最新刊期
期 6 ， 2022
- 摘要：Aiming at the problem that the vibration signal in diesel engine fault diagnosis is non-stationary and nonlinear, and the original signal is directly input into the Convolutional Neural Network（CNN） for fault diagnosis with poor effect, a new method based on PCA-EDT-CNN is proposed. Firstly, use Principal Component Analysis（PCA） to adaptively reduce the original data collected by the sensor, and construct a qualified Principal Component Eigenvector Matrix（PCEM）; secondly, perform Euclidean Distance Transformation（EDT） on PCEM, calculate the Euclidean distance between each row and construct the Euclidean Distance Matrix（EDM）; finally, flatten PCEM and EDM into one-dimensional vectors and synthesize a one-dimensional sample sequence, input into One-Dimensional Convolutional Neural Network（1 DCNN） to train and diagnosis the model. A diesel engine preset failure test bench was built to verify the effectiveness of the method, and through comparison with traditional methods, the results show that the method has high accuracy in diagnosing different fault states of diesel engines and has practical engineering application value.关键词：1DCNN;PCA;EDT;Diesel engine;Fault diagnosis
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发布时间：2023-06-09 - 摘要：Aiming at the problem that the vibration signal of rolling bearing is difficult to extract due to the characteristics of non-linear, non-stationary and low signal-to-noise ratio, a new fault extraction method based on symplectic geometry mode decomposition（SGMD） and multipoint optimal minimum entropy deconvolution adjusted（MOMEDA） theory is proposed. Firstly, a list of symplectic geometry components（SGCs） are obtained with SGMD decomposing the fault signal; secondly, SGCs are selected for signal reconstruction according to the correlation criterion, then, MOMEDA decomposition parameters are determined; finally, the reconstructed signal is processed with MOMEDA for enhancing the signal-to-nosise ratio, and envelope spectrum analysis is utilized to extract fault features. Simulated and experimental results verify that SGMD-MOMEDA can accurately extract the fault frequency of rolling bearings, and the comparison with the Empirical Mode Decomposition（EMD） shows that the SGMD is more accurate when reconstructing signals. This method has certain application value in the field of fault diagnosis.关键词：Symplectic geometry mode decomposition;Symplectic geometry component;Multipoint optimal minimum entropy deconvolution adjusted;Feature extraction;Rolling bearing fault diagnosis
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发布时间：2023-06-09 -
FAULT DIAGNOSIS OF SPIRAL BEVEL GEAR BASED ON LOCAL BISPECTRUM AND CONVOLUTIONAL NEURAL NETWORK (MT)
摘要：Aiming at the problem that the traditional fault diagnosis method has a low efficiency for spiral bevel gear fault diagnosis, a fault diagnosis method based on local bispectrum and convolution neural network（CNN） is proposed. By using local bispectrum of spiral bevel gears vibration signal containing global information as the input of the CNN, a diagnosis model is constructed to realize fault diagnosis of spiral bevel gears, which not only reduces the redundancy of fault information, but also improves the speed of CNN training. Comparing with traditional diagnosis results that use bispectrum and CNN, vibration signal and CNN, local bispectrum and SVM（Support Vector Machine）, local bispectrum and BP（Back Propagation） neural network, the proposed method has an optimal comprehensive performance which has an accuracy of 99.56% and model training time of 15 seconds.关键词：CNN;Local bispectrum;Spiral bevel gear;Fault diagnosis- 8
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发布时间：2023-06-09 - 摘要：Embedded smart bearing is a kind of structural unit with the characteristics of self sensing, self diagnosis, self-adaptive and self-regulation, which is one of the development directions of high-end bearing at home and abroad. Based on Ioannides-Harris theory, the load distribution of rolling bearing is analyzed. Combined with the finite element simulation model, the influence of outer ring grooving on bearing reliability is analyzed, and the radial grooving structure of outer ring of rolling bearing is determined. According to the theoretical analysis and numerical simulation, the embedded bearing vibration monitoring system is designed by combining the vibration sensor with the bearing body. By using the bearing life testing machine, the bearing life test is carried out and the vibration signals of smart bearings with different structures are collected. The experimental results show that the amplitude of vibration signal of smart bearing is higher than that of traditional bearing pedestal monitoring method, and it can effectively monitor the running state of the bearing; compared with the structure of axial grooving, the service life of the proposed smart bearing is similar to that of the ordinary bearing, which provides a new method for the condition monitoring and fault diagnosis of the rolling bearing.关键词：Smart bearing;Vibration monitoring;Radial grooving;Reliability
