最新刊期
期 4 ， 2023
- 摘要：The outer ring spalling failure angle position of the rolling bearing has an important influence on the vibration size and service life of the rotating machine. It is necessary to judge the outer ring spalling failure angle within the load-bearing interval. Based on the peak change law of the acceleration vibration signal, a fault location method was proposed for ball bearing outer ring spalling. This method established the Lagrangian dynamic equation with time-varying impact force. By analyzing the change trend of the contact force in the bearing area of the ball bearing, the law of the peak ratio of the absolute value of the vibration acceleration signal was obtained by analogy, and the impact point of the acceleration vibration signal was analyzed. For nearby locations, a new judgment index was proposed, and the specific location of the fault was obtained. Simulation and experiment results show that there is a corresponding functional relationship between the horizontal vertical synchronization peak ratio of the vibration signals at different positions of the ball bearing outer ring spalling fault. Simulation and experiment verify the accuracy of the positioning law. It provides a theoretical basis for the diagnosis method to determine the location of the ball bearing outer ring spalling fault location.关键词：Rolling bearing;Outer ring fault;Localization law;Peak ratio
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发布时间：2023-09-25 - 摘要：Aiming at the problem of insufficient labeled samples in the process of rolling bearing fault diagnosis, a rolling bearing fault diagnosis model based on semi supervised Laplace score（SSLS） and kernel principal component analysis（KPCA） is proposed by combining with the idea of feature selection and secondary mining. SSLS applies the semi supervised idea to the Laplace score feature selection method, uses a small number of labeled samples and a large number of unlabeled samples, and combines KPCA to excavate fault features for a second time. At the same time, particle swarm optimization-based support vector machine（PSO-SVM） algorithm is used for fault classification. Finally, the model is applied to the process of experimental data analysis. The results show that the model can not only reduce the workload of sample marking, but also maintain a high accuracy in rolling bearing fault classification, which verifies the effectiveness and engineering practicability of the model.关键词：Feature selection;Semi supervised Laplace score;Kernel principal component analysis;Particle swarm optimization-based support vector machine;Fault diagnosis
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发布时间：2023-09-25 - 摘要：When the rolling bearing has a local fault, it will produce a complex vibration response. From the objective reality and irregularity of the inner ring′s actual fault shape, the displacement excitation function is introduced to qualitatively analyze the gradual change of the ball position when it passes through the fault area, and a random number sequence is used to list the characteristics of the irregularity of the bottom. Considering the radial load of the bearing and the slipping phenomenon of the balls through the fault area, a bearing inner ring dynamics model of the local gradient fault is established, and the accuracy of the model is verified by comparing and analyzing the characteristic frequency values of the fault under different rotational conditions.关键词：Failure gradient;Displacement excitation function;Random number sequence;Sliding ratio;Fault characteristic frequency
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发布时间：2023-09-25 - 摘要：Taking the seat vibration system of a certain type of engineering vehicle as an object, using the characteristics of adaptive network-based fuzzy inference system（ANFIS） self-learning and fuzzy reasoning, a semiactive control method of seat suspension vibration based on ANFIS was proposed, which solved the problem of excessive seat vibration in the working process of engineering vehicles. Firstly, the vibration process of the seat suspension of engineering vehicles was analyzed, and the dynamic model of the seat suspension was established. Then, the fuzzy neural control system of seat suspension was designed by adding feed-forward and feedback links. Finally, the control effects of different vibration excitation frequencies, different controller control objects and the input of measured seat signals were observed respectively. The results show that the fuzzy neural control system reduces the vibration energy and frequency of the seat, and the root mean square value of the seat vibration displacement is 52% to 66% of the passive suspension seat.关键词：Engineering vehicle;Seat suspension;Vibration control;Semi active control;ANFIS
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发布时间：2023-09-25 - 摘要：A two-degree-of-freedom collission vibration system model with nonlinear constraints and initial precompression is established. The hysteresis region and distribution of the system are studied by using the 4-order Runge-Kutta numerical algorithm and multi-parameter co-simulation method. The stability of the co-existing motions in the hysteresis region is analyzed by cell mapping method. Finally, the influence of the change of basic parameters on the hysteresis domain of the system is deeply studied. The results show that the stability of coexisting motion changes with the change of excitation frequency in hysteresis domain. The decrease of the elastic stiffness ratio will reduce the hysteretic frequency of the system.关键词：Pre-compression;Nonlinear constraints;Hysteresis domain;Coexisting attractor;Multi-parameter co-simulation
