最新刊期
期 6 ， 2022
- 摘要：Manufacturing errors are one of the main causes of vibration and noise of gear transmission system，and the combination of multiple errors seriously affects the meshing performance of gear pairs. The influence degree and law of various manufacturing errors on meshing performance of herringbone gear pairs are mainly studied. Firstly，the manufacturing error model is established，and the actual tooth surface is constructed based on the theory of spatial coordinate transformation. Secondly，the influence law of different errors on the meshing performance of the gear pair is explored through the load distribution on the tooth surface，and the influence degree of different errors is explored based on the orthogonal experiment. Finally，the relationship between the influence of typical error types on the meshing performance of gear pairs and the system load is analyzed. The results show that the influence law of various errors on the meshing performance of gear pair is different，and the positive tilt deviation of helix direction has the most prominent influence on the meshing performance of gear pairs under heavy load.关键词：Manufacturing errors;Contact analysis;Meshing performance;Load distribution;Orthogonal experiment
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发布时间：2022-10-04 - 摘要：The high thrust electro-mechanical servo actuator in rocket launcher is a linear transmission mechanism with high precision planetary roller screw as its core component. In order to study the fatigue stability characteristics of planetary roller screw mechanism，a fatigue comparison test of fault-free and fault is carried out. Based on the test data curve，the influence of loss of gear tooth and two working conditions with or without grease on load，displacement，speed and temperature rise of planetary roller screw mechanism are analyzed. The result shows that planetary roller screw mechanism could maintain relatively stable load，displacement，speed and temperature rise curves under two working conditions of partial tooth defect or without grease. The planetary roller screw mechanism of high thrust electro-mechanical servo actuator could be used without maintenance or less maintenance for the engineering application in case of tooth damage and little grease.关键词：Electro-mechanical servo actuator;Planetary roller screw mechanism;Fatigue;Stability
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发布时间：2022-10-04 - 摘要：The external excitation caused by random wind load can greatly affect the fatigue life of the wind power transmission system. A four-component model considering the wake effect is used to simulate the random wind speed of a wind farm， and combined with the finite element method， the fatigue life of the wind power planetary gear train is obtained. On this basis， the influence of the depth， length and extension angle of the sun gear single-tooth and double-tooth root cracks on the fatigue strength of wind power planetary gear trains is studied based on the sub-model method. Finally， it is found that the influence degree of the crack size parameters on the fatigue life of the wind power planetary gear train is: crack depth> crack length> crack extension angle. The effect of double root cracks on fatigue life is much greater than that of single root cracks， the fatigue life of the first-engaged tooth in the double-root crack state is much shorter than that of the single-root crack state， and the fatigue life of the later-engaged tooth is slightly larger than that of a single-tooth root crack state. Related research provides a theoretical basis for optimizing the service performance of wind turbines.关键词：Four-component combination model;Fatigue strength;Tooth root crack;Sub-model method
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发布时间：2022-10-04 - 摘要：The numerical simulation of injection lubrication of high-speed wide gears and the improvement of lubrication effect are studied. Based on experimentally verified simulation methods，the oil injection lubrication simulation analysis of the oil-gas two-phase flow model of the high-speed wide-tooth cylindrical gear transmission is carried out. The result shows， the gas pressure field around the high-speed gear will seriously hinder the oil jet； excessive end face angle and unreasonable spray direction make it difficult for oil to lubricate the entire tooth surface of a wide gear. The simulation results of single-phase gas field are used to optimize the injection parameters. After that，the simulation results of two-phase flow verified the effectiveness of the optimization，which is，when the end face angle is 0，the nozzles on the meshing-in side are arranged symmetrically along the tooth width，and the nozzles on the meshing-out side are aligned with the meshing heating surfaces of the two gears. When spraying oil，it is more conducive to increase the oil and gas ratio and the convective heat transfer coefficient of the meshing tooth surface， thus，efficient lubrication and cooling of meshing tooth surface can be realized.关键词：Mesh-in-side oil injection;Mesh-out-side oil injection;Gas field simulation;Two-phase flow simulation optimization of oil injection parameters
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发布时间：2022-10-04 - 摘要：On the basis of the principal of gear generating machining method，the gear flank mathematical model and gear tooth flank contact line equation of skew bevel gears with equivocal modification are derived，the contact finite element dynamic analysis model with seven teeth is built，the position of edge contact in a meshing period，as well as the variation curves of contact stress and bending stress under different loads are obtained. The variation rule of normal contact force and the contact ratio of skew bevel gears in stable meshing period are analyzed. The result shows that edge contact occurs when skew bevel gears enter and exit meshing process. The contact force curve in the entire meshing period is smooth，which is symmetrically distributed near the three-tooth meshing period and has a high contact ratio. The maximum bending stress occurs near the tooth root transition fillet of the large end of the driven gear and the small end of driving pinion.关键词：Skew bevel gear;Equivocal modification;Tooth edge contact;Contact force;Finite element analysis
