最新刊期
期 1 ， 2023
- 摘要：To solve the problems of low computational efficiency and missing amplitude information existing in the current multiscale sample entropy（MSE） method when extracting features of complex series, refined improved multiscale fast sample entropy（RIMFSE） is presented. Firstly, fast sample entropy is employed to substitute traditional sample entropy, and the calculation cost is greatly reduced by improving the matching mechanism of reconstructed vectors. After that, the improved multiscale expansion method is applied to replace the traditional coarse-grained method, thereby avoiding the loss of amplitude information. Based on this, a new rotating machinery fault diagnosis method is proposed in combination with the max-relevance and min-redundancy（mRMR） method and the support vector machine（SVM） classifier. Two fault data sets of gearbox and bearing are used to verify the performance of the presented method; meanwhile, the presented method is compared with existing methods such as MSE, composite MSE（CMSE） and refined composite MSE（RCMSE）. The results show that compared with MSE, CMSE and RCMSE, the proposed method enjoys significant advantages in terms of robustness, calculation efficiency and recognition accuracy, thereby providing a new idea for rotating machinery fault diagnosis based on entropy feature.关键词：Refined improved multiscale fast sample entropy;Max-relevance and min-redundancy;Support vector machine classifier;Rotating machinery;Fault diagnosis
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发布时间：2023-07-28 - 摘要：Aiming at the problems of high vibration and low efficiency of TRT rotor, the dynamic characteristics of TRT rotor are studied. The geometric modeling of the rotor is carried out by using 3D software UG, and imported into Ansys Workbench to establish a finite element analysis model; the rotor dynamic characteristics-modal, critical speed and steady-state unbalanced response are calculated and analyzed. On this basis, the finite element model is used to analyze the influence of different supporting stiffness and supporting positions on the dynamic characteristics of the rotor, and tested on the high-speed rotor test room. Research shows, the difference between calculation and test results is within 3%; the finite element analysis results can truly reflect the dynamic characteristics of the rotor. Both support stiffness and support position have a significant impact on the first and second order critical speed of the rotor. In the unbalance response, the most sensitive position of the first order is the second stage blade position, and second order is the position of the head（coupling）. A reference for the calculation and analysis of the dynamic characteristics of other rotors of the same type is provided.关键词：Dynamic characteristics of rotor;Vibration;TRT;Modal analysis;Critical speed;Unbalanced response
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发布时间：2023-07-28 - 摘要：For the problems of system model inaccuracy, internal and external disturbances in active vibration control of an all-clamped plate structure, an active vibration control method based on an active disturbance rejection controller（ADRC） was introduced to suppress the structural vibration by using inertial actuators, and the effect of the bandwidth of the controller observer, the parameters of PD controller, the gain of controller on control performance were also studied. First, a state space model was established to model the all-clamped plate structure with the inertial actuator. Then, the three-order linear extended state observer was used to estimate the uncertainties and state variables for the whole vibration control system. Additionally, the influence of each parameter of ADRC on the vibration control was also theoretically analyzed to achieve the excellent vibration suppression performance. Finally, based on NI-PCIe 6343 acquisition card, a hardware-in-the-loop experiment platform was set up in the desktop real-time of Matlab/Simulink to verify the vibration performances of ADRC and the accuracy of the theoretical analysis. The results show that the ADRC algorithm is feasible for vibration control. When other parameters of the controller remain unchanged, in a certain range, increasing the bandwidth of the controller observer or decreasing the gain of controller can improve the control performance, but adjusting the parameters of PD controller have little effect on the control performance.关键词：Inertial actuator;All-clamped plates;Active vibration control;Active disturbance rejection control
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发布时间：2023-07-28 - 摘要：In order to extract the fault information of rolling bearing vibration signals under strong noise coverage and improve the accuracy of fault diagnosis and classification, based on the theory of fuzzy entropy（FE）, a new method of complete ensemble empirical mode decomposition with adaptive noise（CEEMDAN） and convolutional neural network（CNN） is proposed, which make full use of the independence, relative consistency, and the advantages of fuzzy entropy and randomness. The fuzzy entropy of the original signal was obtained by cyclic sampling, decomposed by CEEMDAN method, and the optimal component group was screened by Pearson correlation coefficient. Finally, the optimal component group was input to CNN for fault diagnosis, and the t-SNE popular learning algorithm was used for clustering visualization. The results show that compared with EMD-Fuzzy Entropy and EEMD-Fuzzy Entropy under different working conditions, the proposed method has stronger robustness and generalization, and t-SNE visualization makes the results more intuitive.关键词：Convolutional neural network;Bearing;CEEMDAN;Fuzzy entropy;Fault diagnosis
