最新刊期
卷 46 ， 期 1 ， 2024
- 摘要：In view of the technical problems in the process of rolling bearing fault diagnosis such as sample processing and identification of faults, a fault diagnosis classification method based on Morlet wavelets and classification and regression tree (CART) was proposed. Firstly, the Morlet wavelet analysis method and moving window method were used to process samples of the measured vibration signal of bearing. Secondly , the variational modal decomposition and feature extraction were performed on the extracted short samples to complete the construction of the training and test sets. Then, the training set was used to train the CART decision tree classification model, while random search and K-fold cross-validation were introduced to obtain the ideal classification model of bearing fault by optimizing the key parameters of the model. The test set validation results show that the method not only achieves effective diagnosis of various bearing faults and performs well in test sets with noise, but also significantly reduces the data length and sampling time of individual samples.关键词：Fault diagnosis;Rolling bearing;Morlet wavelet;VMD;CART decision tree
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发布时间：2024-04-18 - 摘要：In order to determine the damping characteristics of the electromagnetic shock absorber under different working conditions, the theoretical modeling and test of the electromagnetic shock absorber with mechanical rectification device were carried out. Firstly, the dynamie transmission model and electromechanical coupling model of electromagnetic shock absorber were built theoretically, and its dynamics and electrics characteristics are analyzed. Secondly, a test bench of electromagnetic shock absorber is built from the engineering point of view, and the experimental study of its damping characteristies under different working conditions was carried out. Finally, the theoretical simulation results were compared with the test results. The results show that theoretical results and test results have the same variation trend. The equivalent damping coefficient of electromagnetic shock absorber will decrease from 1 208 N・s/m to 496 N・s/m when the load resistance increases from 5 Ω to 100 Ω. In addition, the results of decrease of equivalent damping coefficient from 874 N・s/m to 660 N・s/m when the increase of excitation frequency from 0.5 Hz to 2 Hz or the increase of excitation amplitude from 20 mm to 40 mm.关键词：Electromagnetic shock absorber;Vibration energy harvesting;Mechanical rectification device;Damping characteristic
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发布时间：2024-04-18 - 摘要：In order to solve the problem of rolling bearing fault diagnosis, an intelligent diagnosis model IHHO-LSTM was proposed, which combined the improved Harris hawks optimization (HHO) algorithm with long short-term memory (LSTM) network. HHO algorithm was prone to fall into local optimum and slow convergence in the solution process. Based on thesc problems, Cauchy distribution function and simulated annealing (SA) algorithm were introduced to expand the universality of global search and avoid falling into local optimization. The improved HHO was used to quickly determine the optimal super parameter values of LSTM model, so as to improve the accuracy of time series diagnosis. The rolling bearing experimental data of Case Western Reserve University were used for fault diagnosis experiments. The results show that IHHO-LSTM model can realize the feature extraction and fault diagnosis of rolling bearing, and the accuracy of the model is nearly 97%.
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发布时间：2024-04-18 - 摘要：Aiming at the problem of trajectory tracking and end elastic vibration of plane single arm flexible beam, a method based on μ synthesis control method was used to suppress the vibration. Firstly, by hypothetical modal method described elastic deformation, and using Lagrange equation established the dynamic model. Secondly, considering the parameter uncertainty andmodeling perturbation of load mass and structural damping, by using linear fractional transformation and weighting function established mixed uncertainty model. By introducing ideal model to improve the standard control structure of μ synthesis, which improved system convergence and closed-loop system performance. Based on μ synthesis control method , the robust controller of the system was designed. The simulation results show that the upper and lower bounds of the structural singular value of the controller are less than 1, indicating that the system has good robust stability and robust performance. Through the comparative analysis with PD controller, it shows that in the presence of uncertainty and interference, the proposed control strategy can track the trajectory with higher accuracy and attenuate the end vibration more effectively, which verifies the effectiveness of the control strategy.关键词：Plane single arm flexible beam;Elastic vibration;Mixed uncertainty;μ synthesis;Structural singular
