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RSS2015 Vol. 34, No. 3
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2015, 34(3): 329-333.
doi: 10.13433/j.cnki.1003-8728.2015.0301
PDF 2784KB
Abstract:
This paper combines the thermal elastic hydrodynamic lubrication(TEHL) analysis with the loaded tooth contact analysis(LTCA) to predict the slide friction efficiency of the spur gear. LTCA is used to calculate the normal load and kinematics of the discrete contact points for the TEHL. The multi-level method, multi-level multi-integration (MIMI) approach and the sequential column sweeping for solving the pressure, elastic deformation and the temperature of the lubricated regions are used alternatively. The results show that when the change of tooth load is small, the effect of the load to the friction coefficient can be ignored; but the larger increase of the load will lead to reduced friction coefficient.
This paper combines the thermal elastic hydrodynamic lubrication(TEHL) analysis with the loaded tooth contact analysis(LTCA) to predict the slide friction efficiency of the spur gear. LTCA is used to calculate the normal load and kinematics of the discrete contact points for the TEHL. The multi-level method, multi-level multi-integration (MIMI) approach and the sequential column sweeping for solving the pressure, elastic deformation and the temperature of the lubricated regions are used alternatively. The results show that when the change of tooth load is small, the effect of the load to the friction coefficient can be ignored; but the larger increase of the load will lead to reduced friction coefficient.
2015, 34(3): 334-338.
doi: 10.13433/j.cnki.1003-8728.2015.0302
Abstract:
The magnetic gears have the characteristics of low stiffness, which is normally regarded as the main barrier for their widespread application in the systems with high-bandwidth dynamic transients. This paper aimed to propose a control scheme of servo drive system with magnetic gears. Firstly, a representative physical and mathematical model under a specific load was built. Then the state observer and pole placement of modern control theory were used to build a closed loop control system to realize the desired dynamics response. More specifically speaking, it mainly included the design principle, the control algorithm, the example and the computer simulation. Simulation results verified that the pole placement achieves better dynamic performance of the system, and the state observer can successfully observe those state variables that cannot be gotten directly from the original system.
The magnetic gears have the characteristics of low stiffness, which is normally regarded as the main barrier for their widespread application in the systems with high-bandwidth dynamic transients. This paper aimed to propose a control scheme of servo drive system with magnetic gears. Firstly, a representative physical and mathematical model under a specific load was built. Then the state observer and pole placement of modern control theory were used to build a closed loop control system to realize the desired dynamics response. More specifically speaking, it mainly included the design principle, the control algorithm, the example and the computer simulation. Simulation results verified that the pole placement achieves better dynamic performance of the system, and the state observer can successfully observe those state variables that cannot be gotten directly from the original system.
2015, 34(3): 339-343.
doi: 10.13433/j.cnki.1003-8728.2015.0303
Abstract:
Taking Chinese high-speed railway bridge as an example, a reasonable double degree-of-freedom mechanical model of FPB isolation bridge was established, and the isolation effect of FPB isolation bridge was studied through numerical simulation. The results show that the model can more accurately calculate the seismic response of isolated bridges; with different seismic waves, the friction coefficient of FPB has different effects on the displacement response of the bridge girder; the isolation rates of acceleration of bridge girder, shear of the bottom of pier, displacement of the top of pier can reach 40%、35%、50% respectively; shear of the bottom of pier and displacement of bridge girder have a large increase when the height of pier increases.
Taking Chinese high-speed railway bridge as an example, a reasonable double degree-of-freedom mechanical model of FPB isolation bridge was established, and the isolation effect of FPB isolation bridge was studied through numerical simulation. The results show that the model can more accurately calculate the seismic response of isolated bridges; with different seismic waves, the friction coefficient of FPB has different effects on the displacement response of the bridge girder; the isolation rates of acceleration of bridge girder, shear of the bottom of pier, displacement of the top of pier can reach 40%、35%、50% respectively; shear of the bottom of pier and displacement of bridge girder have a large increase when the height of pier increases.
2015, 34(3): 344-347.
doi: 10.13433/j.cnki.1003-8728.2015.0304
Abstract:
Aimed at the weakness of the motor drive and low efficiency in the research on a quadruped robot, a coupled driven leg mechanism is proposed to build a four-leg robot. The coupled driven hip joint with a complex motion pattern is designed, which can produce a multi-angle composite motion by selecting different rotation direction and speed in the two motors in hip joint. A quadruped robot with 12 active degrees of freedom is developed with this leg mechanism. According to the static stability margin, static walking gait is designed. The motion control system of the robot is built with distributed CAN bus. The walking experiment shows that the robot can move smoothly and meet the design requirements.
Aimed at the weakness of the motor drive and low efficiency in the research on a quadruped robot, a coupled driven leg mechanism is proposed to build a four-leg robot. The coupled driven hip joint with a complex motion pattern is designed, which can produce a multi-angle composite motion by selecting different rotation direction and speed in the two motors in hip joint. A quadruped robot with 12 active degrees of freedom is developed with this leg mechanism. According to the static stability margin, static walking gait is designed. The motion control system of the robot is built with distributed CAN bus. The walking experiment shows that the robot can move smoothly and meet the design requirements.
2015, 34(3): 348-351.
doi: 10.13433/j.cnki.1003-8728.2015.0305
Abstract:
Blade size can greatly influence the work efficiency of turbine. In order to analyze heat deformation of turbine blades under complex working conditions, a model coupling gas-heat-solid field was established to simulate the three dimensional flow fields. The temperature distribution and the corresponding deformation caused by thermal effect were acquired by changing the flow ratio between main stream and coolant. The results show that the deformation as a whole characterize as bending from the pressure side to suction side, and wich in vertical direction are much larger than that in horizontal direction. The largest deformation locates in the leading edge of blade tip. The thermal deformation is less sensitive with the decreasing of surface temperature. The thermal deformation can be approximately estimated by the vertical one. The present model can predict the thermal deformation of blade and provide the deformation for design and modify the blade dimensions.