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发布时间：2022-10-04 - 摘要：Cylindrical gears with arc teeth as imaginary knife， which generate orthogonal arc tooth face gears using the envelope forming theory. Tooth surface equations of cylindrical gears with arc teeth and face gears are derived， which are based on differential geometry calculation and principle of gear meshing. Mathematical models of working tooth surface and transitional tooth surface are established based on Matlab. With the radius of tooth surface of cylindrical gears with arc teeth changed， the changes of tooth thickness， tooth width and contact line of face gears and the influence on contact trace are compared and analyzed by modifying of the face gear. Finally, through deriving the tooth point set of the face gear before and after modification， the entity modeling in the CATIA parts design is carried out. It is concluded that， with the increase of the radius of concave tooth surface of cylindrical gears with arc tooth， the outer radius of the face gear will have an augment. In the meanwhile， the phenomenon of tooth tip sharpening of face gear will change， that is the tooth thickness at the outer radius of the face gear increases gradually， the contact line has little change. The conclusions have laid a foundation for future research on partial load characteristics of face gears.关键词：Arc teeth;Face gears;Shape modification;Tooth tip sharpening
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发布时间：2022-10-04
Theory·Reserach
- 摘要：In order to solve problems of high coupling degree，inconvenient control and insufficient flexibility when spherical parallel mechanism is applied in the field of robot bionics，a novel three-branch spherical parallel mechanism with semi-decoupled characteristics is proposed. Based on the screw theory，the degree of freedom （DOF） of the mechanism is analyzed. The forward and inverse kinematics solutions of the mechanism are solved by the vector method and the decoupling characteristics of the mechanism are analyzed. The mechanism has a 3-DOF to rotate around the X axis，Y axis，Z axis，and the rotation around the Z axis is controlled by only one branch，while the other two branches jointly control the mechanism to move around the X axis，Y axis. Jacobian matrix is obtained based on differential transformation method and singular configuration is discussed. The workspace of the mechanism is determined by the boundary search method with singular configuration and bar interference as constraints. Based on the decoupling characteristics of the mechanism，a global mean dexterity with decoupling coefficient is proposed. Taking the workspace and global mean dexterity as the optimization goals，the particle swarm optimization algorithm （PSO） is used to synthesize the structure parameters of the mechanism. After the optimization，the workspace is enlarged and the motion performance in this space is good，which provides a theoretical basis for the prototype design of the spherical parallel mechanism and the scale synthesis of other semi-decoupling mechanisms.关键词：Spherical parallel mechanism;Screw theory;Jacobian matrix;Scale synthesis
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发布时间：2022-10-04 - 摘要：Hybrid manipulator has high bearing capacity of parallel manipulator and large operating space of series manipulator，so it has broad engineering application prospect. Taking the RPS parallel mechanism with decoupled characteristic as a module，a partially decoupled hybrid manipulator of series parallel hybrid structure is constructed. By distributing the drive chain on different platforms， the closed positive position solution is obtained. The independent position motion and pose motion are realized by establishing the virtual prototype. The theoretical results are consistent with the motion simulation results， and the displacement data points of the actuator change smoothly， it shows that the manipulator can relize complex operation motion. The motion inertia of the series parallel hybrid manipulator is reduced by this method， which provides an important theoretical basis for the application of the manipulator.关键词：Hybrid manipulator;Decoupled characteristics;Separated positions and poses;Complex operation;Motion inertia
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发布时间：2022-10-04 - 摘要：The stress concentration effect can be reduced and the fatigue life of flexspline can be improved by reasonably selecting the structural parameters of flexspline. Based on the sensitivity analysis of parameters，the key parameters affecting the stress of the flexspline are screened out. The optimization objectives are to minimize the maximum equivalent stress of the gear ring and the volume of the harmonic reducer in the processes of no load as well as loading， the response surface optimization of flexspline parameters is completed. Through fatigue calculation，it is found that the life of the optimized flexspline is improved to a certain extent.关键词：Flexspline;Parameter sensitivity;Response surface;Multi-objective optimization;Fatigue analysis
