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RSS2017 Vol. 36, No. 7
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2017, 36(7): 985-990.
doi: 10.13433/j.cnki.1003-8728.2017.0701
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Abstract:
In order to improve the accuracy of a radial tire's temperature field analysis, we propose a new modelling method with the external flow field considered. To study the PCR tire 205/55R16, the finite element model of the radial tire and its stable temperature field is established by using the ABAQUS and ANSYS software. The thermal parameters and the mechanical parameters of the radial tire's materials are tested with the RPA2000 instrument and the hot-disk instrument. The mechanical model of the tire is simulated with the ABAQUS software, and the flow field analysis is simulated with the ANSYS software. The convection, heat radiation, heat conduction of the radial tire are analysed with the ABAQUS software. The temperature of the radial tire is experimentally tested to prove that the simulation model is reliable. The test results show that compared with the existing methods, the new radial tire temperature field simulation method, which is helpful to study the performance of a radial tire is more accurate and reliable.
In order to improve the accuracy of a radial tire's temperature field analysis, we propose a new modelling method with the external flow field considered. To study the PCR tire 205/55R16, the finite element model of the radial tire and its stable temperature field is established by using the ABAQUS and ANSYS software. The thermal parameters and the mechanical parameters of the radial tire's materials are tested with the RPA2000 instrument and the hot-disk instrument. The mechanical model of the tire is simulated with the ABAQUS software, and the flow field analysis is simulated with the ANSYS software. The convection, heat radiation, heat conduction of the radial tire are analysed with the ABAQUS software. The temperature of the radial tire is experimentally tested to prove that the simulation model is reliable. The test results show that compared with the existing methods, the new radial tire temperature field simulation method, which is helpful to study the performance of a radial tire is more accurate and reliable.
2017, 36(7): 991-997.
doi: 10.13433/j.cnki.1003-8728.2017.0702
Abstract:
In order to solve the problem that the gearbox of a gear system causes too large vibration and noise during operation, a magneto-rheological damper for suppressing its vibration and noise was proposed. A gear vibration and noise reduction bench was built to experimentally evaluate the damping characteristics of the magneto-rheological damper by monitoring the vibration of the bearing block, rotor and sound pressure level of the gear system. The evaluation results show that the damper can effectively reduce the gear system's vibration and noise. The root mean squares (RMS) values of the vibration acceleration and velocity of the bearing block are reduced by 50%. The peak-to-peak value of rotor vibration is reduced by 55%. The sound pressure level is reduced by 8 dB. The damper can simultaneously inhibit each frequency component of the gear system's vibration and noise in a wide frequency range. The experiments performed in the paper verify that the damper can effectively guarantee the smooth operation of the gear transmission system with good vibration reduction characteristics over a range of operating speeds.
In order to solve the problem that the gearbox of a gear system causes too large vibration and noise during operation, a magneto-rheological damper for suppressing its vibration and noise was proposed. A gear vibration and noise reduction bench was built to experimentally evaluate the damping characteristics of the magneto-rheological damper by monitoring the vibration of the bearing block, rotor and sound pressure level of the gear system. The evaluation results show that the damper can effectively reduce the gear system's vibration and noise. The root mean squares (RMS) values of the vibration acceleration and velocity of the bearing block are reduced by 50%. The peak-to-peak value of rotor vibration is reduced by 55%. The sound pressure level is reduced by 8 dB. The damper can simultaneously inhibit each frequency component of the gear system's vibration and noise in a wide frequency range. The experiments performed in the paper verify that the damper can effectively guarantee the smooth operation of the gear transmission system with good vibration reduction characteristics over a range of operating speeds.
2017, 36(7): 998-1004.
doi: 10.13433/j.cnki.1003-8728.2017.0703
Abstract:
According to the structure of Delta parallel mechanism, a novel spatial parallel mechanism with actuation redundancy that can perform three-dimensional translations was presented. The degree of freedom of the parallel mechanism was calculated based on the screw theory and the inverse position solution was analyzed. Then the Jacobian matrix of the parallel mechanism with redundant actuation was deduced by inverse position kinematics and differential method. The singularity loci of the Delta parallel mechanism was analyzed and two novel singularity loci were presented by Gosselin singularity analysis and the singularity loci of Delta mechanism and redundantly actuated parallel mechanism was compared. In order to verify the result of theoretical analysis, the concept of manipulability was introduced to evaluate the kinematical performance of the two kind of parallel mechanism based on numerical analysis method. The results of theoretical analysis indicate that the redundant actuation parallel mechanism can realize the same function as the Delta mechanism, but the second type of singularity loci are significantly less than those of Delta mechanism. The results of numerical simulation show that the suitable workspace and mechanism parameters can reduce the singularity loci of parallel mechanism and the correctness of the theoretical analysis results are verified.
According to the structure of Delta parallel mechanism, a novel spatial parallel mechanism with actuation redundancy that can perform three-dimensional translations was presented. The degree of freedom of the parallel mechanism was calculated based on the screw theory and the inverse position solution was analyzed. Then the Jacobian matrix of the parallel mechanism with redundant actuation was deduced by inverse position kinematics and differential method. The singularity loci of the Delta parallel mechanism was analyzed and two novel singularity loci were presented by Gosselin singularity analysis and the singularity loci of Delta mechanism and redundantly actuated parallel mechanism was compared. In order to verify the result of theoretical analysis, the concept of manipulability was introduced to evaluate the kinematical performance of the two kind of parallel mechanism based on numerical analysis method. The results of theoretical analysis indicate that the redundant actuation parallel mechanism can realize the same function as the Delta mechanism, but the second type of singularity loci are significantly less than those of Delta mechanism. The results of numerical simulation show that the suitable workspace and mechanism parameters can reduce the singularity loci of parallel mechanism and the correctness of the theoretical analysis results are verified.