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发布时间：2024-04-18 - 摘要：In order to reduce the resistance in the cutting process, through the configuration analysis of the tooth rake face of beaver, a turning tool with variable curvature quasi-linear surface configuration was designed. In 0. 15-0.5 mm back cutting ,four kinds of rake face configurations were selected for simulation cutting comparative analysis. The simulation results show that the cutting force of the rake face tool with chord function quasi-linear configuration is reduced by 3.5%-11.96% compared with the other rake face tools. The simulation results are verified by the right angle cutting experiment. Subsequently, the parameter optimization of cosine quasi-line function was carried out through simulation experiment, and the variation law of cutting force with the change of period and amplitude was obtained. The optimization results show that the drag reduction effect is the most obvious when the ratio of the back cutter amount to the front cutter area chord function is about 40% in one cycle. The variable curvature rake face turning tool designed in this study not only effectively reduces the cutting force, but also provides a new idea for the configuration design of metal cutting tools, which has strong application value.关键词：Bionic tool;Variable curvature configuration;Cutting simulation;Cutting force;Drag reduction method
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发布时间：2024-04-18 - 摘要：Thin-walled energy absorber plays an important role in aerospace, transportation and other fields. Inspired by carambola fruit with excellent crashworthiness, the bio-inspired pentacle thin-walled structure was designed. The deformation and energy absorption mechanism of the struct were analyzed by finite element simulation, experiment and theory. The influence of cross-section shapes and geometric parameters on the energy absorption characteristies were discussed. Investigations were carried out on the optimization effect of hierarchy and stiffener on crashworthiness. The results show that the bio-inspired pentacle thin-walled structure has regular progressive folding deformation mechanism. The crashworthiness properties of pentacle thin-walledstructure, such as specific energy absorption and crushing force efficiency, are significantly better than that of thin-walled structures with common sections, showing good engineering application potential.关键词：Crashworthiness;Thin-walled structure;Energy absorption;Finite element simulation;Structural bionics
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发布时间：2024-04-18 - 摘要：In order to meet the structural design and prototyping requirements of micro multi-functional brackets, a study on the design and preparation of flexible elastie dot matrix brackets based on digital light processing (DLP) rapid forming process was carried out. Based on the geometric topology design of the cell structure, the equivalent mechanical model of the cell structure was established by using Timoshenko beam theory to obtain a mathematical model for predicting energy absorption, and the influence of cell geometry and load direction was analyzed in focus. The novel flexible photosensitive resin was used as the forming material , and the DLP forming process was selected to realize the high-precision and high-efficiency preparation of the corresponding dot matrix structure. Combining numerical simulation and physical experiments, the effects of rod diameter, cell edge length and number of dot matrix layers on the energy absorption characteristies of the dot matrix structure were investigated. The results show that the out-of-plane compression of the dot matrix structure has significantly better energy.关键词：Tissue engineering scaffold;Flexible elastic dot matrix structure;Equivalent mechanical model;DLP forming process;Compression energy absorption
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发布时间：2024-04-18 - 摘要：Aiming at an airborne drilling rig for digging and anchoring, its working conditions and functional requirements were analyzed. The force of the drilling rig under various working conditions was analyzed, and the strength of the key components was verified by finite element simulation. The theoretical analysis results show that the vertical load of the installationseat, the vertical load of the telescopic slide sleeve and the joint of the drilling rig and the vertical load of the telescopic slide sleeve increase at first and then decrease with the increase of the pitching angle, and the torque is the highest when the pitching angle is 0°. The finite element calculation results show that the maximum stress of the telescopic rail and telescopic sliding sleeve of the key components is far less than the yield strength of the material Q345B, which meets the application requirements. The maximum stress of the fixed bracket of the drilling rig is only 37.096 MPa, and the deformation is 2. 006 mm, indieating that the fixed bracket of the drilling rig can meet the strength requirements under the maximum load. The effectiveness of the structure of the exploration and discharge drilling rig designed is verified by the industrial tests in the plant and underground coal mine, and it has good value of application and popularization.关键词：Exploration and discharge drilling rig;Airborne drilling rig;Mechanical properties;Finite element analysis
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发布时间：2024-09-13 - 摘要：The properties of 316L stainless steel can be improved by using ultrasonie impact method to modify the specimen surface. The fatigue properties and fracture properties of 316 and 316L stainless steel were treated by tensile test, high-cyclefatigue test, SEM, XRD and EDS. The results show that both the tensile strength and the fatigue strength of 316L stainless steel with Iower carbon content are lower. The tensile strength of this austenitic stainless steel can be increased by 19.7%, but the toughness decreased. The fatigue limits of 316, 316L and 316L after impact treatment are 209 MPa, 204 MPa and 254 MPa, respectively. Both of them are about 35% of their tensile strength. The fitting formula of S-N curve is S = -64 + 0.45σb. The fatigue data of 316 with higher carbon content has better normalization, and no side-crack is observed. The fracture surface shows that the cracks initiate from the heterogeneous phase or the non-metallie inclusion. Cracks usually propagate along the grain boundary. The velocity fluctuation of crack propagation zone is also attributed to the heterogeneous phases. After the ultrasonie impact, the rack growth of 316L is obviously reduced, the section fluctuation is larger, and the transient fracture speed is faster.关键词：Ultrasonic impact;Carbon content;316L stainless steel;Fatigue properties