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发布时间：2022-10-04 - 摘要：The reliability of the planetary cycloidal reducer directly affects the overall performance and service life of industrial robots，among which the reliability of two-stage drive subcomponents has an important influence on the reliability of the whole planetary cycloidal reducer. Taking a heavy-duty planetary cycloidal reducer as the research object，the reliability mathematical model of each subcomponent is constructed based on the force analysis of two-stage transmission system subcomponents，and the reliability is correlated and coupled by Copula function to construct a system reliability model considering failure correlation； on this basis，a multi-objective optimization model with minimum volume and maximum reliability is constructed，and NSGA-Ⅱ（Non-dominated sorted genetic algorithm-Ⅱ） algorithm is used to solve the model，and it is compared and analyzed with the system reliability model considering the independence assumption. The results show that， after optimization，the volume of the reducer is reduced by 11.27%，and the reliability is improved by 5.29%，and the optimal design method considering failure correlation can effectively improve the reliability of the planetary cycloidal reducer with higher comprehensive performance.关键词：Planetary cycloidal reducer;Failure correlation;Reliability;Multi-objective optimization
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发布时间：2022-10-04 - 摘要：In order to derive the volume utilization factors of Roots rotor for pump simply and efficiently，a novel inverse method of volume utilization factors is proposed based on the causal relationship between volume utilization factors and the average theoretical flow，and the different effects of two profile structures with and without clearance on volume utilization factors are analyzed. All results show that the inverse method from the average theoretical flow which is the effect to the volume utilization factors which are the cause is simple and efficient，the results are accurate and reliable，and the general applicability is strong； the profile structure with clearance is beneficial to maximize the volume utilization factor； by controlling the upper limit of profile factor，the shape factors and volume utilization factors are indirectly influenced by the curve type of conjugate profile； volume utilization factor can be simplified as a single variable function of shape factors，and the type of conjugate profile determined by profile factors has little influence on the volume utilization factors etc. It provides a new idea and method for calculating the volume utilization coefficient and other profile characteristics of rotor pump.关键词：Roots pump;Volume utilization factors;Average theoretical flow;Causal relationship;Inverse method;Shape factors;Profile factors
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发布时间：2022-10-04 - 摘要：In order to improve the flight performance of flapping wing aircrafts，a multi-DOF flapping wing mechanism based on space four-bar mechanism is designed by referring to the flight motion characteristics of small and medium-sized birds. Firstly，a kinematic model of the flapping wing driving mechanism is established through kinematic analysis. Then，a simulation model of the flapping wing mechanism is established in Adams to verify the theoretical analysis. The results show that， the design of a driving mechanism with single degree-of-freedom drive can realize the flutter，torsion，deflection multi-degree-of-freedom coupling movement，and the upper flutter limit is 34.65°，the lower flutter limit is -29.66°，the maximum torsion angle is 15.05°，the minimum torsion angle is -14.9°，the deflection angle range is -5.01°~5.21°； the track wich an "8" word output is the same as that of flying wing tips of small and medium-sized birds，which shows a good aerodynamic performance. The kinematic parameters obtained by simulation are in agreement with the theoretical calculation，which verifies the correctness of the theoretical calculation.关键词：Flapping wing aircrafts;Multi-degree-of-freedom;Driving mechanism;Kinematic analysis;Adams
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发布时间：2022-10-04
Design· Calculation
- 摘要：The history and evolution of the random fracture terms，the morphological features，failure examples，causes and preventive measures of various random fracture modes are comprehensively discussed. Contemporary mechanical engineering proposes high speed，heavy load and light weight requirements； what's more the application conditions are more stringent； thus，the gear tooth random fracture has become a common failure mode. For the most commonly used hard tooth flank gears today，the final bending failure of more than 70% of the gears is random fracture. There are multiple failure modes for random fractures. Both the TIFF（Tooth interior fatigue fracture） and TFF（Tooth flank fracture） discussed are typical random fractures. Facing the important objective existence of gear random fracture，it is suggested that designers，manufacturers and relevant experts and scholars of the gear should do further research and analysis of this failure phenomenon，so as to optimize the design and manufacturing，and avoid random gear fracture as much as possible.关键词：Hard tooth flanks;Gear teeth;Random fracture;Failure modes
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发布时间：2022-10-04 - 摘要：Aiming at problems of low braking torque and transmission efficiency of the gap of uniform clearance magnetorheological fluid brake and according to the principle of squeeze enhancement effect of magnetorheological fluid，an eccentric magnetorheological brake is designed and the braking torque model of eccentric magnetorheological brake is established. The effects of working clearance，eccentricity and eccentric distance on braking torque are analyzed. Based on Sobol method，the global sensitivity analysis of structural parameters of the brake is carried out. Optimization is carried out taking the maximum braking torque of eccentric MRB as the objective. The results show that eccentricity has great impact on the braking torque， the braking torque of eccentric brake increases with eccentricity； it rises from 38.3 N
