最新刊期
卷 45 ， 期 6 ， 2023
- 摘要：A large number of complex features need to be extracted for the fault diagnosis of wind turbine rolling bearings. A parallel bearing fault diagnosis model based on attention mechanism, ResNext network and long short-term memory (LSTM) network was proposed. Firstly, the collected one-dimensional vibration signal was preprocessed; then it was input into the model in two ways to extract features, and one of them was input into the ResNext module embedded in the attention mechanism. The attention mechanism can increase the weight of important features and reduce model operations. The other channel was input to the LSTM network to extract the dependence of the vibration signal on the time series. Finally, the two extracted features are fused and input to the Softmax layer for fault classification. The experimental results show that, compared with the current bearing fault diagnosis method based on deep learning, the proposed method performs better in bearing fault classification accuracy.关键词：Fault diagnosis;Attention mechanism;ResNext;LSTM
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发布时间：2024-06-07 - 摘要：Aiming at problems that traditional fault diagnosis methods need to extract features manually and the recognition rate is low, a VMD-CWT-CNN model based on variational modal decomposition (VMD) and continuous wavelet transform (CWT) combined with convolutional neural network (CNN) is proposed for rolling bearing fault diagnosis. Firstly, the bearing vibration signal is decomposed into multiple modal components with different center frequencies by VMD. Secondly, the modal components are calculated by CWT and transformed into two-dimensional time-frequency diagram. Finally, the time-frequency diagram is input into the EfficientNet convolution neural network after structure cutting, the features are automatically extracted, and the fault diagnosis of rolling bearing is completed. Using the method proposed, the average accuracy of multiple experiments on 10 types of bearing fault data from Case Western Reserve University is 99. 86%, which can effectively complete the feature extraction of rolling bearing signal and the accurate diagnosis of damage degree.关键词：VMD;CWT;Time-frequency diagram;CNN;Fault diagnosis
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发布时间：2024-06-07 - 摘要：In order to accurately and timely judge the fault location of pumping unit and change the inefficient manual fault diagnosis mode, a fault identification method of pumping unit based on Mahalanobis Taguchi system was proposed . Firstly, the geometric and shape characteristics of the indicator diagram were analyzed. Secondly, feature extraction of indicator diagram was carried out by combining global and local features. Then , Mahalanobis distance was used as the measurement index, and the sensitive feature variables of each fault were screened by constructing and modifying feature subset. Finally, the multi-classification Mahalanobis Taguchi system was established to realize fault identification and compared with the traditional manual identification method, and the feasibility and effectiveness of the proposed method was verified by taking the oil well data in the Shixi operation area of Karamay as an example.关键词：Global features;Local features;Fault diagnosis of pumping unit;Indicator diagram;Mahalanobis Taguchi system
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发布时间：2024-06-07 - 摘要：In the actual operation of bulb continuous unit, the rotor-runner system is easy to form friction fault between rotating parts and fixed parts allected by extermal incentives, which greatly affects the safe and stable operation of unit. Aimed at the problem of axial friction with fault receptor components, the unbalanced magnetic tension model under rotor composite eccentricity is conshructed, the vibration model of rotor-runner coupled bending torsional vibration with the excitation of multi-source, and its diferential motion equation are established. The dierence of vibration characteristics for converter system is studied and the nonlinear vibration characteristics of system in excitation curent, rotor and runner mass eccenticity are discussed. The results show that failure inereases the unsteady motion range of rotor and runner, causing the system to produce adverse vibration and occasion malfunetion. Meanwhile, the rotor under the same operating conditions and parameters shows a greater amplitude strength than the runmer, which should be more attention. With considering the torsional degrees of freedom, the rotor amplitude amplifies under mass eccentricity variations, resulting in the rub-impact malfunction. In addition, when the runner mass eccentricity is developed to a certain extent, the uncertain random hydraulic force at the blade will induce instability of system. The results can provide useful references for safe operation and stability analysis of bulb tubular unit.关键词：Oil receiver;Coupled bending-torsional vibration;Bulb tubular unit;Compound eccentricity;Excitation current
