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RSS2020 Vol. 39, No. 11
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2020, 39(11): 1641-1646.
doi: 10.13433/j.cnki.1003-8728.20190334
PDF 1572KB
Abstract:
Considering the influence of the free damping layer distribution, this paper proposed an optimization method for the acoustic radiation reduction of the composite plate in vehicle. Taking the sum of the amplitudes of the normal vibration velocity of the composite plate as the simplified target, a parameterized level set method based on globally supported radial basis function (GSRBF) interpolation was adopted. Under the constraint of the material volume fraction of the damping layer, the variation of the objective function was solved to obtain the velocity field of level set function. A numerical example was used to verify that the model can reduce the acoustic radiation power while avoiding complex calculations. It is proved that the parameterized level set method is effective for the topology optimization of composite plate structure for acoustic radiation reduction.
Considering the influence of the free damping layer distribution, this paper proposed an optimization method for the acoustic radiation reduction of the composite plate in vehicle. Taking the sum of the amplitudes of the normal vibration velocity of the composite plate as the simplified target, a parameterized level set method based on globally supported radial basis function (GSRBF) interpolation was adopted. Under the constraint of the material volume fraction of the damping layer, the variation of the objective function was solved to obtain the velocity field of level set function. A numerical example was used to verify that the model can reduce the acoustic radiation power while avoiding complex calculations. It is proved that the parameterized level set method is effective for the topology optimization of composite plate structure for acoustic radiation reduction.
2020, 39(11): 1647-1655.
doi: 10.13433/j.cnki.1003-8728.20200270
Abstract:
The structural local damage can be caused by excessive vibration level of complex structural system, such as aircraft and automobile. The transfer path analysis (TPA) methods are main tools to study structural system vibration. The vibration load contribution of each path and the main source of vibration are usually identified using TPA methods. Nearly for 40 years, 8 TPA methods have been developed including conventional TPA (CTPA), operational TPA (OTPA/OPA), operational path analysis with exogeneous inputs (OPAX), fast TPA (FTPA), multi-level TPA (MTPA), hybrid TPA (HTPA), inverse substructure TPA (ITPA) and global transfer direct transfer method (GTDT). In order to better understand different TPA methods in vibration transmission analysis and use those to identify seat vibration sources of large civil airplane for comfort design, these TPA methods are reviewed, their basic principles and characteristics are summarized. And the applications of different TPA methods are compared. Finally, based on the study of seat comfort of airliner, the applicability of these methods is discussed, and some suggestions are given for the future study of TPA methods.
The structural local damage can be caused by excessive vibration level of complex structural system, such as aircraft and automobile. The transfer path analysis (TPA) methods are main tools to study structural system vibration. The vibration load contribution of each path and the main source of vibration are usually identified using TPA methods. Nearly for 40 years, 8 TPA methods have been developed including conventional TPA (CTPA), operational TPA (OTPA/OPA), operational path analysis with exogeneous inputs (OPAX), fast TPA (FTPA), multi-level TPA (MTPA), hybrid TPA (HTPA), inverse substructure TPA (ITPA) and global transfer direct transfer method (GTDT). In order to better understand different TPA methods in vibration transmission analysis and use those to identify seat vibration sources of large civil airplane for comfort design, these TPA methods are reviewed, their basic principles and characteristics are summarized. And the applications of different TPA methods are compared. Finally, based on the study of seat comfort of airliner, the applicability of these methods is discussed, and some suggestions are given for the future study of TPA methods.
Study on Kriging Approximate Prediction Model for Residual Stress in Girdle Welding of Vertical Pipe
2020, 39(11): 1656-1661.
doi: 10.13433/j.cnki.1003-8728.20190323
Abstract:
As an important part of the floating platform, the deep-sea riser connects the offshore oil and gas resources closely with the offshore platform. The welding residual stress will affect the mechanical properties of the pipe and its fatigue damage life. The finite element model for deep-sea riser of API5LX65 pipeline steel is established by using MSC. Marc software, and the filling process is simulated by using the moving double ellipsoid heat source model and the birth and death element method, and the seam welding process for pipe simulated with the thermal-mechanical coupling method, and the welding residual stress and temperature field distribution are obtained. The variation in residual stress under different parameters was obtained by using the single factor analysis with control variable method. On the above-mentioned, the welding process parameters were selected as the influencing parameters for orthogonal experimental design to obtain sample points, the welding residual stress was taken as the response parameters, Kriging numerical model was established and the response surface was plotted, and the present finite element model was applied and the accuracy via Kriging model was compared. The Kriging model can replace the finite element model for quickly and accurately predicting the residual stress in the welding process under different parameters, which has a significance in engineering.
