最新刊期
期 3 ， 2022
- 摘要：In order to study the torsional vibration problem of the transmission system of a front-rear-drive MPV model, a 21-degree-of-freedom transmission system torsional vibration equivalent model was established based on AMEsim software, and the torsional vibration analysis of the established model was carried out through free vibration calculation and forced vibration calculation. The torsional vibration test of the vehicle transmission system is carried out, the simulation results are compared with the experimental results, and the accuracy of the simulation model is verified in two aspects: Modal frequency and torsional vibration response. Based on the established vehicle transmission system model, the moment of inertia, torsional stiffness and damping in the model are analyzed through sensitivity analysis. The conclusions obtained show that the six system parameters have a greater impact on the transmission system.The multi-parameter adjustment based on MATLAB genetic algorithm is adopted for these parameters. After adjustment, the torsion amplitude values at the transmission and final reducer are reduced by 20.16% and 23% respectively, which greatly reduces the torsion amplitude of the transmission system.关键词：Automotive powertrain;Torsional vibration;AMEsim;Genetic algorithm
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发布时间：2022-09-22 - 摘要：The vehicle body is an important bearing structure of railway vehicles, which can bear dynamic loads from passengers and bogies. The reliability of the structure is directly related to the service safety of the vehicle.Based on the existing vehicle body standard EN12663, this paper firstly studies the static strength and fatigue strength of the vehicle body, and identifies the static weak position of the vehicle body under standard load.In order to further identify the weak position of the vehicle body under service conditions, a rigid-flexible coupling dynamic model of subway vehicle is established based on the rigid-flexible coupling dynamic theory and finite element method.Using the modal stress recovery method, the dynamic weak positions in various service modes are identified, and the vehicle modes which contribute a lot to each weak position are analyzed.Finally, based on the subway rigid-flexible coupling dynamic model, the dynamic stress characteristic of vehicle body weak position under various service conditions is analyzed, and the service life of key welds of vehicle body structure is predicted based on monte Carlo sampling and Miner linear cumulative damage theory.关键词：Rigid-flexible coupling;Dynamics;Modal stress recovery method;Vibratory fatigue;Service life prediction
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发布时间：2022-09-22 - 摘要：Tooth surface spalls fault is the irregularly shaped partial pits on the gear surface. In the calculation of gear mesh stiffness. Common method is to simplify the tooth surface spalls to a specific regular shape for research, which has great limitations. Based on image processing, this paper extracted the edge features of the spalls fault, dissociated spalls area according to the pixels and fit the spalls width function. Based on the traditional potential energy method, mesh stiffness of the faulty gear is calculated more accurately and dynamics simulation are performed. Compared with the rectangular spalls fault, the mesh stiffness of the faulty gear after image processing can more accurately reflect the contour characteristics. Eliminating the stiffness and acceleration response mutation points caused by simplification. The proposed method has high versatility and is applicable to tooth spalls of arbitrary shapes.关键词：Tooth surface spalls;Image processing;Mesh stiffness;Spall shape;Dynamic response
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发布时间：2022-09-22 - 摘要：The background of fault diagnosis is from the prevention of accidents, and from the reverse progression of accidents to the fault subdivision of the failure stage.By studying the single fault and the coupled fault separately, this paper demonstrates that the current theory of fault diagnosis has been intervened and developed in the fault stage, and it is a rule method of subdividing the fault models into opposite and parallel layers. This method makes the research object a divergent system and cannot be solved.The whole process of laboratory experiments and field failures is tracked, and data analysis proves that failures are dynamic links that build each other in the rotor system, and show the corresponding “homogeneous“characteristics with the change of the “forward” phase of the fault state time, and expand the process layer by layer.Therefore, the application of fault diagnosis theory should be restored to the unified whole and the whole process system, which requires changing the direction of fault diagnosis, reversing the horizon, and mastering the main law of fault development in the unified whole and the whole process based on the "forward" and "homogeneous" methods of time history and fault nature, so as to lay a more solid theoretical basis for intelligent diagnosis.关键词：Reverse backwards;Fault subdivision;Forward;Homogeneity;Intelligent diagnosis
