最新刊期
期 12 ， 2021
- 摘要：Meshing stiffness calculation of fatigue pitting helical gear is an important basis of gear failure dynamics analysis. The finite element models of normal gears and fatigue pitting gears are established by using the finite element method to calculate the meshing stiffness of helical gears. Through the finite element model calculation，the normal contact force and comprehensive elastic deformation of the tooth surface are obtained. According to the calculation method of meshing stiffness，the single tooth meshing stiffness and multi tooth comprehensive meshing stiffness of the gear are obtained. The influence of different spalling length and width of pitting corrosion on the meshing stiffness of gears is analyzed. The results show that the spalling length and width have great influence on the meshing stiffness of gears，and the spalling length will affect the change area of meshing stiffness of gears. Through the fatigue pitting test，it shows that the reduction of gear meshing stiffness makes the gear vibration impact response increase.关键词：Helical gear;Pitting;Time varying meshing stiffness;Finite element method
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发布时间：2022-09-15 - 摘要：Crowned tooth can improve the meshing state between tooth surfaces and enhance the load capacity of harmonic gears. In order to reveal the deformation law of the flexspline with variable thickness of tooth ring formed by the radial modification of drum shape，a theoretical method of spatial deformation of the gear with variable neutral layer radius is proposed. The formulas of radial，circumferential and angular displacements of the neutral line of the gear ring with the axial midface radius changing are derived. A parametric solid unit element finite element model of cup type flexspline with real tooth profile is established，and the neutral line deformation in the forward，middle and back cross sections of the tooth ring is calculated by contact analysis. The finite element results of each section of the tooth ring agree well with the theoretical values. The spatial deformation characteristics of variable thickness tooth ring are studied by comparing with the model of equal thickness tooth ring. The results show that the nonlinear characteristics of the generatrix are aggravated by the variable thickness ring. The nonlinear characteristics of the generatrix in the long axis region from the middle section to the back section and the generatrix in the short axis region from the front section to the middle section are more significant.关键词：Variable thickness tooth ring;Flexspline;Harmonic gear;Spatial deformation;Solid unit finite element model
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发布时间：2022-09-15 - 摘要：A new type of point contact gear pair is proposed. Based on a tooth surface，the flexible contact trail is selected according to the design requirements，and the meshing pair gear is constructed，and the sliding coefficient calculation method of the new gear pair is deduced. Taking the involute internal gear as the given gear and the parabolic gear as the matching gear，an internal gear pair is designed. The results show that during the whole meshing process，the gear pair keeps point contact state at all times，and the meshing point moves along the theoretical contact trail，which is consistent with the theoretical analysis. The variation range of the sliding coefficient mainly depends on the involute parameter values corresponding to the entry and exit points selected at both ends of the gear.关键词：Contact trail;Parabolic tooth surface;Normal vector sweeping method;Sliding coefficient
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发布时间：2022-09-15 - 摘要：Taking the involute spur gear as the research object and considering the thermal effect and time-varying effect，the oil-water two-phase flow model and the thermal elastohydrodynamic lubrication model of the gear system are established，the influence of water content on the viscosity of the lubricants and the lubrication performance of the tooth surface are explored. The results show that when the water content in lubricating oil is less than 5%，the viscosity of oil-water two-phase fluid increased with the increment of water content. When the water content is 5%，the viscosity of oil-water two-phase fluid reached its peak value，and then decreased with the increment of water content. Appropriate increase of water content can improve the lubrication characteristics of tooth surface，but considering oil film temperature rise and corrosion wear of equipment，the water content should be controlled within 5%.关键词：Oil-water two-phase flow;Water content;Thermal effect;Time-varying effect;Lubrication characteristic
