最新刊期
期 5 ， 2022
- 摘要：The working environment of rolling bearing is complex, the nonlinear vibration signal and the interference of environmental noise lead to the difficulty of fault diagnosis. Therefore, based on the experimental data of bearing damage and the fractal theory, the Intrinsic Time scale Decomposition（ITD） was used to extract the nonlinear features of vibration signals, and the effective fault feature components were selected. The intelligent fault diagnosis of bearings was realized through Convolutional Neural Network（CNN）. The results show that compared with the existing methods, ITD-CNN has higher accuracy under different SNR. At-4 dB signal to noise ratio, the accuracy is still 2.57%～13.35% higher than the existing methods, which indicates that the proposed method has good recognition ability and generalization performance.关键词：Bearing;Intrinsic time scale decomposition;Convolutional neural network;Box dimension;Fault diagnosis
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发布时间：2022-11-10 - 摘要：To solve the problem that the amplitude of the added white noise and the number of ensemble trials to the ensemble empirical mode decomposition algorithm depend too much on subjective experience or multiple attempts, which is more subjective and blind, a fault diagnosis method based on adaptive EEMD and Fast Kurtogram is proposed. Firstly, the collected vibration signals are preprocessed by EMD to obtain the key input parameters of EEMD adaptively, and then combined with the “double threshold criterion” of the kurtosis and cross-correlation coefficient quickly choose components for signal reconstruction to highlight the fault characteristic, and through the Fast Kurtogram select optimal band-pass filter parameters, finally, the signal after filtering do envelope spectrum analysis, realize the extraction of fault feature frequency and fault diagnosis.The validity of the proposed method is verified by simulation signal analysis and fault diagnosis engineering application of reducer gearbox and comparing with the EMD method and the traditional EEMD method.The results show that the proposed method can successfully extract the reducer gearbox’s early weak fault characteristics from the signal with strong background noise, and the timeliness and accuracy of fault diagnosis are improved.关键词：Gearbox;Ensemble empirical mode decomposition;Fast kurtogram;Kurtosis;Cross-correlation coefficient;Fault diagnosis
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发布时间：2022-11-10 - 摘要：Established an impact-unbalanced suspended rotor system mechanics models, and the dimensionless motion equation of system is deduced, using the fourth order Runge-Kutta method for the numerical calculation of this model, the integrated use of bifurcation diagram, orbit diagram, Poincare section diagram, the axis displacement time history diagram, maximum moment diagram and duty ratio diagram study the dynamic behavior of the system, identify the impact of the rotor, the maximum torque and impact by the proportion of time, and analyzed the speed ratio and the change of the stiffness coefficient of the influence of the nonlinear dynamic characteristics of the system.The analysis results show that the system presents chaotic motion in a certain parameter domain at the medium velocity stage, while the system tends to stable periodic motion in other parameter domains.With the increase of the stiffness coefficient, the chaotic motion region and the maximum moment of the system increase, and the stability of the system decreases.关键词：Rotor system;Impact;Nonlinearity;Bifurcation
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发布时间：2022-11-10 - 摘要：According to the characteristics and technical requirements of ammunition transportation, proposes a double-layer vibration isolation system with large load, establishes its dynamic model, solves the transfer function by using Laplace transform, analyzes the influence characteristics of various parameters on the transfer function through MATLAB, establishes the finite element simulation model and compares with the theoretical model, and verifies the accuracy of the model. On this basis, the corresponding optimization rules are set, and the NSGA-II optimization algorithm is used to optimize the system parameters, and the optimal parameters of the double-layer vibration isolator are obtained. Finally, the actual data are used to verify the vibration isolation effect. The results show that the vibration isolation effect of the double-layer vibration isolation system with large load is greatly improved compared with the single-layer linear vibration isolation system.关键词：Double layer vibration isolator;Multi-objective optimization;Ammunition transportation;NSGA-Ⅱ optimization algorithm
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发布时间：2022-11-10 - 摘要：Due to the uneven distribution of flow velocity when the water flows in the middle section of the bidirectional flow guide device, affect the power generation efficiency of the horizontal axis turbine. By studying the blade radius and installation position of the turbine inside the guide device, improve the power generation efficiency of the turbine inside the two-way guide device in the two-way water flow. First, using Fluent to obtain the flow velocity distribution curve of the vertical section of the center of the diversion device. By means of numerical analysis, established the mathematical model of velocity distribution, and calculated the optimal blade radius. Then, by studying the variation law of flow velocity distribution in the vertical direction, obtained the optimal blade installation position. Finally, through the drag experiment, obtained the periodic power generation under the bidirectional water flow. The research results show that when the blade radius is within the linear range of the flow velocity distribution, the flow velocity of the rotating surface of the turbine blade is larger, and the flow velocity of the rotating surface of the turbine blade increases significantly as the blade installation position decreases. When the water flow velocity is 1 m/s, after adjusting the blade radius and installation position of the turbine, the power generation of the turbine is increased by 72% compared with the previous one, and the power generation by the bare blade is increased by 150%.关键词：Tidal power;Velocity distribution;Leaf blade radius;Installation position;Power generation