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发布时间：2024-06-07 - 摘要：In view of the complexity of the surface instability noise mechanism of the braking system, scholars have carried out a lot of research from the theoretical and experimental perspectives. The purpose was to reveal the instability and nonlinear response mechanism of rough micro contact surfaces to modal coupled self-excited vibration systems. For the modeling of contact surface stiffness, the fractal theory that can simulate the fractal characteristics of machined surfaces was introduced, and the model was embedded into the two-degree-of-freedom brake system model, thus a dynamic model of the brake system containing microscopic contact characteristics parameters was established. The influence of fractal parameters on the stability and nonlinear response of the system was analyzed. Theoretical and experimental studies have found that both fractal dimension D and fractal roughness G have an important influence on the braking stability of the system. This study can provide a reference for the dynamic analysis of similar micro contact effects on macro mechanical systems in engineering.关键词：Rough surface;Self excited vibration system;Response;Nonlinear
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发布时间：2024-06-07 - 摘要：Aiming at the subtle fault features of the wind turbines rolling bearing, the fault signal is nonlinear, non-stationary and contains noise interference, and the fault signal has the characteristics of space and time feature information, a space-time fusion convolutional shared weight long short-term memory network (CSwLSTM) model based on one-dimensional convolutional neural network (1D-CNN) and the shared weight long short-term memory network (SWLSTM) was proposed for wind turbine rolling bearing fault diagnosis. Using the Western Reserve University rolling bearing dataset for experiment, compared with the convolutional long short-term memory network (CLSTM) model and convolutional gated recurrent unit network (CGRU) model with the same structure, CSWLSTM model had a significant improvement in the convergence of the training dataset. The training time was reduced by 39.9% and 19.0%, respectively. The model parameters were reduced by 63. 3% and 53.4%, respectively. The accuracy was increased by 1.0% and 1.5%, the precision rate was increased by 1.0% and 1.7%, and the recall rate was increased by 0.9% and 1.0% on the test dataset, respectively. The simulation experiment results show that the CSWLSTM model has good application potential in the wind turbine rolling bearing fault diagnosis.关键词：Wind power;Fault diagnosis;Rolling bearing;Shared weight long short-term memory network;One-dimensional convolutional neural network
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发布时间：2024-06-07 - 摘要：In this paper, the energy absorption performance of the variable density multilayer gradient lattice metal vibration damping structure was studied by experimental and finite element analysis. Firstly, two kinds of gradient lattice structures of variable diameter BCC (DBCC) and variable angle BCC ( ABCC) were designed based on the body-centered cubic ( BCC ) structure, and the multi-layer gradient structures of 304 stainless steel were prepared by selective laser melting process. Then, the compression and energy absorption properties of the gradient lattice structure and the uniform lattice structure were comparatively studied. Both the finite element simulation and the experimental results indicated that for the DBCC structure, the low-density layer drived the high-density layer to collapse layer by layer since the compression was started. A high energy absorption efficiency was obtained in the small strain stage. However, stress distribution was uneven, resulting in a significant decrease in its mechanical properties and overall energy absorption rate compared with the uniform structure. The ABCC structure performed a strong compressive performance in the stage of small strain, and was collapsed layer by layer in the large compression strain stage, thus improved the energy absorption performance to a certain extent. In addition, increasing the gradient rate of the structure effectively improved the elastic modulus and energy absorption characteristics of the ABCC structure.关键词：Gradient lattice;Quasi-static compression;Selective laser melting (SLM) process;Mechanical properties;Energy absorption properties
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发布时间：2024-06-07 - 摘要：In order to study the influence of compact tensile (CT) specimen size on dynamic fracture toughness test, a dynamic fracture test of 2112T4 aluminium alloy CT was carried out based on a split Hopkinson tie bar (SHTB) device. The dynamic fracture toughness of the specimen was calculated by digital speckle correlation method( DSCM) , and the correctness of this method was demonstrated by comparing the results of strain gauge method. The influence of different sizes of specimens and loading hole locations on dynamic fracture toughness was studied. The results show that the smaller the value of W/B, the smaller the dynamic fracture toughness value of CT specimens and the slower the decreasing trend. For samples of different sizes with the same W/B value, the dynamic fracture toughness gap is small. Changing the center distance of loading round hole has little influence on the experimental results of dynamic fracture toughness.关键词：Compact tensile specimens;Digital speckle correlation method;Dynamic loading;Fracture toughness;Split hopkinson tie bar
