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RSS2016 Vol. 35, No. 4
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2016, 35(4): 493-500.
doi: 10.13433/j.cnki.1003-8728.2016.0401
PDF 1029KB
Abstract:
Numerical control(NC)technology,the combination of mechanical manufacturing and control technology, can be viewed as one of the key technologies in advanced equipment manufacturing industry. From the perspective of CNC machine tool industry, this paper elaborates state of the art and trends of NC system, as well as the latest research results in the aspects of its performance and structure. The specific measures to improve the level of domestic NC system which may provide a reference for China's corresponding research and development are also proposed.
Numerical control(NC)technology,the combination of mechanical manufacturing and control technology, can be viewed as one of the key technologies in advanced equipment manufacturing industry. From the perspective of CNC machine tool industry, this paper elaborates state of the art and trends of NC system, as well as the latest research results in the aspects of its performance and structure. The specific measures to improve the level of domestic NC system which may provide a reference for China's corresponding research and development are also proposed.
2016, 35(4): 501-506.
doi: 10.13433/j.cnki.1003-8728.2016.0402
Abstract:
In order to analyze the impact of the voltage drop on vibration of wind turbine tower, the dynamic model of tower is built by the two-node beam elements; the natural dynamic characteristics of the tower are analyzed. We establish the structural dynamic equation considering the wind shear and the loads acting on the tower. Based on the data from a 1.5MW wind turbine low voltage test, the loads of the tower are calculated, and the dynamic equation is solved by the modal superposition method, the dynamic responses under the symmetry and the asymmetry voltage drops are obtained. The results show that voltage drop has impact on tower vibration, the amplitude of vibration depends on the loads of the turbine, voltage drop type, drop amplitude and drop time.
In order to analyze the impact of the voltage drop on vibration of wind turbine tower, the dynamic model of tower is built by the two-node beam elements; the natural dynamic characteristics of the tower are analyzed. We establish the structural dynamic equation considering the wind shear and the loads acting on the tower. Based on the data from a 1.5MW wind turbine low voltage test, the loads of the tower are calculated, and the dynamic equation is solved by the modal superposition method, the dynamic responses under the symmetry and the asymmetry voltage drops are obtained. The results show that voltage drop has impact on tower vibration, the amplitude of vibration depends on the loads of the turbine, voltage drop type, drop amplitude and drop time.
2016, 35(4): 507-513.
doi: 10.13433/j.cnki.1003-8728.2016.0403
Abstract:
This paper studies the torsional vibration of a gasoline engine crankshaft, based on a 1.8L gasoline engine as the research object. Firstly, the multi-body dynamics software AVL-EXCITE Designer is used to establish crankshaft model, the 3 dimensional mapping software CATIA is used to determine the parameters of the system; with the Spectra LAB, the free vibration and forced vibration of shaft are analyzed to get the natural frequency and inertial parameter of the damper, and the characteristics of crankshaft torsional vibration after the installation of the damper are also analyzed. Then, the software LMS Test.Lab is used to test the torsional vibration, and the test results and simulation results are analyzed. The test results coincide with calculation well and demonstrate the preferable prediction of torsional vibration for an actual gasoline engine crankshaft.
This paper studies the torsional vibration of a gasoline engine crankshaft, based on a 1.8L gasoline engine as the research object. Firstly, the multi-body dynamics software AVL-EXCITE Designer is used to establish crankshaft model, the 3 dimensional mapping software CATIA is used to determine the parameters of the system; with the Spectra LAB, the free vibration and forced vibration of shaft are analyzed to get the natural frequency and inertial parameter of the damper, and the characteristics of crankshaft torsional vibration after the installation of the damper are also analyzed. Then, the software LMS Test.Lab is used to test the torsional vibration, and the test results and simulation results are analyzed. The test results coincide with calculation well and demonstrate the preferable prediction of torsional vibration for an actual gasoline engine crankshaft.
Research on Joint Control of Combined Drivers with Synchronization for Giant Forging Hydraulic Press
2016, 35(4): 514-522.
doi: 10.13433/j.cnki.1003-8728.2016.0404
Abstract:
High-performanced and complex integral die forgings require the forging hydraulic press has the function of synchronous operation with multi-cylinder and stable operation. However, with the reason of the huge moving inertia, complex and variable load, non-uniform forging material and asymmetric in shape, the equipment extremely tends to be unstable in speed and its moving beam is also easy to tilt. In view of these problems, considering the hydraulic nonlinear and complex load, we establish a motion model for forging press. Meanwhile, a method of joint control of combined drivers with synchronization was proposed. With a multi-factor self-tuning fuzzy control to drive subsystem and a fuzzy decoupling control to the synchronization subsystem, the press can not only achieve a forging stable speed, but also has high-precision synchronization performance. At last, the system effectiveness has been verified via the simulation and experiment results. All these will provide with theoretical foundations and guarantees for the large inertia equipment's precise operation.
High-performanced and complex integral die forgings require the forging hydraulic press has the function of synchronous operation with multi-cylinder and stable operation. However, with the reason of the huge moving inertia, complex and variable load, non-uniform forging material and asymmetric in shape, the equipment extremely tends to be unstable in speed and its moving beam is also easy to tilt. In view of these problems, considering the hydraulic nonlinear and complex load, we establish a motion model for forging press. Meanwhile, a method of joint control of combined drivers with synchronization was proposed. With a multi-factor self-tuning fuzzy control to drive subsystem and a fuzzy decoupling control to the synchronization subsystem, the press can not only achieve a forging stable speed, but also has high-precision synchronization performance. At last, the system effectiveness has been verified via the simulation and experiment results. All these will provide with theoretical foundations and guarantees for the large inertia equipment's precise operation.
