最新刊期
期 1 ， 2022
- 摘要：With the increasing requirements of power density，load capacity and service life of gear transmission for aviation，wind power and other equipment，gear contact fatigue failure has become an important bottleneck limiting the service performance and reliability of modern gear equipment，and the material microstructure characteristics determine the fatigue performance of gear and other service parts. Through the surveys of the current related research situation both at home and abroad，the main microstructure features of gear materials such as retained austenite，carbide，grain size and their influence on the contact fatigue performance of gears are introduced. The reported numerical simulations of gear contact fatigue based on microstructure modeling and micromechanics constitutive model are summarized to describe the microscopic mechanical behavior of in gear contact fatigue，and to improve the understanding of the key characteristics and mechanism of gear fatigue. The various contact fatigue failure forms of gears occurred in the engineering practice are expounded in detail，and the main factors affecting the contact fatigue failure of gears，the induced microstructure evolution and degradation of mechanical properties，as well as the potential mechanisms of the gear contact fatigue failure，are analyzed. This review aims to provide the further understanding of the relationship between microstructure evolution characteristics and mechanical property degradation during the service process of gears，as well as the internal mechanism of contact fatigue failure，and providing the reference for anti-fatigue design and manufacturing method of high-performance gears.关键词：Gear transmission;Contact fatigue;Microstructure;Performance degradation;Failure mechanism
- 11
- |
- 9
- |
- 0
发布时间：2022-09-23
Review
- 摘要：Aiming at the inconsistency evaluation standards caused by using the gear designed by theory for simulation and using the gear produced by actual production for roll inspection certificate test，by using the NURBS surface fitting method，the real tooth surface is reconstructed and the construct of the 3D model in CATIA software is carried out. The Abaqus software is used to analyze the error of the hypoid gear transmission of the real tooth surface，and the transmission error of the real tooth surface meshing and the pure theoretical tooth surface meshing is compared，the existence of real tooth surface error and its negative influence on transmission error are verified. Changing the installation error of the gear found that the influence of the shaft angle error，the small wheel installation distance error，the offset distance error and the large wheel installation distance error on the transmission error decreased in turn. The rationality of the real tooth profile simulation model is verified by the rolling machine experiment.关键词：Hypoid gear;Real tooth surface;Transmission error;Installation error;Sensitivity
- 6
- |
- 3
- |
- 0
发布时间：2022-09-23 - 摘要：Gear skiving is an efficient gear cutting technology，and the tool working angle is an important parameter affecting the cutting performance. Due to the involving complex kinematics relation and cutting tool geometry in skiving process，tool working angle changes continuously and is affected by several factors. Primarily，the kinematics model is established based on gear skiving principle and coordinate transformation method. And the mathematical model which specifying the forming flank，rake face and cutting edge of the skiving cutter is proposed according to the geometric configuration of skiving cutter. The calculation formulas of the working rake angle and relief angle of the skiving cutter are derived by bringing in the definition of tool working angle in oblique cutting model. It is capable of realizing analytically express the evolution process of the working angle of gear skiving cutter. Finally，the influence of the designed rake angle and the helix angle of the skiving cutter on the working angle is analyzed. The results show that the designed rake angle tends to affect the working rake angle，while the helix angle of skiving cutter is more conducive to the relief working angle，and the analysis results can provide theoretical support for tool structure optimization for skiving cutter.关键词：Gear skiving process;Cutting tool geometry;Working angle;Evolution of angle
- 8
- |
- 7
- |
- 0
