最新刊期
卷 47 ， 期 9 ， 2023
- 摘要：The tooth profiles at different positions of the non-circular gear pitch curve have the characteristics of equal modulus but unequal curvature radius and polar diameter. The distribution characteristics of the envelope curve of each tooth profile formed during the hobbing process are different, which lead to the unequal envelope error of the tooth profile at different positions. Taking the basic linkage model of hobbing as the motion constraint, the geometric simulation scheme of the tooth profile generated by the intermittent cutting of the hob is constructed, and the correlation characteristics between the envelope distribution and the curvature radius of the pitch curve and the polar diameter are analyzed. The concept of equivalent hobs is introduced, the relationship model between envelope error and equivalent gear tooth number and equivalent hob groove number is built, and the calculation and position distribution of the maximum envelope error of different tooth profiles are analyzed. A hobbing model to improve the envelope error is proposed. The model can realize the change of the equivalent hob groove number at different positions of the non-circular curve through the hob shifting method, thereby the maximum value and uneven distribution of the envelope error are improved. This study provides theoretical support for the analysis of the tooth profile envelope error of the non-circular gear hobbing, which can predict the envelope error and guide the formulation of a reasonable machining plan.关键词：Non-circular gear;Hobbing;Envelope error;Error suppression;Hob shifting
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发布时间：2023-09-18 - 摘要：The mechanical equipment in aerospace field that will not be reused after being used once is called disposable machinery. The failure of the flexible wheel is the most important factor affecting the performance of the disposable harmonic reducer. The change of the meshing stiffness can reflect the fault characteristics of the harmonic drive. In this study, the disposable and conventional harmonic gears are distinguished from the application environment and structure. Then, the crack initiation position of the flexible wheel in the disposable harmonic drive is analyzed. Besides, the damage model of the disposable harmonic flexible has been established based on the extended finite element method, and the crack propagation path of the flexible wheel rim is observed. Finally, the effect of cracks on the meshing stiffness of the disposable harmonic drive is discussed. The research conclusions of this study can provide theoretical support for fault diagnosis and life prediction of disposable harmonic gears.关键词：Disposable harmonic gear;Crack propagation;Meshing stiffness;Extended finite element method
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发布时间：2023-09-18 - 摘要：Aiming at the speed regulation characteristics of slotted-type eddy-current couplers, the expression of the induced magnetic field generated by the induced eddy current is derived by using Ampère's law and the induced magnetic field is introduced into the equivalent magnetic circuit model. Then, the calculation formula of electromagnetic torque is derived in combination with Kirchhoff's law. The electromagnetic torque formula is combined with the expression of constant torque load and quadratic rate load respectively, and the theoretical formula of the speed regulation relationship under corresponding load conditions is obtained. The 3D finite element simulation and experiment are used to verify the proposed theoretical model of speed regulation. It is found that the proposed theoretical model has good accuracy in the case of small air gap length.关键词：Slotted-type eddy-current coupler;Magnetic equivalent circuit model;Induced eddy current;Electromagnetic torque;Speed regulation relationship model
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发布时间：2023-09-18 - 摘要：Aiming at the tooth profile contact problem of internal meshing gear transmission pairs with double contact points, the generation method of tooth profiles of the internal meshing gear transmission pair with double contact points is present. Based on Hertz contact theory, the mathematical model of instantaneous contact ellipse of tooth profiles is established and the equations of contact trajectory are also derived. The contact ellipse area of tooth surfaces of the gear pair with double contact points is solved by the numerical analysis method, and the influences of the design and tooth profiles parameters on the contact ellipse are discussed. Using the finite element analysis method, the contact ellipse area and tooth surface contact stress of the internal meshing gear pair with single contact point and double contact points are compared. The research conclusions show that the contact area location and size can be effectively controlled by selecting the suitable contact angle, nominal pressure angle, normal modulus and spiral angle. Under the same parameters, the contact area with double contact points is larger than that of a single contact point, and the contact stress is smaller. The relevant research has important theoretical significance and reference values for improving the contact characteristics and mechanical properties of the new internal meshing gear transmission.关键词：Double contact points;Internal meshing gear;Contact area;Tooth surface contact analysis;Contact stress
