最新刊期
期 5 ， 2023
- 摘要：To accurately characterize the different operating states of the rotor system, a modified variational mode decomposition（MVMD） combined with instantaneous energy distribution permutation entropy（IEDPE） is proposed to quantify and extract rotor fault features. The parameters of the variational mode decomposition（VMD） decomposition layer are determined using correlation threshold strategy and the MVMD algorithm is designed. Then, the acquired vibration signals are input into the MVMD for decomposition and the instantaneous energy distribution of each mode component is calculated. Finally, the IEDPE of each mode component is extracted as the fault quantization feature. Compared with MVMD+PE, EMD+IEDPE, and EEMD+IEDPE, the results show that the fault features extracted by the proposed method are more effective in characterizing significant differences between rotor fault states, allowing more accurate recognition of fault categories.关键词：Feature extraction;Variational mode decomposition;Instantaneous energy distribution;Permutation entropy;Rotor fault
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发布时间：2023-11-16 - 摘要：To study the association relationship between amplitude jumps and tooth meshing impact in a gear transmission system with backlash, the dynamic equations of amplitude-frequency characteristics of a single gear system are established by the method of harmonic balance. The equation is solved by the quasi-Newton Broyden rank-2 method and pseudo-arc-length continuation algorithm, and then, the two-dimensional domain boundary solution structure of amplitude-frequency characteristics is obtained. The multi-valued solution and tooth surface impact characteristics of the system in the parameter domain boundary structure of the backlash, static comprehensive error, time-varying meshing stiffness, damping, and frequency are analyzed, respectively. The effects of parameters on amplitude jump, multi-value solution, and tooth surface impact characteristics of the system are investigated. The analysis shows that the amplitude jump response of the system appears near the resonance frequency. The nonlinear jump also appears at the non-clearance bearing supports due to the effect of the gear backlash. When b＞1.55, the backlash is not sensitive to the system multi-value solution and tooth surface impact characteristics. The multi-value solution and tooth surface impact characteristics of the system are exacerbated by the increase of the meshing stiffness and the static comprehensive error. Damping can effectively suppress the system amplitude jump and tooth surface impact characteristics, when ξ＞ 0.3, the system shows linear characteristics.关键词：Single-stage gear sets;Two-parameter plane;Harmonic balance method;Tooth surface impact;Dynamic characteristics
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发布时间：2023-11-16 - 摘要：In order to study the effects of parameter approximation and modeling errors caused by lack of cognition on the natural frequency of a single-rotor system respectively, the Riccati transfer matrix method and non-parametric method was applicated to calculate the natural frequency of the rotor system with uncertainty. The contribution of various parameter uncertainties such as support stiffness, shaft length, joint mass and elastic modulus and model uncertainty to the natural frequency of rotor system was analyzed. The results show that for the natural frequency of the uncertain rotor system, the influence range of model uncertainty and parameter uncertainty is quite different, and the magnitude of the fluctuation caused by the uncertainty of different parameters is also different. The research has theoretical reference for the study of uncertain dynamics of steady-state and transient unbalanced responses.关键词：Riccati transfer matrix method;Non-parametric method;Model uncertainty;Parameter uncertainty;Natural frequency
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发布时间：2023-11-16 - 摘要：To study the contact effect of the rotor system with curvic couplings under rolling bearing supports, the combination of 3D finite element and analytical method were used to derive the curvic coupling shaft section stiffness matrix, and the dynamics model of rotor-rolling bearing system was established, which was verified by Ansys. By comparing with the continuous rotor, it was found that the curvic coupling structure reduced the first-order critical rotor speed by 5% and increased the amplitude by 3%. The results show that the nonlinear bifurcation trend of the curvic coupling rotor is nearly the same as that of the continuous rotor, however, the discontinuous characteristic of the curvic coupling structure will make the rotor access or leave the periodic motion state significantly earlier. Obviously, the contact effect needs to be considered when analyzing the rotor vibration characteristics with curvic couplings. The research can provide analysis methods and design ideas for the prediction of nonlinear vibration characteristics and the operating speed design for rotor system with curvic coupling structure.关键词：Rotor system;Curvic coupling structure;Rolling bearing;Nonlinear dynamics;Contact effect