发布时间：2022-09-23 - 摘要：Crack fault will affect the time-varying meshing stiffness of the gear，and cause the vibration response of gear transmission system. Taking the wind turbine gearbox as the research object，considering the misalignment of gear root circle and base circle，an improved energy method is used to calculate the time-varying meshing stiffness of each gear pair. Based the improved method，the influence of sun gear crack on meshing stiffness is calculated and analyzed. Wind turbine gearbox operates in a natural wind load environment，and is excited by time-varying speed and torque. The translation-torsional-axial coupling model of wind turbine gearbox is established by using the lumped parameter method and considering backlash，time-varying meshing stiffness，meshing error parameter. The Runge-Kutta method is adopted to get the system dynamics response，and the order analysis of the response is carried out. The influence of the sun gear crack fault on the vibration response of wind turbine geatbox is obtained，and the fault failure mechanism of sun gear crack fault of wind turbine gearbox is studied. The conclusions provide theoretical reference for online monitoring and fault diagnosis of wind turbine gearbox.关键词：Random wind load;Root crack;Meshing stiffness;Order analysis;Wind turbine gearbox
- 6
- |
- 3
- |
- 0
发布时间：2022-09-23 - 摘要：A sufficiently refined mesh at the stress position is the basis for finite element analysis of gears to obtain accurate tooth surface contact stress and tooth root bending stress. While ensuring the accuracy of finite element analysis results，it is one of the hot research issues to reduce the solution time and the requirements on computer performance. The mesh of tooth surface and tooth root is refined based on Ansys software mesh division method，and the finite element modeling and simulation analysis are carried out by using multipoint constraint （MPC） method to coupling the degree of freedom of mesh nodes with different sizes. The results show that this method can greatly reduce the numbers of mesh and nodes，shorten the calculation time，and ensure the accuracy of calculating the tooth root bending stress and the tooth surface contact stress. Secondly，the results of calculating the tooth root bending stress and the tooth surface contact stress of the herring gear according to the ISO calculation standard are both large than finite element analysis，which provides important reference for engineering practical application of herringbone gear.关键词：Herringbone gear;Finite element mesh;Multipoint constraint method;Contact stress;Bending stress
- 7
- |
- 3
- |
- 0
发布时间：2022-09-23 - 摘要：Combining the principle of generating tooth surface of involute tooth profile curved cylindrical gear，the arc radius of the concave tooth surface of curved tooth cylindrical gear is increased，the equation to calculate cylindrical gear surface is deduced，and curved tooth cylindrical gears with different cross-section single tooth thicknesses and axes are obtained. Using curved tooth cylindrical gears as imaginary tools to derive equation for curved tooth gear surface. The face-gears with or without tooth line modification are compared，and the inner diameter analysis is carried out. The conclusion shows that the original face gear is maintained when the design parameters remain unchanged，the tooth thickness at the inner diameter of the modified face gear and the original face gear differ by 0.113 mm，and the single tooth thickness of the face gear gradually increases from inside to outside along the tooth width. Besides，the outer diameter end surface of the modified curved tooth face-gear is not pointed. Instead it is flat，to avoid the sharpening of the outer diameter tooth tip of the modified face gear. Therefore，the modification of the pinion tooth trace can increase single tooth thickness of face gear，improve the transmission strength of face gear，and provide a theoretical basis for anti-eccentric load and meshing characteristics of curved tooth face gear generated by the subsequent tooth trace modification.关键词：Sectional involute tooth profile;Curved tooth cylindrical gear;Tooth trace modification;Face gear;Inside diameter verification
- 3
- |
- 3
- |
- 0
发布时间：2022-09-23 - 摘要：In light of low sensitivity of fuzzy entropy in extracting degraded features of rolling bearing，an improved fuzzy entropy based on the sigmoid-like function is proposed. Aiming at the localization issues of assessment methods for traditional rolling bearing performance degradation，a novel performance degradation evaluation method based on grey relation is proposed. This method uses grey relation theory to evaluate the relationship between extracted rolling bearing degradation characteristics and reliability，so as to achieve the purpose of evaluating the degradation features of rolling bearing from the overall perspective of rolling bearing reliability evolution. The experimental results show that the improved fuzzy entropy can accurately extract the performance degradation features of rolling bearing，and the rolling bearing degradation features extracted based on the improved fuzzy entropy have a consistent evolution law with the rolling bearing maintaining reliability，with a credibility level above 95%.关键词：Rolling bearing;Degradation characteristic;Fuzzy entropy;Reliability;Grey relation