Blade size can greatly influence the work efficiency of turbine. In order to analyze heat deformation of turbine blades under complex working conditions, a model coupling gas-heat-solid field was established to simulate the three dimensional flow fields. The temperature distribution and the corresponding deformation caused by thermal effect were acquired by changing the flow ratio between main stream and coolant. The results show that the deformation as a whole characterize as bending from the pressure side to suction side, and wich in vertical direction are much larger than that in horizontal direction. The largest deformation locates in the leading edge of blade tip. The thermal deformation is less sensitive with the decreasing of surface temperature. The thermal deformation can be approximately estimated by the vertical one. The present model can predict the thermal deformation of blade and provide the deformation for design and modify the blade dimensions.
2015, 34(3): 352-355.
doi: 10.13433/j.cnki.1003-8728.2015.0306
Abstract:
In order to aid the walking training of hemiplegia patients, a kind of four degrees of freedom pelvis position control mechanism of walking aided training robot is put forward. Based on the principle and components of the mechanism, the dynamics equations of pelvis plane mechanism are established with Kane's method. The kinematics simulation calculations are carried out according to the motion law of pelvis position. The displacement, velocity and acceleration curves of the mechanism motion linkages are presented. By solving dynamics equations the drive forces curves are obtained. The results show that the mechanism can implement position control of human pelvis. By actuating the moving mechanisms of x and z directions and expansions of two linkages of pelvis plane mechanism, the pelvis motions with four degrees of freedom in human walking training can be realized.
In order to aid the walking training of hemiplegia patients, a kind of four degrees of freedom pelvis position control mechanism of walking aided training robot is put forward. Based on the principle and components of the mechanism, the dynamics equations of pelvis plane mechanism are established with Kane's method. The kinematics simulation calculations are carried out according to the motion law of pelvis position. The displacement, velocity and acceleration curves of the mechanism motion linkages are presented. By solving dynamics equations the drive forces curves are obtained. The results show that the mechanism can implement position control of human pelvis. By actuating the moving mechanisms of x and z directions and expansions of two linkages of pelvis plane mechanism, the pelvis motions with four degrees of freedom in human walking training can be realized.
2015, 34(3): 356-360.
doi: 10.13433/j.cnki.1003-8728.2015.0307
Abstract:
This paper uses the alternated frequency/time method to calculate the stable response of a dry friction constrained structure and the energy dissipated by dry friction, thus determining the stick-slip state of its contact spot. The calculation results show that the stable amplitude of the constrained structure does not have a minimum when the energy dissipated by dry friction reaches its maximum; however, it is a more effective method to evaluate the vibration reduction performance of dry friction with the stick-slip ratio of the contact point. Finally, the effect of the structural damping on selecting the stick-slip ratio is analyzed.
This paper uses the alternated frequency/time method to calculate the stable response of a dry friction constrained structure and the energy dissipated by dry friction, thus determining the stick-slip state of its contact spot. The calculation results show that the stable amplitude of the constrained structure does not have a minimum when the energy dissipated by dry friction reaches its maximum; however, it is a more effective method to evaluate the vibration reduction performance of dry friction with the stick-slip ratio of the contact point. Finally, the effect of the structural damping on selecting the stick-slip ratio is analyzed.
2015, 34(3): 361-365.
doi: 10.13433/j.cnki.1003-8728.2015.0308
Abstract:
The breech mechanism is always damaged by the serious impact during the process of breechblock-opening. Aim at the dynamic stresses response, a nonlinear structural dynamic model of artillery's breech mechanism has been established based on the contact finite element theory with ABAQUS to simulate the complex contact and impact in the breech mechanism. In the model, the implicit time integration method is used to simulate the process of opening block to study the dynamic stresses on the main parts of artillery's breech mechanism when the opening latch cam has an impact on the opening latch plate in the process of counter-recoiling. The dynamic stresses on the main parts can be obtained by analyzing the results. The results show that the parts of artillery can satisfy the strength requirement of material and the stress on extractor is big, so that the calculation results can provide reference for changing the structural design of crank and breechblock.
The breech mechanism is always damaged by the serious impact during the process of breechblock-opening. Aim at the dynamic stresses response, a nonlinear structural dynamic model of artillery's breech mechanism has been established based on the contact finite element theory with ABAQUS to simulate the complex contact and impact in the breech mechanism. In the model, the implicit time integration method is used to simulate the process of opening block to study the dynamic stresses on the main parts of artillery's breech mechanism when the opening latch cam has an impact on the opening latch plate in the process of counter-recoiling. The dynamic stresses on the main parts can be obtained by analyzing the results. The results show that the parts of artillery can satisfy the strength requirement of material and the stress on extractor is big, so that the calculation results can provide reference for changing the structural design of crank and breechblock.
2015, 34(3): 366-369.
doi: 10.13433/j.cnki.1003-8728.2015.0309
Abstract:
The static gas-lubricated Reynolds equation of a three-tilting-pads journal bearing was solved with the finite difference method to obtain the gas film pressure distribution of the bearing. Considering bearing carrying a constant load,the maximum gas-film pressure when the velocity of rotor is fixed and the lift-off speeds of the rotor corresponding to different bearing clearances were calculated. The changes of eccentricity ratio and tilt angle of pads in the process of the velocity of rotor increasing from lift-off speed to the working speed were also analyzed. The results show that with the bearing clearance increasing, the lift-off speed, the eccentricity ratio and the tilt angle of pads are increased while the maximum gas-film pressure is decreased.
The static gas-lubricated Reynolds equation of a three-tilting-pads journal bearing was solved with the finite difference method to obtain the gas film pressure distribution of the bearing. Considering bearing carrying a constant load,the maximum gas-film pressure when the velocity of rotor is fixed and the lift-off speeds of the rotor corresponding to different bearing clearances were calculated. The changes of eccentricity ratio and tilt angle of pads in the process of the velocity of rotor increasing from lift-off speed to the working speed were also analyzed. The results show that with the bearing clearance increasing, the lift-off speed, the eccentricity ratio and the tilt angle of pads are increased while the maximum gas-film pressure is decreased.