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发布时间：2022-09-15 - 摘要：The existing numerical atlas methods can not realize open interval path synthesis of spatial RRSS mechanism. A path synthesis method of spatial RRSS mechanism is proposeed based on wavelet decomposition theory. By transforming path synthesis problem into the matching and identification problem of the basic types of mechanism，and the calculation problem of the actual sizes of mechanism，the open interval path synthesis of spatial RRSS mechanism is realized. Thus，it makes up for the deficiency of the numerical atlas method in solving the dimensional synthesis problem with open interval design requirements. A numerical example is presented to demonstrate the practicability and effectiveness of the proposed method.关键词：Spatial RRSS mechanism;Open interval design requirement;Path synthesis;Wavelet decomposition
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发布时间：2022-09-15 - 摘要：In order to realize the multi-axis linkage machining of large slender integral structural parts，the new （（3-RPR+R） & UPS） + P hybrid machine tool mechanism with five degrees of freedom is proposed. The inverse kinematics model of the hybrid machine tool mechanism is established by using analytic vector method，and on this basis，the first-order and second-order kinematic influence coefficient matrices are obtained according to the kinematic influence coefficient method，and a more complete inverse kinematics model is established. Finally，the inverse kinematics model of the hybrid machine tool mechanism is solved by Matlab and simulated by Adams，and the results are basically consistent，which verifies the correctness of the inverse kinematics model of the hybrid machine tool mechanism.关键词：Hybrid machine tool mechanism;Inverse solution;Kinematics model;Kinematic influence coefficient
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发布时间：2022-09-15
Theory·Reserach
- 摘要：The analysis of meshing process of involute spur gear is an important basis to judge the transmission quality，and especially contact stress，transmission error and meshing stiffness are key indexes. According to the TCA model of spur gear，curvature radii in different meshing points are extracted. The meshing process of tooth surface is simplified as elastic extrusion between pairs of cylinders with different radii. Considering the load distribution between the teeth，the Hertz principle is used to carry out load-bearing contact analysis on the tooth surface. It shows that the results of this method are quite same as the results obtained by FEM and experiment. The error of the maximum of the contact stress is 0.74%.The results of transmission error and meshing stiffness are essentially same. The dynamic process of tooth surface contact and meshing stiffness can be reflected by this analysis method.关键词：Hertz contact;Contact stress;LTCA;Transmission error
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发布时间：2022-09-15 - 摘要：For better meshing status between spatial tooth profile of flexspline machined by radial modification of the tool and the planar tooth profile of circular spline，a design method for radial modification of flexspline tooth profile is proposed. The radial and circumferential positions of flexspline teeth under the action of elliptic wave generator are obtained by using the exact algorithm of flexspline assembly deformation，then backlash is obtained by the backlash algorithm between circular arc tooth profiles. According to the assumption of the straight-line generator，the positioning of the teeth profiles and backlashes in several cross sections are determined，then the backlash is obtained to reveal the spatial backlashes distribution in the cross-sections along the axial direction of flexspline with tapered deformation. The backlash distribution without radial modification shows that the backlash of the conjugated tooth profile of circular spline designed with conjugated meshing theory is very small and uniform in the design cross section，and serious interferences occur in the front and back sections. Inward modification of the cutting tool in the front and back sections can eliminate the interference. Reasonable radial modification designed iteratively achieves the optimal backlashes approaching zero in all cross sections，and realize a line meshing state from the front to the back sections. The simulation of meshing trajectory shows that the reasonable radial modification can achieve a better meshing state between tooth profiles.关键词：Triple arc tooth profile;Tapered deformation;Spatial backlash;Backlash algorithm;Meshing motion simulation
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发布时间：2022-09-15 - 摘要：In view of the poor stability of the star wheel type stair climbing device，the conception of step climbing staircase device is put forward. The device is designed and the influence of guide rail eccentricity e on its motion is analyzed. The running track of the three devices when e is 6 mm，10 mm and 15 mm is simulated by SolidWorks to verify the stability of their operation. The prototype is made and its running stability is tested. The results show that the step climbing stair device runs smoothly and the stability of the device has a great relationship with the eccentricity，instability increases with the increase of eccentricity. Therefore，when designing this kind of device，the eccentricity should be chosen to be smaller on the premise of meeting the use requirements.关键词：Step;Climbing stair device;Eccentricity;Stability analysis