As an important part of the floating platform, the deep-sea riser connects the offshore oil and gas resources closely with the offshore platform. The welding residual stress will affect the mechanical properties of the pipe and its fatigue damage life. The finite element model for deep-sea riser of API5LX65 pipeline steel is established by using MSC. Marc software, and the filling process is simulated by using the moving double ellipsoid heat source model and the birth and death element method, and the seam welding process for pipe simulated with the thermal-mechanical coupling method, and the welding residual stress and temperature field distribution are obtained. The variation in residual stress under different parameters was obtained by using the single factor analysis with control variable method. On the above-mentioned, the welding process parameters were selected as the influencing parameters for orthogonal experimental design to obtain sample points, the welding residual stress was taken as the response parameters, Kriging numerical model was established and the response surface was plotted, and the present finite element model was applied and the accuracy via Kriging model was compared. The Kriging model can replace the finite element model for quickly and accurately predicting the residual stress in the welding process under different parameters, which has a significance in engineering.
2020, 39(11): 1662-1670.
doi: 10.13433/j.cnki.1003-8728.20190329
Abstract:
Extreme-point weighted mode decomposition (EWMD) is an adaptive signal processing method based on empirical mode decomposition (EMD). Aiming at mode mixing problem of EWMD, the complete ensemble extreme-point weighted mode decomposition with adaptive noise (CEEWMDAN) is proposed in this paper. CEEWMDAN extracts intrinsic mode function by adding the assisted noise to original signal and using the improved mean curve, which effectively restrains the mode mixing and reduces the computational complexity. Its effectiveness is verified by simulation experimental data analysis. Finally, a fault diagnosis method for low-speed rolling bearings based on CEEWMDAN and fast spectral kurtosis is proposed and applied to the measured data analysis. The results show that the proposed fault diagnosis method can effectively identify low-speed rolling bearing faults.
Extreme-point weighted mode decomposition (EWMD) is an adaptive signal processing method based on empirical mode decomposition (EMD). Aiming at mode mixing problem of EWMD, the complete ensemble extreme-point weighted mode decomposition with adaptive noise (CEEWMDAN) is proposed in this paper. CEEWMDAN extracts intrinsic mode function by adding the assisted noise to original signal and using the improved mean curve, which effectively restrains the mode mixing and reduces the computational complexity. Its effectiveness is verified by simulation experimental data analysis. Finally, a fault diagnosis method for low-speed rolling bearings based on CEEWMDAN and fast spectral kurtosis is proposed and applied to the measured data analysis. The results show that the proposed fault diagnosis method can effectively identify low-speed rolling bearing faults.
2020, 39(11): 1671-1675.
doi: 10.13433/j.cnki.1003-8728.20190311
Abstract:
For the wind turbine gearbox bearing temperature is susceptible to random factors and its prediction accuracy is often low. In order to accurately predict the short term temperature change of gearbox bearing temperature, a predictive model which combined Principal Component Analysis (PCA), Genetic Algorithm (GA) and Elman neural network is proposed through the research on the development trend of wind turbine gearbox bearing temperature. At first, the model reduces the dimension of high-dimensional complex primitives by principal component analysis and then the principal component (PC) obtained is used as the input of the GA-optimized Elman neural network. This new method takes into account the random fluctuations in the bearing temperature development trend and fully exploits the laws of historical data changes. The application results show that the new method has a good fitting effect on the random fluctuation trend in the development of bearing temperature, and the stability and accuracy are better than other methods in the paper, which can effectively predict the bearing temperature.
For the wind turbine gearbox bearing temperature is susceptible to random factors and its prediction accuracy is often low. In order to accurately predict the short term temperature change of gearbox bearing temperature, a predictive model which combined Principal Component Analysis (PCA), Genetic Algorithm (GA) and Elman neural network is proposed through the research on the development trend of wind turbine gearbox bearing temperature. At first, the model reduces the dimension of high-dimensional complex primitives by principal component analysis and then the principal component (PC) obtained is used as the input of the GA-optimized Elman neural network. This new method takes into account the random fluctuations in the bearing temperature development trend and fully exploits the laws of historical data changes. The application results show that the new method has a good fitting effect on the random fluctuation trend in the development of bearing temperature, and the stability and accuracy are better than other methods in the paper, which can effectively predict the bearing temperature.
2020, 39(11): 1676-1684.
doi: 10.13433/j.cnki.1003-8728.20200186
Abstract:
Ankles can benefit from the elastic tube bandage (ETB) by providing the ankle joint with compression. Partial high-or low-pressure leads to human body discomfort. This objective was to propose a method for analyzing the ankle shape with the fabric compression according to the comfortable pressure on human body. By establishing the relationship between the pressure and the ankle shape, the mapping of the fabric warp and weft threads of the ETB on the ankle shape was matched and the corresponding fabric shape curves which provide pressure as the tension were constructed by the U-direction convex curves of ankle. According to the scanned data of 306 lower limbs, the ankles were divided into the nine groups. A standard shape model for ankles was established and each group had a proportional coefficient to it. The maximum pressure of each group could be calculated by using the corresponding position of U-direction characteristic curves and the ankle with minimum pressure areas were also found out at the same time. The calculated result showed that there were six sizes of ETB match for the nine groups of ankles. The method of adjusting the fabric morphological curves was proposed not only to eliminate the problem of uneven pressure distribution but also to increase the required pressure at the corresponding areas. The conclusion of the ankle with the fit pressure should be based on the sizes and shapes which can be applied to the comfort design of ETB for mass users.
