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RSS2016 Vol. 35, No. 1
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2016, 35(1): 1-9.
doi: 10.13433/j.cnki.1003-8728.2016.0101
PDF 1327KB
Abstract:
The paper roughly summarized the research status ofadiabatic shear band in dynamic deformation. From four aspects of the mechanism of adiabatic shear and instabilitycriterion, microscopic texture of adiabatic shear band,experiment techniques and numerical simulation research,the current study and development are summarized and compared. The paper considered that the thermo visco plastic constitutive model should consider the change of microstructure and the state of stress, then it can effectively analyze the impact onmacroscopic deformation localized by the change of microstructure. Secondly, the insufficient sections still exist in the aspect of microscopic texture and microstructure change, the evolution process of the microscopic texture in adiabatic shear band have not been definited, the influence factors which considered in the numerical simulationtechniques are also not comprehensive enough. At last, the paper put forward the own views of the trend on adiabatic shear band.
The paper roughly summarized the research status ofadiabatic shear band in dynamic deformation. From four aspects of the mechanism of adiabatic shear and instabilitycriterion, microscopic texture of adiabatic shear band,experiment techniques and numerical simulation research,the current study and development are summarized and compared. The paper considered that the thermo visco plastic constitutive model should consider the change of microstructure and the state of stress, then it can effectively analyze the impact onmacroscopic deformation localized by the change of microstructure. Secondly, the insufficient sections still exist in the aspect of microscopic texture and microstructure change, the evolution process of the microscopic texture in adiabatic shear band have not been definited, the influence factors which considered in the numerical simulationtechniques are also not comprehensive enough. At last, the paper put forward the own views of the trend on adiabatic shear band.
2016, 35(1): 10-16.
doi: 10.13433/j.cnki.1003-8728.2016.0102
Abstract:
According to the cutting principle of spiral bevel gear, the tooth surface equation of spiral bevel gear is established. Put the equation of two contact gear faces in the same coordinate system, the positions of contact points could be obtained according to the space geometry theory. The principle curvatures of the contact points and the tooth surface relative velocity could be got using differential geometry theory. The geometric model is established by using MATLAB program and PRO/E. Using ABAQUS, the normal contact force could be got by the simulation results. Based on Dowson-Higginson equation, this article calculated and analyzed the minimum film thickness in the condition of different meshing velocity and discussed the most dangerous area during meshing process according to the minimum film thickness of spiral bevel gear.
According to the cutting principle of spiral bevel gear, the tooth surface equation of spiral bevel gear is established. Put the equation of two contact gear faces in the same coordinate system, the positions of contact points could be obtained according to the space geometry theory. The principle curvatures of the contact points and the tooth surface relative velocity could be got using differential geometry theory. The geometric model is established by using MATLAB program and PRO/E. Using ABAQUS, the normal contact force could be got by the simulation results. Based on Dowson-Higginson equation, this article calculated and analyzed the minimum film thickness in the condition of different meshing velocity and discussed the most dangerous area during meshing process according to the minimum film thickness of spiral bevel gear.
2016, 35(1): 17-22.
doi: 10.13433/j.cnki.1003-8728.2016.0103
Abstract:
In order to verify the limit load of blade in its design life can meet the design requirements, the test system of full-scale static loading for wind turbine blade ultimate load testing is designed. The traction force of each node is optimized to get bigger reasonable traction force, and moment calculation software is designed to verify that he bending moment static loading process is matched. Based on the distributed multi-networks control structure, The dynamic master-slave proportion-integral differential(PID) control algorithm is designed to coordinate static loading during traction coupling, and to realize five nodes full-scale static loading test for the fan blade. which meet the reqiurements of static loading test. Field experiments shows that the control strategy of loading system is effective, the maximum traction force error of loading point is about ±5%, the deflection error of measuring points were less than ±7%, the traction coupling during static loading process is reduced and good control effect is achieved.
In order to verify the limit load of blade in its design life can meet the design requirements, the test system of full-scale static loading for wind turbine blade ultimate load testing is designed. The traction force of each node is optimized to get bigger reasonable traction force, and moment calculation software is designed to verify that he bending moment static loading process is matched. Based on the distributed multi-networks control structure, The dynamic master-slave proportion-integral differential(PID) control algorithm is designed to coordinate static loading during traction coupling, and to realize five nodes full-scale static loading test for the fan blade. which meet the reqiurements of static loading test. Field experiments shows that the control strategy of loading system is effective, the maximum traction force error of loading point is about ±5%, the deflection error of measuring points were less than ±7%, the traction coupling during static loading process is reduced and good control effect is achieved.
2016, 35(1): 23-28.
doi: 10.13433/j.cnki.1003-8728.2016.0104
Abstract:
This paper is devoted to the nonlinear characteristics of a rotor bearing system with squeeze film damper(SFD). Non-linear jumps of the rotor system and the related factors such as static eccentricity are investigated. The experimental results show that high unbalance levels excite non-linear jump phenomena. However, increasing the rotation acceleration or reducing the oil temperature has positive effect on the inhibition of the jump phenomena. Improvement of alignment upgrades the vibration attenuation of the SFD. And the non-linear jump could also be eliminated by decreasing the static eccentricity of the SFD. The gravity should be concerned in the SFD design process to decrease the static eccentricity.
