最新刊期
期 4 ， 2021
- 摘要：In order to explore the influence of the changes of electromagnetic parameters and mechanical parameters on the dynamic characteristics of servo drive system,based on the relevant theories of mechanical dynamics and electromagnetism,builded a four-inertia electromechanical coupling model including motor electromagnetic stiffness and electromagnetic damping.Obtained the time history curve,phase plane diagram,Poincare mapping and amplitude-frequency characteristic curve of the system by using 4～5 order Runge-Kutta method with variable step size. Analyzed effects of the changes of electromagnetic stiffness,excitation frequency and transmission comprehensive error on the motion state of the electromechanical coupling system.Under different electromagnetic stiffness values,the system will change from period doubling bifurcation to period 1 motion,and then to chaotic motion,and when the electromagnetic stiffness decreases from 5 × 10~5 Nm/rad to 10~5 Nm/rad,the maximum amplitude of the system will increase by 7%. The change of mechanical parameters such as gear meshing error will change the motion state of the system,and when the fluctuation coefficient of comprehensive transmission error increases from 0. 05 to 0. 2,the amplitude of the system will increase by 16%.关键词：Servo system;Electromechanical coupling;Electromagnetic stiffness;Nonlinear dynamics;Powertrain
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发布时间：2022-09-22 - 摘要：Adjusting the value of nonlinear system parameters will affect the output Signal-to-Noise Ratio（ SNR）,so Signalto-Noise Ratio（ SNR） was used as the output evaluation index of stochastic resonance. A method combining Multipoint Optimal Minimum Entroy Deconvolution Adjusted（ MOMEDA） with Cuckoo search adaptive Stochastic Resonance（ SR） was proposed to extract weak fault feature frequencies.Simulation analysis shows that using MOMEDA as the stochastic resonance pretreatment can significantly improve the weak fault signal,and experimental example verification further shows that the combination of MOMEDA method and stochastic resonance can effectively extract the characteristic frequency of weak fault signal from the signal with strong noise,so as to realize the weak fault diagnosis of rolling bearings.关键词：Rolling bearing;Multipoint optimal minimum entroy deconvolution adjusted;Weak fault;Cuckoo search algorithm;Stochastic resonance
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发布时间：2022-09-22 - 摘要：In the era of big data,bearing fault monitoring has the problem that it cannot realize the real-time processing of massive data processing and have the subjectivity about fault feature selection. In order to solve the above problems,a new bearing fault diagnosis method combining Compressed Sensing（ CS） and Multilayer Extreme Learning Machine（ ML-ELM） is proposed. This method first uses compressed sensing theory to obtain a small amount of data that can express characteristic information from a large amount of bearing monitoring data. Then multilayer extreme learning machine which improved by PSO use the measured value to obtain the classification information of bearing failure. This method greatly reduces the amount of data for bearing diagnostic signals and eliminate the step of feature selection in intelligent diagnosis. It makes full use of multilayer extreme learning machines to extract the characteristic information of bearing signals from a small number of observations.Experimental analysis show that this method can accurately identify faults at different positions and different damage levels,and provides a new method for bearing condition monitoring and fault diagnosis.关键词：Compressed sensing;Multilayer extreme learning machine;Bearing;Fault diagnosis
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发布时间：2022-09-22 - 摘要：In order to solve the problem of poor accuracy and low efficiency of traditional rolling bearing life prediction method. A prediction method based on bi-directional stack simple recurrent unit is proposed. Multiple time and frequency features are extracted from the original signal to construct a multi-dimensional data set to enhance the information representation and avoid the insufficient reflection of a single feature on the bearing degradation ability. Relying on the ability of recurrent neural network to process time series data,the SRU model is constructed,the traditional RNN serial operation structure is reconstructed,and the training efficiency is improved. On the basis of single layer SRU,it is stacked in reverse,so that the model can learn two-way information in time dimension,improve the accuracy of prediction. The experimental results show that the prediction accuracy and training efficiency of this method are improved.关键词：Rolling bearing;Simple recurrent unit;Reverse stacking;Two-way information;Life prediction
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发布时间：2022-09-22 - 摘要：Aiming at the problem that it is difficult to extract subtle fault features in the process of rolling bearing fault identification,this paper proposes a rolling bearing fault diagnosis method based on fusion convolutional neural network and support vector machine based on particle swarm optimization algorithm. In this method,the bearing vibration signal is used as the input signal of the one-dimensional convolutional neural network and the two-dimensional convolutional neural network,and the extracted fault information is fused in the convergence layer. Finally,the optimized classifier improves the accuracy of fault recognition. In order to verify the diagnostic performance of this method,a comparison will be made between the 1 D convolutional neural network and the 2 D convolutional neural network with the same specifications of the fusion convolutional neural network.Experimental results show that this method can not only improve the accuracy of fault identification,but also maintain good diagnostic performance when the signal is polluted by noise.关键词：Rolling bearing;Fault diagnosis;Convolutional neural network;SVM