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发布时间：2023-09-25 - 摘要：Shot peening is an important mechanical treatment process for metal surface. Its treatment quality is closely related to the shot motion behavior which is derived by high speed airflow. To accurate control shots motion and improve treatment quality in shot peening, it is great significance to explore an accurate measurement method and uncover the law of shots motion in peening process. With high speed camera, a high-speed image data acquisition system for shots in peening process was established. In addition, the images of instantaneous spatial position of shots in peening were captured. In order to improve contrast, Photoshop was used to covert the collected photos into black-and-white binary images. The open source particle image velocimetry（PIV） software PIVLab was used to analyze these images, and the velocity field of shot flow was carefully calculated. The results show that, under the condition of 0.4 MPa gas pressure and 0.4 mm cast steel shot, the scattering cone angle of shot flow was 10 degrees, and the maximum velocity of shot was about 46.5 m/s. On different spatial sections, the velocity of shots presents Gaussian distribution. In addition, the standard deviation of this Gaussian distribution is increased with enlarge the distance between shots and nozzles. The velocity of shots increases rapidly to a stable value after leaving nozzle, and the velocity variation conforms to the Logistic function. Compared with the empirical formula, the obtained formula of velocity field distribution of shots is more accurate. Furthermore, the spatial distribution characteristics of shots flow in peening process can be exactly gained.关键词：Shot peening;Shots;PIV;Velocity field;PIVLab
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发布时间：2023-09-25 - 摘要：In order to construct a constitutive model that reasonably describes the changing relationship of flow stress of 440C stainless steel, quasi-static and dynamic compression experiments were carried out with the help of a universal testing machine and a Hopkinson compression bar device. Based on the obtained experimental data, the parameters of the original J-C constitutive model were calibrated, and its applicability and prediction accuracy for describing the stress-flow behavior of the studied materials were discussed. Based on the analysis results, a modified J-C constitutive model considering the coupling among strain, strain rate and temperature was proposed, and the model parameters were calibrated. The experimental data and the model predicted value were compared and analyzed, and the validity of the proposed model was evaluated by three statistical parameters: correlation coefficient R, average relative error AARE and root mean square deviation RMSE. The results show that the dynamic mechanical behavior of 440C stainless steel is jointly dominated by the coupling between strain, strain rate and temperature. The correlation coefficient R of the proposed modified J-C constitutive model is 0.995 9, the average relative error AARE is 0.073, and the root mean square deviation RMSE is 0.761 8, which can reasonably describe its stress flow behavior.关键词：440C stainless steel;Hopkinson pressure bar;J-C constitutive model;Coupling action
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发布时间：2023-09-25 - 摘要：The lubrication state of wire rope has an important influence on the working characteristics and fatigue life of wire rope. 6X19 steel wire rope is taken as the research object, and three kinds of steel wire rope without grease lubrication, partially lubrication and fully lubrication are selected. The bending fatigue tests are carried out on the bending fatigue test machine under different tension states, and the fatigue damage states of each specimen in different stages are statistically analyzed and microscopic studied. Under good lubrication condition, between wire rope and pulley rope groove of the oil film to improve the contact state, reduce the friction coefficient between steel wire rope, steel wire surface is not easy to wear and tear scratches, delay the formation and extension of cracks and improve the steel wire rope section stress distribution and reduce the stress concentration phenomenon, make more effective load effect on the number of steel wire. The steel wire in the rope is fully drawn, and the proportion of necked broken wire in the total broken wire is higher than that of the wire rope with poor lubrication condition. For the wire rope with poor lubrication condition, the proportion of flush fracture is high, and the steel wire in the rope is not fully drawn, resulting in wire breakage due to local damage. Under the same lubrication condition, the increase of tension force destroys the lubricating oil film between the wire rope and pulley groove on the one hand, on the other hand, under the action of compressive stress, the lubricating oil in the rope core is not easy to infiltrate into the side of the wire rope and pulley groove, which deteriorates the lubrication state.关键词：Steel wire rope;Bending fatigue test;Lubrication;Bending fatigue strength;Sheave
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发布时间：2023-09-25 - 摘要：The location of the defect in the CL65 wheel rims was determined by ultrasonic detection, and workblank samples containing the defect were taken out and processed into fatigue samples. Through the fatigue test carried out on Shimadzu electro-hydraulic servo fatigue testing machine, the fatigue life of samples with defects was obtained.After the test, the shape, size and chemical composition of defects were analyzed. The results show that the main component of shrinkage defects is MnS and the main component of inclusion defects is hard oxides. The fatigue life of samples with shrinkage defects is longer than that of samples with inclusion defects. To analyze the difference between the influence of the two defects on the fatigue properties of wheel materials, the finite element models were established based on the tessellated stress theory. Compared with inclusion defects, the tessellated stress at the interface between shrinkage defects and the matrix is significantly reduced and the extent of stress concentration around defects is small. Therefore, the damage of shrinkage defects containing MnS on the fatigue properties of wheel materials is significantly less than that of oxide inclusions.关键词：Inclusion defects;Porosity defects;Manganese sulfide;Hard oxides;Tessellated stress
