最新刊期
期 3 ， 2023
- 摘要：The complex and changeable working conditions of mechanical equipment in industrial field lead to uneven distribution of fault samples, which brings great trouble to traditional machine learning. In order to solve this problem, proposes a bearing fault transfer diagnosis method based on domain adaptive neural network and balanced dynamic distribution adaptive. Firstly, According to the characteristics of bearing vibration fault samples, the convolution layer of convolutional neural network is improved by wavelet transform, and the characteristics of bearing samples are extracted adaptively. Then, Maximum Mean Discrepancy measure and weight regularization are used to process the generated features in the loss function to reduce the difference in sample distribution and obtain the domain adaptive neural network model. Finally, A-distance is used to improve the equilibrium distribution adaptive to make it have dynamic characteristics, further improve the difference of sample distribution, and realize bearing transfer diagnosis by KNN classifier. Through experimental verification, the proposed method can accurately migrate the bearing fault state in the same bench rig cases and cross bench rig cases, proving that the method can effectively solve the problem of uneven distribution of unlabeled samples under variable working conditions, and has the effectiveness and robustness.关键词：Bearing;Domain adaptive neural networks;Balanced distribution adaption;Wavelet transform;A-distance;Transfer diagnosis
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发布时间：2023-08-01 - 摘要：Based on Hamilton principle, the nonlinear magneto-elastic vibration equation of ferromagnetic plate is established under the combined action of mechanical load and harmonic magnetic force induced by magnetization. For the boundary conditions with two long simply supported edges, the transverse vibration differential equations after variables separation is obtained by Galerkin method. The multi-scale method and Lyapunov stability theory are used to solve the first-order principal resonance problem under electromagnetic excitation, the amplitude-frequency equation and the stability criterion of the steady-state solutions are obtained. Through numerical examples, the amplitude-frequency characteristic curves, the amplitude-magnetic field intensity curves and the amplitude-velocity variation curves of the ferromagnetic plate are obtained. The results show that the amplitude of stable solutions increases with the increase of magnetic field intensity amplitude. The nonlinear stiffness increases with the increase of the velocity, the hard-spring characteristics are enhanced and the nonlinear characteristics are more significant.关键词：Ferromagnetic plate;Axially moving;Principal resonance;Harmonic magnetic force;Multi-scale method
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发布时间：2023-08-01 - 摘要：Aiming at the mutation in demodulation of the envelope estimation function, a local mean decomposition method for singular interval envelope reconstruction is proposed. This method determines that the reason for the sudden change in the demodulation of the envelope estimation function is the intersection of the envelopes, and defines the local area where the intersection exists as a singular interval. Combined with the extreme value symmetry theory, the interpolation points in this interval are expanded, and the cubic Hermitian interpolation is used to perform local reconstruction. A singular interval envelope reconstruction algorithm is formed. The simulation signal and the application of fault diagnosis of reciprocating compressor bearing prove that the proposed method solves the envelope crossing problem, suppresses the demodulation mutation phenomenon, and the decomposition result has more obvious fault characteristics.关键词：LMD envelope reconstruction;Mutation in demodulation;Reciprocating compressor;Fault diagnosis
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发布时间：2023-08-01 - 摘要：Gearbox is widely used in petrochemical, shipbuilding, electric power and construction machinery, etc., and its fault monitoring and diagnosis technology is always a hot issue. A gearbox fault diagnosis method based on DS evidence theory, which integrates oil and vibration with multiple parameters is proposed. Aiming at the problem that the traditional single vibration signal analysis method is not sensitive to gear wear in the early stage, radial basis function（RBF） neural network is used to establish the classification model of the fusion of vibration time domain features and oil features. Vibration frequency-domain features are extracted adaptively based on high-dimensional variational autoencoder and fault classification is completed. Different evidence bodies obtained by RBF neural network and high dimensional variational autoencoder are fused by weighted DS evidence theory to obtain the final diagnosis result. Compared with different fusion methods, the effectiveness of the proposed method in gear fault diagnosis is verified.关键词：Weighted DS evidence theory;Neural network;Variational autoencoder;Oil;Vibration