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发布时间：2024-06-07 - 摘要：Filled rubber material is widely used in engineering vibration isolation structures. Accurately describing its hyperelastic properties is very important for accurate prediction of service performance of the engineering structures. Three basic mechanical tests including the uniaxial tensile (UT) , uniaxial compression (UC) and simple shear (SS) test were performed on an isolation rubber to character its hyperelastic mechanical behavior. Abilities of four commonly used hyperelastic constitutive models in predicting other kinds of deformations were discussed with incomplete data of these three basic mechanical tests. Three error evaluation indexes and a fitting goodness coefficient R were proposed to evaluate the fitting accuracy of each constitutive model. Finally, the applicability of different constitutive models under different experimental conditions was discussed and corresponding suggestions were given.关键词：Vibration isolation rubber material;Hyperelastic constitutive models;Material mechanical tests;Fitting accuracy;Applicability
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发布时间：2024-06-07 - 摘要：In order to comprehensively evaluate the feasibility of the engineering application of titanium alloy, the comparative investigations on mechanical performances including the fatigue performance of both aircraft structural maintenance parts and material were carried out based on the different processing methods in which titanium alloy and typical structural samples were respectively made by the selective laser melting(SLM) and traditional mechanical process. As the results, the tensile, shear, and impact properties of titanium alloy by SLM method were excellent at room temperature, and the relative error of various mechanical properties is less than 10% when compared with titanium alloy plates by mechanical process. The aforementioned typical structural samples manufactured by SLM also have the strongest performance of mechanical processing, the relative error of static strength is less than 5%, and the maximum relative error of fatigue strength is 12.9%, titanium alloy typical structural parts manufactured by SLM also have the same level performance of mechanical processing. The reinforcement effect of titanium alloy aircraft structural maintenance parts manufactured by SLM is equivalent to or even slightly better than that of high strength steel by mechanical process. The research shows that the titanium alloy structure made by SLM also meets the basic installation requirement and use.关键词：Selective laser melting;Titanium alloy;Aircraft maintenance;Static strength;Fatigue performance
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发布时间：2024-06-07 - 摘要：Machined surface quality of Al-Si alloy aviation structural part affects its service performance. The cutting parameters have a strong correlation with the formation of surface quality, and surface quality can be improved by adjusting the cutting parameters. Single factor method was used to test the turning of ZL114A Al-Si alloy. To explore the influence law ofcutting parameters and tool nose radius on the surface quality and cutting performance of the workpieces, surface roughness, surface residual stress, surface morphology and tool wear of the specimen were observed and analyzed with cutting force and cutting temperature. The results show that the surface roughness of ZL114A Al-Si alloy is most sensitive to the change of turning depth. The machined surface residual stress is compressive stress, which is most sensitive to the change of tool nose radius. There are obvious tool marks on the surface of the workpiece after turning, accompanied by the appearance of pear ditch. The change of spindle speed has the greatest influence on tool wear.关键词：ZL114A Al-Si alloy;Surface roughness;Surface topography;Residual stress;Cutting force
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发布时间：2024-06-07 - 摘要：Compact tension specimens were fabricated with Ti-6Al-4V titanium alloy by selective laser melting. Some specimens were heat treated and some were hot-isostatic pressed (HIPed). Half of these specimens in three conditions were polished. Fatigue crack growth (FCG) test was conducted to obtain FCG data, and to research into the effect of post-processes. The microstructure and fractography were observed to find possible reasons for FCG variaton. The results indicated that, FCG preformance of as-built SLM Ti-6Al-4V is inferior to conventional material due to the fine needle martensitic structure and large residual stress. Both heat treatment and hot-isostatic pressing lead to thicker o phase and more ß phase, diminsh or even eliminate the residual stress, and improve FCG performance signifcantly. FCG rates of heat treated and HIPed speicmens are comparable to those of Ti-6Al-4V fabricated by conventional techonology. When the crack length and stress intensity factor are larger than a certain value, surface polishing shows haldly any effect.关键词：Selective laser melt;Heat treatment;Hot-isostatic press;Surface condition;Fatigue crack growth