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发布时间：2023-09-25 - 摘要：In recent years, negative Poisson′s ratio（NPR） materials have attracted extensive attention from the academic community due to their excellent mechanical properties and huge application potential in traditional industrial fields. The mechanical properties of a new type of material with negative Poisson′s ratio（based on YSH structural cell） under dynamic compression are designed and studied. Through the finite element simulation method, the response difference of different structural parameters（inclined wall angle, width ratio, aspect ratio） to the equivalent elastic mechanical performance parameters of the cell is compared, and the influence of these structural parameters on the energy absorption performance is explored, and the research is further extended to the structure under four common functional gradient arrays. The energy absorption effect of the structure is evaluated by three indexes: energy absorption, energy absorption efficiency and platform stress. The study shows that, inclined wall inclination θ the larger, the better the energy absorption performance of the whole structure; width ratio α it has little influence on the equivalent mechanical properties and energy absorption of the whole structure; aspect ratio β the smaller the value, the more obvious the negative Poisson′s ratio effect of the structure, but on the contrary, the larger the value, the higher the energy absorption efficiency. The results can provide a reference for the function-oriented design of materials with negative Poisson′s ratio.关键词：Negative Poisson′s ratio;Equivalent performance;Mechanical property;Energy absorption performance
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发布时间：2023-09-25 - 摘要：In order to improve the reliability of the front subframe of a front drive SUV, the strength and fatigue characteristics of the subframe under different working conditions are analyzed by comprehensively using the finite element method, multi-body dynamics theory, strength analysis theory and fatigue analysis theory, and through the established three-dimensional model of the front subframe and the rigid flexible coupling model of multi-body dynamics. The strength and fatigue tests of the subframe are carried out. The simulation results show that the deformation of steering connection point is 2.924 mm and 3.411 mm respectively under straight driving and steering conditions, and the deformation of stabilizer bar and torsion arm is 3.383 mm and 2.695 mm respectively. The strength test results show that, in the straight driving and steering conditions, the deformation of the steering point is 3.263 mm and 3.622 mm respectively, which are 11.59% and 6.19% higher than the simulation results. The deformation of the connection point of the stabilizer bar and the connection point of the torsion arm are 3.538 mm and 2.957 mm respectively. The experimental results are 4.58% and 9.72% higher than the simulation results respectively. The results show that there is no obvious difference between the experimental results and the simulation results, and the deformation of the subframe at each point conforms to the design. The fatigue test results of the subframe show that there are no cracks and plastic deformation in the subframe after 800 thousand torsion arm fatigue tests, 400 thousand braking force fatigue tests and 800 thousand lateral force fatigue tests, indicating that the fatigue characteristics of the subframe meet the requirements.关键词：Front subframe;Strength;Fatigue characteristics;Simulation;Tests
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发布时间：2023-09-25 - 摘要：There are two methods to verify the durability characteristics of a new designed leafspring, there are physical test which takes more time and cost and CAE simulation which is time-saving and cost-saving. Aiming at coming up an effective CAE simulation of the leafspring life, the CAE simulation for stiffness and strength with rig test is validated. Base on the validated CAE method, with material property from test, CAE fatigue simulation is conducted with different surface treatment factor and validated with rig test to find out the best parameter for good life correlation. Finally, an effective CAE life prediction of automotive leafspring is provided, and the solution can serve as a good reference for the industry.关键词：Automobile;Leafspring;Fatigue life;Rig test validation
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发布时间：2023-09-25 - 摘要：Shaft-hole fit is one of the most basic assembly structures for mechanical products, and the fit clearance plays a decisive role in the performance, safety, and effective operation of the product. Taking the uncertainty of the shaft-hole clearance fit in the positioning process as the research objective, based on the analysis of the factors affecting the uncertainty of the shaft-hole clearance fit in the positioning process, an information entropy model of the shaft-hole machining uncertainty is constructed to quantitatively describe the uncertainty of the shaft-hole clearance fit. Propose using the shaft-hole clearance fit uncertainty index to comprehensively characterize the uncertainty of the shaft hole clearance fit accuracy retention, and the inherent relationship-between the uncertainty index and the reliability of the accuracy of shaf-hole clearance fit is analyzed; the effectiveness and feasibility of the method are verified through examples.关键词：Clearance fit;Uncertainty;Information entropy;Multi-factor analysis