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发布时间：2022-09-22 - 摘要：Aiming at the problem of graphical feature representation of one-dimensional mechanical vibration signals, a bearing fault diagnosis method based on symmetric polar coordinates and residual network migration learning is proposed, which combines the powerful image classification and recognition ability of convolution neural network. Therefore, a bearing fault diagnosis method based on symmetric polar coordinates and residual network transfer learning is proposed in this paper. In order to highlight the fault characteristics of bearing vibration signals and take into account the calculation efficiency, the proposed method uses the symmetric polar coordinate method to convert the one-dimensional mechanical vibration signal into a mirror-symmetric snowflake map quickly and the transformation parameters and data sampling length are optimized synchronously by NSGA-II to obtain the image features with better distinguishability. Then, the transfer learning of residual network is used to train and classify. The bearing dataset of Case Western Reserve University which includes different rotational speeds and load is used to verify this method and a good recognition effect has been achieved.关键词：Fault diagnosis;Symmetric polar coordinates;Feature extraction;Transfer learning;Residual network
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发布时间：2022-09-22 - 摘要：Aiming at the problem that the characteristic distribution of rolling bearing vibration data collected under different speed environment is inconsistent and it is difficult to obtain the label of samples to be diagnosed, a fault diagnosis method based on deep migration network is proposed. In this model, a domain-shared feature extraction network is constructed. The convolutional neural network（CNN） is used to extract vibration signal sensitive fault features, and bi-directional Long short-term Memory is used to extract vibration signal sensitive fault features. BiLSTM) network to extract the time information of sensitive fault features; Then, CORAL loss and JMMD loss were embedded in the deep migration network, respectively. By minimizing the second-order statistical difference and the maximum mean difference of the joint distribution, the differences in the feature distributions of the source domain and target domain were reduced, and the common features of the two domains were extracted. Finally, add Softmax classification layer to realize fault status recognition of target data. The results show that the average recognition accuracy of this method is 97.87% when the target domain data is unlabeled, which is significantly higher than the other five popular adaptive fault diagnosis methods.关键词：Feature distribution;Domain adaptive;CORAL losses;JMMD loss
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发布时间：2022-09-22 - 摘要：Taking the unbalanced rotor system supported by rolling bearings as the research object, the variable step size Runge-Kutta method is used for numerical integration to obtain the dynamic response of the rotor system. According to the bifurcation diagrams, phase portraits and Poincaré maps under different conditions of increasing and decelerating, the bifurcation of coexisting attractor is analyzed, and the evolution process of its attraction region with the system parameters was revealed. The results show that when Hopf bifurcation, jump bifurcation and doubling bifurcation occur in the system with the change of rotating speed, there will be the coexistence of attractors. The jump bifurcation will lead to a sudden change in the topological structure of the basin of attraction, while the Hopf bifurcation and the doubling bifurcation have little effect on the basin of attraction. The research results can provide guidance for the operation of the system at different speeds, and provide theoretical basis for the smooth operation of the rolling bearing rotor system.关键词：Ball bearing;Rotor system;Jump bifurcation;Coexistence attractors;Basin of attraction
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发布时间：2022-09-22 - 摘要：Consider the coupling of shaft cracks, rotor eccentricity, electromagnetic force of the electromagnetic bearing, and friction force between the rotating shaft and auxiliary bearing, the Runge-Kutta method is used to obtain the electromagnetic bearing-rotor system under different fault conditions. Bifurcation diagram, maximum friction force distribution diagram, axis trajectory diagram, Poincaré mapping diagram, time response diagram, etc., specifically analyze the impact of different faults on the dynamic response of the system; identify the rub-impact phenomenon and bifurcation of the rotating shaft and auxiliary bearing Characteristics. Research shows that when a crack-rub-impact fault occurs, the system corresponds to the first-order critical speed, 1/2, 1/3 and 1/4 critical speed, and 3 times the critical speed threshold bifurcation characteristics. The change shows that the stability of the system decreases with the increase of the crack coefficient; the clearance between the rotating shaft and the auxiliary bearing has a significant impact on the dynamic characteristics of the system. When the clearance is small, the rotating shaft and the auxiliary bearing will continue to rub-impact, and the clearance After increasing, the movement of the system gradually stabilizes.关键词：Magnetic bearing-rotor;Auxiliary bearing;Rub-impact;Crack