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发布时间：2023-07-28 - 摘要：The effects of structural parameters, material parameters and pre-compression of rubber on the static torsion stiffness of rubber spring were studied by means of experimental research and simulated analysis. Firstly, the Mooney-Rivlin model was used to fit the rubber constitutive parameters, and the finite element model of rubber spring was established. Then, the quasi-static torsion experiment of the rubber spring was carried out, which verified the accuracy of the finite element model. Finally, based on the established finite element model, the effects of rubber rod height, diameter, pre-compression and hardness on the static torsion stiffness of rubber spring were studied by orthogonal experimental method. The results show that the height, diameter, pre-compression and hardness of rubber rod are nonlinear with the static torsion stiffness of rubber spring, and the pre-compression of rubber rod has the most significant effect on the static torsion stiffness of rubber spring.关键词：Rubber spring;Mooney-Rivlin model;Static torsion stiffness;Finite element analysis;Orthogonal experiment
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发布时间：2023-07-28 - 摘要：Experimental tests and finite element simulation methods were used in this article. The bearing loads and deformation failure modes of laminated cellular cylindrical shell under axial compression loads were studied. Two kinds of cellular units, regular hexagon and re-entrant, were studied. The influence of different heights, diameters and thicknesses on the axial bearing loads were discussed with laminated cellular cylindrical shell. It is concluded that the axial compression performance of re-entrant cylindrical shell is better than regular hexagonal cylindrical shell. The buckling deformation modes of laminated cellular cylindrical shell under axial compression were analyzed. In addition, the material parameters obtained by the test were used to simulate the experimental results, compared the deformation modes and compression performance of simulation and experimental results.关键词：Laminated cylindrical shell;Cellular structure;Axial loading;Finite element simulation
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发布时间：2023-07-28 - 摘要：In order to effectively solve the chatter problem in cylindrical grinding and improve the product quality, a general dynamic model for cylindrical grinding was established based on the regenerative chatter theory. The overlapping factor related to the width of the grinding wheel was introduced into the general dynamic model to fully consider the regenerative chatter relationship between the workpiece and the grinding wheel, and it can be used in longitudinal grinding and circular cutting grinding. In this model, Newton iterative method was used to solve the transcendental equation with time delay, Gaussian elimination method was used to improve the iterative convergence speed, the continuation algorithm was used to continuously provide effective initial values to improve the accuracy of the iterative results, and the accurate grinding stability boundary was obtained. Finally, an experimental research on the grinding and processing of the plunge grinding micro-chatter was conducted. The experimental results show that the universal model can effectively describe the process of cylindrical plunge-cut grinding chatter, and effectively avoids grinding micro vibration lines phenomenon by the model selection of grinding parameters. The model can be effectively used in improving the quality and the efficiency.关键词：Grinindg chatter;General model;Continuation scheme;Stability
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发布时间：2023-07-28 - 摘要：Low carbon alloy steel 20CrNiMo is a kind of high strength surface hardening material which was commonly used as high-quality gears. After surface nitriding, carburizing or carbonitriding quenching treatment, it has good tooth surface hardness and tooth root toughness. According to the relevant national standards, a number of material test bars had been designed and carried out, the tensile strength and tensile fatigue strength date of material had been obtained. The lognormal distribution and two parameters Weibull distribution were used to fit and test the testing data, and the R-S-N curves of materials with the different confidence levels were obtained by calculating the probability distribution function. The fatigue life data of the material was more suitable for the lognormal distribution.关键词：20CrNiMo;Fatigue test;R-S-N curve;Data processing