2015, 34(3): 370-376.
doi: 10.13433/j.cnki.1003-8728.2015.0310
Abstract:
The inevitable size deviation in machining process induces the change of stress cycle state in fixed ring. Aiming at the change, the concept of equivalent loading state was proposed. Based on the equivalent loading state and combined Lundberg-palmgren (L-P) life theory with Miner's fatigue damage accumulationhypothesis, a modified L-P life model, including size deviation, was developed. By means of the life model, the effects of the size deviation, external load, and radial clearance were investigated in 6008 type deep groove ball bearing. Considering the statistical distribution of size deviation, statistics analysis of predicted results was conducted. The analytic results of the modified life model were compared with the experimental data of related literature, some conclusions were drawn as follows: 1) the life factor decrease with the increasing of size deviation; 2) the effect of the size deviation gradually decreases with the increasing of external load; 3) in particular negative clearance, the effect of the size deviation is worst; 4) if the size deviation is normally distributed, the distribution of life factors also obeys normal distribution.
The inevitable size deviation in machining process induces the change of stress cycle state in fixed ring. Aiming at the change, the concept of equivalent loading state was proposed. Based on the equivalent loading state and combined Lundberg-palmgren (L-P) life theory with Miner's fatigue damage accumulationhypothesis, a modified L-P life model, including size deviation, was developed. By means of the life model, the effects of the size deviation, external load, and radial clearance were investigated in 6008 type deep groove ball bearing. Considering the statistical distribution of size deviation, statistics analysis of predicted results was conducted. The analytic results of the modified life model were compared with the experimental data of related literature, some conclusions were drawn as follows: 1) the life factor decrease with the increasing of size deviation; 2) the effect of the size deviation gradually decreases with the increasing of external load; 3) in particular negative clearance, the effect of the size deviation is worst; 4) if the size deviation is normally distributed, the distribution of life factors also obeys normal distribution.
2015, 34(3): 377-380.
doi: 10.13433/j.cnki.1003-8728.2015.0311
Abstract:
In the process of liner hanging cementing, the drill pipe will have axial deformation due to the joint effect of multi-loading. Before the cementing construction procedure, if the drill pipe lifting distance is too short, the drill pipe and the liner hanger may close again in the follow-up actions, thus blocking the drilling tool due to the unsuccessful releasing of the hanger when pulling the drill tool out of the hole. By analyzing the drill pipe loading conditions in the liner cementing process for plumb shaft, based on the features that the drill adapter is different from the drill pipe structure, this paper puts forward an engineering calculation model for the maximum elongation of drill adapter with comprehensive consideration of factors including structure field, temperature field, pressure field and so on. With this model, the drill pipe elongation in liner cementing process can be calculated precisely to minimize the sticking of tool. The analysis results show that the drill pipe has a maximum axial elongation in stationary state and the temperature field has largest influence on drill adapter elongation, while the pressure field has the smallest influence. The temperature has smaller influence on drill adapter than on pipe column of the same size.
In the process of liner hanging cementing, the drill pipe will have axial deformation due to the joint effect of multi-loading. Before the cementing construction procedure, if the drill pipe lifting distance is too short, the drill pipe and the liner hanger may close again in the follow-up actions, thus blocking the drilling tool due to the unsuccessful releasing of the hanger when pulling the drill tool out of the hole. By analyzing the drill pipe loading conditions in the liner cementing process for plumb shaft, based on the features that the drill adapter is different from the drill pipe structure, this paper puts forward an engineering calculation model for the maximum elongation of drill adapter with comprehensive consideration of factors including structure field, temperature field, pressure field and so on. With this model, the drill pipe elongation in liner cementing process can be calculated precisely to minimize the sticking of tool. The analysis results show that the drill pipe has a maximum axial elongation in stationary state and the temperature field has largest influence on drill adapter elongation, while the pressure field has the smallest influence. The temperature has smaller influence on drill adapter than on pipe column of the same size.
2015, 34(3): 381-385.
doi: 10.13433/j.cnki.1003-8728.2015.0312
Abstract:
According to the uncertainty existed in the metal structure of the bridge crane, the non-probabilistic reliability index has been derived based on the convex model of the set-theory. The strength of the metal structure of the bridge crane DQ28.5m_75t_A6 is analyzed with finite element method and the stress responses of dangerous point on the structure are obtained. The samples of stresses and uncertain parameter of structure dangerous point are gained through design of experiment (DOE), and the explicit expression of the stress response with respect to uncertain parameter is obtained with the support vector machines (SVM) method, and then the non-probability reliability of this structure is achieved. The result shows that the method can be used to solve the problem of non-probabilistic reliability of metal structure.
According to the uncertainty existed in the metal structure of the bridge crane, the non-probabilistic reliability index has been derived based on the convex model of the set-theory. The strength of the metal structure of the bridge crane DQ28.5m_75t_A6 is analyzed with finite element method and the stress responses of dangerous point on the structure are obtained. The samples of stresses and uncertain parameter of structure dangerous point are gained through design of experiment (DOE), and the explicit expression of the stress response with respect to uncertain parameter is obtained with the support vector machines (SVM) method, and then the non-probability reliability of this structure is achieved. The result shows that the method can be used to solve the problem of non-probabilistic reliability of metal structure.
