-disc MRF transmission through electromagnetic extrusion. The method uses the electromagnetic force generated after the excitation coil is electrified to squeeze the MRF, so that the structure of the MRF device is simpler and more compact while transmitting high torque. The Maxwell software and ABAQUS software were used to analyze the magnetic field and structural field of the MRF device. Shear yield stress, electromagnetic force and extrusion stress of MRF in each working gap under different input current were calculated; shear yield stress of MRF after extrusion was analyzed, and the torque transmitted by the MRF device was calculated. The comparison of experimental results shows that the transmission performance of the MRF device is significantly enhanced with electromagnetic extrusion. When 3 A input current and 7 241.4 N electromagnetic force are applied, the transmission torque of the MRF device increases by 78.6% compared with the non-extrusion state.
2022, 41(11): 1665-1670.
doi: 10.13433/j.cnki.1003-8728.20220241
Abstract:
Structural cross-scale topology optimization can realize collaborative design of microstructure and macrostructure, based on which a quantitative model for the enrollment quality assessment is proposed. The main works of the study include: establish the quantification microstructure mapping individual enrollment performance, enrollment category and category loyalty to microstructure volume fraction, feature correlation and performance reduction; construct surrogate model for the equivalent elastic matrix based on artificial neural network and multiscale finite element method (MFEM); construct the cross-scale topology optimization model to evaluate the enrollment quality. Base on the proposed method, the enrollment quality of a certain category of Northwestern Polytechnical University in the past three years is evaluated, which guides the optimization of the college enrollment policy.
Structural cross-scale topology optimization can realize collaborative design of microstructure and macrostructure, based on which a quantitative model for the enrollment quality assessment is proposed. The main works of the study include: establish the quantification microstructure mapping individual enrollment performance, enrollment category and category loyalty to microstructure volume fraction, feature correlation and performance reduction; construct surrogate model for the equivalent elastic matrix based on artificial neural network and multiscale finite element method (MFEM); construct the cross-scale topology optimization model to evaluate the enrollment quality. Base on the proposed method, the enrollment quality of a certain category of Northwestern Polytechnical University in the past three years is evaluated, which guides the optimization of the college enrollment policy.
2022, 41(11): 1671-1678.
doi: 10.13433/j.cnki.1003-8728.20200554
Abstract:
To investigate the influence of roughness on the scatter in the propagation of subsurface crack for frictionless contact of rough surfaces, random topography samples with different statistical distributions were first obtained with the FFT simulation method. The contact pressure distributions of the simulated topography samples were then determined through the elastic contactcalculation. With the calculated pressure distributions as input, the propagation paths and propagation lives of subsurface crack were calculated for different curvature radii and loads. The results show that: 1) the crack propagation paths and propagation lives have great dispersity under the same roughness statistical distribution, and the dispersity correlates with the standard deviation of roughness, curvature radius and load; 2) the effect of the curvature radius on the crack propagation life is so great that the variations of the crack propagation life vary greatly for different curvature radii; 3) the correlation length of roughness has slight effect on the crack propagation, and no significant correlation between them is found.
To investigate the influence of roughness on the scatter in the propagation of subsurface crack for frictionless contact of rough surfaces, random topography samples with different statistical distributions were first obtained with the FFT simulation method. The contact pressure distributions of the simulated topography samples were then determined through the elastic contactcalculation. With the calculated pressure distributions as input, the propagation paths and propagation lives of subsurface crack were calculated for different curvature radii and loads. The results show that: 1) the crack propagation paths and propagation lives have great dispersity under the same roughness statistical distribution, and the dispersity correlates with the standard deviation of roughness, curvature radius and load; 2) the effect of the curvature radius on the crack propagation life is so great that the variations of the crack propagation life vary greatly for different curvature radii; 3) the correlation length of roughness has slight effect on the crack propagation, and no significant correlation between them is found.