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发布时间：2023-07-28 - 摘要：The osteoporosis model of mouse tibia was established based on castration, and the effect of osteoporosis on the mechanical properties of tibia was investigated. The two-dimensional sections of mouse tibia were obtained by Micro-CT. The three-dimensional digital model of mouse tibia was obtained by reconstruction technology, and trabecular bone shape and density were analyzed. The effect of osteoporosis on the mechanical properties of tibia was explored by testing and finite element simulation. The results showed that osteoporosis could damage the trabecular structure and decrease the mechanical properties of tibia. Compared with healthy tibia, the maximum load, bending stiffness and elastic modulus of tibia decreased by 20%, 30% and 25%, respectively, and the simulation results were in good agreement with the experiment. This study provides an important basis for the clinical diagnosis and treatment of osteoporosis.关键词：Mouse tibia;Osteoporosis;Mechanical properties;Finite element simulation
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发布时间：2023-07-28 - 摘要：The carbide bit YG10 green drilled nickel-base superalloy GH4169 through dry drilling, air cooling and LCO2 cooling to explore the drilling performance and wear mechanism of nickel-base superalloy, with the purpose of improving the bit life. According to the analysis of bit life, drilling force, drilling temperature, drill wear morphology and machined surface roughness under different cutting conditions, both air cooling and LCO2 cooling can improve cutting conditions, reduce drilling force and drilling temperature, and prolong bit life. Air cooling and LCO2 cooling can increase cutting life by 33% and 2.33 times, respectively. It has a high requirement on the working condition when the carbide bit drills nickel-base superalloy. The main failure mode is chipping or even broken edge in inappropriate working conditions, and the main failure mode is adhesive wear in appropriate working conditions.关键词：Cemented carbide;Nickel-base superalloy;Green cutting;Bit life;Adhesive wear
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发布时间：2023-07-28 - 摘要：Fatigue cracks of the welded structure often initiate at the weld toe. Under the complex metallurgical-physical process, the grain sizes and their distribution morphology at the weld toe site show obvious variation. In order to investigate the influence of grain distribution morphology on the fatigue behavior of the weld toe short cracks, metallographic tests were carried out for different areas of the weld toe for the cruciform joint specimen to obtain the average grain sizes of the coarse-grain region and the fine-grain region. Two-dimensional representative volume element（RVE） models considering grain distribution morphology were constructed. Based on FIP parameters and McDowell model, the nucleation and fatigue propagation behavior of the weld toe short cracks with different grain distribution morphology were simulated. The results showed that grain size and orientation are important factors influencing the nucleation behavior of the weld toe short cracks. The grain distribution morphology has little effect on the early behavior of short cracks, but the effect is gradually significant with the cracks propagating to a certain threshold length. In general, the fine-to-coarse grain transition mode can reduce the growth rate of short cracks.关键词：Grain distribution morphology;Short weld toe cracks;Crack nucleation;Crack fatigue propagation;RVE model
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发布时间：2023-07-28 - 摘要：A piston lattice structure design method based on reliability topology optimization is proposed for the lightweight design of internal combustion engine pistons, which is decomposed into two parts of reliability analysis and deterministic topology optimization to be solved separately. A mathematical model for the reliability topology optimization of the piston lattice structure was established considering the minimized mass as the objective function and the maximum stress as the constraint. The failure probability constraint was transformed into a reliability index constraint according to the first second-order moment method, and then the random variables were transformed into standard normal variables, and the random variables were corrected and designed for deterministic topology optimization according to the sensitivity information of the random variables relative to the performance index. Finally, a comparative study of deterministic lattice design and reliable lattice design was conducted with a certain type of engine piston as an example. The results show that compared with the deterministic design, the reliability piston lattice model has more reliable performance when considering the influence of random variables. And the mass of lattice model is reduced by 11.8% compared with the original piston model, which meets the design requirement of piston lightweighting.关键词：Internal combustion engine piston;Lattice structure;Topology optimization;Reliability analysis;Lightweight design
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发布时间：2023-07-28 - 摘要：Aiming at the lightweight design of the disc brake for small family cars, the finite element analysis and multi-objective optimization of the disc brake were carried out.Through the sensitivity analysis, the contribution degree of each size parameter of the brake disc to the braking performance and quality was established, and the optimization variables were quickly selected.Taking the lightest weight of the brake disc, the lowest surface temperature of the brake disc and the minimum maximum equivalent stress as the objective function, a multi-objective optimization mathematical model was established. NSGA-II hybrid variant algorithm based on the control elite strategy in Ansys was used to optimize the brake disc. After the optimization, the quality of the brake disc is reduced by 29.2% by simulation. The correctness of the simulation results is verified by the experiment under the same working condition, which realizes the lightweight of the brake disc and provides a reference for the design of the disc brake.关键词：Disc brake;Lightweight;Multi-objective optimization;Sensitivity analysis