2016, 35(4): 523-530.
doi: 10.13433/j.cnki.1003-8728.2016.0405
Abstract:
A numerical method for casing structural vibration in a marine centrifugal fan was presented. Firstly, an unsteady flow field calculation of centrifugal fan was employed to obtain the vibration sources of volute casing; then a weak fluid-structure coupling algorithm was used for grid interpolation and loading aerodynamics loads; at the last, the volute structure vibration response was obtained based on the mode superposition method of FEM. Numerical results of pressure fluctuations in the flow fields and vibration responses are compared with experiments respectively, showing a good agreement. The mechanism of fluid-induced structural vibration was discussed through pressure fluctuations in the fluid fields and structural vibration responses, the pressure fluctuations of BPF are the primary exciting source of fluid-structure vibrations, BPF component is predominant in vibration frequency response. The major structural vibration response of volute casing results from contributions of both unsteady aerodynamics and vibration modal in BPF.
A numerical method for casing structural vibration in a marine centrifugal fan was presented. Firstly, an unsteady flow field calculation of centrifugal fan was employed to obtain the vibration sources of volute casing; then a weak fluid-structure coupling algorithm was used for grid interpolation and loading aerodynamics loads; at the last, the volute structure vibration response was obtained based on the mode superposition method of FEM. Numerical results of pressure fluctuations in the flow fields and vibration responses are compared with experiments respectively, showing a good agreement. The mechanism of fluid-induced structural vibration was discussed through pressure fluctuations in the fluid fields and structural vibration responses, the pressure fluctuations of BPF are the primary exciting source of fluid-structure vibrations, BPF component is predominant in vibration frequency response. The major structural vibration response of volute casing results from contributions of both unsteady aerodynamics and vibration modal in BPF.
2016, 35(4): 531-534.
doi: 10.13433/j.cnki.1003-8728.2016.0406
Abstract:
A single-degree-of-freedom vibrating system with two-sided constraints is considered. Routes from doubling-periodic bifurcation and Grazing bifurcation of periodic motion to chaotic motion are illustrated by numerical methods. The principle and procedure of the OGY method are introduced. Due to sensitivity to tiny perturbations and traversal properties of chaotic orbits, an unstable fixed point embedded in the chaotic attractor is chosen as the controlling target, and chaotic behavior is controlled to the desired orbit by applying tiny perturbation on a system parameter. The simulated results show that the chaotic motion is suppressed in a very short time period.
A single-degree-of-freedom vibrating system with two-sided constraints is considered. Routes from doubling-periodic bifurcation and Grazing bifurcation of periodic motion to chaotic motion are illustrated by numerical methods. The principle and procedure of the OGY method are introduced. Due to sensitivity to tiny perturbations and traversal properties of chaotic orbits, an unstable fixed point embedded in the chaotic attractor is chosen as the controlling target, and chaotic behavior is controlled to the desired orbit by applying tiny perturbation on a system parameter. The simulated results show that the chaotic motion is suppressed in a very short time period.
2016, 35(4): 535-538.
doi: 10.13433/j.cnki.1003-8728.2016.0407
Abstract:
According to the initial posture of a mobile manipulator, the position of the object to be grasped as well as the constraints of obstacles, the collision-free trajectory of the mobile manipulator's end point is planned with A* algorithm. Considering that there are multiple solutions for redundant DOF and using inverse kinematics, we propose a joint angle optimization method based on minimum angle offset under the constraints of obstacles. In order to improve the adaptability, the mobile manipulator is endowed with the ability to update its end point trajectory and adjust its posture according to the current environment. The effectiveness of the method is verified by simulation.
According to the initial posture of a mobile manipulator, the position of the object to be grasped as well as the constraints of obstacles, the collision-free trajectory of the mobile manipulator's end point is planned with A* algorithm. Considering that there are multiple solutions for redundant DOF and using inverse kinematics, we propose a joint angle optimization method based on minimum angle offset under the constraints of obstacles. In order to improve the adaptability, the mobile manipulator is endowed with the ability to update its end point trajectory and adjust its posture according to the current environment. The effectiveness of the method is verified by simulation.
2016, 35(4): 539-544.
doi: 10.13433/j.cnki.1003-8728.2016.0408
Abstract:
The kinematics model of an industrial robot is established with the screw theory, and a sub-problem category is proposed for its general inverse kinematics solution. The link parameters of the robot is calculated with the special configuration method and the robot model library of simulation software DELMIA(digital enterprise lean manufacturing interaction application). The motion of the first three joints is defined as a new type of sub-problem, which can be described as a known point rotating around two parallel axes and an axe perpendicular to the first two axes at a given point. Combined with the classical Paden-Kahan sub-problem, eight groups of analytic expressions for inverse solution are derived. Taking the IRB1400 arc welding robot as an example, we verify the algorithm. The simulation results show that the algorithm has an error of 10-12 orders of magnitude and needs less than 0.12 ms, which satisfies the high requirements for the accuracy and real-time of the robot's control system.