2017, 36(7): 1005-1010.
doi: 10.13433/j.cnki.1003-8728.2017.0704
Abstract:
The flexibilities of base and joint are described by a linear extension-compression spring and a linear torsion spring, respectively. The dynamic model of flexible-base and flexible-joint space manipulator with an attitude-controlled base is established with the linear momentum conservation principle and the second Lagrange modeling method. The flexibility compensating concept is integrated into the singular perturbation technique, and then the slow subsystem which describes the rigid motion of the system and the fast subsystem which describes the base and the flexible motions of joints are derived. Moreover, an improved singular perturbation control scheme consisting of a slow control for coordinated motion and an optimal control based on a high-order fast state observer is presented. Comparing with the traditional singular perturbation scheme, the improved control scheme can avoid the real-time measurement and feedback of high-order fast states of the system effectively, and it is more suitable for controlling the flexible-base and flexible-joint space manipulator with strong joint flexibility. The simulation results indicate that the proposed improved control scheme can track the desired trajectory accurately and suppress the vibration of the base and joints effectively.
The flexibilities of base and joint are described by a linear extension-compression spring and a linear torsion spring, respectively. The dynamic model of flexible-base and flexible-joint space manipulator with an attitude-controlled base is established with the linear momentum conservation principle and the second Lagrange modeling method. The flexibility compensating concept is integrated into the singular perturbation technique, and then the slow subsystem which describes the rigid motion of the system and the fast subsystem which describes the base and the flexible motions of joints are derived. Moreover, an improved singular perturbation control scheme consisting of a slow control for coordinated motion and an optimal control based on a high-order fast state observer is presented. Comparing with the traditional singular perturbation scheme, the improved control scheme can avoid the real-time measurement and feedback of high-order fast states of the system effectively, and it is more suitable for controlling the flexible-base and flexible-joint space manipulator with strong joint flexibility. The simulation results indicate that the proposed improved control scheme can track the desired trajectory accurately and suppress the vibration of the base and joints effectively.
2017, 36(7): 1011-1015.
doi: 10.13433/j.cnki.1003-8728.2017.0705
Abstract:
In order to predict the trend of joint wear, and the result was applied to the wear can accurately make the dynamics simulation and calculation, based on the dynamic model for slider-crank mechanism with clearance, considering the contact journal and bear interface curvature radius in the process of change trend, a basis for calculating the radius of curvature of contact width change extrapolation wear simulation model is established, and with the calculated results, the wear dynamics change of mechanism is simulated, the stress distribution and the wear rules and dynamic characteristics of pin shaft under different load are gotten, the laws of the function of system degradation is found.
In order to predict the trend of joint wear, and the result was applied to the wear can accurately make the dynamics simulation and calculation, based on the dynamic model for slider-crank mechanism with clearance, considering the contact journal and bear interface curvature radius in the process of change trend, a basis for calculating the radius of curvature of contact width change extrapolation wear simulation model is established, and with the calculated results, the wear dynamics change of mechanism is simulated, the stress distribution and the wear rules and dynamic characteristics of pin shaft under different load are gotten, the laws of the function of system degradation is found.
2017, 36(7): 1016-1021.
doi: 10.13433/j.cnki.1003-8728.2017.0706
Abstract:
In order to investigate the chaos vibration control of a two-stage gear train, a nonlinear dynamics dimensionless equation of a two-stage gear train with time varying meshing stiffness, errors of transmission and backlashes was established and solved with the numerical method. The influences of excitation frequency and damping coefficient on the bifurcation and chaos properties of the system were analyzed with bifurcation diagram and Poincáre section. The study result shows that the system's motion state would change into chaos in the way of crisis or intermittency, the damping coefficient would influence the region of bifurcation; the two-stage gears would germinate crisis in the process of movement at the same time, while the second gear remained relatively stable at the bifurcation point.
In order to investigate the chaos vibration control of a two-stage gear train, a nonlinear dynamics dimensionless equation of a two-stage gear train with time varying meshing stiffness, errors of transmission and backlashes was established and solved with the numerical method. The influences of excitation frequency and damping coefficient on the bifurcation and chaos properties of the system were analyzed with bifurcation diagram and Poincáre section. The study result shows that the system's motion state would change into chaos in the way of crisis or intermittency, the damping coefficient would influence the region of bifurcation; the two-stage gears would germinate crisis in the process of movement at the same time, while the second gear remained relatively stable at the bifurcation point.
2017, 36(7): 1022-1028.
doi: 10.13433/j.cnki.1003-8728.2017.0707
Abstract:
In order to improve the vehicle ride comfort and reduce the tire dynamic load, the 2-DOF mathematical reference model of semi-active suspension system with ideal sky-hook damping is established, and then the error dynamic system is built between the actual controlled system and the reference model system. The sliding mode surface is designed with pole assignment method. Moreover, the asymptotic stability condition of suspension system is derived based on the Lyapunov theory, and the system chattering is reduced with the index control law, which makes the actual controlled system can achieve the control effect of the ideal reference model and produce the asymptotically stable sliding motion. Finally, the sliding mode variable structure control model is built based on the ideal sky-hook damping model of the semi-active suspension. Numerical simulation verification is conducted and results indicate that the sliding mode control has a good control effect of the reference model system with good adaptability and robustness.