2022, 41(11): 1679-1685.
doi: 10.13433/j.cnki.1003-8728.20200537
Abstract:
In the process of convective heat transfer, how to increase the boundary disturbance to improve the heat transfer performance is the key issue to realize the enhancement of heat transfer. Based on the pulsation effect of the self-excited oscillation chamber and the high thermal conductivity of the nanofluid, a passive pulsation enhanced heat transfer mechanism of the nanofluid is proposed in this study. The orthogonal numerical experiment method was used to optimize the main structural parameters of the self-excited oscillation hot runner. The large eddy simulation turbulence model was used to analyze the influence of the hot runner structural parameters on the heat transfer characteristics of the Al2O3 nanofluid, and the optimal structural parameter ratio was obtained. The orthogonal numerical experiment results show that the length of the chamber has the greatest effect on the heat transfer performance of the nanofluid in the hot runner, and the diameter of the chamber has the least effect. It is also observed that the self-excited oscillating hot runner has the best heat transfer performance when dimensionless parameters L/d1=7, D/d1=11 and d2/d0=1.1.
In the process of convective heat transfer, how to increase the boundary disturbance to improve the heat transfer performance is the key issue to realize the enhancement of heat transfer. Based on the pulsation effect of the self-excited oscillation chamber and the high thermal conductivity of the nanofluid, a passive pulsation enhanced heat transfer mechanism of the nanofluid is proposed in this study. The orthogonal numerical experiment method was used to optimize the main structural parameters of the self-excited oscillation hot runner. The large eddy simulation turbulence model was used to analyze the influence of the hot runner structural parameters on the heat transfer characteristics of the Al2O3 nanofluid, and the optimal structural parameter ratio was obtained. The orthogonal numerical experiment results show that the length of the chamber has the greatest effect on the heat transfer performance of the nanofluid in the hot runner, and the diameter of the chamber has the least effect. It is also observed that the self-excited oscillating hot runner has the best heat transfer performance when dimensionless parameters L/d1=7, D/d1=11 and d2/d0=1.1.
2022, 41(11): 1686-1692.
doi: 10.13433/j.cnki.1003-8728.20220209
Abstract:
A four-component model was used to characterize the dynamic characteristics of rubber viscoelastic vibration isolation system, and the dimensionless differential equation of the system was solved by harmonic balance method. The influence of parameters on the amplitude-frequency characteristics and force transmissibility of the system was analyzed, and the calculation method of the optimal damping coefficient under single frequency excitation and multiple frequency excitation was derived. The results show that increasing the damping coefficient or stiffness ratio will shift the system′s resonance peak to the high frequency direction, and also broaden the effective vibration isolation range in the low frequency region. The reasonable design of the stiffness ratio can make the resonance peak of the system far away from the main frequency of the vibration isolation system, and under the condition of not reducing the static deflection of the system, the resonance frequency of the system can be fine-tuned in a small range by adjusting the damping coefficient. When the stiffness ratio is determined, the amplitude-frequency response curves and force transfer curves have a common point under different damping coefficients. Based on this characteristic, the optimal damping coefficient under given parameters can be calculated, which minimizes the resonance peak and optimizes the vibration isolation performance of the system. The method can also be used to calculate the optimal damping coefficient of the system under multi-frequency excitation.
A four-component model was used to characterize the dynamic characteristics of rubber viscoelastic vibration isolation system, and the dimensionless differential equation of the system was solved by harmonic balance method. The influence of parameters on the amplitude-frequency characteristics and force transmissibility of the system was analyzed, and the calculation method of the optimal damping coefficient under single frequency excitation and multiple frequency excitation was derived. The results show that increasing the damping coefficient or stiffness ratio will shift the system′s resonance peak to the high frequency direction, and also broaden the effective vibration isolation range in the low frequency region. The reasonable design of the stiffness ratio can make the resonance peak of the system far away from the main frequency of the vibration isolation system, and under the condition of not reducing the static deflection of the system, the resonance frequency of the system can be fine-tuned in a small range by adjusting the damping coefficient. When the stiffness ratio is determined, the amplitude-frequency response curves and force transfer curves have a common point under different damping coefficients. Based on this characteristic, the optimal damping coefficient under given parameters can be calculated, which minimizes the resonance peak and optimizes the vibration isolation performance of the system. The method can also be used to calculate the optimal damping coefficient of the system under multi-frequency excitation.