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发布时间：2022-09-22 - 摘要：A rolling bearing performance degradation assessment algorithm based on single ring theorem in the random matrix theory is proposed to solve the problem that the traditional feature extraction algorithm is not sufficient to extract the useful information of the bearing under the industrial big data environment, and the constructed index is difficult to effectively characterize the bearing degradation process. Firstly, through segmentation, randomization, amplification and dimensional reconstruction of the bearing sampling data, a high-dimensional random matrix of the bearing at the current moment is established; Secondly, given the good high-dimensional data processing ability of random matrix theory, the distribution of eigenvalues of bearing random matrix is investigated by using the single ring theorem. Finally, the average spectral radius and the distribution of eigenvalue discrete points are used as degradation indexes to describe the degradation history of rolling bearings. The application research of the proposed method was carried out through the IMS rolling bearing full life test data, the research results show that the two quantitative indexes established by using the average spectral radius and the number of discrete points proposed based on the single ring theorem, can effectively describe the degradation process of rolling bearings and are more sensitive to the early anomaly state of rolling bearing.关键词：Random matrix theory;Single ring theorem;Rolling bearing;Degradation assessment;Mean spectral radius
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发布时间：2022-09-22 - 摘要：Aiming at the problem that the vibration frequency of conventional vibration exciter is small and can not realize the resonance of high stiffness components, Based on the superharmonic vibration characteristics of nonlinear vibration system, designed a nonlinear ultraharmonic vibrator exciter composed of 3 linear springs and 3 nonlinear springs. Established the dynamic model of the nonlinear ultraharmonic vibrator exciter, solved the nonlinear vibration amplitude-frequency characteristic equation by using the multi-scale method, and analyzed the theoretical feasibility of the vibration exciter to achieve third ultraharmonic resonance. Analyzed effects of excitation force amplitude, nonlinear stiffness coefficient and nonlinear damping coefficient on nonlinear vibration amplitude-frequency response. Carried out dynamic simulation of nonlinear ultraharmonic vibrator exciter by using ADAMS, and carried out the vibration experiment of the nonlinear ultraharmonic vibrator exciter. The results show that under the adjustment of the nonlinear spring, the exciter can achieve third ultraharmonic resonance, which verifies the rationality of the design of the nonlinear super-resonant exciter.关键词：Vibratory stress relief;Vibration exciter;Nonlinear vibration;Ultraharmonic resonance
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发布时间：2022-09-22 - 摘要：Aiming at the problem of vibration isolation design of turboprop engine single mounting surface vibration isolation mounting system, this paper proposes a method to optimize the stiffness parameters of the mounting system vibration isolator to achieve the vibration decoupling of the engine mounting system and the improvement of the vibration isolation efficiency. This paper takes a turboprop engine installation system as an example, uses this method to establish a six-degree-of-freedom installation system dynamics model, and combines the NSGA-Ⅱ genetic algorithm with the installation system dynamics analysis. While the vertical stiffness affects the design life, the multi-objective optimization of the vibration isolation efficiency and vibration decoupling of the installation system is realized. The optimization results show that the installation system has obtained high vibration isolation efficiency and vibration decoupling rate, and the comprehensive vibration isolation performance is good.关键词：Engine vibration isolation system;Isolator stiffness;Vibration decoupling;Vibration isolation efficiency;Multi-objective optimization
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发布时间：2022-09-22 - 摘要：Dynamic simulation is an indispensable means for the development of advanced suspension system. The accuracy of the model affects the efficiency of product development. The bushing components in suspension system have a great influence on the vehicle performance, so it is necessary to describe its complex nonlinear mechanical characteristics accurately when modeling the suspension system dynamics. However, the suspension bush model built in Adams can only roughly reflect its basic mechanical characteristics. In this paper, a high order fractional derivative three element parallel bushing mathematical model is applied. This model can better describe the higher-order and non-linear of the mechanical characteristics of the bushing viscoelastic element. Based on Visual Studio Intel Visual Fortran platform, combined with FORTRAN language and Adams built-in function rules, completed the compilation and compilation of bushing mathematical model, and built a suspension system dynamic simulation platform. Finally, sinusoidal sweep frequency, cement crack spectrum and S-curve excitation test are carried out on the dynamic K ＆ C test-bed to verify the proposed modeling method.关键词：Nonlinear dynamics;Viscoelastic characteristics;Fortran language;ADAMS;Modeling method
