最新刊期
期 1 ， 2022
- 摘要：The dynamic behaviors of the hydrostatic slide is changed instantaneously and abruptly during the start-stop, acceleration and deceleration, so magnetorheological（MR） damper is used to suppress tangential vibration of hydrostatic slide. A single-degree-of-freedom vibration model is established, and the dynamic response of the system are studied by the incremental harmonic balance method（IHBM） with arc length as control increment. The simulation results show that it is feasible to suppress the vibration of hydrostatic slide using MR damper. The amplitude-frequency curve changes from hardening type nonlinearity to softening type nonlinearity with the increase of the current of damper slowly, and may lead to hysteresis region narrowing, disappear and secondary jump. With the variation of the frequency ratio, the relationship between amplitude and current of damper is changed significantly. When the frequency ratio is small, the amplitude decreases monotonously with the increase of current. The curve is complex and the jump phenomenon occurs with the large frequency ratio. Finally, the experimental results show that the MR damper can suppress the vibration of hydrostatic slide effectively.关键词：Machine hydrostatic slide;MR damper;Machine vibration;Vibration suppression;IHB
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发布时间：2022-09-22 - 摘要：Multi-scale fuzzy entropy can well measure the complexity of the vibration signal, but it lacks the effective use of other channel information. To make full use of the vibration information of other channels, the multivariate sample entropy theory that characterizes the multivariate complexity of synchronized multi-channel data is applied to the bearing fault diagnosis. To accurately extract fault features of bearing signals, a bearing multi-fault diagnosis method based on complete ensemble empirical mode decomposition with adaptive noise（CEEMDAN） and refined composite generalized multivariate multiscale fuzzy entropy（RCGmvMFE） is proposed. First, CEEMDAN is used to decompose multi-channel raw signals to obtain IMF without mode mixing. Then the correlation analysis method is used to screen the IMF components, and the IMF sensitive to the fault characteristics is selected as the multi-channel data to constitute the multivariate variable, and the RCGmvMFE is calculated to constitute the fault feature. Then, t-distributed stochastic neighbor embedding（t-SNE） is used to reduce the dimensionality of high-dimensional features. Finally, the whale optimization algorithm（WOA）is used to optimize the kernel extreme learning machine（WOA-KELM） so as to classify the low-dimensional fault features. Experimental results show that this method can effectively diagnose different fault severity of bearings, and provides a supplementary method for fault diagnosis of rolling bearings.关键词：CEEMDAN;RCGmvMFE;Sensitive IMF;t-distributed stochastic neighbor embedding;Manifold learning;Rolling bearings;Fault diagnosis
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发布时间：2022-09-22 - 摘要：In order to obtain the optimal vibration response of a seven-axle elevated platform vehicle with hydro-pneumatic suspension（HPS）, a hybrid coupling scheme of parallel connection ＆ contralateral cross-linked for HPS was designed. The dynamic model with 20 degrees of freedom which can comprehensively reflect vehicle coupling vibration including vertical-lateral-longitudinal-transverse was established. The vibration response characteristics of the vehicle and the influence of key parameters were analyzed by joint simulation. A single objective function contains two evaluation indices of vehicle ride comfort and stability was established through analytic hierarchy process（AHP） and range transformation standardization. The parameters optimization calculation of HPS was carried out. The model reference adaptive control, based on the principle of global vibration, applying Lyapunov design adaptive law, was carried on the HPS. The simulation results show that the evaluation index of vehicle vibration response is significantly improved after parameter optimization and superposition adaptive control.关键词：Seven-axle hybrid HPS;Dynamic model;Ride comfort and stability;Parameters optimization;Adaptive control
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发布时间：2022-09-22 - 摘要：The non-linear motion characteristics of the large-scale floating wind turbine have been significantly enhanced. For this reason, the DTU 10 MW wind turbine was used as the research object, and the NAUTILUS semi-submersible platform floating wind turbine model was established, and the tuned mass damper（TMD） was installed in the nacelle Optimize TMD parameters through multi-island genetic algorithm, study the motion response characteristics of floating wind turbines without TMD control, TMD control（unoptimized） and optimized TMD control, and based on chaos theory, adopt phase space reconstruction and maximum Lyapunov exponent method from qualitative and quantitative analysis of the nonlinear characteristics of floating wind turbine motion response. The results show that under TMD control and optimized TMD control, the forward to after displacement response of the floating wind turbine tower top is significantly reduced, but the side to side displacement response is relatively small; the peak forward to after acceleration response of the tower is significantly reduced in the range of 30 m～90 m. The peak value of side to side acceleration response decreases in the range of 10 m～30 m. Compared with the non-TMD control, under the optimized TMD control, the chaotic characteristics of the floating wind turbine’s motion response are weakened, and the maximum Lyapunov exponents are all reduced, indicating that the optimized TMD can reduce the nonlinear characteristics of its motion response.关键词：Super large;Floating wind turbine;Tuned mass damper;Multi-island genetic algorithm;Dynamic response;Chaotic characteristics