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发布时间：2023-09-25 - 摘要：In order to improve the robustness of the compliant hinge, genetic algorithm and BP neural network methods are introduced to optimize the parameters of the compliant mechanism. Orthogonal experiments are used to select training parameters and test parameters, a BP neural network model is established, and by using the nonlinear fitting ability of the neural network and the global search and optimization ability of genetic algorithm. The flexibility and natural frequency signal-to-noise ratio are used to find the global optimum in the selection range for single and multi-objectives. It is not only limited to the permutation and combination of selected factor levels, but also provides a new solution to improve the compliance hinge robustness. The experimental results show that the comprehensive evaluation function of the compliant hinge is better, which achieves the purpose of robust optimization design, and proves the effectiveness of the method.关键词：Compliant mechanism;Flexibility;BP neural network;Robust optimization;Genetic algorithm
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发布时间：2023-09-25 - 摘要：In order to obtain the classification prediction performance of TBM oil temperature, a camel walking resistance and walking endurance strategy based on natural weather phenomena was proposed to improve the camel algorithm to optimize the prediction model of random forest. Firstly, the traditional camel algorithm was improved by using the proposed strategies. The results showed that the improved camel algorithm has good convergence speed and convergence accuracy. Secondly, the improved camel algorithm was used to optimize the parameters of the TBM oil temperature prediction model established by the random forest to obtain the best model. Finally, on this basis, the classification prediction research and analywis of the test data set was carried out. The experimental results show that the prediction accuracy of the proposed model reaches 97.71%, compared with the traditional random forest model, the accuracy is mproved 6.38%, which can achieve the purpose of avoiding the failure of the shield machine caused by high oil temperature. It provides the basis for the whoce machine material-structure-control future multi-disciplinary cooperative optimization design and performance prediction.关键词：Improved camel algorithm;Random forest classification;Parameter optimization;TBM;Oil temperature prediction
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发布时间：2023-09-25 - 摘要：In view of the small number of data samples in the field test, a method of data expansion by using probability distribution and proxy model was proposed. This method determines the interval division and the number of sample points that need to be generated in each interval by analyzing the basic probability characteristics of the data. The sample points were generated based on the back propagation（BP） neural network method to build a semi-physical simulation system proxy model, and were selected by the histogram statistical method. Therefore, the additional sample points not only retain the probability characteristics of the original data, but also have the physical connotations. The expanded testing data improved the aircraft′s landing point coordinate information and the accuracy of the landing point data fusion model. The practicability and effectiveness of the method were verified through the field and semi-physical simulation experiments of the aircraft 534A respectively.关键词：Aircraft landing point;Field test;Data expansion;Basic probability allocation;Proxy model;Data fusion
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发布时间：2023-09-25 - 摘要：In order to solve the optimization design problem of complex shape of underwater glider and improve the optimization efficiency of Kriging surrogate model while improving its lift drag ratio, an adaptive surrogate optimal algorithm is proposed. The proposed improved parallel expectation improvement（PEI） criterion and probability of improvement（PI） criterion are used for global exploration, and the minimizing surrogate prediction（MSP） criterion is used for local exploration. The switching between global exploration and local exploration is realized according to the relationship between new sample points and known sample points. The proposed algorithm, the maximum expected improvement（EI） criterion multiple expectation of improvement（q-EI） and the improved probability improvement（IPI） are combined through a mathematical example. The result shows that the proposed algorithm converges faster and has higher accuracy. Finally, the optimal algorithm is used to optimize the shape of the underwater glider, and the maximum lift drag ratio is increased by 19.37%.关键词：Kriging surrogate model;Surrogate optimal algorithm;Numerical simulation;Parallel filling;Underwater glider
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发布时间：2023-09-25 - 摘要：In order to research the influence of the web deflection on the bend-twist coupling characteristics of large wind turbine blades, the CAD model of NREL 5 MW blade is established based on NX secondary development, the aerodynamic loads of the blade are obtained by CFD method, the blade bendind angle and twisting angle are solved by the node displacement method to analyze the influence of web deflection for bend-twist coupling blade. The results show that the offset web helps to achieve the bend-twist coupling of blades. Under the action of aerodynamic load, the bending and twisting angle both increase along spanwise direction of blade gradually, and reach the magnitude at the tip of the blade; in forward bias, negative correlation between twist angle and offset, reverse bias is the opposite; positive bias blades bend-twist coupling coefficient is decreasing trend with the increase of deflection angle, reverse bias blade are greater than the conventional blade.关键词：Wind turbine blade;Bend-twist coupling;Composite material;Structure coupling;Node displacement method