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发布时间：2022-09-22 - 摘要：Based on the bearing dynamics and rotor dynamics models,the dynamic characteristics of aero-engine rolling bearing-dual rotor spindle system are studied. According to Timoshenko beam-axis theory,the finite element discretization model of rolling bearing-dual rotor spindle system is established and the numerical method is used to solve the problem. The results shows that:（ 1） Due to the influence of nonlinear characteristics of the system,the system responds to multiples and combined frequencies of the excitation frequency under multi-frequency coupling excitation,the system vibration response is extremely complex.（ 2） The change of the radial clearance of the intermediate roller bearing has a certain influence on the system response,the effect on the response of the supporting bearing is small,and the small clearance can reduce the response displacement of the center of the intermediate bearing and the rotor system,so that the system tends to be stable.（ 3） Properly increasing the number of supporting bearing rolling elements reduces the response of the supporting bearing and rotor center,and the system stability also increases.（ 4） The general trend of the simulation curve is the same as the experimental data but not fully in agreement,and the result has some errors（ the error is about 15. 6%）. The analytic results will provide a referenced gist for the dynamic stability of dual-rotor-rolling-bearing by the quantitative and qualitative analysis.关键词：Rolling bearing-dual rotor spindle system;Dynamic;The finite element method
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发布时间：2022-09-22 - 摘要：The empirical correlation method of small punch test is the main method to obtain the mechanical properties of macroscopic materials. However,owing to the empirical correlation method is limited by the test device of small punch test and the size of specimen,there is no unified and recognized empirical correlation formula so far. In order to obtain the semi-analytical solution formula by using the small punch test,a new strip-type specimen of small punch test based on the energy equivalence principle and the finite element analysis method were adopted to obtain 4 coefficients of the Chen-Cai semi-analytical equation. A new method of estimating the uniaxial constitutive relationship of metal material by small punch test of strip-type specimen was proposed. The uniaxial constitutive relationship of Q345 R steel and 904 stainless steel estimated by the new method is in good agreement with the true stress-strain curve obtained by uniaxial tensile test.关键词：Small punch test;Strip-type specimen;Energy equivalence principle;Uniaxial constitutive relationship
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发布时间：2022-09-22 - 摘要：In order to investigate the material properties of the welded structure in the airship and the effect of the welded structure on the membrane strength,the test specimens and schemes were designed for uniaxial tensile test,uniaxial cyclic test,and biaxial tensile test according to the airship engineering experience and structural stress distribution. The method of digital image correlation was adopted in the experiment. The test results show that the strength of welded structure is more than membrane and the fracture location is the membrane where the two materials meet. The strength of membrane with welded structure is smaller than the membrane itself,which is reduced by about 12% under uniaxial tensile condition and reduced by about 36% under biaxial tensile condition with ratio 2 ∶1. This paper can provide experimental support for the strength prediction of the airship structure.关键词：Welded structure;Membrane;Airship;Strength test;Digital image correlation
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发布时间：2022-09-22 - 摘要：It is of great theoretical significance and engineering value to carry out fatigue damage detection and evaluation of aluminum alloy for application of automobile lightweight materials. In this paper,the periodic fatigue damage characteristics of 6061-T6 aluminum alloy were studied based on CT damage detection and defect reconstruction technology. Firstly,fatigue damage samples of 6061-T6 aluminum alloy at different stages are obtained by static tensile test and periodic fatigue test. Secondly,defect information of holes and cracks in the damaged samples are achieved through X-ray CT scanning,and 3D reconstruction of defect features is carried out by AVIZO visualization software,and continuity features of the damage defects in different stages are studied. Finally,the change characteristics of damage evolution parameters,including porosity,damage volume fraction,are analyzed according to damage degree of fatigue damage samples in different stages. Based on the analysis of change of damage characterization parameters with the number of cycles,the damage volume fraction,as a damage parameter,determines the proportion of damage,and has a direct impact on the size of damage,which can better reflect the continuous change of damage,so as to conduct a reasonable and effective analysis of defect evolution process.关键词：6061-T6 aluminum alloy;Periodic fatigue damage;CT scanning;AVIZO;3D defect reconstruction