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发布时间：2023-06-09 - 摘要：In-situ monitoring of the dynamic contact force between catenary and pantograph is very important for the quality evaluation of pantograph catenary current collection. A monitoring method based on strain response was proposed to invert the value and position of the dynamic contact force between catenary and pantograph. The measurement principle, sensor installation method and calibration experiment of key parameters were described in detail. The monitoring system has been successfully applied to a metro test project with rigid overhead catenary. And the dynamic contact force between pantograph and catenary was monitored and analyzed when the subway was running at the speed of 60 km/h and 80 km/h, respectively. The results indicated that the dynamic contact force measurement method based on strain response has the advantages of high measurement accuracy, good data consistency and flexible sensor installation. It can not only accurately restore the value of dynamic contact force between catenary and pantograph, but also locate the position of the dynamic contact force on the carbon slide of pantograph. This work can effectively evaluate the performance quality of the coupling system of pantograph and catenary.关键词：Pantograph;Dynamic contact force between pantograph and catenary;Inversion;Structural health monitoring
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发布时间：2023-06-09 - 摘要：Most of the existing local linear embedding algorithms assume that the original data set is located in Euclidean space, but in reality almost all the original space is non-Euclidean space. Aiming at the problem that Euclidean space cannot effectively describe the nonlinear structure of the data and affects the performance of the feature extraction of the local linear embedding（LLE） algorithm, a local linear embedding algorithm based on the parameter matrix measurement on a symmetric positive definite（SPD-PMM-LLE） manifold is proposed. First, in order to find a suitable measurement method on the symmetric positive definite manifold to improve the performance of the algorithm, an efficient Riemann space metric learning method is introduced. The parameter matrix obtained by learning transforms the original manifold to a new and distinguishable manifold. Then use the locally linear embedding algorithm to mine the salient features. Finally, the efficiency of this method is verified by experimental results on multiple bearing data sets.关键词：Feature extraction;Symmetric positive definite manifold;Local linear embedding;Riemann space metric learning;Euclidean space
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发布时间：2023-06-09 - 摘要：In view of the shortcoming that the dimensivity reduction effect of local linear embedding（LLE） is greatly affected by the uniformity of sample distribution, the uniform distance is designed to replace the Euclidean distance in LLE, so the uniform distance local linear embedding（UDLLE） method is proposed, and the effectiveness of UDLLE is verified by typical curves. On this basis, a rolling bearing fault diagnosis method based on UDLLE was proposed, and the diagnosis example was verified. The experimental results show that UDLLE can obtain more effective low-dimensional features than some other methods, reduce the difficulty of subsequent diagnosis and improve the fault diagnosis accuracy.关键词：Local linear embedding;Uniform distance;Rolling bearing;Fault diagnosis
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发布时间：2023-06-09 - 摘要：The authenticity of the Houfeng seismograph, invented by the great scientist of the Eastern Han Dynasty, Zhang Heng, has been questioned by the outside world, because it has not yet been restored to a recognized model after being lost. The first major problem in the research on the restoration of the Houfeng seismograph is that the actual performance of the Houfeng seismograph is not clear, another major problem is the lack of effective performance inspection methods. In view of the two major problems, and based on the seismic mechanism analysis of the seismograph, the seismic performance and the anti-interference performance of the Houfeng seismograph, a test wave method is proposed, which takes the seismic sensitivity and anti-interference performance of the Houfeng seismograph as the criteria for testing whether the Houfeng seismograph responds to the test wave or not. Based on the determination of two kinds of test waves, namely the responsive test-wave and the unresponsive test-wave, a new restoration scheme of the Houfeng seismograph based on the response spectrum is proposed, and the natural vibration period（1.5 s～2.5 s） and response critical value（5 mm～10 mm） of the Houfeng seismograph are derived. An experimental prototype was developed, and the test showed that the restoration model meets the seismic display and anti-interference requirements of the Houfeng seismograph, and confirms the historical records authenticity of the Houfeng seismograph.关键词：Houfeng seismosgraph;Restoration model;Test wave;Seismic response spectrum;Seismicity performance;Anti-interference performance
