最新刊期
卷 46 ， 期 3 ， 2024
- 摘要：Non-stationary and nonlinear vibrating signals in rotating mechanical equipment are always disturbed by noises from working environment and other devices. Bearing fault signals in mechanical systems are reduced which makes it difficult to extract fault characteristic, diagnose fault type. Selection of global optimal solution was solved by studying the parameter [K,α] about variational mode decomposition (VMD) and simulating physical system annealing， that was simulated annealing variational mode decomposition (SAVMD) extract characteristic value. The intrinsic mode function (IMF) components were reconstructed by weighted kurtosis evaluation index, put them into convolutional neural network (CNN) model for fault classification. Finally, the proposed method was verified by numerical simulations with the open bearing data of Case Western Reserve University. The accuracy rate is 99.28%. After introducing -6 dB white noise to simulate the noisy environment, the accuracy rate is 93.6%. These results show that this method can be used to achieve bearing fault diagnosis in complex working environment.关键词：Bearing fault;Variational mode decomposition;Simulated annealing;Feature extraction;Fault diagnosis
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发布时间：2024-07-05 - 摘要：In order to reveal the vibration characteristics of fault rotor systems caused by the bearing misalignment, the expression of the rotor deflection displacement under the bearing misalignment was derived through the coordinate transformation relation. On this basis, the dynamic model of the double disk rotor system with the coupled bearing misalignment-rub-impact fault, considering the influence of external excitation including the rub-impact force and the oil film force was established. The effects of rotational speed and mass eccentricity on the dynamic response of the system were studied by means of the numerical method. The results show that the bearing misalignment fault can increase the possibility of rub-impact, worsen the shafting vibration and magnify the unsteady motion range of system. Although the addition of misalignment can delay the instability movement induced by parameter changes to a certain extent, the enlargement of amplitude is contrary to the safe operation goal for system, therefore, the necessary measures should be taken to control the bearing misalignment fault. The relevant conclusions can provide useful references for the vibration state identification and the stability analysis of rotor bearing systems.关键词：Rotor-bearing system;Bearing misalignment;Rub-impact;Deflection
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发布时间：2024-07-05 - 摘要：Aiming at the problem that the bearing fault diagnosis algorithm based on deep learning has poor diagnosis performance when the fault samples are lack of labels in different working conditions and real environmentsly, an unsupervised domain adaptive bearing fault diagnosis method was proposed to realize the unsupervised fault diagnosis of bearings under different working conditions. Firstly, the bearing fault sample data was preprocessed by fast Fourier transform and the features of bearing faults samples were extracted using convolutional neural network. Then, the feature distributions output of the source domain and the target domain were converged by the method of reversing labels in the generative adversarial network. Finally, the classifier of the source domain was exploited to complete the bearing fault diagnosis task under different working conditions. In order to verify the effectiveness of the proposed method, relevant comprehensive experiments were carried out on the bearing dataset of Case Western Reserve University of American and the bearing dataset of the University of Paderborn in Germany. The experimental results show that the proposed method can use the unlabeled target domain data to complete the transfer task, and it shows a good transfer performance on the two datasets and achieves a high diagnostic accuracy.关键词：Domain adaptation;Transfer learning;Unsupervised learning;Fault detection;Rotating machinery
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发布时间：2024-07-05 - 摘要：A rotor fault identification method integrating symbolic entropy and evidence theory was proposed for the problem of the difficulty to accurately identify the fault state caused by the nonlinearity and nonstationarity of the rotor vibration signal. Firstly, the fluctuation sequence was obtained by processing the recorded data of the rotor system by de-averaging and difference. Secondly the binary sequence was obtained by binary processing. Thirdly the symbol sequence was obtained by encoding to calculate the symbol entropy. In this paper, the code length in the calculation of symbol entropy was determined by an indicator of the relative growth rate of the mean value of symbol entropy. Through experimental analysis, the symbol entropy of the four channels of the rotor was used as the identification vector, and then compared with the identification standard vector obtained from the historical data to obtain the recognition probability of each state, and finally the results of two tests were fused through D-S evidence theory to obtain the final discriminatory result. Compared with the traditional fault identification method based on symbolic entropy, the proposed method can accurately identify the common states of the rotor system, providing a solution to the rotor fault state identification problem when the vibration signals are in nonlinear and nonstationary conditions.关键词：Rotor;Symbolic entropy;Evidence theory;Fault identification;Relative growth rate