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发布时间：2023-07-28 - 摘要：Excavators are the main construction machinery for earth and stone engine. Due to the uncertainties of the work object, load, and operation, the force of the working device of the excavators becomes more complicated. The working device is mainly composed of bucket, arm and boom. Based on different optimization parts, optimization objectives and optimization algorithms, the optimization design of excavators working device has diversity and complexity. An optimization method of working device of hydraulic excavator is introduced in detail, respectively from three aspects of local and overall optimization, new structure application of simulation and modern optimization algorithm. The optimization methods and future development trend of hydraulic excavator working device are summarized, which provides a reference for optimal design of hydraulic excavator working device.关键词：Hydraulic excavator;Working device;Optimization design;New structure;Modeling and simulation
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发布时间：2023-07-28 - 摘要：Inspired by the intrinsic degradation mechanism within the battery during fast charging, a stress-regulation（SR） fast charging method for lithium-ion battery is proposed by considering the diffusion-induced stress in the positive active particles. In the SR protocol, the diffusion-induced stress within the active particle reaches the critical value rapidly in the very early stage of the charging and maintains that value throughout the whole charging process. Furthermore, the constant-current stress-regulation（CCSR） protocol which contains an initial constant current stage and a following stress-regulated stage is proposed to resolve the issue of the theoretically infinite current at the beginning of the SR protocol. Compared with the constant current charging method, the boost charging method and the exponential current charging method, the proposed protocols provide an effective fast charging scheme for balancing the charging speed, the peak stress and the available capacity.关键词：Lithium-ion battery;Fast charging;Diffusion-induced stress;Capacity fading
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发布时间：2023-07-28 -
MECHANICAL PERFORMANCE OF NEGATIVE POISSON’S RATIO STRUCTURES BASED ON ROTATING CONCAVE HEXAGON (MT)
摘要：In order to improve the mechanical performance of the negative Poisson’s ratio structure, based on the deformation mechanism of rotating rigid body structure and concave polygon structure, conventional concave hexagon was rotated by a certain angle to obtain the negative Poisson’s ratio（NPR） structure of rotating concave hexagon. Firstly, the theoretical formulas of structural equivalent performance, such as relative density, equivalent elastic modulus, and equivalent Poisson’s ratio, were derived, and verified by simulation calculation. The finite element software LS-Dyna was used to simulate and analyze the dynamic characteristics of rotating concave hexagon and conventional concave hexagon under different impact velocities, and the relationship between energy absorption characteristics of rotating concave hexagon NPR structure and structural parameters such as cell wall thickness, rotation angle and included angle was discussed. The results show that the nominal stress-strain curves of the structure have multi-stage platform stress characteristics. Compared with conventional structure with the same mass, the new structure has longer platform stress section and better energy absorption performance. This study provides an idea for improving impact resistance of multicellular structures.关键词：Negative Poisson’s ratio;Mass ratio energy absorption;Energy absorption characteristics;Finite element simulation;Dynamic crushing- 5
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发布时间：2023-07-28 - 摘要：Using finite element simulation and experimental testing methods, with three stiffened rib configurations as the research object, the effect of the stiffened rib configuration on the mechanical behavior of the stiffened plate structure is analyzed under the given material parameters and geometric parameters of the stiffened plate. And the method of sine curve instead of straight line is used to optimize the structure. The research shows that the reinforcement effect of the plate is better than the positive distribution when the square configuration is distributed in the 45° direction, and the vertical distribution of the regular hexagon and the inner concave configuration has better plate reinforcement effect than the horizontal distribution and the 45° direction distribution; the smaller the angle between the pores of the stiffened configuration is, the better the reinforcement effect of the plate is; the use of sinusoids in the stiffened layer instead of the straight line boundary can significantly improve the bearing capacity of the stiffened plate; through the analysis of the crack path of the stiffened plate, it can be obtained that all the stiffened layers of the stiffened plate expand along the longitudinal rib wall at the load-bearing position after bending and deformation.关键词：Stiffened plate;Stiffened rib configuration;Bearing capacity;Reinforcement effect