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发布时间：2023-09-25 - 摘要：Stiffness performance is an important index to evaluate the bearing capacity of array framework and radar working accuracy. The mean square root of reflector deformation is often used to measure the stiffness performance of array, but the root mean square method can only analyze the overall stiffness of the framework, and can not evaluate the stiffness of local modules and their contribution to the overall stiffness.To solve this problem, the stiffness contribution of substructure（λ） and substructure bearing coefficient（α） were proposed based on the design criteria of substructure strain energy and uniform strain energy density, which has high calculation efficiency and wide application. Through this two parameters, the stiffness contribution of substructure in complex structure can be evaluated and analyzed conveniently. Finally, taking a typical vehicle mounted phased array radar as an example, the contribution and matching of the box girder substructure and T type joint substructure to the array framework were analyzed detailly, and then the influence of the array panel on the substructure stiffness contribution of the frame was analyzed. Through the analysis, some improvement design suggestions were put forward for the lightweight and bearing capacity design of the array antenna frame.关键词：Stiffness characteristics;Stiffness contribution;Bearing coefficient;Substructure;Joint;Antenna array
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发布时间：2023-09-25 - 摘要：In order to meet the requirements of machining accuracy indexes such as the entry, exit and shape of micro-hole, a multi-objective parameter optimization weigh method for micro electrical discharge machining（EDM） based on grey relational analysis（GRA） and entropy weight method is proposed.By designing orthogonal experiment and processing test for H62 brass, the grey relational coefficient of each index of the experiment result sequence is calculated.The entropy weight method and grey relational analysis method are used to comprehensively evaluate the model, and the grey relational degree of each experiment sequence is obtained, and the mean value analysis is carried out to realize the transformation from multi-objective optimization to single objective optimization.The research results show that the entry Overcut（EnOV）, exit Overcut（ExOV） and taper（TA） of the optimized process parameters are reduced by 8.97%, 4.11% and 8.33% respectively compared with those of the H-22 group with the largest grey relational degree, and the machining accuracy of micropores is improved.关键词：Micro EDM;Entropy weight method;Grey relational analysis;Orthogonal experiment;Micro-hole
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发布时间：2023-09-25 - 摘要：The accuracy of traditional milling force prediction model is low, and it is difficult to provide effective support for the reasonable selection of process parameters in practical production, by synthetically considering the equivalent turning force model of working angle, cutting edge arc and radius of tool tip arc, in this model, the actual turning tool is equivalent to the ideal turning tool model to identify the material constant, the chip flow angle and the average friction angle in the material constitutive equation, according to the oblique cutting model, the shear stress on the main shear plane and the F0 vector of the unit cutting force at different cutting speeds are calculated, thus the instantaneous cutting force on the front face of the end mill can be calculated, the three-dimensional cutting force of end mill in X-Y-Z coordinate system is obtained by coordinate transformation. The prediction of the cutting force model is verified by simulation and experiment.关键词：Equivalent model;Unit cutting force;Prediction of milling force
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发布时间：2023-09-25 - 摘要：In order to investigate the ballistic performance, failure patterns and energy dissipation of aluminum alloy target plates against the impact of different strength and head shape projectiles, the three-dimensional models of 3 mm thick 6061-T651 aluminum alloy target plates impacted by lightweight-deformable projectiles of different materials were established by Abaqus finite element software, and the modified Johnson-Cook（MJC） constitutive model and the Lode-dependent modified Mhor-Coulomb（MMC） fracture criterion are used for numerical simulation. The results show that the corresponding ballistic limit velocity of the target plates are the highest when the low strength 6061-T651 aluminum alloy are used as the projectile material, and the ballistic limit velocity of the target plates decrease with the increase of the projectiles strength. The impact will cause a more complex failure patterns of the target plates when the projectiles strength is low, and at the same time, the plastic deformation of the projectiles head occur to different degree; the projectiles strength has a significant effect on the energy dissipation ability of the target plates. The ballistic limit velocity corresponding to the lightweight-deformable blunt-head projectiles are higher than that of the ogival-head projectiles.关键词：Lightweight-deformable;Lode numerical simulation;Ballistic limit velocity