Ankles can benefit from the elastic tube bandage (ETB) by providing the ankle joint with compression. Partial high-or low-pressure leads to human body discomfort. This objective was to propose a method for analyzing the ankle shape with the fabric compression according to the comfortable pressure on human body. By establishing the relationship between the pressure and the ankle shape, the mapping of the fabric warp and weft threads of the ETB on the ankle shape was matched and the corresponding fabric shape curves which provide pressure as the tension were constructed by the U-direction convex curves of ankle. According to the scanned data of 306 lower limbs, the ankles were divided into the nine groups. A standard shape model for ankles was established and each group had a proportional coefficient to it. The maximum pressure of each group could be calculated by using the corresponding position of U-direction characteristic curves and the ankle with minimum pressure areas were also found out at the same time. The calculated result showed that there were six sizes of ETB match for the nine groups of ankles. The method of adjusting the fabric morphological curves was proposed not only to eliminate the problem of uneven pressure distribution but also to increase the required pressure at the corresponding areas. The conclusion of the ankle with the fit pressure should be based on the sizes and shapes which can be applied to the comfort design of ETB for mass users.
2020, 39(11): 1685-1690.
doi: 10.13433/j.cnki.1003-8728.20190322
Abstract:
This paper focuses on the vibration and noise reduction of the transmission box for hydraulic mechanical continuous variable transmission in tractor. The dynamic characteristics of the transmission box are analyzed, and the optimum design of the box is also carried out with the structural optimization method. According to the geometric model of initial design of the transmission box, the finite element model of the box is developed via coupling between the shell and the solid elements. The modal analysis and transient dynamic analysis of the transmission box are performed. According to the analysis results, the maximization of the weighted natural frequencies of the first six modes is determined as the optimization objective. A combined topology and topography optimization scheme is employed to optimize the distribution of material and stiffener. The simulation results indicate that the strength and stiffness of the transmission box meet the design requirements and the box mass is reduced by 8.7%. Meanwhile, the natural frequencies of the first six modes are improved to avoid the excitation frequencies. This scheme provides a reference for the optimization design of the similar transmission box, which is beneficial to reduce the product design cost and shorten the design cycle.
This paper focuses on the vibration and noise reduction of the transmission box for hydraulic mechanical continuous variable transmission in tractor. The dynamic characteristics of the transmission box are analyzed, and the optimum design of the box is also carried out with the structural optimization method. According to the geometric model of initial design of the transmission box, the finite element model of the box is developed via coupling between the shell and the solid elements. The modal analysis and transient dynamic analysis of the transmission box are performed. According to the analysis results, the maximization of the weighted natural frequencies of the first six modes is determined as the optimization objective. A combined topology and topography optimization scheme is employed to optimize the distribution of material and stiffener. The simulation results indicate that the strength and stiffness of the transmission box meet the design requirements and the box mass is reduced by 8.7%. Meanwhile, the natural frequencies of the first six modes are improved to avoid the excitation frequencies. This scheme provides a reference for the optimization design of the similar transmission box, which is beneficial to reduce the product design cost and shorten the design cycle.
2020, 39(11): 1691-1697.
doi: 10.13433/j.cnki.1003-8728.20190296
Abstract:
In order to solve the problem that the existence of associated gas in the process of crude oil exploitation will affect the separation efficiency between the media and the ineffective emptying will affect the environment. Based on the principle of cyclone separation, we proposed an integrated cyclone design for gas and oil removal with hierarchical separated structure. This cyclone is divided into outer gas-liquid separation chamber and inner liquid-liquid separation chamber, achieving efficient separation among gas, water and oil. The structural parameters including length of cylinder part(A), cone angle(B) and inserted depth of escape-pipe(C) were optimized by the orthogonal test combined with computational fluid dynamics software. The results of comparing between direct analysis and variance analysis of the orthogonal test were coherently, the ideal parameters were obtained finally, and the separation efficiency was improved to over 95%, and the separation effect of multiphase flow separation cyclone was verified by laboratory test.
In order to solve the problem that the existence of associated gas in the process of crude oil exploitation will affect the separation efficiency between the media and the ineffective emptying will affect the environment. Based on the principle of cyclone separation, we proposed an integrated cyclone design for gas and oil removal with hierarchical separated structure. This cyclone is divided into outer gas-liquid separation chamber and inner liquid-liquid separation chamber, achieving efficient separation among gas, water and oil. The structural parameters including length of cylinder part(A), cone angle(B) and inserted depth of escape-pipe(C) were optimized by the orthogonal test combined with computational fluid dynamics software. The results of comparing between direct analysis and variance analysis of the orthogonal test were coherently, the ideal parameters were obtained finally, and the separation efficiency was improved to over 95%, and the separation effect of multiphase flow separation cyclone was verified by laboratory test.