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发布时间：2024-04-18 - 摘要：As the power density of an engine increases, so does the temperature and stress that the cylinder head is subjected to during operation. Therefore, creep damage prediction needs to consider accurate creep constitutive models and parameters. Aiming at the wide range of temperature and stress working conditions of the compacted graphite cast iron (CGI) cylinder head, CGI creep test was carried out at 450-550 °C and 100-300 MPa. The comparative study of creep constitutive models to characterize the minimum creep rate of CGI under a wide range of temperature and stress was carried out. The research shows that compared with a smaller range of temperature and stress, CGI is more prone to creep damage under wide conditions. and temperature can promote the creep deformation of CGI more than stress. Based on the Norton-Bailey power law model, the Garofalo hyperbolic sine model, and the deformation mechanism-based true stress (DMTS) model respectively, combined with the multi-objective optimization method, the CGI creep constitutive model was constructed. Among them, 73% of the predicted values of the CGI creep model based on the DMTS model are within twice the error range, and the coincidence effect is the best among the three models.关键词：Compacted graphite cast iron;Wide temperature and stress range;Creep test;Creep-constitutive model;Minimum creep rate;Multi-objective optimization
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发布时间：2024-04-18 - 摘要：According to a certain type of aireraft fuselage structure's crashworthiness(occupant survivability envelope) design requirements, a standard 14g vertical impact test of the 'floor-seat-occupant' system which meet the requirements of AC25.562-1B regulations was carried out first. Then, finite element model calibration of the test was carried out based on Ls-Dyna software. After calibration, in order to simulate the vertical drop conditions, several impact pulses with different peaks and widths were designed, calculated and tested on 80° fixture condition, and obtained the seat vertical impact pulse envelope meeting the occupant lumbar injury index, which provide reference for the design of aireraft fuselage structure. In addition, the concept of seat 'force transfer coefficient K' and the hysteretic effect of seat cushion on passenger lumbar load under different impact pulses were proposed based on the injury index of passenger lumbar load.关键词：Crashworthiness;Impact test;Lumbar load;Seat;Impact pulse;Finite element
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发布时间：2024-04-18 - 摘要：The quasi-static compressive stress of reinforced honeycomb is studied. Firstly, the structure of the reinforeed honeycomb is analyzed, the Y-shaped cells are extracted, and the plastic hinge is analyzed based on this. Then, referring to the simplified superfolding theory, based on Tresca and Mises yield criterion, the theoretical formula of axial plateau stress is deduced. Thirdly, the aluminum alloy 5052H18 with a wall thickness of 0. 15 mm and a side length of 2. 5 mm is selected, and the honeycomb simulation model is established by Ls-Dyna to obtain the average stress. Comparing the theoretical value with the simulated value, the results show that: under the two yield criteria, the correlation between the theoretical value and the simulation result is 0.96, and the deviation is from -12.16% to 3.60%. Finally, the sample preparation and quasi-static test of ordinary and "4+1"honeycombs shows that the deviation between the theoretical strength and the actual strength of the two specifications is between -2.51% and 1.56%. It shows that the theoretical calculation formula given in this paper is correct, which can provide an effective design basis for the selection of reinforeed honeycombs, and provide a certain guiding value for engineering applications.关键词：Reinforced honeycomb;Quasi-static compression;Numerical simulation;Test comparison
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发布时间：2024-04-18 - 摘要：When estimating very small failure probability, the methods based on active learning Kriging (ALK) model usually need too many candidate points and time-consuming calculation. To address this problem, this paper proposes a two-stage surrogate model method, ALK-SS2, which combines the ALK model and subset simulation(SS). Firstly, based on the constructed surrogate model in the first stage, the method uses a small number of SS last layer samples as candidate samples to complete the rough approximation of the limit state surface, and then in the second stage, it selects the SS last layer samples witha larger sample size to refine the surrogate model in the first stage, so as to obtain higher accuracy. In addition, considering the conventional stopping criteria are too conservative. based on the failure probabilitv evaluated by ALK-SS2, a new stopping criterion based on failure probability error is proposed, which further improves the efficiency of the method. From the investigation of four examples and the comparison with relative methods, it is proved that the proposed method has high calculation accuracy and efficiency, and is suitable for dealing with small failure probability problems and time-consuming implicit function problems.关键词：Reliability analysis;Active learning;Kriging model;Subset simulation