This paper is devoted to the nonlinear characteristics of a rotor bearing system with squeeze film damper(SFD). Non-linear jumps of the rotor system and the related factors such as static eccentricity are investigated. The experimental results show that high unbalance levels excite non-linear jump phenomena. However, increasing the rotation acceleration or reducing the oil temperature has positive effect on the inhibition of the jump phenomena. Improvement of alignment upgrades the vibration attenuation of the SFD. And the non-linear jump could also be eliminated by decreasing the static eccentricity of the SFD. The gravity should be concerned in the SFD design process to decrease the static eccentricity.
2016, 35(1): 29-34.
doi: 10.13433/j.cnki.1003-8728.2016.0105
Abstract:
In order to raise the energy efficiency of a hydraulic excavator, we propose a slewing energy recovery system that uses an energy accumulator. The mathematical model of the energy recovery system is built, and its simulation is conducted. Through a number of computer simulations, we analyzes whether the energy recycle precept is proper, the influence of parameters of the energy accumulator on energy recovery ratio and how the added energy recovery system affects the control performance of the energy recovery system. The simulation results demonstrate that the energy recovery system can indeed raise the energy recovery and recycle ratio to 41.99%, while its great control performance is maintained. Finally, its practicability and the correction of the simulation results were tested and verified through experiments on sample machines.
In order to raise the energy efficiency of a hydraulic excavator, we propose a slewing energy recovery system that uses an energy accumulator. The mathematical model of the energy recovery system is built, and its simulation is conducted. Through a number of computer simulations, we analyzes whether the energy recycle precept is proper, the influence of parameters of the energy accumulator on energy recovery ratio and how the added energy recovery system affects the control performance of the energy recovery system. The simulation results demonstrate that the energy recovery system can indeed raise the energy recovery and recycle ratio to 41.99%, while its great control performance is maintained. Finally, its practicability and the correction of the simulation results were tested and verified through experiments on sample machines.
2016, 35(1): 35-39.
doi: 10.13433/j.cnki.1003-8728.2016.0106
Abstract:
In order to accurately identify the modal model based on inconsistent frequency response functions(FRFs), a new local solving method for modal parameters estimation in the least square complex frequency(LSCF) domain is proposed. Taking a light mass plate as an example, considering the inconsistent FRFs caused by the added mass of transducers, we estimate the modal based on LSCF utilizing the global solving method and local solving method, respectively. The comparison of results show that the natural frequencies obtained by the local solving method have smaller errors than these of the standard test, and the modal shapes are consistent with the theoretical ones. It demonstrates that the local solving method based on LSCF can accurately identify the modal model based on inconsistent FRFs.
In order to accurately identify the modal model based on inconsistent frequency response functions(FRFs), a new local solving method for modal parameters estimation in the least square complex frequency(LSCF) domain is proposed. Taking a light mass plate as an example, considering the inconsistent FRFs caused by the added mass of transducers, we estimate the modal based on LSCF utilizing the global solving method and local solving method, respectively. The comparison of results show that the natural frequencies obtained by the local solving method have smaller errors than these of the standard test, and the modal shapes are consistent with the theoretical ones. It demonstrates that the local solving method based on LSCF can accurately identify the modal model based on inconsistent FRFs.
2016, 35(1): 40-43.
doi: 10.13433/j.cnki.1003-8728.2016.0107
Abstract:
In order to solve the problem of accurate and efficient measurement of the effective fire area of the flash hole in bulk, an automatic measurement method for the effective area of the flash hole with machine vision technology and image processing technique is proposed. The measurement system was set up with industrial Complementary Metal Oxide Semiconductor(CMOS) camera, optical lens groups, backlight source and computer etc, combining with special image processing software and the measurement of effective fire area of the flash hole was realized. The calibration tests show that the system measurement error is about 5‰ and the ultimate size of the calibration has a small floating range, it can meet the measurement accuracy requirements of the cartridge flash hole. Practical application results show that the system measurement precision can meet the design requirements, and the measuring efficiency reaches 20 pieces per minute.
In order to solve the problem of accurate and efficient measurement of the effective fire area of the flash hole in bulk, an automatic measurement method for the effective area of the flash hole with machine vision technology and image processing technique is proposed. The measurement system was set up with industrial Complementary Metal Oxide Semiconductor(CMOS) camera, optical lens groups, backlight source and computer etc, combining with special image processing software and the measurement of effective fire area of the flash hole was realized. The calibration tests show that the system measurement error is about 5‰ and the ultimate size of the calibration has a small floating range, it can meet the measurement accuracy requirements of the cartridge flash hole. Practical application results show that the system measurement precision can meet the design requirements, and the measuring efficiency reaches 20 pieces per minute.
2016, 35(1): 44-49.
doi: 10.13433/j.cnki.1003-8728.2016.0108
Abstract:
To deals with the problem of ensuring accuracy of the assembly processing, a forecasting model of assembly deviation propagation is proposed. The deviation characteristics that affect the assembly accuracy of a four axis horizontal precision machining center are analyzed. Based on the small displacement spin theory, the mathematical model of typical deviation characteristics is established. Based on the series assembly relation, the mathematical model of assembly deviation transfer is established to predict assembly accuracy of the end. The effectiveness of the proposed approach was verified by measurement experiments.