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发布时间：2023-09-18 - 摘要：Considering the complexity of the gearbox structure, the first six orders are identified by using the single-point excitation and multipoint response modal identification technology, and the modal confidence, namely, the modal identification accuracy is high. Based on the first six orders of the gearbox obtained from the test, a modal finite element calculation method considering both calculation accuracy and calculation efficiency is proposed. Subsequently, the topology optimization method is used to optimize the structure of the gearbox. After optimization, the deformation of the gearbox at different natural frequencies is reduced, which provides a new idea for the optimization design of the gearbox structure.关键词：Gearbox;Modal analysis;Structural optimization design
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发布时间：2023-09-18
Theory·Research
- 摘要：In order to improve the transmission capability by exploring the relationship between torsional stiffness on output shaft and load meshing characteristics, a simulation model of finite element analysis (FEA) is built to evaluate the performance of tooth profile under transmission loading. A triple-circular-arc tooth profile of flexspline is constructed, and the radial modification of the tooth profile is adjusted to minimize the outer envelope overlap of meshing motion of the tooth profiles. Then, a triple-circular-arc planar tooth profile of circular splines is designed with the envelop method according to the outer envelope. A triple-circular-arc tooth profile of flexspline with tradial modification is constructed in several cross sections, and the spatial tooth profiles of flexsplines are generated by axial lofting in finite element environment. A finite element simulation model including circular spline with planar tooth profile, cup-shaped flexspline with spatial tooth profile and outer ring of wave generators is established. Transmission torques of different amplitudes in two rotational directions are applied on the flange plate at the bottom of the flexspline engaged with a fixed circular spline, and the meshing force distribution and torsional stiffness hysteresis curves are simulated. The number of meshing teeth in different meshing states can be estimated with the relationship between torsional stiffness and meshing characteristics of tooth profiles. The simulation results show that the number of meshing teeth is positively correlated with the torsional stiffness. Using the measureable hysteresis curve of torsional stiffness, the immeasurable meshing characteristics such as the number of meshing teeth can be estimated.关键词：Triple-circular-arc tooth profile;Spatial tooth profile;Meshing characteristics;Finite element simulation;Torsional stiffness
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发布时间：2023-09-18 - 摘要：Aiming at the problems of high labor intensity, high risk factor, long inspection time, low efficiency and wide range of manual inspection of railway catenary, a catenary inspection robot with a telescopic structure is proposed, which can replace manual inspection of the catenary. The overall structure of the robot and the selection of core components are determined. The screw theory and the modern matrix exponential product formula are used to establish the kinematics model; the Matlab Robotics toolbox is used to establish the simulation model and verify the kinematics equation; the Monte Carlo method is used to solve the robot workspace and draw the point cloud map. Finally, Ansys Workbench software is used for finite element analysis of key components, and the strength and stiffness are checked and verified. The designed robot in this study reduces the workload of workers; using lightweight materials and joint modular design makes the mass be reduced by 25%; its terminal multi-degree-of-freedom structure makes the shooting angle and range be increased by 2 times compared with the traditional way; the telescopic structure enables the robot to obtain a larger working space to meet the work requirements.关键词：7-DOF robot;Product of exponential;Workspace;Kinematic analysis;Finite element analysis