In order to improve the vehicle ride comfort and reduce the tire dynamic load, the 2-DOF mathematical reference model of semi-active suspension system with ideal sky-hook damping is established, and then the error dynamic system is built between the actual controlled system and the reference model system. The sliding mode surface is designed with pole assignment method. Moreover, the asymptotic stability condition of suspension system is derived based on the Lyapunov theory, and the system chattering is reduced with the index control law, which makes the actual controlled system can achieve the control effect of the ideal reference model and produce the asymptotically stable sliding motion. Finally, the sliding mode variable structure control model is built based on the ideal sky-hook damping model of the semi-active suspension. Numerical simulation verification is conducted and results indicate that the sliding mode control has a good control effect of the reference model system with good adaptability and robustness.
2017, 36(7): 1029-1034.
doi: 10.13433/j.cnki.1003-8728.2017.0708
Abstract:
In order to extract the weak and low-frequency fault feature hidden in the single-channel measured signal from multi-stage gear transmissions, a joint approach of fault feature extraction based on empirical mode decomposition (EMD) and constrained independent component analysis (cICA) is proposed in this paper. Firstly, the single-channel measured signal is decomposed into several IMFs with EMD. Then, the kurtosis and cross-correlation coefficient of each IMF are computed, and the suitable IMFs for constructing the new measured virtual vector are selected. Finally, the proper reference signal including gear fault feature frequency is constructed, and the desired low-frequency slight feature is extracted with cICA method. Through the experiment analysis of fault feature extraction on the low-speed gears with a missed tooth, the effectiveness and applicability of the proposed method is verified.
In order to extract the weak and low-frequency fault feature hidden in the single-channel measured signal from multi-stage gear transmissions, a joint approach of fault feature extraction based on empirical mode decomposition (EMD) and constrained independent component analysis (cICA) is proposed in this paper. Firstly, the single-channel measured signal is decomposed into several IMFs with EMD. Then, the kurtosis and cross-correlation coefficient of each IMF are computed, and the suitable IMFs for constructing the new measured virtual vector are selected. Finally, the proper reference signal including gear fault feature frequency is constructed, and the desired low-frequency slight feature is extracted with cICA method. Through the experiment analysis of fault feature extraction on the low-speed gears with a missed tooth, the effectiveness and applicability of the proposed method is verified.
2017, 36(7): 1035-1041.
doi: 10.13433/j.cnki.1003-8728.2017.0709
Abstract:
In order to improve the safety and reliability of axial piston pump, it is very important to determine the scope of working conditions reasonably. In this paper, the effect of oil air content, variable speed and temperature on flow of pump outlet is studied based on FLUENT. The simulation results show that the air content of the oil has greater impact on oil compressibility, but little influence on leakage. Under a certain load pressure, once the speed is about more than 2600rpm, volumetric efficiency is decreased with the raising of speed, while the compression volume and leakage volume is increased with the increasing of temperature. Finally, the accuracy of the model is verified by experiments, which also provides an effective tool for carrying out the nonlinear dynamical systems and the evolution of fault mechanism to piston pump research.
In order to improve the safety and reliability of axial piston pump, it is very important to determine the scope of working conditions reasonably. In this paper, the effect of oil air content, variable speed and temperature on flow of pump outlet is studied based on FLUENT. The simulation results show that the air content of the oil has greater impact on oil compressibility, but little influence on leakage. Under a certain load pressure, once the speed is about more than 2600rpm, volumetric efficiency is decreased with the raising of speed, while the compression volume and leakage volume is increased with the increasing of temperature. Finally, the accuracy of the model is verified by experiments, which also provides an effective tool for carrying out the nonlinear dynamical systems and the evolution of fault mechanism to piston pump research.
2017, 36(7): 1042-1047.
doi: 10.13433/j.cnki.1003-8728.2017.0710
Abstract:
The working principle and mechanical characteristics in the BTA deep hole drilling is analyzed, and a model for contact analysis between the drilled hole wall and the guide pads of BTA drill is established via commercial software ANSYS. By the statics simulation analysis, the actual contacting state between the drilled hole wall and the guide pads in the drilling process of staggered teeth BTA drill is presented. The change laws of contacting stress and contacting area with position angle of guide pads are analyzed. The results show that the contacting area via FE simulation is nearly similar to the wear area of guide pads in the actual drilling. The contacting area between the drilled hole wall and the guide pads is very small, and mainly concentrates on the front of guide pads. The position angles of guide pads have important effect on contacting stress and contacting area. The optimization of the position angles of guide pads can well improve the contacting state, which provides the laws for optimizing design of staggered teeth BTA drill.
The working principle and mechanical characteristics in the BTA deep hole drilling is analyzed, and a model for contact analysis between the drilled hole wall and the guide pads of BTA drill is established via commercial software ANSYS. By the statics simulation analysis, the actual contacting state between the drilled hole wall and the guide pads in the drilling process of staggered teeth BTA drill is presented. The change laws of contacting stress and contacting area with position angle of guide pads are analyzed. The results show that the contacting area via FE simulation is nearly similar to the wear area of guide pads in the actual drilling. The contacting area between the drilled hole wall and the guide pads is very small, and mainly concentrates on the front of guide pads. The position angles of guide pads have important effect on contacting stress and contacting area. The optimization of the position angles of guide pads can well improve the contacting state, which provides the laws for optimizing design of staggered teeth BTA drill.