To deals with the problem of ensuring accuracy of the assembly processing, a forecasting model of assembly deviation propagation is proposed. The deviation characteristics that affect the assembly accuracy of a four axis horizontal precision machining center are analyzed. Based on the small displacement spin theory, the mathematical model of typical deviation characteristics is established. Based on the series assembly relation, the mathematical model of assembly deviation transfer is established to predict assembly accuracy of the end. The effectiveness of the proposed approach was verified by measurement experiments.
2016, 35(1): 50-55.
doi: 10.13433/j.cnki.1003-8728.2016.0109
Abstract:
In order to improve the vibration characteristics of spiral bevel gears, the stiffness excitation was calculated using the results of loaded tooth contact analysis. The corner impact excitation was approximately obtained by the tooth contact analysis, loaded share curve and the impact model of gear pair. The three-dimensional eight-degree dynamical model of the spiral bevel gears was established with the concentrated parameter method. The dynamic equations of this system were established, and the identical dimensionless equations were deduced though the methods of eliminating relative displacement and identical dimensionless. The dynamic equations were solved by the fourth-order Runge-Kutta algorithm with variable step lengths and the dynamic behaviors of spiral bevel gears drive were studied. Also,the influence of transmission error and design contact ratio on the system vibration were investigated, and the results show that:an increase of vibration of gear pair as the increase of transmission error; the decrease of vibration of gear pair while the increase of design contact ratio.
In order to improve the vibration characteristics of spiral bevel gears, the stiffness excitation was calculated using the results of loaded tooth contact analysis. The corner impact excitation was approximately obtained by the tooth contact analysis, loaded share curve and the impact model of gear pair. The three-dimensional eight-degree dynamical model of the spiral bevel gears was established with the concentrated parameter method. The dynamic equations of this system were established, and the identical dimensionless equations were deduced though the methods of eliminating relative displacement and identical dimensionless. The dynamic equations were solved by the fourth-order Runge-Kutta algorithm with variable step lengths and the dynamic behaviors of spiral bevel gears drive were studied. Also,the influence of transmission error and design contact ratio on the system vibration were investigated, and the results show that:an increase of vibration of gear pair as the increase of transmission error; the decrease of vibration of gear pair while the increase of design contact ratio.
2016, 35(1): 56-62.
doi: 10.13433/j.cnki.1003-8728.2016.0110
Abstract:
This paper presents the structural design of a new hybrid surgical robotic manipulator for laparoscopic surgery. The proposed surgical robot which can provide multi degrees of freedom is combined by two decoupled parallel mechanisms. The kinematic model of the whole robot is presented by means of superposition. Motion planning based on laparoscopic surgery is built to reduce the number of structural inputs. The Jacobian matrix of the operation point is also solved by using the mapping principle of the surgical instrument. The best configuration of the robot in preoperative localization is presented on the basis of Jacobian condition number. "Dexterity-Space" index is established to optimize the workspace of the operation point. The result indicates that the robotic manipulator provides better dexterity and fits the need of laparoscopic surgery operation.
This paper presents the structural design of a new hybrid surgical robotic manipulator for laparoscopic surgery. The proposed surgical robot which can provide multi degrees of freedom is combined by two decoupled parallel mechanisms. The kinematic model of the whole robot is presented by means of superposition. Motion planning based on laparoscopic surgery is built to reduce the number of structural inputs. The Jacobian matrix of the operation point is also solved by using the mapping principle of the surgical instrument. The best configuration of the robot in preoperative localization is presented on the basis of Jacobian condition number. "Dexterity-Space" index is established to optimize the workspace of the operation point. The result indicates that the robotic manipulator provides better dexterity and fits the need of laparoscopic surgery operation.
2016, 35(1): 63-66.
doi: 10.13433/j.cnki.1003-8728.2016.0111
Abstract:
The pendulum is the most important part of the high impact shock testing machine with middleweight, whose quality will determine the whole experiment. The pendulum also determines the service time of the test machine. So it is imperative to optimize the pendulum of the test machine. The pendulum of the impact test machine is simplified, and some typical parameters are obtained. Taking the impluse of the rotation shaft as the object, the relationship between typical parameters and the impulse of the rotation shaft can be deduced. With the calculated data with MATLAB software, the optimal design of the pendulum is performed to minimize the shaft wear. thus the reliability and service life of the pendulum will be improved.
The pendulum is the most important part of the high impact shock testing machine with middleweight, whose quality will determine the whole experiment. The pendulum also determines the service time of the test machine. So it is imperative to optimize the pendulum of the test machine. The pendulum of the impact test machine is simplified, and some typical parameters are obtained. Taking the impluse of the rotation shaft as the object, the relationship between typical parameters and the impulse of the rotation shaft can be deduced. With the calculated data with MATLAB software, the optimal design of the pendulum is performed to minimize the shaft wear. thus the reliability and service life of the pendulum will be improved.