The kinematics model of an industrial robot is established with the screw theory, and a sub-problem category is proposed for its general inverse kinematics solution. The link parameters of the robot is calculated with the special configuration method and the robot model library of simulation software DELMIA(digital enterprise lean manufacturing interaction application). The motion of the first three joints is defined as a new type of sub-problem, which can be described as a known point rotating around two parallel axes and an axe perpendicular to the first two axes at a given point. Combined with the classical Paden-Kahan sub-problem, eight groups of analytic expressions for inverse solution are derived. Taking the IRB1400 arc welding robot as an example, we verify the algorithm. The simulation results show that the algorithm has an error of 10-12 orders of magnitude and needs less than 0.12 ms, which satisfies the high requirements for the accuracy and real-time of the robot's control system.
2016, 35(4): 545-550.
doi: 10.13433/j.cnki.1003-8728.2016.0409
Abstract:
We analyzed the kinematics and dynamics of a large horsepower tractor according to its performance parameters and then designed a geometric type hydro-mechanical continuously variable transmission (HMCVT) with a double-planetary gear, including the transmission ratio of shifting mechanism, diesel engine, clutches and hydraulic speed regulator. We compared the experimental and theoretical curves of the stepless speed regulator, and analyzed the causes of error and the rationality of the design scheme. In three operation modes of the tractor, the experimental results for matching the HMCVT and the engine verify the continuously stepless speed regulation characteristics and the dynamic response performance.
We analyzed the kinematics and dynamics of a large horsepower tractor according to its performance parameters and then designed a geometric type hydro-mechanical continuously variable transmission (HMCVT) with a double-planetary gear, including the transmission ratio of shifting mechanism, diesel engine, clutches and hydraulic speed regulator. We compared the experimental and theoretical curves of the stepless speed regulator, and analyzed the causes of error and the rationality of the design scheme. In three operation modes of the tractor, the experimental results for matching the HMCVT and the engine verify the continuously stepless speed regulation characteristics and the dynamic response performance.
2016, 35(4): 551-556.
doi: 10.13433/j.cnki.1003-8728.2016.0410
Abstract:
Based on the analysis of insufficient selection of accelerated stresses in reliability enhancement testing, by examining the fault physics of hydraulic cylinders the hydraulic oil film thickness is deduced through Reynolds equation and the relationship between the oil leakage and hydraulic oil volume and pressure loads in hydraulic cylinder piston reciprocating motion process. The correctness is proved for the selection of acceleration stress in reliability enhancement test by comparing the oil leakage of hydraulic cylinder in the presence or absence of defects. The hydraulic cylinder of end toothed disc dividing type NC rotary is taken as the example and comparative tests are conducted with different stress levels, the results show the consistency with those obtained by analyzing fault physics of accelerated stresses in reliability enhancement testing.
Based on the analysis of insufficient selection of accelerated stresses in reliability enhancement testing, by examining the fault physics of hydraulic cylinders the hydraulic oil film thickness is deduced through Reynolds equation and the relationship between the oil leakage and hydraulic oil volume and pressure loads in hydraulic cylinder piston reciprocating motion process. The correctness is proved for the selection of acceleration stress in reliability enhancement test by comparing the oil leakage of hydraulic cylinder in the presence or absence of defects. The hydraulic cylinder of end toothed disc dividing type NC rotary is taken as the example and comparative tests are conducted with different stress levels, the results show the consistency with those obtained by analyzing fault physics of accelerated stresses in reliability enhancement testing.
2016, 35(4): 557-561.
doi: 10.13433/j.cnki.1003-8728.2016.0411
Abstract:
We analyzed a 3PUS-S(P) parallel spherical metamorphic mechanism which consists of a moving platform, a base plate, three PUS legs and one middle S(P) leg. This mechanism has two configurations: the 1st normal configuration and the 2nd metamorphic configuration. The moving platform has three revolute degrees of freedom which is equivalent to spherical joint and extra translational freedom in the direction of radius. Firstly, the kinematic positional inverse solution equations are established based on the vector algebra method. Then the constraints of workspace are built based on the inverse kinematic solution. Finally, the boundary of workspace, on the basis of the study of real mechanism is determined with the boundary search method.
We analyzed a 3PUS-S(P) parallel spherical metamorphic mechanism which consists of a moving platform, a base plate, three PUS legs and one middle S(P) leg. This mechanism has two configurations: the 1st normal configuration and the 2nd metamorphic configuration. The moving platform has three revolute degrees of freedom which is equivalent to spherical joint and extra translational freedom in the direction of radius. Firstly, the kinematic positional inverse solution equations are established based on the vector algebra method. Then the constraints of workspace are built based on the inverse kinematic solution. Finally, the boundary of workspace, on the basis of the study of real mechanism is determined with the boundary search method.
2016, 35(4): 562-567.
doi: 10.13433/j.cnki.1003-8728.2016.0412
Abstract:
The longitudinal vibration of the drill string is the principal factor causing drill bit failure and drill pipe wear, on which the transverse inertia effect has an important influence. Based on this point, the longitudinal vibration control of drilling string is studied considering its lateral inertial effect by using the Rayleigh-Love rode model. Assuming that the drilling string can be divided into several parts with material damping of Rayleigh-Love rod, and drilling fluid around drill string are elastic layers with common attributes. According to the actual working condition of drilling string and regarding the whole drill string as the object, simplified mathematical models and vibration equations are established. According to the relationships between parameters and the boundary conditions of the models, we obtain the solutions to complex impedance and the differential equations of dynamic stiffness at the bottom of the drill string, and the influences of different parameters on the dynamic stiffness of drill string are analyzed by MATLAB. The results show that dynamic stiffness of the drilling string increases gradually with the frequency in the form of periodic change, while the vibration period increases; when other related parameters remain unchanged, the absolute value of dynamic stiffness increases with the increase of the length and cross-sectional area of the drill string; damping coefficient is bigger, which means that the force of bottom-hole to drilling string is bigger, so the amplitude of dynamic stiffness is smaller; when Poisson's ratio increases, its dynamic stiffness period increases with the frequency.