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发布时间：2022-09-22 - 摘要：The load carriage is an important part of the conventional rail endless rope driven transport system aiming at the safety accidents such as derailment,descent and rollover caused by the vibration of the carriage in the process of transporting people or goods. In this paper,the vibration of the load carriage of the standard wheeling device and the clamp wheeling device are tested under three conditions: straight lanes,horizontal turning radius of 9 m,and vertical turning radius of 15 m. The analysis of the vibration performance of different gear trains under a variety of operating speeds shows that the clamp wheeling device has the best stability. With the increase of speed,when the running speed is more than 2. 0 m/s,the lateral amplitude of the standard wheeling device is larger; when the running speed is more than 1. 5 m/s,the longitudinal amplitude and the lateral amplitude of the standard wheeling device are larger than that of the clamp rail gear train,It is recommended to add the guard rail device; the running speed should not exceed 1. 8 m/s during vertical turning operation.关键词：Conventional rail endless rope driven transport system;Load carriage;Vibration;Wheeling device;Amplitude
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发布时间：2022-09-22 - 摘要：On the basis of verifying the effectiveness of the simulation method,frontal collision models of the trolley with three different forms of multi-lattice crash box were established. Through 100% forward collision simulation,the energy absorption effect,crushing performance and peak crushing force of different types of crash box were analyzed. The orthogonal experiment was completed with full factor experimental design method,and the nine-lattice energy absorption box was determined as a follow-up research object,explore the effect of wall thickness on the crashworthiness of crash box,A neural network model was used to construct the proxy model,and the multi-objective optimization design was completed using the NSGA-II genetic algorithm. For the optimized nine-lattice energy absorption box,The energy absorption was increased,the peak crushing force was reduced and the lightweight is achieved.关键词：Frontal crash;Energy absorbing box;Multi-objective optimization;Approximate model
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发布时间：2022-09-22 - 摘要：In the reliability assessment of products,this paper tried to make full use of a small amount of field data under natural storage, which might break through the restriction of using single pseudo-sample data in accelerated tests. The comprehensive reliability evaluation model,fusing exponential and Weibull natural storage field data and accelerated storage sample data,was built based on the integrating of relative entropy and the least square method. Simulation results indicate that the method can fuse two sources of information effectively,and when the amount of field data is small,the assessment of model is robust.关键词：Relative entropy;Least squares method;Accelerated test with double stresses;Information fusion
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发布时间：2022-09-22 - 摘要：In order to improve the energy utilization rate of the vertical axis variable angle of attack turbine,a mathematical optimization model of the blade declination angle variation rule was established,using the blade declination angle change with the position angle as the design parameter,the turbine energy utilization rate as the objective function,and genetic algorithm Combined with the method of sequential quadratic programming,the optimization calculation is carried out,and on this basis,the most suitable blade declination variation law is obtained. The deflection angle of the cycloid turbine at different speed ratios is optimized to obtain the optimized declination law. The results show that the energy utilization rate of the hydroturbine is better than that of the original cycloid turbine under the declination law optimized by the hybrid genetic algorithm. The ratio has improved.关键词：Vertical axis turbine;Deflection optimization;Sequence quadratic program（SQP）;Genetic algorithm
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发布时间：2022-09-22 - 摘要：In order to provide the basis for selecting suitable design formula of pressure equipment strength,and to establish the reliability method of pressure equipment strength design,the ratio of the flat winding vessel burst pressure actual value to the formula calculated value was considered as a random variable. applied mathematical statistics and probability theory,the validity and homogeneity of random variables statistical samples were discussed,the random variables distribution law was analyzed,the comparison method of random variables distribution parameters was constructed. The evaluation index and method of formulas engineering adaptability were established from two aspects of precision and stability. Taking 15 sets of flat winding simulation vessel burst pressure measured data and 5 sets of flat winding industrial scale vessel burst pressure measured data as examples,the distribution laws and parameters of the random variables corresponding to four burst pressure calculation formulas were analyzed and compared,the engineering adaptability of the corresponding formula was evaluated. The researching results show that:（ 1） When the confidence of both sides was 99%,4 formulas corresponding random variables statistical samples are effective and homogeneous; if the significance was 0. 05,the 3 random variables are basically accorded with normal distribution,when the confidence of both sides was 98%,the value interval of distribution parameters are obtained.（ 2） Of the three random variables that basically fit the normal distribution,there is no significant difference in the distribution parameters of two random variables,but there is significant difference with the distribution parameters of the other one.关键词：Design formula;Engineering adaptability;Flat winding vessel