2020, 39(11): 1698-1704.
doi: 10.13433/j.cnki.1003-8728.20190324
Abstract:
The double-span rotor test-bed was taken as the research object for numerical simulation and experimental test to simulate the oil film instability of the actual unit. From the numerical calculation, the dynamic model of the test-bed was established with the oil film force model of Capone circular bearing, based on the finite element method, and the effects of eccentricity and disc mass at different rotating speeds were compared and analyzed. From the test, the influence of disc eccentricity and disc mass on the rotor system was analyzed and compared with the simulation results. The results show that the influence of oil film oscillation on system operation is restrained to some extent by properly increasing eccentricity and turntable mass. The oil film oscillation will be delayed. But the power frequency amplitude will increase. Theoretical and practical bases are provided by these fault features for identifying oil film instability in the future.
The double-span rotor test-bed was taken as the research object for numerical simulation and experimental test to simulate the oil film instability of the actual unit. From the numerical calculation, the dynamic model of the test-bed was established with the oil film force model of Capone circular bearing, based on the finite element method, and the effects of eccentricity and disc mass at different rotating speeds were compared and analyzed. From the test, the influence of disc eccentricity and disc mass on the rotor system was analyzed and compared with the simulation results. The results show that the influence of oil film oscillation on system operation is restrained to some extent by properly increasing eccentricity and turntable mass. The oil film oscillation will be delayed. But the power frequency amplitude will increase. Theoretical and practical bases are provided by these fault features for identifying oil film instability in the future.
2020, 39(11): 1705-1712.
doi: 10.13433/j.cnki.1003-8728.20190320
Abstract:
This paper presents a wheel-legged mobile mechanism which can switch motion modes with self-adaption. The under-actuated switching design improves the ability of the mobile mechanism to cross complex terrains. The mobile mechanism can switch between wheel mode and wheel-leg mode without actuators, which reduces the complexity of the switching mechanism and its overall quality. The mobile mechanism executes its wheel mode on a flat road, and when encountering obstacles, the rotating body can be switched to wheel-leg mode. The motions in two modes such as straight-line moving and direction switching, obstacle crossing and other processes are analyzed theoretically. Dynamic simulation models are established to obtain and verify the mobile mechanism's turning radius function and maximum obstacle-crossing height. A prototype was made to verify its feasibility. Theoretical analysis and simulation results show that, the mobile mechanism has the travel stability of the traditional wheeled mechanism and the high obstacle-crossing property of a legged mechanism. The adaptive switching can significantly improve the obstacle-crossing ability of the mobile mechanism.
This paper presents a wheel-legged mobile mechanism which can switch motion modes with self-adaption. The under-actuated switching design improves the ability of the mobile mechanism to cross complex terrains. The mobile mechanism can switch between wheel mode and wheel-leg mode without actuators, which reduces the complexity of the switching mechanism and its overall quality. The mobile mechanism executes its wheel mode on a flat road, and when encountering obstacles, the rotating body can be switched to wheel-leg mode. The motions in two modes such as straight-line moving and direction switching, obstacle crossing and other processes are analyzed theoretically. Dynamic simulation models are established to obtain and verify the mobile mechanism's turning radius function and maximum obstacle-crossing height. A prototype was made to verify its feasibility. Theoretical analysis and simulation results show that, the mobile mechanism has the travel stability of the traditional wheeled mechanism and the high obstacle-crossing property of a legged mechanism. The adaptive switching can significantly improve the obstacle-crossing ability of the mobile mechanism.
2020, 39(11): 1713-1719.
doi: 10.13433/j.cnki.1003-8728.20190333
Abstract:
The dynamic hysteresis characteristics of the wire-cable vibration isolator were studied by experiments. In order to improve the fitting accuracy of the modified normalized Bouc-wen model under the condition of small amplitude, a nonlinear function about excitation displacement was first introduced into the model to complete the modeling of dynamic hysteresis characteristics of the isolator. Then, the linear least square method and adaptive unscented Kalman filter (AUKF) algorithm with noise statistic estimator were developed for model parameter identification. Research results indicated that the established model can well describe the dynamic hysteresis characteristics of the wire-cable vibration isolator, and the model parameters can be identified accurately and effectively by this identification method, the experimental hysteresis curve is consistent with the identified model fitting curve, verifying the effectiveness of the established model and the parameter identification method.
The dynamic hysteresis characteristics of the wire-cable vibration isolator were studied by experiments. In order to improve the fitting accuracy of the modified normalized Bouc-wen model under the condition of small amplitude, a nonlinear function about excitation displacement was first introduced into the model to complete the modeling of dynamic hysteresis characteristics of the isolator. Then, the linear least square method and adaptive unscented Kalman filter (AUKF) algorithm with noise statistic estimator were developed for model parameter identification. Research results indicated that the established model can well describe the dynamic hysteresis characteristics of the wire-cable vibration isolator, and the model parameters can be identified accurately and effectively by this identification method, the experimental hysteresis curve is consistent with the identified model fitting curve, verifying the effectiveness of the established model and the parameter identification method.