2022, 41(11): 1693-1697.
doi: 10.13433/j.cnki.1003-8728.20200555
Abstract:
The dynamics characteristics of rotor system with parallel misalignment are investigated when flexible of coupling is also considered. Radial displacement, bending and torsion of rotor are included in the model, and bearing are assumed anisotropic. Firstly, dynamic governing equations of rotor system with parallel misalignment are established with the Lagrange equation. Then, Runge-Kutta numerical integration method is used to solve the nonlinear governing equations; and responses in time and frequency domain and orbit of rotor system with different parameters are obtained and discussed. Finally, the effect of the magnitude of parallel misalignment on vibration responses is analyzed, when the ratio of the misalignment to the rotor length is less than 10−3, some results are obtained as follows: the transverse vibration is always dominated by the fundamental frequency component; the torsional vibration has considerable amount of double frequency components; furthermore, the coupling of lateral and torsional vibrations is very weak and does not show obvious nonlinear characteristics.
The dynamics characteristics of rotor system with parallel misalignment are investigated when flexible of coupling is also considered. Radial displacement, bending and torsion of rotor are included in the model, and bearing are assumed anisotropic. Firstly, dynamic governing equations of rotor system with parallel misalignment are established with the Lagrange equation. Then, Runge-Kutta numerical integration method is used to solve the nonlinear governing equations; and responses in time and frequency domain and orbit of rotor system with different parameters are obtained and discussed. Finally, the effect of the magnitude of parallel misalignment on vibration responses is analyzed, when the ratio of the misalignment to the rotor length is less than 10−3, some results are obtained as follows: the transverse vibration is always dominated by the fundamental frequency component; the torsional vibration has considerable amount of double frequency components; furthermore, the coupling of lateral and torsional vibrations is very weak and does not show obvious nonlinear characteristics.
2022, 41(11): 1698-1704.
doi: 10.13433/j.cnki.1003-8728.20200522
Abstract:
To solve the problem that the traditional throttling regulation of fluid machinery is easy to waste a lot of electric energy, a disc type permanent magnet eddy current coupling with the function of power transmission and speed regulation is designed. The equivalent magnetic circuit of the coupling is established, the calculation model of torque and eddy current loss of the coupling is constructed, the influence of magnetic flux leakage on magnetic induction is analyzed. Furthermore, the influence of slip, air gap and thickness of permanent magnet on transmission characteristics is discussed. The results show that, after considering magnetic flux leakage, the calculation result on the magnetic induction intensity of air gap magnetic field is smaller than that of neglecting this factor and that the deviation between them increases with the increase of air gap. With the increase of slip, the transmission torque of the coupling first increases rapidly and then decreases slowly. The transmission torque increases with the increase of permanent magnet thickness and decreases with the increase of air gap size, thus guiding the design of disc permanent magnet eddy current coupling.
To solve the problem that the traditional throttling regulation of fluid machinery is easy to waste a lot of electric energy, a disc type permanent magnet eddy current coupling with the function of power transmission and speed regulation is designed. The equivalent magnetic circuit of the coupling is established, the calculation model of torque and eddy current loss of the coupling is constructed, the influence of magnetic flux leakage on magnetic induction is analyzed. Furthermore, the influence of slip, air gap and thickness of permanent magnet on transmission characteristics is discussed. The results show that, after considering magnetic flux leakage, the calculation result on the magnetic induction intensity of air gap magnetic field is smaller than that of neglecting this factor and that the deviation between them increases with the increase of air gap. With the increase of slip, the transmission torque of the coupling first increases rapidly and then decreases slowly. The transmission torque increases with the increase of permanent magnet thickness and decreases with the increase of air gap size, thus guiding the design of disc permanent magnet eddy current coupling.