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发布时间：2024-07-05 - 摘要：The mechanical behavior and stability of thin-walled I-beams with honeycombs, concave and elliptic cellular under quasi-static uniaxial compression were studied by experiments and the finite element simulation. By comparing results of experiments and the finite element simulation, the reliability of the finite element simulation was verified. Based on experimental results and finite element simulation results, the maximum bearing capacity, elastic modulus and failure mechanism of thin-walled I-beams with honeycombs were analyzed, and the influence law of the cell type on the compression instability of thin-walled I-beam with honeycombs was obtained. The results show that the larger the distance from the hole to the flange, the better the stability of the structure. The buckling position of thin-walled I-beams with honeycombs with good stability appears between the two holes, and the concave structure has better stability than the honeycomb and elliptical structure.关键词：Cellular beam;Stability;Bearing capacity;Elastic modulus;Instability characteristics
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发布时间：2024-07-05 - 摘要：Crack growth analysis of aircraft fuselage panels is one of the important tasks of aircraft damage tolerance design. In this paper, the crack growth behavior and residual strength characteristics of the internal pressure panel of the aircraft fuselage with longitudinal cracks were analyzed from two aspects: damage tolerance experiment and finite element simulation. A horizontal self-balancing test device was used to apply internal pressure load to the fuselage panel to analyze the damage tolerance characteristics of the panel. Based on the finite element method, the stress field distribution at the crack tip of the fuselage panel under internal pressure load was simulated. And the analysis results of the equivalent stress intensity factor and crack growth of different crack lengths were calculated based on the fracture mechanics theory. The comparison between the crack growth results and the test results validates the feasibility of the analysis method. This serves a as a valuable reference for conducting damage tolerance analysis on aircraft fuselage panels subjected to internal pressure loads.关键词：Crack growth;Damage tolerance;Aircraft internal pressure panel;Stress intensity factor
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发布时间：2024-07-05 - 摘要：The hierarchical multicellular structure exhibits good energy absorption characteristics, which can be widely used in the energy absorption devices of vehicles such as automobiles and airplanes. Two types of self-similar nested metal multi-cellular tubes were designed, the crashworthiness under axial impact was studied by numerical simulation. The results show that higher order multicellular tubes have better energy absorption capacity than lower order multicellular tubes, regardless of the same mass or wall thickness. With the same mass, the specific energy absorption ratio of higher order multi-cellular tubes is up to 36.45% and the crush force efficiency is up to 35. 42%. Under the same wall thickness, the maximum specific energy absorption and crush force efficiency of higher order multicellular tubes are increased respectively by 80.40% and 59.64%. The results show that the crashworthiness of the proposed self-similar nested metal multicellular tube is significantly improved compared with the traditional multicellular tube. Finally, the parametric study of the structural parameters such as order and wall thickness on the crashworthiness of self-similar nested metal multicellular tubes was carried out systematically.关键词：Self-similar structure;Multicellular tube;Axial impact;Numerical simulation;Crashworthiness
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发布时间：2024-07-05 - 摘要：In order to consider the influence of mechanical properties of different at p positions of cylinder head on fatigue assessment, a fatigue assessment method considering the dispersion of mechanical properties of cylinder head was proposed. Firstly, samples were taken from the top plate, bottom plate, intake and exhaust port walls and vertical walls of the cylinder head body, and tensile tests were carried out to analyze the dispersion of mechanical properties of each part. Then, the microstructure characteristics of each area of the cylinder head were measured, and a prediction model of tensile properties based on microscopic defects was established. A fatigue strength prediction model was established by using the relation between tensile properties and fatigue strength. Finally, based on the multi-axial high-cycle fatigue theory, combined with the coupled thermo-mechanical stress and material boundary, a zonal evaluation method for the fatigue strength of the cylinder head was proposed. The results show that the prediction error of the established mechanical performance model is about 2%, which can accurately predict the mechanical performance of each area of the cylinder head. Compared with the traditional fatigue assessment method, the proposed method combined the influence of two factors of working load and material dispersion, and the estimated dangerous position was consistent with the test cracking position, so it can more accurately characterize the fatigue performance of the cylinder head.关键词：Cast aluminum cylinder head;Dispersion of mechanical property;Mechanical property prediction;Fatigue strength;SDAS