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发布时间：2022-09-22 - 摘要：In order to explore the effects of material properties, filling density, support structure and other parameters on mechanical properties and strength characteristics of 3 D printed products, an optimization design method of 3 D printed configuration based on strength requirements was proposed. The mechanical properties of the products were obtained through the simulation calculation of the finite element structure strength and the comparative analysis of the tensile test of the characteristic samples. The tensile strength of 3 D printed products with different internal structures has great differences when the packing density is the same. In theoretical analysis and experimental test, the tensile strength of concentric structures is higher, while that of folded lines and spirals is lower. The results have guiding significance for in-depth analysis of the relationship between the strength of 3 D printing parts and the filling structure, and provide research data support for the optimization design of 3 D printing parameters based on strength demand.关键词：3D printing;Internal support;Filling degree;Mechanical properties
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发布时间：2022-09-22 - 摘要：To explore the influence of external temperature and loading rate on itsrheological behavior and mechanism, the dynamic impact compression test was conducted on 022 Cr18 Ni14 Mo2 stainless steel by using the split Hopkinson compression bar test platformat at 2 000 s-1～5 000 s-1 and 25℃～400℃.The results show that the flow stress, strain rate sensitivity, strain hardening and temperature sensitivity of the sample are closely related to strain, temperature and strain rate. At a constant temperature, the flow stress, strain hardening effect, and strain rate sensitivity increase with the increase of strain rate.At a constant strain rate, the temperature sensitivity increases with the increase of temperature, and the sample exhibits a significant thermal softening effect. The strain rate sensitivity and strain hardening effect appear to weaken with increasing temperature. In addition, the microstructure observation by scanning electron microscope（SEM） shows that deformation twins are mainly present in the grains, and a deformation zone with positioning or stacking faults is present in the grains. Under high strain rate or low temperature conditions, the number of deformation zone in the grain is more. The deformation twins within the grains help to adjust the degree of deformation between the grains and improve the uniformity of sample deformation at high strain rate.关键词：Strain rate sensitivity;Temperature sensitivity;Deformation zone
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发布时间：2022-09-22 - 摘要：Steel pipeline has been widely used in oil and gas transportation industry because of its unique advantages. However, while providing services, the steel pipeline is easy to be corroded, resulting in volumetric defects, which makes the pipeline thinner and the bearing capacity weaker, further causes the pipeline leakage, and even serious safety accidents. Based on the simplified form of volumetric defects, this paper compares and summarizes the evaluation criteria and evaluation methods, and gives suggestions on the simplified form of defects. The critical factors of single defect and multiple defects on pipeline safety evaluation are sorted out, and the interaction rules of adjacent defects are summarized. Finally, the research direction of multiple defects and the application of machine learning in pipeline safety evaluation are prospected.关键词：Steel pipeline;Volumetric defects;Safety assessment;Multiple defects;Multi-physics field coupling;Machine learning
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发布时间：2022-09-22 - 摘要：Numerical control machining is widely used in traditional manufacturing industry and national defense strategic industry, and optimization of milling parameters is closely related to processing efficiency, quality and cost. Firstly, a constrained multi-objective optimization function is constructed as a parameter optimization model. Then, the ENDE-NSGA-II method is adopted to complete the parameter optimization. By adoption of the NDX crossover algorithm, CA sorting method and DE strategy can increase the search interval, ensure the population diversification distribution, and improve the convergence rate. The DMU125 P five-axis CNC machine tool combined with Matlab 2020 was used to complete the comparison experiment of processing parameters, quality and system steady-state. Experimental results show that in comparison with the traditional empirical processing method, the processing parameters optimized by the ENDE-NSGA-II method can improve the surface roughness and the processing quality of the workpiece, under the premise of ensuring the processing efficiency. And increase the wear resistance of cutting tools, improve economic benefits. In addition, it allows the system to reach steady state more quickly.关键词：Multi-objective;NDX crossover;CA sorting;ENDE-NSGA-II;Numerical control machining