2015, 34(3): 386-392.
doi: 10.13433/j.cnki.1003-8728.2015.0313
Abstract:
An axisymmetric finite element model for O-ring was built based on the soft-ware Abaqus, and its seal performance in reciprocating dynamic seals and its mechanical properties under different conditions were analyzed. The results show that the biggest contact stress on the primary seal face and Von Mises stress's acting position change with the direction of movement and the size fluctuated over time. When reciprocating speed is less than 0.25 m/s, the friction force and shear stress are almost not affected by speed. With the friction coefficient and medium presure increased, friction force and shear stress become higher sensitive for speed. Medium presure and friction coefficient have a great impact on friction force and shear stress. Friction force and shear stress change simultaneously. The Von Mises stress and shear stress in outer journey are bigger than the inner journey, and outer journey is more likely to cause fatigue and shear failure. The friction force of O-ring in dynamic seal suffered a sharp rise when compression ratio get to a certain value, so too large compression ratio should not be adopted in dynamic seal.
An axisymmetric finite element model for O-ring was built based on the soft-ware Abaqus, and its seal performance in reciprocating dynamic seals and its mechanical properties under different conditions were analyzed. The results show that the biggest contact stress on the primary seal face and Von Mises stress's acting position change with the direction of movement and the size fluctuated over time. When reciprocating speed is less than 0.25 m/s, the friction force and shear stress are almost not affected by speed. With the friction coefficient and medium presure increased, friction force and shear stress become higher sensitive for speed. Medium presure and friction coefficient have a great impact on friction force and shear stress. Friction force and shear stress change simultaneously. The Von Mises stress and shear stress in outer journey are bigger than the inner journey, and outer journey is more likely to cause fatigue and shear failure. The friction force of O-ring in dynamic seal suffered a sharp rise when compression ratio get to a certain value, so too large compression ratio should not be adopted in dynamic seal.
2015, 34(3): 393-397.
doi: 10.13433/j.cnki.1003-8728.2015.0314
Abstract:
The wave-induced motion of the floating crane can produce complicated nonlinear dynamic characters, which maybe cause some accidents on the sea. Regarding the rope as a flexible body and considering the coupled motion of the cargo and the ship, a virtual prototype model of the floating crane was established based on flexible multi-body dynamics theory. From the simulation of the floating crane that carries out the supplement at sea, the relevant dynamic characters were calculated. The results indicate that the safety operation of the floating crane depends on the position of the ships, wave frequency, the initial length of cable and unreeling speed.
The wave-induced motion of the floating crane can produce complicated nonlinear dynamic characters, which maybe cause some accidents on the sea. Regarding the rope as a flexible body and considering the coupled motion of the cargo and the ship, a virtual prototype model of the floating crane was established based on flexible multi-body dynamics theory. From the simulation of the floating crane that carries out the supplement at sea, the relevant dynamic characters were calculated. The results indicate that the safety operation of the floating crane depends on the position of the ships, wave frequency, the initial length of cable and unreeling speed.
2015, 34(3): 398-403.
doi: 10.13433/j.cnki.1003-8728.2015.0315
Abstract:
Vertical shearing machine is one of the key equipments of the Spent Fuel Post Processing, the feeding system has a significant impact on the performance of shearing machine. The reliability analysis method based on fault tree analysis(FTA) and working principle is proposed in this paper. The MATLAB software is adopted to develop a visual platform, which is used to process test data efficiently and calculate the reliability parameters such as reliability, failure rate, mean time to failure(MTTF) accurately. The results show that the pin and driving draft are the vital parts of feeding system and the irradiation environment strongly influences the feeding system. With this reliability data analysis platform, the testing data can be computed and processed visually and automatically in real time.
Vertical shearing machine is one of the key equipments of the Spent Fuel Post Processing, the feeding system has a significant impact on the performance of shearing machine. The reliability analysis method based on fault tree analysis(FTA) and working principle is proposed in this paper. The MATLAB software is adopted to develop a visual platform, which is used to process test data efficiently and calculate the reliability parameters such as reliability, failure rate, mean time to failure(MTTF) accurately. The results show that the pin and driving draft are the vital parts of feeding system and the irradiation environment strongly influences the feeding system. With this reliability data analysis platform, the testing data can be computed and processed visually and automatically in real time.
2015, 34(3): 404-407.
doi: 10.13433/j.cnki.1003-8728.2015.0316
Abstract:
The textured port pair in axial piston pump is considered as the research object in this paper, its steady force and transient force is analyzed in detail, its mathematical model and simulation model based on the Simulink software are established, and the oil film thickness is taken as the parameter to be examined. The results show that comparing with the ordinary port plate pair, the textured port plate pair has smaller change in the oil film thickness when the pressure is suddenly changed, and the dynamic performance of the oil film thickness has been enhanced to a certain extent. The dynamic characteristic of the oil film thickness is related to its oil film stiffness, the larger the oil film stiffness is, the more benefits is obtained for dynamic characteristics of the port plate pair. The compression effect of the textured port plate pair can avoid its solid contact when the oil film thickness is approximately zero.
The textured port pair in axial piston pump is considered as the research object in this paper, its steady force and transient force is analyzed in detail, its mathematical model and simulation model based on the Simulink software are established, and the oil film thickness is taken as the parameter to be examined. The results show that comparing with the ordinary port plate pair, the textured port plate pair has smaller change in the oil film thickness when the pressure is suddenly changed, and the dynamic performance of the oil film thickness has been enhanced to a certain extent. The dynamic characteristic of the oil film thickness is related to its oil film stiffness, the larger the oil film stiffness is, the more benefits is obtained for dynamic characteristics of the port plate pair. The compression effect of the textured port plate pair can avoid its solid contact when the oil film thickness is approximately zero.
2015, 34(3): 408-412.
doi: 10.13433/j.cnki.1003-8728.2015.0317
Abstract:
The existing solving algorithm of intersection curve cutting trajectory for latticed-shell steel structure joints is complex and the cutting precision is low. In order to improve the manufacturing efficiency and quality of steel structure joint, a kind of approach for generating and checking intersection curve cutting trajectory of complex-section steel structure joint components is presented. Firstly, a real-time solving algorithm of complex intersection curve is derived from the movement of branch pipe generatrix with the analytical model, then the processing checking file of cutting trajectory is generated from the distance of section vertex on adjacent component. The proposed approach is applied to acquire rough interpolation trajectory data so that provid cutting trajectory data for a kind of 5 degrees of freedom hybrid robot.