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发布时间：2022-09-22 - 摘要：A flexible auxiliary support device based on magnetorheological fluid is designed to improve the machining accuracy of weakly rigid parts. Use the finite element method to simulate the device’ s magnetic induction intensity through COMSOL software,study the support force provided by it,use engineering mechanics knowledge to perform mechanical analysis on the processed workpiece,theoretical deformation calculation and finite element processing deformation simulation on the processed workpiece,the research is different The influence of the auxiliary supporting device of the magnetorheological fluid on the deformation of the processed workpiece under the state of loading current. Finally,build a test stand,perform milling experiments under the conditions of different milling parameters and magnetorheological auxiliary support devices loading different currents and measure the surface roughness and flatness of the processed workpiece, study the milling parameters and magnetorheological auxiliary support on the workpiece processing surface The impact of quality. The results show that the MRF auxiliary support device can increase the rigidity of weakly rigid workpieces,suppress machining deformation,and improve the machining quality of workpieces.关键词：Magnetorheological fluid;Finite element;Three-dimensional magnetic field simulation;Deformation amount;Milling test;Machining accuracy
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发布时间：2022-09-22 - 摘要：The movable tooth in the double shock sleeve movable tooth transmission structure is an indispensable part,which is easy to fail. The contact stress analysis of the movable tooth is of great significance to improve the bearing capacity and service life of the mechanism. The contact surface pressure and subsurface stress field distribution of movable teeth are solved by numerical method. The results show that the contact stress will appear singularity and stress concentration,which seriously affect the transmission performance of the transmission mechanism. In this paper,the logarithmic generatrix modification method and genetic optimization algorithm are used to optimize the structure of sleeve movable teeth. The results show that this method can effectively improve the contact stress singularity and stress concentration of movable teeth. The research results can provide theoretical guidance for the structural design and optimization of double shock sleeve movable tooth transmission and line contact parts.关键词：Double shock wave;Sleeve movable tooth transmission;Surface contact pressure distribution;Subsurface stress field;Optimization
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发布时间：2022-09-22 - 摘要：The world is short of energy,tidal current energy has been a hot topic in many countries because of its superiority. In this paper,a new type of impeller was designed to solve the problem that the current tidal current turbine couldn’t catch energy in both directions. The basic airfoil NACA24112 was calculated by the airfoil analysis software Xfoil and simulation software Fluent and used to design a new “S”airfoil,The chord length and twist angle of each blade section were calculated according to Wilson method,finally used CATIA for 3 d modeling and Fluent for simulating the model. A bidirectional fairing was designed to improve power generation,and its best flaring angle was 26° by Fluent simulation analysis. Through the flume experiment,the results show the impeller has good bidirectional characteristic and has low start velocity thanks to the effect of fairing,and can reach the maximum generation efficiency about 25. 4% at 2 m/s.关键词：Blade design;Fairing;Fluent simulation;Flume experiment
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发布时间：2022-09-22 - 摘要：The vigorous development of offshore wind energy and dense routes have increased the probability of collision between ships and wind turbines. Based on the nonlinear dynamics theory,the conceptual design of the foam aluminum sandwich structure protection device is proposed. To verify the advantages and disadvantages of the proposed design protection performance,LS-DYNA is used to simulate the collision process of a 3000 t ship and a 5 MW tripod offshore wind turbine. At different ship speeds,the anti-collision performance of the sandwich protection device with the same thickness and different layers was analyzed. The results show that with the same thickness,the 5-layer protective structure has a significant effect on improving the safety of offshore wind turbines,and effectively suppress the dynamic response of the wind turbine tower top. Furthermore the 5-layer anti-collision performance is better than the 3-layer and 4-layer structures. The ship speed is 0. 5 m/s,1 m/s and 2 m/s,the initial kinetic energy absorption ratio of the protective device is 76. 9%,79. 7% and 78. 5%,respectively. In addition,the 5-layer structure has the highest energy absorption ratio. With the increase of ship speed,the damage of the tower is aggravated,and the increase of the absorbed energy is less than that of the initial energy. Under the three speeds,the maximum displacement of the tower top is 80. 8 mm,169. 7 mm,and 375. 5 mm,respectively. The displacement response of the tower top is consistent with the change trend of the ship’s kinetic energy. With the increase of initial kinetic energy,the maximum crashworthiness of the protective device shows a growth trend. The crashworthiness growth rate is smaller than the initial kinetic energy growth rate,and the crashworthiness decreases with the increase in the number of layers of aluminum foam sandwich.关键词：Protective devices;Offshore wind turbine;Aluminum foam sandwich;Crash worthiness
