最新刊期
期 7 ， 2019
- 摘要：In order to improve the indexing accuracy of CNC gear shaper YKD5132X3, the transmission error of gear shaper is detected. After analyzing the data, it is concluded that the main error sources of indexing error are workpiece worktable worm gear and cutter stand worktable worm gear pair. Aiming at these two error sources, the two worm gears are processed by the refined worm wheel master machine of our research group, and the on-line detection is realized through the on-line detection device. After the worm gear is finished, when the gear shaper is assembled, the installation of the workpiece worm gear is adjusted by TE data. The method of adjusting and installing many times in the past is replaced, which saves the installation time and improves the installation precision. Finally, the gear cutting accuracy of gear shaper is improved from 7-level to 5-level.关键词：CNC gear shaper;Transmission error detection;Worm gear pair;On-line measuring device;Worm gear machine tool
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发布时间：2022-09-24 - 摘要：In view of the limitation of current mainstream methods of gear crack fault detection (that is only using the system response as research object, and seldom considering the input effect on fault feature extraction), and taking into account its dynamic characteristics as a kind of typical nonlinear system, by applying Volterra series theory into different states of gear meshing transmission system, for fully taking the advantage of Volterra series, which can use both the input and output data of system to describe the nonlinear characteristics of system. Meanwhile, using the high global search capability of QPSO algorithm, QPSO algorithm is used to identify the time domain kernel of gear meshing transmission system’s Volterra model(referred to as GIRF). The simulation results show that the high-order GIRFs are very sensitive to the nonlinear characteristics of the system caused by the gear crack failure, and can effectively characterize and distinguish the nonlinear dynamic characteristics of the gear meshing transmission system under different conditions. The simulation results achieve the expected purpose.关键词：Volterra series;QPSO algorithm;Gear crack;Fault feature extraction
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发布时间：2022-09-24 - 摘要：In order to depict the numerical characteristic of the attractor structure in phase space for gear system effectively, a nonlinear dynamical spur gear transmission model including backlash and general transmission error is established, the calculation formula of equispaced gear system correlation dimension is deduced based on G-P algorithm. The numerical characteristics are explored quantitatively for both of periodic attractor and chaotic attractor by employing largest Lyapunov exponent as well as correlation dimension, the evolution and migration process of chaotic attractors is analyzed by means of Poincaré section. The evolution of chaotic attractor under the excitation of damping ratio and general transmission error is described by correlation dimension. The results show that the more complex of attractor structure generates the larger correlation dimension values, and causing strong vibration to the system, correlation dimension of chaotic attractor is between integer 1 and 2 with fractal characteristic.关键词：Correlation dimension;Lyapunov exponent;Poincaré section;Chaotic attractor
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发布时间：2022-09-24 - 摘要：By analyzing the principle of FA transmission and its structural characteristics, taking FA45-29 reducer as the research object, and the three-dimensional model of simplified model of the prototype is built and virtual assembly is carried out without interference. By importing Hypermesh for detailed mesh generation, contact definition and constraint addition, the finite element model is established, and then importing ANSYS for modal analysis under constraint conditions. The natural frequencies and mode shapes are obtained, which not only avoids complex theoretical modeling and calculation, but also lays a foundation for the subsequent dynamics analysis and rigid-flexible coupling analysis. At the same time, it provides a theoretical basis for the evaluation of the dynamic performance of FA reducer, the design of experimental scheme and the structural optimization design of all parts of the reducer.关键词：FA45-29 reducer;Detailed mesh generation;Modal analysis of the whole reducer
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发布时间：2022-09-24 - 摘要：A volumetric Kalman filter estimation algorithm with good real-time accuracy and stability is used to identify the quality of electric bus and road gradient in complex environment. A dynamics model of 4-gear automated mechanical transmission is established, and an economical shift strategy is proposed which is based on the fusion of four parameters: vehicle speed, throttle opening, vehicle quality and road gradient. The simulation results show the identification algorithm proposed can identify vehicle quality and road gradient accurately without adding any sensors. The multi-parameter fusion shifting strategy developed can achieve economical shifting under the condition of guaranteeing vehicle dynamic performance, which can avoid frequent shift, reduce component wear and improve ride comfort to a great extent.关键词：Pure electric bus;Automated mechanical transmission;Kalman filter;Economic shift