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发布时间：2022-11-10 - 摘要：According to the characteristics of the magnetorheological fluid, in this thesis, there are designs of a set of adaptive, flexible auxiliary supporting device units, which can be used to develop the processing accuracy of complex curved parts with weak rigidity. The magnetic field of the device is simulated by comsol using finite elements to determine its magnetic strength. It establishes the milling and positioning models of the workpieces with weak stiffness based on the magnetorheological effect, analyzing the positioning constraint models under the auxiliary support, calculating the deformation of the work pieces under static state, studying the influence of the device on the quality of the workpieces. It set up a milling test platform based on magnetorheological auxiliary support, milling parts with weak stiffness under the conditions of different current parameters, collecting acceleration signals for analysis by labview platform data acquisition system, measuring the surface roughness of the milling process. The results agree that, under the action of the magnetorheological auxiliary support, in comparison with the unsupported state, the vibration amplitude is reduced 46.9% to 75.7%, and the surface roughness of the workpieces with weak rigidity is about 69.89% to 80.61% lower.关键词：Magnetorheological effect;Magnetic field simulation;Fixture system;Milling test;Machining accuracy
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发布时间：2022-11-10 - 摘要：Bending fatigue failure is one of the main failure modes for gears in transmission system, shot peening is an important gear strengthen technology. In order to study the influence of shot peening on gear bending fatigue characteristics, 20 MnCr5 carburized involute cylindrical spur gear was adopted as study object. The effect of shot peening on gear surface integrity were analyzed before and after shot peening, coinciding with our products. Bending fatigue test was carried out with the single tooth loading method, afterwards, based on the observation of the failure fracture surfaces by scanning electron microscope（SEM）, the differences of failure characteristics in the crack source areas before and after shot peening were analyzed. It is found that shot peening can greatly improve gear surface integrity, although it has a negative effect on the gear surface corrugation. Shot peening can effectively increase gear bending strength and restrain the crack initiation from the gear surface.关键词：20MnCr5 carburized gear;Shot peening;Gear surface integrity;Bending fatigue characteristics;Failure fracture surfaces observation
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发布时间：2022-11-10 - 摘要：To study the effect of static pressure on the surface integrity of beryllium copper alloy during the ultrasonic rolling process, scanning electron microscope, stylus roughness tester, rockwell hardness tester, X-ray diffraction analyzer and metallographic microscope were used to measure and analyze the surface morphology, roughness, surface hardness, residual stress and microstructure of the before and after ultrasonic rolling specimens. The results indicate that the static pressure and the surface roughness show a nonlinear relationship in the range of test parameters. With the increase of static pressure, the surface roughness decreases first and then increases. Moreover, we can obtain better surface quality when the static pressure is 0.2 MPa～0.4 MPa. Work hardening and grain refinement of the material surface caused by the plastic strain generated during the ultrasonic rolling process are the main reasons for the increase in hardness. The surface hardness of the treated specimen can reach 43.3 HRC, which is 18.6% higher than that of the untreated specimen.The ultrasonic rolling treatment can transform the residual tensile stress on the surface of the material into residual compressive stress, which is of great significance for improving the surface mechanical properties of the material.关键词：Static pressure;Ultrasonic rolling;Beryllium copper alloy;Surface integrity
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发布时间：2022-11-10 - 摘要：The self-made thread root rolling strengthening device based on common lathe CA6140 was used to perform rolling strengthening process on 45 steel thread samples. The surface integrity parameters such as surface roughness, surface microhardness, residual stress and surface microstructure of thread root after rolling were measured by using three-dimensional topography measurement instrument, microhardness tester, X-ray residual stress detector and ultra-depth of field microscope. The effect of rolling strengthening parameters on the surface integrity of thread root was investigated by single factor test. After the 45 steel thread sample underwent the rolling strengthening process, the surface roughness Sa of the thread root is reduced from 1.71 μm to 0.874 μm; the thread root forms an obvious grain refinement layer with a depth of 120 μm; the microhardness increases from 199.3 HV to 379.5 HV, and the hardening degree N=90.4%; the residual stress of the surface layer is distributed in a spoon shape, and the residual stress reaches a peak value of-542 MPa at 105 μm from the surface, and the depth of the residual compressive stress layer can reach 700 μm. The results show that the rolling strengthening process can significantly improve the surface integrity of the thread root, and the rolling depth has the most significant effect.关键词：Rolling strengthening;Thread root;Surface roughness;Microhardness;Residual stress