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发布时间：2023-11-16 - 摘要：In order to detect abnormal wind turbine generator and reduce the occurrence of outages, a deep learning framework combining K-CNN and N-GRU is proposed based on multi-dimensional sensor parameters recorded in real wind farm SCADA system, and a wind turbine generator state prediction model is established. Firstly, the correlation of state parameters was analyzed by Pearson correlation coefficient, and then the one-dimensional fusion parameters were weighted by weight coefficient. Secondly, to solve the problem of ignoring shallow features in traditional feature extraction, CNN was used to extract the features of one-dimensional fusion parameters in layers, and KPCA was used to reduce the feature extraction results of different layers to one dimension. Then, to solve the problem of parameter optimization of the traditional GRU algorithm, the neural network architecture search was used to improve the GRU algorithm, and the N-GRU model was obtained. The feature extraction results after dimensionality reduction were input into N-GRU for prediction and reconstruction error was obtained, then the state evaluation was realized by setting the alarm threshold. Finally, a 2 MW wind turbine in a wind farm in Xinjiang was taken as an example to verify the model validity and model accuracy.关键词：Pearson correlation coefficient;CNN stratified feature extraction;Kernel principal component analysis;N-GRU model;Reconstruction error
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发布时间：2023-11-16 - 摘要：Tooth surface pitting is one of the main faults of helical gear. A large number of experimental data are needed for the diagnosis of pitting corrosion faults on different tooth surfaces and different degrees. Therefore, a method combining simulation and experiment is proposed to identify the degree and quantity of pitting corrosion on helical gear tooth surface. The envelope spectrum analysis of dynamic response signals is carried out, and the characteristic response laws of different pitting fault types in time domain and frequency domain are obtained. Through the characteristic analysis of the vibration signal of gear contact fatigue experiment, the accuracy of the dynamic model of helical gear pitting corrosion fault is verified. The results show that the gear pitting fault dynamic model can diagnose and identify the pitting corrosion degree of single tooth surface and multi tooth surface, and provide a diagnostic basis for transmission gear fault diagnosis and health prediction.关键词：Helical gear;Tooth surface pitting;Dynamic simulation;Fault diagnosis
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发布时间：2023-11-16 - 摘要：Staddle monorail use rigid catenary, which often produce strong rigid vibrations and violent fluctuations in contact forces affecting pantograph receiving quality and service life during operation. Therefore, a semi-active control method for staddle monorail′s pantograph with sliding mode variable structure is proposed. The pantograph model with two lumped masses and magneto rheological damping are selected as the research object and the operating mechanism respectively. Firstly, the coupling relationship of the staddle monorail′s pantograph-catenary system is studied and the dynamics equations are derived. Secondly, with the support of the above theory, the active control system for pantograph is built by Simulink simulation method combined with sliding mode variable structure control. Finally, the reverse model of magneto rheological damper is established to realize semi-active control for pantograph. When magneto rheological damper receives the control signal transmitted by the controller, it outputs the desired control force by adjusting the current and finally acts on the pantograph, effectively solving the problem of violent fluctuation of contact force. The experimental results show that the proposed method is more accurate to control the contact force of the pantograph-catenary system, significantly reduces the standard deviation of the contact force by more than 17.34%, and avoids the occurrence of the offline situation of the pantograph-catenary system. The stability and superiority of the proposed method in improving the current quality of the pantograph-catenary system and prolongating the service life of the pantograph are verified.关键词：Pantograph;Sliding mode variable structure control;Semi-active control;Magneto rheological damper
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发布时间：2023-11-16 - 摘要：A type of single-degree-of-freedom mechanical impact vibration system with dry friction and nonlinear constraints is studied. Through the fourth-order variable step Runge-Kutta numerical algorithm, the dynamics of the mechanical vibration system generated by the low-frequency excitation of the p/1 periodic motion are analyzed. The effect of system parameters on the dynamic characteristics of the vibration model is analyzed by the method of multi-parameter co-simulation, and the frequency hysteresis characteristics of Grazing bifurcation and Saddle-node in p/1 periodic motion are revealed. And the range of coexistence attractors. Finally, combined with the cell mapping method, the distribution of different attractors and attracting domains in the polymorphic coexistence area and their transition laws are studied. The research results show that the Grazing bifurcation with the decrease of the excitation frequency, the number of collisions of the p/1 periodic motion will gradually increase until the flutter motion occurs, and due to the irreversibility of adjacent periodic motion, changing different initial values in the hysteresis domain will result in different periodic motions coexisting.关键词：Chattering-impact motion;Non-linear constraints;Bifurcation;Attractors coexistence;Multi-parameter coordination