2017, 36(7): 1048-1054.
doi: 10.13433/j.cnki.1003-8728.2017.0711
Abstract:
In order to improve the dynamic reliability of roadheader, based on rock cutting mechanism and combined with the actual working condition, the roadheader load files were obtained using the "vertical axis roadheader design and loads analysis software". The equivalent stress contour of the gyration platform was obtained with the ADAMS software,and the fatigue life-reliability degree membership function was established based on the reliability theory. The fatigue life analysis of gyration platform was performed by using NSOFT software. With the reliability of the bolt-set as the training sample, the optimization design was conducted for the gyration platform using particle swarm optimization(PSO), and the optimal parameters of gyration platform bolt-set was obtained. The results show that the maximum equivalent stress of gyration platform was reduced by 31.669%, the minimum fatigue life was increase from 1.706×103 to 2.487 4×106, which meet the design requirements.
In order to improve the dynamic reliability of roadheader, based on rock cutting mechanism and combined with the actual working condition, the roadheader load files were obtained using the "vertical axis roadheader design and loads analysis software". The equivalent stress contour of the gyration platform was obtained with the ADAMS software,and the fatigue life-reliability degree membership function was established based on the reliability theory. The fatigue life analysis of gyration platform was performed by using NSOFT software. With the reliability of the bolt-set as the training sample, the optimization design was conducted for the gyration platform using particle swarm optimization(PSO), and the optimal parameters of gyration platform bolt-set was obtained. The results show that the maximum equivalent stress of gyration platform was reduced by 31.669%, the minimum fatigue life was increase from 1.706×103 to 2.487 4×106, which meet the design requirements.
2017, 36(7): 1055-1062.
doi: 10.13433/j.cnki.1003-8728.2017.0712
Abstract:
The contact zone of the traditional processing of spiral bevel gears prevents diagonal tooth contact problem. Therefore, the spread-out helix modified roll is used. The passive gear is machined by the generation method; the drive gear is machined by the helix modified roll method. According to the principles of these new methods, given the movement of the machine tool, then based on the gear meshing theory, the equations for cutting tool surface and the individual gear meshing equation are established respectively. The mathematical models of cutting tooth surfaces are obtained. The three-dimensional (3D) models of gear pairs are built based on the equations for cutting tooth surfaces. Finally, the computer simulation analysis is carried out. The analysis results show that the bias of the tooth contact zone is essentially prevented by using the spread-out helix modified roll.
The contact zone of the traditional processing of spiral bevel gears prevents diagonal tooth contact problem. Therefore, the spread-out helix modified roll is used. The passive gear is machined by the generation method; the drive gear is machined by the helix modified roll method. According to the principles of these new methods, given the movement of the machine tool, then based on the gear meshing theory, the equations for cutting tool surface and the individual gear meshing equation are established respectively. The mathematical models of cutting tooth surfaces are obtained. The three-dimensional (3D) models of gear pairs are built based on the equations for cutting tooth surfaces. Finally, the computer simulation analysis is carried out. The analysis results show that the bias of the tooth contact zone is essentially prevented by using the spread-out helix modified roll.
2017, 36(7): 1063-1067.
doi: 10.13433/j.cnki.1003-8728.2017.0713
Abstract:
In order to improve the fatigue resistance and corrosion resistance of titanium alloy, the tests of abrasive belt grinding of titanium alloy are conducted on different prestressed conditions(0,100 MPa and 200 MPa)based on the principle of prestressed abrasive belt grinding. On different prestressed conditions, the influence rules of the residual stress, surface roughness, hardness and surface topography of the workpiece are obtained by testing and analyzing the surface integrity of the workpiece. Based on the model of abrasive belt grain, the mechanisms that prestressed abrasive belt grinding affects the residual stress and surface topography are revealed. The research shows that, within the elastic deformation limit of titanium alloy, the condition of compressive residual stress on surface of workpiece can be actively strengthened by applying prestress. The larger the magnitude of prestress is, the larger the compressive residual stress. The influence of prestressed abrasive belt grinding on the surface hardness is insignificant, and the surface hardness does not change with prestress. The workpiece machined by prestressed abrasive belt grinding can obtain good surface topography but there is slight increase in roughness.
In order to improve the fatigue resistance and corrosion resistance of titanium alloy, the tests of abrasive belt grinding of titanium alloy are conducted on different prestressed conditions(0,100 MPa and 200 MPa)based on the principle of prestressed abrasive belt grinding. On different prestressed conditions, the influence rules of the residual stress, surface roughness, hardness and surface topography of the workpiece are obtained by testing and analyzing the surface integrity of the workpiece. Based on the model of abrasive belt grain, the mechanisms that prestressed abrasive belt grinding affects the residual stress and surface topography are revealed. The research shows that, within the elastic deformation limit of titanium alloy, the condition of compressive residual stress on surface of workpiece can be actively strengthened by applying prestress. The larger the magnitude of prestress is, the larger the compressive residual stress. The influence of prestressed abrasive belt grinding on the surface hardness is insignificant, and the surface hardness does not change with prestress. The workpiece machined by prestressed abrasive belt grinding can obtain good surface topography but there is slight increase in roughness.