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发布时间：2022-09-24 - 摘要：In view of the structural characteristics of spherical 3-DOF parallel mechanism, which all the joints are rotating joints and the joint axes intersect at one point, the position of the component is expressed by quaternion by means of the corresponding relationship between the long arc on the sphere surface and quaternion algebra. The product of quaternions is used to describe the component position change caused by joint rotation, and the direction cosine of the joint axis is obtained through the corresponding relationship between the geometric addition of the long arc on the sphere surface and the multiplication of quaternions, thus the constraint equation of the robot is established. The constraint equation is proceed subtly by a clever variable, which reduced the data in the symbolic operation of MATLAB, solved the problem that the effective results could not be obtained when the operation exceeded the computer memory, and the positive closed equation of the robot is established. By using the influence coefficient method, the transfer relation between the angular velocity and angular acceleration of the robot active component and the corner cone on the end component is established. The examples show that, there are 8 kinematics solutions for the given position of the active component in the top pyramid group. And according to the example of the continuous motion of the active robot component, the changing course of angular velocity and angular acceleration in the position of the top pyramid is simulated.关键词：Spherical parallel robot;Quaternion algebra;Positive closed equation;Influence coefficient
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发布时间：2022-09-24 - 摘要：A fully symmetric 4-URU parallel mechanism with 3T1R motion is studied. Based on the screw theory, the degree of freedom of the mechanism is verified, the mathematical model of the positive and negative solution of the mechanism position is established, and the singular configuration of the mechanism is obtained. The workspace of the mechanism is solved by the numerical search method. The key scale parameters of the mechanism are optimized by examining the influence of various scale parameters on the workspace. The results of numerical calculation and motion simulation show that the kinematics model and performance analysis are correct and reasonable, and the results can provide references for mechanism mechanics analysis, structure design.关键词：3T1R motion;Kinematic performance;Scale optimization
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发布时间：2022-09-24 - 摘要：The spatial trajectory and pose planning of manipulator is often completed by interpolation calculation. In order to realize spatial curve trajectory and pose planning, a kind of method is put forward that the pose of the eoat in discrete points of the spatial circular curve is obtained, and Cardan angles are worked out and fitted in Matlab by calculating discretely the Frenet frame of the spatial circular curve expressed by the parameter equation. Based on the parameters of the Kawasaki BA006N six degree of freedom manipulator body mechanism, a manipulator simulation platform is built in Adams. The driving functions including the spatial circle parameter equation and the fitting Cardan angle parameter equation are applied to the eoat as the general driver. The simulation analysis shows that the spatial circular curve trajectory and pose can be traced well by the eoat. The angular displacement, the angular velocity, the angular acceleration and the torque of the six joints of the manipulator are extracted by Adams. This method not only avoids the inverse kinematics calculation, but also provides a new method for the design of the control system and the planning of other spatial curves and surfaces.关键词：Spatial circular curve;Frenet frame;Cardan angle;Trajectory;Pose;Adams
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发布时间：2022-09-24 - 摘要：In order to reduce the fuel consumption rate of the engine and improve the efficiency of the transmission system, the optimal power shift path is calculated. The dynamic model of engineering vehicle transmission system is established and the dynamic shift strategy is simulated. The simulation shows that the optimal dynamic shift strategy can improve the acceleration and dynamic performance of the vehicle and greatly improve the shift quality of the vehicle. Improve the fuel economy of engineering vehicles, so that the overall energy saving effect of the whole machine is better. The test results show that the speed change of gearbox before and after the shift is relatively gentle, indicating that the new dynamic shift strategy can reduce the gearbox shift time, and the dynamic response of the gearbox is effectively improved during the operation of the engineering vehicle. It shows that the improved BP neural network control method can effectively control vehicle automatic shift. The research results have important theoretical and practical significance for improving the dynamics, economy and intelligence of engineering vehicles.关键词：Automatic shift;Dynamic characteristic;BP neural network;Gearbox