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发布时间：2023-11-16 - 摘要：Safety protection design is a key problem to be considered in structural design. The study on mechanical characteristics of rolling lobe air spring（RLAS） under the extreme working condition lays an important foundation for its safety protection design. Considering the influence of outer diameter of rubber bellows along with the height of air spring, taking the radius of arc segment and inner cone angle of linear segment as the key design parameters, a novel mechanical model of rolling lobe air spring with safety protection design is established. The experimental results show that the maximum relative error of structural parameters of rolling lobe air spring is 11.9%, the relative error of static stiffness under different pressure in the extreme condition is less than 11% and the maximum relative error of load capacity is less than 6%, which all proves the correctness of mechanical model of RLAS. Force gain and stiffness gain are further proposed as quantitative characterization indexes of safety protection design, and the influence laws of key design parameters on mechanical characteristics and quantitative characterization indexes of rolling lob air spring under extreme condition are explored. The research results provide theoretical support for accurate calculation of safety protection capability of RLAS in the design stage.关键词：Rolling lobe air spring;Composite curved profile;Safety protection design;Mechanical characteristic;Extreme working condition
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发布时间：2023-11-16 - 摘要：Additive thin-walled parts have the characteristics of complex features and weak rigidity, which are prone to processing chatter vibration during the subsequent local feature milling and finishing. Therefore, this paper designed an electromagnetic magnetorheological damping fixture to semi-actively suppress processing vibration and improve processing quality. By simplifying the thin-walled part of the additive into a rectangular thin plate, considering the magneto-rheological fluid（MRF） excitation solidification damping characteristics, using the mode superposition method, the dynamic response model of the milling of the thin-walled part under the change of the magnetic induction intensity was obtained, and the fixture-workpiece system milling. The maximum error between the predicted value of dynamic response and the measured value is 21.4%. The feasibility and effectiveness of the method were verified through modal hammer percussion experiments and milling experiments, and the matching relationship between milling force, process parameters and magnetic induction intensity was fitted. Finally, the processing quality test of the typical samples was carried out. The processing flatness and roughness are increased by 80.0% and 80.3% respectively. The electromagnetic magneto-rheological damping fixture can effectively suppress the milling chatter, improve the processing stability of thin-walled parts, and improve the surface processing of the workpiece quality.关键词：Additive thin-walled part;Flutter suppression;Dynamic response;Electromagnetic magneto rheological damping fixture;Milling
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发布时间：2023-11-16 - 摘要：Aiming at the problems of easy introduction of chemical element residues, micro scratches and low material removal rate in contact chemical mechanical polishing and non-contact plasma polishing processes of single-crystal silicon, a non-contact green polishing method of plasma cavitation stripping for single-crystal silicon is proposed. In the water-based working fluid medium with pulse voltage more than 100 V, the high impedance state isolation vapor layer breaks down due to the small curvature convergence of electron flux and induces an oxygen plasma channel. The convex position of the micro-region on the surface of the anode single crystal Si generates an SiO2 loose film due to the enhancement of the anode chemical reaction by the oxygen plasma. During the pulse intermission period, the plasma channel collapses due to the cold shock liquefaction of the water-based working fluid medium near the wall surface, and cavitation micro-jet impact force is formed at the same time to strip the loose film on a nano scale. After treating the sample for a certain time, the surface roughness of the sample can reach 1.54 nm, and no new chemical elements will be introduced into the surface of the sample. It provides a green non-contact method for plane/non-plane ultra-precision machining of brittle and hard materials.关键词：Discharge mechanism;Plasma;Removing mechanism;Parameter control;Single-crystal silicon
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发布时间：2023-11-16 - 摘要：In this study, CoCrFe-based alloys reinforced by W（0 wt%, 4 wt%, 8 wt% and 12 wt%） were prepared by powder metallurgy, and the tribological properties of the alloys under seawater environment were systematically studied. The friction and wear behavior of the alloy under different loads and sliding speeds in seawater was studied using a reciprocating ball-on-disk friction and wear tester sliding against with GCr15 steel ball; X-ray diffractometer, scanning electron microscope and energy dispersive x-ray analyzer were used to analyze the phase composition and wear mechanisms of the alloys. The results show that the CoCrFeW alloy is composed of ε（hcp）, γ（fcc）, Fe-Cr and Cr2O3 phases. The alloy structure was compact, and the hardness and density increased with the increase of W content. Generally speaking, the friction coefficients of the alloy showed a decreasing trend with the increase of sliding speed and load, and increased first and then decreased with the increase of W content under high-speed conditions. Under high load conditions, the friction coefficients of W-added specimens first decreased and then increased with the increase of W content. The wear rates decreased with the increase of sliding speed, load and W content. Seawater component reaction products and alloy corrosion products had friction-reducing and antiwear action. W significantly improved the wear resistance of the alloy in seawater environment, and the specimen CW8 with 8 wt%W added showed the best tribological performance. As the W content increased, the alloy wear mechanisms changed from plastic deformation and fatigue wear to abrasive wear.关键词：CoCrFeW alloy;Seawater;Friction;Wear