2020, 39(11): 1720-1727.
doi: 10.13433/j.cnki.1003-8728.20190321
Abstract:
Focusing on the intermittent turning of superalloy GH4169, the effects of the chamfer parameters in the cutting insert on the tool life and machined surface roughness by using the single factor experiment method was studied. The influences of the chamfer parameters on the tool wear mechanism were also investigated via a scanning electron microscope (SEM) and a digital microscope with super depth of field. Then the experiment results were discussed by combining the cutting impact stress and the cutting temperature obtained via finite element method. The results showed that tool life increased firstly and decreased with the increasing of chamfer angle and width, but machined surface roughness changed slightly. Properly increasing the chamfer parameters can decrease the impact stress so as to increase the tool life. But the large chamfer parameter increased significantly the cutting temperature so as to exacerbate the tool wear and decrease tool life.
Focusing on the intermittent turning of superalloy GH4169, the effects of the chamfer parameters in the cutting insert on the tool life and machined surface roughness by using the single factor experiment method was studied. The influences of the chamfer parameters on the tool wear mechanism were also investigated via a scanning electron microscope (SEM) and a digital microscope with super depth of field. Then the experiment results were discussed by combining the cutting impact stress and the cutting temperature obtained via finite element method. The results showed that tool life increased firstly and decreased with the increasing of chamfer angle and width, but machined surface roughness changed slightly. Properly increasing the chamfer parameters can decrease the impact stress so as to increase the tool life. But the large chamfer parameter increased significantly the cutting temperature so as to exacerbate the tool wear and decrease tool life.
2020, 39(11): 1728-1732.
doi: 10.13433/j.cnki.1003-8728.20190310
Abstract:
Non-contact in-line measurement and modeling methods were carried out for the transparency with large complex surface, which was suitable for the aeronautical transparencies with low toughness and scratch resistance. For the numerical control machine, the spectral confocal displacement sensor and data acquisition card to record the position coordinates of the workpiece surface were used, and the machine axes in the running process. The non-contact measurement and reconstruction model method of transparent parts were carried out by using the vector sums the two sets of data collected and the software development. The acquisition of surface point cloud, data processing and reconstruction model for surface were completed with the experiments, and the feasibility of the method was verified.
Non-contact in-line measurement and modeling methods were carried out for the transparency with large complex surface, which was suitable for the aeronautical transparencies with low toughness and scratch resistance. For the numerical control machine, the spectral confocal displacement sensor and data acquisition card to record the position coordinates of the workpiece surface were used, and the machine axes in the running process. The non-contact measurement and reconstruction model method of transparent parts were carried out by using the vector sums the two sets of data collected and the software development. The acquisition of surface point cloud, data processing and reconstruction model for surface were completed with the experiments, and the feasibility of the method was verified.
2020, 39(11): 1733-1739.
doi: 10.13433/j.cnki.1003-8728.20190325
Abstract:
To solve the problem of long test period and difficult prediction of shape and surface in the process of electrochemical machining of annular narrow slot structure, a coupled mathematical model of electric field, flow field and temperature field was established. The multi-physical field coupling simulation was conducted with the COMSOL software to obtain the distribution patterns of the density, velocity and pressure of electrolytic current in the machining gap. The simulation results on the coupling field in different periods in the machining process were compared to obtain the variation patterns of each parameter. The multi-physical field coupling simulation can accurately simulate the actual electrolytic machining process, select process parameters, provide a theoretical basis for actual processes and significantly improve the quality and efficiency of the electrolytic machining of a narrow slot.
To solve the problem of long test period and difficult prediction of shape and surface in the process of electrochemical machining of annular narrow slot structure, a coupled mathematical model of electric field, flow field and temperature field was established. The multi-physical field coupling simulation was conducted with the COMSOL software to obtain the distribution patterns of the density, velocity and pressure of electrolytic current in the machining gap. The simulation results on the coupling field in different periods in the machining process were compared to obtain the variation patterns of each parameter. The multi-physical field coupling simulation can accurately simulate the actual electrolytic machining process, select process parameters, provide a theoretical basis for actual processes and significantly improve the quality and efficiency of the electrolytic machining of a narrow slot.
2020, 39(11): 1740-1746.
doi: 10.13433/j.cnki.1003-8728.20190327
Abstract:
Based on the analysis of radial and axial interference errors of the thread milling process, this paper presents a less interference optimal method for the thread milling cutter profile by adjusting the position of the feature points for the profile. Firstly, the feature point method is used to parameterize the standard thread profile and the thread milling cutter profile, respectively. Then, the mathematical computing models of thread contour surface and thread milling envelope surface are established, and the interference error calculation model of thread milling is established. Finally, the position of the feature points for the thread milling cutter profile is transformed appropriately by using the axial and radial interference errors which is calculated by interference model, and the thread milling cutter profile is optimized to reduce the interference errors. Taking ∅8×1.5 threaded milling cutter for machining M14×1.5 internal threads as an example, the maximum interference error of the optimized thread milling cutter calculated by MATLAB is 2.6 μm, which is 67.9% lower than that of the conventional thread milling cutter (8.1 μm). The thread milling experimental results show that the maximum interference error of the optimized thread milling cutter is only 15.5 μm, which is 37.5% lower than that of the conventional thread milling cutter (24.8 μm). It can be seen that the less interference optimal method for the thread milling cutter profile established in this paper can greatly reduce the interference errors of thread milling and effectively improve the thread machining accuracy.