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发布时间：2022-09-24
Theory·Reserach
- 摘要：During the gears meshing process, the Time Varying Meshing Stiffness (TVMS) is affected by the relative displacement. An algorithm of TVMS considering two translational degrees of freedom is proposed. The algorithm is based on the potential energy method for the ideal involute spur gear. The translational freedom is introduced into the calculation of TVMS by considering the influence of translational freedom on the angles in gear meshing. The effect of gears relative displacement on the maximum, mean and contact ratio of TVMS is studied. The results show that TVMS is most sensitive to the relative translation of gears along the vertical direction of the meshing line, and is least sensitive to the relative translation of gears along the direction of the meshing line. In the vertical direction of the meshing line, the 0.1 mm relatively movement can cause 0.93% change of the mean of TVMS.关键词：Translational freedom;Time varying mesh stiffness;Potential energy method;Ideal involute gear;Spur gear
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发布时间：2022-09-24 - 摘要：Aiming at the dual duplex spread blade method for cutting spiral bevel gears, the midpoint of the tooth space of pinion is treated as the reference point for the bilateral modification tooth surfaces. The target tooth surface is constructed to meet with the meshing performance by predetermining of the meshing parameters. The mathematical model and constraint function of the target tooth surface errors based on the optimization of machining tool setting are constructed. The nonlinear constrained optimization function is used to derive the machining parameters of the gear. The optimized method is verified by tooth contact analysis and finite element contact analysis. The simulation results show that the meshing performance meets the expected requirements after the tooth surface modification.关键词：Dual duplex spread blade method;Spiral bevel gear;Bilateral modification;Reference point
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发布时间：2022-09-24 - 摘要：Based on the structure optimization software OptiStruct and commercial finite element analysis software Abaqus, combined with the theory of topology optimization, dimension optimization and finite element contact analysis, an innovative lightweight design method of gear web structure is proposed to solve the problem of overweight of aeronautical gear. Taking the transmission gear of an aeroengine accessory as the research object, the web structure is designed by topology optimization and dimension optimization based on OptiStruct software. The contact performance of the gear is calculated by Abaqus software. The flow chart and key technology of lightweight design of the web structure are given. The actual optimal design results show that under the condition of guaranteeing strength and transmission error, the overall weight of the gear is reduced by 39.6%, and the effect of weight reduction is obvious, thus realizing the goal of gear lightweight design.关键词：OptiStruct-Abaqus software;Gear;Topological optimization;Size optimization;Lightweight
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发布时间：2022-09-24 - 摘要：Aiming at the sawtooth cutting mechanism of traditional reciprocating saw, a new type of kinematic mechanism of arc cutting reciprocating saw with curve face gear pair is proposed. By using the meshing and coordinate transformation principle of curve face gear pair, and combining with mechanical principle, gear meshing theory and modern design method, the transmission coordinate system of the compound kinematic mechanism with curve face gear pair and connecting rod is established, the motion equation of the compound kinematic mechanism is deduced, the influence of displacement, velocity and acceleration on the compound kinematic mechanism of arc cutting reciprocating saw and its variation law are analyzed. By using the software of SolidWorks and Adams, the kinematic simulation model of the arc cutting reciprocating saw is established, the kinematic characteristic law of the reciprocating saw is obtained. The corresponding experimental bench is built and tested, and the theoretical simulation data and experimental results are compared with the theoretical analysis results to verify the feasibility of the reciprocating saw mechanism with curved gear pair at the end. The corresponding experimental bench is built and the test is carried out, and the theoretical simulation data and experimental results are compared with the theoretical analysis results, the feasibility of the arc cutting reciprocating saw mechanism with curve face gear pair is verified.关键词：Electric reciprocating saw;Curve face gear pair;Arc cutting;Kinematic characteristic