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发布时间：2022-10-04 - 摘要：Taking the main bearing of the shield machine as the research object， and a finite element analysis on the contact fatigue mechanism of the main thrust raceway is carried out. Considering the size of the main bearing of the shield machine is too large， a simplified main thrust raceway contact model is used for finite element analysis， and the validity of the numerical model is verified by comparing the theoretical solution and numerical simulation solution of raceway contact stress. A semi-elliptical crack is inserted into the raceway surface based on FRANC3D to study the influence of load and friction coefficient on the fatigue damage of the main thrust raceway.关键词：Main bearings of shield machine;Main thrust raceway;Fatigue mechanism;Cracks;FRANC3D
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发布时间：2022-10-04 - 摘要：The differences of microstructure and mechanical properties of 50CrVA chain plate caused by different tempering temperatures under the same isothermal quenching process and the same tempering holding time are analyzed，and the tensile and fatigue properties of chain plate under different tempering temperatures and chain plate without tempering are studied.关键词：Roller chain;Chain plate;Isothermal quenching;Tempering temperature Tensile strength;Fatigue life
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发布时间：2022-10-04 - 摘要：In order to realize the localization of unmanned helicopter gear oil，the influence of different performance gear oil on gearbox performance is clarified，so as to improve the reliability and service life of gearbox scientifically. Zhengzhou Research Institute of Mechanical Engineering Co.， Ltd.， jointly developed 80W-140 unmanned helicopter gear oil. Based on the performance test of the oil in the laboratory，the performance of the 80W-140 unmanned gear oil is compared and tested with that of the imported oil through the gearbox comprehensive test bench. The vibration，noise，temperature，efficiency and gluing torque obtained from the bench test are carried out，the results show that different performance oils have obvious different effects on the efficiency and bearing capacity of the gearbox， the 80W-140 oil product has better friction reduction，anti-wear and anti gluing performance，which can effectively improve the reliability of the gearbox.关键词：Gear oil;Unmanned helicopter;Gearbox;Bench test;Lubrication
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发布时间：2022-10-04 - 摘要：The wear of gear in running stage can reflect the fatigue life and wear performance of gear in the whole service cycle. Polishing and grinding technology is a new type of gear grinding technology，which can effectively improve the surface quality of gears and improve the wear performance of gears in running stage. To investigate the effect of polishing and grinding technology on the running performance of gears and taking a low-speed driving gear of a transmission as the research object，a pair of polishing grinding gears and a pair of conventional grinding gears are processed respectively. The two pairs of gears are tested on the gear test stand. The ferrogram is collected during the gear operation. The ferrograph data is analyzed by using Matlab，and the influence law of polishing and grinding process on the running performance of gear is obtained. The results show that the polishing grinding technology can effectively improve the wear performance of the gear in the running process，reduce the wear rate of the gear，shorten the running cycle of the gear，and make the wear process of the gear in the running process more moderate. The conclusion provides some data support and reference for the application of this technology in gear machining.关键词：Polishing grinding;Ferrographic analysis;Gear running;Wear rate
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发布时间：2022-10-04
Test·Analysis
- 摘要：Aiming at the problem of phase lag in flapping wing of traditional flapping wing aircraft，a kind of flapping wing aircraft driven by crank chute mechanism is designed，its modeling and simulation analysis are carried out，the prototype is made and the actual flight test is carried out. The mass of the prototype is 26 g，the wingspan is 340 mm，and the maximum beating frequency is 17 Hz. The crank chute mechanism is analyzed theoretically，and the kinematic equation of the mechanism is deduced； the kinematic simulation analysis of crank chute mechanism is carried out by using the SolidWorks software. The motion characteristics of flapping wing aircraft under different crank length and different flapping frequency are studied，and a suitable crank length is determined； the power consumption of flapping wing aircraft with different motor types and reduction ratios is tested，and a set of low-power power devices is determined. The results show that the crank chute mechanism can eliminate the phase lag between the wings and reduce the influence of lift imbalance on the fuselage； when the crank length is 4.5 mm，the up stroke angle and down stroke angle of the wing are 45° and -15°； the flapping wing aircraft can achieve stable flight in the air.关键词：Flapping wing aircraft;Crank chute mechanism;Phase lag;Motion simulation