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发布时间：2023-09-25 - 摘要：The oil film temperature of the spherical hybrid sliding bearings would increase due to the friction and shear of the lubricating oil at high speed or super high speed, which leads to the thermal deformation of bearing and rotor. As a result, the deformation seriously affects the rotation accuracy of the spindle, because it is in the same order of magnitude as the oil film thickness. Therefore, the fluid lubrication mathematical model is established by taking the spherical hybrid sliding bearings with orifice throttling mode as the research object, and the Reynolds equation and energy equation of lubricating oil film are derived. The pressure distribution and temperature distribution of oil film of the spherical hybrid sliding bearings are calculated by combining the finite difference method and relaxation iteration method. The influence of working parameters on bearing capacity and oil film temperature rise was investigated. The results show that the oil film shear effect is stronger and the temperature rise increases with the increase of rotating speed and the decrease of oil film thickness. When the speed is 3 000 r/min and the oil film thickness is 28 μm, the maximum temperature rise of the bearing is 18.65 K higher than that of 1 000 r/min. When the speed is 3 000 r/min and the oil film thickness is 20 μm, the maximum temperature rise of the bearing is 27.685 K higher than that of the oil film thickness of 28 μm.关键词：Spherical hybrid sliding bearings;Orifice throttling;Load capacity;Temperature field;Thermal deformation
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发布时间：2023-09-25 - 摘要：The end face meshing worm drive with tapered roller envelope has many simultaneous meshing tooth pairs and can eliminate clearance. According to the gear meshing principle and differential geometry principle, the meshing mathematical model of the transmission pair is established, the worm tooth surface equation and meshing function are deduced, and the meshing performance calculation formula is obtained. Matlab software is used to analyze the effects of small end radius, throat diameter coefficient and half cone angle of cone on the meshing performance evaluation parameters of the transmission pair induced normal curvature, lubrication angle, relative entrainment speed and self rotation angle. The analysis results show that the transmission pair has good meshing performance.关键词：Cone rolling envelope;End face engagement;Meshing performance
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发布时间：2023-09-25 - 摘要：Taking the spherical sliding bearings with orifice throttling as the research object, the mathematical model of lubrication of spherical hybrid sliding bearings is established and the Reynolds equation under laminar flow state is deduced from this model. The pressure distribution of the oil chamber and oil edge are calculated according to the flow conservation principle of the orifice throttle. Combining with the finite difference method and relaxation iterative method to solve the disturbance pressure control equation which is derived by means of perturbation method. The stiffness coefficient and damping coefficient of spherical sliding bearings are used to study the influence of supply pressure, rotating speed, average oil film clearance and other parameters on the dynamic characteristics coefficient of the bearing through numerical analysis. The results show that as the oil film clearance decreases and the oil supply pressure increases, the stiffness coefficient and damping coefficient will increase accordingly. As the rotating speed increases, the changing trend of the direct stiffness is small while the decreasing trend of the direct damping is obvious. When the oil film clearance is 20 μm, the stiffness coefficient and damping coefficient of spherical hybrid sliding bearings reach the maximum. The increasing of rotating speed has little effect on the stiffness while the damping coefficient will be significantly reduced.关键词：Orifice throttling;Spherical hybrid sliding bearings;Flow conservation principle;Reynolds equation;Perturbation method;Dynamic characteristics
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发布时间：2023-09-25 - 摘要：In order to ensure the secondary part at the front end of vehicles absorb the impact energy as much as possible in case of collision, reduce the impact on main parts, and ensure the safety of passengers and drivers, the energy absorption structure is set at the front end of the vehicle to improve the passive safety. Firstly, compared different standards at home and abroad and their requirements for collision conditions. Secondly, ASME RT-2 standard is selected as the standard, two energy absorbing structures are designed respectively. Structures mainly include head girders, corner posts and crash elements. The result shows that both structures can absorb more than 1.22 MJ of energy through the simulation by Ls-Dyna. At last, energy absorbing structures which has two energy absorb stages is tested to verify the reliability of the simulation results, and it is proved that the structure can meet the requirements of ASME RT-2.关键词：Railway vehicle;Absorbing energy structure;Crash worthiness;Finite element analysis;Passive safety