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发布时间：2022-09-22 - 摘要：In order to accurately diagnose the fault of submersible sewage pump, an improved Hopfield neural network（HNN） fault diagnosis method was proposed. BP neural network was used for coding operation to overcome the coding defects of HNN neural network. The connection weights of HNN neural network were optimized by particle swarm optimization（PSO） algorithm to improve the global convergence ability of the improved neural network, and the improved HNN neural network model was obtained. Based on the field experiments, the vibration signal feature vector of the submersible sewage pump under fault operation was obtained. Then the feature vector was used as sample data to train the improved neural network, and the fault types of the submersible sewage pump were diagnosed. The results show that the improved HNN neural network has better global convergence ability, and the typical fault diagnostic accuracy of the submersible sewage pump is more than 90%, which can realize the accurate diagnosis of the fault during the operation of the submersible sewage pump.关键词：Submersible sewage pump;Improved Hopfield neural network;PSO algorithm;Fault diagnosis;Vibration signal
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发布时间：2022-09-22 - 摘要：Some characteristics of bearing initial signals are considered including unobvious features, susceptibility to noise interference and strong nonlinearity when a bearing was damaged. Based on the fractal box dimension, an improved variational mode decomposition for nonlinear features extraction of bearing fault signals（IVMD-NFE） is proposed. Because of the multi-measurement of nonlinear signals, the multifractal detrended fluctuation analysis（MF-DFA） method is used to study the multifractal characteristics of each fault signal. Taking the experimental data of rolling bearing as the research object, IVMD-NFE and MF-DFA method were used to analyze and diagnose the initial bearing signal. The results show that the signal extracted by the IVMD-NFE method can filter out noise to a greater extent and has lower fractal box dimension, and the extracted nonlinear characteristics are more representative; The fault signals of bearing exhibit multi-fractal features, the outer ring fault has the largest singularity index and strongest nonlinearity, and the cage fault is the smallest and weakest nonlinearity, indicating that the complexity of the data can better reflect the running state of the bearing. However, the method of using VMD or directly processing the original signal fails to extract effective nonlinear features, resulting in failure to distinguish faults.关键词：Variational mode decomposition;Fractal;Bearing;Nonlinear;Fault diagnosis
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发布时间：2022-09-22 - 摘要：In mechanical systems, the gap between mechanical components causes nonlinear elastic collisions during their movement. Taking the two-degree of freedom vibro-impact system with gap as the research object, the mathematical model was established and the numerical simulation analysis was carried out in Matlab software. Based on this, the application of function generators, resistors, capacitors, operational amplifiers and oscilloscopes and other analog electronic components in Multisim software to establish the equivalent circuit model for simulation analysis. The results show that the simulation results of equivalent circuit are consistent with those of numerical simulation analysis.The difference is that the equivalent circuit simulation not only has faster and more efficient operation, but also can realize dynamic parameter adjustment and conversion analysis under different modes. The Equivalent circuit simulation provides a reference method for the dynamics research of nonlinear vibration system.关键词：Nonlinear vibration;Numerical simulation;Equivalent circuit simulation;Dynamics
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发布时间：2022-09-22 - 摘要：The surface topography of parts serves as a crucial role for machining quality. In order to achieve accurately prediction of the surface topography of precision milling, a surface topography simulation method based on wavelet packet analysis and frequency spectrum analysis of cutting vibration is proposed in this paper. In the paper, firstly, the ball-end milling is taken as the research object and the motion trace model of cutting edge changing with time based on the workpiece coordinate system is established. And then the vibration equation obtained by wavelet packet analysis and spectrum analysis is put into the model. Finally, the surface topography of the part is simulated and predicted by employing MATLAB. The comparisons between simulation and trial experiments suggest that the accuracy of the surface topography simulation prediction model based on wavelet packet analysis and frequency spectrum analysis of vibration signal offers a reference for the actual processing and production.关键词：Ball-end milling;Cutting vibration;Wavelet packet analysis;Modeling and simulation;Surface topography