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发布时间：2022-09-24 - 摘要：Based on the position feature set theory and decoupling principle of parallel mechanism, a new kind of structure decoupled parallel mechanism with hybrid driving and local motion decoupling is designed and its movement is one translation and three rotations (1T3R). The topological structure of the parallel mechanism is analyzed, the type of the position feature set of the moving platform is obtained and the degrees of freedom and coupling of the mechanism are solved. The explicit analytical expressions of the positive and inverse solutions of the position of the mechanism are obtained by using the spatial projection principle and the pose transformation matrix method. The numerical examples of the positive and inverse solutions of the position of the mechanism are obtained by using MATLAB software programming and the results are completely consistent, indicating that the position inverse solution model is correct and reliable. The angular displacement curves of the mechanism are obtained by using MATLAB software programming and Adams software motion simulation and their results are the same, which verifies the correctness of the theoretical analysis model of motion. Based on the 3D motion simulation model, the angular velocity and angular acceleration curves of the mechanism are obtained.关键词：Parallel mechanism;Zero coupling degree;One translation and three rotation;Positive and inverse solutions of kinematics
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发布时间：2022-09-24 - 摘要：To increase off-axis stiffness and rotating angle, a double-decker rotating flexible hinge is designed, with straight beams and curved plates combined as the flexible body. The model of rotational stiffness is established by pseudo rigid model of fixed-oriented beam and the equivalent method of series and parallel spring. The model of off-axis stiffness is established by the pseudo rigid body method. Then a finite element simulation model is established by using ANSYS software, and compared with the theoretical model. The results show that the rotational stiffness error is about 7% and the off-axis stiffness error is about 3%, which can prove the correctness of the stiffness models. The statics performance of the flexible hinge is clear by analyzing rotating stiffness and off-axis stiffness, whose off-axis stiffness is 2 N/mm and rotating angle is 30°.关键词：Flexible hinge;Pseudo-rigid-body method;Stiffness model;Finite element;Double-decker
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发布时间：2022-09-24 - 摘要：Redundantly driven parallel mechanisms have been increasingly used in practical production because of their greater stiffness and force maneuverability. Based on 3-RPS parallel mechanism，a redundant parallel mechanism with five-bar closed-loop structure limbs is proposed. Through the analysis of the structure and movement of closed-loop limbs，combined with mathematical derivation and Matlab，the overall kinematics performance of the mechanism is analyzed. According to the results of kinematics，compare the workspace situation of the mechanism with the redundant limbs and without the redundant limbs. The results show that the redundant limbs will reduce the workspace of the mechanism，and the overall reduction is about 20%. However，due to the increased stiffness of the mechanism， the mechanism still has obvious advantages within the scope of work， and it also provides a new configuration and theoretical basis for the research of redundantly driven parallel mechanisms in the future.关键词：Redundantly driven;Closed-loop limb;Parallel mechanism;Workspace
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发布时间：2022-09-24 - 摘要：The parallel mechanism of four-degree-of-freedom (4-DOF) 4PPaRR is proposed. Then its topological characteristic of analysis 4PPaRR parallel mechanism is performed based on the theory of position and orientation characteristic (POC), and the degree of freedom and motion property are validated by it. The inverse kinematics of the mechanism is analyzed, and the workspace of the 4PPaRR parallel mechanism is solved by numerical method. Then a performance index is defined in order to analyze the rotational capacity of 4PPaRR parallel mechanism, The scale optimization of parallel mechanism size is carried out based on Grasshopper Optimization Algorithm（GOA）in the end. The research results show that the 4PPaRR parallel mechanism has larger workspace and rotation capability. The optimization results can provide a theoretical basis for later prototype development and trajectory planning.关键词：Parallel mechanism;Position and orientation characteristic;Workspace;Parameter optimum
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发布时间：2022-09-24 - 摘要：In order to improve the efficiency and success rate of rescuing the wounded in the complex and catastrophic environment, a novel 4-UPS/PS parallel mechanism with 3R1T is proposed, which can be used in self-balancing system of the transfer robot. The degree of freedom is analyzed by using screw theory and tested by the modified G-K formula. By utilizing the closed vector, the solution to the inverse kinematics and the relation between the length of each driving rod and the posture of the moving platform are obtained. The expressions of kinetic energy and potential energy of self-balancing compensating mechanism are deduced. The dynamic model of self-balancing compensator is established by Lagrange method. The kinematics and driving force of self-balancing process are simulated and analyzed by Adams simulation software. The experimental results show that the mechanism has excellent motion performance, good drive performance, strong controllability and stability, which is suitable for the rescue and transport robots.关键词：Wounded-transfer robot with self-balancing;Kinematics analysis;Dynamics analysis;Adams simulation