2017, 36(7): 1068-1072.
doi: 10.13433/j.cnki.1003-8728.2017.0714
Abstract:
With Simufact.Forming software, the finite element model for power spinning of plate blank was established, and the forming process of conical thin-wall spun parts with straight flange had been simulated. The flatness error via least square method was taken as the evaluation index of flange flatness. In addition, the single factor design was used. The influence of the process parameters, including mandrel rotational velocity, roller feed velocity, roller nose radius and roller mounting angle on the flange flatness of conical thin-wall spun parts was obtained. The results indicated that flange flatness is improved with the increasing of mandrel rotational velocity, however, the effect of the mandrel rotational velocity increasing up to a certain value on the flange flatness was slightt. When roller feed velocity increased, the flange flatness was deteriorated. The roller nose radius and roller mounting angle had a compliex effect on the flange flatness, in other words, the flange flatness was first improved and then deteriorated when the roller nose radius or roller mounting angle increased. The further computer simulation with appropriate process parameters based on the obtained simulation results was conducted, which showed the flange had a minimum flatness error comparing with the other simulated.
With Simufact.Forming software, the finite element model for power spinning of plate blank was established, and the forming process of conical thin-wall spun parts with straight flange had been simulated. The flatness error via least square method was taken as the evaluation index of flange flatness. In addition, the single factor design was used. The influence of the process parameters, including mandrel rotational velocity, roller feed velocity, roller nose radius and roller mounting angle on the flange flatness of conical thin-wall spun parts was obtained. The results indicated that flange flatness is improved with the increasing of mandrel rotational velocity, however, the effect of the mandrel rotational velocity increasing up to a certain value on the flange flatness was slightt. When roller feed velocity increased, the flange flatness was deteriorated. The roller nose radius and roller mounting angle had a compliex effect on the flange flatness, in other words, the flange flatness was first improved and then deteriorated when the roller nose radius or roller mounting angle increased. The further computer simulation with appropriate process parameters based on the obtained simulation results was conducted, which showed the flange had a minimum flatness error comparing with the other simulated.
2017, 36(7): 1073-1078.
doi: 10.13433/j.cnki.1003-8728.2017.0715
Abstract:
In order to realize efficiency and ductile machining of tungsten carbide (WC), the model for critical depth of cutting for brittleness-ductility transition of WC in ultrasonic elliptical vibration cutting (UEVC) was established, considering the critical load for generating crack on the surface of hard brittle materials and the principal cutting force for WC in UEVC. The effects of the cutting speed, tool radius, elliptical vibration frequency, amplitude, hardness and fracture toughness of WC on the critical depth of cutting were analyzed with the theoretical formulae. Based on the imitation cutting scribing experiment, the influence of the cutting speed, hardness and fracture toughness of WC on the critical depth of cutting was investigated. It is understood that the critical depth of cutting in UEVC can be increased as comparing with the conventional cutting (CC) and the processing efficiency can be improved under the premise of improving the surface quality and accuracy.
In order to realize efficiency and ductile machining of tungsten carbide (WC), the model for critical depth of cutting for brittleness-ductility transition of WC in ultrasonic elliptical vibration cutting (UEVC) was established, considering the critical load for generating crack on the surface of hard brittle materials and the principal cutting force for WC in UEVC. The effects of the cutting speed, tool radius, elliptical vibration frequency, amplitude, hardness and fracture toughness of WC on the critical depth of cutting were analyzed with the theoretical formulae. Based on the imitation cutting scribing experiment, the influence of the cutting speed, hardness and fracture toughness of WC on the critical depth of cutting was investigated. It is understood that the critical depth of cutting in UEVC can be increased as comparing with the conventional cutting (CC) and the processing efficiency can be improved under the premise of improving the surface quality and accuracy.
2017, 36(7): 1079-1084.
doi: 10.13433/j.cnki.1003-8728.2017.0716
Abstract:
In order to effectively eliminate the core void and improve the mechanical properties of CWR shaft, a new method with high-pressure gas to compact CWR shaft core void, briefly called floating-pressure method, is put forward. The mechanism of void closure and the influence law of the processing parameters is investigated with DEFORM-3D. The results show the condition of core void closure is that the high-temperature shaft should be subjected via three directional compressive stress, negative mean stress and large shear stress; the higher the gas pressure or the shaft temperature is, the more quickly the void close, but there is the slight effect on the shafts' shape and size.
In order to effectively eliminate the core void and improve the mechanical properties of CWR shaft, a new method with high-pressure gas to compact CWR shaft core void, briefly called floating-pressure method, is put forward. The mechanism of void closure and the influence law of the processing parameters is investigated with DEFORM-3D. The results show the condition of core void closure is that the high-temperature shaft should be subjected via three directional compressive stress, negative mean stress and large shear stress; the higher the gas pressure or the shaft temperature is, the more quickly the void close, but there is the slight effect on the shafts' shape and size.
Research and Realization of Automatic Verification System for Controllable Ultrasonic Fault Detector
2017, 36(7): 1085-1091.
doi: 10.13433/j.cnki.1003-8728.2017.0717
Abstract:
On the basis of analyzing the current manual verification method, the automatic verification method of ultrasonic flaw detector with remote control interface is studied, and the automatic verification system is designed and developed. With the extensible markup language (XML), equipment remote control instruction set and data analytical method library are established, which can solve the problems of the extension design of the instrument interface and protocol diversification; with signal generator and a programmable attenuator cascade, controlled attenuator used in metrology is designed, the high accuracy controllable attenuator bottleneck is broken through effectively, and the problems of large attenuation range, small attenuation step and high attenuation accuracy are all solved. For the verification of the scanning range parameters of the ultrasonic flaw detector, the calculation method is proposed to replace the traditional counting method, and the verification process is realized.