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发布时间：2022-11-10 - 摘要：In order to study the effect of low temperature environment on the fatigue crack growth performance of high-speed train brake disc materials, the tensile and fatigue crack growth rate tests of special cast steel materials of high-speed railway brake disc at-40℃,-20℃, 0℃ and room temperature（20℃）were carried out. The mechanical properties, fatigue crack growth rate and fracture morphology of high-speed railway brake disc materials at different temperatures were analyzed. The results show that the decrease of temperature has a significant effect on the mechanical properties and fatigue crack propagation of high-speed railway brake disc. Compared with room temperature, the elastic modulus, Poisson′s ratio, yield strength, tensile strength and other mechanical properties of high-speed railway brake disc materials increase with the decrease of temperature. In the stable stage of fatigue crack growth, the fatigue crack growth rate decreases with the decrease of temperature, but the inhibition effect of low temperature on the fatigue crack growth rate decreases with the increase of ΔK. The fracture analysis shows that with the decrease of temperature, the fatigue crack propagation is likely to change from ductile fracture to brittle fracture.关键词：Low temperature;High-speed railway brake disc;Fatigue crack growth performance;Fracture surface analysis
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发布时间：2022-11-10 - 摘要：Established the double cold expansion simulation model, and investigated the effects of surface micromorphology characteristics on the fatigue performance of double cold expanded holes. The double cold expansion process and fatigue life of the strengthened holes was simulated by using ABAQUS and MSC. Fatigue software. The hole wall element was selected, and the surface micro-profile of the hole wall was represented as the semi-ellips micro-notches. The S-N curve of the material is modified by effective stress concentration factor Kf, and investigated the effects of surface micro-profile on the fatigue performance of double cold expanded holes.The results show that there existed compressive residual stress layer on the hole wall after the double cold expansion process, and the fatigue life of the expanded sample was increased. With the increasing of the number of micro-notches in the hole wall, the stress concentration factor can be alleviated effectively, and stress concentration factor Kt is positively correlated with the depth-width ratio b/a and the distance-width ratio d/（2a）. The double cold expansion process can reduce the surface roughness of the hole wall by 21%～49%, which can effectively alleviate the notch stress concentration and improve the fatigue performance of the hole.关键词：Double cold expansion;Surface micro-mrofile;Simulation analysis;Stress concentration factor;Fatigue life
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发布时间：2022-11-10 - 摘要：Several equipment clamps of main transformer in a nuclear power company were broken. Taking samples from the broken equipment clamps and the same batch of spare equipment clamps, the fracture causes were analyzed through macroscopic inspection, penetrant testing, metallographic analysis, micro morphology testing, crimping quality testing, conductivity testing and XRD testing. The main reason for the fracture is that the equipment clamp bears all kinds of stress under the condition of insufficient strength and performance degradation, and finally cracks appear at the weakest part of the weld, forming fracture. In order to avoid the occurrence of similar accidents, it is suggested to strengthen the metal supervision and strictly control the quality of the access equipment.关键词：Equipment clamp;Insufficient strength;Performance degradation;Weakest point;Fracture;Metal supervision
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发布时间：2022-11-10 - 摘要：The mechanical properties of steel plate are an obvious sensitivity of strain rate. Accurate measurement of the dynamic properties of materials plays an important role in accurately predicting the collision resistance of the car body. Based on the universal testing machine and the horizontal hydraulic driving testing system, the true stress-true strain curves were obtained at the different strain rates. At the same time, the crush test of box-shaped parts was designed to verify the accuracy of dynamic testing data. The results indicated that the measured parameters by using the true stress-true strain data of different strain rates obtained by tensile test were applied to the finite element simulation analysis in order to study the deformation morphology of high strength steel under the crushing states in the application of automotive industry. The force-displacement curve was predicted by the finite element, which is roughly the same as the curve obtained from the crushing test. Therefore, it was verified that the accuracy of the real stress-strain curve at the different strain rates. And it assists to realize the low-cost measurement of dynamic tensile parameters of high strength steel plates. In addition, it can provide the possible design basis for the car impact protection.关键词：True stress-true strain;Strain rate;Crushing;Simulation