The existing solving algorithm of intersection curve cutting trajectory for latticed-shell steel structure joints is complex and the cutting precision is low. In order to improve the manufacturing efficiency and quality of steel structure joint, a kind of approach for generating and checking intersection curve cutting trajectory of complex-section steel structure joint components is presented. Firstly, a real-time solving algorithm of complex intersection curve is derived from the movement of branch pipe generatrix with the analytical model, then the processing checking file of cutting trajectory is generated from the distance of section vertex on adjacent component. The proposed approach is applied to acquire rough interpolation trajectory data so that provid cutting trajectory data for a kind of 5 degrees of freedom hybrid robot.
2015, 34(3): 413-417.
doi: 10.13433/j.cnki.1003-8728.2015.0318
Abstract:
In computer numerical control (CNC) machining for triangular mesh surface, the estimation accuracy of curvature on triangular mesh surface is critical to tool path planning and quality of machining. An accurate algorithm is proposed for evaluating the nodal curvature for triangular mesh surface. Considering the effect of triangular shape on the nodal normal vector, a triangular shape factor is introduced, and it is integrated by weighing the surrounding areas so that the nodal normal vector is determined more precisely. The algorithm can effectively improve the accuracy of nodal curvature estimation for triangular mesh, thus effectively improve the calculation accuracy of cutting location points and machining precision of triangular mesh surface.
In computer numerical control (CNC) machining for triangular mesh surface, the estimation accuracy of curvature on triangular mesh surface is critical to tool path planning and quality of machining. An accurate algorithm is proposed for evaluating the nodal curvature for triangular mesh surface. Considering the effect of triangular shape on the nodal normal vector, a triangular shape factor is introduced, and it is integrated by weighing the surrounding areas so that the nodal normal vector is determined more precisely. The algorithm can effectively improve the accuracy of nodal curvature estimation for triangular mesh, thus effectively improve the calculation accuracy of cutting location points and machining precision of triangular mesh surface.
2015, 34(3): 418-422.
doi: 10.13433/j.cnki.1003-8728.2015.0319
Abstract:
The priori knowledge of each tool wear state usually can't be completely attained in practical processing, but the priori knowledge of blunt state can be easily attained. In view of this situation, a tool wear monitoring method with incomplete knowledge based on continuous hidden Markov model (CHMM) was proposed in this paper. The cutting force signals were measured as monitoring signals by multi-sensors. The wear features were extracted by wavelet package decomposition technology, and the normalization features of blunt states were inputted to CHMM to construct monitoring models. The tool performance value (PV) can be got through calculating the log-likelihood between unknown state feature vectors and monitoring model, which can achieve the aim of tool condition evaluation. The whole life-cycle wear data of milling cutter were used to validate the effectiveness of the proposed method. The experimental result shows that this method can carry out an accurate assessment of the tool wear when only having the priori knowledge of tool blunt state, and the model has fast learning ability and needs few training samples.
The priori knowledge of each tool wear state usually can't be completely attained in practical processing, but the priori knowledge of blunt state can be easily attained. In view of this situation, a tool wear monitoring method with incomplete knowledge based on continuous hidden Markov model (CHMM) was proposed in this paper. The cutting force signals were measured as monitoring signals by multi-sensors. The wear features were extracted by wavelet package decomposition technology, and the normalization features of blunt states were inputted to CHMM to construct monitoring models. The tool performance value (PV) can be got through calculating the log-likelihood between unknown state feature vectors and monitoring model, which can achieve the aim of tool condition evaluation. The whole life-cycle wear data of milling cutter were used to validate the effectiveness of the proposed method. The experimental result shows that this method can carry out an accurate assessment of the tool wear when only having the priori knowledge of tool blunt state, and the model has fast learning ability and needs few training samples.
2015, 34(3): 423-428.
doi: 10.13433/j.cnki.1003-8728.2015.0320
Abstract:
For having good physical and mechanical properties, SiC monocrystal is widely used in high-power devices and IC industry. However, the high hardness and brittleness make the cutting process of SiC monocrystal very difficultly. The single input and single output system consists of part feed rate and cutting force are analyzed; a minimum variance self-tuning controller is designed to make sure the process will be stable and more efficiency. Firstly, system order is determined through F-test. Then the system model parameters are estimated, the differential equation between the cutting force and the part feed rate is developed. The experiments with reference force (square wave and sine wave signal) are conducted and the results show that the proposed cutting force controller can control the feed rate well to track the different reference cutting forces, and the proposed controller has a robotic ability. The results indicate that the proposed cutting force controller can improve the surface integrity for SiC monocrystal wafer and keep the cutting process stable.
For having good physical and mechanical properties, SiC monocrystal is widely used in high-power devices and IC industry. However, the high hardness and brittleness make the cutting process of SiC monocrystal very difficultly. The single input and single output system consists of part feed rate and cutting force are analyzed; a minimum variance self-tuning controller is designed to make sure the process will be stable and more efficiency. Firstly, system order is determined through F-test. Then the system model parameters are estimated, the differential equation between the cutting force and the part feed rate is developed. The experiments with reference force (square wave and sine wave signal) are conducted and the results show that the proposed cutting force controller can control the feed rate well to track the different reference cutting forces, and the proposed controller has a robotic ability. The results indicate that the proposed cutting force controller can improve the surface integrity for SiC monocrystal wafer and keep the cutting process stable.
2015, 34(3): 429-433.
doi: 10.13433/j.cnki.1003-8728.2015.0321
Abstract:
The continuous cutting technology to architectural model with EPS (Expandable Polystyrene) is provided. To solve the interference problem between the outline surface and hot cutting-wire in the cutting process, the STL (Standard Template Library) model projection profile method is adopted. The slicing algorithm based on the grouping matrix and the union of slice contour algorithm is proposed to continuously cut the outline model. The local topological relations in each group are established to improve the efficiency of slicing cutting. The automatic programming system with Visual C++ 6.0 based on the STL model is developed, which used the 5-degrees of freedom CNC thermal device to cut the model. The experiment shows that this technology can cut the outline architectural model efficiently and accurately.