The longitudinal vibration of the drill string is the principal factor causing drill bit failure and drill pipe wear, on which the transverse inertia effect has an important influence. Based on this point, the longitudinal vibration control of drilling string is studied considering its lateral inertial effect by using the Rayleigh-Love rode model. Assuming that the drilling string can be divided into several parts with material damping of Rayleigh-Love rod, and drilling fluid around drill string are elastic layers with common attributes. According to the actual working condition of drilling string and regarding the whole drill string as the object, simplified mathematical models and vibration equations are established. According to the relationships between parameters and the boundary conditions of the models, we obtain the solutions to complex impedance and the differential equations of dynamic stiffness at the bottom of the drill string, and the influences of different parameters on the dynamic stiffness of drill string are analyzed by MATLAB. The results show that dynamic stiffness of the drilling string increases gradually with the frequency in the form of periodic change, while the vibration period increases; when other related parameters remain unchanged, the absolute value of dynamic stiffness increases with the increase of the length and cross-sectional area of the drill string; damping coefficient is bigger, which means that the force of bottom-hole to drilling string is bigger, so the amplitude of dynamic stiffness is smaller; when Poisson's ratio increases, its dynamic stiffness period increases with the frequency.
2016, 35(4): 568-572.
doi: 10.13433/j.cnki.1003-8728.2016.0413
Abstract:
The use of "single feature alarm" and "threshold alarm" makes the single alarm mode for the reciprocating compressor, which leads to blindly parking and affect the production. It is also unable to analyze whether the operating condition of equipment is abnormal or not comprehensively and to alarm in advance. An automatic alarm system for reciprocating compressor based on state subspace is proposed in this paper. Features of operating condition signals of the equipment are extracted to construct a multidimensional feature matrix. The dimension is then reduced by KPCA (Kernel Principal Component Analysis, KPCA) method to construct the state subspace. The difference degree between the normal state subspace and the current state subspace is calculated and the alarm threshold of the difference degree is obtained by self-learning of data of fault cases. Verified by actual failure cases, the method can significantly advance the alarm time point of typical failure of reciprocating compressor and improve the fault alarm ability of online condition monitoring system.
The use of "single feature alarm" and "threshold alarm" makes the single alarm mode for the reciprocating compressor, which leads to blindly parking and affect the production. It is also unable to analyze whether the operating condition of equipment is abnormal or not comprehensively and to alarm in advance. An automatic alarm system for reciprocating compressor based on state subspace is proposed in this paper. Features of operating condition signals of the equipment are extracted to construct a multidimensional feature matrix. The dimension is then reduced by KPCA (Kernel Principal Component Analysis, KPCA) method to construct the state subspace. The difference degree between the normal state subspace and the current state subspace is calculated and the alarm threshold of the difference degree is obtained by self-learning of data of fault cases. Verified by actual failure cases, the method can significantly advance the alarm time point of typical failure of reciprocating compressor and improve the fault alarm ability of online condition monitoring system.
2016, 35(4): 573-579.
doi: 10.13433/j.cnki.1003-8728.2016.0414
Abstract:
A 6-PSS three dimensional parallel mechanism for simulating jaw chewing system is constructed via UG software. Based on the homogeneous transformation matrix, which is used to describe the position and orientation of the moving platform state during exercise, the formulae for solving the inverse problems are derived. Then, the boundary of the workspace is solved with boundary search method after the workspace search scope and influence factors are determined. The workspaces of different chew styles are compared. Through the analysis on workspace and the correlation analysis on the dimension parameters of chewing mechanism, design variables, objective functions and constraints of workspace optimization model are determined. And the rod length and the spherical joint support vectors are optimized by the coordinates of the rotation law technique. Furthermore, the suitable workspace to meet with the bionic essentiality of the manipulator has been obtained. The workspace optimization has a great guiding significance for trajectory planning, dynamics analysis and control design of the simulator.
A 6-PSS three dimensional parallel mechanism for simulating jaw chewing system is constructed via UG software. Based on the homogeneous transformation matrix, which is used to describe the position and orientation of the moving platform state during exercise, the formulae for solving the inverse problems are derived. Then, the boundary of the workspace is solved with boundary search method after the workspace search scope and influence factors are determined. The workspaces of different chew styles are compared. Through the analysis on workspace and the correlation analysis on the dimension parameters of chewing mechanism, design variables, objective functions and constraints of workspace optimization model are determined. And the rod length and the spherical joint support vectors are optimized by the coordinates of the rotation law technique. Furthermore, the suitable workspace to meet with the bionic essentiality of the manipulator has been obtained. The workspace optimization has a great guiding significance for trajectory planning, dynamics analysis and control design of the simulator.