- 3
- |
- 4
- |
- 0
发布时间：2022-09-23 - 摘要：The contact path and transmission error are key indexes for evaluating the meshing performance of spiral bevel gears. The contact path is offset by misalignment，and symmetry and fluctuation amplitude of transmission error change. Therefore，based on installation adjustment，an optimization method for the contact path and transmission error of spiral bevel gears is proposed. The equations are established by the constraining assembly conditions and the initial transmission ratio，and then the theoretical installation adjustment is solved. A tooth contact analysis （TCA） algorithm with the misalignment is built by introducing gear pair misalignment. Taking the misalignment as the design variable and presetting the characteristic parameters of contact path and the transmission error，an objective function is built and solved by the nonlinear optimization algorithm. The optimization results show that the contact path is moved to the small end and the loaded contact area is expanded to the middle of the tooth flank，load bearing contact performance is improved. That the droop deviation and fluctuation amplitude of the transmission error curve are decreased，whichis beneficial to avoid edge contact and improve dynamic performance.关键词：Spiral bevel gear;Misalignment;Tooth contact analysis;Contact path;Transmission error
- 4
- |
- 6
- |
- 0
发布时间：2022-09-23
Theory·Reserach
- 摘要：In response to the needs of the health care industry，based on the modular design method，the multifunctional nursing bed is divided into modules and functions are analyzed，and the overall plan design of the multifunctional nursing bed is completed. Based on the principle of ergonomics，the back lifting mechanism is researched. By analyzing and comparing the advantages and disadvantages of the existing back lifting mechanism，a two-fold back lifting mechanism is designed，and the corresponding mathematical model of motion is established. With the help of Matlab,the theoretical motion analysis is carried out, and it is compared with the simulation results of Adams kinematics to verify the rationality of the mechanism design. With the help of Ansys，a finite element analysis is carried out on the key components of the back lifting mechanism to ensure the safety of the mechanism，and an experimental prototype was made for verification.关键词：Modularity;Nursing bed;Mechanism design;Kinematics analysis
- 9
- |
- 3
- |
- 0
发布时间：2022-09-23 - 摘要：The rotor shaft vibration of the helicopter transmission system is an important factor affecting its operational reliability. In order to improve the safety margin of torsional vibration of the rotor shaft system of a coaxial counter-rotating double-rotor transmission system，under the premise of considering the lightweight design，by changing the shaft section diameter size or changing the excitation frequency makes the natural frequency of torsional vibration stagger with the excitation frequency，so as to avoid resonance and realize the optimized design of shafting torsional vibration frequency modulation. The torsional vibration safety margin of the optimized shaft system reaches more than 10%，and the torsional vibration characteristics are effectively improved. The calculation and optimization methods have certain guiding significance for the improved design of the rotor shafting of the helicopter transmission system.关键词：Helicopter;Shafting;Torsional vibration;Optimal design
- 6
- |
- 3
- |
- 0
发布时间：2022-09-23 - 摘要：Traditional feet robots have shortcomings of mechanism flexibility insufficient in adaptive walking on complex terrain. A bio-tensegrity foot mechanism is proposed for promoting the performance of adaptive terrain and stable locking locomotion of the conventional foot robots on sloped terrain based on the similarity between musculoskeletal systems and a tensegrity structure. The equivalent mapping model of a tensegrity structure is established by the matching of tension unit，the design of configuration of the mechanism achieved by the method of bionic design，a physical sample is made and an experimental platform is built. The results show that the proposed bionic foot mechanism has good flexibility and stability，the adaptive and stable walking ability of the traditional foot robot on slope terrain are improved.关键词：Tensegrity structure;Bioinspired design;Adaptive motion;Locking mechanism
- 4
- |
- 3
- |
- 0