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发布时间：2023-06-09 - 摘要：Acoustic emission technique can monitor the fatigue damage state of composite materials in real time. The identification accuracy of damage state depends on the processing and extraction of acoustic emission signals. A method of the acoustic emission signal processing based on harmonic wavelet power spectrum and energy spectrum is proposed. The damage state of composite materials with delamination defects can be identified. First, the uniaxial tensile experiment was carried out on the composite laminates with or without delamination defects. The acoustic emission signals during the process of damage evolution were recorded. Then, the frequency distribution range of different damage modes based on the harmonic wavelet packet decomposition was obtained according to the damage characteristics analyzed by frequency spectrum and energy spectrum. Compared with the traditional wavelet analysis, the harmonic wavelet analysis can detect the different damage characteristics and damage modes of composite blade with delamination defects accurately. It can be used to detect the operated state for in-service blades in practical engineering.关键词：Wind turbine blade;Acoustic emission signal;Composite materials;Harmonic wavelet;Damage
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发布时间：2023-06-09 - 摘要：Fatigue life of filled natural rubbers used in isolators is very dispersive owing to many uncertainties such as loads and temperature. Conventional crack initiation methods and crack propagation methods to determine fatigue life of rubbers are insufficiently to characterize the phenomenon; thus, probabilistic methods are desired in practical engineering. Based on the test data of uniaxial tensile fatigue experiment of rubbers, the cumulative distribution function and probability density function of residual fatigue life corresponding to two typical probability distribution models of three parameters Weibull distribution（3 PWD） and logarithmic normal distribution（LND） were derived and applied to the prediction of residual life reliability, in order to determine the minimum required under different probability distribution model of sample number and working condition number. The results showed that 3 PWD was more suitable to characterize the probability distribution of rubber fatigue life. The minimum values of the number of rubber fatigue test samples and the number of working conditions are distributed between 4 and 6. The log mean should be preferred for subsequent fatigue analysis when determining the median life. The research can provide guidance for the anti-fatigue design and test of rubber vibration isolators.关键词：Rubber;Fatigue life;Reliability;Weibull distribution;Logarithmic normal distribution;Residual life;P-S-N curve
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发布时间：2023-06-09 - 摘要：In order to study the effect of PMI foam on the impact resistance of the double-layered plates of aluminum alloy 2 A12-T4, the high-velocity impact experiments were performed to the aluminum alloy double-layered plates and aluminum alloy/PMI/aluminum alloy sandwich panel by using hemispherical-nosed projectiles launched by the one-stage gas gun system. The ballistic limit velocity and damage characteristics of the plates were obtained through the experimental results. The results show that the PMI foam core can restrict the plastic deformation of aluminum alloy plate under the same thickness as the aluminum alloy plate, decrease the absorption of impact energy and reduce the impact resistance of the aluminum alloy 2 A12-T4 double-layered plates by increasing the rigidity of the plate. In addition, the effect of the PMI foam core on the impact resistance of the plates decreases as the increase of velocity of the projectile.关键词：PMI foam;Impact;Ballistic limit;Damage characteristics;Sandwich panel
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发布时间：2023-06-09 - 摘要：In order to meet the requirements of vehicle lightweight and crash safety, flax-basalt fiber composite laminates were made. The tensile, shear and impact resistance properties of the composite structure were discussed through test and simulation analysis. Using the three-dimensional Hashin failure criterion of strain form and the stiffness linear degradation scheme based on fracture toughness, the Vumat subroutine was compiled to establish a low-speed impact finite element model. The effects of ply structure and ply angle on the low-speed impact resistance of laminates were studied. The flax-basalt fiber laminate structure was applied to the inner and outer panels of engine hood under static conditions and children’s head impact simulation analysis. The results show that the static stiffness and weight reduction effect of the structure are better than steel engine cover, the child head protection performance meets the requirements, and the performance improvement is more obvious when the inner plate adopts the composite structure.关键词：Flax fiber;Basalt fiber;Low speed impact;Child-pedestrian head impact simulation
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发布时间：2023-06-09 - 摘要：In view of the uneven mass distribution and the excessive weight of the power head gearbox bodies, and the first-order natural frequency is close to the excitation frequency generated by the second-stage gear transmission. The Genesis module in the Ansys Workbench simulation platform was used to analyze the modal topology of the gearbox. Based on the size to be optimized obtained from the topology optimization, the gearbox body was optimized by the target drive optimization tool. Without affecting the strength and rigidity of the gearbox body, the mass was reduced by 12.9%, and the first-order natural frequency was increased by 10.9%, which achieved the dual purpose of reducing weight and increasing the first-order natural frequency. The research results have practical guiding significance for saving manufacturing costs and improving product performance.关键词：Power head gearbox;Modal analysis;Topology optimization;Size optimization;Natural frequency