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发布时间：2023-11-16 - 摘要：Due to long-term alternating load, engineering thin-walled structures will produce fatigue cracks, and most of them are penetrative cracks, which will lead to difficult repair and irreplaceable problems in engineering. Therefore, a coating technology is proposed to repair and crack arrest thin-walled structures. Thin plate test pieces related to practical engineering were made, and cracks were preset. The test piece was going to be subjected to the first-order bending resonance state and the excitation test with the foundation excitation of 10g on the vibration test bench until cracks appear. Two kinds of coatings, NiCrAl coating and NiCrAl transition layer + ZrO2 functional layer composite coating, were applied to the test piece by double-sided spraying method to repair the crack, and the excitation test was repeated. Comparing the crack propagation time and propagation rate of the test piece before and after coating, the influence of NiCrAl coating and ZrO2 coating on the crack propagation of the thin-walled plate test piece was analyzed. The crack arrest effect of the coating on the thin-walled plate is verified.关键词：Thin wall shell structure;Coating;Crack repair;Coating crack arrest;Excitation test
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发布时间：2023-11-16 - 摘要：To resolve the poor universality and low accuracy of the existing surrogate models for reliability analysis, a hybrid surrogate model based on radial basis function（RBF） and sparse polynomial chaotic expansion（SPCE） was proposed. It realized rapid and accurate prediction of performance functions to improve the engineering applicability and the accuracy of structural reliability analysis. Importantly, the orthogonal matching pursuit technology was applied to obtain the important terms in PCE, and an SPCE model could be established directly to form the RBF-SPCE model for improving the prediction accuracy of surrogate model. Subsequently, the reliability analysis of complex structures is carried out based on Monte Carlo simulation（MCS）. In this work, three simulation cases were implemented to compare the performance of the proposed method with the traditional RBF model and augmented RBF model. The results illustrated that the proposed method has higher accuracy and efficiency for structural reliability analysis. Finally, a vehicle side impact engineering example illustrated that the proposed method has good engineering applicability for complex problems.关键词：Radial basis function;Sparse polynomial chaotic expansion;Hybrid surrogate model;Reliability analysis;Computational efficiency
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发布时间：2023-11-16 - 摘要：For improving the machining quality and wear-resistance of intelligent numerically-controlled（NC） machine technology, and decreasing the production cost, an adaptive quantum particle swarm optimization method for machining parameters was proposed. Particle swarm optimization（PSO） method and improved Elman network are combined to solve the nonlinear and multi-constraint problems of multi-objective NC cutting parameter optimization. Then, quantum mechanism is introduced into PSO algorithm to adjust the fitness through adaptive inertia weight, and the network training is completed by using adaptive momentum back-propagation method. In the process of network learning, the optimal NC cutting parameters are obtained. A KMC800SU five-axis vertical NC machine tool was used to complete the comparison experiment under Matlab 2021a. Taking the surface roughness as an example, the roughing and finishing machining energy of the workpiece obtained by the proposed method can reach 7.6 μm and 3.5 μm respectively, while the PSO method can only reach 8.6 μm and 3.9 μm separately. The results show that the parameter matching of the proposed method is more reasonable than that of the PSO method, and it can achieve stable and better surface roughness, tool wear and average maximum completion time in less iterations.关键词：Cutting;Quantum mechanism;Inertial weight;Neural network;PSO method
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发布时间：2023-11-16 - 摘要：The distribution of failures is crucial in reliability engineering, and the applicability of a single distribution is limited. In complex systems, a mixture distribution is more appropriate. This article introduces the 3CAW distribution, which provides a more flexible failure rate function, especially a bathtub-shaped failure rate with a long constant region, which is suitable for more complex systems. This article discusses the use of maximum likelihood estimation to estimate the unknown parameters of the 3CAW distribution, and calculate reliability and failure rate as reliability indicators. The cross-entropy method is used to find the global optimum of the logarithmic likelihood function and compare it with single distributions such as the Weibull distribution. The results show that although the model is complex, it has the highest logarithmic likelihood function value and the highest fitting accuracy. The cross-entropy method reduces the difficulty of parameter estimation, making it worth further promotion in engineering practice.关键词：Reliability;Three-component additive Weibull distribution;Cross entropy method