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发布时间：2022-09-15 - 摘要：In order to improve the range and fuel economy of PHEV（plug-in hybrid electric vehicles），a new type of planetary gear driving device is presented，which can realize a variety of dynamic modes，and the adaptive control strategies modes is formulated. The simulation model of the PHEV is set up based on the ADVISOR software depending on the vehicle parameters of a domestic SUV，and secondary development to the control strategy of the vehicle is carried out at the same time. The PHEV in pure electric driving mode and hybrid mode are simulated in CYC-NEDC conditions. The results show that the mileage of pure electric range of new hybrid SUV is 16.7% more than that of the single motor endurance，the hybrid mode prompts the vehicle energy consumption reducing by 22.8%，which improved the fuel economy.关键词：Planetary gear;Hybrid power;Working mode;Control strategy
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发布时间：2022-09-15 - 摘要：In order to solve the problem of robot welding path planning for welding work at the ball pipe joints，taking the UR5 welding robot as a reference，the models of ball pipe intersection curve is established and the parameter equation of the curve is derived，the D-H coordinate system is established，the forward and reverse directions are solved respectively，by using the Matlab and Adams joint simulation，the trajectory planned path of end effector and the angular velocity and angular acceleration time change curve of each joint are obtained. The test shows that the UR5 welding robot model is correct and reasonable，has good kinematics performance，and has no sudden changes in the posture during the welding process. It also verifies the rationality and reliability of the trajectory planning operation space of the intersecting welding seam. It provides a verification method for welding operations in a complex working environment. The verification method can provide theoretical support for further research on prototype control.关键词：UR5 welding robot;Ball pipe intersection trajectory planning;Matlab robot toolbox;Adams simulation
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发布时间：2022-09-15 - 摘要：Humanoid robots are an important part of the field of robotics，and their characteristics analysis involves disciplines such as machinery，electronics，and materials. Since humanoid robots can imitate human behaviors and actions and can better serve humans，it has become a current research hotspot most humanoid robots are equipped with a large number of intelligent software and hardware，but the body design still has defects，especially the waist structure design of humanoid robots，which is not innovative and restricts the overall function. Based on this，a kind of humanoid robot waist structure is designed，it has a certain degree of innovation. Firstly，its pose is calculated by using the spin theory. Secondly，by using the Adams and Matlab，the simulation fitting is carried out. Finally，it is verified by experiments to prove the rationality and feasibility of the structure design，it lays the foundation for robot dynamics analysis.关键词：Humanoid robot;Waist structure;Spin theory;Adams
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发布时间：2022-09-15 - 摘要：In order to realize non-flow ripple and non-axial force of roots pump with helical rotor and greater capacity utilization and smaller internal leakage as desired by its lightweight，for high cross shape coefficient of rotor，a construction method for chord height line of pitch arc of half lobe as internal conjugate profile segment and top profile segment with radial equal arc gap is proposed，from coupled relation without axial force between volume pair with helical rotor and power pair with helical gear，its coupled design method with non-axial force is derived and an example is given. All results show that plane-convex conjugate gap and top equal arc gap can effectively restrain conjugate leakage and radial leakage，and cause larger shape coefficient of 1.6 and larger volume utilization coefficient of 0.58 to come true，helical angle of 60° can realize theoretical non-flow ripple，and coaxial design with equal cross pitch radius of helical rotor and standard helical gear can be derived from helical angle of 20°~25°，and the coaxial design method is simple，etc. It provides a theoretical basis for future high quality development of roots pump.关键词：Roots pump;Helical rotor;Helical gear;Chord height line;Non-flow ripple;Non-axial force
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发布时间：2022-09-15
Design· Calculation