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发布时间：2024-04-18 - 摘要：Gradient honeycombs have received extensive attention due to their excellent mechanical properties and crashworthiness. Taking the crashworthiness index of the honeycomb as the optimization goal, in the design space of the gradient honeycomb, the multi-objective optimization algorithm is directly used to determine the specific parameters of each layer of the gradient honeyeomb. Usually, multi-objective optimization design is used to obtain Pareto sets of optimal graded honeycomb. According to different application environment of graded honeycomb, appropriate graded honeycombs can be selected. The regular hexagonal honeycomb is taken as the research object in this paper, and the homogeneous honeycomb is divided into 4 layers for next optimal design. That the graded honeycomb recommended by the NSGA-I algorithm is compared with the homogeneous honeycomb. The results show that the graded honeycomb can greatly improve the initial peak force (P,PCF) while slightly inereasing the total energy absorption (E,EA) and specific energy absorption (S,SEA), and the maximum improvement is 78. 51 %, which proves the advantage of using this method for gradient design.关键词：Honeycomb;Gradient design;Multi-objective optimization;Crashworthiness;Optimal solution set
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发布时间：2024-04-18 - 摘要：The hazard rate function with a bathtub-shaped curve is crucial in reliability engineering due to its ability to capture certain observed failure rate characteristies in real-world scenarios. This study introduces a novel MPGW (Modified Power Generalized Weibull) distribution capable of modeling hazard rate function exhibiting a bathtub shape. To evaluate the effectiveness of this model, the study conducted empirical research using a dataset of pressure steam sterilizer failures and compared its performance to 5 classical distribution models, the results indicated that this model exhibits significant advantages in terms of flexibility.关键词：MPGW distribution;Bathtub curve;Pressure steam sterilizer
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发布时间：2024-04-18 - 摘要：Aiming at the sliding door of an automobile as the research object, a comprehensive finite element model of the sliding door based on the modal frequency and stiffness is established. The components with relatively small sensitivity are selected as the design variables through sensitivity analysis. The sample data of the thickness of key components are designed by using the Hamersley sampling test design method. The calculation results are fitted with the sliding door mass, first-order bending modal frequency. Approximate model of first-order torsional modal frequency, torsional stiffness and vertical stiffness response. Based on the approximate model, taking the minimum mass as the main objective and the maximum first-order bending frequency as the reference objective, and taking the first-order torsional mode of sliding door torsional stiffness and vertical stiffness as constraints, the multi-objective optimization algorithm based on global response surface method in Hyperstudy is applied to optimize the design to achieve the purpose of lightweight.关键词：Sliding door;Sensitivity analysis;Test design;Response surface;Multi objective optimization
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发布时间：2024-04-18 - 摘要：Planetary transmission mechanism is the core part of tracked vehicle transmission system, its reliability directly affects the tracked vehicle normal operation. Taking tracked vehicle planetary transmission mechanism as the research object, the fault tree was established based on the measured test results, and the fault tree was transformed into a Bayesian network (BN) model, and the reliability analysis was carried out considering the planetary transmission mechanism three states of normal general failure and serious failure . The results show that planetary transmission mechanism failure probability is 89.34×10-8 h-1.and its reliability is 0.999 64 for 400 hours, which meets the design requirements. Using Bayesian network bidirectional calculation function, planetary transmission mechanism fault is more likely to be caused by the main shaft fracture or friction plate ablation, warping, fracture or gear fatigue broken teeth. It provides a theoretical basis for subsequent equipment maintenance and improvement design.关键词：Fault tree analysis;Bayesian Network;Polymorphic reliability;Planetary transmission mechanism
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发布时间：2024-04-18 - 摘要：Bolting is a common connection method in engineering and construction, and the tightening torque is often used to control the preload of bolts on industrial sites to ensure the reliability. The torque coefficient is defined as the proportional factor between the tightening torque and the preload force of the bolt, which is essential to estimate the appropriate tightening torque range. At present, the research on torque coefficient is mainly focused on circular face bolts, and there is less research on other face bolts. Based on the force analysis of the bolt tightening process, a mechanical model of bolt preload is proposed, and an accurate calculation formula of the torque coefficient of arbitrary end face bolt is derived by using description of the internaland external contours of the bolt end face in polar coordinates. A simple torque coefficient measurement system is built to test and verify the torque coefficients of circular end face, hexagonal end face and T-shaped end face bolts. The testing results are consistent with the theoretical caleulation, which proves the accuracy of the theoretical caleulation formula of torque coefficient.