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发布时间：2024-06-07 - 摘要：Wind turbine blade pitch fault is easy to cause unstable ultra-high load, which can lead to structural failure and damage. Firstly, the aerodynamic characteristics of NREL 5 MW wind turbine blades with pitch fault/success were analyzed based on the computational fluid dynamics method. Then, the two-way strong fluid-structure coupling and bending analysis were used to study the state of blades with pitch fault under typical azimuths. The results show that average flapwise torque of the blade with pitch fault under the cut-out wind speed is 13. 8 times that of the blade with successful pitch, and the flow field wake of the former is more obvious. The fluctuation range of blade flapwise torque under two-way strong fluid-structure coupling is significantly wider than that without fluid-structure coupling, and the maximum tip displacement of the blade with pitch fault is 14. 1 times that of the blade with successful pitch. For the four typical azimuth angles of 0°, 60°, 120°, and 180°, the bending moment, tip displacement, bending degree, end effect, wake range and strength of the blade with pitch fault gradually decrease with the increase of the angle. Buckling analysis reveals that the buckling factor increases with the enlargement of azimuth angle, and the first-order buckling factor of 180°azimuth is 20.2% higher than that of 0° azimuth.关键词：Wind turbine;Pitch fault;Fluid-structure coupling;Aerodynamic characteristic;Structural response;Buckling analysis
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发布时间：2024-06-07 - 摘要：The standard guardrail was topologically optimized in the longitudinal stretch direction, the optimal force transmission path was obtained, and the initial section of the new type guardrail was extracted. Then, ultra-high performance concrete material was applied to the collision analysis using the guardrail-vehicle coupling finite element model verified by the actual vehicle experiment. In order to obtain the optimal section parameters that minimize the acceleration of vehicle centroid and the maximum dynamic displacement of guardrail, taguchi method combined with physical programming method was used for multi-objective robust design considering the influence of uncertain factors. Finally, the simulation results of the optimized guardrail and the standard guardrail are compared, and the results show that the crashworthiness of the optimized new guardrail can be comprehensively improved. The work has practical engineering significance.关键词：Topological optimization;Taguchi method;Satisfaction;Physical programming method;Multi-objective robustness;Ultra-high performance concrete
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发布时间：2024-06-07 - 摘要：Taking the welded rotor of steam turbine as the research object, a two-dimensional axisymmetric finite element model of multi-layer and multi-pass TIG are welding process was established. By using the double ellipsoidal heat source model, the element birth and death method and the Dflux heat source movement subroutine, the welding process was numerically simulated, and the distribution of temperature field and stress field and the optimization method of welding process were analyzed. The results show that a complex heat load curve was formed after repeated heating and cooling during the multi-layer and multi-pass welding process, and the average stress level of the matrix on both sides increases, which improves the uneven stress distribution of the welds. The stress level of the weld zone of the three passes in the same layer decreased slightly compared with the two passes, but the width of the high stress level zone increased, and the welding deformation increased by about 7.9% at the top and bottom of the groove. The research suggests that the number of welding passes in the same layer has an important influence on the stress and deformation of the welds, which should be selected reasonably.关键词：Multi-layer and multi-pass TIG;Numerical simulation;Stress field;Temperature field;Process optimization
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发布时间：2024-06-07 - 摘要：Time-dependent failure probability function(TDFPF) of parameters is one of the key problems of structural time-dependent reliability-based optimization. The accuracy and efficiency of TDFPF estimation determine the effect of time-dependent reliability-based optimization of structures. In this work, a weighted importance sampling (WIS) approach was proposed for theTDFPF estimation based on the concept of the composite limit states. The proposed method extends importance sampling to obtain the estimation of the TDFPF with only one reliability analysis, avoiding repeated reliability analyses. To verify the accuracy and efficiency of the proposed method, numerical examples and industrial robot reducer examples are given and solved by the proposed method. The results indicated that the proposed method has wide applicability, high efficiency in obtaining the satisfactory estimation of the TDFPF.关键词：Time-dependent reliability;Time-dependent failure probability function (TDFPF);Weighting approach;Importance sampling method;Stochastic simulation