2016, 35(1): 67-72.
doi: 10.13433/j.cnki.1003-8728.2016.0112
Abstract:
In order to implement the dynamics characteristic of dual power-split transmission, a dynamic mechanics model is built. First, according to the methods of the tooth contact analysis(TCA) and loaded tooth contact analysis(LTCA), the actual meshing process of each gear pair is simulated, and the time-varying mesh stiffness excitation are obtained, which can improve the numerical precision. Next, by using the lumped mass method, the bending-torsion coupling three-dimensional dynamical model of the dual power-split transmission is established. Then, by the method of fourth order Runge-Kutta algorithm with variable step lengths, the responses of this system in frequency domain and time domain are obtained, and the dynamic load change characteristics of each gear pairs are analyzed. The results show that the establishment, solution and analysis of the system dynamics model could provide a basis for the dynamic design, and have an important significance for the dynamic efficiency analysis and dynamic performance optimization design of the dual power-split transmission.
In order to implement the dynamics characteristic of dual power-split transmission, a dynamic mechanics model is built. First, according to the methods of the tooth contact analysis(TCA) and loaded tooth contact analysis(LTCA), the actual meshing process of each gear pair is simulated, and the time-varying mesh stiffness excitation are obtained, which can improve the numerical precision. Next, by using the lumped mass method, the bending-torsion coupling three-dimensional dynamical model of the dual power-split transmission is established. Then, by the method of fourth order Runge-Kutta algorithm with variable step lengths, the responses of this system in frequency domain and time domain are obtained, and the dynamic load change characteristics of each gear pairs are analyzed. The results show that the establishment, solution and analysis of the system dynamics model could provide a basis for the dynamic design, and have an important significance for the dynamic efficiency analysis and dynamic performance optimization design of the dual power-split transmission.
2016, 35(1): 73-79.
doi: 10.13433/j.cnki.1003-8728.2016.0113
Abstract:
The dynamic characteristics is analyzed with the motion and force characteristics of a hydraulic excavator's working device's mechanical arm. The dynamic differential equations of the hydraulic excavator's mechanical arm are established with the equivalent finite element method based on concentrated mass and inertia. The derivation and numerical solution are conducted for the differential equations of motion with the Runge-Kutta numerical solution method. The dynamic characteristics are analyzed for each arm. The virtual prototype model of the hydraulic excavator's working device is established with the dynamics simulation software Adams. The simulation results are analyzed by selecting the same condition parameters with the numerical solution. By comparing the dynamic characteristic curve obtained with the simulation results and numerical solution, the results are basically consistent, which show that the dynamic modeling method of mechanical arm is correct.
The dynamic characteristics is analyzed with the motion and force characteristics of a hydraulic excavator's working device's mechanical arm. The dynamic differential equations of the hydraulic excavator's mechanical arm are established with the equivalent finite element method based on concentrated mass and inertia. The derivation and numerical solution are conducted for the differential equations of motion with the Runge-Kutta numerical solution method. The dynamic characteristics are analyzed for each arm. The virtual prototype model of the hydraulic excavator's working device is established with the dynamics simulation software Adams. The simulation results are analyzed by selecting the same condition parameters with the numerical solution. By comparing the dynamic characteristic curve obtained with the simulation results and numerical solution, the results are basically consistent, which show that the dynamic modeling method of mechanical arm is correct.
2016, 35(1): 80-84.
doi: 10.13433/j.cnki.1003-8728.2016.0114
Abstract:
The fault tree model of the CNC turret being not tight and stuck was developed with the failure modes of indexing process and the theory of FTA(fault tree analysis), also, the lasted failure data was collected. The probability fuzzy numbers were generated based on the fuzzy set theory, as it was difficult to gather the exact failure data for each event under uncertain situations, and the algorithms was given. The top event failure probability interval and the end event importance sorted were given on the quantitative analysis of the fuzzy fault tree. The results show that the Signal elements, re-positioning devices and Standard operation was the weakness for the reliability of CNC turret, which provides the basis of data analysis for improving reliability of CNC turret system.
The fault tree model of the CNC turret being not tight and stuck was developed with the failure modes of indexing process and the theory of FTA(fault tree analysis), also, the lasted failure data was collected. The probability fuzzy numbers were generated based on the fuzzy set theory, as it was difficult to gather the exact failure data for each event under uncertain situations, and the algorithms was given. The top event failure probability interval and the end event importance sorted were given on the quantitative analysis of the fuzzy fault tree. The results show that the Signal elements, re-positioning devices and Standard operation was the weakness for the reliability of CNC turret, which provides the basis of data analysis for improving reliability of CNC turret system.
2016, 35(1): 85-90.
doi: 10.13433/j.cnki.1003-8728.2016.0115
Abstract:
Data redundancy and improper rules for parts and components naming will happen when the mirror function in the CATIA system is used for the assembly design of symmetrical parts and components. In order to overcome the aforementioned disadvantages, a rapid assembly design method for symmetrical parts and components is proposed. In this method, parts and components with the same reference source are automatically identified. Instantiation of parts and components is carried out according to their categories. The rapid assembly design method is realized on the CATIA V5 system. The effectiveness of the method is verified by the rapid assembly design of an aircraft wing structural framework. Results indicate that the present method can improve the assembly efficiency of symmetrical parts and components, decrease the designers' workload, shorten the engineering product design cycle and reduce design cost.