2022, 41(11): 1705-1712.
doi: 10.13433/j.cnki.1003-8728.20200510
Abstract:
In response to the difficulty in ensuring uniformity of coating thickness in the boundary area of face sheets when the sparying robot automatically coats a large surface with an air spraying gun, the causes of coating thickness deviation were firstly analyzed, and then a spraying gun model with the description of coating thickness distribution at the start and end positions of spraying was established by fitting the experimental data of the flat plate at a uniform straight line. On the basis of the present model, the transverse lap parameters of the boundary area of the face sheet were analyzed and optimal value interval solving,and the optimal value interval is 0.2 - 0.4 was obtained. Finally, the present processing parameter is proved to be accurate and can effectively improve the coating thickness uniformity in the boundary area of the face sheet through multiple comparison tests.
In response to the difficulty in ensuring uniformity of coating thickness in the boundary area of face sheets when the sparying robot automatically coats a large surface with an air spraying gun, the causes of coating thickness deviation were firstly analyzed, and then a spraying gun model with the description of coating thickness distribution at the start and end positions of spraying was established by fitting the experimental data of the flat plate at a uniform straight line. On the basis of the present model, the transverse lap parameters of the boundary area of the face sheet were analyzed and optimal value interval solving,and the optimal value interval is 0.2 - 0.4 was obtained. Finally, the present processing parameter is proved to be accurate and can effectively improve the coating thickness uniformity in the boundary area of the face sheet through multiple comparison tests.
2022, 41(11): 1713-1718.
doi: 10.13433/j.cnki.1003-8728.20200496
Abstract:
In order to improve the efficiency of creating three-dimensional model for modified tapered roller bearing, a parametric modeling method based on ADAMS secondary development is proposed. The difficulty of constructing the model for the modified roller is reduced by dividing the modified tapered roller into several parts, and wrote modeling macro commands in ADAMS/VIEW to create three-dimensional model for modified tapered roller bearing, which greatly shorten the modeling time. In addition, through case analysis, the 3D bearing model created by the present method and Creowas importedinto ABAQUS respectively, and the roller-raceway contact stress with those models under different working conditionswere analyzed. The results show that the average relative error between the contact stress distribution curves of two kinds models is below 1.8%, the accuracy with the present methodwas verified.
In order to improve the efficiency of creating three-dimensional model for modified tapered roller bearing, a parametric modeling method based on ADAMS secondary development is proposed. The difficulty of constructing the model for the modified roller is reduced by dividing the modified tapered roller into several parts, and wrote modeling macro commands in ADAMS/VIEW to create three-dimensional model for modified tapered roller bearing, which greatly shorten the modeling time. In addition, through case analysis, the 3D bearing model created by the present method and Creowas importedinto ABAQUS respectively, and the roller-raceway contact stress with those models under different working conditionswere analyzed. The results show that the average relative error between the contact stress distribution curves of two kinds models is below 1.8%, the accuracy with the present methodwas verified.
2022, 41(11): 1719-1726.
doi: 10.13433/j.cnki.1003-8728.20200463
Abstract:
In order to improve the conflict problem of different index optimization in aluminum alloy machining effectively, a new multi-objective optimization method has been proposed in this paper. Firstly, grey relations analysis (GRA) has been applied to convert the multi-objective problems of cutting force, surface roughness and material removal rate in the machining into single-objective problem of grey relational grade (GRG). Then, a correlation model between the cutting parameters and GRG has been constructedvia support vector machine (SVM). Finally, the chaos particle swarm optimization (CPSO) has been applied to find the optimal processing parameters for minimizing cutting force and surface roughness and maximizing material removal rate at a cutting speed of 400 m/min, feed rate of 0.15 mm/r and cutting depth of 1 mm in the turning of aluminum alloy and it turns out that the CPSO algorithm has better global search capabilities,can converge to the global optimal position faster and obtain better optimization results comparing with particle swarm optimization (PSO) algorithm.