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发布时间：2024-04-18 - 摘要：The rotational speed of gear system directly affects the dynamic characteristies of gear system, but this important factor was often ignored by many scholars in the caleulation of mesh stiffness. In order to study the influence of rotational speed on mesh stiffness, an algorithm of calculating the dynamic mesh stiffness which related to rotational speed was proposed based on finite element framework by using the average acceleration method. Meanwhile, the dynamic mesh stiffness under different rotational speeds was simulated and analyzed. Finally, the relevant dynamic characteristics of gear system which affected by dynamic mesh stiffness were further explored. The research results show that the dynamic mesh stiffness varies with rotational speed of gear system. With the increase of rotational speed, the fluctuation range of the dynamic mesh stiffness increases relative to the static mesh stiffness. The resonance speed range of the gear system calculated by dynamic mesh stiffness is either ahead or behind the static mesh stiffness, and the super harmonic response of dynamie mesh stiffness model is more obvious at high rotational speed. The research on dynamic mesh stiffness related to rotational speed can provide reference for improving transmission performance and reducing vibration and noise of spur gear.关键词：Gear system;Dynamic response;Dynamic mesh stiffness;Nonlinear vibration;Rotational speed
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发布时间：2024-04-18 - 摘要：Functionally graded shape memory alloys (FG-SMA) have the properties of both functionally graded materials and shape memory alloys (SMA), so they have been widely used in aerospace, biomedical, and micro electro mechanical systems(MEMS). The influence of surface effects on the mechanical properties of microstructure is very significant when the scale reaches the nanometer scale. In order to study the effect of surface effects on the mechanical properties of FG-SMA, based on the bending theory and Gurtin-Murdoch surface elasticity theory, the phase transition mechanical model considering the effects of tensile and compressive asymmetry and temperature on FG-SMA nanobeams was developed considering the surface effects. The influence of functionally graded index, load, temperature, and tensile-compression asymmetry coefficient on the mechanical properties of FG-SMA nanobeams was analyzed. It is shown that bending moment and functionally graded index have significant effects on the cross-sectional response, while temperature and tensile asymmetry coefficient have fewer effects on them. Ignoring the influence of surface effect will underestimate the flexural resistance of FG-SMA nanobeams. When the bending moment reaches a certain range, the neutral axis deflection of FG-SMA nanobeams is not much affected by surface effects. The results of the study provide a basis for the design and application of FG-SMA nanobeams in the field of MEMS.关键词：Functionally graded shape memory alloys;Micro electro mechanical system;Surface effect;Gurtin-Murdoch surface elasticity theory;Phase transition
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发布时间：2024-04-18 - 摘要：Based on the top beam support structure of advance support equipment, a design method of constant pressure support device is studied. The constant pressure support device is composed of positive stiffness linear spring, negative stiffness nonlinear plane curved beam and pressure bearing air bag. The characteristics of Nonlinear Plane Curved Beam with negative stiffness are briefly described by using B-spline curve. Based on genetic algorithm and nonlinear finite element method , the shape of the nonlinear plane curved beam with negative stiffness is designed and optimized. According to the working principle of constant pressure support, the stiffness and strength properties of the linear coil spring are analyzed and designed. The components of the constant pressure support device are designed to realize the constant output pressure and self-protection function of the support device. The constant pressure support design method proposed in this paper provides strong technical support for the development of advanced support in the fully mechanized mining road.关键词：Constant pressure support device;Nonlinear plane curved beam;Morphological optimization
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发布时间：2024-04-18 - 摘要：In order to more accurately reflect the real contact stress on the tooth surface of beveloid gear, this paper constructs the tooth surface contact coefficient of beveloid gear, and verifies its rationality. Based on fractal contact theory and Hertz contact theory, a contact model of beveloid gear is established, which comprehensively considers the parameters such as gear tooth surface roughness, elastic deformation of contact point and material characteristics. The effectiveness of this method is contact strength of beveloid gear, which is compared with the finite element calculation results by calculating. The relation between load and area during gear meshing is obtained through fractal theory, and four basic parameters are simulated to analyze the effect of fractal contact model. The results show that the accuracy of fractal contact model is verified by numerical simulation and analysis of the relation between actual contact area and load. This paper is based on the finite element theory, Hertz contact theory and fractal theory, the tooth surface contact strength of beveloid gear is compared and analyzed, the correctness of calculating the contact stress of beveloid gear by fractal contact model is verified. The establishment of this model provides a certain theoretical basis for the design and strength check of beveloid gear.关键词：Beveloid gear;Fractal theory;Contact stress;Hertz contact theory