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发布时间：2024-07-05 - 摘要：The tensile residual strength is an important mechanical property of composite laminates and plays a key role in the service life of the product. In order to study the influence of drilling process parameters on the tensile residual strength of carbon fiber composite laminates after drilling, Vumat subroutine was written with the selected failure criteria and stiffness degradation mode, and the finite element model of tensile of carbon fiber composite laminates after drilling was established in Abaqus software. The effect of spindle speed, feed rate and bit tip angle on the tensile residual strength of carbon fiber composite laminates after drilling were investigated by the orthogonal test. The results show that spindle speed, feed rate and bit tip angle all have significant effects on the laminate's tensile residual strength. Increasing spindle speed and decreasing feed rate and bit tip angle can effectively improve the laminate tensile residual strength after drilling, which provides a reference for practical processing.
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发布时间：2024-07-05 - 摘要：In order to reduce casualties caused by improperly driven vehicles in maintenance construction zones, this paper proposes an aluminum honeycomb attenuator installed at the rear of road maintenance vehicles. Currently, there is limited research on this type of attenuator. To address this, the paper establishes a high-precision finite element model for the attenuator and utilizes numerical simulation methods to study its collision protection performance from three aspects: energy absorption, directional controllability, and blocking capability. The research results indicate that the aluminum honeycomb attenuator can effectively reduce the impact force and acceleration experienced by occupants during collisions. Additionally, the appropriate strength of the aluminum honeycomb is crucial for enhancing collision protection performance.关键词：Road maintenance vehicle;Attenuator;Numerical simulation;Collision protection performance
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发布时间：2024-07-05 - 摘要：In order to study the crack damage propagation law of rotor blades under complex loads in the actual service of aero-engines, the crack propagation life curve of blades was constructed based on the operational data of aero-engine, and the crack propagation rate formula was established by fracture mechanics theory. Taking the high-pressure compressor blade as an example, the load model of the compressor blade structure was constructed by the fluid-solid coupling method. The Paris， Walker and Newman crack growth rate formulas were used to analyze the three-dimensional crack propagation in the tip region of the compressor blade. The simulation results show that the prediction results of the three crack propagation rate formulas are consistent with the crack propagation curve of the engine operation data in the early stage of crack propagation, which can better describe the crack propagation law of the blade. In the stage of stable crack propagation, the prediction results of Walker and Newman formulas are relatively dangerous, and the prediction results of Paris formula are in good agreement with each other, and can be mutually confirmed with the requirements of damage development control in the manufacturer's technical manual.关键词：Compressor blade;Operation data;Fracture mechanics;Crack growth rate formula;Life prediction
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发布时间：2024-07-05 - 摘要：In view of the problem that large jacquard machine was prone to bending deformation when bearing load, resulting in insufficient lifting height of lifting knife, so that the straight needle hook can not be caught by the electromagnetic device. Firstly, the structure, load and movement of crank slider driving mechanism were analyzed. Secondly, based on the theory of variable cross-section beam and the method of structure optimization, non uniform rational B-splines (NURBS) method was used to express the side and cross-section shape of the lifting knife. Inertia moment function and bending moment function of the lifting knife cross-section were calculated by numerical method, and deflection of the lifting knife was calculated by finite difference method. The deflection calculation method in this paper was verified by the finite element method (FEM) and equivalent beam method with an error of less than 10%. Finally, aiming at the minimum quality, the primal-dual infeasible-interior-point algorithm was used to optimize the lifting knife structure. The optimization result shows that compared with the optimized initial value model, the mass of lifting knife decreases by about 1.7% and the maximum deflection decreases by about 26.67%.关键词：Jacquard machines;Lifting knife;Variable section beam;NURBS method;Bending deformation;Structural optimization