2016, 35(4): 580-583.
doi: 10.13433/j.cnki.1003-8728.2016.0415
Abstract:
The post-processing method is different among general CAD/CAM software in computer-aided programming. In this paper, according to the principles of polar coordinate programming and cylindrical coordinate programming of FANUC 18i system, we develop two sets of post-processing for turn-milling machining by UG Post Builder for axial processing and radial processing cases, respectively. To verify the reliability and availability of the software,the turn-milling operations and machining simulations were made for a complex part in UG CAM module,and two experiments of cut aluminum alloys in PD/C-TMC CNC machine tool of SPINNER company were conducted. The results and their analysis showed preliminarily that the CNC programming converted by the post-processors can be executed directly in FANUC system without any errors. It is proved that the two sets of post-processing are highly reliable, particularly suitable for the actual production in turn-milling machining and valuable for wide spread applications.
The post-processing method is different among general CAD/CAM software in computer-aided programming. In this paper, according to the principles of polar coordinate programming and cylindrical coordinate programming of FANUC 18i system, we develop two sets of post-processing for turn-milling machining by UG Post Builder for axial processing and radial processing cases, respectively. To verify the reliability and availability of the software,the turn-milling operations and machining simulations were made for a complex part in UG CAM module,and two experiments of cut aluminum alloys in PD/C-TMC CNC machine tool of SPINNER company were conducted. The results and their analysis showed preliminarily that the CNC programming converted by the post-processors can be executed directly in FANUC system without any errors. It is proved that the two sets of post-processing are highly reliable, particularly suitable for the actual production in turn-milling machining and valuable for wide spread applications.
2016, 35(4): 584-588.
doi: 10.13433/j.cnki.1003-8728.2016.0416
Abstract:
The common normal line length and the orthogonal error are presented to describe the errors of actual AB-axis mechanism in this paper, the motion equation of actual AB-axis with these two errors is established by the six set continuous coordinate transformations. According to those equations, actual AB-axis mechanism will accurately point to the desired target point. Through an example the main errors to cause pointing error are analyzed, so that the theoretical foundation for the development of high precision AB-axis mechanism is laid.
The common normal line length and the orthogonal error are presented to describe the errors of actual AB-axis mechanism in this paper, the motion equation of actual AB-axis with these two errors is established by the six set continuous coordinate transformations. According to those equations, actual AB-axis mechanism will accurately point to the desired target point. Through an example the main errors to cause pointing error are analyzed, so that the theoretical foundation for the development of high precision AB-axis mechanism is laid.
2016, 35(4): 589-593.
doi: 10.13433/j.cnki.1003-8728.2016.0417
Abstract:
The residual life prediction for the growing waste mining parts is the premise of the remanufacturing recycling, in the special conditions of dusty, corrosion, fast wear, the traditional life prediction methods are inaccurate. Therefore, a new method of the Weibull distribution models parameter estimation by combining weighted least squares method regarding the square and the minimum of horizontal and vertical residuals and mean rank order is put forward. A two-parameter Weibull distribution regarding remanufacturing residual life prediction models is established. By model analysis, a new solution for the residual life prediction of waste parts in special working conditions is provided. The crankshaft of the electric wheel dump truck is taken as an example to illustrate the feasibility of the present method.
The residual life prediction for the growing waste mining parts is the premise of the remanufacturing recycling, in the special conditions of dusty, corrosion, fast wear, the traditional life prediction methods are inaccurate. Therefore, a new method of the Weibull distribution models parameter estimation by combining weighted least squares method regarding the square and the minimum of horizontal and vertical residuals and mean rank order is put forward. A two-parameter Weibull distribution regarding remanufacturing residual life prediction models is established. By model analysis, a new solution for the residual life prediction of waste parts in special working conditions is provided. The crankshaft of the electric wheel dump truck is taken as an example to illustrate the feasibility of the present method.
2016, 35(4): 594-600.
doi: 10.13433/j.cnki.1003-8728.2016.0418
Abstract:
To explore the deforming mechanism in high speed cold roll-beating of 40Cr, according to the plastic deforming mechanism, we carry out the striking experiments to obtain the strain-stress curves under high speed cold roll-beating conditions of 40Cr. Considering the plastic deformation characteristics of high speed and big deformation, based on the obtained strain-stress curve, we use the Deform simulation software to analyze the high speed cold roll-beating forming in different deforming zones under different temperatures and stain rates so as to reveal the variation laws of strain, stress, temperature and metal flowing characters, which will be helpful to explain the cold roll-beating forming laws and can lay the foundation for further study of cold roll-beating.
To explore the deforming mechanism in high speed cold roll-beating of 40Cr, according to the plastic deforming mechanism, we carry out the striking experiments to obtain the strain-stress curves under high speed cold roll-beating conditions of 40Cr. Considering the plastic deformation characteristics of high speed and big deformation, based on the obtained strain-stress curve, we use the Deform simulation software to analyze the high speed cold roll-beating forming in different deforming zones under different temperatures and stain rates so as to reveal the variation laws of strain, stress, temperature and metal flowing characters, which will be helpful to explain the cold roll-beating forming laws and can lay the foundation for further study of cold roll-beating.