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发布时间：2022-11-10 - 摘要：Absrtact Maxon Cinema 4 D R21 was used to build 3 D model, and the composite structure of truss ball filled interwoven network tube was made by 3 D printing. The uniaxial compression tests of 3 D printed truss ball, aluminum alloy thin-walled tube and composite structure filled with truss ball and interwoven network tube were carried out, and studied the difference between the composite structure of truss-sphere filled interlaced network tube and the other two structures in the energy absorption characteristics. The results show that the deformation degree and energy absorption capacity of the composite structure are directly affected by the impact. The composite structure can bear the highest load and the ball truss can bear the weakest load. The experimental results show that the energy absorption characteristics of the thin-walled tube are between the aluminum alloy thin-walled tube and the truss ball.关键词：Truss ball;Aluminum alloy thin-walled tube;Truss ball filled interwoven network tube composite structure;Uniaxial compression tests;Energy absorption characteristics;Impact deformation
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发布时间：2022-11-10 - 摘要：In order to study the failure mechanism of 6061-T651 aluminum alloy sheet under oblique impact, the impact experiments of a hemispherical projectile slanting into a single aluminum alloy sheet at different impact angles（0°, 15°, 30°, 45°） were carried out with a first-stage light gas gun, and the ballistic limit velocity and damage characteristics of the target plate were obtained. The results show that when the size and shape of projectile and target are the same, the ballistic limit of target decreases first and then increases with the increase of impact angle. When the impact angle is 15°, the ballistic limit of aluminum alloy target is the lowest, and the failure mode of target gradually transits from petal cracking to tensile tearing failure. In addition, at the same impact Angle, the damage of the target plate is also affected by the velocity of the projectile body.关键词：Oblique impact;The impact angle;The ballistic limit;Failure mode;6061-T651 aluminum alloy plate
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发布时间：2022-11-10 - 摘要：Taking a hydrogen-fueled truck frame as the research object, based on the topology optimization theory of variable density method, the goal of maximizing the static multi-working stiffness and improving the dynamic low-order natural frequency of the frame is realized. The attachments of the frame were retained, and the topological optimization space was established according to the original frame outline size. A multi-objective topology optimization was carried out by using the isotropic material penalty function to obtain the best frame structure layout, and then the new frame structure was designed. The results show that the middle bearing capacity of the new frame is better than that of the original frame which has been verified by modal testing, and the maximum stress decreases by 35.6%. The first-order natural frequency increases by 1.9 Hz, which can avoid the maximum excitation energy region of the road. Meanwhile, the frame weight is reduced by 7.8%, which realizes the specialized and lightweight design of a hydrogen-fueled truck frame.关键词：Hydrogen-fueled truck;Frame;Variable density method;Multi-objective topology optimization
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发布时间：2022-11-10 - 摘要：In order to improve the crashworthiness of the collision post structure, the optimal cross-section configuration of the collision post was obtained based on the topology optimization method, and the impacting finite element model of the collision post was established in the explicit dynamics software Ls-Dyna. Based on the optimal Latin hypercube experimental design method, a polynomial response surface surrogate model of the specific energy absorption and the peak crush force with respect to the wall thickness of the novel multi-cell collision post was established, the multi-objective optimization problem was conducted using the Non-dominated Sorting Genetic Algorithm-Ⅱ and the Pareto front was obtained. The optimization results show that the total energy and specific energy absorption of the novel multi-cell collision post are improved significantly while meeting the structural lightweight requirements compared with the conventional single-cell structure.关键词：Railway vehicles;Collision post;Crashworthiness;Topology optimization;Multi-objective optimization
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发布时间：2022-11-10 - 摘要：The lightweight of rack EMU（Electric Multiple Units）body is one of the key factors to realize the strong climbing ability and comfort of rack EMU. Aiming at the lightweight design of rack EMU body floor beam, a structural design method combining 2 D with 3 D based on modal analysis and topology optimization theory was proposed. Firstly, the topology optimization of the 2 D section of floor beam with the minimum strain energy was carried out by using the finite element analysis and the structural optimization design software, and the topology configuration of the coarse section was obtained. Then, based on the coarse topological configuration, the multi-objective topology optimization of strain energy minimization and modal maximization for the 3 D structure of floor beam were carried out to obtain the 3 D structure shape of floor beam containing modal factors. Finally, the new configuration suitable for the rack-rail floor beam section was constructed based on the two optimization results and the manufacturability of floor beam, and the finite element simulation results were compared, analyzed and verified under the same boundary conditions as the original structure. The results show that the strength, stiffness and modal performance of the configuration satisfy with the requirements of the rack EMU body, and the quality of the optimized structure is 6.835% lower than the original structure.关键词：Rack-rail;EMU body;Floor beam;Topology optimization;Modal analys