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发布时间：2022-09-22 - 摘要：Based on the meshing theory of single roller enveloping end face worm drive,the distribution of contact line and the length of contact line on the cylindrical surface of the drive pair,and the self-rotation angle of the roller,and the self-rotation angle velocity of the roller are analyzed. The concepts of contact line wrap angle and contact line density are proposed to describe the spatial complexity of single contact line on roller cylinder and the density of contact wire on roller cylinder. Meanwhile,the calculation formulas of contact wire wrap angle and contact wire density are derived and analyzed numerically. The calculation formula of contact line on cylindrical surface of roller in specific space distribution area is deduced and its value is calculated. The average self-rotation angle velocity of roller in height direction is deduced and its value calculated by using numerical integration function of Matlab mathematical tool software. And the angle of roller in meshing period is obtained with the help of numerical integration function of Matlab. The sliding speeds under the condition of whether the roller is fixed or not are analyzed by comparing their values. The results show that the distribution area of contact line of the roller cylinder is very small in the specific space,the roller has excellent rotation performance,and the transmission pair has excellent anti sliding effect.关键词：Face worm;Wrap angle;Density of contact line;Average rotation angle;Numerical integration;Sliding speed
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发布时间：2022-09-22 - 摘要：According to the structure characteristics and motion principle of traditional machine tools,the spiral bevel gear is virtual machined by Catia. By comparing the machining accuracy with the theoretical model,the rationality and accuracy of the modeling are proved. Hypermesh is used to mesh the gears,which is imported into ABAQUS for finite element analysis to extract the curve of transmission error and contact wire with the increase of load,the amplitude of transmission error fluctuation decreases,but the amplitude of deviation from zero line increases. It shows that the transmission of spiral bevel gear is more stable and the transmission accuracy decreases with the increase of load,which is consistent with the dynamic characteristics of spiral bevel gear,indicating that the performance of virtual machining gear is good. When the contact performance and transmission error curve of the gear formed by virtual machining are not ideal in the finite element analysis,according to the principle of modification, the machining parameters can be adjusted and gear is reprocessed in Catia. The contact and transmission performance of the reconstructed gear can be improved in the analysis. In Catia simulation machining,the error can be added artificially to provide a model for the finite element analysis of the gear with error,which is convenient for people to study the dynamic characteristics of the gear with error. In the gear design stage,the finite element method is used to study the contact performance and transmission characteristics of the gear,so as to predict and evaluate the quality of the virtual machining gear,analyze the relationship between the gear performance and the adjustment parameters of the machine tool,and play an important role in the reverse adjustment of the processing adjustment parameters of the spiral bevel gear.关键词：Spiral bevel gear;Virtual machining;CAE;Transmission Error;Gear accuracy
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发布时间：2022-09-22 - 摘要：As an important performance parameter of metal materials,the elastic modulus changes with temperature.However,in the analysis of thermal elastohydrodynamic lubrication,the elastic modulus has been taken as a constant,and there must be an error in the calculation results. Taking the infinitely long line contact roller pair as the research object,the relationship between the change of solid elastic modulus and temperature was introduced into the theory of thermal elastohydrodynamic lubrication, combined with the theory of thermoelastic mechanics and the principle of heat-pressure conversion,a numerical calculation method considering the effect of random roughness was presented. The calculation of the elastic modulus field was added to the calculation,and the convergence accuracy of the elastic modulus field was set. The calculation was carried out through an example,and the influence of the load change was analyzed before and after considering the change of elastic modulus. The research content can provide a theoretical basis for the analysis of elastohydrodynamic lubrication and material properties.关键词：Elastic modulus;Line contact;Thermal elastohydrodynamic lubrication;Thermal elastic deformation;Roller pairs
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发布时间：2022-09-22 - 摘要：In view of the creep failure of the thermal recovery wellhead under the conditions of steam flood and steam stimulation,the creep test of 30CrMo at 390℃ and four different stresses was carried out. The test results were fitted and the parameters of the combined time hardening model were obtained.It is verified by short-term experiments that the error between the calculated value of the combined time hardening model and the test value is less than 15%.Using ANSYS Workbench,the creep failure process of the main pressure parts of the thermal recovery wellhead under constant temperature and load condition and intermittent load condition are simulated,and the failure time of the main pressure parts under two conditions is obtained,which is of great significance to the service life evaluation of the thermal recovery wellhead.关键词：Thermal recovery wellhead;Creep failure;30CrMo;Constant temperature and load;Intermittent load