Based on the analysis of radial and axial interference errors of the thread milling process, this paper presents a less interference optimal method for the thread milling cutter profile by adjusting the position of the feature points for the profile. Firstly, the feature point method is used to parameterize the standard thread profile and the thread milling cutter profile, respectively. Then, the mathematical computing models of thread contour surface and thread milling envelope surface are established, and the interference error calculation model of thread milling is established. Finally, the position of the feature points for the thread milling cutter profile is transformed appropriately by using the axial and radial interference errors which is calculated by interference model, and the thread milling cutter profile is optimized to reduce the interference errors. Taking ∅8×1.5 threaded milling cutter for machining M14×1.5 internal threads as an example, the maximum interference error of the optimized thread milling cutter calculated by MATLAB is 2.6 μm, which is 67.9% lower than that of the conventional thread milling cutter (8.1 μm). The thread milling experimental results show that the maximum interference error of the optimized thread milling cutter is only 15.5 μm, which is 37.5% lower than that of the conventional thread milling cutter (24.8 μm). It can be seen that the less interference optimal method for the thread milling cutter profile established in this paper can greatly reduce the interference errors of thread milling and effectively improve the thread machining accuracy.
2020, 39(11): 1747-1752.
doi: 10.13433/j.cnki.1003-8728.20190297
Abstract:
In the mass production of box and monoblock parts, due to the clearance between the traditional location of one plane and two pins. The complete unification of datum of each process cannot be reached, which easily causes the problem of unstable product quality. A new clearance-free location method with two elastic multi-tooth cylindrical pins instead of traditional cylindrical pins and diamond pins is proposed. The elastic interval of the teeth of the locating pin is searched by the least square method, then tolerance zone of the center distance of the locating hole only satisfies to the elastic minimum interval. The clearance between the pin and the hole is eliminated through self-adaptive fitting relied the resilience of elastic teeth of location pin, consequently the real unification of location datum of each process is realized. Ultimately, the validity of the present clearance-free location method is verified via numerical simulation.
In the mass production of box and monoblock parts, due to the clearance between the traditional location of one plane and two pins. The complete unification of datum of each process cannot be reached, which easily causes the problem of unstable product quality. A new clearance-free location method with two elastic multi-tooth cylindrical pins instead of traditional cylindrical pins and diamond pins is proposed. The elastic interval of the teeth of the locating pin is searched by the least square method, then tolerance zone of the center distance of the locating hole only satisfies to the elastic minimum interval. The clearance between the pin and the hole is eliminated through self-adaptive fitting relied the resilience of elastic teeth of location pin, consequently the real unification of location datum of each process is realized. Ultimately, the validity of the present clearance-free location method is verified via numerical simulation.
2020, 39(11): 1753-1758.
doi: 10.13433/j.cnki.1003-8728.20190295
Abstract:
The relative calibration method is used to complete the calibration of the vibration sensor in this paper, the experimental sensor is put on the center of the shaking table being back-to-back with standard sensor, the data from standard vibration sensor and the experimental sensor are compared and analyzed, and introducing the uncertainty analysis. The experimental results show that the Fiber Bragg Grating(FBG) vibration sensor calibration platform is calibrated to obtain the FBG vibration sensor with a sensitivity of 5.115 pm/g, linearity of 3.5%, repeatability error of 4.9% FS, and calibration uncertainty of the calibration device is 0.003 8 g. It satisfies the calibration requirements of the FBG vibration sensor to be tested, improves the working efficiency and calibration accuracy of the FBG vibration sensor verification, and this method can be applied to practical engineering.
The relative calibration method is used to complete the calibration of the vibration sensor in this paper, the experimental sensor is put on the center of the shaking table being back-to-back with standard sensor, the data from standard vibration sensor and the experimental sensor are compared and analyzed, and introducing the uncertainty analysis. The experimental results show that the Fiber Bragg Grating(FBG) vibration sensor calibration platform is calibrated to obtain the FBG vibration sensor with a sensitivity of 5.115 pm/g, linearity of 3.5%, repeatability error of 4.9% FS, and calibration uncertainty of the calibration device is 0.003 8 g. It satisfies the calibration requirements of the FBG vibration sensor to be tested, improves the working efficiency and calibration accuracy of the FBG vibration sensor verification, and this method can be applied to practical engineering.