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发布时间：2022-09-22 - 摘要：In order to investigate the impact resistance of the 2A12 aluminum alloy plate, blunt-nosed projectiles were launched with the impact velocity ranging from 120 m/s to 330 m/s to hit aluminum alloy target plates with a thickness of 6 mm, and the influence of the initial impact speed on the impact resistance of targets was analyzed. The ballistic limit and velocity curve of projectiles were obtained by fitting the data of the experiment. The results show that the energy absorption of the target first decreases sharply and then keeps stable with the increase of the initial velocity of the projectile. Meanwhile, the target plate mainly undergoes shear failure, and the structural deformation of the target plate decreases as the velocity of the projectile increases. Moreover, based on the ABAQUS/Explicit finite element software, the modified J-C constitutive relation and fracture criterion were used to calculate the projectile impact target model. And the failure mechanisms of targets were analyzed on the base of verifying the validity of the simulation model.It has been found that the failure mechanisms of targets are similar under different impact speeds, and the initial velocity of the projectile has little effect on the failure mechanism of target.关键词：Aluminum alloy target;Blunt-nosed projectile;Shear failure;Failure mechanism;Target deformation
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发布时间：2022-09-22 - 摘要：In order to study the dynamic mechanical properties of SUS304 stainless steel commonly used in rail vehicles, tensile tests under wide strain rates of 0.000 2 s-1～500 s-1 were carried out respectively. The test results show that SUS304 stainless steel exhibits strain hardening during dynamic stretching. As the strain rate increases, the material exhibits a strain rate strengthening effect. At the same time, a certain thermal softening effect is produced. To accurately describe the dynamic mechanical properties of the material, the Johnson-Cook model of the material at room temperature was first established. On this basis, adiabatic temperature rise is introduced, and a modified Johnson-Cook model considering plastic strain and strain rate correlation is established. The modified Johnson-Cook model can better describe the dynamic mechanical characteristics of SUS304 stainless steel, which is the characteristic that the stress gradually weakens with the increase of strain and strain rate. This modified model provides a basic basis for the crashworthiness analysis of the rail vehicle body structure.关键词：SUS304 stainless steel;Dynamic constitutive;Johnson-Cook model;Strain rate
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发布时间：2022-09-22 - 摘要：Foil hydrodynamic air bearing is a kind of self-acting hydrodynamic gas bearing which the foil is used for elastic support. Because of its superior dynamic performance, it is widely used in high-speed turbine machinery, high-precision machine tools, aviation, aerospace, national defense and other high-end equipment fields. The foil hydrodynamic air bearing uses the air as the lubricating medium, according to the principle of dynamic pressure lubrication, a certain relative velocity should be reached between the journal and the bearing, so that the dynamic pressure film formed can overcome the radial force of the rotor and make the journal and bearing separate from the mechanical contact, that is, the rotational speed should reach the takeoff velocity of the foil hydrodynamic air bearing. In order to reduce the mechanical contact time between journal and bearing, determine the acceleration time of the motor and accurately measure its takeoff velocity, which has important engineering significance. A method to determine the takeoff speed of foil hydrodynamic air bearing by evaluating the vibration characteristics is proposed.The analysed result shows that accords with the actual result, which verifies the accuracy of the theoretical calculation method and is of great significance to the engineering application of air bearing.关键词：Air bearing;Foil;Takeoff velocity;Vibration test
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发布时间：2022-09-22 - 摘要：Aiming at the dynamic mechanical system with multiple failure correlation, the copula function is used to describe the correlation of failure modes among units, and a reliability model of dynamic mechanical system with multiple failure correlations is proposed. The reliability problem of complex system is transformed into multiple two-dimensional pair copula functions by using R-Vine copula function. The optimal R-Vine structure is selected by using MST algorithm. The time-varying parameters in the model are described by nonparametric kernel density estimation（KDE）. The common series parallel system（hybrid system） in mechanical system is modeled and analyzed. Finally, the effectiveness of the model is verified by an example of spacecraft open and close shafting.关键词：R-Vine Copula function;Series-parallel system;Nonparametric kernel density estimation（KDE）;Reliability
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发布时间：2022-09-22 - 摘要：In order to improve the working reliability of the biomimetic robotic fish, put forward a gradient reliability robust optimization design method method which is applied to the biomimetic robotic fish.Taken the bionic killer whale as the research object, based on the flapping wing motion theory, the dynamic load of the bionic killer whale was obtained by using MATLAB.Based on the theory of reliability sensitivity design, robust design theory and the theory of performance degradation, established optimization evaluation function of bionic killer whale, obtained the influence of the bionic killer whale’s design variables to reliability sensitivity gradient.The improved quantum evolutionary algorithm was used to optimize the design, the optimal solution of caudal fin propulsion mechanism was obtained.The results show that the absolute value of sensitivity of the design variables is decreased, the reliability is improved and the structure is more robust. This paper combine the flapping wing movement theory, the reliability sensitivity design theory, the reliability-based robust design theory, the theory of performance degradation and improved quantum evolutionary algorithm were combined, put forward a gradient reliability robust optimization design method method which is applied to the biomimetic robotic fish, it provides theoretical method and data support for the reliability analysis and design of bionic robot fish.关键词：Bionic robotic fish;Numerical simulation;Reliability;Sensitivity;Quantum evolutionary algorithm