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发布时间：2023-07-28 - 摘要：Combining the linear conjugate tooth profile with the planetary gear transmission with small tooth difference, taking the linear conjugate small tooth difference planetary gear reducer as the research object, the structure natural frequency and vibration mode of the reducer are obtained through finite element modal analysis, which shows the reducer has good structural dynamic characteristics; through the simulation analysis of vibration characteristics, the vibration law of the reducer under typical working conditions is obtained, and the vibration test experiment is carried out. The vibration experiment results are consistent with the simulation results. The vibration characteristics research results show that the input speed has a significant impact on the vibration amplitude and frequency of the linear conjugate small tooth difference planetary gear reducer.关键词：Straight line conjugate;Small tooth difference;Planetary reducer;Finite element mode;Vibration characteristics
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发布时间：2023-07-28 - 摘要：Cutouts are widely used in ships and offshore structures, which are used mainly for inspection, and they may be fitted for other purposes, such as passing pipes and reducing weight. In general, the existence of cutouts can reduce the structural strength, so the plates with cutouts（perforated plates） are given high importance at the structural design stage. In this regard, locally reinforced perforated plates are often used in shipyards to satisfy the structural buckling and ultimate strength requirements, but quantitative evaluations of the reinforced perforated plates have a little insufficient. To mitigate the reduction of the structural strength, flanged cutout has been adopted as a reinforcing method to achieve the structural buckling and ultimate strength increase, but no standard methodologies or recommendations are available for the cutout parameters of this stiffener. In this paper, a series of numerical studies were undertaken to analyze the buckling and ultimate strengths of different thickness flanged-perforated plates, for various cutout parameters（cutout radius, flanging length and flanging angle） under edge shear loading condition. The results can provide references for the design of flanged-cutouts in engineering.关键词：Flanged-perforated plates;Edge shear loading;Buckling;Ultimate strength
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发布时间：2023-07-28 - 摘要：Aiming at the wear failure of tubing string caused by the nonlinear flow-induced vibration（FIV） in high-temperature, high-pressure and high-yield（3H） gas wells, the nonlinear FIV model of tubing string was established using the element method, energy method and Hamilton variational principle, which considered the changes of wellbore trajectory, wellbore temperature/pressure, and contact of casing. A simulation experiment of the tubing string vibration was conducted to verify the correctness and validity of the nonlinear vibration model. Based on the White-Fleisher wear theory, a calculation method for the wear amount and depth of tubing string in 3H gas wells is proposed. The wear unit test is carried out, and the friction coefficient and wear efficiency are determined. On this basis, the influence of production rate, well angle, well section length, packer position and centralizer position on wear characteristics of tubing is systematically analyzed. The safety control methods of tubing string were proposed, namely, which shown that, firstly, with the increase of production rate, the wear life of the string decreases, and there is a sudden value, which can be determine using the analysis method, so that the field production allocation should be far away from the sudden production rate. Secondly, in the well trajectory design, the length of vertical well section should be reduced, and the length of build section and the angle of stable inclined section should be increased. Thirdly, there is an optimal position of packer and centralizer in the field, which is related to the well structure, string structure and downhole tool size, and can be determined by the proposed analysis method to guide the design of packer and centralizer. The research results can effectively improve the service life of tubing string in 3H gas wells.关键词：3H gas well;Tubing string;Nonlinear flow-induced vibration;Wear characteristics;Wear failure mechanism