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发布时间：2023-09-18 - 摘要：Based on the topological design theory of a parallel mechanism with orientation feature set and bending translation theory, a new parallel mechanism with circular spherical translation and one rotation (2T1R) with 3 degrees of freedom （DOF） and low coupling is designed and topological characteristics of the mechanism are analyzed, including the orientation feature set, degrees of freedom and coupling calculation. The kinematics of the mechanism is analyzed, and the forward and inverse solutions of the position of the mechanism are solved and verified. Finally, based on the positive and negative equations of the mechanism, the workspace and the rotation capacity distribution of the mechanism are analyzed. The work in this study lays the foundation for the subsequent scale optimization, error analysis and dynamics analysis of the mechanism.关键词：Parallel mechanism;Bending translation;Kinematic analysis;Workspace
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发布时间：2023-09-18 - 摘要：In order to improve the ability of wheeled robots to surmount obstacles and improve the movement stability, a transformable wheeled-clawed flexible mechanism and a motion mode conversion transformation scheme of the robot are designed. The transformation principle of the wheel is introduced in detail and both the kinematics theory analysis and Adams kinematics simulation analysis of the deformation process are completed. The simulation results are basically consistent with the theoretical results. Through the mutual verification of theory and simulation, the accurate pulse width modulation （PWM） wave control range of steering gear is determined. In order to verify the feasibility of the proposed scheme, taking the wheel radius of 80 mm as an example, Adams virtual prototype simulation and prototype platform experiment are used to verify the obstacle crossing ability of the proposed transformable wheel. The simulation and experimental results show that the robot has stronger stability when moving on flat ground with a flexible structure.关键词：Transformable wheeled-clawed flexible mechanism;Robot;Kinematics;Stationarity analysis
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发布时间：2023-09-18 - 摘要：Aiming at the problems of insufficient modeling accuracy and low efficiency of design verification and calculation in the current parametric design and development of internal gears, a parametric design system of internal gears based on accurate tooth profile modeling is developed by using Matlab GUI. According to the principle of gear generating machining theory, the involute tooth profile of internal gears is generated. The tooth profile-normal method is used to establish the tooth root transition curve equation of internal gears, realizing the accurate modeling of the whole tooth of internal gears, and the pressure angles αM and αN at the transition point of the internal gear profile are calculated. The geometric calculation and interference verification of the design parameters of internal gear pairs are completed through the parametric design program. In the transition curve interference verification part, using the pressure angles αM and αN of the tooth profile transition point, the verification formula of the transition curve interference of the internal gear pair is calculated under the condition of any size tooth top fillet (or unspecified fillet) of the cutter. Finally, the whole tooth profile data of the designed target gear pairs is imported into the Catia interface, and the three-dimensional solid model of the gear pairs is established, which lays a foundation for the subsequent research on the stress analysis and dynamic performance detection of the gear system.关键词：Internal gear;Parametric design;Accurate tooth profile modeling;Tooth root transition curve;Transition curve interference;Tooth profile transition point
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发布时间：2023-09-18 - 摘要：Based on the two postures of trunk roll-up and extension, a spiral spatial folding mechanism composed of multiple modules is designed. The geometric relationship between the modules is analyzed, and the endpoint positions of the modules are calculated by the D-H method. The influence of the angle, length, number and scaling factor of the modules on the spiral shape is discussed. The spiral shape is designed as a whole by dimensional optimization, and the design of the solar wing is used as an example to calculate the dimensional parameters with the maximum unfolding length as the objective function and the spiral range, spacing and rod size as the constraints. The 3D models of the solar wing and gripper applications are given, and the appropriate driving method is briefly described for each application. This mechanism has a wide range of applications and can provide some reference for the design of the spiral mechanism.关键词：Elephant trunk;Spiral;Deployable mechanism;Dimensional optimization
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发布时间：2023-09-18
Design· Calculation