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发布时间：2023-08-01 - 摘要：The long-term continuous high-speed rotation of the rotor of the steam turbine generator set inevitably leads to the change of the rotor vibration state. The quality of the rotor vibration state directly affects the safe operation of the whole unit. Therefore, it is imperative to study the early warning method. Firstly, the running law of rotor vibration is analyzed. Secondly, based on the vibration operation law, the calculation method of rotor vibration abnormal threshold is proposed. Thirdly, based on the abnormal threshold and nonlinear state estimation technique（NSET）, the rotor vibration early warning method is proposed. Finally, it is tested and verified by the operation data of a power plant, and compared with the vibration early warning method based on back propagation（BP） neural network. The results show that the proposed method can accurately and effectively realize the rotor vibration early warning.关键词：Rotor vibration;Calculation method of threshold;Nonlinear state evaluation model;Warning method
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发布时间：2023-08-01 - 摘要：An articulated pipe composed of a flexible pipe and a rigid pipe is a typical hybrid rigid-flexible dynamical system involving flow-induced vibrations. Based on Hamilton′s principle, the governing equations of motion of the hybrid rigid-flexible pipe system were established. The partial differential equations of motion were discretized via Galerkin′s approach using the modal functions of a cantilevered beam. Instabilities and critical flow velocities were analyzed and calculated as a function of the stiffness of the rotational spring, mass ratio, length ratio of the rigid and flexible pipes. The results show that the critical velocities decrease as the increasing of length ratio and the system mainly suffers second mode instability. The hybrid pipe undergoes complicated transference of “second mode instability-regain stability-third mode instability” at a certain value of stiffness when the flow velocity increases. With the increasing of mass ratio of flexible pipe, a transition from second mode instability to fourth mode instability is observed.关键词：Hybrid rigid-flexible pipe conveying fluid;Flow-induced vibration;Eigenvalue;Critical flow velocity;Instability
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发布时间：2023-08-01 - 摘要：A type of two-degree-of-freedom vibration system with bilateral nonlinear constraints is established. Through the fourth-order Runge-Kutta numerical algorithm, the dynamic characteristics of the p/1 periodic motion of the system under low frequency excitation, the law of mutual transition and the corresponding law of the coexistence zone of gap and period are analyzed. The cell mapping method is used to study the distribution law of different attractors and attracting domains in the coexistence area of periodic motion. The results show that the periodic motions of the system are mainly transferred through Grazing bifurcation and Saddle-node bifurcation. Due to the irreversible transition process, there is a coexistence zone of periodic motion between adjacent motions. As the gap increases, the range of the coexistence zone of periodic motion of the system gradually decreases.关键词：Chattering-impact motion;Non-linear constraints;Bifurcation;Attractors coexistence
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发布时间：2023-08-01 - 摘要：Focusing on investigating the brake squeal problem of a disc brake at 3 000 Hz. To this end, the noise of this frequency is reproduced on the bench, the laser Doppler vibration measurement technology is used to obtain the operational deflection shape（ODS） at this frequency. Finite element analysis（FEA） model is established and modified according to the experimental modal. The complex eigenvalue analysis is adopted to retrieve the complex eigenvalues and mode shapes.The correlation analysis is used to confirm that the complex eigenvalue results are valid for the actual noise ODS results.Afterwards, analysis of the components contribution and the components modal contribution of this unstable mode are used to provide corresponding structural optimization plan, and a bench test has been carried out to verify the effectiveness of this method.关键词：Disc brake;Brake noise;Laser vibrometer;Complex eigenvalue analysis;Correlation analysis
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发布时间：2023-08-01 - 摘要：Aiming at the low accuracy with unbalanced data sets in existing bearing fault diagnosis methods, we proposed a bearing fault diagnosis method based on importance weighted auto-encoder（IWAE） in unbalanced data sets. It was trained by minority samples, and the generated samples were added into original data sets to obtain balanced data sets. Then, deep learning method was used as diagnose network, and the balanced data sets were fed into it as input, so as to adaptively learn fault characteristics and realize fault classification. A large number of qualitative experiments showed that when the imbalance rate was 1∶7, the method could correctly classify the balanced samples, and the accuracy rate was 98.90%. Based on various imbalance ratios, the proposed method had better convergence and generalization than other existing models.关键词：Unbalanced data set;Importance weighted autoencoders;One-dimensional multi-scale convolutional neural network;Bearing fault diagnosis