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发布时间：2022-10-04 - 摘要：In order to improve the accuracy of gearbox fault diagnosis and accurately express the health status of the gearbox， combined with deep learning algorithms， a GAF-inceptionResNet model for gear fault diagnosis is proposed. The model can directly take the original one-dimensional vibration signal after GAF transformation to form photos as the input of the model. Through the stem-block， residual inception， residual module and classification layer， the residual inception network can broaden the network depth and improve the training time and accuracy， the residual block uses identity mapping to greatly reduce the training difficulty of the model. Therefore， the model can effectively mine the information between the signal features and enhance the feature learning ability of the model， thereby improving accuracy and accurately determine the faults. The test results show that the model can achieve a fault diagnosis accuracy of 99.59%. It can effectively achieve good gearbox fault identification and classification.关键词：Gearbox;Fault diagnosis;GAF;Vibration signal;Deep residual network
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发布时间：2022-10-04 - 摘要：Aiming at the rapid diagnosis and optimization of gear excitation whine noise in the forward design of heavy vehicle drive axle， a dynamic response analysis method integrated considering the structural rigidity of drive assembly is introduced. The gear whine noise simulation and experiment are carried out on a sample vehicle equipped with a twin drive axle. The calibration results show that there is a good correlation between calculation and test response. Then， the noise optimization scheme (optimization of transmission error， modification of structure transmission path) is calculated and analyzed， and a significant noise reduction is achieved.关键词：Gear whine;Transmission error;MASTA;Coupled mode;Response analysis
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发布时间：2022-10-04 - 摘要：Aiming at the further acceleration of the aging speed in China， and considering the lack of effective exercise for the elderly， their shoulders， elbows and wrist joints often suffer from soreness， pain， and other problems. Thus， a new type of arm joint training instrument with multi-posture and multi-motion forms for family use is developed. Through theoretical design and calculation， and based on NX， a forward kinematic analysis and comparison of the four-bar mechanism without rapid return is conducted， 3 sets of rod length parameters (corresponding to 2 attitudes， 3 different motion forms， 9 different motion parameters respectively) are determined as a design scheme， and the force balance and load change analysis of the arm joint training equipment are carried out by the design scheme. Finally， according to the theoretical design calculation and the dynamic simulation analysis data of the NX virtual prototype， the performance of the physical prototype of the training instrument is trial-produced and tested. The test results show that the training instrument is safe， reliable and comfortable， and the human shoulders， elbows， wrists and waist joints can be better trained.关键词：New type;Multi-posture;Multi-motion form;Arm joint;Training instrument
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发布时间：2022-10-04 - 摘要：Aiming at the fact that the performance of support vector machine （SVM） in vehicle gearbox fault diagnosis is greatly affected by parameters，a new method of vehicle gearbox fault diagnosis based on improved SVM is proposed based on the research of beetle antennae search （BAS）. Compared with BAS，IBAS modified the step size formula and added Gaussian variation behavior，so that the search ability of the algorithm in the early and late period is balanced and has the ability to jump out of the local optimal，and better SVM parameters could be obtained. The results of gearbox fault diagnosis show that the proposed method can effectively improve the accuracy of fault diagnosis，and the results are better than those of other methods.关键词：Beetle antennae search;Support vector machine;Gearbox;Fault diagnosis
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发布时间：2022-10-04
Development·Application
- 摘要：The stability of the transmission system is directly related to the survivability of the helicopter. The failure of lubrication system under the condition of war injury will accelerate the damage of gear surface and destroy the dry running condition. The dry running capability of the gear has become an important factor to evaluate modern helicopters. The research status of dry running thermal analysis of gear transmission system is reviewed. The current studies on improving the dry running capability of the gear transmission system are reviewed from the aspects of gear surface modification, coating, surface texture treatment, the design of transmission and lubrication systems, and the corresponding experiments. The application status of these methods is summarized to provide reference for the research and development in this field.关键词：Gear transmission system;Dry running;Coating;Surface treatment;Experiment
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发布时间：2022-10-04 - 摘要：There is a new tooth failure mode for hardened gears called tooth flank fracture(TFF). ISO published a technical specification for calculating the load capacity of tooth flank failure in 2019. This failure mode is a fatigue phenomenon with initial crack initiating in the transition zone between the case hardened layer and the tooth core. Its failure mechanism is different from the traditional pitting and tooth root breakage fatigue failure modes. The main characteristics，research status，calculation methods and main influencing factors of tooth flank fracture failure are summarized. It provides a theoretical basis for understanding tooth flank fracture failure.关键词：Hardened gears;Tooth flank fracture;Shear stress;Material exposure value
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发布时间：2022-10-04
Review
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