Data redundancy and improper rules for parts and components naming will happen when the mirror function in the CATIA system is used for the assembly design of symmetrical parts and components. In order to overcome the aforementioned disadvantages, a rapid assembly design method for symmetrical parts and components is proposed. In this method, parts and components with the same reference source are automatically identified. Instantiation of parts and components is carried out according to their categories. The rapid assembly design method is realized on the CATIA V5 system. The effectiveness of the method is verified by the rapid assembly design of an aircraft wing structural framework. Results indicate that the present method can improve the assembly efficiency of symmetrical parts and components, decrease the designers' workload, shorten the engineering product design cycle and reduce design cost.
2016, 35(1): 91-97.
doi: 10.13433/j.cnki.1003-8728.2016.0116
Abstract:
This paper establishes the instantaneous model of cutting force of composite tool to realize controlling cutting force and provide the basis for inhibiting damage. The hole-machining process is divided into three processing operations:drilling, reaming and countersinking. The dynamic cutting force(thrust force and torque) models of the three processing operations are established based on the microscopic oblique cutting model. According to the cutting characteristics and states, we divide the hole-machining process into several stages. By studying the characteristics of each stage, the dynamic cutting force models of the three processing operations are employed to calculate the cutting force of the corresponding stage. Based on the actual rake angle model, the average value of rake angle is introduced then. We establish the expressions of average values of shear angle and friction angle as well as fiber orientation angle according to the respective relationships between distinct angles. A prediction model of the cutting force for the chisel edge is proposed with the theory of contact mechanics and the final instantaneous model of cutting force on hole-machining is well-established. Finally, several groups of experiments using the composite tool integrated with drilling, reaming and countersinking are carried out to verify the correctness and reliability of the model.
This paper establishes the instantaneous model of cutting force of composite tool to realize controlling cutting force and provide the basis for inhibiting damage. The hole-machining process is divided into three processing operations:drilling, reaming and countersinking. The dynamic cutting force(thrust force and torque) models of the three processing operations are established based on the microscopic oblique cutting model. According to the cutting characteristics and states, we divide the hole-machining process into several stages. By studying the characteristics of each stage, the dynamic cutting force models of the three processing operations are employed to calculate the cutting force of the corresponding stage. Based on the actual rake angle model, the average value of rake angle is introduced then. We establish the expressions of average values of shear angle and friction angle as well as fiber orientation angle according to the respective relationships between distinct angles. A prediction model of the cutting force for the chisel edge is proposed with the theory of contact mechanics and the final instantaneous model of cutting force on hole-machining is well-established. Finally, several groups of experiments using the composite tool integrated with drilling, reaming and countersinking are carried out to verify the correctness and reliability of the model.
2016, 35(1): 98-103.
doi: 10.13433/j.cnki.1003-8728.2016.0117
Abstract:
Aiming at the disc slitting process of sheet metal, the technique of plastic shearing oppression slitting is proposed to obtain a smoot and burr-free slitting surface. Based on the experiments of precision slitting, a 2D model is established with the DEFORM software. The plastic deformation of the galvanized sheet and the formation of the slitting surface morphology features are analyzed by the changes of the metallographic structure and hydrostatic stress in the process of slitting. The simulation results are in a good agreement with the experimental results. It is studied that the influence of the radial clearance and axial clearance between the two disc cutters on the burr-free slitting process. It can be proved that when the axial clearance is determined and the value of radial clearance is 20% of the sheet thickness, the best slitting surface can be getten. And the plastic shearing oppression slitting could only be used when the radial clearance is less than 2.5% of thickness. The axial clearance does not have an obvious influence on the slitting surface in a reasonable range.
Aiming at the disc slitting process of sheet metal, the technique of plastic shearing oppression slitting is proposed to obtain a smoot and burr-free slitting surface. Based on the experiments of precision slitting, a 2D model is established with the DEFORM software. The plastic deformation of the galvanized sheet and the formation of the slitting surface morphology features are analyzed by the changes of the metallographic structure and hydrostatic stress in the process of slitting. The simulation results are in a good agreement with the experimental results. It is studied that the influence of the radial clearance and axial clearance between the two disc cutters on the burr-free slitting process. It can be proved that when the axial clearance is determined and the value of radial clearance is 20% of the sheet thickness, the best slitting surface can be getten. And the plastic shearing oppression slitting could only be used when the radial clearance is less than 2.5% of thickness. The axial clearance does not have an obvious influence on the slitting surface in a reasonable range.
2016, 35(1): 104-108.
doi: 10.13433/j.cnki.1003-8728.2016.0118
Abstract:
To accurately describe the bathtub curve trend of complex products during the failure process, the intensity function bathtub curve model for multiple CNC machine tools is built, and its parameters are estimated through Maximum Likelihood Estimation, along with some numerical method. The hypothesis testing for trend based on TTT(Total Time on Test) is introduced and applied to test and verify the bathtub failure trend. Considering the reliability implication of two turning points of bathtub curve, we propose a method of determining the turning points on the basis of analyzing features of the cumulative mean time between failures. The model and method proposed in this paper are demonstrated to be effective in practical applications, through computing and analyzing failure data of three CNC grinding machines from field test.