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发布时间：2023-08-01 - 摘要：In order to characterize the Ⅰ-Ⅱ mixed-mode fracture performance of 2D-C/SiC composites, Arcan butterfly specimens with unilateral cracks were used, and the mode-Ⅰ and mode-Ⅱ fracture shape factors of the specimen were calibrated through finite element model. The Arcan disc device was used to carry out mode-Ⅰ, mode-Ⅱ and Ⅰ-Ⅱ mixed-mode fracture tests upon 2D-C/SiC butterfly specimens, and the macroscopic and microscopic fracture modes and strength properties of the specimens under different loading paths were investigated. The results show that the fracture toughness of mode-II of 2D-C/SiC material is higher than that of mode-I. With increasing of the loading angle, the influence of shear stress on the crack propagation path increases, and meanwhile the fracture resistance of the specimens presents a tendency to increase. The applicability of several fracture criteria is demonstrated, and an Ⅰ-Ⅱ mixed-mode fracture criterion for 2D-C/SiC composites is suggested.关键词：Ceramic matrix composites;Mixed-mode fracture;Finite element model;Stress intensity factor;Fracture criterion
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发布时间：2023-08-01 - 摘要：The mechanical properties of fiber reinforced composite aluminum honeycomb sandwich structure were studied by three-point bending test. The effects of different types of panels（carbon fiber panel, glass fiber panel, carbon fiber/glass fiber panel）, panel thickness and core aperture on failure modes, ultimate load and energy absorption were analyzed. The results show that the carbon fiber/aluminum honeycomb sandwich structure has stronger ultimate load and energy absorption than the other two structures. The thicker the panel, the smaller the core aperture, the stronger the ultimate load and energy absorption of the structure. The thickness of the panel has a great influence on the energy absorption, and the aperture of the core has a great influence on the ultimate load. The finite element simulation of carbon fiber/aluminum honeycomb sandwich structure and the comparative analysis of its failure and deformation process verify the validity of the model, and provide guidance and help for experimental design and analysis.关键词：Composite material;Honeycomb sandwich structure;Three-point bending;Ultimate load;Energy absorption
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发布时间：2023-08-01 - 摘要：To obtain the filling material with good compression mechanical properties, two kinds of orthogonal trapezoidal honeycomb aluminum with different structures were manufactured（90°orthogonal trapezoidal honeycomb aluminum and 45° orthogonal trapezoidal honeycomb aluminum）, the mechanical properties of the material under quasi-static axial loading was analyzed. Two kinds of orthogonal trapezoidal honeycomb aluminum were filled with polyurethane foam, and the effect of polyurethane filling on the orthogonal trapezoidal honeycomb aluminum was analyzed. The results show that compared with 45° orthogonal trapezoidal aluminum honeycomb, the performance of 90° orthogonal trapezoidal honeycomb aluminum is better, and the peak stress, plateau stress and unit volume absorption energy of the two kinds of orthogonal trapezoidal honeycomb aluminum are improved after polyurethane filling. However, the energy absorption efficiency is not significantly improved after being filled with polyurethane, and the strain corresponding to the maximum energy absorption efficiency decreases.关键词：Orthogonal trapezoidal honeycomb aluminum;Polyurethane;Static compression;Mechanical property
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发布时间：2023-08-01 - 摘要：Under the bending load generated by automobile collision, the composite safety components should have the ability to resist deformation and dissipate crashworthiness energy. In order to determine the mechanical parameters of the progressive damage material model of a woven carbon fiber composite thin-walled beam in the three-point bending condition, the mechanical properties test of the woven carbon fiber composite material and the three-point bending experiment of square tubes made by this material were carried out, thus got the basic mechanical parameters, bending failure history and force-deformation characteristics. Then the effects of the non-test parameter in the progressive damage material model on the simulation results were analyzed and the effectiveness of the multilayer shell modeling method were discussed. By comparing with the experimental results, the non-experimental parameters and effective simulation modeling methods for the progressive damage model of composite materials were gotten. The obtained material properties can be used for the crashworthiness simulation analysis of this material structure in similar working conditions.关键词：Plain woven carbon fiber reinforced composite material;Mechanical properties;Three-point bending;Material model;Model calibration