2016, 35(4): 601-605.
doi: 10.13433/j.cnki.1003-8728.2016.0419
Abstract:
Aiming at the inconveniently installation of acceleration sensor in the machine tool equipment, the friction characteristic was extracted with the empirical mode decomposition (EMD) and the intrinsic mode function (IMF) energy method for signal processing, and the friction and wear characteristics was analyzed. Firstly, the contrast experiments were designed to obtain the current signals for of the four groups of transmission chains. Secondly, the current signals were decomposed into a finite number of IMF. Finally, the edge frequency band and friction characteristic values E(IMF3) were extracted by calculating energy per unit time of IMF component of each order. The experimental results show that the four stages of wear states can be obtained by changing the E(IMF3) curve, and the purpose of on-line monitoring for the wear states of the guide rail was realized.
Aiming at the inconveniently installation of acceleration sensor in the machine tool equipment, the friction characteristic was extracted with the empirical mode decomposition (EMD) and the intrinsic mode function (IMF) energy method for signal processing, and the friction and wear characteristics was analyzed. Firstly, the contrast experiments were designed to obtain the current signals for of the four groups of transmission chains. Secondly, the current signals were decomposed into a finite number of IMF. Finally, the edge frequency band and friction characteristic values E(IMF3) were extracted by calculating energy per unit time of IMF component of each order. The experimental results show that the four stages of wear states can be obtained by changing the E(IMF3) curve, and the purpose of on-line monitoring for the wear states of the guide rail was realized.
2016, 35(4): 606-613.
doi: 10.13433/j.cnki.1003-8728.2016.0420
Abstract:
In order to control the surface quality of cold roll-beating forming part, the characterization parameters of scale-texture are studied in this paper. According to the basic principles of cold roll-beating forming, we analyze the main reasons of scale-texture flaws. The height and width of scale-texture is studied by theoretical analysis under the different ways of cold roll-beating and a relational expression for that, the revolution speed of the rolling wheel and the feeding horizontal speed of the workpiece. Because the effect of the strain rate, rolling wheel rotation and friction are not considered, the errors of calculation results are large, so expressions are complemented by the simulation results via ABAQUS software, so that it can more e accurately reflect the height scale-texture under technical state. The forming experiment is conducted on the refitted cold roll-beating forming equipment, the height of scale-texture and 2D section shape is obtained by scale-texture measurement on the surface of cold roll-beating forming parts, the validity of post-correction formula is verified by inter comparison of experimental results and 2D section shape, so as to provide reference for surface quality control and selection of parameters parameters.
In order to control the surface quality of cold roll-beating forming part, the characterization parameters of scale-texture are studied in this paper. According to the basic principles of cold roll-beating forming, we analyze the main reasons of scale-texture flaws. The height and width of scale-texture is studied by theoretical analysis under the different ways of cold roll-beating and a relational expression for that, the revolution speed of the rolling wheel and the feeding horizontal speed of the workpiece. Because the effect of the strain rate, rolling wheel rotation and friction are not considered, the errors of calculation results are large, so expressions are complemented by the simulation results via ABAQUS software, so that it can more e accurately reflect the height scale-texture under technical state. The forming experiment is conducted on the refitted cold roll-beating forming equipment, the height of scale-texture and 2D section shape is obtained by scale-texture measurement on the surface of cold roll-beating forming parts, the validity of post-correction formula is verified by inter comparison of experimental results and 2D section shape, so as to provide reference for surface quality control and selection of parameters parameters.
2016, 35(4): 614-619.
doi: 10.13433/j.cnki.1003-8728.2016.0421
Abstract:
Based on the response surface method the underwater robot pressure hull is optimized with 5 optimization variables. In the optimization, the ANSYS software is used to solve the structural stress response value, and combined experiment is applied to reduce the optimized variable range hence to perform response surface experimental design. The constraint condition of optimization is the requirements of structural stress and stability,the optimization objective is to minimize the mass of the robot pressure hull. The response surface optimization solution is obtained with experimental design software Design-Expert, and the results are compared with the optimization results got from 1stOpt Optimization software based on different algorithms the optimization results show that the weight of pressure hull is decreased by 15.52% and the pressure hull can meet the requirements of structural strength and stability, therefore the optimization goal is achieved.
Based on the response surface method the underwater robot pressure hull is optimized with 5 optimization variables. In the optimization, the ANSYS software is used to solve the structural stress response value, and combined experiment is applied to reduce the optimized variable range hence to perform response surface experimental design. The constraint condition of optimization is the requirements of structural stress and stability,the optimization objective is to minimize the mass of the robot pressure hull. The response surface optimization solution is obtained with experimental design software Design-Expert, and the results are compared with the optimization results got from 1stOpt Optimization software based on different algorithms the optimization results show that the weight of pressure hull is decreased by 15.52% and the pressure hull can meet the requirements of structural strength and stability, therefore the optimization goal is achieved.
2016, 35(4): 620-625.
doi: 10.13433/j.cnki.1003-8728.2016.0422
Abstract:
The reverse engineering was used to establish a geometric model for child dummy head of Q6, then a detailed and high-quality Q6 child dummy head finite element (FE) model was developed with proper material models. Based on the calibration test results of a physical dummy head, the ordinate-based curve matching method was applied to the multi-objective optimization of the material model parameters of head skin of the FE model in both frontal and side calibration tests, and optimal results were acquired after several iterations by sequential with domain reduction metamodel-based optimization method. The optimized results were used as material parameters of head skin, and the simulation shows that the FE model for child dummy head of Q6 meets the requirements of calibration quite well.