In order to improve the conflict problem of different index optimization in aluminum alloy machining effectively, a new multi-objective optimization method has been proposed in this paper. Firstly, grey relations analysis (GRA) has been applied to convert the multi-objective problems of cutting force, surface roughness and material removal rate in the machining into single-objective problem of grey relational grade (GRG). Then, a correlation model between the cutting parameters and GRG has been constructedvia support vector machine (SVM). Finally, the chaos particle swarm optimization (CPSO) has been applied to find the optimal processing parameters for minimizing cutting force and surface roughness and maximizing material removal rate at a cutting speed of 400 m/min, feed rate of 0.15 mm/r and cutting depth of 1 mm in the turning of aluminum alloy and it turns out that the CPSO algorithm has better global search capabilities,can converge to the global optimal position faster and obtain better optimization results comparing with particle swarm optimization (PSO) algorithm.
2022, 41(11): 1727-1732.
doi: 10.13433/j.cnki.1003-8728.20200528
Abstract:
In view of the defects such as frequent acceleration and deceleration and complex curve processing algorithm, a simple implement method based on segmental curve is proposed. The method of processing and speed control of curve micro-segment is analyzed, and the idea of segmental machining is given. Based on the principle of "discrete curvature", the piecewise algorithm is deduced, and the curve processing speed is planned and designed by combining the direct transition and circular transition methods, and the realization flow of the algorithm and the key points of prospective machining are given. Finally, the plane curve is piecewise machined with this method. The experimental results show that this method is simple in calculation, high in efficiency, less in acceleration and deceleration than other methods, and smooth in processing.
In view of the defects such as frequent acceleration and deceleration and complex curve processing algorithm, a simple implement method based on segmental curve is proposed. The method of processing and speed control of curve micro-segment is analyzed, and the idea of segmental machining is given. Based on the principle of "discrete curvature", the piecewise algorithm is deduced, and the curve processing speed is planned and designed by combining the direct transition and circular transition methods, and the realization flow of the algorithm and the key points of prospective machining are given. Finally, the plane curve is piecewise machined with this method. The experimental results show that this method is simple in calculation, high in efficiency, less in acceleration and deceleration than other methods, and smooth in processing.
2022, 41(11): 1733-1745.
doi: 10.13433/j.cnki.1003-8728.20200545
Abstract:
In order to solve the problem of poorly considering a system′s hierarchical structure in the current product conceptual design plan and the lack of interrelationship between multiple attributes, a multi-attribute decision-making method for product concept design based on concept hierarchy development (CHD) was proposed. Based on the CHD theory, the method divides the image of each candidate product′s conceptual design plan into three design levels: module component, angle view, and physical attribute.The similarity comparison matrix betweenmulti-attribute criteria at each level of development was constructed. The method of combining the Pythagorean fuzzy set (PFS) and theprospect theory (PT) was used to obtain the weight distribution of decision experts and attribute criteria and realize the objective and reasonable multi-attribute decision-making for product conceptual design. Finally, the feasibility and effectiveness of the method was verified by taking product conceptual design schemes of Xiangtangshan Buddha educational toys as example.
In order to solve the problem of poorly considering a system′s hierarchical structure in the current product conceptual design plan and the lack of interrelationship between multiple attributes, a multi-attribute decision-making method for product concept design based on concept hierarchy development (CHD) was proposed. Based on the CHD theory, the method divides the image of each candidate product′s conceptual design plan into three design levels: module component, angle view, and physical attribute.The similarity comparison matrix betweenmulti-attribute criteria at each level of development was constructed. The method of combining the Pythagorean fuzzy set (PFS) and theprospect theory (PT) was used to obtain the weight distribution of decision experts and attribute criteria and realize the objective and reasonable multi-attribute decision-making for product conceptual design. Finally, the feasibility and effectiveness of the method was verified by taking product conceptual design schemes of Xiangtangshan Buddha educational toys as example.