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发布时间：2022-09-22 - 摘要：To raise the efficiency of finite element calculation of load distribution in large three-row roller slewing bearing, an equivalent modeling method using the combination of shell element and nonlinear spring element was proposed on the basis of the structural features of the assembly. The spring element was used to replace the load and deformation behavior of roller, and the shell element was used to simulate the contact area between the roller and raceway contact. The computational scale of the nonlinear contacts was reduced with this modeling approach, and the load distribution of bearing can be obtained efficiently with lower computational scale. The effectiveness of the finite element calculation model was validated with the static loading experiment. The roller-raceway contact analysis was conducted on the basis of the maximum contact load from the finite element calculation analysis. The stress distribution between the roller and raceway contact under different clearances was studied. The results show that the stress in the edge area of the roller-raceway contact increases with the increase of clearance, thus leading to the decreases of fatigue life.关键词：Slewing bearing;Load distribution;Clearance;Fatigue life;Nonlinear spring
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发布时间：2022-09-22 - 摘要：This paper introduces a multi-robot coordinated parallel system for sea towing. Due to the force and direction of the floating-base are constantly changing, it is easy to overturn the crane. Firstly, the system is divided into two parts: floating robot and suspended system, and the dynamic model of the two are analyzed by using hydrodynamic theory and ball-pendulum model. Then according to the characteristics of fluid-solid coupling, the concrete steps of solving the system response to waves are analyzed. Finally, the displacement of floating-base, swing of suspended object and tension of rope are obtained by comparing and simulating the system under wave condition. The conclusion is a good basis for the optimization and control of the system.关键词：Towing system;Hydrodynamic;Dynamic model;Fluid-structure interaction;Dynamic response
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发布时间：2022-09-22 - 摘要：Due to study the influence of interfacial slip on the bearing capacity of hydrostatic and hydrostatic ball bearings with small orifice throttling, the Reynolds equation of ball bearings considering interfacial slip was established based on the linear slip model of interfacial slip. The Reynolds equation and the oil film thickness equation are solved by the finite difference method and the relaxation iterative method. The oil film pressure distribution and bearing capacity of the hydrostatic ball bearing considering interface slip are calculated. The results study that the higher the oil supply pressure, the higher the rotational speed, the smaller the oil film clearance, the stronger the dynamic pressure effect and the greater the bearing capacity of the hydrostatic bearing. Considering the sliding effect, the interface sliding leads to the increase of oil film pressure, and the influence on bearing capacity has a critical value. When the oil film gap is larger, the critical value of slip coefficient is larger, the liquid slip effect is stronger, and the carrying capacity increases when the slip degree is lower than the critical value, but decreases when the slip degree is higher than the critical value.关键词：Hydrostatic and hydrostatic ball bearings;Orifice compensated;Interface slippage;Finite difference method;Load capacity
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发布时间：2022-09-22 - 摘要：The comprehensive performance of suspension directly affects the handling stability and riding comfort of the vehicle. The suspension performance of a domestic vehicle was verified. By using ADAMS/car software, the front suspension model with flexible stabilizer bar subsystem and the rear suspension model with flexible torsion beam subsystem are established to form the suspension system of vehicle with rigid-flexible coupling model. The displacement and force were applied to the suspension system respectively. The dynamic and elastic kinematics analysis were carried out, and the wheel alignment parameters under different characteristics were obtained. The simulation results show that the simulation values were basically consistent with the real vehicle K＆C test data. The comprehensive performance of the suspension of this model was more optimized than that of the standard model. At the same time, through the rolling acceleration, understeering and car rolling three aspects, the steady-state rotary road test was conducted to further verify that the steady-state characteristics of the vehicle meet the design requirements and have good motion characteristics.关键词：Rigid-flexible coupling model;Adams/Car;Wheel alignment parameters;KC characteristic parameters