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发布时间：2024-04-18 - 摘要：The stability analysis of spherical hybrid sliding bearings includes exploring its dynamic characteristics and critical speed, its stiffness and damping coefficient have an important impact on the stability of the bearing-rotor system, and the study of critical speed can effectively avoid whirl instability in the bearing-rotor system. The boundary slip conditions are considered to analyze the stability of spherical hybrid sliding bearings. Taking the flow of the small hole restrictor into the oilcavity equal to the flow out of the oil sealing edge as the boundary condition, the Reynolds equation in the boundary slip state is solved to obtain the oil cavity pressure and the oil sealing edge pressure. For the transient Reynolds equation in the boundary slipstate, the equation uses the small perturbation method to derive the partial differential equation of the perturbation pressure, and combines the finite difference method and the relaxation iterative method to solve the equation to obtain the stiffness and damping coefficient of the ball bearing under the state of boundary slip, and then establish the shafting trajectory equation to solve the instability speed. The influence of slip coefficient, oil supply pressure, rotor speed on the dynamic characteristics of the bearingand the variation law of the instability speed on the slip coefficient are discussed. The results show that the increase of the slipcoefficient will lead to the decrease of the four stiffness coefficients and the cross damping coefficients, and the increase of thedirect dampings. The increase of the oil supply pressure will lead to the increase of the eight dynamic characteristic coefficients, and the increase of the rotational speed will lead to the increase of the stiffness and the decrease of the dampings, and the occurrence of slip effect does not affect the above rules. The instability speed decreases with the increase of slip coefficient, so the system stability decreases.关键词：Spherical hybrid sliding bearings;Pinhole throttling;Reynolds equation;Boundary slip;Dynamic characteristic;Critical speed
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发布时间：2024-04-18 - 摘要：Silicon is the most potential anode material for new high capacity lithium ion batteries with high energy density. However, the huge volume deformation of silicon materials during charging and discharging leads to severe damage and rapiddegradation of electrodes, making the cycle life of silicon-based batteries generally low and difficult to meet the design requirements of both high capacity and long life, which is the core problem in the development of high-capacity lithium-ion batteries. As one of the main components of the active layer of lithium ion battery composite electrode, conductive agent is traditionally considered to improve the electrical conductivity of the electrode. By studying the component content of the conductive agent (taking carbon nanotubes as an example), the experiment revealed that the conductive agent has a regulating effect on the initial crack density of the silicon composite electrode, and the optimal value of the carbon nanotube content was obtained, and the negative mechanism by which the addition of carbon nanotubes introduces defects was discovered. This mechanism also plays an important role in electrochemical cycling. The above experimental results are of great significance for the design and preparation of high capacity and long-life silicon composite electrode.关键词：Lithium-ion batteries;Carbon nanotubes;Initial crack;Defects;Hydrophobicity
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发布时间：2024-04-18 - 摘要：Failure mode of bonded structure under different adhesive types and different adhesive thickness was discussed by designing the edge ring crack torsion test which can truly reflect mode III fracture toughness. And the fracture characteristies of bonded structure are revealed by combing the peak torque and strain energy release rate. Through the comparative analysis of experiment and simulation, parameter expression of cohesive zone model which considered the thickness effect is deduced by inversion method. The results show that the peak torque and strain energy release rate of Araldite 2015 increased with the increase of adhesive thickness. While the peak torque and strain energy release rate of E-120HP and WD3705 showed a concave trend with the increase of adhesive thickness. This study provides a basis for reasonably evaluating the effect of adhesive type and thickness on the failure mechanism of bonded structures under type III fracture.关键词：Adhesive;Finite element simulation;Cohesive zone model;Mode III fracture;Fracture toughness