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发布时间：2023-06-09 - 摘要：A semidefinite programming-based optimization method is proposed for lightweight design of boom and stay bars of container cranes. The boom and stay bars are welded together by steel plates, and in engineering practices the cross-sectional dimensions of boom and stay bars are of discrete values. Thus, the lightweight design of boom and stay bars is a discrete sizing optimization problem. The cross-section of boom is irregular and after optimization the boom section may become distorted, which may negatively affect the assembling of boom with other parts. In view of this defect, a design method is proposed by transforming the discrete sizing problem into a section-type selection problem, which means selections of sections from a predefined set of available sections. To relax the discrete problem as a continuous problem, a linear relaxation approach based on the convex hull of discrete points is proposed, with which a linearized stiffness matrix is derived. Furthermore, a new method is proposed by implicitly containing the stress constraint within a narrowed compliance constraint. In this way, the original discrete optimization problem with stress and stiffness constraints is simplified as a compliance-constrained problem, which can be further reformulated as a relaxed semidefinite programming problem. With existing optimization solvers, the global optimum solution for the relaxed semidefinite programming problem can be quickly achieved. Based on the global optimum solution, a discrete feasible solution is derived through section rounding. Finally a numerical example of boom and stay bars of a certain contain crane is presented, and the result validates the effectiveness of the proposed method.关键词：Boom and stay bars;Lightweight design;Section-type selection problem;Compliance constraint;Semidefinite programming
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发布时间：2023-06-09 - 摘要：In view of stability requirements of compliant mechanisms, based on the Heaviside three-field mapping scheme and the compliance change rate constraint measure, the topology optimization problem of the compliance minimization of hinge-free multi-input multi-output compliant mechanisms with buckling constraints is investigated. Firstly, in order to solve the problem of pseudo-buckling modes and calculation efficiency caused by low-density elements, smooth penalty functions of the element stiffness matrix and stress matrix are constructed, and comprehensive measures to solve the corresponding problem are proposed. Furthermore, cooperating with the Pian mixed stress element formula, the aggregation function method, the Heaviside three-field mapping scheme and the compliance change rate constraint measure, the topology optimization model of hinge-free multi-input multi-output compliant mechanisms considering buckling is constructed. Then, the sensitivities of the objective function and buckling constraints are derived, and the MMA algorithm is adopted to optimize the topology optimization model. Finally, the numerical examples are given to illustrate the feasibility and effectiveness of this method.关键词：Compliant mechanisms;Compliance change rate constraints;Buckling constraints;Topology optimization;Material penalty model
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发布时间：2023-06-09 - 摘要：In view of the large difference between the elastic modulus of human bone structure and metal materials and the difficulty of control, the goal is to reduce or eliminate the “stress shielding” effect in a wide span, introduce a negative Poisson’s ratio metamaterial with an unconventional deformation mechanism, carry out the design and experimental research of porous microstructure with wide span and low elastic modulus. Based on the negative Poisson’s ratio auxetic structure unit, the three-dimensional cellular porous microstructures with different control parameters and porosity were designed.Experimental samples were prepared by selective laser melting. The variation rules between mechanical properties and structural parameters such as strength and elastic modulus were revealed through compression tests, and the matching degree of negative Poisson’s ratio microstructure and human bone was evaluated. The experimental results show that the auxetic structure has good manufacturability, and the forming quality is correlated with the concave angle and porosity.The mechanical properties of negative Poisson’s ratio auxetic structure are highly dependent on the geometric structure and porosity of the cell.Compared with the positive Poisson’s ratio structure, the auxetic structure with negative Poisson’s ratio has lower elastic modulus and similar yield strength under the same porosity, and can control the 316 L stainless steel bone material with wide span elastic modulus by 0.47 GPa～1.75 GPa.Therefore, the negative Poisson’s ratio auxetic microstructure has potential advantages in the application of human bone structure.关键词：Negative Poisson material;Bone structure;Porous materials;Mechanical property