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发布时间：2024-06-07 - 摘要：In order to improve the sealing performance of the beam seal, the structural parameters of the beam seal were used as design variables, and the optimization design was carried out. Firstly, a finite element model of the beam seal with elliptical are groove was established. Secondly, taking the maximum contact pressure of the sealing contact surface as a quantitative indicator of sealing performance, the sensitivity analysis of five structural parameters that affect the sealing performance of the beam seal was carried out, and the structural parameters with significant effects were selected to establish a second-order response surface model. Finally, the genetic algorithm was used to solve the multi-objective optimization of thel response surface model, and the effectiveness of the optimization results was verified by the finite element numerical simulation. The results show that the three parameters of the ellipse semi-major axis, the elliptic semi-minor axis and the nominal width of thefirst seal have a more significant impact on the sealing performance of the beam seal. When the three values are taken as 1. 051 mm, 0. 540 mm and 0. 060 mm respectively, the sealing performance of the beam seal can be effectively improved.关键词：Beam seal;Sensitivity Analysis;Response surface model;Genetic algorithm;Multi-objective optimization
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发布时间：2024-06-07 -
RESEARCH ON STEADY STATE AND DYNAMIC PERFORMANCE OF TRANSMISSION SYSTEM BASED ON SHIFT SHOCK PROBLEM
摘要：In order to solve the problem of abnormal noise when the car is shifted, the dynamic model of transmission system with 7 degrees of freedom is established. The model contains flywheel, clutch, gearbox, transmission shaft, drive shaft and tire. Using the established mathematical model, natural frequency and main vibration shape of the transmission system can be obtained. With the help of Adams software to build a multi-body dynamics model of the transmission system, and then perform modal analysis calculations on the model, the main kinetic energy that affects the shift shock is concentrated in the flywheel, and the main potential energy is concentrated in the drive half shaft. Starting from the excitation, constructing the clutch vibrationdamping characteristic model, and analyzing the sensitivity of the clutch clearance angle, it can be concluded that the larger the clearance angle, the more obvious the shift shock. Therefore, the optimized design is carried out for the flywheel inertia, drive axle stiffness, and clutch clearance angle, and is installed on the real vehicle for verification. The results show that the shift shock of the vehicle is effectively improved by installing the optimized components. The established model and analysis method have guiding significance for improving the shift shock.关键词：Shift shock;Mathematical model;Multi-body dynamics model;Modal analysis calculation;Clearance angle- 3
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发布时间：2024-06-07 - 摘要：The line contact elasto-hydrodynamic lubrication (EHL) phenomenon generally exists in key parts of mechanical systems e. g. bearings, gears, the lubricant oil film between the contact interfaces acts as a spring and damper, and the frictional heat generated by the contact between the lubricant and the solids changes the rheological properties of the lubricant, then the dynamics characteristics of the contact pair are affected. Based on the basic principles of elastohydrodynamic lubrication heat transfer and dynamics, the coupling model of line contact thermoelastohydrodynamic lubrication and dynamics was established. By using the relationship between the stiffness and the contact body approach amount under steady state conditions, the part affected by the stiffness force under transient contact was separated and the damping parameter was obtained. Based on the above model, the contact oil film characteristics and the dynamics characteristics of thermal elastohydrodynamic lubrication were studied. The results show that the lubricating oil film temperature obviously increased with the increasing applied load and entrainment velocity, which influences the rheological properties of lubricant and further affects the dynamics characteristics during the loading process. At light load and low speed, the influence of thermal effect on elastohydrodynamic lubrication stiffness and damping is not obvious. With the increase of load and entrainment speed, the thermal effect of elastohydrodynamic stiffness and damping is greater than the calculated results under isothermal conditions, and the influence of thermal effect is more obvious with the increase of speed.关键词：Line contact;Elastohydrodynamic lubrication;Thermal effect;Stiffness;Damping
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发布时间：2024-06-07 - 摘要：Propulsion system is an important part of shield machine, and its stiffness will affect the propelling and steering function. In order to obtain the effective parameterized stiffness model of shield propulsion system, and to accurately describe the static stiffness of shield propulsion system in the whole working space, the static stiffness modeling method is studied. The physical model of shield propulsion system was established and its movement and force were analyzed. The stiffness model of shield propulsion cylinder was established by material mechanics formula and the relation between deformation of the end of themechanism in each direction and force or moment was constructed based on the principle of virtual displacement. The calculation formula of total stiffness matrix of shield propulsion system was obtained by superposition principle. The accuracy of the static stiffness model was verified by finite element method and its sensitivity was analyzed. It provides theoretical basis for structural design optimization and research analysis of shield propulsion system.关键词：Virtual displacement principle;Shield propulsion system;Mechanism static stiffness;Finite element method;Sensitivity analysis