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发布时间：2024-04-18 - 摘要：The stress intensity factor (SIF) have been studied by many methods based on the displacement element model. However, under sparse meshes, the displacement element models will suffer from excessive stiffness, and are difficult to introduce the stress boundary conditions directly which lacking in objectivity. The generalized mixed enriched element method is proposed based on the principle of enriched element and generalized H-R variational principle. This method takes the crack tipstress singularity into account, considers the introducing of stress boundary conditions, and overcomes the oscillation of the classical mixed enriched element method. Numerical examples show that the stress intensity factor obtined by this method is stable and reliable with a high degree of accuracy.关键词：Singularity;Stress intensity factor;Generalized mixed enriched element;Stress boundary condition
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发布时间：2024-04-18 - 摘要：Aiming at the fatigue fracture problem of aireraft hydraulic pipeline connector, the fatigue life of hydraulic conduit with axial assembly deviation was predicted based on random vibration theory. Starting with the establishment of the finite element model of the pipeline connector of the real aircraft hydraulic system, the influence law of the assembly stress caused by the axial assembly deviation on the structure was analyzed, and the damping ratio of the pipeline connector under different axial deviation is obtained through the test. The random vibration analysis was carried out by using the finite element analysis software, and the stress response power spectral density function of the dangerous part was obtained. Combined with Miner linear damage theory, the random vibration fatigue life of the pipeline connector with assembly stress was predicted. The resonance fatigue test of pipeline was designed and carried out. It is found that the crack initiation position and the decreasing trend of fatigue life of pipeline are consistent with the simulation results. The simulation and test results show that when the axial deviation reaches 0.8 mm, it seriously affects the flight safety. The research results provide theoretical reference and technical support for the design and assembly theory of aviation hydraulic pipeline.关键词：Pipe connector;Assembly stress;Random vibration;Power spectral density;Fatigue life
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发布时间：2024-04-18 - 摘要：The critieal distance theory is suitable for caleulating the creep-fatigue life of complex structures, but the calculation efficiency of this method is very low in engineering. To overcome this shortcoming, Python language was used for the secondary development of Abaqus software. The developed software can calculate the creep-fatigue life of the structure by using the critical distance method. To improve analytical efficiency, various functions were developed in the software, including model information extraction, material parameter import and calculation result output, ete. The applicability of the software was verified by analyzing a high-pressure turbine blade. The results show that the software can efficiently calculate the creep-fatigue life of complex structures by simplifying the steps of the critical distance method, and it has certain engineering value.关键词：Complex structure;Life calculation;Python;ABAQUS second-development;Critical distance theory
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发布时间：2024-04-18 - 摘要：Aiming at the problems that the failure reason of the solid partition structure inside the double-cavity fuel tank is not easy to obtain and the load is not to quantify of a tractor, a fatigue failure solution for fuel tank based on the measured load is proposed. The fracture of the sample was observed and analyzed by SEM, and the failure mode was determined to be fatigue failure. Based on the analysis of the mechanical properties of fuel , the main reason for the failure of the double-cavity tank wasthat the solid partition receives too much impact force due to the insufficient sloshing damping provided by single damping baffle. The porous damping baffle was added inside the fuel tank to reduce the impact force of fuel sloshing on the solid baffle during driving and the tank structure was optimized. Sensors were installed at key positions before and after fuel tank optimization. The strain load spectrum of solid partition plate before and after optimization of double-cavity fuel tank was compared in the test field. and the difference of strain load before and after optimization was quantified by means of amplitude, rain flow and statistical analysis of the load data. The measured load of the fuel tank before and after optimization was quantitatively analyzed, and the maximum load value decreases by more than 60% after optimization, which indicates that the damping baffle can effectively reduce the impact force of fuel on the solid partition. After optimization, there was no tank failure problem in the road test field, which indicates that the optimized strain load of the solid partition was lower than the fatigue limit of the fuel tank, and the fatigue life of the solid partition was increased. To verify that the optimized fuel tank structure meets the safety requirements, and to provide theoretical guidance and data for the subsequent optimization and the next generation of new product development.关键词：Fuel tank;Scanning electron microscope;Failure;Anti shaking damping;Structural optimization;Measured load