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发布时间：2024-07-05 - 摘要：In order to improve the energy absorption efficiency of the conventional thin-walled square tube, a bionic hierarchical thin-walled square tube (BHST) was proposed by the microscopic trabecular structure of beetle wing sheaths. Based on the super folding element theory, a theoretical model of the mean crushing force of the bionic hierarchical thin-walled square tube was established. The axial energy absorption characteristics of the bionic hierarchical thin-walled square tube and the conventional multi-cell thin-walled square tube were analyzed by the nonlinear finite element method, and the influence of structural parameters on the crashworthiness of BHST4-2 structure was studied. The results show that the theoretical predictions match with the numerical simulation results, and the relative errors are all within 7%. The bionic hierarchical thin-walled square tube exhibits excellent crashworthiness. The wall thickness has a more significant effect on the crashworthiness of BHST4-2structure than the second-order square tube edge length. The radial basis function (RBF) model and the genetic algorithm were used for the multi-objective optimization of the BHST4-2 structure, and optimal al parameters of the structure were obtained. The results of the study provide new ideas for the design of thin-walled square tubes with excellent energy absorption properties.关键词：Bionic hierarchical thin-walled square tube;Super folding element theory;Parameter analysis;Crashworthiness;Multi-objective optimization
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发布时间：2024-07-05 - 摘要：As one of main equipments of coal transportation, the transportation efficiency of train skin has always been the focus of the coal transportation industry. Under the condition of low temperature in winter in northern China, the main reason affecting the transportation efficiency is that the water contained in coal is adhered to the inner surface of the uneven carriage, and gradually diffuses from the surface of the carriage to the inside of the coal, finally, the phenomenon of frozen car causes the equipment to be unable to continue to run. In this paper, firstly, based on the existing problems of different cleaning methods, combined with the actual project, an automatic frozen sticky floating coal cleaning mechanism was designed and its cleaning performance was optimized. Through theoretical research and analysis, the floating coal frozen particle model was established. Secondly, the movement of the disc cutter during the cleaning process was analyzed, and the mechanical model and mathematical model were established. Finally, the multi-body dynamics software RecurDyn was used to simulate the performance of the cleaning drum at the bottom of the cleaning mechanism. The influences of different drum speed, traction speed and cleaning depth on the cleaning performance was solved, and the performance parameter matching scheme with the smallest cleaning retance and the lowest energy consumption was sought by optimization. The results show that the cleaning efficiency of the cleaning mechanism is less affected by the drum speed. With the increase of the drum speed, the cleaning resistance fluctuates within a certain range. As the traction speed continues to increase, the cleaning resistance firstly decreases and then gradually increases; the cleaning depth has the greatest influence on the cleaning resistance. With the increase of the cleaning depth, the cleaning resistance increases continuously. According to the influence law of single factor parameters on the cleaning resistance, the response surface method V was used to simulate the comprehensive influence law in a reasonable range. After the objective function was obtained, the mathematical model was solved by Matlab to obtain the optimal solution. When the drum speed is 78 r/min, the traction speed is 0.05 m/s, and the cleaning depth is 100 mm, the cleaning mechanism has the lowest resistance and the lowest specific energy consumption of 0.22 kWh/m3, and the performance of the cleaning mechanism is optimal.关键词：Cleaning mechanism;Frozen sticky floating coal;Co-simulation;Cleaning performance;Parameter optimization