2020, 39(11): 1759-1765.
doi: 10.13433/j.cnki.1003-8728.20190318
Abstract:
For the unknown object of a 3D model such as reverse engineering, the existing adaptive algorithm can not be used. With point cloud information, color information and contact measurement combined, a point cloud pre-sampling surface adaptive point distribution strategy is proposed. The pre-processed depth point cloud and the point set after the HSV color space are segmented to obtain the saliency point cloud of the surface to be tested. An improved European-style segmentation algorithm based on the Gaussian curvature is proposed for point cloud segmentation. The segmentation algorithm can divide the significant point cloud into several point cloud clusters. The cost function of the centroid Voronoi tessellation is used as the weight function of the mean shift algorithm, and the specific position of the best sampling point is calculated with the point cloud cluster iteration. The sampling accuracy and efficiency of the sampling method are compared with those of uniform sampling, random sampling and adaptive sampling. The experimental results show that the 3D point cloud pre-sampling surface adaptive point distribution strategy can improve the sampling efficiency, while ensuring the measurement accuracy, which is 60% shorter than the sampling time of the adaptive sampling.
For the unknown object of a 3D model such as reverse engineering, the existing adaptive algorithm can not be used. With point cloud information, color information and contact measurement combined, a point cloud pre-sampling surface adaptive point distribution strategy is proposed. The pre-processed depth point cloud and the point set after the HSV color space are segmented to obtain the saliency point cloud of the surface to be tested. An improved European-style segmentation algorithm based on the Gaussian curvature is proposed for point cloud segmentation. The segmentation algorithm can divide the significant point cloud into several point cloud clusters. The cost function of the centroid Voronoi tessellation is used as the weight function of the mean shift algorithm, and the specific position of the best sampling point is calculated with the point cloud cluster iteration. The sampling accuracy and efficiency of the sampling method are compared with those of uniform sampling, random sampling and adaptive sampling. The experimental results show that the 3D point cloud pre-sampling surface adaptive point distribution strategy can improve the sampling efficiency, while ensuring the measurement accuracy, which is 60% shorter than the sampling time of the adaptive sampling.
2020, 39(11): 1766-1773.
doi: 10.13433/j.cnki.1003-8728.20190298
Abstract:
To accurately predict the exhaust temperature of a natural gas scroll compressor, an experimental system was established and the temperature in the main part of the scroll compressor was measured. By analyzing the temperature data, a multiple regression prediction model, a gray prediction model and a dual-mode prediction model were set up. Based on these models, the influence of such factors as inlet temperature, spindle speed and pressure ratio on the exhaust temperature are explored. Moreover, the accuracy of these models was evaluated. Finally, the exhaust temperature under different operating conditions is predicted and analyzed. The results show that the error of the multiple regression prediction model is 3.06%, the error of the gray prediction model is 2.11% and the error of the dual-mode prediction model is 1.69%. The dual-mode prediction model has the smallest error and the strongest stability. In addition, among the factors which affect exhaust temperature, the inlet temperature has the most apparent influence on the result, the spindle speed is the second and the pressure ratio is the smallest.
To accurately predict the exhaust temperature of a natural gas scroll compressor, an experimental system was established and the temperature in the main part of the scroll compressor was measured. By analyzing the temperature data, a multiple regression prediction model, a gray prediction model and a dual-mode prediction model were set up. Based on these models, the influence of such factors as inlet temperature, spindle speed and pressure ratio on the exhaust temperature are explored. Moreover, the accuracy of these models was evaluated. Finally, the exhaust temperature under different operating conditions is predicted and analyzed. The results show that the error of the multiple regression prediction model is 3.06%, the error of the gray prediction model is 2.11% and the error of the dual-mode prediction model is 1.69%. The dual-mode prediction model has the smallest error and the strongest stability. In addition, among the factors which affect exhaust temperature, the inlet temperature has the most apparent influence on the result, the spindle speed is the second and the pressure ratio is the smallest.
2020, 39(11): 1774-1781.
doi: 10.13433/j.cnki.1003-8728.20200271
Abstract:
Due to narrow sound absorption bandwidth of traditional single-layer micro-perforated panel absorber, this paper studies the sound absorption performance optimization of composite micro-perforated panel with multiple perforation rates. Based on the principle of volume flow continuity, an improved transfer matrix method is employed to derive formulas of sound absorption coefficient about composite micro-perforated panel with multiple perforation rates, and the effect of multiple perforation rates on sound absorption performance is discussed. Results of numerical simulation and experiment show consistently that the composite micro-perforated panel with multiple perforation rates has larger efficient sound absorption bandwidth than traditional single-layer plate, and different distribution of perforation rates has significant influence on the maximum sound absorption coefficient of the micro-perforated plate sound absorption structure.
Due to narrow sound absorption bandwidth of traditional single-layer micro-perforated panel absorber, this paper studies the sound absorption performance optimization of composite micro-perforated panel with multiple perforation rates. Based on the principle of volume flow continuity, an improved transfer matrix method is employed to derive formulas of sound absorption coefficient about composite micro-perforated panel with multiple perforation rates, and the effect of multiple perforation rates on sound absorption performance is discussed. Results of numerical simulation and experiment show consistently that the composite micro-perforated panel with multiple perforation rates has larger efficient sound absorption bandwidth than traditional single-layer plate, and different distribution of perforation rates has significant influence on the maximum sound absorption coefficient of the micro-perforated plate sound absorption structure.