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发布时间：2023-11-16 - 摘要：The vertical well inclinometer is widely used in downhole data measurement, wherein the mud pulse generator used for data transmission has substantial significance to the accuracy and stability of data. For this instrument, the performance of its mud pulse generator valve head is the key to ensure the efficient, accurate and complete transmission of downhole data. Firstly, the structure of pulse generator in the vertical well inclinometer is described, followed by the presentation of the physical and theoretical model of pulse generator valve head. Based on the erosion theories and thin-wall hole throttling model, the main parameters that affect the performance of pulse generator valve head are determined, including the throttling hole slot angle α and the valve head angle β. Secondly, with using the discrete phase model（DPM）, the influences of throttle slot angle α and valve head angle β on the flow field characteristics near the valve head and the pressure distribution of the valve head are investigated. In terms of the simulation, an optimized parameter set of the valve head is α=25°and β=45°. Finally, valve heads with optimized parameters are tested in a certain well of Dixi, showing a good accuracy with the numerical simulation with comparing the results before optimization.关键词：Vertical well inclinometer;Pulse generator;Valve head;Discrete phase model（DPM）;Flow Field
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发布时间：2023-11-16 - 摘要：The service life of the planetary reducer in a hub drive system largely depends on the system reliability design. Aimed at the problems of lower credibility and inadequate depth in the reliability allocation, based on improved FMECA formulas and order statistics theory, an advanced reliability allocation method of the planetary reducer is proposed. The basic characteristics of the planetary reducer are analyzed, and FMECA formulas with the positive failure correlation modifying operator are presented, which indicate that the subsystem complexity and the failure occurrence change in the same direction as the failure correlation degree, respectively. Simultaneously, based on the Gumbel Copula function and order statistics theory, the reliability allocation model is established to assign reliability design indices to parts of the planetary reducer. By comparing the subsystem reliability allocation weights obtained by different methods, results show that the allocation result of the proposed method is more credible. It will be helpful to accomplish the deeper reliability allocation and improve the service life of the planetary reducer.关键词：Integrated factors allocation method;Planetary reducer;Reliability allocation;Positive failure correlation;Modifying operator;Order statistics
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发布时间：2023-11-16 - 摘要：The research on the excavation resistance function of excavator is the key step to realize automatic excavation. Based on the classical soil-bucket model, a digging resistance model of automatic excavator is proposed. The expression of the excavation resistance function for the whole automatic excavation process of three stages of penetration, cutting and loading and the detailed calculation process of its coefficients are given. The existing bucket shape model is modified to make it more in line with the actual shape. Taking a certain excavation track and silty clay as examples, the theoretical excavation resistance curve under this working condition is calculated and compared with the results obtained by Ls-Prepost software simulation. The shape of the two curves is similar, and the maximum error is less than 10.2%, the results show that the resistance model can be used as the excitation function of excavator dynamic performance analysis. It has a good reference value to the dynamic performance research of automatic excavator.关键词：Automatic excavator;Excavation resistance function;Vibration excitation function;Excavator vibration
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发布时间：2023-11-16 - 摘要：To improve the ride comfort of a light commercial vehicle, the dynamic performance of the hybrid air suspension was analyzed and optimizaed by multi-body dynamics. Through the quasi-static compression test, the dynamic model of the air spring under different air pressures was established, and then the dynamic performance of the vehicle under random and pulse input were studied through the multi-body dynamics simulation. A combined model for ride comfort simulation was established ob basis of Isight, Matlab and Adams/Car. Through performing the sensitivity analysis, the parameters that have a great impact on the ride comfort performance were determined. Finally, the ride comfort of the whole vehicle under random and impulse input is optimized through the Co-simulation platform and NSGA-Ⅱ optimization algorithm. The simulation results of ride comfort after optimization show that: under random input, the root mean square value of weighted acceleration at the driver is reduced by 13.6%, and that at the passenger is reduced by 25.6%; under pulse input, the maximum vertical acceleration at the driver is reduced by 15.9%, and that at the passenger is reduced by 29.4%, and the ride comfort of the whole vehicle is significantly improved.关键词：Air suspension;Ride comfort;Co-simulation;Sensitivity analysis;Optimization algorithm
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发布时间：2023-11-16 - 摘要：To optimize the structural strength of the soft-sealing ball valve seat at ultra-low temperature, a design method combining response surface method and genetic algorithm was proposed, which took the maximum equivalent stress as the optimization objective. The stress-strain relationship of PCTFE, the material of low-temperature ball valve seat, under different working conditions was studied, and the tensile strength is the only important basis to judge the strength of PCTFE. The central combination design method was adopted, established the response surface model of stress on structural parameters, analyzed the interaction between parameters. The optimal structural parameters of valve seat were obtained based on response face combined with genetic algorithm. The results show that the maximum equivalent stress of valve seat decreases with the increase of valve seat thickness and inner and outer diameter of valve seat sealing face. The inner diameter of sealing face of valve seat has the most significant effect on the maximum equivalent stress.关键词：PCTFE;Parameter optimization;Response surface method;Genetic algorithm