2022, 41(11): 1746-1752.
doi: 10.13433/j.cnki.1003-8728.20200525
Abstract:
The traditional machine learning methods used to tool wear monitoring often need to manually extract features, and require a long time and have low accuracy in the process of tool wear monitoring. In this paper, a tool wear condition recognition method is proposed based on one-dimensional residual convolution neural network. Firstly, the original vibration signal was processed by wavelet packet threshold denoising and fast Fourier transform. Then, the generated spectrum data was taken as a input of the residual convolution neural network model, and the feature was extracted automatically through convolution connection, residual connection and fusion, and finally matched with the tool wear state. The results show that compared with other commonly used neural networks, the proposed method in this paper improves the average accuracy by 0.6% after multiple tests and reduces the training time by 30% for spectrogram input. Thus the proposed method has the characteristics of simple process and higher accuracy, and has more advantages than other methods.
The traditional machine learning methods used to tool wear monitoring often need to manually extract features, and require a long time and have low accuracy in the process of tool wear monitoring. In this paper, a tool wear condition recognition method is proposed based on one-dimensional residual convolution neural network. Firstly, the original vibration signal was processed by wavelet packet threshold denoising and fast Fourier transform. Then, the generated spectrum data was taken as a input of the residual convolution neural network model, and the feature was extracted automatically through convolution connection, residual connection and fusion, and finally matched with the tool wear state. The results show that compared with other commonly used neural networks, the proposed method in this paper improves the average accuracy by 0.6% after multiple tests and reduces the training time by 30% for spectrogram input. Thus the proposed method has the characteristics of simple process and higher accuracy, and has more advantages than other methods.
2022, 41(11): 1753-1758.
doi: 10.13433/j.cnki.1003-8728.20200472
Abstract:
A pulse width modulation (PWM) type hydraulic transformer is designed in this study, which is composed of pump / motor flow measuring unit and control valve group. By controlling the duty ratio of pulse width signals of high-speed on-off valves on both sides of A and B, the pressure transformation function is realized. This paper introduces the working principle of PWM type hydraulic transformer, verifies the feasibility of its principle through theoretical derivation and mathematical modeling, and makes simulation analysis on the pressure transformation process of PWM type hydraulic transformer using AMESim simulation software. The PWM type hydraulic transformer has flexible control and wide range of pressure transformation. It may be used as a secondary regulating element in the hydraulic constant pressure network system to drive the linear load, and it may also recover the pressure energy at the load end, which is of great significance to improve the efficiency of the hydraulic system.
A pulse width modulation (PWM) type hydraulic transformer is designed in this study, which is composed of pump / motor flow measuring unit and control valve group. By controlling the duty ratio of pulse width signals of high-speed on-off valves on both sides of A and B, the pressure transformation function is realized. This paper introduces the working principle of PWM type hydraulic transformer, verifies the feasibility of its principle through theoretical derivation and mathematical modeling, and makes simulation analysis on the pressure transformation process of PWM type hydraulic transformer using AMESim simulation software. The PWM type hydraulic transformer has flexible control and wide range of pressure transformation. It may be used as a secondary regulating element in the hydraulic constant pressure network system to drive the linear load, and it may also recover the pressure energy at the load end, which is of great significance to improve the efficiency of the hydraulic system.