- 摘要：The research object is a two-speed double clutch automatic transmission (2DCT) of pure electric vehicles. Firstly, the modal simulation and test of the transmission housing are carried out to verify the accuracy of the finite element model of the housing. Then, considering the working efficiency of the motor, through the established dynamic model of the transmission system, the variation law of the transmission error of the gear pair under different torque conditions is obtained. The dynamic force of the bearing is further analyzed and taken as the boundary condition to study the vibration characteristics of the housing. By analyzing the modal participation factor (MPF), the modal order which contributes greatly to the shell vibration is determined. Finally, the vibration acceleration simulation and test of the obvious vibration area under multiple working conditions not only verify the accuracy of the dynamic model, but also further clarify the vibration characteristics of the 2DCT housing.关键词：Electric vehicle;Two-speed transmission;Housing;Transmission error;Modal participation factor
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发布时间：2023-09-18 - 摘要：An arc is constructed at the end of the planetary wheel profile shaft of the planetary traction drive, and the contact point between the arc and the outer ring and the end face of the solar wheel shaft is kept on the radial traction contact line. A new type of a more compact bearing reducer is designed by replacing thrust bearings cleverly. In this study, the radial contact stress and flange stress of the contact line are analyzed based on the assembly interference, the full arc element line modification and the influence of the contact line edge chamfering. Several sets of 3D ideal models are established and analyzed by Abaqus software. The results show that the edge stress concentration exists in the contact lines of the outer ring, planetary wheel and solar wheel of the bearing reducer. Reasonable contact-element trimming and edge chamfering can make contact stress uniform and improve edge effect. The best way to improve the contact stress of traction drives is to modify the contact element and chamfering the edge simultaneously. The distribution and size of the contact stress at the flange are basically the same under different convexity modification, and the axial and radial contacts between the contact line of the planet wheel and the outer ring and the contact line of the sun wheel and the flange can remain on a traction line.关键词：Planetary traction drive;Contact stress;Bearing reducer;Plain wire modification
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发布时间：2023-09-18 - 摘要：In this study, milling large wheels for spiral bevel gears by the profile method, the effect of cutting speed, depth of cutting and feed rate on the residual stress on the machined surface is studied. According to the characteristics of spiral bevel gears machined by the forming method, a three-dimensional simulation model of bevel cutting is established to simulate the cutting process of gears, and the effects of cutting speed, feed rate, depth of cutting and coolant on the residual stresses on the surface of the workpiece are simulated using the single factor method. The simulation results show that the residual stresses on the machined surface of the spiral bevel gear are distributed in a "spoon" pattern along the depth of cut, the residual tensile stresses are on the surface, and the residual compressive stresses are on the sub-surface. The surface residual tensile stress increases with the increasing feed rate and cutting speed, the layer depth of residual stress deepens with the increasing feed, and the depth of cut has no significant effect on the residual stress. The addition of coolant reduces the residual tensile stress on the surface. Through this research, a theoretical reference is provided for the analysis of residual stresses in the cutting of spiral bevel gears.关键词：Spiral bevel gear;Oblique cutting;Residual stress;Finite element simulation
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发布时间：2023-09-18 - 摘要：A finite element simulation model is established for the gearbox body of 120B metro vehicle model in China. The fatigue strength, static strength and safe nose strength of aluminum alloy and nodular cast iron gearbox are calculated by the finite element method. The results show that the maximum equivalent stress of aluminum alloy case is larger than that of nodular cast iron, and the maximum difference ratio is 36.3%. The static strength and type test of aluminum alloy and nodular cast iron box are compared. The results show that the maximum stress of aluminum alloy case is greater than that of the ductile iron, and the difference ratio is 8.3%. The maximum sound power and vibration value of the aluminum alloy case are greater than that of the nodular cast iron case, but the average bearing temperature decreases by about 10 ℃. Although the strength of the aluminum alloy case is weaker than that of the nodular cast iron case, the overall factor of safety of the aluminum alloy case is higher than that of the nodular cast iron case, which can still meet the service life of 33 years or 9.6 million kilometers requirements. In this study, the applicability of aluminum alloy box is analyzed. The results show that both the aluminum ductile iron and the aluminum alloy can be used in metro gearboxes; both materials have their own advantages and disadvantages, and priority selection can be made during design based on the specific requirements of the vehicle.关键词：Standard metro;Case;Simulation calculation;Test;Lightweight