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发布时间：2023-07-28 - 摘要：In order to solve the problem that the national standard cannot accurately calculate the bending stress of cylindrical helical gear with variable pressure Angle hob, a modified algorithm for calculating the bending stress of gear with variable pressure angle hob was proposed. An imaginary hob is introduced to meshing an equivalent spur gear, the equation of gear root transition curve is established based on conjugate meshing conditions, and the calculation method of curvature radius of any point of tooth root was given according to Euler-Savary formula. Combined with GB/T 3480—1997, the tooth profile coefficient and stress correction coefficient of gear processed with variable pressure Angle hob were calculated, and the bending stress correction value of tooth root was obtained. Then, Kisssoft/Romax analytical solution, finite element numerical solution values were used to verify the rationality of the tooth root bending stress correction algorithm. The results show that the tooth root bending stress correction algorithm can accurately calculate the tooth root bending stress based on variable pressure Angle hob machining gear; the tooth root bending stress correction algorithm can make up for the defect that using GB/T 3480—1997 cannot calculate the tooth root bending stress of cylindrical helical gear processed by variable pressure Angle hob, so as to realize the seamless connection between gear strength design and actual processing and solve the problem of inconsistency between the calculation model and the real object.关键词：Root stress correction;Tooth root transition curve;Tooth shape coefficient;Stress correction factor;Variable pressure angle hob
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发布时间：2023-07-28 - 摘要：For the centroid of crank connecting rod of automatic gun is moving continuously in longitudinal direction, under the condition of alternating high and low overload, the crank and connecting rod are subjected to the alternating time-varying inertia load, resulting in dynamic deflection and flexible impact of automatic gun; The causes and characteristics of flexible impact are analyzed. According to the definition of inertia load in D’Alembert principle, the inertial load is introduced as boundary condition in finite element analysis; Under the condition of the action of gunpowder gas with time varying law of Sergey Mamontov, the movement simulation analysis of crank connecting rod mechanism is carried out, and the law of crank and connecting rod overload and saltus is obtained; The dynamic deflection（deformation quantity） of crank connecting rod under inertia load is analyzed by finite element method. The results show that the connecting rod becomes the main source of vibration when the overload is more than 25 000 m/s~2. The dynamic deflection can be reduced by reducing the center distance of the rotating pair and the mass distribution near the centroid, thus reducing the dynamic deflection and reducing the flexible impact.关键词：Automatic gun;Flexible impact;Dynamic deflection;Crank;Connecting rod
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发布时间：2023-07-28 - 摘要：Negative Poisson’s ratio（NPR） structure has been widely used in aerospace, biomedicine and military equipment and other fields owing to its outstanding energy absorption and adjustable volume. A novel type of inclined cross-like cellular re-entrant structure with negative Poisson’s ratio in horizontal and vertical directions and positive Poisson’s ratio in 45° oblique direction is proposed. The analytical expressions of the equivalent elastic modulus, equivalent Poisson’s ratio and relative density of the structure are derived by using the energy method and Castigliano’s second theorem. The correctness of the analytical expression is verified by finite element simulation and experimental test. Meanwhile, the effects of the geometric parameters on the equivalent elastic modulus and Poisson’s ratio are given. The research results improve the mechanical properties of this kind of structure, and provide a theoretical basis for its promotion and application in engineering practice.关键词：Negative Poisson’s ratio;Mechanical properties;Auxetic structure;Cellular structure;Energy method
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发布时间：2023-07-28 - 摘要：The thermal fatigue damage of the brake disc caused by the thermal load of the friction brake when the electric brake fails is an important factor for the safety of train operation. A three-dimensional finite element model of the friction brake of the axle-mounted brake disc of the subway train was developed. The thermal-mechanical coupling of the brake disc in service brake and one emergency brake was investigated, and the temperature field and stress field of the brake disc under the two braking modes were obtained. Results show that the temperature distributions of the brake disc surface have similarities under different working conditions. In the beginning of braking, the temperature on the disc surface rises rapidly and quickly reaches the peak points of 166.81℃ and 151.5℃. Then the disc surface temperature decreases slowly. The initial stress field is dominated by mechanical stress. With the increase of braking temperature, thermal stress becomes the main influencing factor. The stress field has the similar distribution with the temperature field, but the stress peak appears later than the temperature peak. The thermal stress will cause the accumulation of material damage in the braking process which leads to the fatigue cracking of the brake disc.关键词：Brake disc;Temperature field;Stress field;Thermal-mechanical coupling