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发布时间：2023-09-25 - 摘要：In order to study the frequency domain calculation method of non-Gaussian excitation, Gaussian mixture model（GMM） is introduced. The measured non-Gaussian excitation is transformed into probabilistic power spectrum（PPSD） through GMM model, so that the non-Gaussian excitation is introduced into the frequency domain. The corresponding non-Gaussian rain flow distribution is obtained by simulation and GMM-Dirlik model, and the damage of the specimen is calculated. At the same time, according to the Gaussian hypothesis, the excitation is directly converted into PSD for damage calculation. Then, the bench test is carried out to obtain the stress response of the specimen, the rain flow distribution in the stress range is obtained by rain flow counting, and the damage of the specimen is calculated. After comparing the test results with the simulation results, it is found that the relative error between the results obtained by GMM-Dirlik model and the test is 10.8%, while the relative error between the results obtained by Gaussian hypothesis and the test is large, which is 45.3%, which further explains the risk of non-Gaussian excitation damage evaluated by Gaussian hypothesis. Finally, the difference between non-Gaussian excitation and Gaussian distribution probability density function is compared to explain the concave phenomenon of measured stress rain flow distribution at the middle stress level and the reason why the damage of non-Gaussian excitation is larger than that of Gaussian excitation.关键词：Gaussian mixture model;Non-Gaussian excitation;Frequency domain calculation;Random vibration
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发布时间：2023-09-25 - 摘要：Fretting fatigue failure of 2024 aluminum alloy under alternating normal load was investigated. A biaxial fretting fatigue test system is designed which can apply alternating phase load and distal load. Through Abaqus finite element analysis, the normal loading device of the test bench was analyzed and calculated, and the influence of the force conduction error and the swing angle of the fretting pad on the test accuracy was investigated, the accuracy of loading test machine is verified. The influence of phase difference of 0°, 45° and 90° on fatigue life of 2024 aluminum alloy under alternating normal load was studied. The test results show that the life of 2024 aluminum alloy specimens increases with the increase of phase difference. Through the analysis of wear state, it is found that the influence of wear is small when the phase difference is 0° and 45°, and the life increases with the increase of phase difference. When the phase difference is 90°, the wear is more serious. Under the joint action of wear and fatigue damage, the fatigue life of specimens at 90° phase difference is further increased. The overall trend of fretting fatigue life of specimens under alternating normal load is that the life increases with the increase of phase difference, and the wear increases with the increase of phase difference.关键词：Fretting fatigue;Alternating normal load;2024 aluminum alloy;Finite element analysis
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发布时间：2023-09-25 - 摘要：Aiming at the problem of fatigue life prediction of aluminum alloy wheel hub, a fatigue life prediction model considering damage accumulation is proposed and tested. The Finite Element Models of a wheel hub under bending fatigue test and radial fatigue test are established, and the main failure positions are studied by simulation analysis. The S-N curves of material and part are established by using the nominal stress method, and the average stress of the asymmetric cyclic load borne by the wheel hub is corrected by using the Morrow line. Considering the rotation process of the wheel hub, a theoretical model for predicting the fatigue life is constructed by using the linear cumulative damage theory. Taking an aluminum alloy wheel hub as an example, the life calculated by the theoretical model is 448.2 thousands revolutions. Compared with the fatigue life of 473.3 thousands revolutions given by the bending fatigue test, the error is about 5.6%, which verifies the effectiveness of the fatigue life prediction theoretical model.关键词：Wheel hub;Fatigue life;Damage accumulation;Bending fatigue test
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发布时间：2023-09-25 - 摘要：Aiming at the problem of fatigue fracture of pipeline connectors, a finite element model of pipeline connectors in aircraft hydraulic system is established. Based on the theory of continuous damage mechanics, the vibration fatigue life of pipeline connectors with assembly stress is predicted. The results show that under normal assembly state, the fatigue crack initiation point of pipeline connectors is located at the contact part between flared conduit and flat nozzle. With the increase of vibration load amplitude, the fatigue life of pipeline connections decreases gradually. When there is axial assembly deviation, due to the influence of stress concentration, the fatigue crack initiation point of pipeline connector is located at the connection between pipe flare and pipe body. The axial assembly deviation weakens the fatigue strength of pipeline connectors. The larger the axial deviation is, the smaller the fatigue life of pipeline structure is.关键词：Pipeline connector;Damage mechanics;Axial deviation;Fatigue life
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发布时间：2023-09-25 - 摘要：In order to study the fatigue crack propagation of the fuselage skin under uniform pressurized cyclic load, experiments were carried out with the self-made aircraft fuselage skin uniform pressurized fatigue device. Firstly, the stress intensity factor was calculated by the extended finite element method. Then, the deflection angle of the crack was calculated based on the maximum circumferential stress criterion and the strain energy density factor criterion, and the fatigue crack propagation path of the fuselage skin was predicted. Finally, the fatigue fracture was analyzed under scanning electron microscope. The results show that the crack propagation paths predicted by the two criteria are basically consistent with the crack propagation path obtained by experiment.The surface cracks of the fuselage skin are mixed mode cracks. With the increase of the crack length, KⅠ first increases and then decreases, KⅡ first decreases rapidly to around 0, then oscillates around 0, and finally increases rapidly when the lower hole is about to penetrate. Observing the fatigue fracture shows that the fatigue cracks are initiated by multiple fatigue sources. The crack propagation zone has typical quasi-cleavage fracture characteristics, and the fatigue crack growth rate first increases and then decreases with the increase of crack length. The instantaneous fracture zone is a typical dimple feature with different sizes.关键词：Fuselage skin;Uniform pressurized;Fatigue crack;Crack propagation;Fatigue fracture