On the basis of analyzing the current manual verification method, the automatic verification method of ultrasonic flaw detector with remote control interface is studied, and the automatic verification system is designed and developed. With the extensible markup language (XML), equipment remote control instruction set and data analytical method library are established, which can solve the problems of the extension design of the instrument interface and protocol diversification; with signal generator and a programmable attenuator cascade, controlled attenuator used in metrology is designed, the high accuracy controllable attenuator bottleneck is broken through effectively, and the problems of large attenuation range, small attenuation step and high attenuation accuracy are all solved. For the verification of the scanning range parameters of the ultrasonic flaw detector, the calculation method is proposed to replace the traditional counting method, and the verification process is realized.
2017, 36(7): 1092-1098.
doi: 10.13433/j.cnki.1003-8728.2017.0718
Abstract:
It is difficult to predict the characteristics of the flow fields between the jet pipe nozzle and the receiver as there exists a complex turbulent flow like submerged jet. Under the condition that the nozzle is rectangular and that the receiving ports are circular and rectangular respectively, the flow fields are numerically simulated. Then the influence factors of nozzle displacement, overlap areas of the nozzle and the receiving ports, the inlet pressure and load of a jet pipe on the flow rate during the pilot stage are obtained. The simulation results and their comparison show that the flow rate during the pilot stage is proportional to the pressure difference between the inlet and outlet of the jet pipe and that variables such as nozzle displacement, overlap area of the nozzle and the receiving ports and the load have little influence on the flow rate during the pilot stage. The equivalent hydraulic bridge road of the jet pipe flow field is established. The nonlinear equations of the flow rate are deduced. The influence factors of the flow rate are analyzed with the Taylor expansion. The concept of acceptance rate of flow rate is put forward and its influence on the pilot stage is analyzed.
It is difficult to predict the characteristics of the flow fields between the jet pipe nozzle and the receiver as there exists a complex turbulent flow like submerged jet. Under the condition that the nozzle is rectangular and that the receiving ports are circular and rectangular respectively, the flow fields are numerically simulated. Then the influence factors of nozzle displacement, overlap areas of the nozzle and the receiving ports, the inlet pressure and load of a jet pipe on the flow rate during the pilot stage are obtained. The simulation results and their comparison show that the flow rate during the pilot stage is proportional to the pressure difference between the inlet and outlet of the jet pipe and that variables such as nozzle displacement, overlap area of the nozzle and the receiving ports and the load have little influence on the flow rate during the pilot stage. The equivalent hydraulic bridge road of the jet pipe flow field is established. The nonlinear equations of the flow rate are deduced. The influence factors of the flow rate are analyzed with the Taylor expansion. The concept of acceptance rate of flow rate is put forward and its influence on the pilot stage is analyzed.
2017, 36(7): 1099-1104.
doi: 10.13433/j.cnki.1003-8728.2017.0719
Abstract:
In order to meet the need of accuracy and real-time in long distance obstacle detection of tower crane warning system, a new least mean square adaptive time delay estimation(LMSTDE) in ultrasonic echo time delay estimation is proposed, which is based on discrete particle swarm optimization(DPSO) algorithm. The method can reduce computation amount greatly with DPOS and overcome immature constringency in the optimization algorithm with variable step-size LMS and variable acceleration coefficients. The experimental results show that:this method not only keeps the high accuracy and good anti-noise ability of the original algorithm, but also increases the computation speed by 25 times. It can be used in the real time detection of middle and long distance obstacles with higher reliability.
In order to meet the need of accuracy and real-time in long distance obstacle detection of tower crane warning system, a new least mean square adaptive time delay estimation(LMSTDE) in ultrasonic echo time delay estimation is proposed, which is based on discrete particle swarm optimization(DPSO) algorithm. The method can reduce computation amount greatly with DPOS and overcome immature constringency in the optimization algorithm with variable step-size LMS and variable acceleration coefficients. The experimental results show that:this method not only keeps the high accuracy and good anti-noise ability of the original algorithm, but also increases the computation speed by 25 times. It can be used in the real time detection of middle and long distance obstacles with higher reliability.
2017, 36(7): 1105-1110.
doi: 10.13433/j.cnki.1003-8728.2017.0720
Abstract:
Complex more-bending thin-wall tube is difficult to ensure bended position and shape precision, so it is difficult to adapt to an assemblage part. The forming difficulty in the more-bending thin-wall thin-length copper tube is analyzed, and the scheme of step to step bending formore-bending copper tube by using point to plane and plane to space is presented. The single bending problems are solved by process optimization. The bending forming and precision control tool are designed, that the bending forming problem with high efficiency and quality on more-bending thin-wall copper tube is solved. The comparison showed that the scheme of step to step bending was better than the scheme of U-shaped welding forming.
Complex more-bending thin-wall tube is difficult to ensure bended position and shape precision, so it is difficult to adapt to an assemblage part. The forming difficulty in the more-bending thin-wall thin-length copper tube is analyzed, and the scheme of step to step bending formore-bending copper tube by using point to plane and plane to space is presented. The single bending problems are solved by process optimization. The bending forming and precision control tool are designed, that the bending forming problem with high efficiency and quality on more-bending thin-wall copper tube is solved. The comparison showed that the scheme of step to step bending was better than the scheme of U-shaped welding forming.