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发布时间：2024-06-07 - 摘要：The multi-axis manned centrifuge is an important device for training pilots' directional cognitive ability and overcoming illusions. Its intensity check is a necessary part of structural design. The traditional quasi-static static analysis method can only directly analyze the structural strength problem of no more than two-axis nested rotation, but the multi-axis manned centrifuge has three or more than three-axis nested rotation. The flexible multi-body dynamics method can be used to analyze and determine the strength of the multi-axis rotating structure of the motion path, but the calculation time is long and the resource consumption is large, so it is difficult to fully assess the intensity of the structure. In this paper, a multi-axis centrifuge intensity check method based on multi-body dynamics combined with random sampling and finite element calculation is proposed. The calculation results can be obtained in a relatively short period of time, it is highly efficient and feasible, which is conducive to improve the accuracy of structural intensity verification of multi-axis nested rotating equipment, and provides important support for its structural design.关键词：Multi-body dynamics;Multi-axis rotation;Intensity check;Random sampling
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发布时间：2024-06-07 - 摘要：In order to study the contact stiffness of the bonding surface in more detail from the perspective of fractal theory, on the basis of the M-B fractal model and the Hertz theory, a domain expansion factor is introduced to represent the fractal dimension to establish the normal and tangential contact stiffness fractal models of the bonding surface, respectively. The model comprehensively considers the effects of load, fractal dimension and material parameters on the contact stiffness. At the same time, the change trend of the contact stiffness of the joint surface and each parameter is obtained through numerical simulation.The change trend of normal contact stiffness and normal load is the same, which is opposite to the fractal characteristics and length scale coefficient, but the change trend of the fractal dimension is more complicated, no longer monotonic. The changetrend caused by tangential contact stiffness and the above parameters is similar to that caused by normal contact stiffness.关键词：Contact stiffness;Domain expansion factor;Fractal model;Micro contact area distribution function;Numerical simulation
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发布时间：2024-06-07 - 摘要：Two-stage reciprocating small oil-free air compressors have been widely used in various fields due to their high exhaust pressure and low power consumption, but the vibration and noise problems seriously affect the comfort of use. In order to improve the compressor vibration, the theory of dynamic balancing of a two-stage reciprocating air compressor was developed and a virtual prototype simulation was carried out using Adams software to establish an objective function to optimize the balance block counterweight of its crankshaft-piston system. Subsequently, in view of the close connection between the motor and thel compressor structure, the theoretical study and analysis of the dynamic balance of the crankshaft piston system and the motor rotor as a whole was carried out, and the dynamic balance scheme was further improved. Based on the above dynamic balance theory, vibration and noise tests are carried out and the noise are all reduced to a certain extent, verifying the reasonableness of the dynamic balance theory of the two-stage reciprocating small air compressor.关键词：Reciprocating compressor;Crankshaft piston system;Dynamic balance;Virtual prototypes;Motor rotor
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发布时间：2024-06-07 - 摘要：The traditional fatigue life prediction method Miner theory ignored the damage caused by stress below the fatigue limit to the component, resulting in a large error in fatigue life prediction. In order to calculate the damage caused by the stress below the fatigue limit to the component, according to the loading stress and its characteristics of the damage, the partial large membership function in the semi-trapezoidal and trapezoidal distribution is selected, and the degree of damage caused by the stress below the fatigue limit is characterized by its membership. The damage phenomenon reflected by this membership functionis regarded as a gray system, and an equally spaced GM(1,1) model of stress and membership is established. Then, it fitted its function expression and combined it with the membership function to calculate the damage caused by stress below the fatigue limit. Two sets of 41Cr4 multi-level loading experimental data were used to verify and evaluate the proposed new model, and the error between the estimated results and the experimental results was about 7.5%. Compared with Miner theory, the predicted fatigue life model of the equally spaced grey system, and the grey Verhulst predicted fatigue life model, this model improves the fatigue life prediction accuracy.关键词：Membership function;Grey system theory;Fatigue limit;GM(1,1) model;Fatigue life