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发布时间：2023-11-16 - 摘要：Combining the topology optimization of crashworthiness results and the shear squeezing energy absorption idea, this paper proposes a re-directive crash cushion with a shear and extrusion expansion mixed energy absorption type, and then based on the robust design method to obtain its optimal structural parameters. Firstly, according to topology optimization of crashworthiness for obtaining the best force transmission path. Secondly, the energy absorption types of shearing and extrusion expansionare mixed and then integrated into the design of the crash cushion to propose a basic configuration of the re-directive crash cushion with a shearing and extrusion expansion mixed energy absorption type. The results indicate that the re-directive crash cushion with a shearing and extrusion expansion mixed energy absorption type can provide better protection for crash vehicles and occupants.关键词：Shearing;Extrusion expansion;Topology optimization;Robustness;Re-directive crash cush
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发布时间：2023-11-16 - 摘要：Aiming at the problem of aggravated wear of coiled tubing caused by buckling in underground, a contact wear model between compression buckling coiled tubing and wellbore was established based on submodel method. Archard model was introduced to calculate the wear depth of coiled tubing. The removal process of material on the surface of coiled tubing was described by moving contact boundary node method to avoid mesh distortion.The wear of various compressive loads and annulus clearance are predicted.The results show that the coiled tubing is subjected to sinusoidal buckling and the wear parts are few, and the compression load and annular clearance have little influence on the wear of the coiled tubing.There are many and continuous wear parts in coiled tubing with spiral buckling, and the compression load and annulus clearance have great influence on the wear of coiled tubing This paper provides a calculation method for quantitative prediction of wear of buckling coiled tubing in wellbore.关键词：Sinusoidal buckling;Helical buckling;Archard model;Finite element analysis;Wear prediction
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发布时间：2023-11-16 - 摘要：In order to facilitate the selection of basic parameters in the initial design stage of face gear, and simplify the process of solving meshing strength of face gear pair. By referring to the existing strength calculation formula of the standard spur gear, the analytical calculation models of contact stress and bending stress of full tooth height of face gear were established. The curvature of tooth surface was solved by the basic parameters of the gear, and the contact stress of tooth surface was solved by the Hertz contact theory. The tooth thickness at the dangerous section of gear teeth was determined by the 30° tangent method, and the stress calculation coefficient table was given based on the expression of basic parameters of gear pair, finally, the analytical calculation formula of tooth root bending stress was deduced. Taking face gear pair with a certain design parameter as an example, the results obtained from the analytical calculation models were compared with those from the finite element simulation to verify the accuracy of models. On this basis, a simplified formula for calculating the strength of face gear was given which can be directly solved by the basic parameters of gear.关键词：Face gear;Contact stress;Bending stress;Finite element
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发布时间：2023-11-16 - 摘要：As an important part of the bionic robotic fish, lightweight design of the frame mechanism was an effective way to improve the efficiency of bionic robotic fish propulsion. The frame and tail swing three-dimensional solid model of virtual bionic robotic fish were constructed on the three-dimensional design platform. Based on flapping wing theory, the mechanical characteristics of the tail fin of bionic robotic fish in motion were analyzed, and the instantaneous load was obtained by numerical simulation method. The caudal fin mechanism was introduced into ADAMS environment for dynamic analysis, and the motion load of the bionic robotic fish frame mechanism was obtained. Using the transient simulation of bionic robot fish frame, the real-time dynamic mechanical characteristics of bionic robotic fish were studied. Based on topology optimization, the key areas of the bionic robotic fish frame are lightweight designed. The results show that the equivalent stress, equivalent strain, total deformation and mass are reduced by 12%, 16%, 5.3% and 10.69% respectively. The lightweight design method of bionic robotic fish frame improves the maneuverability of bionic robotic fish and provides a reliable theoretical basis for the design and research of bionic robotic fish.关键词：Bionic robotic fish;Flapping wing theory;Dynamics analysis;Lightweight design