2022, 41(11): 1759-1764.
doi: 10.13433/j.cnki.1003-8728.20200465
Abstract:
Aiming at the shortcomings of the standard particle swarm algorithm in the path planning of mobile robots, such as slow convergence, easy to fall into the "premature" phenomenon, and unsmooth path, the particle swarm optimization algorithm is improved in this paper. When the particles fall into the local optimal value, this improved method can slightly perturb the speed of the global optimal particle to increase the convergence speed. In order to balance the local and global search capabilities, nonlinear inertia weights are proposed. Finally, a fitness function considering the shortest path and smoothness is also proposed. The simulation results show that in a dynamic environment, the improved particle swarm optimization algorithm converges quickly, avoids obstacles, and finds the optimal path that meets the requirements.
Aiming at the shortcomings of the standard particle swarm algorithm in the path planning of mobile robots, such as slow convergence, easy to fall into the "premature" phenomenon, and unsmooth path, the particle swarm optimization algorithm is improved in this paper. When the particles fall into the local optimal value, this improved method can slightly perturb the speed of the global optimal particle to increase the convergence speed. In order to balance the local and global search capabilities, nonlinear inertia weights are proposed. Finally, a fitness function considering the shortest path and smoothness is also proposed. The simulation results show that in a dynamic environment, the improved particle swarm optimization algorithm converges quickly, avoids obstacles, and finds the optimal path that meets the requirements.
2022, 41(11): 1765-1772.
doi: 10.13433/j.cnki.1003-8728.20200530
Abstract:
Gear bending fatigue has an important impact on the safe operation of urban railway vehicles. According to the load characteristics of urban railway vehicles, this paper establishes a gear fatigue life prediction model suitable for urban railway vehicles. By analyzing the gear load characteristics of the actual operation condition of urban rail vehicles, and combining the cumulative load frequency of the driving gear, the two-stage load is determined; using the two-level stress ratio as the damage parameter, the bending fatigue test and life prediction of urban rail train gears are carried out. The research results show that the fatigue life of the gear under two-stage load is significantly lower than that under a single load. By comparing the prediction results of the fatigue life prediction model proposed in this paper with the test data, it is found that the fatigue life prediction model established in this paper can predict the bending fatigue life of gears more accurately.
Gear bending fatigue has an important impact on the safe operation of urban railway vehicles. According to the load characteristics of urban railway vehicles, this paper establishes a gear fatigue life prediction model suitable for urban railway vehicles. By analyzing the gear load characteristics of the actual operation condition of urban rail vehicles, and combining the cumulative load frequency of the driving gear, the two-stage load is determined; using the two-level stress ratio as the damage parameter, the bending fatigue test and life prediction of urban rail train gears are carried out. The research results show that the fatigue life of the gear under two-stage load is significantly lower than that under a single load. By comparing the prediction results of the fatigue life prediction model proposed in this paper with the test data, it is found that the fatigue life prediction model established in this paper can predict the bending fatigue life of gears more accurately.
2022, 41(11): 1773-1779.
doi: 10.13433/j.cnki.1003-8728.20220240
Abstract:
In order to study the influence of the cooling mode on the temperature field and second-order motion of the diesel engine piston, the surface temperature of two differences structure models with and without blind cooling holes in the piston core of diesel engine was measured by using the plug of hardness test method. The finite element method was used to simulate the temperature field which the results was verified by the experiment data, as well as the effect of the two different piston structure on the thermal load was studied. The results show that the blind holes in the piston core of diesel engine can decrease the temperature of piston comparing with that without blind holes, the temperature of piston second groove in TS reduced 13.2 ℃, and the skirt temperature reduced 11 ℃. At the same time, the temperature in the piston core reduces the largest up to 25 ℃, was reduced by 10%. In addition, the contact pressure, wear load and friction loss of the piston skirt are significantly reduced.
In order to study the influence of the cooling mode on the temperature field and second-order motion of the diesel engine piston, the surface temperature of two differences structure models with and without blind cooling holes in the piston core of diesel engine was measured by using the plug of hardness test method. The finite element method was used to simulate the temperature field which the results was verified by the experiment data, as well as the effect of the two different piston structure on the thermal load was studied. The results show that the blind holes in the piston core of diesel engine can decrease the temperature of piston comparing with that without blind holes, the temperature of piston second groove in TS reduced 13.2 ℃, and the skirt temperature reduced 11 ℃. At the same time, the temperature in the piston core reduces the largest up to 25 ℃, was reduced by 10%. In addition, the contact pressure, wear load and friction loss of the piston skirt are significantly reduced.