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发布时间：2023-09-18 -
Analysis of Vibration and Noise Response Characteristics of Electric Vehicle Reducers Based on Masta
摘要：In order to improve the coupling vibration response characteristics of the reducer system, the model of the gear transmission system is established by using the Masta software. Secondly, the finite element model of the differential case and the reducer case is introduced for coupling, the noise waterfall diagram of the reducer under various working conditions is obtained through NVH (Noise, Vibration and Harshness) analysis, and the noise slice diagram and dynamic response curve of it under various operating conditions are further obtained. Finally, the influence of the pressure angle, helix angle and tooth width on dynamic response of the gear transmission system is studied and optimized. The results show that the dynamic meshing force of each operating condition of the reducer system after optimization is reduced, and the noise radiation is greatly reduced, which provides a theoretical basis for the vibration reduction and noise reduction design of the reducer.关键词：Vibration response characteristics;Multi operating conditions;Pressure angle;Helix angle;Tooth width;Dynamic meshing force- 17
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发布时间：2023-09-18 - 摘要：Considering misalignment angles will appear during the actual installation of angular contact ball bearings and truncated contact ellipse will be produced due to bearing excessive external load, a bearing limit bearing capacity analysis model containing misalignment angle is put forward. By improving the algorithm, the number of equations and the difficulty of solving the model are reduced. Then the correctness of the algorithm is verified by comparing it with literature and Romax software. Finally, the angular contact ball bearing 7008C is taken as the research object and the influence of different parameters on the ultimate load carrying capacity is analyzed. The results show that increasing the misalignment angle and radial force, increasing the number of rolling elements, and reducing the diameter of rolling elements will weaken the ultimate axial force and the ultimate overturning moment to a certain extent, and increasing the curvature radius coefficient and shoulder height can significantly improve the ultimate axial force and the ultimate overturning moment. However, the minimum shoulder height restricts the bearing ultimate load carrying capacity.关键词：Angular contact ball bearing;Misalignment angle;Ultimate axial force;Ultimate overturning moment;Improved algorithm
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发布时间：2023-09-18 - 摘要：In high-speed machine tools, the friction heat of bearings will cause the deformation of the rolling body and the "burning shaft", which will reduce the fatigue life of bearings and affect the normal operation of equipment. Taking high-speed angular contact ball bearing 7003C as an example, based on the quasi-static analysis of high-speed angular contact ball bearings, the force analysis of the bearing is carried out, and the friction power calculation model of the bearing is established by using the local method. Based on the heat transfer theory, the heat transfer model of the bearing system is established. The temperature rise model of the bearing system is established and simulated by using the finite element software, and the effects of rotational speed, axial force and lubricating oil temperature on the temperature rise of the bearing system are analyzed. Finally, the temperature rise test is designed and compared with the theoretical simulation. The results show that the temperature rise of the bearing system increases with the increase of the bearing speed and the axial force, and the temperature rise is the highest at the steel ball, followed by the inner ring, and finally the outer ring. Lubricating oil temperature plays an important role in bearing system temperature changes. The maximum error rate between the test results and the simulation results is 11.66%, which verifies the rationality of the theoretical calculation and the model simulation, and provides some reference value for the study of bearing fatigue life.关键词：Angular contact ball bearing;Quasi-statics;Heat generation;Temperature rise model;Temperature rise test
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发布时间：2023-09-18
Test·Analysis