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发布时间：2022-09-22 - 摘要：With the development of structural topology optimization methods, some scholars had proposed strategies to integrate existing topology optimization methods to improve the manufacturability of topology optimization result. Specifically, a topology optimization method combined the Solid Isotropic Material Penalty（SIMP） method and the Moving Morphable Components（MMC） method was proposed. Firstly, the characteristics of power function in SIMP method was used to quickly obtain the main path of force transfer. Secondly, according to the gray-scale elements generated by the SIMP method, an Otsu threshold algorithm was proposed to maximize response of the binary topological structure. On this basis, morphological thought was used to construct a component, whose boundary was the inflection point of the skeleton, then the MMC method was used to complete the optimization to finally achieve the precise control of structure size. By calculating the minimum compliance topology optimization problem of the 2 D and 3 D numerical examples, the optimization results of smooth boundary and precise size of structure are obtained, verifying the effectiveness of proposed method.关键词：Otsu threshold algorithm;Morphological idea;SIMP（Solid Isotropic Material Penalty）;MMC（Moving Morphable Components）;Minimum compliance
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发布时间：2022-09-22 - 摘要：Aiming at the life data information of multiple types of testing sources for the same product, a mixed base distribution constructed to achieve three-source data fusion, and at the same time, the overall distribution density function of the life data source was estimated. And the iterative formula of the maximum likelihood estimation of each unknown parameter in the parameter vectors of the mixed basis distribution density function was obtained based on the EM algorithm. At the same time, the estimated value of each parameter was given by using the sample weighted by Bootstrap method, the density function analysis of the mixed basis distribution was determined, and the product reliability analysis was completed. The calculation example verified the feasibility and effectiveness of this type of model.关键词：Mixed basis;Maximum likelihood estimation;EM algorithm;Data fusion;Bootstrap method
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发布时间：2022-09-22 - 摘要：Aiming at the driving comfort problem of a sporty large-displacement motorcycle, an optimization scheme was proposed. Through the simulation analysis of the motorcycle on the C-level road, the pitch vibration and vertical vibration acceleration, which characterize the riding comfort of the motorcycle, were obtained, and the above two index peaks were used as the target response. Sensitivity analysis and approximate modeling of related parameters were carried out, and the radial basis function neural network approximate model was used for multi-objective optimization, based on the error analysis of the approximate model. The results show that after optimization, the actual vehicle verified that the pitch vibration acceleration peak was reduced by 17.21%, and the front and rear wheel vertical vibration acceleration peaks were reduced by 8.11% and 24.18%, respectively, which improved the ride comfort of the motorcycle and verified the effectiveness of the optimization scheme.关键词：Class C road surface;Suspension system;Sensitivity analysis;Approximation model to basis function neural network;Multi-objective optimization
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发布时间：2022-09-22 - 摘要：In order to solve the reliability evaluation of small samples for the high reliability, long-life products and to improve the accuracy of reliability evaluation, the Bayesian reliability evaluation model of multiple information source data fusion was carried out. First, a set of data as the initial prior information of another information source in this model was selected, by using the posterior density according to Bayesian estimation. Then, it as the prior distribution of the next information source was used. Through iteration, the joint posterior density and reliability index data of multi-source heterogeneous data are obtained, and the corresponding reliability analysis is completed. Finally, a simulation example verifies the rationality and effectiveness of the model.关键词：Data;Information fusion;Bayesian estimation;Reliability assessment
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发布时间：2022-09-22 - 摘要：A Bayesian model updating and damage identification method based on Markov chain sampling was proposed for damage identification of stochastics structures. Firstly, an objective function based on the measured frequency and mode shapes was established, and then the Markov chain Monte Carlo method with delayed rejection was used for stochastics sampling, and the posterior probabilities of structural parameters in intact and damage states were obtained. By comparing the probability density functions of the identified parameters in the two states, the probability and degree of structural damage were finally obtained. The experimental example of steel cantilever beam indicated that based on the modified stochastics parameters, the damage probability and damage degree of each region of the structure are consistent with the real situation.关键词：Model updating;Damage identification;Bayesian method;Stochastics structure