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发布时间：2022-09-24
Design· Calculation
- 摘要：The high speed and heavy load gear meshing transmission will cause temperature rise because of friction and heat. The gear will produce thermal expansion and cause meshing error, which makes the vibration and noise increase, and then aggravate the process of failure of gluing. Therefore, it is significant to calculate the temperature rise and analyze the influencing factors of gear transmission. The temperature rise will lead to the change of gear thermal physical property parameters and affect the temperature field. If this effect is ignored, an error will be generated. Based on involute spur gear, according to gear meshing theory and friction heat transfer principle, the instantaneous friction heat flow and convection heat transfer coefficient in the transmission process of gear are calculated and solved. The CALPHAD method is used to calculate the physical parameters at different temperatures. Based on the ANSYS thermosetting coupling calculation method, the calculation program under the variable physical parameters is compiled by APDL, the temperature rise of the gear transmission is calculated, and the change of temperature field in the gear transmission process is obtained. A parametric solution program is written, and the influence of tooth width and torque parameters on the temperature rise of meshing transmission is analyzed. The research provides an important basis for analyzing the influence mechanism of temperature rise on gear failure, and has certain guiding significance.关键词：Gear meshing transmission;Variation physical parameter;Temperature rise calculation;APDL;CALPHAD calculation method
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发布时间：2022-09-24 - 摘要：As an auxiliary fixture in the grinding process of slender shaft parts such as lead screw and crankshaft and so on, the self-centering center rest is of great significance to the processing accuracy of slender shaft parts. As an important part of the self-centering center rest, the reset mechanism is related to the positioning accuracy and service life of the self-centering center rest . A rigid reset plate mechanism is studied to realize close contact and timely reset between cam and clamp arm. The parametric design and simulation of reset plate is carried out, and its precise mathematical calculation model is obtained. The contour of the curve groove in the rigid reset plate of a self-centering center rest is solved by using MATLAB software. The correctness of the mathematical model of the reset plate and the feasibility of the design method are verified by using the collaborative virtual simulation functions of MATLAB, UG and Adams software.关键词：Self-centering center rest;Reset plate;Slender shaft;Profile curve;Virtual prototype
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发布时间：2022-09-24 - 摘要：The blast furnace top gearbox is the key equipment of the stock distribution of blast furnace. The quality of the blast furnace top gearbox is directly related to the quality and efficiency of the blast furnace iron making. The upper slewing bearing is an important bearing component of the blast furnace top gearbox, which connects the fixed end and the moving end. If the frame or the slewing bearing is slighted inclination, the central axis line of the rotating body will be deviated from the geometric central axis line, which causing the unbalance loading of the slewing ring. The eccentric slewing bearing is taken as the research object, the load calculation and equivalent are carried out. Then, the mathematical model is established and the analytic method is used to calculate the load distribution and deformation of the rolling elements inside the slewing bearing. The theoretical support for slewing bearings to withstand eccentric load research is provided.关键词：Slewing bearing;Blast furnace top gearbox;Central axis line;Eccentric load;Elastic deformation amount
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发布时间：2022-09-24 - 摘要：Taking an aero-engine gearbox with split torque transmission system and double helical gears as research object. Based on the finite element node method, the model of a split torque transmission system with considering the effects of the supporting shafts and bearings, gyroscopic effect of rotor, is constructed. The time-varying meshing stiffness of double helical gear is calculated by finite element method, and the static transmission error is calculated according to the measured tooth surface. According to the established system dynamics equation, the typical modal of gear train is calculated according to the vibration theory method, and the correctness of the calculated modal is verified by the test. The time-domain and frequency-domain response is simulated with NewMark method, the time-domain response of the system is convergent and the modulation phenomenon appeared. In the frequency-domain analysis, several high and low order components of mesh frequency, shaft frequency exist. The calculated results are basically consistent with the experimental results. The study work provides a valuable reference method for the dynamic performance analysis of aeronautical gear transmission.关键词：Double-helical gear;Split torque transmission;Modeling