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发布时间：2024-06-07 - 摘要：With respect to the fatigue failure of typical bolted joints of aircraft subjected to the random block spectrum, the micro-observation technology was used to analyze the macro and micro fracture morphology characteristics, and to reveal the fatigue failure mode and micro failure mechanism of bolted joint. Combined with the fatigue load spectrum and micro fatigue strip characteristics of the bolted joint, the fatigue crack propagation and initiation life were quantitatively derived based on the Paris formula, and the relation between fatigue crack length to the load cycle number and flight hour are respectively developed. The results show that the fatigue crack of the bolted joint originates from the bottom surface of the bolted joints with stress concentration, showing the multi-source mode. The fracture surface possesses typical fatigue characteristics, including crack source zone, crack growth zone and instantaneous fracture zone. It is also found that the two-stage function formula can properly characterize the evolution law between the fatigue crack growth length to the cycle number and flight time during the whole fatigue life. The fatigue crack growth and initiation life were calculated as 3 147.7 and 615.4 hours, and the configuration and manufacturing process of the bolted joint need to be improved to meet the requirements of safety life design.关键词：Bolted joint;Fatigue failure;Random block spectrum;Fracture characteristic;Failure analysis
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发布时间：2024-06-07 - 摘要：To address the issue of reducing the contact pressure of jack spring in the triaxial random vibration environment of electrical connectors, a finite element model was built to reveal the assembly relation of electrical connector and connection of the contact components. The finite element analysis of triaxial random vibration was conducted by the combination of HyperMesh spring, the two-dimensional joint probability distributions of mean stress and stress amplitude were established, and the equivalent load model was proposed. Based on the Miner cumulative damage criterion, the variations in the fatigue cumulative damage values for the root of the jack spring with vibration time and random vibration stress levels were plotted. The constantthat the contact pressure of the jack spring is decreased due to its increased opening diameter. The plastic deformation occurs and Ansys software. The tri-axial and tri-tangential direction stress power spectral densities at the root of the jack spring were obtained under different vibration stress levels. Based on the principle of minimum distortion energy, the theoretical equivalentcalculate the time-domain load history of the root of the jack spring. Considering the pre-stress imposed on the root of the jack stress power spectral density was achieved. Accordingly, the inverse non-uniform discrete Fourier transform was applied to stress acceleration test of electrical connector was carried out in a tri-axial random vibration environment. The results demonstrate near the root of the jack spring, while the irregular creep appears at the edge of its root end. As the position approaching to the outside, the creep trend becomes stronger and is gradually enhanced from inside to outside.关键词：Triaxial random vibration;Electrical connectors;Finite element method (FEM);Fatigue damage;Plastic deformation
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发布时间：2024-06-07 - 摘要：In order to predict the ductile fracture failure of different high-strength steel plates, the damage parameters of the ductile fracture criterion were calibrated by designing the tensile, shear and fracture failure tests of four high-strength steel plates. The relation between damage parameters and material properties is established by combining test and numerical simulation, so as to reduce the difficulty of calibrating the damage parameters of ductile fracture criterion. In order to verify the universality and accuracy of the criterion in predicting the fracture failure of high-strength steel under different stress triaxiality, through shear, tension bending, bulging test and numerical simulation. The results show that the ductile fracture criterion can better predict the fracture failure of different advanced high strength steels.关键词：High strength dual phase steel;Ductile fracture criterion;Stress triaxiality;Parameter calibration;Numerical simulation
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发布时间：2024-06-07 - 摘要：The riveting process is a frequently utilized technique for joining components in aircraft assembly, but the complex damage and deformation of riveted joints may lead to intricate and unpredictable failure modes during the service phase. In order to thoroughly examine the deformation characteristics, mechanical properties and failure behavior of single-lap composite riveted joints, the three-dimensional Hashin failure criteria and exponential stiffness degradation method was used to establish an asymptotic damage prediction model for composite materials. Riveting forming and quasi-static tensile simulation were performed on riveted parts with different riveting process parameters, and the corresponding simulation results were compared with experimental results. The results indicate that the radial expansion of the rivet shank is non-uniform when subjected to pressure riveting force. Furthermore, the forming damage primarily transpires in the hole wall near the driven head, wherein the fibercrushing and interfacial shear cracks dominate. The uniformity of the hole expansion in the joint with a 4. 82 mm diameter is superior to that of a 4.9 mm diameter, resulting in better ultimate bearing strength. Moreover, the numerical model's displacement-load curve aptly reflects the trend and features of the actual mechanical properties. The predicted ultimate strength level is also comparable to the test results. Notably, the numerical model effectively captures the damage forms and range of fibers and matrix in the micro-morphology on the bearing plane, confirming the validity of the damage prediction model.关键词：Composite material;Riveted joint;Mechanical performance;Failure Mechanism;Damage evolution