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发布时间：2022-11-10 - 摘要：In view of the blindness and contingency of the trial cutting method in traditional processing of spiral bevel gears, this paper proposes a processing adjustment method of designing grinding wheel section according to the curvature of the tooth surface. Firstly, the spiral bevel gear is simulated by CATIA to build a high-precision cutting model. In ABAQUS, the finite element analysis of the cutting model is carried out, and the contact spots are extracted. Then, according to the analysis results of the cutting model, the curvature and node offset of the tooth surface are calculated for contact area adjustment. Finally, the grinding wheel section is designed according to the cutter section and the offset of the tooth surface, which is called in the virtual grinding. The analysis results show that the contact performance and transmission performance of the gear after curvature adjustment are greatly improved, which indicates that the tooth surface curvature adjustment is realized by adding the grinding process, and it is in line with the actual process flow. It provides a new research method for transmission error optimization and contact area correction of spiral bevel gear system.关键词：Spiral Bevel Gear;Virtual simulation;FEM analysis;Tooth contact;Curvature adjustment
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发布时间：2022-11-10 - 摘要：The G-load simulation principle and kinematic relationship of three-axis manned centrifuge are analyzed. The numerical method is used to solve the G-load simulation loading section, and the accurate calculation of the main arm speed of the overload simulation loading section is realized by simulation. The existence of the rotational speed solution of the main arm of the unloading section is analyzed, and the boundary of the rotational speed solution is clarified, which can also guide experimental designers to design the overload curve. Under the condition that the existence boundary of the solution is satisfied, the high precision numerical solution is obtained, and the G-load simulation accuracy of different methods is analyzed by combining pure Gz G-load simulation and three-direction G-load simulation.关键词：Manned centrifuge;Kinematic;Differential equation;G-load simulation
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发布时间：2022-11-10 - 摘要：At present, more and more small-sized or even micro reducers are applied in the fields of national defense and military, medical equipment, aerospace, etc. In view of the large size of the current RV reducers, a small-sized RV Reducer is proposed. Firstly, based on the analysis of the basic structure of the small-sized RV Reducer, the size parameters of each part were determined, and the 3 D solid model was established by SolidWorks software. Then, the force analysis and strength check of the involute planetary gear and cycloid pin gear mechanism were carried out by the theory of force analysis and strength check for conventional RV transmission system, and the simulation is carried out by the finite element analysis software. Finally, by comparing the theoretical calculation results with the simulation results, the maximum contact stress errors of the involute planetary gear and the cycloidal pin gear tooth surface are up to 5.77% and 11.03%, respectively, which verifies the correctness of the theoretical analysis and the rationality of the structural design, and provides theoretical support for the subsequent research on small-sized RV reducers.关键词：Small-sized RV reducer;Structural analysis;Strength check;Simulation
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发布时间：2022-11-10 - 摘要：The working conditions of self-aligning bearings in rolling mills are complex. The actual life of the bearing often does not reach the design life as expected. Therefore, it is of great significance to study the global load distribution and local stress distribution of self-aligning roller bearing. The global model involving contact of a number of elements often results in a long calculation time and convergence difficulty. Firstly, proposes a new simplified finite element model of bearing based on Hertz contact theory, which can greatly improve the calculation efficiency. Then, the roller contact loading distribution of the global model is solved based on the interference fit amount of the shaft and the inner ring of the bearing. Finally, the displacements corresponding to the maximum contact load is used as the boundary conditions of the local model, and the stress distribution of the inner ring is solved. The results show that the loading ratio of the two rows of raceways and loading distribution of the contact are varied with working conditions. The interference fit amount specified in the present study makes the minimum Mises stress of the inner ring greater than 40 MPa. This will reduce the strength and fatigue life of the bearing.关键词：Rolling mill;Self-aligning roller bearing;Model simplification;Loading distribution;Interference fit