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发布时间：2022-09-24 - 摘要：Due to higher stiffness, better dynamics performance, etc., the redundantly driven parallel mechanisms are increasingly used in various industries. A 3-DOF redundant parallel mechanism with a double-slider structure is proposed. Based on the direct position solution and inverse position solution, the kinematics equation of the mechanism is deduced separately, and the kinematics simulation are carried out by combining the inverse solution equation with MATLAB to draw the drive displacement and speed. Combining kinematics analysis results and direct position solution equations to analyze the workspace of the mechanism, and drawing the three-dimensional workspace of the mechanism. The results of kinematics and workspace show that the mechanism runs smoothly in the workspace, without sudden change in speed, displacement, etc., and the workspace has good symmetry about XOZ. The research results also provide the foundation for the practical redundant application of this configuration redundant parallel mechanism.关键词：Redundantly driven;Parallel mechanism;Kinematics performance;Workspace
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发布时间：2022-09-24 - 摘要：A thermal mixed lubrication model in plane contacts is developed and the local temperature rise is considered. The influence of temperature on lubricant film thickness, local pressure distribution, local temperature rise and the load sharing ratio of micro convex peak are analyzed by computing on Sinusoidal rough surface and Gaussian rough surface. The results show that, as the temperature rises, lubricant film becomes thinner, so that more micro convex peak contacts emerge and the rise of temperature increases. As a result, the load carried by micro convex peak increases gradually, the local temperature rise increases, the load carried by the micro convex peak increases gradually. However, the load carried by the lubricating oil film decreasing, but it is still noticeable and not negligible.关键词：Mixed lubrication;Rough peak;Lubricant film thickness;Local temperature rise
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发布时间：2022-09-24 - 摘要：In order to accurately diagnose gear faults, a gear fault diagnosis method based on local characteristic scale decomposition (LCD) and mathematical morphological filtering is proposed, which aims at the non-linear, non-stationary and low signal-to-noise ratio characteristics of vibration signals of early gear faults. Firstly, some Intrinsic Scale Components (ISCs) are obtained by local characteristic scale decomposition of gear vibration signals. Then, according to kurtosis criterion, the ISC with the largest kurtosis is selected as the fault characteristic component, and then filtered by morphological difference filter. Finally, the spectrum of the filtering results is obtained and the fault diagnosis is carried out. The feasibility and validity of the method are illustrated by analyzing the simulation results and experimental data. The results show that the method has the ability to suppress noise and extract fault shock characteristics, and can effectively realize the accurate diagnosis of gear fault.关键词：Local characteristic scale decomposition;Mathematical morphological filtering;Gear;Fault diagnosis
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发布时间：2022-09-24
Test·Analysis
- 摘要：As a kind of omnidirectional walking wheel, Mecanum wheel is widely used in many fields, to solve the limitation of Mecanum motion system on smooth road surface，a new variable cone angle Mecanum wheel which can be extended to the V type road surface is proposed. Each roller of the wheel is installed on the four-bar mechanism with spherical arrays and four-bar mechanism with circumferential arrays. The mechanism has a common input shaft to synchronously drive the corresponding Mecanum roller mounted on the connecting rod to realize the change of the roller axis offset angle, to achieve the change of the Mecanum wheel cone angle, to increase the adaptability of the Mecanum wheel motion system to the V type ground walking. By establishing the spherical four-bar mechanism kinematics model, the input and output equations of the spherical four-bar mechanism are solved. The common axis input rotation angle and the mapping relationship between the offset angles of the rollers are obtained. Finally, the slope of the road corresponding to the controllable cone angle of the Mecanum wheel, according to envelope principle, is approximated.关键词：Mecanum wheel;Spherical four-bar mechanism;Synchronous drive;Variable cone angle