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发布时间：2024-07-05 - 摘要：Gear is the most commonly used transmission component, and its most common failure mode is tooth surface pitting and tooth root fracture. In order to analyze its reliability quickly and accurately, an improved fourth moment method considering failure correlation was proposed. Firstly, according to the failure mechanism, the reliability models of tooth contact fatigue and tooth root bending fracture failure were established respectively. Secondly, in order to improve the accuracy of the traditional fourth order moment solution, the second order reliability index obtained by the improved first order second moment method was used to obtain the new fourth order reliability index, so as to improve the reliability solution accuracy of single failure mode. Then, the correlation between multiple failure modes and the overall failure probability considering failure correlation were calculated based on the conditional probability dimension reduction method. Finally, taking the transmission gear of a system a a example, the calculation results of the proposed method, mean value first order second moment (MVFOSM) method, advanced first order second moment (AFOSM) method and traditional high-order moment standardization technique (HOMST) method were compared. The results show that the accuracy and efficiency of the proposed method are greatly improved, and it also provides a theoretical method to analyze the reliability of multiple failure modes.关键词：Gear;Fourth order moment;Multiple failure modes;Reliability
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发布时间：2024-07-05 - 摘要：In order to improve the time dependent robust reliability performance of structure and give consideration to the description accuracy of interval variables, a time dependent robust reliability optimization of structure based on genetic interval affine response surface method was proposed. Firstly, the performance reise of structure according to the structural performance analysis method was obtained, and uncertainties of the structure were extracted. Secondly, the parametric analysis model of the structure was established, and design of experiment was carried out. The process of design of experiment was divided into two parts which were design variable database and structural performance response database. Combined with interval affine theory, the initial interval affine response surface was established. On the basis of sample boundary and structural performance analysis results of each variable in the design variable database, the genetic algorithm and criteria for error minimization we were used to optimize the initial interval affine response surface. The structural performance response database was used to verify the effectiveness of new interval affine response surface. Finally, combined with structural with structural performance degradation behaviour and robust reliability optimization method, the time dependent robust reliability optimization model for structure was established and structural optimization design was carried out. The rationality of the proposed method was verified by an engineering example. The analysis results show that genetic interval affine response surface can more reasonably reflect the fluctuation range of structural response, and the proposed optimization method can effectively improve the level of structural robust reliability.关键词：Bogie frame;Robust reliability;Affine response surface;Interval theory;Genetic algorithm
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发布时间：2024-07-05 - 摘要：According to Shanghai road driving cycle, a light-weight design model for gear in driving deceleration system with finite life is developed, in consideration of random continuous loading characteristics and low amplitude load strengthening effect on 20CrMnMo steel. Based on linear damage theory, developed load spectrum and continuous load spectrum with low amplitude load strengthening were implemented to calculate fatigue damage. To minimize gear volume, a light-weight optimization model was established with the constraint of fatigue damage, and differential evolution algorithm was then adopted to solve the model. Experimental results show that the designed model can find the optimal gear parameters quickly and accurately, and the best optimized parameters can be obtained when the continuous load spectrum is used and the low amplitude load strengthening effect is taken into consideration. The optimization model designed in this paper has excellent transferability and can be directly migrate to light-weight optimization of other transmission parts.
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发布时间：2024-07-05 - 摘要：In order to solve the limitation of center distance adjustment and strength distribution of conventional gear, a structure with the same base pitch but different modulus was proposed to greatly improve the strength of small gears in gear transmission, especially the strength of the tooth root. But used in the engineering practice in modulus differ with tooth profile angle are smaller, the formation principle of involute gear tooth surface and the gear meshing analysis of some parameters, got this kind of gear modulus, tooth number, tooth shape parameters such as coefficient of angle, depth of constraints, and through the formula deduction coefficient of the teeth, the tooth depth and the relation between the dividing circle pressure angle limit value. Based on the modeling of engineering practice and the finite element analysis through Ansys, the gear strength designed based on the limit parameters is about 2.66 times of the standard gear, which verifies the feasibility of the theory and expands the application range of this gear pair.关键词：Involute gear;Unequal modulus;Unequal pressure angle;Backlash-free drive;Finite element analysis