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发布时间：2022-11-10 - 摘要：In solving the boundary conditions of a hydrostatic motorized spindle, there are some certain errors between the boundary conditions calculated by the traditional empirical formula and the actual conditions. In order to solve this problem, an optimization algorithm based on response surface is proposed in this paper, which is based on the idea of composite experimental design. The mathematical models of air gap heat transfer coefficient between stator and rotor, forced convection heat transfer coefficient of spindle inner hole and temperature are established, which is also called the mathematical model of temperature field. By using ANSYS Workbench simulation analysis software, load the optimized convective heat transfer coefficient into the simulation model to solve the temperature field of the hydrostatic motorized spindle to solve the temperature field of the hydrostatic motorized spindle. After selecting the sensor measuring points for temperature measurement, the results are compared with the simulation results. The results show that: the maximum error between the front bearing simulation temperature measurement point and the experimental temperature point is only 9.41%, and the maximum error between the rear bearing measurement point and the experimental temperature point is 3.09%. And it verifies the effectiveness and reliability of the method to improve the simulation accuracy of the hydrostatic motorized spindle.关键词：Hydrostatic motorized spindle;Ansys workbench;Response surface optimization algorithm;Experimental study
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发布时间：2022-11-10 - 摘要：Gear crack failure is a high incidence of the electromechanical transmission system, and timely detection of the crack failure is of great significance to ensure the normal operation of the electromechanical transmission system. Proposes a non-invasive diagnosis method for gear crack faults based on the stator current signal of a three-phase AC asynchronous motor. First, establish a motor-gear-load electromechanical coupling model, and use the potential energy method to calculate the variable meshing stiffness of the gear under different crack lengths and angles; Then, the electromechanical coupling model is numerically solved by Runge-Kutta method to analyze the dynamic response of motor current under the influence of time-varying meshing stiffness. In response, by comparing the stator current spectra of healthy gears and cracked faulted gears, the current spectrum characteristics corresponding to the gear crack faults are revealed, and the drive system gear crack fault diagnosis criterion based on the analysis of the motor current signal is established. The motor driving experiment is carried out on the gear with crack fault, and the motor current signal under the influence of the gear crack fault is consistent with the numerical solution result. The proposed non-invasive diagnosis method of gear crack fault based on motor current signal is of high value for reducing the maintenance cost of transmission system.关键词：Time-varying meshing stiffness;Gear failure;Electromechanical coupling model;Motor current signal;Current characteristic analysis
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发布时间：2022-11-10 - 摘要：By collecting the hard points data of an independent brand electric vehicle, EPS dynamic model was established and the assistance characteristic parameters of the model were designed. The steering simulation test was carried out by using ADAMS software. The accuracy of the model was verified. Relationship between steering wheel input torque and EPS output torque were compared and analyzed under different conditions with and without assistance. Finally, the real vehicle road test and Adams vehicle simulation were used. The steering wheel middle position handling stability test was carried out. The test results show that the EPS system is reasonably designed and has good handling and stability under high-speed driving conditions.关键词：Electric power steering system;Multibody dynamics;Steering assist characteristics;On center steering test;Handling stability test
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发布时间：2022-11-10 - 摘要：Considering the effect of carbide coarsening and void nucleation and growth on the creep damage of Fe-Cr-Ni based austenitic stainless steel, a new creep damage constitutive model was established based on the hyperbolic sinh function, and material parameter optimization procedure of the model was also developed. In addition, a comparative assessment of extrapolated failure times for 3 creep damage models was undertaken for the standard uniaxial round-bar specimen using finite element software.The results show that the proposed constitutive model is capable to reflect the creep behavior of the material under different stress levels at 890 ℃. Compared with the failure time predicted by the widely used power law model（Kachanov-Robotnov model and Liu-Murakami model）, the prediction results of the current model can reflect the nonlinear relationship between stress and creep rupture time under double logarithmic coordinates in a wide stress range, so the prediction results are more reasonable.关键词：20Cr32Ni1Nb steel;Creep damage models;Finite element analysis
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发布时间：2022-11-10 -
FATIGUE LIFE ANALYSIS OF WING WITH HIGH ASPECT RATIO BASED ON BIDIRECTIONAL FLUID-STRUCTURE COUPLING
摘要：Based on the Miner linear cumulative damage theory and the finite element analysis method, the fatigue life of the wing with high aspect ratio at different angles of attack was calculated.Firstly, based on the N-S equation, the displacement, stress and strain of the wing structure in cruise state are solved by using the bidirectional fluid-structure coupling method.Secondly, the fatigue life of the wing structure is analyzed, and the fatigue life of the wing structure at the weak position and different angles of attack is obtained.The results show that the fatigue weakness of the wing with high aspect ratio tends to occur at the leading edge and the wing root, and the life of the leading edge increases from the wing tip to the wing root along the wing span.The life of the wing is closely related to the change of Angle of attack and airfoil parameters, and there is generally a maximum life Angle of attack under a given flight condition.关键词：High aspect ratio;Finite element method;Bidirectional fluid-structure coupling;Fatigue life- 6