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发布时间：2023-06-09 - 摘要：In order to study the structure design and mechanical properties of the cutterhead of D2000 Slurry balanced pipe jacking machine for composite formation, the static analysis of the cutterhead model was carried out, and the equivalent stress and deformation nephogram of the cutterhead were obtained. It was determined that the dangerous position was located at the bottom of the front cutter installation side plate. The maximum equivalent stress value was 178.21 MPa, and the maximum deformation was 0.50 mm. The results showed that the cutterhead material was made of strength and stiffness requirements. Through the lightweight design of cutter head, the maximum stress, maximum deformation and cutter head mass are obtained. The results show that the stress and deformation of the improved cutterhead meet the optimization constraints. The mass reduction is reduced by 8.23% compared with that before optimization, which meets the requirements of lightweight design of cutterhead.关键词：Pipe jacking machine;Cutterhead structure design;Finite element analysis;Optimization
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发布时间：2023-06-09 - 摘要：To solve the problem of excessive collision force caused by traditional crash cushion, a novel guiding crash cushion is designed based on the Singly Periodic Minimal Surface（SPMS） sandwich structure. Firstly, Mathematica is used to explore the influence of parameter changes of a, b and c in the implicit function expression of SPMS on the structure form. Then, the quasi-static compression finite element simulation is carried out. Finally, the vehicle-crash cushion collision model system is established, and the full scale crash simulation is carried out at the speed of 100 km/h. The results show that the change of parameters a and b will make the structure exhibit periodic rotational symmetric changes, and the change of parameter c will change the size of the genus. At last, the optimal values of parameters a, b and c are 1, 0.3 and 0 respectively. Through the full scale crash simulation, compared with the traditional crash cushion, the peak impact force of the novel crash cushion decreases by 37.5% and 18.8% in the frontal and frontal lateral conditions. The new crash cushion can effectively reduce the impact force, and absorb the huge energy under the impact damage, which possesses a good engineering reference value.关键词：SPMS;Guiding crash cushion;Collision resistance;Finite element method
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发布时间：2023-06-09 - 摘要：In order to solve the problem of intelligent identification of coal-rock interface of shearer in fully mechanized coal mining face, a CPS-based coal-rock identification system structure of shearer is proposed. A hybrid system simulation design was carried out for the system, a wireless sensor network system model based on Ptolemy II was constructed, and the design and modeling of the wireless sensor node was completed. The overall simulation of the system was carried out, the experimental data was extracted from the physical prototype system, and the information processing system model was constructed based on the wavelet packet feature extraction and the PSO-BP neural network algorithm. Through the joint simulation of Ptolemy II and Matlab, the reliability of the CPS-based coal-rock identification system is verified.The simulation results show that the average error value of the system co-simulation is larger than the result obtained by the single method simulation, the maximum error is 0.027 924, and the error is still within the allowable range. The results obtained through the simulation of the hybrid system more truly reflect the coal-rock identification process of the shearer, and the prediction accuracy is higher. The research provides a certain contribution to the modeling and simulation of the CPS hybrid system.关键词：Coal-rock identification;Ptolemy Ⅱ;System simulation;CPS;Shearer
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发布时间：2023-06-09 - 摘要：Contact characteristic is an important index to characterize the transmission performance of gears. To clarify the contact characteristic of a nutation transmission with double circular-arc spiral bevel gears, this paper carried out a loaded tooth contact analysis by using the finite element method. Firstly, based on the meshing theory, the tooth surface equation of the double circular-arc spiral bevel gear was derived based on which a three-dimensional CAD model of the meshing gear pair was generated. Secondly, a finite element model of the gear pair was developed in Ansys Workbench to simulate contact status of the meshing double circular-arc spiral bevel gear pair. Finally, the influence of load and installation error on the transmission performance of the gear pair was investigated. The results show that a double-point contact occurs on concave and convex tooth surfaces of the double circular-arc spiral bevel gear, and the stress maximum occurs at the toe of bevel gear. With the increase of load, the contact ratio of the meshing gear increases, while the load distribution coefficient decreases, which improves the smoothness of gear transmission. The installation error affects the contact state of the gear pair in that a negative offset error and a positive nutation angle error may degrade the bearing capacity and the transmission stability of the gears. Thus, they should be reasonably controlled in practical applications.关键词：Double circular-arc spiral bevel gear;Nutation drive;Contact characteristic;Installation error