To accurately describe the bathtub curve trend of complex products during the failure process, the intensity function bathtub curve model for multiple CNC machine tools is built, and its parameters are estimated through Maximum Likelihood Estimation, along with some numerical method. The hypothesis testing for trend based on TTT(Total Time on Test) is introduced and applied to test and verify the bathtub failure trend. Considering the reliability implication of two turning points of bathtub curve, we propose a method of determining the turning points on the basis of analyzing features of the cumulative mean time between failures. The model and method proposed in this paper are demonstrated to be effective in practical applications, through computing and analyzing failure data of three CNC grinding machines from field test.
2016, 35(1): 109-112.
doi: 10.13433/j.cnki.1003-8728.2016.0119
Abstract:
Analyzing the main features of the NC incremental forming and stretch forming, we investigate a hybrid of NC incremental forming with stretch forming based on the servo control system of NC incremental forming equipment so as to solve the heavy thinning and long time of the NC incremental forming. A new special fixture was developed to realize the hybrid forming on the original incremental forming equipment with one clamping system. The influences of the two methods on the thickness and forming time are analyzed. The results show that comparing with the normal incremental forming this hybrid forming technology can reduce the thinning and forming time series and form the parts that the normal incremental forming technology cannot form by breaking the forming limit angle of incremental forming.
Analyzing the main features of the NC incremental forming and stretch forming, we investigate a hybrid of NC incremental forming with stretch forming based on the servo control system of NC incremental forming equipment so as to solve the heavy thinning and long time of the NC incremental forming. A new special fixture was developed to realize the hybrid forming on the original incremental forming equipment with one clamping system. The influences of the two methods on the thickness and forming time are analyzed. The results show that comparing with the normal incremental forming this hybrid forming technology can reduce the thinning and forming time series and form the parts that the normal incremental forming technology cannot form by breaking the forming limit angle of incremental forming.
2016, 35(1): 113-117.
doi: 10.13433/j.cnki.1003-8728.2016.0120
Abstract:
A real-time monitoring system and corresponding software for optimizing the cutting parameters in CNC machining have been developed by using alternating-current motor driver. This system mainly consists of a computer, an alternating-current motor driver, a prime motor of machining and so on. First the related information including the materials of the work-piece and cutter, the type of machine tool, etc. is input into the computer for optimizing the cutting parameters and determining the reasonable fluctuation range of the motor's rotational speed, current and power. In cutting process, this system can acquire the current/voltage values of the prime motor in real-time for processing and analyzing. When the motor's rotational speed, current and power beyond the predetermined fluctuation range(e.g., tool damage occurrence, etc.); the controlling programs would give the control orders(e.g. pausing, etc.) to the alternating-current motor drive to stop the working of the prime motor. Therefore this system not only can optimize the selection of cutting parameters, and but also can real-time monitor the working currents, rotational speeds, and so on to guarantee a stable and reliable machining process.
A real-time monitoring system and corresponding software for optimizing the cutting parameters in CNC machining have been developed by using alternating-current motor driver. This system mainly consists of a computer, an alternating-current motor driver, a prime motor of machining and so on. First the related information including the materials of the work-piece and cutter, the type of machine tool, etc. is input into the computer for optimizing the cutting parameters and determining the reasonable fluctuation range of the motor's rotational speed, current and power. In cutting process, this system can acquire the current/voltage values of the prime motor in real-time for processing and analyzing. When the motor's rotational speed, current and power beyond the predetermined fluctuation range(e.g., tool damage occurrence, etc.); the controlling programs would give the control orders(e.g. pausing, etc.) to the alternating-current motor drive to stop the working of the prime motor. Therefore this system not only can optimize the selection of cutting parameters, and but also can real-time monitor the working currents, rotational speeds, and so on to guarantee a stable and reliable machining process.
2016, 35(1): 118-121.
doi: 10.13433/j.cnki.1003-8728.2016.0121
Abstract:
Steel ball is the rolling element of the ball bearings, whose surface quality directly affect the performance and longevity of the bearing. The developed systems of steel ball surface damage detection have complex unfolding mechanisms, which is not suitable for mass inspection. This paper is based on the sphere surface unfolding method with double image sensors, and the parameters that can fully unfold the sphere surface when the balls are analyzed in a queue. A system is built to illustrate the feasibility of this method. The result shows that the system accurately detect and sort the balls at a high speed of 14,400 pcs/h only take 5 images with each image sensor.
Steel ball is the rolling element of the ball bearings, whose surface quality directly affect the performance and longevity of the bearing. The developed systems of steel ball surface damage detection have complex unfolding mechanisms, which is not suitable for mass inspection. This paper is based on the sphere surface unfolding method with double image sensors, and the parameters that can fully unfold the sphere surface when the balls are analyzed in a queue. A system is built to illustrate the feasibility of this method. The result shows that the system accurately detect and sort the balls at a high speed of 14,400 pcs/h only take 5 images with each image sensor.
2016, 35(1): 122-125.
doi: 10.13433/j.cnki.1003-8728.2016.0122
Abstract:
To resolve the non-linearity of the Gebi topography detector's grounding pressure regulation system, we put forward a control method for the regulation system based on BP(back propagation) neural network and design a BP neural network and PID(proportional/integral/differential) controller. We use the MATLAB to simulate the model of the topography detector's ground pressure regulation system and test the control result. The simulation and experimental results and their analysis show preliminarily that compared with the ordinary PID control method, the BP neural network and PID control method better dynamic characteristics, thus being an effective control method.