The reverse engineering was used to establish a geometric model for child dummy head of Q6, then a detailed and high-quality Q6 child dummy head finite element (FE) model was developed with proper material models. Based on the calibration test results of a physical dummy head, the ordinate-based curve matching method was applied to the multi-objective optimization of the material model parameters of head skin of the FE model in both frontal and side calibration tests, and optimal results were acquired after several iterations by sequential with domain reduction metamodel-based optimization method. The optimized results were used as material parameters of head skin, and the simulation shows that the FE model for child dummy head of Q6 meets the requirements of calibration quite well.
2016, 35(4): 626-629.
doi: 10.13433/j.cnki.1003-8728.2016.0423
Abstract:
For the low-rigidity and easy deformation of aircraft components in assembly process, a locating strategy optimization method of aircraft weakly rigid parts was presented. According to "N-2-1" positioning principle, the method took the minimum deformation of parts caused by deadweight as the objective function. The maximum deformation of parts under different positioning strategies was calculated by the finite element method, then the optimal points layout was given based on the iteratively search of the firefly algorithm. Finally, taking typical aircraft structure as an example, the feasibility and validity of the method was verified.
For the low-rigidity and easy deformation of aircraft components in assembly process, a locating strategy optimization method of aircraft weakly rigid parts was presented. According to "N-2-1" positioning principle, the method took the minimum deformation of parts caused by deadweight as the objective function. The maximum deformation of parts under different positioning strategies was calculated by the finite element method, then the optimal points layout was given based on the iteratively search of the firefly algorithm. Finally, taking typical aircraft structure as an example, the feasibility and validity of the method was verified.
2016, 35(4): 630-635.
doi: 10.13433/j.cnki.1003-8728.2016.0424
Abstract:
An overrunning spring clutch, which is simple, reliable and light, can be used for the transmission system of a high-speed helicopter. The clutch relies on the friction of the spring and the input/output shell to convey torque under the condition of self-locking with the forward transfer power, the minimum friction coefficient is analyzed under the condition of contact. The friction coefficient of 4Cr5MoSiV steel was studied by changing the surface roughness; the study results show that the friction coefficient increases with the increase of surface roughness. With the optimal value of the surface roughness, the friction coefficient is minimal. The overrunning spring clutch has the wear problem. Based on the Archard wear model, the wear life of overrunning spring clutch is obtained with the composite wear calculation method.
An overrunning spring clutch, which is simple, reliable and light, can be used for the transmission system of a high-speed helicopter. The clutch relies on the friction of the spring and the input/output shell to convey torque under the condition of self-locking with the forward transfer power, the minimum friction coefficient is analyzed under the condition of contact. The friction coefficient of 4Cr5MoSiV steel was studied by changing the surface roughness; the study results show that the friction coefficient increases with the increase of surface roughness. With the optimal value of the surface roughness, the friction coefficient is minimal. The overrunning spring clutch has the wear problem. Based on the Archard wear model, the wear life of overrunning spring clutch is obtained with the composite wear calculation method.
2016, 35(4): 636-640.
doi: 10.13433/j.cnki.1003-8728.2016.0425
Abstract:
The risk assessment approach for the civil transport category airplanes during continued airworthiness has been established in the present analysis. The risk types of the event, the severity level of the event consequence and the approach to determine the probability level of the event have been given. The risk matrix method and the Gunstone method were used to determine the risk levels and the time of appropriate corrective actions. The risk assessment of wing fuel tank overpressure damage event of a certain airplane was analyzed using the present approach. The risk level of the event was determined and appropriate corrective actions were also given.
The risk assessment approach for the civil transport category airplanes during continued airworthiness has been established in the present analysis. The risk types of the event, the severity level of the event consequence and the approach to determine the probability level of the event have been given. The risk matrix method and the Gunstone method were used to determine the risk levels and the time of appropriate corrective actions. The risk assessment of wing fuel tank overpressure damage event of a certain airplane was analyzed using the present approach. The risk level of the event was determined and appropriate corrective actions were also given.
2016, 35(4): 641-645.
doi: 10.13433/j.cnki.1003-8728.2016.0426
Abstract:
The laminate structure of an I-beam with strips and web is designed based on the classic laminate theory and the strength criterion of maximum stress. The MATLAB software programming is used and the characteristics of I-beam are considered in the design process. Three finite element models of the I-beam composite with different laminate structures are constructed based on the manufacture process. The stress analysis of the three different laminate I-beam composite is carried out. The stress distributions of some representative layers are given. The stresses of material principal directions are calculated. The ultimate loads of the three laminate I-beams composite are determinated based on the strength criterion of maximum stress on condition that the I-beams composite is in linear state. The results of finite element analysis are compared with that of classic laminate theory. It is showed that: 1) the ultimate loads of the I-beams composite of inner C connection and L connection are higher than the theoretical load; the ultimate load of the I-beam composite of outer C connection is lower than the theoretical load; the relative errors of the three ultimate loads are all smaller than 9% which means the finite element results fit well with the theoretical ultimate load; 2) the initial damages of the I-beams are all occurred in the 45° layer on the lower strips. The damage mode is matrix fracture; 3) the ultimate load of I-beam composite is mainly determined by the strength of the matrix; 4) the damage position is in the cross-section of the fixed end; 5) the design method of I-beam laminate composite based on classic laminate theory and the finite element models of composite I-beam composite built in this paper are reasonable and reliable.