The continuous cutting technology to architectural model with EPS (Expandable Polystyrene) is provided. To solve the interference problem between the outline surface and hot cutting-wire in the cutting process, the STL (Standard Template Library) model projection profile method is adopted. The slicing algorithm based on the grouping matrix and the union of slice contour algorithm is proposed to continuously cut the outline model. The local topological relations in each group are established to improve the efficiency of slicing cutting. The automatic programming system with Visual C++ 6.0 based on the STL model is developed, which used the 5-degrees of freedom CNC thermal device to cut the model. The experiment shows that this technology can cut the outline architectural model efficiently and accurately.
2015, 34(3): 434-439.
doi: 10.13433/j.cnki.1003-8728.2015.0322
Abstract:
The discrete element method (DEM) model which describes the friction and wear behavior of the interface between Sialon ceramic tool and chip was established. Based on the prestressed cutting principle, a specific preload device was designed for the prestressed turning of GH4169 ring parts; experimental validations were carried out with Sialon ceramic tools. Combining the experiments and DEM simulation, the cutting force and tool wear were investigated in different prestress conditions. It is found that the prestress shows little effect on wear appearances and mechanisms of ceramic tool. Both experiments and DEM simulation indicate that prestressed cutting method is benefit for the wear of Sialon ceramic tools. Moreover, within a certain range of prestress, higher cutting speed effectively results in slighter tool wear. The DEM simulation results are in good agreement with the experiments, which are further validated that DEM is feasible to simulate the tool wear behaviors.
The discrete element method (DEM) model which describes the friction and wear behavior of the interface between Sialon ceramic tool and chip was established. Based on the prestressed cutting principle, a specific preload device was designed for the prestressed turning of GH4169 ring parts; experimental validations were carried out with Sialon ceramic tools. Combining the experiments and DEM simulation, the cutting force and tool wear were investigated in different prestress conditions. It is found that the prestress shows little effect on wear appearances and mechanisms of ceramic tool. Both experiments and DEM simulation indicate that prestressed cutting method is benefit for the wear of Sialon ceramic tools. Moreover, within a certain range of prestress, higher cutting speed effectively results in slighter tool wear. The DEM simulation results are in good agreement with the experiments, which are further validated that DEM is feasible to simulate the tool wear behaviors.
2015, 34(3): 440-444.
doi: 10.13433/j.cnki.1003-8728.2015.0323
Abstract:
The novel algorithm for recognizing hole axis with different poses based on the computational geometry is studied. The edge of a hole will show as an ellipse by perspective projection. The ellipse fitting based on the algebraic distances could ensure the stability of fitting results. And the fitting results are iterated and optimized by adding the ellipse definition constraints. This would avoid interference due to exception points and incomplete sample points. The spatial geometry model was established by using the spatial geometry analysis. The formulas were deduced with analyzing plane normal vector and similar triangles. The simulation and real image results are presented with the high precision and practical algorithm.
The novel algorithm for recognizing hole axis with different poses based on the computational geometry is studied. The edge of a hole will show as an ellipse by perspective projection. The ellipse fitting based on the algebraic distances could ensure the stability of fitting results. And the fitting results are iterated and optimized by adding the ellipse definition constraints. This would avoid interference due to exception points and incomplete sample points. The spatial geometry model was established by using the spatial geometry analysis. The formulas were deduced with analyzing plane normal vector and similar triangles. The simulation and real image results are presented with the high precision and practical algorithm.
2015, 34(3): 445-448.
doi: 10.13433/j.cnki.1003-8728.2015.0324
Abstract:
Comparing with the strong background noise, the gear's vibration signal is usually very weak when occurring the incipient fault of gear box, and with concealed impulse component reflecting the operating state of the gearbox. The vibration feature is very difficult to extract through frequency spectrum or envelope spectrum analysis. The minimum entropy deconvolution (MED) was adopted to carry out the fault diagnosis of gear box for rubber refiner. The vibration signal of gearbox was firstly filtered with the MED method, then the filtered signal was demodulated with the envelope spectrum, and the fault feature of root slight crack of gear 8(z8=28) on the shaft five was successfully extracted. Therefore, the incipient fault diagnosis of the gear box was realized. The application results verify the effectiveness and advantage of MED method.
Comparing with the strong background noise, the gear's vibration signal is usually very weak when occurring the incipient fault of gear box, and with concealed impulse component reflecting the operating state of the gearbox. The vibration feature is very difficult to extract through frequency spectrum or envelope spectrum analysis. The minimum entropy deconvolution (MED) was adopted to carry out the fault diagnosis of gear box for rubber refiner. The vibration signal of gearbox was firstly filtered with the MED method, then the filtered signal was demodulated with the envelope spectrum, and the fault feature of root slight crack of gear 8(z8=28) on the shaft five was successfully extracted. Therefore, the incipient fault diagnosis of the gear box was realized. The application results verify the effectiveness and advantage of MED method.
2015, 34(3): 449-453.
doi: 10.13433/j.cnki.1003-8728.2015.0325
Abstract:
The attitude measurement for the threaded probe end is one of the key techniques in the screw comprehensive measurement that is based on the digital contour envelope. An attitude measurement system of the threaded probe end was designed. To ensure the measuring precision of the attitude measurement, it is necessary to correct the nonlinearity of the measuring system. The transfer function of the signal sampling system was calibrated and the nonlinear part was separated with the linear part. The nonlinear part was corrected by using the correction algorithm after the transform function of the nonlinear part was solved. The results showed that the angular displacement nonlinear error decreased 1'17.25" and the nonlinear error of the measuring system was less than 0.12% after the nonlinearity had been corrected, and the precision met the requirement of the system.