发布时间：2022-09-23 - 摘要：In order to solve difficulties of going to bed and getting up for the elderly，a device is designed to assist them in going to bed. The track of the elderly's leg going to bed is analyzed. Based on mathematical modeling，the leg lift trajectory is simulated by intersection curves between spherical surface and conical surface，a spatial linkage is designed to help leg lift and its specific structure design and motion simulation are analyzed. The simulation results show that the device can realize leg lift trajectory and run smoothly，the theoretical feasibility is verified. The physical construction and practical test are carried out，it is proved that the device has clever mechanism and compact structure and can realize auxiliary leg lift，can be adapted to different bed types and has a broad application prospect.关键词：Leg lift;Space linkage;Motion simulation;Practical test
- 6
- |
- 5
- |
- 0
发布时间：2022-09-23 - 摘要：In light of low efficiency，uneven quality and high labor intensity in manual grinding large marine propeller blades in enterprises，a 2P3R type 5-DOF industrial robot for processing large marine propeller blades is proposed and its complete model is established. Taking the end-effector into account，the forward kinematics mathematical model of the robot is established by using an improved D-H method and the forward kinematics equation is obtained. Based on the Monte Carlo method，in the Matlab environment，the robot workspace is solved by using the robot toolbox，and the point cloud of the reachable workspace of the end cutter of the robot is depicted. Through the comparison of surface fitting and spatial inclusion，the results show that the designed 2P3R type 5-DOF industrial robot can achieve full coverage of the upper surface of a single blade of a large marine propeller with a diameter of 4~10 m，which lays a foundation for subsequent research on motion control and path planning of large propeller processing robots.关键词：2P3R type;Forward kinematics analysis;Monte Carlo method;Workspace;Surface fitting;Space inclusion
- 5
- |
- 3
- |
- 0
发布时间：2022-09-23 - 摘要：A 2-CRR/UPU parallel mechanism is proposed for apple sorting and packing. A kinematic spiral matrix of 2-CRR/UPU parallel mechanism is established，its degree of freedom is analyzed by the spiral theory，and a modified Kutzbach-Grübler formula is used for verification. Through the geometric relations of the mechanism，the inverse solution of the position of the mechanism is solved，and then the Jacobian matrix of the mechanism is derived and its velocity is analyzed. The workspace of the mechanism is solved by 3D dynamic search method. The singularity of the mechanism is analyzed by Jacobian matrix，and the distribution law of the dexterity index in the workspace is obtained. The 2-CRR/UPU parallel mechanism can carry out three translational motions，and the motion is stable，which can meet the action requirements of apple sorting and packing.关键词：2-CRR/UPU parallel mechanism;Inverse position solution;Workspace;Singularity;Dexterity
- 3
- |
- 3
- |
- 0
发布时间：2022-09-23
Design· Calculation
- 摘要：Meshing clearance is one of the key factors affecting the transmission performance of cycloid-pin planetary drive such as load capacity，frictional power，vibration and noise. By using the principle of mesh between cycloidal gear and pins，the analysis model is well built for analyzing contact force and frictional power loss of cycloid gear and pin considering meshing clearance. By introducing comparisive coefficient，the influence of meshing clearance on contact force and frictional power of cycloid-pin pair is described. The analysis results show that the meshing clearance will significantly change the number of pins in the contact，thus changing the peak of contact force and frictional power loss，the increase of meshing clearance will lead to a significant rising of the peak contact force，but the frictional power loss will be slightly reduced. This method can provide a simple theoretical method for evaluating the influence of initial and worn clearance on contact characteristics of cycloid-pin pair.关键词：Cycloid-pin gear;Meshing clearance;Gear tooth contact force analysis;Friction power loss
- 6
- |
- 3
- |
- 0
发布时间：2022-09-23 - 摘要：As one of weakest link of harmonic reducer，flexspline has always been the object of concern in the reliability research of harmonic reducer. The CSG-32-80 harmonic reducer is taken as the object，and the transient analysis of the flexspline is carried out by using Ansys Workbench. The distribution of stress and strain of the flexspline is obtained. The results of finite element analysis is imported into Ncode Designlife fatigue analysis module，and the fatigue life of flexspline is obtained by combining S-N Stress-Life curve of flexspline material. The relationship between the maximum stress and the length，wall thickness and tooth width of the flexspline are explored by orthogonal experiment. It provides a theoretical reference for the optimal design of flexspline structure.关键词：Flexspline;Finite element analysis;Fatigue life;Mechanical property;Orthogonal experimental design