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发布时间：2022-09-22 - 摘要：In view of the temperature field generated during the working process of the twin-screw compressor,the rotor produces thermal deformation and thermal stress,which is likely to cause fatigue damage to the rotor. Therefore,it is of great significance to analyze the stress fatigue of the screw rotor under the action of temperature load. Based on the finite volume method to numerically simulate the temperature field of the compressor in the working process,the GGI（ General Grid Interface）interpolation technology was used to transfer the temperature load to the rotor structure grid,and a thermo-solid unidirectional coupling simulation method based on loose coupling was established. The accuracy of the method was verified by using " L-shaped large diameter buried pipeline ". By solving the static balance equation of the rotor structure,the deformation and stress distribution of the rotor under the action of temperature load were studied. Finally,the fatigue life of the rotor was analyzed through the revised stress fatigue S-N curve. The research results show that the maximum deformation of the screw rotor occurs at the end where the male rotor is connected to the motor. The tooth tip of the female rotor and the tooth root of the male rotor produce a large stress concentration,and with the increase of temperature,the service life of the screw rotor Gradually decreases.This method can provide reference for compressor design research and optimization upgrade.关键词：Compressor;Temperature field;GGI;Static equilibrium equation;Fatigue life
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发布时间：2022-09-22 - 摘要：Automobile rear axle is the core load-bearing part of automobile chassis,its main damage form is fatigue failure under alternating load. It is of great significance to quantitatively evaluate the fatigue sensitivity of rear axle to realize the lightweight design of automobile and to improve the effective service life and safety of automobile. Firstly,the three-dimensional finite element model of automobile rear axle was established, and the maximum vertical force was selected for strength calculation,and the stress and strain state of automobile rear axle was obtained. On this basis,the fatigue life and damage distribution of the rear bridge are calculated based on n Code Design-Life,and the sensitivity of various parameters to the fatigue life is analyzed by response surface method. The results show that the fatigue failure of the rear axle first appears at the half axle sleeve pipe,elastic modulus has the most obvious effect on fatigue,the thickness of leaf spring seat is next,and the influence of bridge shell thickness,poisson’s ratio and bridge envelope thickness decreased successively.关键词：Automobile rear axle;nCode design-life;Fatigue life;Response surface methodology;Sensitivity
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发布时间：2022-09-22 - 摘要：To explore the influence of virtual road surface method,virtual iteration method and fixed body method on the damage of lower control arm,the data from the test site was used. The accuracy of vehicle multi-body dynamics model was verified by suspension K＆C test and vehicle controllability and stability test. The six-component force signal of wheel center simulation value was compared with test value in the time domain and the frequency domain. The analysis results show the accuracy of 3 D virtual road and tire model; Comparison of simulation value of three methods and test value of the vertical acceleration of the wheel center shows virtual iteration method has the highest precision,and fixed body method has the worst precision. From the perspective of fatigue simulation,the results show that virtual iteration method and virtual road surface method have the same damage distribution to lower control arm. Fixed body method is quite different from the two,and is more conservative. The simulation results of lower control arm under the three load methods meet the durability of the test field.,which was consistent with the test results of indoor bench.关键词：Multi-body dynamics;3D virtual road surface;Virtual iteration method;Fatigue damage
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发布时间：2022-09-22 - 摘要：Fatigue scatter factor is the reliability index of aircraft structure life,which is used to describe the reliability of analysis and test results. When average spectrum is used for durability analysis,the scatter factor is generally set as 4,corresponding to 99. 9% reliability. In the case of using severe spectrum,the scatter factor is between 2 and 4,but the specific value is not clear in aircraft strength specification. By referring to a larger number of relevant research and according to the results of scatter study on component-level fatigue tests,the fatigue scatter factor of aircraft structures under severe spectrum was clarified,which lays a foundation for the application of durability severe spectrum in fatigue design and full-scale test of military aircraft.关键词：Fatigue scatter factor;Severe load spectrum;Reliability;Fatigue life;Full-scale fatigue test（FSFT）
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发布时间：2022-09-22 - 摘要：In order to solve the problem that the accuracy of shrouded blade frequency calculation was reduced due to integrated treatment of shroud working face,the vibration characteristics of shrouded turbine blades were studied.In this paper,a modeling method of shrouded turbine blade considering deformation and actual contact area of shroud working face was proposed.The blade disk modeling and modal analysis were completed by using the above method,and the dynamic stress test was carried out to verify that the first order resonance frequency of the blade calculated by the model is basically consistent with the measured resonance frequency,and the difference between the two is less than 7%. The research work can provide a reference for the vibration design of aero-engine shrouded turbine blade.关键词：Aero-engine;Shrouded turbine blade;Vibration characteristics;Dynamic stress test