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发布时间：2024-07-05 - 摘要：In order to study the structural performance of the new bend-twist coupling blade, NREL 5 MW blade was taken as the prototype, and the geometric model of the blade was established by using NX Open Grip parameterization language. The composite lamination design was carried out in accordance with the real processing technology, and the aerodynamic force of the blade was obtained by the computational fluid dynamics (CFD) method. The bend-twist coupling characteristics, harmonic response and strength of conventional and bending-torsional coupling blades were analyzed respectively. The results show that the blade tip displacement increases with the increase of the web deflection. For the same angle, the blade tip displacement of γ > 0 blades was smaller than that γ < 0 blades. The bend-twist coupling effect is the most obvious when γ = 10° and 15°. Compared with the conventional blade, the second-order displacement responses of bend-twist coupling blades are significantly reduced. The γ = 15° blade can reduce the stress on the surface and has a good load reduction performance.关键词：Wind turbine blade;Parametric;Structural characteristic;Bend-twist coupling;Harmonic response
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发布时间：2024-07-05 - 摘要：In view of the velocity and acceleration discontinuity by lifted object trajectories cannot be directly applied to multi-robot coordination of inverse kinematics problem of the towing system, a inverse kinematic solution strategy based on point-to-point trajectory planning was proposed. Firstly, the kinematic and dynamic model of the system was established, and inverse kinematics of the system were analyzed and different solutions aiming at different situations were given. Secondly, the strategy for solving feasible inverse solution based on point-to-point trajectory planning, and three algebraic programming methods were used to plan the trajectory of lifted objects. The continuity of velocity and acceleration was ensured during the planning process. Finally, the feasibility of the strategy was verified by two simulation examples, and only the quintic polynomial planning method met the tension condition. The research results lay a foundation for the optimal distribution and control of system tension.关键词：Under-constrained;Multi-robot system;Towing system;Point-to-point trajectory planning;Inverse kinematics
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发布时间：2024-07-05 - 摘要：A bending-torsion-axis coupling dynamic model of herringbone tooth planetary gear transmission system under time-varying meshing stiffness, tooth-side clearance and bearing clearance, integrated meshing error and load excitation was established, and the periodic motion and bifurcation of the system were studied. The global bifurcation diagram, load sharing coefficient, phase diagram and time history diagram of the system were obtained by numerical simulation, and the meshing state of the system was identified. The results show that the optimal load distribution effect of the system occurs in the periodic 1 when the vibration of the meshing frequency is low, both the external sp1l and internal rp1l meshing are in the state of complete meshing. With the increase of meshing frequency, the dynamic meshing force and load sharing coefficient of the system increase, and there are Hopf bifurcation, the real-grazing bifurcation and periodic doubling bifurcation in the process of periodic vibration mutual transition.关键词：Herringbone tooth planetary gear;Bifurcation;Load sharing;Dynamics
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发布时间：2024-07-05 - 摘要：In order to obtain the dynamic response characteristics of the main bearing under the starting and stopping conditions of the RV Reducer, taking the main bearing of a certain RV Reducer as the research object, the radial and axial eccentric loads of the bearing were analyzed. On this basis, the multi rigid body dynamics simulation model of bearings was established, and the load, speed and contact parameters were set according to the working conditions, and the effectiveness of the model was verified. The influence law of the starting and deceleration stop working conditions of the main bearing of RV Reducer on the contact force between the bearing roller and the cage and the inner and outer rings was simulated and analyzed. The results show that the contact force between the main bearing roller and the cage of RV Reducer is affected by the starting and stopping working conditions, and the collision is the most intense in the starting and accelerating stage, followed by the stable stage, and the minimum in the deceleration stage. The fluctuation range of the contact force between the roller and the inner ring during the starting acceleration and deceleration stop stages is 1. 5 times that of the smooth operation, which provides a theoretical basis for the study of dynamic characteristics and the life test of the main bearing of RV Reducer.关键词：RV reducer;Main bearing;Dynamic characteristic;Speed;Contact force