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发布时间：2023-08-01 - 摘要：Definition based on the incremental theory of plasticity of J integral, combining the method of experiment and computer simulation, the method of crack propagation rate based on elastic-plastic mechanics is studied, the research shows that the crack growth rate curve obtained by the incremental plastic J integral is well described the material fracture mechanics performance characteristics, ΔJ integral as the crack growth driving force is verified the rationality of the parameters, in order to further research to explore mechanism of crack extension provides research foundation, a new model is proposed based on the 7N01 aluminum alloy test data, it takes into account the effect of stress ratio on crack propagation, and it is suitable for estimating fatigue life of materials in engineering practice.关键词：Fatigue crack growth rate;Elastic-plastic mechanics;J-integral;Stress ratios effect
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发布时间：2023-08-01 - 摘要：In order to study the strength performance of the airship envelope and the influence of overpressure bearing on its residual strength, the sample forms and experiments plans for the uniaxial and biaxial tensile of the envelope material were designed, and the tearing situation of the airship was analyzed with the help of a high-speed camera. Based on the experimental data, fitted the uniaxial tensile strength curve when the airship bears air pressure, and the longitudinal and latitudinal strength envelope line of the material when it was biaxially stretched. The experimental results demonstrate that there is a negative correlation between the residual strength of the envelope and the airship bearing air pressure when uniaxially stretched, the bearing strength of the envelope is comprehensively affected by the longitudinal and latitudinal strengths when biaxially stretched. This experiment also analyzes the failure situation of the airship envelope, which can provide an experimental guidance for its strength prediction.关键词：Envelope;Airship;Tear damage;Strength test;Single double axis stretching
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发布时间：2023-08-01 - 摘要：Since there are more systems to be observed on the sites and the observation time is shorter than the average life of the product, the life data actually collected is often heavily censored data. For such data, the classical parameter estimation methods can’t provide accurate and robust estimation. For this reason, a parameter estimation method based on the Weibull auxiliary model is proposed, and the numerical experiment results validate that this method can provide a more accurate and robust estimation of the gamma distribution than the classical parameter estimation method under the condition of heavily censored data.关键词：Gamma distribution;Performance evaluation;Heavily censored data;Weibull auxiliary model
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发布时间：2023-08-01 -
PARAMETER ANALYSIS AND OPTIMIZATION OF MAGNETIC ADSORPTION UNIT FOR CRAWLER WALL-CLIMBING ROBOT (MT)
摘要：Due to low adsorption efficiency of magnetic adsorption unit（MAU） of crawler wall-climbing robot, the parameters analysis and structural optimization design are carried out based on DOE, RSM and sensitivity analysis method. The functional relationship between the parameters of the MAU and the magnetic force is obtained by the finite element simulation model, DOE and RSM. The sensitivity of parameters of the MAU to the magnetic adsorption force is determined by the sensitivity analysis. The length, the width, the height of the permanent magnet, the thickness of the yoke and the distance between the permanent magnet and the wall are selected as the design variables. After the optimized design, the adsorption efficiency of the MAU is increased from 2.029 7 to 3.938 1.关键词：Wall-climbing robot;Magnetic adsorption;Unit sensitivity analysis;Structural optimization- 8
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发布时间：2023-08-01 - 摘要：To solve the problems of complex calculation and weak applicability of the traditional interval estimation methods such as Weibull distribution with the different parameters, a simple interval estimation method suitable to the conditions of multi-parameters was proposed. Through the expression of Weibull distribution, the pivotal-variable obeying chi-square distribution was obtained and the degrees of freedom were modified. Combined with the point estimation results from maximum likelihood estimation and the empirical estimation shape parameter in the Weibull distribution, the interval estimation method of two parameters in Weibull distribution was established. The confidence of proposed interval estimation method was verified by Monte Carlo simulation, and the applicability of the method on different parameters was also analyzed. Furthermore, comparisons with the results computed from traditional least square and maximum likelihood estimation methods were carried out by using simulation. Simulation results indicated that the modified pivotal-variable method has simple calculation process and small deviation from predefined nominal confidence with the different parameters. Therefore, it can be concluded that proposed method executes the more effective estimation than the traditional methods.关键词：Weibull distribution;Interval estimation;Confidence;Monte Carlo simulation;Modified pivotal-variable