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发布时间：2023-09-25 - 摘要：In order to solve the problem of single design method of the existing guided anti-collision pad, the guided anti-collision pad is designed to meet the requirements of the current regulations, and based on the collision-resistant topology optimization method, by establishing the model of the car-anti-collision pad and topologically carrying out the topology optimization analysis under the condition of its positive encounter, from which to extract the basic configuration of the energy absorption unit, to the positive collision of the car center acceleration size as an evaluation index, the use of orthogonal design and robust design method to further optimize the size of the energy absorption unit, and finally obtain the optimal size of the energy absorption unit. The simulation results show that the design method based on collision resistance topology optimization is effective, and the TS-grade guided anti-collision pad is designed to meet the current requirements关键词：Topology optimization;Guiding anti-collision pad;Robustness design
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发布时间：2023-09-25 - 摘要：The cycloid gear is the key component of the RV reducer, and the hole structure of the cycloid gear has a great influence on the transmission stability of the of the RV reducer. Based on the meshing contact analysis between the cycloid gear and pin of transmission system, the number of actual meshing teeth pairs of the cycloid gear were obtained. The meshing angle of each tooth pair and the comprehensive meshing stiffness were calculated. Taking the comprehensive meshing stiffness as elastic constraint condition in finite element software, the dynamics harmonic resonance analysis of cycloid gear was carried out. The position of maximum vibration and deformation is located at the fan-shaped lightening hole of cycloid gear plate. According to the different shape of fan-shaped holes of cycloid gear, the dynamics simulation was carried out by orthogonal test with three factors and four levels. The results show that the radius of the top and bottom circle of the fan-shaped hole is always the key factor to the vibration of the cycloidal wheel with the increase of rotation speed, while the vibration increases gradually for the radius of the inverted circle, and decreases for the angle between the waist and the waist. The conclusions are helpful for the structure design of cycloid gear wheel.关键词：Cycloid gear;Comprehensive meshing stiffness;Orthogonal test;Structure optimization
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发布时间：2023-09-25 - 摘要：A S-N curve for predicting the life of welding joints is proposed to accurately predict the fatigue life of SUS304 stainless steel spot welded joints on construction machinery. According to several common structural forms of spot welding joints, tension shear fatigue samples with different plate thickness combinations were prepared, and the fatigue life data of the samples were obtained through fatigue test. The accurate nugget diameter is obtained by CT scanning experiment, then the finite element model of the specimen is established, and the accuracy of the model is verified by optical strain measurement experiment. Then, based on Rupp equivalent structural stress method and fatigue test data, S-N curves integrating different plate thickness combinations and load ratios are established, and Goodman correction method is used to eliminate the influence of load ratio. Finally, the finite element model of vibrating conveyor is established, the transient dynamic analysis is carried out to obtain the structural stress of vibrating groove solder joint, whose life is predicted based on the established S-N curve. The results show that there is no fatigue problem in each solder joint of the vibration groove but solder joint redundancy, so it can be designed lightweight.关键词：304 stainless steel;Spot welding;S-N Curve;Fatigue life;Vibrating conveyor
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发布时间：2023-09-25 - 摘要：In the optimization design of twin-screw compressor line, the influence of geometric parameters on compressor performance is considered to be different. In order to judge the advantages and disadvantages of the designed profile more directly, proposed a comprehensive performance index to judge the advantages and disadvantages of the rotor profile, and designed a rotor with better profile based on the comprehensive performance index for fluid simulation and experimental verification. Compared with the original profile, the length of the contact line of the optimized profile increases slightly, the area of leakage triangle decreases, area utilization coefficient increased. But the single performance index which reflects the whole performance index is better, which also preliminarily proves the correctness of the proposed method.关键词：Comprehensive performance;Screw rotor;Meshing line;Optimization design
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发布时间：2023-09-25
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