- 摘要：The contact characteristics of a nutation drive with double circular-arc spiral bevel gears are extremely sensitive to installation errors. To reveal the effects of installation errors on contact characteristics，the tooth surface contact analysis of double circular-arc spiral bevel gear with installation error is carried out. Firstly，the tooth surface equation of nutation drive double circular-arc spiral bevel gear in internal meshing form is derived. Secondly，the contact trace and geometric transmission error of the gear pair are obtained by using the tooth contact analysis （TCA）. Finally，the influence of the cone point errors of inner and outer bevel gears and the axis angle errors of the gear pair on the contact characteristic of the tooth surface of the double circular-arc spiral bevel gear pair is analyzed by numerical examples. The research show that with the increase of various installation errors，the contact trace deviates from the tooth height accordingly. The deviations of contact trace on the convex and the concave tooth surfaces from the tooth height direction are different in terms of sensitivity to installation errors. A positive installation error may have a stronger impact on the transmission error than a negative installation error. Based on the present founding，the installation errors of a nutation drive double circular-arc spiral bevel gears should be reasonably controlled to obtain an ideal meshing performance.关键词：Double circular-arc spiral bevel gear;Nutation drive;Installation error;Contact trace;Transmission error
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发布时间：2022-09-15 - 摘要：Aiming at the phenomenon of vibration and abnormal joint response in the operation of walking robot，the dynamics method is adopted to simulate the contact state of the clearance model of the moving pair，and the natural frequency of the walking robot with clearance is analyzed，avoiding the problem that the nonlinear factors are ignored in the simulation analysis of the computational modal analysis method. With the help of transient dynamics simulation，the displacement response of the walking robot with clearance is calculated，and then through the Fourier transform，the frequency response curve is obtained，the corresponding frequency of the curve peak is the natural frequency of the walking robot with clearance. The existence of joint clearance can reduce the natural frequencies of the walking robot，but the clearance does not affect the mode shapes. The first-order mode is the sway vibration of the platform and the support leg along the X-axis，the second-order mode is orthogonal to the first-order mode，and the third-order mode is the torsional vibration of the platform and the support leg along the Z-axis.关键词：Clearance;Walking robot;Natural frequency;Transient dynamics analysis
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发布时间：2022-09-15 - 摘要：A kind of corn hill-seeder based on 4-CRR parallel mechanism is presented. The degree of freedom of the 4-CRR parallel mechanism is solved by using screw theory，and verified by using the modified Kutzbach-Grübler formula. The inverse position solution of the mechanism is solved by using equivalent plane projection method，and the Jacobian matrix of the mechanism is derived to analyze its velocity. The value range of rod length of 4-CRR parallel mechanism applied to hill-seeder is analyzed. The workspace of the mechanism with a rod length of 250 mm is solved by the limit boundary search method. The moving platform of the mechanism can realize translation movements along the three coordinate axis directions. The interior of the workspace is continuous，and a 300 mm×300 mm adjustable seeding area can be formed below the hill-seeder. The hill-seeder based on 4-CRR parallel mechanism can flexibly adjust the sowing position and change the planting density according to the different soil conditions in the field to achieve the effect of increasing yield and income of corn.关键词：4-CRR parallel mechanism;Hill-seeder;Workspace;Inverse position solution
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发布时间：2022-09-15 - 摘要：In response to the design requirements of miniaturization，lightweight and high resonance frequency of the flexspline，the inner diameter，aspect ratio，thickness-diameter ratio and tooth width coefficient of the flexspline are used as research variables. Based on the finite element Ansys，the response surface method parameter optimization analysis is used to explore the influence of the changes of each parameter on the natural frequency of the flexspline. The results show that，in the design process of the flexspline miniaturization，the decrease of the inner diameter and the aspect ratio of the flexspline will increase its natural frequency，and the decrease of the thickness-diameter ratio and the tooth width coefficient will increase its natural frequency，but its natural frequency is greater than the working excitation frequency of the reducer，and resonance will not occur to affect normal operation.关键词：Harmonic reducer;Response surface method;Modal;Natural frequency