To resolve the non-linearity of the Gebi topography detector's grounding pressure regulation system, we put forward a control method for the regulation system based on BP(back propagation) neural network and design a BP neural network and PID(proportional/integral/differential) controller. We use the MATLAB to simulate the model of the topography detector's ground pressure regulation system and test the control result. The simulation and experimental results and their analysis show preliminarily that compared with the ordinary PID control method, the BP neural network and PID control method better dynamic characteristics, thus being an effective control method.
2016, 35(1): 126-131.
doi: 10.13433/j.cnki.1003-8728.2016.0123
Abstract:
The frequency is one of the most important test objects in the fault diagnosis of mechanical equipment. The vibration amplitude is low when the mechanical equipment is in normal operation. In order to detect the vibration frequency quickly and easily, a kind of special vibration measurement sensors is designed according to the law of conservation of energy. The bottom of the sensor is equipped with a liquid medium which can transmit vibration characteristics; the central gas section is a truncated cone structure which the diameter of bottom is greater than the diameter of the top. Due to the same energy concentrated into smaller parts from the area of the larger part, the amplitude of the top is greater than that of the bottom when the vibration characteristics from bottom to top; The sensor is the capacitance sensor at the top, the capacity of the capacitor will change with the vibration of bottom plate. In the hardware processing circuit, a fully differential amplifier circuit is used to amplify electrical signal, amplified analog signal is sampled by high resolution ADC. Nanosecond precision time is measured through software subdivision algorithm, so as to realize the frequency measurement of high precision.
The frequency is one of the most important test objects in the fault diagnosis of mechanical equipment. The vibration amplitude is low when the mechanical equipment is in normal operation. In order to detect the vibration frequency quickly and easily, a kind of special vibration measurement sensors is designed according to the law of conservation of energy. The bottom of the sensor is equipped with a liquid medium which can transmit vibration characteristics; the central gas section is a truncated cone structure which the diameter of bottom is greater than the diameter of the top. Due to the same energy concentrated into smaller parts from the area of the larger part, the amplitude of the top is greater than that of the bottom when the vibration characteristics from bottom to top; The sensor is the capacitance sensor at the top, the capacity of the capacitor will change with the vibration of bottom plate. In the hardware processing circuit, a fully differential amplifier circuit is used to amplify electrical signal, amplified analog signal is sampled by high resolution ADC. Nanosecond precision time is measured through software subdivision algorithm, so as to realize the frequency measurement of high precision.
2016, 35(1): 132-138.
doi: 10.13433/j.cnki.1003-8728.2016.0124
Abstract:
As the passive suspension is uncontrollable, semi-active suspension can not give force out actively and active suspension costs excessive energy, a novel electromagnetic suspension structure is proposed in this paper with the hydraulic shock absorber replaced by MRD, and EA with the traditional spring element in parallel is adopted. Based on energy reclaiming potential for military vehicles and requirements of driving performance and shooting accuracy, a subsection vibration control algorithm is put forward. Analysis results show that the novel electromagnetic suspension structure has a Fail-Safe function, and could increase the range of the suspension adjustable parameters, and could perform the passive, semi-active and active control and the vibration energy could be reclaimed under in certain conditions.
As the passive suspension is uncontrollable, semi-active suspension can not give force out actively and active suspension costs excessive energy, a novel electromagnetic suspension structure is proposed in this paper with the hydraulic shock absorber replaced by MRD, and EA with the traditional spring element in parallel is adopted. Based on energy reclaiming potential for military vehicles and requirements of driving performance and shooting accuracy, a subsection vibration control algorithm is put forward. Analysis results show that the novel electromagnetic suspension structure has a Fail-Safe function, and could increase the range of the suspension adjustable parameters, and could perform the passive, semi-active and active control and the vibration energy could be reclaimed under in certain conditions.
2016, 35(1): 139-143.
doi: 10.13433/j.cnki.1003-8728.2016.0125
Abstract:
In order to find the best parameters from three cab suspension programs, a multi-body dynamics model was built for the cab suspension system of a new designed truck in the multi-body dynamics software ADAMS and verified by the sample vehicle road test through vibration's acceleration Power Spectral Density curve. Taking to reduce the cab floor's vertical acceleration Root Mean Square value as the target, taking the stiffness and the damp of the cab suspension as test factors, the parameters of the cab suspension system were optimized by means of the design of experiments technique. Finally the vehicle's comfort was improved, and the paper provided optimal parameter matching values for the truck to improve cab suspension system performance.
In order to find the best parameters from three cab suspension programs, a multi-body dynamics model was built for the cab suspension system of a new designed truck in the multi-body dynamics software ADAMS and verified by the sample vehicle road test through vibration's acceleration Power Spectral Density curve. Taking to reduce the cab floor's vertical acceleration Root Mean Square value as the target, taking the stiffness and the damp of the cab suspension as test factors, the parameters of the cab suspension system were optimized by means of the design of experiments technique. Finally the vehicle's comfort was improved, and the paper provided optimal parameter matching values for the truck to improve cab suspension system performance.