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发布时间：2022-09-22 - 摘要：Automobile seat crossbeams play an important role in ensuring the living space of passengers in a collision accident. The reasonable filling design may effectively improve the safety performance of automobiles. Based on the characteristics of high specific energy and light weight of aluminum foam, three different kinds of composite structure composed of foamed aluminum and thin-walled steel pipe were designed and filled into automobile seat crossbeams. The bending and compressive properties of the filled seat crossbeams under three-point bending and axial compression were studied by finite element simulation, and then the best filling scheme was optimized. The results show that the bending and axial bearing capacity of the filled seat crossbeam are improved by 193.6% and 241.4% respectively compared with the original one, and the effectiveness of filled seat crossbeams to improve the crashworthiness of vehicle is proved by the side impact simulation.关键词：Seat crossbeam;Aluminum foam;Composite structure;Finite element simulation;Filling design
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发布时间：2022-09-22 - 摘要：Stiffened plates is a common structural form in aviation structure. Different types of stiffened plates and different manufacturing processes will affect its mechanical behavior and failure mode. The finite element method is used to establish numerical models of titanium alloy stiffened plates, and to study the effects of the T, L and Z type stiffened plates on buckling mode and failure. The influence of manufacturing processes such as welded, spot welded, riveted and integral panels on buckling and post buckling properties are analyzed. It is shown that the buckling load and the failure load of the T-type stiffened plate are the maximum one. Different manufacturing processes have great influence on the failure load and post-buckling load capacity, among which the post-buckling load capacity of welded stiffened plate is the largest one. At the same time, the most effective stiffening method of 600 mm×600 mm stiffened plate structure is given.关键词：Stiffened plates;Finite element method;Axial compression load;Buckling;Post-buckling
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发布时间：2022-09-22 - 摘要：In order to study the transportation efficiency of the aggregate device of coal cleaning machine, taking a certain type of coal cleaning machine as the research object, establishing the mechanical model of interaction between particles and blades, obtaining the relationship between force and speed.Based on the Archard wear theory and discrete element method, Coupling model of screw and coal was established by EDEM.Analyzing the transportation capacity of screw by controlling variable, the influence of coal particle size and rotating speed on the wear depth of screw was studied.The results show that increasing the rotating speed can improve the coal transportation efficiency in terms of speed control, but too fast speed will cause particles to fly out along the radial direction.The wear depth of the screw decreases first and then increases with speed changing in from 20 r/min to 65 r/min.When speed is increased from 35 r/min to 50 r/min, the efficiency improvement effect is the most significant.,the torque of screw is relatively small at the same time.In conclusion, the best range of screw speed is 35 r/min～ 50 r/min.In addition, the screw wear is serious when transporting large coal particles compared with small particles.Therefore, in practical application, the transportation of large coal should be carried out at low screw speed.Based on the above conclusion, in this paper, an optimal mathematical model is established to minimize the driving torque, obtaining the optimal structure and dynamic parameters of the screw, and proving the correctness of optimization process by simulation test.It provides a theoretical reference for improving the transportation efficiency of the coal cleaning machine, reducing the energy consumption of the equipment and prolonging the service life of the equipment.关键词：Conveying screw;Conveying characteristics;Wear;Optimization
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发布时间：2022-09-22 - 摘要：The load of ball cage type constant velocity joint of military off-road vehicle is larger than that of traditional vehicle, and the working condition is bad, which may cause contact wear, as well as the fracture of the cage under the angle between large axes. Therefore, it is very important to study the contact stress and the strength of the cage under the bad working condition. In this paper, a typical military off-road vehicle ball cage constant velocity joint is taken as the object. Firstly, the contact stress between the steel ball and the inside and outside raceway is theoretically analyzed and simulated. The simulation and analytical results are compared to verify the correctness of the simulation model. Secondly, according to the load transfer relationship between the key parts of the universal joint and the physical experiment, the reason and process of cage fracture are analyzed. Finally, the static torsion test under the ultimate axial angle is carried out, and the hardness test is carried out on the section of the cage. The strength distribution along the thickness is obtained through the relationship between hardness and strength conversion. The results show that the strength of the cage meets the requirements under normal working conditions, but may be broken under bad working conditions. This research can provide theoretical reference for the design and manufacture of constant velocity joint for off-road vehicle.关键词：Universal joint;Cage;Contact analysis;Stress analysis;Strength