2020, 39(11): 1782-1787.
doi: 10.13433/j.cnki.1003-8728.20190328
Abstract:
According to the principles of nest structure, a new type of nest structural non-pneumatic tire was designed, and its three-dimensional analysis model was established. The ABAQUS finite element simulation of its amount of sinking was compared with the experimental results to verify its feasibility. Its radial elastic properties were analyzed by its sinking characteristics and compared with its radial elastic properties. The pressure distribution of the nest structural non-pneumatic tire that has different numbers of arrays was studied with the finite element method. The characterization and influence factors were analyzed. The results show that with the increase of load, the amounts of sinking of the non-pneumatic tire and the pneumatic tire are similar, and that changing the number of spoke arrays can meet the requirements of different radial stiffness of the pneumatic tire. When the number of arrays is large, the grounding pressure is continuous, and the amount of sinking is large.
According to the principles of nest structure, a new type of nest structural non-pneumatic tire was designed, and its three-dimensional analysis model was established. The ABAQUS finite element simulation of its amount of sinking was compared with the experimental results to verify its feasibility. Its radial elastic properties were analyzed by its sinking characteristics and compared with its radial elastic properties. The pressure distribution of the nest structural non-pneumatic tire that has different numbers of arrays was studied with the finite element method. The characterization and influence factors were analyzed. The results show that with the increase of load, the amounts of sinking of the non-pneumatic tire and the pneumatic tire are similar, and that changing the number of spoke arrays can meet the requirements of different radial stiffness of the pneumatic tire. When the number of arrays is large, the grounding pressure is continuous, and the amount of sinking is large.
2020, 39(11): 1788-1793.
doi: 10.13433/j.cnki.1003-8728.20190326
Abstract:
Considering the fatigue behavior of polycrystalline material affected by grain topology, the finite element model for microstructure with Voronoi tessellation algorithm is established, and the grain boundary characteristics is simulated by inserting the cohesive elements. Then, based on the constitutive relationship of Abaqus bilinear cohesive force, the model for fatigue cumulative damage of cohesive element is established, and the damage variable, damage criterion and damage law are defined. The fatigue damage of cohesive elements is calculated with Abaqus User-defined material mechanical behavior. The calculation program realizes the behavior simulation of the rolling contact fatigue crack initiation and propagation under the microstructure. Finally, the contact fatigue analysis of the roller and the raceway is taken as an example. The simulation results are compared with the measured, which shows the effectiveness of the simulation method in simulating the formation and propagation of cracks for polycrystalline materials.
Considering the fatigue behavior of polycrystalline material affected by grain topology, the finite element model for microstructure with Voronoi tessellation algorithm is established, and the grain boundary characteristics is simulated by inserting the cohesive elements. Then, based on the constitutive relationship of Abaqus bilinear cohesive force, the model for fatigue cumulative damage of cohesive element is established, and the damage variable, damage criterion and damage law are defined. The fatigue damage of cohesive elements is calculated with Abaqus User-defined material mechanical behavior. The calculation program realizes the behavior simulation of the rolling contact fatigue crack initiation and propagation under the microstructure. Finally, the contact fatigue analysis of the roller and the raceway is taken as an example. The simulation results are compared with the measured, which shows the effectiveness of the simulation method in simulating the formation and propagation of cracks for polycrystalline materials.
2020, 39(11): 1794-1804.
doi: 10.13433/j.cnki.1003-8728.20190317
Abstract:
This work established a dynamic model of intershaft bearing-dual rotors in aero-engine with the theory of rotor dynamics and Lagrange equation. The vibration characteristics were examined by numerical simulation. With the time-varying stiffness curve, amplitude-frequency curve, three-dimensional waterfall plot, bifurcation diagram, Poincare map and so on, the time-varying stiffness characteristic, intershaft bearing force, primary resonance, spectrum characteristic, bifurcation and chaos characteristics of the ideal intershaft bearing-dual rotor system and the system with surface waviness on the intershaft bearing are analyzed comparatively. The results show that the surface waviness of the intershaft bearing complicated the vibration condition of the dual rotor system. The surface waviness has significant influence on the dual rotor system, especially at the lower speed.
This work established a dynamic model of intershaft bearing-dual rotors in aero-engine with the theory of rotor dynamics and Lagrange equation. The vibration characteristics were examined by numerical simulation. With the time-varying stiffness curve, amplitude-frequency curve, three-dimensional waterfall plot, bifurcation diagram, Poincare map and so on, the time-varying stiffness characteristic, intershaft bearing force, primary resonance, spectrum characteristic, bifurcation and chaos characteristics of the ideal intershaft bearing-dual rotor system and the system with surface waviness on the intershaft bearing are analyzed comparatively. The results show that the surface waviness of the intershaft bearing complicated the vibration condition of the dual rotor system. The surface waviness has significant influence on the dual rotor system, especially at the lower speed.