2016, 35(1): 144-147.
doi: 10.13433/j.cnki.1003-8728.2016.0126
Abstract:
The extrusion force between metal blocks in metal belt continuously variable transmission(MB-CVT) is the research objective; mechanics model of metal block extrusion force has been developed. Through the comparative analysis of numerical solution and analytical solution, the results indicate that the extrusion force increases from the driver pulley ingress beginning to end straight Line Segment bc terminal, and decreases from the driven pulley egress until zero. This trend and the inflection point are consistent with the analytical solution, and it shows that numerical solution correct and the established model is rational. The curve difference between numerical solution and analytical solution indicates that analytical solution has limitation because collision and vibration of metal belt assembly is not considered.
The extrusion force between metal blocks in metal belt continuously variable transmission(MB-CVT) is the research objective; mechanics model of metal block extrusion force has been developed. Through the comparative analysis of numerical solution and analytical solution, the results indicate that the extrusion force increases from the driver pulley ingress beginning to end straight Line Segment bc terminal, and decreases from the driven pulley egress until zero. This trend and the inflection point are consistent with the analytical solution, and it shows that numerical solution correct and the established model is rational. The curve difference between numerical solution and analytical solution indicates that analytical solution has limitation because collision and vibration of metal belt assembly is not considered.
2016, 35(1): 148-152.
doi: 10.13433/j.cnki.1003-8728.2016.0127
Abstract:
Springback is an unavoidable phenomenon in the profile bending, clearance between the dies and profile is one of the significant factors affecting springback. To study the influence of clearance on springback of the profile, the 3D-FE models of rotary draw bending process and unloading springback of 5052 aluminum alloy cap-type profile were established based on ABAQUS, and their reliability were validated via experiments. Then, process simulation and analysis were carried out, and the influence laws of clearance between pressure die, wipe die, bend die, clamp die and profile on the springback were obtained, respectively. The results show that to reduce the clearance among bend die, clamp die and profile can make the springback weaken, the springback will more obvious following the clearance among pressure and profile decrease, while the clearance among wipe die and profile have an hardly effect on the springback of profile.
Springback is an unavoidable phenomenon in the profile bending, clearance between the dies and profile is one of the significant factors affecting springback. To study the influence of clearance on springback of the profile, the 3D-FE models of rotary draw bending process and unloading springback of 5052 aluminum alloy cap-type profile were established based on ABAQUS, and their reliability were validated via experiments. Then, process simulation and analysis were carried out, and the influence laws of clearance between pressure die, wipe die, bend die, clamp die and profile on the springback were obtained, respectively. The results show that to reduce the clearance among bend die, clamp die and profile can make the springback weaken, the springback will more obvious following the clearance among pressure and profile decrease, while the clearance among wipe die and profile have an hardly effect on the springback of profile.
2016, 35(1): 153-158.
doi: 10.13433/j.cnki.1003-8728.2016.0128
Abstract:
In order to analyze the crashworthiness of civil aircraft structure, a numerical fuselage structure model based on the Finite Element method(FEM) was built to study the structural deformation under different impact velocities. The results demonstrated that, with the increasing of initial impact velocities, the deformation of the fuselage nonlinearly increased, and the deformation position extended from the bottom of the fuselage to the cabin floor, which may threat the safety of passengers. Moreover, the optimization of the local structural design and application of energy absorbing material would decrease the acceleration peak value transmitted to passengers, but they have different mechanism of action. In general, as one of the effective approach, the numerical method can improve the structural crashworthiness in aircraft design stage which may reduce the cost and risk of the airworthiness certification test.
In order to analyze the crashworthiness of civil aircraft structure, a numerical fuselage structure model based on the Finite Element method(FEM) was built to study the structural deformation under different impact velocities. The results demonstrated that, with the increasing of initial impact velocities, the deformation of the fuselage nonlinearly increased, and the deformation position extended from the bottom of the fuselage to the cabin floor, which may threat the safety of passengers. Moreover, the optimization of the local structural design and application of energy absorbing material would decrease the acceleration peak value transmitted to passengers, but they have different mechanism of action. In general, as one of the effective approach, the numerical method can improve the structural crashworthiness in aircraft design stage which may reduce the cost and risk of the airworthiness certification test.
2016, 35(1): 159-164.
doi: 10.13433/j.cnki.1003-8728.2016.0129
Abstract:
In this paper, combined the batch manufacture requirement of the new aircraft ARJ21, based on the wing assembly connection structure, the differences between the HER(the Handheld Electromagnetic Riveting) and ADR(the Automatic Drilling & Riveting) from riveting process tests and mechanical property tests was analyzed in this paper, and the feasibility and operation process of the HER as a supplement of the ADR was studied. In this paper, the results shows that the interference fit values are uniform of the HER, the fatigue life of the HER are smaller than those of the ADR, can completely meet the technical requirements of ARJ21. The HER technology working as a supplement of the ADR technology is feasible.
In this paper, combined the batch manufacture requirement of the new aircraft ARJ21, based on the wing assembly connection structure, the differences between the HER(the Handheld Electromagnetic Riveting) and ADR(the Automatic Drilling & Riveting) from riveting process tests and mechanical property tests was analyzed in this paper, and the feasibility and operation process of the HER as a supplement of the ADR was studied. In this paper, the results shows that the interference fit values are uniform of the HER, the fatigue life of the HER are smaller than those of the ADR, can completely meet the technical requirements of ARJ21. The HER technology working as a supplement of the ADR technology is feasible.