2022, 41(11): 1780-1793.
doi: 10.13433/j.cnki.1003-8728.20200536
Abstract:
According to the literature on fuel cell bipolar plate materials and preparation processes published in the Web of Science core collection database from January 2000 to October 2020, the literature metrology analysis is carried out, and the core research is drawn by using the CiteSpace visual analysis tool. A structural map of the evolution of countries, authors, research institutions, and keywords. The data analysis results show that the research hotspots of bipolar plates are mainly the corrosion resistance of metal bipolar plates and the conductivity of polymer-based composite bipolar plates. The corrosion resistance of metal plates has research contents such as ion pollution, substrate materials and coating technology. Ion pollution studies have revealed the negative effects of plate corrosion. Research on substrate materials and coating technology involves adjusting the material composition or preparation process. The research content of the conductivity of polymer composites is the model for polymer matrix, conductive filler and composite conductivity. The modelfor conductivity is an important theoretical basis for studying the composite composition.
According to the literature on fuel cell bipolar plate materials and preparation processes published in the Web of Science core collection database from January 2000 to October 2020, the literature metrology analysis is carried out, and the core research is drawn by using the CiteSpace visual analysis tool. A structural map of the evolution of countries, authors, research institutions, and keywords. The data analysis results show that the research hotspots of bipolar plates are mainly the corrosion resistance of metal bipolar plates and the conductivity of polymer-based composite bipolar plates. The corrosion resistance of metal plates has research contents such as ion pollution, substrate materials and coating technology. Ion pollution studies have revealed the negative effects of plate corrosion. Research on substrate materials and coating technology involves adjusting the material composition or preparation process. The research content of the conductivity of polymer composites is the model for polymer matrix, conductive filler and composite conductivity. The modelfor conductivity is an important theoretical basis for studying the composite composition.
2022, 41(11): 1794-1804.
doi: 10.13433/j.cnki.1003-8728.20200520
Abstract:
The residual stress is one of the important characterizations of the shot peening effect. In order to study the distribution of residual stresses after milling and shot peening of blade with typical thin-walled structural characteristics, the three-dimensional residual stresses of the titanium alloy blade are tested with X-ray diffraction method with the specific structural characteristics of the blade as the object of study. The residual stresses on the blade back and the blade basin surface are the compressive residual stresses, and there is no consistent pattern of distribution, but the distribution trend of the residual stresses on the blade back and the blade basin along the depth direction is generally consistent; finally, according to the basis of the surface and the subsurface residual stress of the blade, the empirical formula for predicting the residual stresses based on the three-dimensional coordinates of the leaf (x-y-h) distribution was obtained with the numerical fitting method. The residual stress of the specific points validates the feasibility of the empirical formula for the three-dimensional characterization of residual stress in shot peening.
The residual stress is one of the important characterizations of the shot peening effect. In order to study the distribution of residual stresses after milling and shot peening of blade with typical thin-walled structural characteristics, the three-dimensional residual stresses of the titanium alloy blade are tested with X-ray diffraction method with the specific structural characteristics of the blade as the object of study. The residual stresses on the blade back and the blade basin surface are the compressive residual stresses, and there is no consistent pattern of distribution, but the distribution trend of the residual stresses on the blade back and the blade basin along the depth direction is generally consistent; finally, according to the basis of the surface and the subsurface residual stress of the blade, the empirical formula for predicting the residual stresses based on the three-dimensional coordinates of the leaf (x-y-h) distribution was obtained with the numerical fitting method. The residual stress of the specific points validates the feasibility of the empirical formula for the three-dimensional characterization of residual stress in shot peening.