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发布时间：2023-06-09 - 摘要：With the help of theoretical analysis and numerical simulation, the modal parameters of the two-dimensionally low-order beam elements and high-order beam elements based on the absolute nodal coordinate formulation were studied. The analytical solution of the first-order thickness natural frequency of low-order and high-order beam elements considering the Poisson effect was derived. Based on the generalized characteristic equation, four natural frequencies and natural modes of bending, axial, shear and thickness of the shear beam element based on the absolute nodal coordinate formulation were obtained. Taking a simply supported beam structure as an example, the effects of the polynomial displacement field of the shear beam element on the four natural frequencies and natural modes of bending, axial, shear and thickness were analyzed. The results show that the polynomial displacement field of the shear beam element needs to introduce both the horizontal and vertical high-order terms x~2 and y~2. They mainly affect the bending and axial modal parameters, but have little effect on the shear and thickness modal parameters, and first-order thickness natural frequencies of the lower-order and higher-order beam elements is relatively close to the derived analytical solutions of first-order thickness natural frequencies.关键词：Absolute nodal coordinate formulation;Polynomial displacement field;Natural frequency;Natural mode;Shear deformable beam element
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发布时间：2023-06-09 - 摘要：Improving the design process of shaft parts and improving the optimization index of shaft parts in the mechanical system can effectively improve the use performance of the entire equipment, while saving design time and ensuring design efficiency. By summarizing the research status and progress of shaft parts, a comprehensive analysis of the traditional design criteria, parametric design and optimization design of shaft parts has been carried out, and the main problems in the design process of shaft parts have been discovered. Suggestions on the design process of shaft parts based on analysis of working conditions, closed-loop design to achieve multi-objective optimization, establishment of an integrated design platform and system for shaft parts, and use of digital twins for advanced design are proposed, and the shaft is summarized and prospected. The future development trend of similar parts design. This provides an important research direction for realizing the comprehensive design of shaft parts, and also provides ideas for the intelligent development of shaft parts.关键词：Shaft parts;Design criteria;Parametric design;Optimization design;Multi-platform integration
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发布时间：2023-06-09 - 摘要：The traditional steering knuckle durability test bench can only carry out uniaxial loading test, which cannot fully simulate the stress state of steering knuckle under actual road conditions. To solve it, a durability test system for steering knuckles simulating real-time road conditions and four-axis loading was proposed. Firstly, the three-dimensional model of the mechanical part of the test system was constructed, column strength is calibrated and the key hardware was selected. Then, the modal analysis is carried out by ANSYS Workbench, and the first six modes and natural frequencies of the test system are obtained. Through theoretical calculation, the external excitation frequencies transmitted by the tire to the steering knuckle are 8.47 Hz and 104.4 Hz, which are not consistent with the inherent frequency of the mechanical subsystem system. This verifies that the test system does not produce resonance in the standard loading frequency range. Finally, the experimental system was built and tested.The collected data were subjected to FFT spectrum analysis by using MATLAB. It is concluded that the maximum error of loading force is 0.95 kN, far less than the maximum allowable error of ± 2.5 kN, and the average error of frequency is 1.35 %. The results show that the performance of the steering knuckle durability test system meets the requirements and can simulate the actual working conditions, which provides a reliable theoretical basis for the steering knuckle durability test.关键词：Steering knuckle;Durability;Test system;Vibration analysis;ANSYS