- 7
- |
- 4
- |
- 0
发布时间：2022-09-23 - 摘要：In order to find out the thermo-elastohydrodynamic lubrication characteristic of internal meshing gear transmission，considering the influence of various gear transmission types and different modification coefficients，an elastohydrodynamic lubrication model for the internal meshing gear transmission is established to analyze the thermo-elastohydrodynamic lubricating characteristics of internal meshing gear system. The research shows that compared with other transmission types，for the modified internal meshing gear system，when the positive transmission is realized，the lubrication effect of the gear system is the best，the thick lubricating oil film can be formed between the meshing gear teeth，the friction coefficient between the gear teeth and the highest temperature rise of the oil film are the least，and the thermal adhesive bearing capacity is the strongest. When positive transmission is realized，appropriate increment of the modification coefficient can further improve the lubrication characteristics of the tooth surface，but at the same time reduce the oil film stiffness.关键词：Internal meshing gear;Modification coefficient;Lubricating characteristic;Oil film stiffness
- 4
- |
- 3
- |
- 0
发布时间：2022-09-23 - 摘要：Splash lubrication is the most important lubrication method in gearbox of EMU at present，it is of great significance to study the law of flow field distribution for gear box lubrication. A simulation test platform for splashing lubrication flow field of gearbox is established after simplifying the gearbox of EMU，and splash lubrication capture test is carried out. Based on the theoretical knowledge of computational fluid mechanics，a three-dimensional numerical analysis model of the flow field simulation test platform is established by using PumpLinx software. The reliability of the three-dimensional numerical analysis model is verified by the comparison between the test and the simulation. Finally，the simulation and prediction of the flow field of the lubricating oil in the gearbox of a EMU during going up，down and turning are realized.关键词：EMU gearbox;Simulation test platform;Lubricating oil flow field
- 4
- |
- 3
- |
- 0
发布时间：2022-09-23 - 摘要：Taking hydrodynamic sliding bearing as the research object，models of hydrodynamic lubrication and mixed lubrication are established. The characteristic parameters such as friction force，friction coefficient，load-carrying capacity and temperature rise of lubricating oil are obtained by finite difference method for numerical solution，then lubrication state of bearing could be judged by friction coefficient and film thickness ratio，the influence of surface roughness on bearing characteristics after lubrication state transformation is analyzed，and the running-in experiment of mixed lubrication friction pair is carried out under mixed lubrication based on M2000 friction and wear tester. The results show that as the eccentric ratio increase，the lubrication state of the bearing will transform to mixed lubrication from hydrodynamic lubrication at low rotary speed; the rough peak contact in mixed lubrication state can improve load-carrying capacity，but lead to rapidly increase of bearing friction force and oil temperature; the experimental results are consistent with the theoretical results of mixed lubrication under high eccentric ratio.关键词：Mixed lubrication;Lubrication state;Sliding bearing;Surface roughness
- 6
- |
- 3
- |
- 0
发布时间：2022-09-23 - 摘要：In order to improve the transmission efficiency of the rubber CVT and better match the power performance of the engine and the whole vehicle，the bench test of the engine and CVT is carried out，and the curves of starting motor，external characteristics of CVT and influencing factors of CVT are drawn. The results show that，without changing the structure of the CVT，the temperature is the main factor that influence the efficiency of the CVT，and at the age of 55 ℃ CVT maintain a high efficiency. According to the driving force curve drawing CVT external characteristic curve，determine the total transmission ratio for the gear reducer is 12.9，and determine the CVT light left block and the combination of the heavy spring can make the car can quickly reach the highest speed.关键词：CVT;Efficiency promotion;Power matching
- 4
- |
- 3
- |
- 0