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发布时间：2022-09-15 - 摘要：Aiming at the shortcomings of current beam pumping units with small stroke，large energy consumption，and poor movement performance，as well as the general problem of low reliability and unstable transmission of beam less pumping units，a design scheme of the reversing device of a long stroke pumping unit which realizes the pure mechanical non-switching type reversing by mechanical characteristic is presented. The 2K-H planetary gear train is input in parallel through the anti-parallelogram mechanism and the gears，and the device commutation is realized under the specific transmission ratio of the parallel gears. The new type of commutator avoids the reliability problems of motor and chain commutator，as well as the vibration problems of non-circular gear commutator，and the transmission efficiency is improved compared with crank and rocker commutator. The movement analysis of the reversing device is carried out，and the multi-parameter calculation simulation is compared. The influence of each parameter on the movement performance of the device is analyzed. The results show that the downstroke time of the reversing device is shorter than that of the upstroke，which is helpful to improve the production efficiency. The mechanism parameters can be adjusted according to the actual work requirements to meet the requirements of working conditions，and have higher design compatibility in the actual application. The device can realize efficient and reliable reversing work，and has a wide range of application prospects in the future development of tower pumping units.关键词：Pumping unit;Mechanical commutation;Anti-parallelogram mechanism;Planetary gear;Parallel transmission
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发布时间：2022-09-15 - 摘要：Aiming to solving the problem of cage failure under revolution-rotation，based on the dynamics theory of rolling bearing，the dynamics differential equations of needle roller bearing coupled with revolution-rotation working condition are established，and GSTIFF variable step length integral algorithm is adopted to solve the bearing. Cage stress is used to evaluate cage strength，and the influence of bearing working conditions on cage stress is studied to guide cage material selection. The results show that the cage stress with revolution is obviously greater than that without revolution. The impact force between the needle roller and the cage mainly affects the stress at the contact place where is between the needle roller and the cage，which increases with the increase of the impact force，while the centrifugal force of the cage mainly affects the stress at the angle of the beam slope of the cage，which increases with the increase of the centrifugal force. The 0Cr18Ni9Ti can be selected when revolution velocity is low，20CrMo can be selected when revolution velocity is high.关键词：Revolution-rotation;Dynamics;Needle roller bearing;Strength of cage
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发布时间：2022-09-15 - 摘要：The reason of the aeroengine transmission gear spokes fracture fault is analyzed，through the fracture examination，strength calculation，vibration characteristic analysis and stress test，the nature of the gear spokes fracture fault is the high-cycle fatigue caused by the pitch diameter resonance is determined. Based on the analysis results，the gear structure is improved and optimized to reduce vibration stress and increase strength reserve，and the optimized structure is tested and verified. The results show that the vibration stress of the optimized structure is greatly reduced，the strength reserve and working reliability are improved obviously.关键词：Aeroengine;Gear;Vibration stress;Pitch diameter resonance
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发布时间：2022-09-15
Test·Analysis
- 摘要：Based on the principle of constant stress accelerated fatigue life test，a testing machine for plastic gears is developed to test the fatigue life quickly. The working principle，structure composition and the design of core parts of the testing machine are mainly studied. On the whole，the horizontal structure is adopted，the special gear tooling is designed to ensure the test accuracy，and the temperature control box is used to adjust and control the test environment temperature. The experimental device can accurately measure the influence of speed，torque，temperature and cycle times of plastic gear on transmission efficiency. The experimental results show that the higher the torque is，the smaller the average efficiency，the higher the average temperature and the smaller the number of cycles are. It provides an efficient and feasible method and device for the life prediction and failure form research of plastic gear，which has theoretical value and practical application value.关键词：Plastic gear;Fatigue life;Temperature control;Transmission efficiency