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发布时间：2023-11-16 - 摘要：To explore the effect of the tooth profile modification of the flexible gear on the meshing performance of the harmonic reducer, an assembly model of the hollow harmonic reducer was established, and the meshing situation of the flexible gear and the rigid gear was analyzed by the finite element method. The equivalent deformation and equivalent stress of the double-arc tooth profile in the no-load and load process are used as the comparison conditions. Comprehensively consider the amount of flexible gear tooth profile tooth tip modification, and adjust the tooth height inclination of the flexible gear tooth profile axis at the same time, and calculate the equivalent deformation stress after the tooth profile modification under the same boundary conditions. The comparison results show that the neutral layer curves of the front and rear edges of the flexible gear tooth are extracted under no-load and load conditions. The equivalent deformation of the flexible gear is basically unchanged, but the maximum equivalent stress is reduced to 80% and 76.6% respectively, and the meshing performance is improved. Related researches provide useful attempts and references for the design, evaluation and transmission performance optimization of harmonic reducers.关键词：Harmonic reducer;Flexible gear;Meshing performance;Tooth profile modification;Finite element method
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发布时间：2023-11-16 - 摘要：Fused Deposition Modeling（FDM） has the advantages of fast forming speed and simple operation. Printing speed, printing layer thickness and printing temperature affect the equivalent stress of the workpieces, and then affect its mechanical properties. It is different from direct setting printing temperature as the initial temperature in the birth and death unit simulation. Through experiment and fluid simulation, the temperature of the single fuse when it contacts the plate is got, as the initial temperature of the multilayer superposition simulation. We calculate and fit out the function of heat transfer coefficient, considering printing parameters. With the FDM Multi Layer Stacking simulation, the stress of the workpieces under different parameters is got. Then correlated and compared with the tensile strength obtained by the tensile test under the same parameters. From the point of the stress, we analyzed the influence of the printing parameters on the tensile strength. The supplementary experiment is designed, and find the tensile strength of ploylactic acid（PLA） workpieces reach the maximum when the printing layer thickness is as far as small, the printing speed and the printing temperature are appropriate.关键词：FDM;Equivalent stress;Heat transfer coefficient;Tensile strength
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发布时间：2023-11-16 - 摘要：To explore the effect of low load strengthening on the fatigue life of parts under random load, the automobile stabilizer bar is taken as an example, and the collected random load signal is extrapolated to the whole life cycle by peak over threshold extrapolation method. Based on the extrapolated load signal, the distribution characteristics of its mean and amplitude are analyzed, and the two-dimensional joint probability distribution is established. According to the characteristic that the stabilizer bar is continuously subjected to complex random loads, the influence of mean and amplitude is considered to compile the two-dimensional load spectrum, and the low load strengthening theory is introduced. The life prediction based on linear fatigue cumulative damage theory（Miner rule） and low load strengthening theory is compared with the test results to verify the effectiveness and accuracy of life prediction based on low load strengthening under random load.关键词：Random load;Peak over threshold extrapolation;Low load strengthening;Life prediction
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发布时间：2023-11-16 - 摘要：Engine, internal combustion engine, steam turbine rotors and other high-temperature components were often subjected to high and low cycle composite fatigue loads during operation. A new method by the curves of strain ratio(εHCF/εLCF)-life ratio(NLCF/HCF/NLCF) to predict the life of high and low cycle composite fatigue was advanced. The analysis of experimental data of three different materials showed that this method had certain versatility. The estimated values of life were within the error tolerance range by comparing the life estimation value with the experimental results, indicating that this method can better predict the life of high and low cycle composite fatigue for high temperature equipment materials.关键词：High temperature equipment materials;High and low cycle composite fatigue loads;New method to predict the life
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发布时间：2023-11-16 - 摘要：To analyze the fatigue fracture causes of boom during normally working service, the boom bench fatigue test scheme was proposed. The measured joints multi-load was equivalent to a uniaxial load based on the fatigue damage consistent principle. Moreover, the calculated fatigue damage caused by the equivalent uniaxial load is in the same order of magnitude as the measured damage of each boom fatigue key point, and the relative error is within 8%. The full-scale accelerated loading fatigue test of four large and medium-sized excavator′s boom was carried out under the accelerated 5-level program loading spectrum compiled from the equivalent uniaxial load. The fatigue fracture surface was analyzed by scanning electron microscope. The results show that the boom fatigue life is relatively discrete, and the fatigue crack originates from the stress concentration point caused by welding defects such as incomplete penetration, incomplete fusion and gas porosity. After targeted improvements to the weld structural details of a boom based on bench test results, its fatigue life is increased by at least 1.5 times. The predicted life of commonly used international welding standards, BS7608-2015, IIW2008 and AWS-2015, is relatively close to the bench fatigue test results of the 2nd and the 3th boom, while the predicted life of standard EN-2005 is longer. With the bench fatigue test, the fatigue strength weak parts of booms and other similar structures can be effectively inspected, which provides a valuable reference for structural improvement.关键词：Excavator;Boom;Full-scale accelerated loading test;Fatigue fracture;Welding defects