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发布时间：2022-09-22 - 摘要：In order to obtain the stiffness-damping feature of cross-arm damping seat of special vehicles, the dynamic simulation model of cross-arm seat is established. The time-frequency responses on the level D road and different vehicle speed conditions（5 km/h, 15 km/h, 25 km/h and 35 km/h） are analyzed. With considering the weighted root-mean square（RMS） acceleration in criterion ISO 2631-1:1997 as an evaluation index, the ride comfort of the seat with different matching relationships of stiffness and damp are discussed. Furthermore, the real vehicle validation experiment is conducted. The results show that the seat vertical acceleration under different speeds has the non-stationary random characteristic. The seat vibration intensifies with the increase of the speed. Under different vehicle speed conditions, the first two model frequencies for the seat concentrates in 3 Hz～10 Hz, which includes the human sensitivity frequency ranges, inducing the poor ride comfort performance. Additionally, the simulation results agree with the experimental data, which verifies the correctness of the dynamic simulation model. The research has certain reference for multi-objective matching optimization design about the stiffness-damping parameters for the seat comfort of special all-terrain vehicles and engineering applications.关键词：Special vehicle;Seat;Ride comfort;Stiffness-damping;Matching
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发布时间：2022-09-22 - 摘要：In order to study the influence of different operating modes on the dynamic response and stability of offshore wind turbines under turbulent wind and earthquake, DTU 10 MW offshore single-pile wind turbine was used as the research object. The p-y curve was used to describe the interaction between the pile foundation and the subsea soil. Based on the finite element software ANSYS, the finite element model of the wind turbine was established and the structure modal, dynamics and buckling calculation of the wind turbine were carried out. The results show that the vibration mode of the tower is dominated by torsional and bending vibration. Its first natural frequency is within the ideal design range and the rotation of the wind wheel will not cause its resonance. Turbulent wind has the most significant influence on the displacement of tower top and earthquake has much greater influence on the lateral displacement of tower top than the turbulent wind. After the earthquake, the equivalent stress and strain energy response of the tower have surged. The emergency shut-down can effectively reduce the peak of the tower top displacement, the tower equivalent stress and the tower strain energy response and reduce the risk of structural damage and plastic deformation. Under the action of turbulent wind and earthquake, lateral buckling failure will occur in the middle and upper part of the leeward surface of the tower. The emergency shut-down can effectively improve its buckling resistance and the maximum increase of critical buckling load is nearly 27.11%.关键词：Wind turbine;Finite element;Earthquake;Dynamic response;Buckling
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发布时间：2022-09-22 - 摘要：Combined with the actual structure and working conditions of the synchronizer, AMESim, MATLAB and ABAQUS software are used to establish the gear shifting dynamics model, friction contact mechanism model and finite element analysis model of the synchronizer. The thermal structure coupling method is used to simulate the temperature characteristics of synchronizer during synchronization. Based on the mechanical result of the synchronizer and the friction contact mechanism and thermal analysis theory of the synchronizer, the thermal characteristics of the frictional contact area during the synchronization phase of the synchronizer are modeled, simulated and analyzed. The results show that the maximum temperature of the model is in the middle of the whole friction area, the maximum temperature of the friction surface of the synchronous lock ring is 106.0℃, and the maximum temperature of the friction cone surface of the meshing ring is 78.3℃.The analysis of the temperature field of the synchronizer lays a foundation for the subsequent analysis of the thermal failure form and mechanism of the friction contact surface.关键词：Synchronizer;Frictional contact;Thermal structure coupling;Temperature characteristic
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发布时间：2022-09-22 - 摘要：By combining the thermal elastohydrodynamic lubrication theory, thermoelastic mechanics theory and principle of heat-pressure conversion, a method was presented to solve the material thermal expansion coefficient of solid surface in the thermal elastohydrodynamic lubrication of line contact. It could solve the thermal elastic deformation of solid surface caused by non-uniform temperature field under constraint of oil film pressure. Numerical results satisfying the convergence conditions were obtained by an example, and the influence of load, entrainment speed and solid material on the material thermal expansion coefficient were further studied. When the two solids are the same metal material, the results show that the thermal expansion coefficient of the solid surface with large radius is relatively large at each point in the computational domain; when the load increases, the material thermal expansion coefficient of the solid surface at each point becomes larger; when the entrainment speed increases, the thermal expansion coefficient will decrease; when the density of solid increases, the material thermal expansion coefficient decreases.关键词：Line contact;Thermal elastohydrodynamic lubrication;Thermal expansion coefficient;Thermal elastic deformation;Heat-pressure conversion