2017, 36(7): 1111-1115.
doi: 10.13433/j.cnki.1003-8728.2017.0721
Abstract:
The influence of the weld seam parameters on the formability of tailor welded blanks (TWBs) with same material and different gage under different base material thickness ratio as well as different material and same gage under different strength ratio was studied with numerical simulation techniques combining with the dome test, and to determine the thickness ratio and strength ratio of weld seam as the major effecting factor on formability of TWBs. The results show that the influence of the weld seam on the formability of TWBs has a matching scope of the base. At the thickness ratio or strength ratio of base below 1.3, the weld seam is the major effecting factor on formability of TWBs, and which will improve the property of weld seam so as to enhance the formability of TWBs. At the thickness ratio or strength ratio of base above 1.3, the deviation level of base is the major effecting factor on the formability of TWBs, and which will be reasonable for combining the base with the processing optimization of TWBs.
The influence of the weld seam parameters on the formability of tailor welded blanks (TWBs) with same material and different gage under different base material thickness ratio as well as different material and same gage under different strength ratio was studied with numerical simulation techniques combining with the dome test, and to determine the thickness ratio and strength ratio of weld seam as the major effecting factor on formability of TWBs. The results show that the influence of the weld seam on the formability of TWBs has a matching scope of the base. At the thickness ratio or strength ratio of base below 1.3, the weld seam is the major effecting factor on formability of TWBs, and which will improve the property of weld seam so as to enhance the formability of TWBs. At the thickness ratio or strength ratio of base above 1.3, the deviation level of base is the major effecting factor on the formability of TWBs, and which will be reasonable for combining the base with the processing optimization of TWBs.
2017, 36(7): 1116-1123.
doi: 10.13433/j.cnki.1003-8728.2017.0722
Abstract:
An Optimization method for processing parameters is presented, which is a comprehensive applying for experimental design, response surface method and multi-objective optimization. Taking the forming efficiency and the yield strength as the optimization indexes, aging temperature, aging time and stress as the optimization variables, the experiments are conducted according to Box-Behnken design principle. Then the response surface models are constructed based on the experimental results, and the multi-objective optimization model is further established. The Dynamic weighted aggregation based on the quantum-behaved particle swarm optimization algorithm is introduced to provide the designer with a set of Pareto optimal solutions, a minimum normalized distance method has been presented to select the optimal solution and the corresponding processing parameters (187.9℃, 6.42 h, 250 MPa) are the comprehensive optimal parameters. Tension of creep aging have been carried out with the parameters pre-and post-optimization, the results show that the forming efficiency increase from 14.0% to 19.4% and the yield strength increase from 442.354 MPa to 451.786 MPa, which prove the present processing parameter optimization method for creep aging forming is effective.
An Optimization method for processing parameters is presented, which is a comprehensive applying for experimental design, response surface method and multi-objective optimization. Taking the forming efficiency and the yield strength as the optimization indexes, aging temperature, aging time and stress as the optimization variables, the experiments are conducted according to Box-Behnken design principle. Then the response surface models are constructed based on the experimental results, and the multi-objective optimization model is further established. The Dynamic weighted aggregation based on the quantum-behaved particle swarm optimization algorithm is introduced to provide the designer with a set of Pareto optimal solutions, a minimum normalized distance method has been presented to select the optimal solution and the corresponding processing parameters (187.9℃, 6.42 h, 250 MPa) are the comprehensive optimal parameters. Tension of creep aging have been carried out with the parameters pre-and post-optimization, the results show that the forming efficiency increase from 14.0% to 19.4% and the yield strength increase from 442.354 MPa to 451.786 MPa, which prove the present processing parameter optimization method for creep aging forming is effective.
2017, 36(7): 1124-1130.
doi: 10.13433/j.cnki.1003-8728.2017.0723
Abstract:
The equivalent 8-SPU mobile robot acts as a leg type robot while walking and a parallel robot while supporting. Inverse position solution, kinematics mapping model, and comprehensive constraints with combining geometric constrains and kinetic property constraints are suggested for the workspace analysis of this mechanism. The polar coordinate boundary searching method is used to determine the workspace boundary, and then the 3D solid model of fixed pose workspace and its cross-sectional drawing are also given. The effect of mechanism parameters on workspace volume size and connectivity is also intensively analyzed. Moreover, the workspace is analyzed from manipulability and uniformity, and compared under two different constraint conditions. The analysis results demonstrate that the workspace under the comprehensive constraints has better motion performance. The robot workspace analysis in this study provides a theoretical basis for its structural optimization, motion control and path planning.
The equivalent 8-SPU mobile robot acts as a leg type robot while walking and a parallel robot while supporting. Inverse position solution, kinematics mapping model, and comprehensive constraints with combining geometric constrains and kinetic property constraints are suggested for the workspace analysis of this mechanism. The polar coordinate boundary searching method is used to determine the workspace boundary, and then the 3D solid model of fixed pose workspace and its cross-sectional drawing are also given. The effect of mechanism parameters on workspace volume size and connectivity is also intensively analyzed. Moreover, the workspace is analyzed from manipulability and uniformity, and compared under two different constraint conditions. The analysis results demonstrate that the workspace under the comprehensive constraints has better motion performance. The robot workspace analysis in this study provides a theoretical basis for its structural optimization, motion control and path planning.