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发布时间：2022-09-22 - 摘要：Because the traditional method is not easy to test the motion characteristics of angular contact ball bearings under high-speed operation,a multi-body dynamic finite element model of balls,cages and rings was established based on ABAQUS.Taking 7005 type angular contact ball bearings as the research object,the variation of the linear velocity of the ball and the sliding rate of the cage under different axial load,radial load and rotation speed were studied. The study found that when the axial load increases,the amplitude of the linear velocity fluctuation of the ball gradually decreases,and the sliding rate of the cage gradually decreases. With the radial load increases,the fluctuation of the ball linear velocity amplitude gradually increases,and the sliding rate of the cage increases. When the rotation speed increases,the fluctuation of the ball linear velocity amplitude gradually increases,and the sliding rate of the cage also gradually increases. The finite element simulation results are compared with the theoretical values to verify that the finite element calculation results are closer to the actual working conditions.关键词：Angular contact ball bearings;Dynamics;Sliding rate;Cage;Rolling body
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发布时间：2022-09-22 - 摘要：Up to 81. 5 d B high noise occurs in the range hood fitted with original process impeller. This paper presents a method of combing experiment and numerical simulation to reduce the noise level of the range hood under the maximum working condition.First,noise and vibration test of range hood and excitation resource are conducted on a range hood fitted with impellers made by original approach and new process,respectively. Then,the differences between the processing technologies in making the two impellers are analyzed. Modal analysis of the above impellers are performed to determine the cause of the vibration noise. Results show that the thermal stress is generated in the production process,which changes the natural frequency of the impeller made by the original process.Moreover,the changed natural frequency is close to the excitation frequency,which leads to the severe vibration noise. However,less thermal stress is produced in the production process of the new impeller by adding one more step in the production. The final modified procedure is to increase the natural frequency of the impeller by thickening the impeller rear lap and use the original production process. Thus the problems caused by severe vibration noise of the impeller gets solved successfully.关键词：Range hood impeller;Vibration noise;Modal;Optimization analysis
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发布时间：2022-09-22 - 摘要：In order to analyze and predict the fatigue life of the shearer’s cutting planet carrier,the shearer’s rigid-flexible coupling model was established,the planet carrier’s dynamic characteristics was studied,and the planet carrier’s maximum stress value was obtained as the input. The planet carrier’s fatigue life was obtained by using n Soft,and the planet carrier’s fatigue life,under different working conditions was predicted by using BP,PSO-BP and improved PSO-BP. The results show that under the condition of solidity coefficient of 8. 4,depth of cut-off 600 mm,rotational speed of 90 r/min and traction speed of 2. 5 m/min,the maximum stress is 554. 78 MPa,the planet carrier’s stress concentration area is at the spline receding groove,and the fatigue life is 5. 507 2×106. Among the three neural network models,BP,PSO-BP and the improved PSO-BP,the predicted fatigue life’s maximum relative error is 4. 35%,2. 52% and 0. 90%,and the iteration ’s number is 23,8 and 6 times,respectively. The improved PSO-BPNN model improves the prediction accuracy and also improves the iterative speed. Combining MATLAB、ANSYS、ADAMS、n Soft and improved PSO-BPNN,this paper provides a method for predicting the fatigue life of key parts of industrial and mining equipment.关键词：Shearer;Planet carrier;Fatigue life;Adaptive variation;Particle swarm optimization algorithm;BP neural network
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发布时间：2022-09-22 - 摘要：The three-point bending pressure straightening method is employed to deal with the problem of single curvature bent stepped pipe. Based on the theory of elastoplastic mechanics the analysis of deformation process for the stepped pipe with bilinear strengthening elastoplastic material is performed,in which the effect of stress concentration at the changed cross-section place is considered. Therefore,the calculation formula of straightness stroke is deduced. The correction of the mathematical model is verified by the straightening process simulation based FEM analysis of explicit dynamics in Workbench LS-Dyna software and the corresponding experiment. The simulation and experiment results show that stepped pipe rectified by the proposed method has high straightness,meaning a good straightening affect.关键词：Stepped pipe;Stress concentration;Straightening stroke;FME simulation
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发布时间：2022-09-22 - 摘要：In the long-term work of industrial robot cables,the mechanical properties will be insufficient due to aging,which will affect the normal operation of the robot. In this paper,the thermal aging test was carried out to accelerate the aging of CPE rubber at the same temperature,and the tensile test was carried out to select the tensile strength at break and the elongation at break. The mechanical properties of CPE rubber after aging were studied. The results show that with the increase in aging time,the tensile strength and elongation of CPE break with the aging time,showing a trend of decreasing first and then rising. And the tendency towards the elongation at break is a delay from the tensile strength of the fracture. The slope of the elastic phase of the CPE tensile curve is greatly affected by the aging time,while the strengthening phase is less affected by it. And the slope of the elastic stage decreases rapidly in the early stage of heating,and it picks up later. This can provide some basis for further research to improve cable performance and prolong its service life.关键词：CPE;Cable;Jacket material;Heat aging