发布时间：2022-09-23 - 摘要：The cutting part planet carrier is the key part of the shearer，and its time-varying reliability has an important influence on the comprehensive performance of shearer. Rigid-flexible coupling model of shearer with planetary carrier as modal neutral file is established based on Pro/E，and weak areas and dynamic stress of the cutting part planet carrier are obtained by studying the dynamics performance of the planetary carrier. The probability density function of the three-parameter Weibull distribution in the weak region of the cutting part's planet carrier is obtained by Matlab and the rationality of its fitting is verified with Kstest function. According to the fatigue life reliability theory，the fatigue life reliability model of planetary carrier is established. By calculation，the time-varying reliability of multiple weak areas of planetary carrier based on Copula function is to degrade exponentially from 0.936 2 until the failure of the planetary carrier. Combined with reliability sensitivity design theory，the influence of multiple weak areas design variables on the time-varying reliability of the cutting part planet carrier is analyzed. This provides theoretical basis and accurate data support for related research on the planet carrier.关键词：Shearer;Cutting part planet carrier;Rigid-flexible coupling;Fatigue life;Reliability
- 4
- |
- 6
- |
- 0
发布时间：2022-09-23
Test·Analysis
- 摘要：Difficulties are always encountered when distinguish the fault types in the planetary gearbox diagnosis. A new fault diagnosis method with implementation of wavelet time-frequency diagram and convolutional neural network is proposed. At first，the continuous wavelet transform is used on the original signal to obtain the wavelet time-frequency diagrams. Secondly，the wavelet time-frequency diagrams are processed and compressed，the processed wavelet time-frequency diagrams are input into the convolutional neural network to classify and identify. Finally，the wavelet basis function and convolution neural network parameters are adjusted in order to get an ideal diagnosis model. Experimental results show that the proposed method has better diagnostic accuracy and robustness than the BP neural network when the speed of training set data and test set data is different. This approach provides a reference for planetary gearbox fault diagnosis.关键词：Planetary gearbox fault diagnosis;Continuous wavelet transform;Wavelet time-frequency diagram;Convolutional neural network
- 5
- |
- 4
- |
- 0
发布时间：2022-09-23 - 摘要：Taking RV-40E reducer as the object，the dynamic characteristics of RV reducer under free mode are studied by combining modal simulation and modal analysis experiment. Firstly，the RV reducer is modeled and simulated based on Ansys，and the simulation results of natural frequency and mode shape are obtained. After comparing the experimental modalities of the domestic and Nabtesco RV-40E reducer，the test results show that the first-order modal of domestic RV-40E reducer is generally lower than that of Nabtesco，with a maximum difference of 11.1%. At the same time，the simulation and experimental results are compared. The largest domestic difference in the first-order mode is -5.8%，and that of Nabtesco is +5.9%. The above research provides effective data and methods for the structural optimization design and modal performance analysis of the RV reducer.关键词：RV reducer;Finite element;Modal analysis;Modal experiment
- 4
- |
- 3
- |
- 0
发布时间：2022-09-23 - 摘要：Cycloid gear tooth profile modification is very important to the performance of RV reducer，in order to select the shape modification method and parameter size reasonably and improve the stress state of the cycloid tooth surface，an equidistant & radical-moving modification method based on particle swarm optimization algorithm to optimize bearing capacity is proposed. Based on the RV-60E reducer as an optimization example，the mechanical analysis of the cycloid needle wheel transmission part is carried out first，and the mathematical model of the cycloid wheel shape is established with the goal of reducing the maximum bearing capacity of the needle teeth. The required shape modification parameter values and tooth profile curve are obtained by using the proposed optimization design method. Compared with equidistant trimming，radical-moving and angle fitting modification methods，it is found that the maximum contact force of cycloidal gear profile modification method based on particle swarm optimization algorithm is reduced by 15.9%，16.0% and 11.8%，respectively，thus improving the bearing capacity and life of RV reducer.关键词：RV reducer;Optimal design method;Cycloidal gear tooth profile;Equidistant & radial-moving modification;Carrying capacity
- 3
- |
- 5
- |
- 0
发布时间：2022-09-23
Development·Application
- Technical support is provided by Beijing Founder electronics co., LTD 豫ICP备05013835号-5
京公网安备11010802024621 - It is recommended to read the content of this site in Chrome&IE9+. Please switch to extreme mode in browser 360.
- Cookies We use cookies to help provide and enhance our service and tailor content. By continuing, you agree to the use of cookies.
0