- 摘要：Dedicated hybrid transmission (DHT) has attracted wide attention because of its light weight and small overall size. The hybrid system has a variety of different power sources, which can change the operation mode to respond to different operating conditions, thus improving the fuel economy. The DHT torque distribution control strategy model is built on Matlab/Simulink platform to control the optimal output torque of the engine, so as to ensure the engine operating in the economic zone. Off-line simulation is carried out based on the test cycle conditions of light passenger vehicles in China and light vehicle in the world. The results show that the matching accuracy of the expected speed and the actual speed is high, and the simulation model is accurate and reliable. Under CLTC_P condition, the fuel consumption of 100 km is 5.74 L, saving 36.33% than that of traditional fuel vehicles.关键词：Dedicated hybrid transmission;Torque distribution;Off-line simulation
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发布时间：2023-09-18 - 摘要：In order to stably exert the best obstacle-surmounting performance of the wheel-track compound robot, a new wheel-track compound robot that can switch multiple motion modes according to the environment is developed. The robot can switch between the upright motion and the crawler motion mode, and the position of the center of gravity of the robot can be greatly adjusted by the rotation of the swing arm, which has better obstacle-surmounting performance. On the basis of gait planning and motion mechanism analysis of the robot, kinematics and dynamics analysis of the typical step crossing motion process are carried out, which verifies the feasibility of the robot mode switching, and calculates the maximum theoretical value of the step height that the robot can climb. Finally, using the simulation software, according to the theoretical values obtained by the calculation, the simulation test of the robot's step climbing process is carried out. The results verify the accuracy of the calculated values and the obstacle-surmounting performance of the robot.关键词：Wheel-track hybrid robot;Obstacle-surmounting performance;Kinematics;Dynamics
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发布时间：2023-09-18 - 摘要：The output gear shaft of the main gearbox for polypropylene granulator main gearbox breaks during operation.Fracture reasons of the output gear shaft are investigated through fracture analysis, physical and chemical inspection, and strength check. The results show that the output gear shaft has early fretting tear, due to instantaneous impact caused by fracture of the corresponding screw shaft. Under the compound alternating load of the torque and the bending moment, the early crack initiates and propagates along the journal. When the effective bearing area of the output gear shaft reduces to the critical point that it cannot withstand the torsional torque generated by normal operation, the fracture of the output gear shaft occurs. It is easy to form stress concentration at the cutter back groove of the output gear shaft journal, which is also one of the cracking inducement.关键词：Gear shaft;Fracture failure;Instantaneous impact;Fretting tear;Stress concentration
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发布时间：2023-09-18 - 摘要：To solve the problems of low accuracy, difficult diagnosis and long time consuming of the current fan bearing fault diagnosis, an improved grey wolf optimization (IGWO) algorithm and a support vector machine (SVM) fault diagnosis method are proposed. In order to accurately extract the fault features, the wavelet packet decomposition method in the time-frequency domain analysis is used to extract the fault vibration signal. Take the wavelet packet decomposition energy of the eight frequency bands as the fault feature， the eigenvectors are constructed. Then, the fault model of SVM is established and the parameters of the SVM model are optimized by the IGWO algorithm, which avoids the defects of local optimum and slow convergence. According to the experimental analysis result, the average fault recognition rate of the IGWO algorithm is up to 99.3%, and it can identify fault types more quickly, more efficiently and more accurately, which provides a good support for the development of fault diagnosis.关键词：Support vector machine;Improved grey wolf optimization algorithm;Wavelet packet decomposition;Feature extraction;Fault classification
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发布时间：2023-09-18
Development·Application
- 摘要：Due to special tooth surface morphology, the crown gear coupling achieves misalignment compensation while causing the non-uniform carrying of tooth pairs, which destroys the stability of the tooth surface contact. Scholars at home and abroad have carried out extensive research on the contact theory of tooth pairs, reviewed the contact characteristics and the theoretical research of crown gear couplings, and pointed out the contact theory model of clearance of tooth pairs, contact stress of tooth surface, and load distribution of tooth pairs, which is the key technology to achieve the optimal design of high-performance crown gear couplings.关键词：Crown gear coupling;Contact theory;Clearance of tooth pairs;Contact stress of tooth surface;Load distribution of tooth pairs
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发布时间：2023-09-18
Review
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