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发布时间：2022-11-10 - 摘要：Gearbox is one of the core components of wind turbine, and the gear under heavy load is prone to fatigue fracture, which affects the normal operation of the generator. In this paper, the planetary-sun gear in the gearbox of 1.5 MW wind turbine is taken as the research object, and the finite element analysis model of fatigue crack propagation in the meshing process of gear pair is established through the joint programming of MATLAB and ABAQUS. The NASGRO equation is used to predict the residual fatigue life, and the influence of load and initial crack length on the fatigue crack propagation path and life is studied. The analysis results show that the simulation results of crack growth path based on the numerical model are in good agreement with the fatigue test results. At the same time, the meshing state of gear has a significant effect on the crack growth rate; the initial crack length has little effect on the crack growth path; the load amplitude will change the crack growth law under different meshing states, and the crack length and growth life will decrease with the increase of load.关键词：Wind turbine;Gear;Finite element analysis;Crack propagation;Fatigue life
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发布时间：2022-11-10 - 摘要：In this paper, an isogeometric analysis method is proposed to obtain the notch tip stress intensity factor for the plane fracture problem with V-notch. Based on the isogeometric analysis, which discretizes the overall structure and constructs the stiffness matrix of the structure, obtains the equilibrium equation, and simultaneously obtains the coordinate information of the nodes. Combined with the displacement expression of the plane with sharp notch in polar coordinate system, the node coordinate information of the whole field is substituted into the analytical expression after coordinate conversion to obtain a transformation matrix, and the isogeometric equilibrium equation is converted into a smaller-dimensional equation. The coefficients of the analytical solution of the displacement field can be calculated, and the stress field and the stress intensity factor of the notch are obtained at the same time. This method unifies numerical modeling and numerical calculation into one platform, which improves the efficiency of numerical analysis; avoids the grid-sensitive problem of iso-geometric analysis fracture problems, and the stress intensity factors can be directly solved without any post-processing program, and avoids the problem of inconsistency in the calculation of isogeometric equations.关键词：Stress intensity factor;Isogeometric analysis;V-notched plane;Displacement field;Stress field
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发布时间：2022-11-10 - 摘要：As an example of life evaluation of the weld between main girder and rigid leg of 580 t gantry crane based on structural stress method, the non-proportional stress characteristics of multi-axis are obtained by analyzing the working stress history of crane. The shell-solid mixed model with weld details in the dangerous position is built, and the multi-axial structural stress is obtained by combining the load spectrum with the ANSYS and Verity module of FE-SAFE software. The damage accumulation path is obtained by Path Dependent Maximum Range（PDMR）. Moment of Load Path（MLP） is introduced to realize the transformation from non-proportional loading path to proportional loading path. The fatigue life of the weld is estimated according to the master S-N curve and compared with the multi-axis proportional and uni-axial life estimation methods. It shows the necessity of multi-axial non-proportional fatigue analysis method, which provides reference for the complex multi-axial fatigue analysis of cranes.关键词：Structural stress method;Multi-axial fatigue;Non-proportional load path;Equivalent structural stress
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发布时间：2022-11-10 - 摘要：The stresses was analysis in press-fitting and in service, and fatigue was evaluated based on ANSYS software in this thesis. What’s more, the fatigue test was carry out, stiffness variation was analyzed before and after fatigue test. The result show that, the pressure ring is the largest Von-Mises stress component in press-fit, and the hoop tensile stress pay a important role. The Von-Mises stress on hole of pressure ring is 1.5 times than other component in service, and the hoop stress pay a important role. The weak anti-fatigue area of tyre is on back side of tyre, and The weak anti-fatigue area of pressure ring is on hole. No fatigue crack was found, and the stiffness variation was less than 20% after fatigue test.关键词：FEM;Resilient wheel;Stress analysis;Fatigue evaluation
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发布时间：2022-11-10 - 摘要：In view of the fact that most of the cracks in the coupler yoke are surface cracks with small depth and long length, the shallow surface crack propagation was simulated by FEA method for No.17 forged coupler yoke. The shape change of the surface crack was analyzed in the process of crack propagation, and the residual lives were predicted for the coupler yokes with different initial length and depth cracks. The results show that the shape of the elliptical surface crack of the coupler yoke changes and tends to be narrow and long during the propagation process. In the case of 0.5 mm and 1 mm initial crack depth, the residual lives of the coupler yokes were simulated for various crack lengths, and simulated results show that the forged coupler yoke has high anti-fracture resistance. For crack with the same initial length and depth, intermediate crack is more dangerous than corner crack. Based on the simulation results, a residual life prediction formula is obtained for the coupler yoke with the intermediate crack and corner crack under different initial crack lengths.关键词：No.17 coupler yoke;Shallow surface crack;Crack shape;Crack growth;Residual life