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发布时间：2022-09-22 - 摘要：The tower is the main bearing component of wind turbine,and its performance directly affects the service life and safety of wind turbine. The 2 MW wind turbine tower structure optimization was researched,with the tower quality was taken as the optimization objective,the natural frequency,stress and height was taken as the constraint conditions,and the diameter,wall thickness,pitch length was taken as control variables. The tower structure was optimized by simulation and checked by analytical solution. The results show that the optimized tower has reduced weight 4. 21% and increased natural frequency,the maximum stress position obtained by simulation is the same but 22. 3% larger than the analytical,the analytical first order natural frequency is 18% larger than the simulation. This optimization method has certain practicability and engineering application value,and is suitable for popularization and application.关键词：Wind turbine;Tower;Structural optimization;Simulation analysis;Analytical solution
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发布时间：2022-09-22 - 摘要：The load sharing characteristics of a planetary gear train is one of its main performance. Many researches at home and abroad have shown that the floating effect of components in a planetary gear train has an important influence on load sharing characteristics of the system. In this paper,the relationship between sun gear and spline on the input shaft is considered. Also,friction of inner and outer teeth in splined connection as well as constraint floating of sun gear are simulated. The nonlinear opposite supporting force of the spline on the input shaft to the sun gear is established. Taken a 5-planetary gear transmission system as an example,its load sharing coefficients with different radial clearance of a spline are calculated by the lumped-mass method. The research result provides a basis for load sharing design of planetary gear trains.关键词：Planetary gear train;Load sharing characteristics;Sun gear;Spline;Floating
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发布时间：2022-09-22 - 摘要：In order to meet the requirements of beating up technology on conjugate cam,a modified trapezoid acceleration law is used to construct motion equation of reed by segment. The reverse design program of conjugate cam is developed by MATLAB software,and precise reverse design of pitch curve on main and auxiliary cam are realized which on the basis of reconstructing law of beating-up motion. Besides,shape change of the pitch curve is analyzed by combining swing arm angle Φand center distance L. The results of reverse design show that pressure angle α at each point on the curve can meet requirements of mechanical transmission characteristics. The reasonable values of basic circle radius and roller are determined through calculating radial direction r0 and radius of curvature ρ0 of the curve point by point. The results provides a technical idea for reverse and design innovation of the conjugate cam on beating-up mechanism.关键词：Conjugate cam;Reverse design;Beating-up;Pitch curve;Pressure angle;MATLAB
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发布时间：2022-09-22 - 摘要：According to the burst fault of a fuel tank cover,the failure mode was determined to be fatigue fracture based on the fracture morphology and failure analysis. By contrasting the different of design drawing and using finite element analysis method,the fault mechanism was located through troubleshooting process. The fracture position of the cover was determined to be the maximum stress position. Insufficient thickness of the cover is the fundamental cause of the fatigue resistance. According to the design drawing,the thickness of the cover increased from 3 mm to 4 mm meet the use requirements under the condition that the total height of the cover remains unchanged. The results of the study were recognized by the customer and the improvement measures ensured the safety and reliability of the aircraft in service.关键词：Fuel tank cover;Fatigue failure;Mechanism analysis;Improvement measure
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发布时间：2022-09-22 - 摘要：The test of stress distribution and characteristics of pressure vessel is of great significance to ensure the safe and reliable operation of pressure vessel. For the rectangular vessels,the external stiffeners are used to improve their bearing capacity,so their stresses are more complex than that of cylindrical and spherical vessels. In this paper,a set of data acquisition system of stress test was self-developed for a rectangular vessel of desalination pilot plant by using the electrical resistance strain gauge method. All stress tests were carried out under the half-water and operation conditions,the Mises stress and its variation at different positions of the rectangular vessel was obtained. According to the measured strain data,the strength analysis was conducted. The results indicated that the Mises stress of the rectangular vessel under operation conditions is larger than that under the half-water condition in which the maximum Mises stress is 247. 09 MPa. The dangerous area of the rectangular vessel is mainly in the middle of the shell,and the stress on the edge of the shell is small. This study could provide an analysis method for a rectangular vessel of desalination pilot plant and the optimal design of rectangular vessels.关键词：Stress test;Rectangular vessel;Experimental research;Strength analysis
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发布时间：2022-09-22
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