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发布时间：2023-07-28 - 摘要：To explore an accurate load spectrum editing method and discover the influence of different types of bench load spectrum on steering knuckle fatigue damage, the verified test field load spectrum was used as the data source and the knuckle endurance specification was simplified. The multi-body dynamics model of the vehicle was verified by the Kinematics Compliance（KC） test of the suspension and virtual iteration method. The bench random spectrum with the features of time and frequency domain was created by the domain editing method. Four-stage bench program spectrum was generated by damge equivalence principle. According to the result of the statistical knuckle’s pseudo damage in all directions and the modal test, the knuckle multi-axis virtual bench was built. The modal stress recovery method is used to compare the fatigue damage under the steering knuckle of the original spectrum, the bench random spectrum, and the bench program spectrum. The result shows that the damage distribution under the three excitations is consistent. The maximum damage ratios of the bench random spectrum and bench program spectrum to the original spectrum were 0.75 and 1.7, the accuracy of the load spectrum editing method and the engineering practicability of the virtual bench are verified. Finally, the load type of the steering knuckle fatigue damage and the road type were determined through the virtual bench transfer matrix, which provides data support for structural improvement.关键词：Steering knuckle;Multibody dynamics;Virtual iteration method;Bench test;Load spectrum;Fatigue damage
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发布时间：2023-07-28 - 摘要：The tank body of the transformer is filled with welds. Under vibration conditions, the fatigue damage of the tank often occurs at the internal defect position of the fillet weld. In order to analyze the effect of fillet weld defects on the fatigue life of the transformer tank, a finite element model of the transformer tank is established. According to the tank vibration test data, the fatigue analysis of the fillet welds on the sidewall of the tank was carried out in the nCode software, and the fatigue life of the fillet weld on the side wall of the lower transformer tank and the defect-free condition was obtained. Take the most dangerous fillet weld of the full tank sidewall fillet weld, and further establish a fillet weld model with partial defects, and analyze the influence law of the fatigue life of the fillet weld of the transformer tank when there are pores and slag defects. It was finally found that for slag inclusion defects, the greater the difference between the slag elastic modulus and the weld elastic modulus, the more likely it is to cause fatigue damage, and soft slag inclusions are more dangerous than hard slag inclusions; the increase in the size of pore defects will cause fatigue life reduce, the closer the pores is to the welding root, the shorter the fatigue life will be; and the pore defects are more likely to cause fatigue damage than the slag inclusion defects.关键词：Transformer oil tank;Fillet weld;Welding defects;Fatigue life
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发布时间：2023-07-28 - 摘要：Based on quick access recorder（QAR）data generated by engine operation, high pressure turbine（HPT）speed ratio of the right engine N2（the ratio of actual working speed to design speed of HPT）was extracted to compile turbine blade load spectrum. A fluid-thermal-solid coupling model was established, and the thermal boundary conditions required for calculation were established by combining QAR data and thermal analysis. The temperature, stress and strain distributions of HPT blade under different working conditions were obtained by solving the fluid-thermal-solid coupling problem with finite element software. The Manson-Coffin model and Larson-Miller model were used to predict the fatigue and creep life of the blade respectively, the influence of cooling on the life of blade was mainly analyzed. Finally, the fatigue-creep life of the blade was obtained by the linear damage accumulation theory. The results show that the fatigue life of blade is improved and the creep life is significantly improved after considering internal cooling, the predicted fatigue-creep life is close to the actual life, and this method can be used to predict the remaining life of the turbine blade of the engine and make the maintenance plan.关键词：QAR data;Load spectrum;High pressure turbine（HPT）blade;Fluid-thermal-solid coupling;Cooling;Fatigue-creep life
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发布时间：2023-07-28 - 摘要：A method for the fatigue life analysis of the differential housing of the electric drive assembly based on the measured load spectrum is proposed. Taking the housing of an electric drive assembly differential of an electric vehicle as the research object, a finite element model of the housing is established, modal analysis is carried out, and modal test verification is carried out. On this basis, with the measured load spectrum of the differential housing as the load input, and the actual vehicle driving conditions as the boundary constraints, the dynamics simulation analysis of the differential housing is carried out. Based on the dynamic finite element analysis results of the differential housing of the electric drive assembly, the nominal stress method and the modified S-N curve of the housing, the fatigue life of the differential housing of the electric drive assembly is analyzed and researched. The results show that the fatigue failure position of the differential housing is consistent with the fatigue failure position during actual driving. Based on the actual driving load spectrum, the actual driving fatigue life of the differential housing can be accurately analyzed.关键词：Differential housing of electric drive assembly;Modal test;Measured load spectrum;Dynamic analysis;Fatigue life