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发布时间：2022-09-24 - 摘要：Based on a dual parallel four-bar mechanism and gear joint series-type traffic cone recovery manipulator, which has the problem of low recovery efficiency and difficult to achieve optimal motion trajectory of fixed gear ratio joints. The grooved cam joint is used for improving design. Firstly, based on the motion analysis of the manipulator, the minimum main arm angle is taken as the optimization target, the constraint condition is determined according to the traffic cone motion requirement, the motion trajectory optimization model is established, and the optimal motion trajectory of the manipulator is obtained. Then, according to the optimized motion trajectory, the theoretical contour of the grooved cam is solved by analytical method, and then the actual contour of the grooved cam is obtained. Finally, the simulation is verified by Adams. The results show that the main arm angle of the traffic cone recovery robot arm is reduced by 8.1%, the working stroke of the hydraulic cylinder is shortened, the force of the hydraulic cylinder is improved, and the working efficiency of the traffic cone recovery robot arm is improved.关键词：Traffic cone recycling manipulator;Kinematic analysis;Design of groove cam;Trajectory optimization
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发布时间：2022-09-24 - 摘要：For the problem of bending fatigue strength test of involute helical gear, the change regulations of bending stress and load distribution relation of helical gears with different tooth width and helical angle are researched by using RomaxDesigner. The contact line positions and the maximum stress are got, and it can be used to determine the loading position and load of helical gear in single tooth bending fatigue test. The simulation values of bending stress of different helical angle gears and the calculated values obtained by a series of correction coefficients in GB/T 3480—1997 are compared and analyzed. It is found that there is a big difference between them, which proves the necessity of bending fatigue test of helical gear. The test scheme of helical gear bending fatigue strength is raised. The results of helical gear bending fatigue test according to the method can be transformed into the national standard, which can be used in future to improve the accuracy of evaluating helical gear bending strength.关键词：Helical gear;Tooth root stress;Bending fatigue strength test
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发布时间：2022-09-24 - 摘要：According to the requirement of projectile long-travel and heavy-load automatic loading, a chain rammer with compact structure and forced ramming is designed. Based on virtual prototype technology, the virtual prototype model of the chain rammer is built. Adding driving according to the driving motor output characteristic, the dynamics simulation of the work process of rammer is carried out and the stability of chain drive ramming is analyzed. The results of simulation show that the projectile is stable in the forced ramming travel, the projectile at the end of the ramming can overcome the heavy load and accurately pushed into the chamber at a certain speed, the values can meet the requirements of automatic loading, and it is proved that the design is rationality.关键词：Chain rammer;Forced ramming;Virtual prototype;Dynamics simulation
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发布时间：2022-09-24 - 摘要：By establishing the mathematical model of helicopter transmission system running time and flight time, engine working time, the time ratio relation between running time and flight time is deduced, that is, conversion coefficient. Using Minitab software to complete the data calculation, the running time of the transmission system is converted into the corresponding flight time. Compared with the traditional way which only considers the flight time in the air, the real and accurate time between overhaul can be obtained and the reliability can be improved. At the same time, the maintenance time scale of the transmission system and other parts of the helicopter can be ensured. This method is successfully applied to a certain type of helicopter, and some reference for the maintenance of similar aviation products can be provided.关键词：Running time;Time between overhaul;Calculation method
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发布时间：2022-09-24 - 摘要：To realize the higher performance design of involute rotor, based on four possible top structure, from seven aspects of profiles parameterization, the limit value of shape coefficient, volume utilization coefficient, size optimization and so on, the higher performance profiles with wide top for high-sealing zone is finally constructed. Then, from lightweight of rotor as design object, the optimization model is constructed. Finally, an innovative configuration of profiles is given to eliminate trapped-gas phenomenon. All results show that the innovative profiles is meet high performance requirement for maximizing volume utilization coefficient and minimizing radial top leakage. The trapping-gas phenomenon is eliminated better by the new avoid-arc, which is easy machined. The shape coefficient or volume utilization and top half angle have approximately negative linear correlation, etc. It is concluded that the full parametric modeling and design method can be used for other rotor profiles with radial high-sealing zone.关键词：Roots pump;Wide top high-sealing zone;Involute rotor;Profile optimization;Volume utilization coefficient;Composed profile
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发布时间：2022-09-24
Development·Application
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