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发布时间：2023-11-16 - 摘要：In view of the contact fatigue problem of the wheel side reducer gear of the drive axle of the loader during its service, the fatigue life was evaluated. Finite element models of the sun wheel and the planet wheel were established in Hypermesh. Statics and transient dynamics were solved in Ansys Workbench according to the fatigue loading spectrum. The fatigue life was calculated in Ncode environment based on statics and transient dynamics. The fatigue life calculated based on finite element was compared with the bench test results. The results show that the contact stress calculated by transient dynamics is greater than that calculated by static. The fatigue life based on transient dynamics is 47 417 h, which is closer to the experimental results, and the relative errors are 9.32% and 15.14%. The analysis results provide reference and basis for the optimization and fatigue life evaluation of the drive axle gear system of loader.关键词：Loader;Wheel edge reducer;Gear;Contact;Fatigue life
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发布时间：2023-11-16 - 摘要：A thin-walled sandwich structure filled with polyurethane is introduced. Based on the hyperelastic constitutive model of polyurethane, the energy absorption characteristics of the structure are studied and compared with single-layer and double-layer thin-walled steel circular tubes. Applying quasi-static load and dynamic load to the three structures, the deformation mode, energy absorption characteristic parameters, crushing force and stroke efficiency of the three structures are obtained. The results show that under quasi-static loading, the thin-walled circular tube filled with polyurethane produces axisymmetric deformation, and the average load and specific energy absorption are higher than the other two structures. Under dynamic loading, the stroke efficiency of thin-walled circular tube filled with polyurethane is small, but the average load and specific energy absorption are higher than the other two structures.关键词：Thin walled sandwich structure;Polyurethane;Specific energy absorption;Crushing force;Finite element analysis
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发布时间：2023-11-16 - 摘要：Seven truss lattice cells were designed by the combined superposition method, and the specimens with the same porosity of seven lattice structures were prepared by the Multi Jet Fusion（MJF） 3D printing technique. The mechanical properties, deformation modes and energy absorption capacity of different lattice structures were analyzed by uniaxial compression experiments and finite element simulations. It show that all seven structures go through the linear elastic stage, platform stress stage and densification stage during the compression process, and the deformation process of SBO structure with bending as the dominant type is relatively smooth, and its platform stress(σpl=2.76 MPa) and platform strain interval length（23% to 72%） are higher than other lattice structures, and the accumulated energy absorption value reach 702 J/mm~3, showing excellent mechanical properties and energy absorption capacity.关键词：3D printing;Multi jet fusion;Truss lattice structure;Mechanical properties;Energy absorption
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发布时间：2023-11-16 - 摘要：Transportation and human protection industry constantly demands for lightweight and better energy absorption materials and structures. By designing customizable porous materials, the mechanical properties and energy absorption of hexagonal honeycomb-structured polydimethylsiloxane（PDMS） were investigated through experiments and numerical simulations. PDMS has adequate viscoelastic properties for 3D directing ink writing（DIW）, therefore the honeycomb structures with different line widths were fabricated through optimizations of the printing speed and air pressure. Quasi-static compression tests were performed on the fabricated samples to evaluate their mechanical properties and energy absorption. The results show that the average stress in the plateau stage of the honeycomb structure increase with the increase of the line width, but is anisotropy. The honeycomb structure with line width of 900 μm has highest energy absorption of 0.018 J/cm~3. The corresponding finite element analysis were in agreement with the experimental results.关键词：3D directing ink writing;Elastomeric honeycomb structure;Numerical simulation;Mechanical properties;Energy absorption
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发布时间：2023-11-16 - 摘要：Based on the computational fluid dynamics, a numerical model of deep-sea landing vehicle was established to meet the requirements of deep-sea landing vehicle for large scale and long period submarine operation. The key design variables were determined by parametric analysis of the control point of the landing vehicle bow modeled line, which was carried out in the Isight software through the combination with SolidWorks and Fluent. The optimal latin Hypercube method is used to select sample points for the direct navigation resistance calculation, an approximate model of design variable-resistance was established based on the radial basis function neural network, and the optimal design of landing vehicle bow modeled line was carried out by using the adaptive simulated annealing algorithm. The optimized resistance is reduced by 14.24%, and the hydrodynamic performance is improved. This work provides a basis for the optimization design of the deep-sea landing vehicle and can also provide a reference for the numerical analysis of other submersible vehicles.关键词：Deep-sea landing vehicle;Drag;Optimal design;Bow modeled line;Computational Fluid Dynamics（CFD）
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发布时间：2023-11-16
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