The laminate structure of an I-beam with strips and web is designed based on the classic laminate theory and the strength criterion of maximum stress. The MATLAB software programming is used and the characteristics of I-beam are considered in the design process. Three finite element models of the I-beam composite with different laminate structures are constructed based on the manufacture process. The stress analysis of the three different laminate I-beam composite is carried out. The stress distributions of some representative layers are given. The stresses of material principal directions are calculated. The ultimate loads of the three laminate I-beams composite are determinated based on the strength criterion of maximum stress on condition that the I-beams composite is in linear state. The results of finite element analysis are compared with that of classic laminate theory. It is showed that: 1) the ultimate loads of the I-beams composite of inner C connection and L connection are higher than the theoretical load; the ultimate load of the I-beam composite of outer C connection is lower than the theoretical load; the relative errors of the three ultimate loads are all smaller than 9% which means the finite element results fit well with the theoretical ultimate load; 2) the initial damages of the I-beams are all occurred in the 45° layer on the lower strips. The damage mode is matrix fracture; 3) the ultimate load of I-beam composite is mainly determined by the strength of the matrix; 4) the damage position is in the cross-section of the fixed end; 5) the design method of I-beam laminate composite based on classic laminate theory and the finite element models of composite I-beam composite built in this paper are reasonable and reliable.
2016, 35(4): 646-651.
doi: 10.13433/j.cnki.1003-8728.2016.0427
Abstract:
In order to improve the wear resistance of Ti6Al4V alloy contacted with polytetrafluoroethylene-based (PTFE) composites in seawater, plasma nitriding (PN) and micro arc oxidation (MAO) were used to modify the surface of Ti6Al4V alloy. The tribological properties of Ti6Al4V alloy matrix and its modified layers sliding with polytetrafluoroethylene-based (PTFE) composites in seawater were comparatively investigated. The PTFE composites were made with glass fiber and bronze separately by compression molding. The results indicate that low friction coefficients were shown in the modified layers of Ti6Al4V alloy sliding with PTFE composites in seawater. The Ti6Al4V alloy exhibits the poor wear resistance and leads to the serious wear of PTFE composites. The above two kinds of surface treatments effectively improve the wear resistance of Ti6Al4V alloy. The PN treatment with reducing the wear of PTFE composites shows the better wear resistance comparing with that via MAO treatment with accelerating the wear of PTFE composites. The glass fiber reinforced PTFE shows the better wear resistance comparing with that of the bronze reinforced PTFE in the same condition. It has obvious advantages that the titanium alloy with PN treatment contacted with glass fiber reinforced PTFE were chosen as the materials of the tribological components used in hydraulic transmission in the marine environment application.
In order to improve the wear resistance of Ti6Al4V alloy contacted with polytetrafluoroethylene-based (PTFE) composites in seawater, plasma nitriding (PN) and micro arc oxidation (MAO) were used to modify the surface of Ti6Al4V alloy. The tribological properties of Ti6Al4V alloy matrix and its modified layers sliding with polytetrafluoroethylene-based (PTFE) composites in seawater were comparatively investigated. The PTFE composites were made with glass fiber and bronze separately by compression molding. The results indicate that low friction coefficients were shown in the modified layers of Ti6Al4V alloy sliding with PTFE composites in seawater. The Ti6Al4V alloy exhibits the poor wear resistance and leads to the serious wear of PTFE composites. The above two kinds of surface treatments effectively improve the wear resistance of Ti6Al4V alloy. The PN treatment with reducing the wear of PTFE composites shows the better wear resistance comparing with that via MAO treatment with accelerating the wear of PTFE composites. The glass fiber reinforced PTFE shows the better wear resistance comparing with that of the bronze reinforced PTFE in the same condition. It has obvious advantages that the titanium alloy with PN treatment contacted with glass fiber reinforced PTFE were chosen as the materials of the tribological components used in hydraulic transmission in the marine environment application.
2016, 35(4): 652-656.
doi: 10.13433/j.cnki.1003-8728.2016.0428
Abstract:
In order to predict the materials' low cycle fatigue life, the Formula of Three-Parameter Power Function and Ostergren model were investigated and a damage energy life prediction model was proposed based on the Three-Parameter Power Function. The low cycle fatigue test data for superalloy, titanium alloy and other metallic materials were used to verify this model, and its analysis results was compared with the Manson-Coffin model's laterly. Using the low cycle fatigue test data of superalloy GH4133 at 250℃ to establish its cyclic stress-strain curve and damage energy life prediction model, at the same time tested the curve and model. The results show that the established cyclic stress-strain curve can accurately reflect the relation between stress and strain in such circumstances. Besides, the damage energy life prediction model has a better fitting effect for the twelve materials' low cycle fatigue test data and its life prediction accuracy is significant higher than that of Manson-Coffin model.
In order to predict the materials' low cycle fatigue life, the Formula of Three-Parameter Power Function and Ostergren model were investigated and a damage energy life prediction model was proposed based on the Three-Parameter Power Function. The low cycle fatigue test data for superalloy, titanium alloy and other metallic materials were used to verify this model, and its analysis results was compared with the Manson-Coffin model's laterly. Using the low cycle fatigue test data of superalloy GH4133 at 250℃ to establish its cyclic stress-strain curve and damage energy life prediction model, at the same time tested the curve and model. The results show that the established cyclic stress-strain curve can accurately reflect the relation between stress and strain in such circumstances. Besides, the damage energy life prediction model has a better fitting effect for the twelve materials' low cycle fatigue test data and its life prediction accuracy is significant higher than that of Manson-Coffin model.