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发布时间：2023-07-28 - 摘要：The rotary excitation valve is one of the key components for the high-frequency and high-pressure electro-hydraulic excitation system, and its dynamic characteristics directly affect the performance of the entire excitation system.In order to study the dynamic characteristics of the rotary excitation valve under the coupling effect of Fluid-Thermal-Solid multi-field. First, the flow field of the rotary excitation valve was dynamically simulated by the sliding grid method through Fluent simulation, and the simulation results were verified by the measured flow rate of the rotary excitation valve. Then, the Fluid-Thermal-Solid multi-field coupling simulation of the rotary excitation valve was performed by using ANSYS. The thermal characteristics and thermal deformation laws of the rotary excitation valve was studied when the pressure difference between inlet and outlet ΔP are 5 MPa, 10 MPa, 15 MPa and the oil temperature are 20℃, 40℃, 60℃ respectively. The research results show that the internal flow field and temperature field of the rotary vibration valve are not uniformly distributed. The temperature of fluid near the valve core and the wall of valve body is higher, and the center temperature is lower.Due to the impact of the fluid at the outlet of rotary excitation valve, a local high temperature will be generated, resulting in thermal deformation of the valve core groove and the valve body outlet port.When the pressure difference between inlet and outlet at 15 MPa, the thermal deformation is 3.789 4 μm, and the oil inlet temperature at 60℃, the thermal deformation is 7.701 7 μm. Therefore, choosing the pressure difference between inlet and outlet and oil temperature is beneficial to the operational characteristics for rotary excitation valve. The theoretical data for the structural design and optimization of the rotary excitation valve are provided.关键词：Rotary excitation valve;Flow field;Fluid-Thermal-Solid coupling;Thermal deformation
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发布时间：2023-07-28 - 摘要：In order to solve the problem of bolt loosening and failure, based on self-developed aviation self-locking bolts, the influence of locking coating on locking performance of self-locking bolts was studied, and the locking effect of bolts with molybdenum disulfide（MoS2）, nylon 11（PA11） and polyvinyl chloride（PVC） coating materials was explored. Bolt connection locking mechanism are analyzed in this paper, by using the method of finite element simulation analysis and experimental verification, the air with the self-locking bolt lock the simulation and experimental research of the coating material selection, the mathematical model of the thread contour complete accurate set finite element meshing, boundary conditions, load simulation, experimental verification and test bench.The results show that the average locking torque of MoS2, PA11 and PVC is 1.06 N·m, 1.95 N·m and 2.18 N·m respectively in the finite element simulation. When PA11 is used as the coating, it is closer to the requirement that the maximum locking torque is less than or equal to 2.05 N·m in American standard IFI524. The bench test verifies that the average locking torque of the locking bolt with PA11 coating material is 1.82 N·m. Compared with the value of simulation analysis, it is within a reasonable fluctuation range, and PA11 as the coating material can meet the actual production requirements.关键词：Self-locking bolt;Coating material;Numerical simulation;Locking torque
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发布时间：2023-07-28 - 摘要：In order to reduce the influence of wing box deformation on the spoiler control surface of an aircraft, a linkage mechanism was adopted for the suspension at both ends of the spoiler. During the stiffness characteristic test, it was found that the monitoring data of the spoiler structure showed a jumping trend which was not consistent with the conventional rudder surface test and the theoretical expectation. In order to solve this problem, the fish-bone method was used to analyze the experimental phenomenon. After the problem was located quickly and accurately, the structure were re-analyzed by the nonlinear analysis method of geometric large deformation based on Patran/Nastran platform. A numerical calculation curve which is in good agreement with the experimental phenomenon is obtained. The factors affecting the support stiffness and the solution to the problem of large deformation of the structure are discussed.The analysis method provides a solution for the dynamic problems of flexible mechanism, and the numerical results and the discussion have guiding and reference value for the design improvement. The cause localization analysis process of the test phenomenon can provide reference for other experiments.关键词：Spoiler;Linkage mechanism;Fish-bone;Large deformation
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发布时间：2023-07-28
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