2017, 36(7): 1131-1135.
doi: 10.13433/j.cnki.1003-8728.2017.0724
Abstract:
Based on the property of double-helical gear driver and the principle of the face gear driver, the method for constructing the double-helical tooth of the face gear was presented; in order to obtain local bearing contact for teeth with different screw directions, longitudinal tooth modification was applied to realize shifting contact path. Then, for the sake of using the maximum tooth width of the face gear with double-helical pinion, the manufacturing method and the cutter for the herringbone tooth of the face gear were designed. Third, the generation principle for the herringbone tooth of the face gear without tool withdrawal groove was elaborated; and the applied coordinate system, tooth surface mathematical model of the herringbone tooth of the face gear, simulation model of the tooth surface contact performance were established to make the face gear have the maximum tooth width. Finally, the calculation result of the herringbone tooth surface of the face gear was given and the virtual prototype was drawn, and the tooth surface contact analysis was completed. The result demonstrates that the double-helical face gear driver has desired meshing performance, which could meets the needs of the meshing transmission.
Based on the property of double-helical gear driver and the principle of the face gear driver, the method for constructing the double-helical tooth of the face gear was presented; in order to obtain local bearing contact for teeth with different screw directions, longitudinal tooth modification was applied to realize shifting contact path. Then, for the sake of using the maximum tooth width of the face gear with double-helical pinion, the manufacturing method and the cutter for the herringbone tooth of the face gear were designed. Third, the generation principle for the herringbone tooth of the face gear without tool withdrawal groove was elaborated; and the applied coordinate system, tooth surface mathematical model of the herringbone tooth of the face gear, simulation model of the tooth surface contact performance were established to make the face gear have the maximum tooth width. Finally, the calculation result of the herringbone tooth surface of the face gear was given and the virtual prototype was drawn, and the tooth surface contact analysis was completed. The result demonstrates that the double-helical face gear driver has desired meshing performance, which could meets the needs of the meshing transmission.
2017, 36(7): 1136-1142.
doi: 10.13433/j.cnki.1003-8728.2017.0725
Abstract:
It is difficult to theoretically calculate lift of flapping wing flight as the aerodynamic feature of flapping wing is more complex than fixed wing flight. Based on the basic aerodynamic characteristics of an object flowed around by air, the total lift of flapping wing flight was divided into lift of flow around wing(LFAW) and lift of flow dragging wing(LFDW) in this paper. The acting mechanism and change rule of LFAW and LFDW in flapping wing flight were further analyzed and illustrated. After establishing motion model of flapping wing, theoretical calculating models of maximum LFAW and LFDW were further given. Case study shows that not only the classified lift method was feasible, but the proportion of LFAW and LFDW during fly test was consistent with the change rule of actual animal flight.
It is difficult to theoretically calculate lift of flapping wing flight as the aerodynamic feature of flapping wing is more complex than fixed wing flight. Based on the basic aerodynamic characteristics of an object flowed around by air, the total lift of flapping wing flight was divided into lift of flow around wing(LFAW) and lift of flow dragging wing(LFDW) in this paper. The acting mechanism and change rule of LFAW and LFDW in flapping wing flight were further analyzed and illustrated. After establishing motion model of flapping wing, theoretical calculating models of maximum LFAW and LFDW were further given. Case study shows that not only the classified lift method was feasible, but the proportion of LFAW and LFDW during fly test was consistent with the change rule of actual animal flight.
2017, 36(7): 1143-1148.
doi: 10.13433/j.cnki.1003-8728.2017.0726
Abstract:
A Bayesian approach based crack propagation curve predicting method under random load spectrum with Walker model was presented. At first, parameters C and n in Walker model were viewed as random variables and their joint posterior distribution was constructed based on Bayes' theorem using test data under random spectrum. Then, samples of C, n were generated from their joint posterior distribution using Markov Chain Monte Carlo (MCMC) sampling method in which crack growth analysis under random spectrum was embedded ingeniously. At last, mean values of posterior distribution of C, n were substituted into Walker model to predict crack propagation curve (a-N curve) whose initial size has been known under random spectrum. The presented method was identified using crack growth test data of Aluminum alloy 7050-T7651 and 7050-T7452 under random spectrum, it was found that a-N curve predicted based on the method agrees well with tested a-N curve even only using a few of test data. Hence, it's promising that this method would bring great value in engineering application for achieving future damage predicting accurately in structural health monitoring (SHM) system.
A Bayesian approach based crack propagation curve predicting method under random load spectrum with Walker model was presented. At first, parameters C and n in Walker model were viewed as random variables and their joint posterior distribution was constructed based on Bayes' theorem using test data under random spectrum. Then, samples of C, n were generated from their joint posterior distribution using Markov Chain Monte Carlo (MCMC) sampling method in which crack growth analysis under random spectrum was embedded ingeniously. At last, mean values of posterior distribution of C, n were substituted into Walker model to predict crack propagation curve (a-N curve) whose initial size has been known under random spectrum. The presented method was identified using crack growth test data of Aluminum alloy 7050-T7651 and 7050-T7452 under random spectrum, it was found that a-N curve predicted based on the method agrees well with tested a-N curve even only using a few of test data. Hence, it's promising that this method would bring great value in engineering application for achieving future damage predicting accurately in structural health monitoring (SHM) system.