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发布时间：2024-06-07 - 摘要：In this study, the concept of energy absorption and collision avoidance of metal tubes in the transportation field is combined with a spherical reticulated shell structure with excellent vibration absorption and impact resistance in the construction field. New energy absorption structures— reticulated tubes (RT), equator skeleton spherical reticulated shells (ES), truss spherical reticulated shells (TR), and thin-walled sphere with round holes (TSH), and sphere-filled RTs-are proposed. In order to compare with the traditional energy absorption structure, aluminium alloy thin-walled tubes are also included in the study. The energy absorption characteristics were studied by drop-hammer impact test, the TSH, ES and TR-filled RTs can produce more prominent filling effect than the corresponding aluminium alloy tubes and significantly improve the carrying capacity, energy absorption, crushing forceefficiency, and specific energy absorption. Compared with the filled aluminum alloy tubes, sphere-filled RTs can not only significantly reduce the impact effect, keep the initial impact peak basically unchanged, but also significantly improve the energy absorption per unit mass. Thus, the TSH, ES, and TR-filled RTs can be new types of lightweight structures which can meet the requirements of lightweight, high energy absorption, and low impact effect.关键词：New energy absorption structures;Filled aluminum alloy tubes;Impact;Energy absorption;Lightweight
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发布时间：2024-06-07 - 摘要：Arc truss is a kind of basic structure commonly used in national economic construction, which has the advantages of light weight, long span and so on. In order to obtain the optimal solution of building are truss quickly and accurately, an improved cooperative search algorithm based on communication speech strategy is proposed. The performance of the improved cooperative search algorithm is verified by typical examples of 3-bar truss and 18 bar truss. The results show that the improved cooperative search algorithm has good convergence speed and robustness. Based on this, the improved cooperative search algorithm is used to optimize the design of building arc truss. The results show that after 46 iterations, the mass of arc truss is reduced from the initial 1 468. 51 kg to 1 284.85 kg, which is 12.51% lower than the initial value. The improved cooperative search algorithm is an optimization algorithm, which provides an efficient algorithm basis for practical engineering optimization problems.关键词：Cooperation search algorithm;Arc truss structure;Communication speech strategy;Optimization algorithm
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- 69
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发布时间：2024-06-07 - 摘要：The amount of cycloidal gear modification is an important factor affecting the evaluation of machining error. At present, a method is proposed to invert the actual modification for a cycloid gear designed by using a composite modification method, where the modification is unknown. By analyzing the composite profiling method for cycloidal gear, the best approximation modification calculation model is constructed with the sum of squared normal errors as the target. And this model is solved by using the modified Powell method to obtain the actual modification parameters of the cycloidal gear. The feasibility ofthis method is verified by measuring the tooth profile of the actual machined cycloidal gear, providing a new way to evaluate the error of cycloidal gear in the case of unknown modification parameters.关键词：Cycloidal gear;Tooth profile detection;Composite modification;Machining error;Actual modification
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发布时间：2024-06-07 - 摘要：A damage identification method based on CMCM and L1 regularization is proposed. Firstly, the basic principle of cross modal method and the characteristics of L2 regularization and L1 regularization are introduced. The proposed method was then validated with a steel frame structure in a laboratory. The results show that the combination of CMCM and L2 regularization can easily lead to misjudgment of undamaged elements, while L1 regularization in CMCM can identify structural damage more accurately. Even if only the first measurement mode is used, the L1 regularization technique can be used to solve the CMCM equation to accurately identify the damage of the frame structure.关键词：L1 regularization;Damage identification;Cross model cross mode (CMCM);Model updating
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发布时间：2024-06-07 -
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