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发布时间：2022-09-22 - 摘要：Creep behavior of P91 steel was studied by using a constitutive model based on deformation mechanism. Combined with the experimental data, it was found that the minimum creep rate has an obvious exponential relationship with the applied stress during creep, which was closely related to different deformation mechanisms. By introducing dislocation slip, dislocation climb and grain boundary slip into the traditional Norton power law equation, the creep behavior of P91 steel under the conditions of 580℃～620℃ and 135 MPa～200 MPa stress was simulated and analyzed. The results show that the creep curve of P91 steel can be well described by using this model, including the initial stage, steady stage and acceleration stage of creep. In addition, the results of model calculation and SEM analysis further show that the creep fracture form of P91 steel is transgranular fracture within the current temperature stress range.关键词：Deformation mechanism;True stress;Creep behavior;Fractography
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发布时间：2022-09-22 - 摘要：The calculation models of frequency domain fatigue analysis method are various and their accuracy is different. In order to solve the above problems, based on the time domain analysis results of the half axle, the accuracy comparison of frequency domain fatigue analysis methods is carried out. Firstly, the load signals of the half axle under different working conditions are obtained, and the stationarity, Gaussianity and bandwidth were investigated to obtain the basic properties of the load signal. Secondly, the static analysis of the half axle was carried out, and the transfer coefficients of stress and torque at the dangerous node of the walking half axle were obtained. Meanwhile, the stress time histories of the dangerous node of the half axle under various working conditions were obtained. Based on the above stress time histories, the comparative study of fatigue life in time-frequency domain was carried out, in which the average stress and non-Gaussian correction model were introduced to modify the traditional frequency domain method. The results showed that the accuracy of the modified frequency domain method was significantly better than that of the traditional frequency domain method. In the modified frequency domain method, TB2ms+nG and DKms+nG had the highest accuracy. When the above two methods were applied to the stationary load signals, the reliability was high. Nevertheless, when they were applied to the non-stationary load signals, the reliability was low.关键词：Combine half axle;Time domain fatigue analysis;Frequency domain fatigue analysis;Stationarity;Gaussianity
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发布时间：2022-09-22 - 摘要：In view of the fatigue failure of the transmission shaft in advance, the study of the stress state and life is carried out. Through the analysis of the actual measured load, the cause of the fatigue failure of the drive shaft in advance is the inconsistent output load of the left and right splines. The finite element model of the transmission shaft is established by using finite element software, and the maximum stress at the root of the right tooth of the transmission shaft is obtained, which is the weak part of the transmission shaft. The response surface method and genetic algorithm are used to optimize the structural parameters of the transmission shaft（tooth root fillet, spline transition arc, and arc groove depth）. After optimization, the stress of the weak part of the transmission shaft tooth root is reduced by 28.3%. The fatigue life of the transmission shaft is increased by five times, and the reliability is higher. Finally, the fatigue test is carried out on the scaled down sample. The test result shows that the life of the drive shaft is doubled. The effectiveness of the optimization method is verified through experiments, and the method has certain reference significance for the optimization of shaft parts in the future.关键词：Transmission shaft;Load;Response surface;Life optimization
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发布时间：2022-09-22 - 摘要：Taking two different structures of bogie frame as the research object, the multi-axis stress method was used to evaluate the side beam fillet weld fatigue according to DVS1612. The establishment means of the weld local coordinate system and the calculation method of material utilization are described in detail. It can be seen from the fatigue assessment results that the base plate fillet weld fatigue strength mainly depends on the normal stress parallel to weld; the vertical plate fillet weld fatigue strength is comprehensively affected by the stress in three directions, and the multi-axis effect is transparent. The material utilization of the vertical plate fillet weld is higher than the base plate, so the fatigue failure of side beam fillet weld first occurs at the vertical plate. The weld fatigue strength assessment relative dangerous areas of different frame structures are roughly identical, which verifies the accuracy and stability of the fatigue assessment method in this paper. This method provides a reference for the weld fatigue assessment of other equipment.关键词：Welded frame;Weld fatigue evaluation;Multi-axis stress;Material utilization;DVS1612