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发布时间：2024-04-18 - 摘要：The effect of surface morphology parameters on the contact damping of miero textured surface was studied. The damping source of the joint surface is analyzed, and the mathematical model of the damping of a single micro convex body on the joint surface is established. Further, based on the distribution density function of planar micro bumps, the number of surface contact micro bumps is calculated, and the effects of texture density, material characteristic parameters, frequency and amplitude of applied dynamic load on contact damping are studied. The results of research and example analysis show that the higher the texture density is, the smaller the contact damping between the surfaces is. With the increase of material characteristic parameters, the normal contact damping increases. With the increase of vibration frequency, the contact damping decreases gradually under the same load. The larger the dynamic deformation amplitude is, the greater the contact damping is.关键词：Normal contact damping;Surface texture;Texture density
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发布时间：2024-04-18 - 摘要：To research mechanical behaviors of advanced high strength dual-phase steel DP780 in the warm forming ,fundamental mechanical properties and true stress-strain curves of the DP780 were obtained and analyzed based on the warm uniaxial tensile test with temperatures of 300 °C , 400 °C, 500 °C , 600 °C, and strain rates of 10-4~10-3 s-1. The parameters ofGrosman constitutive model were solved and corrected in the warm forming to describe the warm forming stress-strain curves of DP780 steel plate. Taking the uniaxial tension model as an example, the Abaqus-Vumat subroutine was written based on Fortran language to verify the numerical simulation. The results show that the predicted values of Grosman model are in good agreement with the experimental values, which proves the validity of the proposed model.关键词：Advanced high strength duplex steel;Constitutive model;Warm forming;Uniaxial tensile test;Numerical simulation
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发布时间：2024-04-18 -
OPTIMIZATION OF REDUCER OF VERTICAL BUCKET ELEVATOR BASED ON IMPROVED NORTHERN GOSHA WK OPTIMIZATION
摘要：Vertical bucket elevator is a kind of mechanical conveying equipment with fixed device, which has the advantages of strong conveying capacity, high lifting height, stable and reliable operation, long service life and so on. Reducer is the key component of vertical bucket elevator. In order to obtain the optimal solution of reducer efficiently, an improved northern goshawk optimization algorithm based on sprint decisive strategy is proposed. Two classical nonlinear constrained engineering examples of pressure vessel and cantilever beam are used to verify the performance of the improved northern goshawk algorithm. The results show that the improved northern goshawk algorithm has good convergence speed. On this basis, the reducer of vertical bucket elevator is optimized. The results show that the center distance of the reducer is reduced from the initial 720 mm to 680. 16 mm, which is 5.33% lower than the initial value. The improved northern goshawk optimization algorithm can be used as an efficient optimization algorithm to solve practical engineering problems.关键词：Northern goshawk algorithm;Sprint winning strategy;Vertical bucket elevator;Reducer;Optimization algorithm- 16
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发布时间：2024-04-18 - 摘要：The correlation between the parameters of the Gamma degradation process was described by the Jeffreys uninformative prior distribution. And the Bayesian model was used to obtain the full conditional distribution of each parameter. The MCMC method was used to get parameter posterior expectation estimates. Finally, reliability was calculated according to the engineering examples and 100 simulations, the obtained reliability assessment was more conservative than the independent case in engineering practice. Thus, the product repair suggestion could be given earlier. And the higher the reliability requirement was .the oreater the deviation between the estimation results of the correlated case and the independent case was, and the life estimation error rate under the reliability of 0. 999 9 was up to 9.26%.关键词：Gamma process;Dependent parameters;Jeffreys uninformative prior distribution;Markov chain Monte Carlo
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发布时间：2024-04-18
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