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发布时间：2024-07-05 - 摘要：Heat is very important to the rotation accuracy of the spindle, and the accurate calculation of the convection heat transfer coefficient is the premise of obtaining accurate results from the finite element steady-state thermal analysis. In this paper, the convective heat transfer coefficient of the main shaft was optimized by using the lion swarm optimization (LSO) algorithm. Compared with other optimization algorithms such as genetic algorithm, the LSO algorithm has faster convergence speed, higher accuracy, and better global optimal solution. Firstly, the critical point temperature of the spindle system and the thermal elongation of the spindle were measured by using Lion's thermal analysis module. Secondly, the inaccurate but close to real convective heat transfer coefficient value of the main shaft was calculated by empirical formula. Inaccurate convective heat transfer coefficient was led to inaccurate finite element simulation temperature results, so used the lion optimization algorithm to optimize the convective heat transfer coefficient, the convection heat transfer coefficient was regarded as the target value of interest, and the root mean square error between the experimental temperature value and the simulated temperature value was regarded as the fitness function. After 150 generations, the optimal convective heat transfer coefficient with the smallest error was searched. Finally, the finite element steady-state thermal analysis of the spindle system was carried out on the searched optimal convective heat transfer coefficient, and the comparison with the experimental results proved the effectiveness of the proposed method.关键词：Machine tool spindle;Thermal characteristics;Convective heat transfer coefficient;Lion swarm optimization;ANSYS
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发布时间：2024-07-05 - 摘要：Aiming at the problem that the reliability of the hub drive system under the actual load could not be accurately evaluated at the design stage, a method for evaluating reliability which applied in the design stage was proposed. The dynamic fatigue reliability of each gear pair of the hub drive system was calculated by replacing the actual random load with the static load of the rated design load in the method. The fatigue damage and reliability of each gear pair of the wheel hub drive system under the actual load were simulated through Romax Design software, and the feasibility of the method d was verified, which could provide theoretical basis and practical test guidance for the reliability design of wheel drive system.关键词：Hub drive system;Fatigue injuries;Dynamic fatigue reliability;Romax Design fatigue life test
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发布时间：2024-07-05 - 摘要：Aiming at the problem of low interfacial combination strength or even cracking properties of composite coatings on uranium surface, based on the research of interface characteristics of composite coatings, the numerical model was established to study the interface mechanical behavior of coating interface, and effects of deposition temperature, coating material and component size on interfacial mechanical behavior of Al/Ti, Al/Al2O3 composite coatings were discussed. The results indicate that the stress-oscillation behavior occur at the interface of out coating when the deposition temperature exceeds 300 ℃, and which will directly affect the interfacial bonding strength of the composite coatings. Therefore, the deposition temperature of Al/Ti, Al/Al2O3, composite coatings must not exceed 300 ℃ during magnetron sputtering deposition process. Compared with Al/Ti composite coatings, Al/Al2O3 composite coatings can not only improve the adhesion of Al coating and uranium substrate, but also reduce the stress-oscillation at the interface, which will be the main research directions to further improve the corrosion resistance and wear resistance of uranium and uranium alloys.关键词：Uranium component;Composite coating;Deposition temperature;Interfacial stress
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发布时间：2024-07-05 - 摘要：Aiming at the problem of fatigue life prediction of 2A70 aluminum alloy in the full life range, carried out the tensile test of 2A70 aluminum alloy material, low-cycle fatigue test and high-cycle fatigue test under uniaxial tension and compression conditions. Discussed the advantages of life prediction by strain over the full life range. Proposed the strain fatigue full life curve model, and established the strain fatigue full life curve of 2A70 aluminum alloy. Calibrated the parameters of this model and three commonly used models through the test results, compared and analyzed the prediction results of four models. The results show that the life prediction results of the new model proposed in this paper are all within the range of triple error band, the average error and dispersion are small, and the life prediction accuracy is better than the other three models. The new model is more suitable for the fatigue life prediction of 2A70 material under the same strain ratio.关键词：2A70 aluminum alloy;Strain fatigue;Full life range;Life prediction model