The attitude measurement for the threaded probe end is one of the key techniques in the screw comprehensive measurement that is based on the digital contour envelope. An attitude measurement system of the threaded probe end was designed. To ensure the measuring precision of the attitude measurement, it is necessary to correct the nonlinearity of the measuring system. The transfer function of the signal sampling system was calibrated and the nonlinear part was separated with the linear part. The nonlinear part was corrected by using the correction algorithm after the transform function of the nonlinear part was solved. The results showed that the angular displacement nonlinear error decreased 1'17.25" and the nonlinear error of the measuring system was less than 0.12% after the nonlinearity had been corrected, and the precision met the requirement of the system.
2015, 34(3): 454-458.
doi: 10.13433/j.cnki.1003-8728.2015.0326
Abstract:
With double symmetrical rectangle relief grooves as an example, from the accurate calculation of closed volume changed in discharge side of gear pump and the simulation results of trapped oil pressure, the calculation formula of instantaneous flow rates were derived under ideal state and actual state, and then the flow quality was analyzed. Results indicated that, in the ideal state, the flow quality was greatly improved by relief groove, the average flow rate was increased by 1.6%, and the non-uniform flow coefficient was reduced by 65.3%; in the actual state, the flow quality was also improved by relief groove, but the improvement effect was slightly declined; the two trapped oil regions as a whole in large backlash gap only was a rough approximation, and the obvious phenomenon of trapped oil was also occurred in the meshing range of a single tooth, etc. It is summarized that the classic definition of trapped oil phenomenon limited in the meshing range of two teeth should be corrected, and it is necessary to consider the trapped oil pressure in the calculation of instantaneous flow rate.
With double symmetrical rectangle relief grooves as an example, from the accurate calculation of closed volume changed in discharge side of gear pump and the simulation results of trapped oil pressure, the calculation formula of instantaneous flow rates were derived under ideal state and actual state, and then the flow quality was analyzed. Results indicated that, in the ideal state, the flow quality was greatly improved by relief groove, the average flow rate was increased by 1.6%, and the non-uniform flow coefficient was reduced by 65.3%; in the actual state, the flow quality was also improved by relief groove, but the improvement effect was slightly declined; the two trapped oil regions as a whole in large backlash gap only was a rough approximation, and the obvious phenomenon of trapped oil was also occurred in the meshing range of a single tooth, etc. It is summarized that the classic definition of trapped oil phenomenon limited in the meshing range of two teeth should be corrected, and it is necessary to consider the trapped oil pressure in the calculation of instantaneous flow rate.
2015, 34(3): 459-463.
doi: 10.13433/j.cnki.1003-8728.2015.0327
Abstract:
Through road test, 7 dampers with serious noise problem (Class A) and 6 dampers without noise problem (class N) are determined. The damping force signal and the acceleration signal with and without external connecting sleeve are obtained by the indicator diagram test and vibration-noise test. Firstly, comparative analysis of acceleration signal and damping force signal characteristics of 15# and 47# are carried out. Then, statistical analyses of all shock absorbers are performed in time domain and frequency domain. Time domain analysis shows that the peak accelerations of class A damper were generally higher than class N damper, and the frequency range with peak acceleration is 80~250 Hz. Without external connection sleeve, the damping force abnormal fluctuations occurred when it is 0.1671×T/4 s past the compression-recovery reversing point, and the valve opening is the causation. Frequency domain analysis show that the RMS value, max value and average value of damping force signal of class A damper are general greater than that of class N damper. The valve opening status of class A damper is greater than that of class N damper.
Through road test, 7 dampers with serious noise problem (Class A) and 6 dampers without noise problem (class N) are determined. The damping force signal and the acceleration signal with and without external connecting sleeve are obtained by the indicator diagram test and vibration-noise test. Firstly, comparative analysis of acceleration signal and damping force signal characteristics of 15# and 47# are carried out. Then, statistical analyses of all shock absorbers are performed in time domain and frequency domain. Time domain analysis shows that the peak accelerations of class A damper were generally higher than class N damper, and the frequency range with peak acceleration is 80~250 Hz. Without external connection sleeve, the damping force abnormal fluctuations occurred when it is 0.1671×T/4 s past the compression-recovery reversing point, and the valve opening is the causation. Frequency domain analysis show that the RMS value, max value and average value of damping force signal of class A damper are general greater than that of class N damper. The valve opening status of class A damper is greater than that of class N damper.
2015, 34(3): 464-471.
doi: 10.13433/j.cnki.1003-8728.2015.0328
Abstract:
In order to serve the interior designer of a passenger car and its buyers better, the evaluation model for its interior design is built with the Delphi technique improved by network and game theory. In addition, the improved Delphi technique is combined with the Fuzzy-Analytic Hierarchy Process. It has the three merits: firstly, with the improved Delphi technique, experts can spend less time on evaluating the interior design than with the traditional Delphi technique; secondly, the unreasonableness of the traditional grade quantitative value assignment method is eradicated; thirdly, the improved Delphi technique obviously reduces the subjectivity in the interior design evaluation. Finally, three models of convertible saloons are taken for example to verify the feasibility of the evaluation method.
In order to serve the interior designer of a passenger car and its buyers better, the evaluation model for its interior design is built with the Delphi technique improved by network and game theory. In addition, the improved Delphi technique is combined with the Fuzzy-Analytic Hierarchy Process. It has the three merits: firstly, with the improved Delphi technique, experts can spend less time on evaluating the interior design than with the traditional Delphi technique; secondly, the unreasonableness of the traditional grade quantitative value assignment method is eradicated; thirdly, the improved Delphi technique obviously reduces the subjectivity in the interior design evaluation. Finally, three models of convertible saloons are taken for example to verify the feasibility of the evaluation method.