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发布时间：2023-06-09 - 摘要：Large welding structures have been widely used in various major equipment fields. Life evaluation of welding structures is very important for equipment safety.The fatigue life assessment methods including nominal stress method, notch stress method, hot spot stress method and equivalent structural stress method are summarized for large welded structures. The basic principles, advantages and disadvantages of various methods are compared and analyzed. The results show that the nominal stress method is simple and convenient, and can be used for simple welding structure analysis in various fields; the hot spot stress method is widely used in the field of marine ships; the notch stress method is complex in modeling and solving, and it can be used for both fatigue analysis of butt weld toe and weld root; the equivalent structural stress method is mesh insensitive, and can unify the application of various welded joints by a main SN curve, and has great potential application for engineering. The fatigue life assessment of large welded structures application in the fields of rail transit, ships, bridges, construction machinery and vehicles are introduced. The main difficulties and problems in the fatigue life prediction of the large welded structures at the emerging stage are analyzed. It provides references and ideas for the development of fatigue life evaluation methods for the large welded structures in the future.关键词：Fatigue life;Welding structure;Fatigue assessment method;Review
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发布时间：2023-06-09 - 摘要：Based on the practical problem of fatigue life prediction of landing gear, the fatigue life prediction model of landing gear components with surface treatment was studied. The calculation process of the traditional local stress-strain method was introduced, and the factors that affect the local stress-strain method for fatigue life prediction were systematically explained; The actual engineering research shows that the main factors for predicting the fatigue life of landing gear by using the local stress-strain method are surface treatment and surface roughness. By modifying the strain-life curve, a model for predicting the fatigue life of landing gear components is proposed. The two calculation examples show that the predicted results are in good agreement with the experimental results, and the proposed method for revising the strain-life curves under different surface conditions is reasonable.关键词：Landing gear;Local stress-strain method;Strain life curve;Life prediction
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发布时间：2023-06-09 - 摘要：In order to evaluate the influence of the thickness of the stent on the fatigue strength after implantation of the blood vessel, we established a two-way fluid-solid coupling model of the blood vessel、stent and the blood in this paper. The ANSYS finite analysis software was used in this paper to simulative analysis the fatigue performance of stent after implantation, the coupling calculation of structural solid mechanics analysis and fluid dynamics analysis is realized, and the numerical results of the stent under a blood pulsating load are obtained. According to the simulation results, the fatigue performance of the implanted stent is evaluated by Goodman criterion and dynamic safety factor. The results show that the multi-component nature of blood has a greater impact on the stress fluctuation of the stent; the thickness of the stent has almost no effect on the stress distribution of the stent, but has a greater impact on the fatigue performance.关键词：Finite element;Fluid-solid coupling;Fatigue;Goodman criterion;Dynamic safety factor
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发布时间：2023-06-09 - 摘要：Nuclear power plants should be strictly protected against earthquakes. Especially in nuclear power pressure vessels, there are a lot of dissimilar metal welded joints（DMWJ）. They are the weak link owing to their highly heterogeneous microstructure; mechanical; thermal; and fracture properties, and some defects that occur at different positions within the DMWJs. To ensure the safety of nuclear power pressure vessels, it is important to examine the fracture behavior of DMWJ in detail. In addition to the earthquake loads, constraint is an important factor affecting the fracture behavior of DMWJ. To understand this behavior, both constraint and earthquake loads must be considered. In this study, taking nuclear safe end DMWJ as the research object, four single edge-notched bend（SENB） specimens with central crack under different constraints were selected. Different vertical earthquake loads under five earthquake intensities and three actual earthquakes were applied to the specimen respectively by mass acceleration application method. The fracture behavior of DMWJ under various vertical earthquake loads and the interaction between vertical earthquake load and constraint were numerically simulated. The results showed that with the increase of earthquake intensity, the J-R curve of DMWJ gradually decreases. In contrast to the DMWJ with high constraint, the decrease of J-R curve of the DMWJ with low constraint is more obvious. It is related to the fracture mode of DMWJ under different constraints. Under the actual earthquake, the change of J-R curve is related not only to the earthquake magnitude, but also to the acceleration time history curve of earthquake wave.关键词：Earthquake load;Constraint effect;Dissimilar metal welded joint;Fracture behavior;Vertical earthquake