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发布时间：2023-08-01 - 摘要：In order to improve the load-carrying capacity of the hydrodynamic bearing, and reduce the calorific value and friction coefficient at the same time, a multi-objective optimization model of the hydrodynamic bearing was established. Aiming at the shortcomings of the traditional optimization algorithm that the convergence speed is slow and it is easy to fall into the local optimal solution, an adaptive strategy assisted the golden jackal optimization algorithm is proposed to improve the exploration and exploration ability of the golden jackal algorithm. The performance of the adaptive strategy assisted the golden jackal optimization algorithm is verified by an example with constraints. The results show that the adaptive strategy assisted the golden jackal optimization algorithm has good convergence performance. The algorithm is used to solve the multi-objective optimization problem of hydrodynamic bearings. The optimization results show that the optimized structure has a great improvement in performance compared with the initial structure, the load capacity is increased by 12.257%, and the calorific value and friction coefficient are reduced respectively by 15.610% and 33.333%.关键词：Golden jackal optimization algorithm;Adaptive strategy;Hydrodynamic bearing;Multi-objective optimization;Optimization algorithm
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发布时间：2023-08-01 - 摘要：The impact characteristics and residual compressive strength of the honeycomb sandwich structure under different impact energies and different boundary conditions were studied by testing and finite element analysis. The Vumat subroutine was used to establish a three-dimensional progressive failure criterion. The validity of the simulation model was verified by experiments. The results show that the simply supported specimens are more prone to damage and the peak force is lower, but the energy absorption effect is slightly better. At the same time, the residual compressive strength of the simply supported sample after impact is relatively low. When the impact energy is low, the boundary conditions have an important influence on the residual compressive strength. The influence of boundary conditions on the residual compressive strength can be ignored when the impact energy is large.关键词：Honeycomb sandwich structure;Hybrid composite skin;Simulation analysis;Low-velocity impact properties;Residual compression strength
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发布时间：2023-08-01 - 摘要：In order to study the influence of load change on the meshing characteristics of cycloid pinwheel of RV reducer, considering the modification of cycloid tooth profile, the three-dimensional model of cycloid pinwheel mechanism was established by UG. The changes of meshing tooth pairs and meshing stress of cycloid pinwheel in a meshing transmission cycle were analyzed by using the transient dynamics module of Ansys, and the simulation was compared with the theoretical contact stress. Results show that the overall trend of contact stress between simulation and theory is consistent, the number of meshing teeth and meshing stress of cycloid pinwheel show a periodic law, and increase with the increase of load. The change trend of contact stress and equivalent stress is opposite to the number of meshing teeth, the more the number of meshing teeth, the smaller the meshing stress. The equivalent stress of the needle tooth in the length direction increases with the increase of load, and the stress has a trend of uniform distribution, but the change is small. The finite element analysis has certain reference significance for the design, analysis and manufacture of RV reducer.关键词：Cycloid needle wheel;ANSYS;Transient dynamics;Meshing characteristics;Contact stress
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发布时间：2023-08-01 - 摘要：A statistical model of static friction factor of joint surfaces was deduced, which was more in line with the actual situation and takes into account the interaction of asperities and the deformation of the substrate. Based on the contact load model of joint surfaces considering the interaction of asperities and the deformation of the substrate, the statistical model of the static friction factor of joint surfaces considering the interaction of asperities and the deformation of the substrate was deduced according to the definition of the static friction coefficient of joint surfaces. The parameters of joint surfaces measured by the experiment are substituted into the model for simulation, and it is found that the static friction coefficient of joint surfaces considering the asperities interaction and the substrate deformation is larger than that without considering the asperities interaction and the substrate deformation. The influence of the asperities interaction and the substrate deformation decreases with the increase of the dimensionless normal contact load and decreases with the decrease of the dimensionless distance of joint surfaces, and increases with the decrease of the root mean square of the profile height. The simulation results of the model are compared with the experimental data of the static friction factor. The results show that the static friction coefficient of joint surfaces considering the asperities interaction and the substrate deformation is closer to the experimental data, which shows that the model is correct.