2015, 34(3): 472-475.
doi: 10.13433/j.cnki.1003-8728.2015.0329
Abstract:
This paper establishes a constitutive model of composite structure with UMAT subroutine of ABAQUS based on three dimensional Hashin invalidation rules and two kinds of fatigue degradation models. Some fatigue tests of composite structures with one-fastener joint without interference fit are simulated, the predicted fatigue lives agree well with the test results which verify the correctness of proposed model and analying program. Consequently, the fatigue life of a one-fastener composite structure with different interference fits is predicted by the present method and the results indicate that the fatigue lives of composites structures can be increased by three times of its original ones with the interference fit level of 0.8% to 1.0%.
This paper establishes a constitutive model of composite structure with UMAT subroutine of ABAQUS based on three dimensional Hashin invalidation rules and two kinds of fatigue degradation models. Some fatigue tests of composite structures with one-fastener joint without interference fit are simulated, the predicted fatigue lives agree well with the test results which verify the correctness of proposed model and analying program. Consequently, the fatigue life of a one-fastener composite structure with different interference fits is predicted by the present method and the results indicate that the fatigue lives of composites structures can be increased by three times of its original ones with the interference fit level of 0.8% to 1.0%.
2015, 34(3): 476-480.
doi: 10.13433/j.cnki.1003-8728.2015.0330
Abstract:
To shorten the design cycle and enhance the overall performance of composite radome, a multidisciplinary optimization method is proposed. The optimization model is established and the optimization variables, objects and constraints are analyzed. An optimization scheme is proposed which takes the electrical properties as the objects and the mechanical properties as the constraints. The aperture integration-surface integration (AI-SI) method is employed to analysis its electrical properties while the finite element method (FEM) is employed to analysis its mechanical properties. The optimization process is established based on the multi-island genetic algorithm (MIGA). Numerical analysis of an example is carried out and the results show that the electrical properties of the radome are successfully improved under the ensurance of mechanical properties. The feasibility of the optimization method is validated.
To shorten the design cycle and enhance the overall performance of composite radome, a multidisciplinary optimization method is proposed. The optimization model is established and the optimization variables, objects and constraints are analyzed. An optimization scheme is proposed which takes the electrical properties as the objects and the mechanical properties as the constraints. The aperture integration-surface integration (AI-SI) method is employed to analysis its electrical properties while the finite element method (FEM) is employed to analysis its mechanical properties. The optimization process is established based on the multi-island genetic algorithm (MIGA). Numerical analysis of an example is carried out and the results show that the electrical properties of the radome are successfully improved under the ensurance of mechanical properties. The feasibility of the optimization method is validated.
2015, 34(3): 481-484.
doi: 10.13433/j.cnki.1003-8728.2015.0331
Abstract:
The fabrication technology of knitted-dapped metal rubber was introduced. The comparison of the static characteristic of knitted-dapped metal rubber with the ordinary one was made by carrying out the compression tests. The effect of the thickness and density on the compression deformation of knitted-dapped metal rubber was also studied. The results showed that knitted-dapped metal rubber was better than the ordinary metal rubber in many aspects, such as bearing capacity, range of vibration isolation and consistency of property. The stiffness of the knitted-dapped metal rubber increased and the linear range decreased with the increasing of density. The thickness hardly had any influence on the material's stiffness and the linear range, while the stiffness in the hardening stage would decreased with the increasing of thickness.
The fabrication technology of knitted-dapped metal rubber was introduced. The comparison of the static characteristic of knitted-dapped metal rubber with the ordinary one was made by carrying out the compression tests. The effect of the thickness and density on the compression deformation of knitted-dapped metal rubber was also studied. The results showed that knitted-dapped metal rubber was better than the ordinary metal rubber in many aspects, such as bearing capacity, range of vibration isolation and consistency of property. The stiffness of the knitted-dapped metal rubber increased and the linear range decreased with the increasing of density. The thickness hardly had any influence on the material's stiffness and the linear range, while the stiffness in the hardening stage would decreased with the increasing of thickness.
2015, 34(3): 485-488.
doi: 10.13433/j.cnki.1003-8728.2015.0332
Abstract:
To overcome the shortcomings of existing computer reconstruction algorithms, the efficient computer reconstruction algorithm was proposed based on the geometrical feature extraction and visualization simulation. According to the SEM results of titanium alloys, based on the geometrical feature extraction of grain contour and the visual design of two-dimensional microstructure, the computer reconstruction algorithm for two-dimensional microstructures of titanium alloy with polycrystalline topological structure is achieved.
To overcome the shortcomings of existing computer reconstruction algorithms, the efficient computer reconstruction algorithm was proposed based on the geometrical feature extraction and visualization simulation. According to the SEM results of titanium alloys, based on the geometrical feature extraction of grain contour and the visual design of two-dimensional microstructure, the computer reconstruction algorithm for two-dimensional microstructures of titanium alloy with polycrystalline topological structure is achieved.
2015, 34(3): 489-492.
doi: 10.13433/j.cnki.1003-8728.2015.0333
Abstract:
This paper applies ANSYS to implement the finite element analysis for the corner crack of the dimple riveting structure, which is a common structure in practice. By changing the structure's geometric thickness and the height of the dimple hole, the parameter sensitivity of the stress intensity factor is studied. The results of comparative analysis show that the crack front stress intensity factor of the dimple is proportional to the height of the dimple, and is inversely proportional to the structure thickness; and also, when the proportion of the dimple height to the structural thickness is a constant over 0.5, the front stress intensity factor of the crack can be approximately regarded as the same, if the dimple height and the structure thickness are synchronously and proportionally changed.
This paper applies ANSYS to implement the finite element analysis for the corner crack of the dimple riveting structure, which is a common structure in practice. By changing the structure's geometric thickness and the height of the dimple hole, the parameter sensitivity of the stress intensity factor is studied. The results of comparative analysis show that the crack front stress intensity factor of the dimple is proportional to the height of the dimple, and is inversely proportional to the structure thickness; and also, when the proportion of the dimple height to the structural thickness is a constant over 0.5, the front stress intensity factor of the crack can be approximately regarded as the same, if the dimple height and the structure thickness are synchronously and proportionally changed.