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发布时间：2022-11-10 - 摘要：According to the requirements of loading and unloading of safety valve, an automatic guide vehicle for safety valve handling is designed. Aiming at the established mechanical model of in-situ steering of truck, the simulation analysis of virtual prototype is carried out by using ADAMS simulation software. The steering motion under different wheel ground friction coefficient, steering acceleration time and eccentricity is simulated for many times. Based on the simulation curve of rotation center displacement and discrete points of relative displacement value in three-dimensional space, the uncertainty is compared and analyzed The simulation results and prototype tests verify the correctness of the theoretical analysis, which provides a basis for the optimization of the mechanical structure and the design of the control system of the carrier.关键词：Safety valve carrier;In situ steering;Mechanical modeling;Simulation analysis
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发布时间：2022-11-10 - 摘要：The regulation UN R127 is the must for the import country since 2018, In order to successfully pass the regulatory certification, so the pedestrian protection performance of the vehicle should be evaluated. In this paper, the pedestrian protection analysis was done by finite method, and the results show that the legform satisfy the regulation, but some area of the head don′t satisfy the requirements of the regulation. So some optimization analysis was made that aimed at the fail area to pass the UN R127 pedestrian protection certification test successfully. Comparing the optimized data of risk points with the experiment, the deviation is 1.9%, which shows the reliability of building the finite element model, and provide reference for the design and development of pedestrian protection for subsequent models.关键词：Pedestrian protection;UN R127;Headform impact;Finite element;Optimization;Test verification
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发布时间：2022-11-10 - 摘要：This paper investigated inherent characteristics of graphene reinforced conical shells with arbitrary boundary conditions based on Love shell theory. The mechanics model for graphene reinforced composites and the free vibration differential equation of graphene reinforced conical shells were deduced. Finally, parameter studies were carried out to evaluate effects of boundary conditions and material and geometric parameters on inherent characteristics of conical shells.关键词：Conical shell;Arbitrary boundary conditions;Artificial spring technique;Rayleigh-Ritz method
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发布时间：2022-11-10 - 摘要：In the design and research on the spaceborne connector of aerospace satellites, a joint optimization method is proposed. In order to reduce the problem of excessive bolt axial force of the spaceborne connector, a method with the variance of the bolt axial force as the objective function and constraint conditions is proposed. Free size optimization mathematical model, using OptiStruct optimization module for optimization simulation, a comparative analysis of the bolt loading before and after optimization, and a detailed description of the optimization iteration process; based on the optimization model, the size of the support plate is optimized design. The results show that after optimization by the proposed mathematical model, the axial force of the bolt is significantly reduced, which meets the expected requirements; The optimization target is affected by different factors in different stages of the iterative process; The structural fundamental frequency can be increased by optimizing the design. The optimization method provides a reference for the optimization of bolt strength and the structural design of spacecraft.关键词：Spaceborne connector;Free size optimization;Size optimization;Bolt strength;Optimal mathematical model
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发布时间：2022-11-10 - 摘要：To improve the wheel-rail relationship of high-speed EMUs due to the deterioration of wheel treads central hollow wear, wheel-rail matching characteristics of various treads were analyzed. Due to the loss of gravity stiffness restoring force, the wheel/rail creep increases and the bad contact becomes more and more severe. The matching relations of LMA, S1002 G, XP55 and typical hollow-worn profile were compared. It was found that the selection of profile should reasonably match the suspension characteristics of bogies. The larger contact spot area of LMA and the rail contact point close to the rail top is easier to form the conformal contact, which is not conducive to the delay of hollow-worn. The equivalent conicity of S1002 G and the position of the contact points change nonlinearly in the narrower scope, which is harmful to uniform wear; the peak of the contact spot area at the nominal rolling circle position of the wheel tread is easy to form the concentrated abrasion. XP55 maintains a（near） linear change in the equivalent conicity and contact spot area, and the initial rail contact position close to the rail gauge corner of 7 mm is benefit to overcome the conformal contact on the rail top. XP55 can be used for reference to optimize high-speed wheel-rail matching relationship.关键词：Wheel-rail matching;High-speed railway;Hollow-worn wheel;Equivalent conicity;Roll radii difference;Wheel-rail contact
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发布时间：2022-11-10
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