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发布时间：2022-09-22 - 摘要：The multi-specimen method and the normalization method and the elastic unloading compliance method were used to test the high-temperature fracture toughness of 630℃ on new rotor steel FW2. The multi-specimen method and the normalization method have obtained valid high-temperature fracture toughness test results. Comparison of the test results shows that the J-R resistance curve obtained by normalization method is within the ± 99.7% confidence interval of the fitting curve of the multi-sample method. The fracture toughness characteristic value J0.2 BL obtained by normalization method is lower than the characteristic value J0.2 BLobtained by the multi-specimen method and is located at the lower limit of the confidence interval of the multi-specimen method, which verifies the validity of the normalization method. Elastic unloading compliance method is not suitable for the high-temperature fracture toughness test for the stress field at the crack tip of FW2 steel does not conform to the elastic-plastic fracture mechanical characteristics at elevated temperature.关键词：High temperature fracture toughness;New rotor steel;Multi-specimen method;Normalization method;Elastic unloading compliance method
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发布时间：2022-09-22 - 摘要：Aiming at the problems of screen blinding, low screening efficiency and unstable screening performance of traditional vibrating screen in agricultural field, a three degree of freedom adjustable vibrating screen was designed, including leveling device, two degree of freedom excitation system, single degree of freedom excitation system, controller and level monitor.The two degree of freedom excitation system provides reciprocating movement along the x-axis and rotation around the y-axis for the screen disk, while the single degree of freedom excitation system provides reciprocating movement along the y-axis for the screen disk, and the two are connected in series to form a three degree of freedom excitation device.The kinematics simulation of the vibrating screen was carried out by using ADAMS software to verify that the vibrating screen can vibrate with 1～3 degrees of freedom; Based on the discrete element method, the screening process of rice particles on the adjustable three degree of freedom vibrating screen plate was simulated and analyzed, and the experiment was carried out on the prototype.The results show that the screening efficiency of three degree of freedom vibration is 8.8% and 33.4% higher than that of two degree of freedom and single degree of freedom vibration respectively, which solves the problems of less degree of freedom, low screening efficiency and unstable screening performance of traditional vibrating screen.关键词：Multi degree of freedom;Vibration sieve;Structural design;Simulation analysis;Experimental verification
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发布时间：2022-09-22 - 摘要：Experiment and simulation method are adopted to analyze the bolts fracture of the power take-off box of a certain type of dry-mixed mortar transport truck. The power take-off box gets power from the gear box and sends it to the air compressor through transport shaft, the materials are transported to the storehouse through the air pressure. The torque of transport shaft is measured at different rotation velocity. Results show that the torque value is high value and high aptitude at low rotation velocity. The analysis results of the fatigue life of bolts at the toque of different rotation velocity indicated the lower the current speed, the shorter the fatigue life of the power take-off bolt. It is concluded that air compressor working at low speed is the reason for the bolts fracture problem. The problem of the power take-off box bolt was solved by keeping the speed of air compressor at 950 r/min through the constant speed cruise function of the dry hybrid vehicle.关键词：Power take-off box;Bolt;Fatigue;Finite element simulation
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发布时间：2022-09-22 - 摘要：Aiming at the problems of single movement dimension of traditional vibrating screen, low screening efficiency, short life of key parts, etc. Using the randomness of chaotic vibration and the characteristics of reciprocating non-periodic motion, chaotic vibration is applied to the vibrating screen to improve the screening efficiency. A new type of chaotic vibrating screen with one redundant degree of freedom is developed, the dynamic model of the new chaotic vibrating screen is established, the vibration differential equation of the vibrating screen is obtained by the Lagrange method, and its dynamic characteristic diagram is obtained through simulink simulation analysis. Chaotic identification is performed on the time-frequency diagram, phase diagram, Poincare map and Lyapunov exponent diagram obtained from the simulation results. The simulation shows that the Poincre map of the chaotic vibrating screen is scattered and the maximum Lyapunov exponent is positive. The motion output of the new chaotic vibrating screen is chaos Vibration, the research results of the thesis can provide a theoretical basis for the design and application of chaotic vibrating screens.关键词：Chaotic vibration;Vibrating screen;Simulink;Lagrange;Nonlinear system
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发布时间：2022-09-22
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