关键词：Joint surface;Asperity interaction;Substrate deformation;Static friction factor;Statistical model
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发布时间：2023-08-01 - 摘要：With the increase of the load and running speed of heavy freight locomotives, the wheel wear becomes more and more serious, which can exacerbate the polygon formation of wheels. The influence of polygonal wheels on the dynamic performance of a wide-gauge six-axle heavy freight locomotive is examined, taking the ГОСТ standard as the main reference. The finite element model of the wheelset is established, and then a rigid-flexible coupling model is established by using the multi-body dynamics software. The polygonal wheel is described by the harmonic function. Effects of the parameters, unrounded amplitudes and polygon numbers are analyzed. The results show that the critical speed decreases because of the effect of the polygonal wheel. Within the design speed range of 120 km/h, the wheel polygon has little influence on the running comfort; the influence on the locomotive safety and the vehicle dynamic characteristics is closely related to the modal characteristics of the vehicle.关键词：Six-axle heavy freight locomotive;Polygonal wheel;Rigid-flexible coupling;Dynamic performance;Co-Co
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发布时间：2023-08-01 - 摘要：In the process of plunge cylindrical grinding, it is difficult to directly measure the contact stiffness between the grinding wheel and the workpiece. In order to solve this problem, a simplified method for qualitatively determining the contact stiffness between the grinding wheel and the workpiece is proposed, and the grinding parameters are optimized. Based on the dynamic model of plunge cylindrical grinding process, the transfer function of grinding process is deduced, and the mathematical model of the time constant and contact stiffness is established. A simplified method for qualitative determination of grinding contact stiffness is proposed. Further, multiple tests are conducted by controlling the wheel feed speed and the workpiece speed. According to the experimental results, the variation of the system time constant and the grinding force with the grinding parameters are analyzed. The relationship model between the contact stiffness and the grinding parameters is established by regression analysis, and the optimal values of the wheel feed speed and the workpiece speed in the specific grinding process are determined under the condition of meeting the machining requirements.关键词：Cylindrical plunge grinding;Contact stiffness;Grinding parameters;Time constant;Grinding process model
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发布时间：2023-08-01 - 摘要：The grinding of spiral bevel gears is a nonlinear and dynamic complex process. It is significant to explore the complex grinding mechanism of spiral bevel gears by simulating the grinding process based on finite element method. A finite element model of composite abrasive grinding was established based on material constitutive equation of Johnson-Cook force-thermal coupling. And the changes in the tooth surface temperature field, grinding force and abrasive wear were compared and analyzed under different grinding speeds, grinding depths and abrasive spacing condition. The simulation results were also verified by the experimental results.The results show that the grinding depth is the most important factor to affect the grinding surface performance. The influence of the compound abrasive grain interference on the tooth surface temperature field and the resulting grinding vibration cannot be ignored. It could provide theoretical guidance for the research and practical processing of grinding surface performance of spiral bevel gears.关键词：Spiral Bevel Gear;Grinding;Force-heat coupling;Performance analysis