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发布时间：2022-09-15 - 摘要：Traditional small module spiral bevel gear milling needs to use a large number of cutting fluid，which will not only cause environmental pollution，but also increase production costs，the new technology of high speed dry cutting does not use cutting fluid，which reduces environmental pollution and improves production efficiency. Based on the theory of bevel cutting，combining the equivalent plane method of oblique cutting with the machining theory of spiral bevel gear，the high speed dry cutting technology of small module spiral bevel gear is studied. Aiming at the characteristics of high speed dry cutting technology of small module spiral bevel gear，the thermal mechanical coupling model of bevel cutting is established，and the influence of different process conditions on cutting force is simulated and analyzed by using Abaqus finite element software. The cemented carbide is selected as the tool material，and the high speed dry cutting technology process of small modulus spiral bevel gear is discussed. The feasibility of this technology is verified by machining test. The research provides a reference basis for the implementation of this technology.关键词：Small module spiral bevel gear;Cutting simulation;High speed dry cutting;Bevel cutting
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发布时间：2022-09-15 - 摘要：In order to realize the machining of the cycloid coupling on the domestic CNC bevel gear milling machine，the cutting principle and processing method of the cycloid coupling are studied. Based on the structural characteristics of the cycloid coupling，the processing method for machining cycloid coupling with monolithic cutter is proposed，and the lengthwise curvature and profile curvature are corrected by changing the radius of the cutter and the radius of the blade arc. Based on the cutting principle of cycloid coupling，the calculation method for the cutter parameters and the machine tool adjustment parameters for machining cycloid coupling is proposed. The cutter interference check is carried out on the cycloid coupling. Through the use of monolithic cutter to process the cycloid coupling on domestic CNC bevel gear cutting machine，the correctness and feasibility of cutting principle and processing method is verified by tooth profile error measurement and contact pattern inspection.关键词：Cycloid coupling;Monolithic cutter;Cutter parameter;Machine tool adjustment parameter;Curvature modification
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发布时间：2022-09-15 - 摘要：Planetary gearboxes have the advantages of compact structure，high transmission efficiency，stable operation，etc.，and are widely used in heavy loads and key mechanical equipment. Since planetary gearbox often works in harsh environment，its key components are prone to tooth root crack fault damage and are not easy to be identified，easy to cause security risks. Compared with traditional transverse vibration signal，torsional vibration signal is not affected by the modulation of time-varying transmission path in theory，it has great advantages，so its frequency component is simple and it is easy to extract fault features. Taking torsional vibration signals as the analysis object，a windowed RMS time-domain synchronous averaging technique is proposed to realize the early tooth root crack fault diagnosis of planetary gearbox，and a fault simulation test bed is built to verify the effectiveness of the method.关键词：Planetary gearbox;Tooth root crack;Torsional signal;Time-domain synchronous averaging;Windowed RMS
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发布时间：2022-09-15 - 摘要：Taking a DCT transmission preliminary gear 3 to 2 as an example，through the analysis of rattle theory and influence factors，the precise comparison verification result between simulation and test of rattle sensitivity are obtained. The quantitative evaluation target of rattle sensitivity is formulated，and different flywheels are matched for real vehicle verification. This research has theoretical significance and practical value for guiding low-noise design and matching engine platform of transmission.关键词：Transmission rattle;Sensitivity;Vibration noise
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发布时间：2022-09-15
Development·Application
- 摘要：Overrunning clutches，as kernel components to achieve working condition changes，have two different working states of overrunning and engaging. With the development of mechanical transmission system technology，the working condition requirements for overrunning clutch are higher and higher. In order to facilitate further systematic research on overrunning clutch，meet the requirements of new age development of high-end equipment，through combing the related literature of mesh type，friction type two kinds of different types of overrunning clutch，the research hotspot and difficulties of overrunning clutch in recent years are summarized，and the future development direction of the overrunning clutch is analyzed. It is provided a basis and reference for subsequent overrunning clutch research.关键词：Overrunning clutch;Mesh type;Friction type;Development tendency
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发布时间：2022-09-15
Review
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