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发布时间：2023-06-09 - 摘要：Taking the rotor system supported by angular contact ball bearing as the research object, the dynamic model of rotor bearing system is established by using Lagrange equation. Based on the Archard wear model, the calculation model of wear depth of bearing raceways considering lubrication effects is presented. The wear depth is introduced into the system dynamics model as the bearing clearance. The dynamic characteristics of rotor-bearing system and the evolution of bearing wear are carefully analyzed taking into account the rotor speed, bearing preload and disc position. The results show that the influence of bearing wear on dynamic characteristics of rotor-bearing system is closely related to rotor speed and bearing preload. Changing disc position does not lead to the significant variation of dynamic characteristics of rotor-bearing system with wear depth of bearing raceways. The rotor speed significantly affects the bearing wear, the bearing preload has very limited effect on bearing wear, and the variation of the disc position results in the weak difference of wear depth of bearings.关键词：Rotor-bearing system;Angular contact ball bearing;Bearing wear;Bearing preload;Dynamic characteristics
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发布时间：2023-06-09 - 摘要：Debonding between flange and skin is the dominate failure mode of stiffened composite panels which are widely used in modern aircraft. The influence of internal cladding layer in hat stringer on the onset of debonding is investigated experimentally and numerically. Cohesive elements are used to simulate the adhesive layer between skin and flange and Hashin’s failure criterion is adopted to determine damage initiation of composite layers in the numerical simulations. The process of damage initiation, propagation and failure of the stiffened composite panels was simulated in detail. A good agreement between tests and numerical prediction was observed.
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发布时间：2023-06-09 - 摘要：In order to solve the problems of dynamic response and structural vibration suppression of aircraft bevel gear thin-walled spoke plate, an optimal design scheme of damping pass structure was proposed. Taking a certain type of aeronautical spiral bevel gear as an example, the model of spiral bevel gear was established. The natural characteristics of the gear were calculated by Lanczos method, and the frequency margin between the first six natural frequencies and the excitation force was analyzed. The dynamic response characteristics of radial plates with different holes and their suppression effect on vibration transmission were studied by means of modal superposition method. The parameters of radial plate pass structure are optimized by orthogonal experiment design and simulation analysis. The results show that under the condition of the same area and the same number, the vibration responses of triangle, round, pillow and waist shapes decrease in turn. The optimized waist pass can effectively suppress vibration transmission and improve the smoothness of bevel gear transmission.关键词：Spiral bevel gear;Modal analysis;Orthogonal test;Dynamic response
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- 95
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发布时间：2023-06-09 - 摘要：In order to solve the problem that the driving wheel teeth are easy to break in the harsh working environment, this paper used RecurDyn software to establish the virtual prototype model of the driving wheel crawler mechanism with different number of teeth, and used the finite element software WorkBench to make the driving wheel teeth flexible, and established the rigid-flexible coupling model with the driving wheel teeth as the flexible body. Under the typical working conditions of the Spreader, the driving wheel was simulated, and the contact load between the driving wheel and the crawler shoe and the stress nephogram of the driving wheel teeth with different number of teeth are obtained. On this basis, the fatigue life of the nine tooth driving wheel teeth was analyzed. The results show that: with the increase of the number of driving wheel teeth, the maximum stress in the root area of the driving wheel teeth will decrease; the root area of the driving wheel teeth is the weakest position of the teeth, and the fatigue life is the shortest under the steering condition. The research results provide the basis for the design optimization of the driving wheel.关键词：Spreader;Driving wheels;Rigid-flexible coupling;Dynamic stress;Fatigue life
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- 115
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发布时间：2023-06-09 - 摘要：Car body gravity deformation analysis by finite element method, and roof cross members are easy to have big gravity deformation. By researching on the relationship between gravity deformation and part thickness, camber, rib shape, it can be concluded that gravity deformation will be reduced a lot by optimize part camber and rib shape. Roof cross member gravity deformation reduced 48% by optimization the structure at last. It can identify the quality risk in advance by finite element virtual analysis of part manufacturing deformation during body process simultaneous engineering phase, and it is helpful to instruct the part design and reduce manufacturing cost.关键词：Roof cross member;Finite element;Gravity deformation;Structure optimization
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发布时间：2023-06-09 -
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