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发布时间：2023-08-01 - 摘要：To reduce the raw material waste problems and repeated trial production in the matching process of rubber parts hardness and stiffness, the correlation analysis of rubber parts stiffness and hardness was carried out. Based on a rectangular rubber spring cushion, with uniaxial compression and tensile tests, the theoretical parameters of the Mooney-Rivlin model were calculated, and the results were verified by the least square method. The stiffness of the rectangular rubber spring pad increases nonlinearly with the increase of deformation, which Abaqus calculated. Based on the experimental data of rubber hardness, the exponential quadratic nonlinear function of hardness and Mooney-Rivlin model parameters was established. As a result, the hardness of rubber was positively correlated with the material parameters. The relationship between elastic modulus and hardness was transformed into elastic modulus and material parameters C2 and C1. Furthermore, the stiffness displacement curve of rubber material was obtained by simulation analysis to find the relationship between rubber material parameters and stiffness. Finally, with Mooney-Rivlin model parameters as the bridge, the correlation conclusion between stiffness and hardness of rubber parts was obtained.关键词：Mooney-Rivlin;Rubber hardness;Rubber stiffness;Constitutive model parameters
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发布时间：2023-08-01 - 摘要：For improving the mobility and obstacle climbing ability of the bionic gecko, a bionic moving joint configuration in legged style with two degrees of freedom is designed and developed. Based on the principle of mechanism, the sucker, steering engine and planar linkage, etc. are organically integrated with gecko morphology, and 3D solid modeling of the joint components based on features is constructed, which realize the motion function simulation of the legged joint on the basis of profiling design. The correctness and feasibility of the transmission design are verified through the trajectory simulation of the large and small leg joints. At the same time, the swing angle（0～73°） and obstacle climbing height（＞30 mm） of the bionic joint are analyzed. The results of static analysis show that the bionic joint under different load-bearing environments（such as flat ground, hang upside down, vertical wall） can meet the design requirements of strength and stiffness. The experimental test of the bionic gecko shows that the legged joint has not only stable movement and reliable force transmission performance, but also good bionic mobility. This study provides an new ideas for the mobile technology exploration of bionic gecko.关键词：Bionic;Legged joint;Gecko;Modeling;Simulation;3D printing;Experiment
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发布时间：2023-08-01 - 摘要：In order to improve the stability of diagonal trot gait for quadruped robot, a foot end trajectory planning method based on Bezier curve is proposed. Aiming at the diagonal trot gait of quadruped robot, the kinematics model of parallel legs of quadruped robot is established, the forward and inverse kinematics are solved by geometric method, and the foot end trajectories of swing phase and support phase are optimized based on zero impact principle and PD controller. The comparative test is carried out by using Webots simulation platform and experimental prototype. The results show that when the proportional coefficient in X direction is 20, the differential coefficient is 0.75 s, the proportional coefficient in Y direction is 20 and the differential coefficient is 0.5 s, the foot end trajectory of quadruped robot is smooth without sudden change of speed and acceleration, and the gait of diagonal trot is more stable.关键词：Quadruped robot;Diagonal trot;Webots;Bezier curve;Foot trajectory
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发布时间：2023-08-01 - 摘要：In view of the low accuracy of cutting force prediction caused by the difficulty of considering the tip arc radius, the main cutting edge arc radius and the tool working angle in the traditional turning force prediction model, an equivalent turning force model considering the tip arc, the main cutting edge arc radius and the working angle based on a small amount of turning force experimental data is established in this paper. The model is a turning force equivalent model of ideal turning tool with three nonlinear equations with equivalent principal deflection angle, equivalent edge inclination angle and equivalent normal forward angle as independent variables through the turning force experimental data and coordinate transformation matrix obtained by turning once. A turning force prediction model based on the equivalent model is established. Finally, the effectiveness of the prediction model is verified by turning force experiments.关键词：Equivalent processing;Unit cutting force;Turning force prediction
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发布时间：2023-08-01 - 摘要：When mechanical components are subjected to multiaxial cyclic loading during operation, the additional strengthening effect is easy to occur. Using uniaxial fatigue life calculation formula to predict their life will produce large errors. However, the existing multiaxial fatigue life prediction models are not convenient for engineering applications because it contains a large number of material constants. To solve the above problems, based on the initiation and promotion mechanism of fatigue microcracks under different stresses, combined with the shear damage model, a new expression of damage parameters is proposed, and the corresponding multiaxial fatigue life prediction model is derived combined with the Manson-Coffin-Basquin equation. The test data of two materials under the non-proportional loading and proportional loading path are used to verify the proposed life prediction model, and compared with the prediction results of the FS model. The results show that the proposed model has a good prediction effect. Finally, the model is applied to the fatigue life prediction of a big pendulum boom, and the results show that the boom meets the fatigue life requirements.关键词：Multiaxial fatigue;Additional strengthening effect;Damage parameter;Fatigue life predicted;Nonproportional loading