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发布时间：2024-07-05 - 摘要：Under the fatigue loading condition, tooth flank fracture, crack source initiated at the subsurface position, is a subsurface fatigue failure. The failure mode is closely related to the local material strength and local stress state at the internal points of teeth. Based on the contact theory and elastic mechanics, a mathematical model for calculating the internal field stress of gear teeth with interfacial friction and the stress intensity with hardness gradient was established, and the risk prediction of gear tooth flank fracture was carried out. The results show that the calculated maximum stress risk position occurs at a certain depth below the tooth surface, which is basically consistent with the representative position of the tooth surface fracture fatigue source. With the increase of the friction coefficient, the internal safety factor of the gear teeth decreases, which indicates that poor interfacial lubrication can easily lead to the accelerated initiation of internal cracks in the gear teeth, resulting in the fracture fatigue failure of the tooth surface. The risk prediction model provides basic technical guarantee and support for the design and manufacture of tooth flank fracture resistance.关键词：Gear;Tooth flank fracture;Friction effect;Risk analysis
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发布时间：2024-07-05 - 摘要：Bio-inspired multi-cell thin-walled structure has the advantages of light quality and strong impact resistance. The bio-inspired structures design of lotus root and horsetail were coupled with a thin-walled hollow tube, and two novel bio-inspired multi-cell structures were proposed. One was the coupling structure of thin-walled hollow tube and lotus root (LR-IS) , and the other was the coupling structure of thin-walled hollow tube, lotus root and horsetail (LR-HS-IS) . The models were built by Pro/E and imported into the finite element software Abaqus for numerical simulation analysis. In addition, the 3D printing molding technology was used to make the structures. The mechanical behavior and energy absorption characteristics under axial impact of drop hammer impact test and finite element numerical simulation were studied. The results show that the bio-inspired multi-cell structures have good energy absorption effect, significantly improve the carrying capacity, load efficiency and specific energy absorption. Compared with the individual thin-walled hollow tube, the bio-inspired multi-cell thin-walled structures can not only significantly reduce the impact effect, but also the initial peak force is relatively stable. In addition, the structures are also very consistent with the requirements of lightweight and high energy absorption.关键词：Bionic engineering;Finite element simulation;Experiment;Energy absorption;Impact resistance
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发布时间：2024-07-05 - 摘要：The concave-convex die plays an important role in the metal plate bending process, and the fillet radius of the concave-convex die is a key parameter in the design of the bending process. Due to the delamination damage of the single-layer metal plate during the bending process of the multilayer metal plate, this paper mainly studied the influence of the concave-convex die on the damage of the multilayer metal plate during the bending process, and the test was carried out by changing the corresponding die parameters and verified by finite element simulation. The results show that delamination damage occurs in the bending process of the multi layer metal plate. Without changing the punch, the degree of delamination damage will gradually decrease with the increase of the fillet radius of the die, and the bending effect of the multilayer metal plate is better. At the same time, it is found that when the fillet radius of the concave die is equal to the sum of the fillet radius of the punch and the thickness of the metal plate, the bending performance of the multilayer metal plate is the best, and there is basically no delamination damage.关键词：Concave-convex die;Fillet radius;Multi layer metal plate;Bending process;Delamination damage
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发布时间：2024-07-05
- 摘要：In order to study the carrying capacity of the cylinder joint in the mechanical structure, based on Hertz contact theory and combined with the modified three-dimensional fractal theory, the three-dimensional fractal theory was applied to simulate the actual engineering joint surface, and a three-dimensional fractal model of the contact stress of the cylinder joint was established under the comprehensive consideration of the macroscopic characteristics and the microscopic morphology factors. And a comparative analysis was conducted with the Hertz contact model, proving the rationality of the established model. Through Matlab simulation analysis, from the macro characteristics, the contact stress can be reduced and the carrying capacity can be improved by using the form of internal contact cylinder joint or by increasing the radius of the cylinder. From the aspect of microscopic morphology, the contact stress can be reduced by reducing the fractal dimension parameter and the material characteristic parameter. The influence of the fractal dimension of the micro-topography parameter on the contact stress is complex. When 2. 1 ≤ D ≤2.5, increasing the fractal dimension can reduce the contact stress. When 2.5 ≤ D ≤ 2. 9, reducing the fractal dimension can reduce the contact stress.关键词：Cylinder joint;Three-dimensional fractal theory;Contact stress;Carrying capacity
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发布时间：2024-10-15
Design·Calculation
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