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发布时间：2023-08-01 - 摘要：To quickly evaluate the safety of damaged bridge structures in the service process of cranes, a real-time prediction method for the fatigue life of bridge structures based on the optimal additive agent model is proposed. Based on the measured load data, the randomness of the relevant parameters of the service conditions is characterized by the combination of the working cycle process. In line with the most unfavorable service conditions, the stress weak position of the bridge structure is determined through finite element statics analysis and failure case statistics. And the structure finite element model is established for fatigue damage and life prediction. The MSC. Fatigue′s S-N module and crack propagation module are employed to simulate the residual life of the structure under random working conditions, and the influence of different crack depths on the residual life of the structure is analyzed. The Kriging model for the life prediction of the bridge structure that is optimized by the Pelican Optimization Algorithm and additive point criterion is created by the Latin Hypercube Sampling method and the black box theory. The real-time fatigue life prediction of bridge structures during trolley movement with load by Miner linear cumulative damage theory. The bridge structure of QD20/10 t × 43 m × 12 m general bridge crane is taken as an example to verify the feasibility of the proposed method. Comparing the proposed method with the traditional fatigue life calculation method based on finite element simulation, the results show that it can accurately assess the remaining life of the damaged bridge structure with fewer simulation calls and shorter simulation time, which can provide some reference significance for crane maintenance cycle formulation and scrapping decisions.关键词：Fatigue life;Kriging agent model;Finite element simulation;Bridge structures;Work cycle
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发布时间：2023-08-01 - 摘要：Due to the complex material and shape of synchronous belt, it has complex mechanical behavior in normal operation. To solve this problem, propose a matrix model to calculate the tangential pressure of the meshing part between tooth and pulley. In the matrix model, use spring to replace the contact between synchronous belt and pulley, synchronous belt was discretized and separated into independent parts. In order to verify the model correctness, multi-body dynamics software RecurDyn was used to simulate the synchronous belt transmission system. The results show that the calculated results is closed to simulation results at the beginning and the end of the meshing part where the tangential pressure is larger, and there are some difference in the meshing part where the tangential pressure is smaller. Comparing with other methods, the matrix model has less computation, which solves the difficulty of calculating the tangential pressure of the belt, and provides a theoretical basis for the selection and design optimization of synchronous belt.关键词：Synchronous belt;Multibody dynamics analysis;RecurDyn;Rigid-flexible coupling dynamics simulation;Transmission performance
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发布时间：2023-08-01 - 摘要：Active gear design is a method that can pre-control gear meshing performance directly. In order to study the influence of active gear design on the bearing characteristics of tooth surface, the relationship between active modification parameters of the face gear and bearing characteristics of tooth surface is studied. Firstly, the contact model of the gear pair is established by the finite element method, and then different groups of active modification parameters are designed for simulation analysis. The results show that the geometric transmission error greatly influences gear transmission stability and contact strength, and controlling its amplitude can control bearing transmission error amplitude. Pre-designed contact path inclination angle within 30° neighborhood, bearing contact characteristics are better. The contact ellipse length mainly affects the contact strength of tooth surface and bending strength of tooth root. According to the simulation results, when it takes 0.5～0.75 times of tooth width, face gear pair has better bearing contact characteristics.关键词：Active modification;Face gear;Transmission Error;Strength;Stress
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发布时间：2023-08-01
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