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发布时间：2022-09-22 - 摘要：In this paper, the structure design and optimization of the column of the tree-shaped parking garage are carried out. The base dimensions are 2.4 m、0.7 m and 8.5 m respectively. The simplified model of column takes into account the axial stress caused by the total weight FN of each component and the bending stress caused by the suspended loading plate and the vehicle. The maximum stress is easy to occur at the root of the column. The calculated results are 63.06 MPa, less than allowable stress 117.5 MPa, maximum deflection 8.93 mm, much less than standard value 113.90 mm. In order to meet the requirements of strength and deflection displacement, the penalty function method is used to optimize the size of the main support of the column, and the optimized model is measured and compared with the software analysis. Under the same working condition, the stress change data at the root of the column are collected by the test instrument and compared with the software analysis. The stress at the same position is less than 10% of the deviation between the measured and the simulated analysis results. The design and analysis of column structure are carried out by combining finite element analysis with actual stress test, and the mixed penalty function method is used to optimize the column structure. The results show that the method is effective. It provides some means and reference for the analysis of this kind of project.关键词：Stereo garage;Column;Mixed penalty function method;Structural design;Stress analysis
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发布时间：2022-09-22 - 摘要：In order to achieve the rapid measurement change of the rectangular pipe jacking machine and expand the application scope of the equipment, based on the DPLEX drive form, a modular cutterhead and main drive of the variable measurement rectangular pipe jacking machine are designed. One set of cutterhead is equipped with two sets of drives to form a set of module that is easy to disassemble and replace. Multiple modules must be used in combination to ensure that at least 4 crankshafts support a set of cutterhead. Based on the force analysis of the module, the ANSYS was used to carry out static analysis and modal analysis on the cutterhead and crankshaft, and the stress value, deformation and inherent frequency of the cutterhead and crankshaft under the maximum load condition were obtained; Through the rigid-flexible coupling dynamics simulation, the crankshaft load spectrum is obtained. And the fatigue analysis of the crankshaft is carried out based on nCode DesignLife. The results show that: in the construction of soft soil layer, the maximum stress of the cutterhead is 229.7 MPa, which is lower than the yield strength of the material, the safety factor is 1.55, the inherent frequency of the cutterhead at the first six orders range from 179.3 Hz to 196.5 Hz; the maximum stress of the crankshaft is 491.4 MPa, which is located at the front spindle at the neck fillet, the safety factor is 1.89, and the inherent frequency of the crankshaft at the first six orders range from 333.4 Hz to 1 304.5 Hz. The main fatigue damage points of the crankshaft are concentrated at the fillet of the front main journal, the minimum number of cycles is 3.37×10~7, and the theoretical life is 165 928 h. It can meet the tunneling needs of the pipe jacking machine.关键词：Variable measurement rectangle pipe jacking machine;Cutterhead;Main drive
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发布时间：2022-09-22 - 摘要：Hot molten salt storage tank is the key energy storage equipment in solar thermal power stations. The accidents of similar equipment indicates that there is a risk of periodic cracking for storage tanks based on general strength design specifications. Based on the high-temperature structural strength design theory, risk-informed design methods were introduced to a 100 MW CSP plant. Quantitative control indicators for risk sources were reversely calculated. The results show that when the equivalent friction coefficient of bottom plate is greater than 0.65, the tank could have ratchet damage during heat-up stage. When the thickness of sand layer is greater than 60 mm, the sidewall of the storage tank could be instantaneously fractured. The range of temperature fluctuation should be limited between-20℃ and +25℃ to avoid high cycle fatigue fracture and buckling. Meanwhile, it is recommended to appropriately increase the center height of the tank bottom（<29 mm） to prevent thermal stress failure.关键词：Hot storage tank;Risk-informed design;Friction;Foundation settlement;Temperature fluctuation
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发布时间：2022-09-22 - 摘要：Based on the dynamics theory of rolling bearings, the fluid-solid-thermal three-phase coupled numerical analysis method is used to study the temperature field and strength of the cage in the ultra-low temperature environment. The influence of the temperature distribution, stress distribution and inlet flow rate of the cage on the fluid flow rate and fluid pressure is obtained. The results show that the temperature of the cage decreases with the increase of the inlet flow rate and the maximum temperature is at the circumferential position of the pocket; the cage stress increases with the increase of the inlet flow rate and the maximum stress is at the axial position of the pocket.Research can provide reference for solving bearing life extension and reliability problems in ultra-low temperature environment关键词：Ultra-low temperature;Cage;Fluid-solid-thermal coupling;Temperature field;Strength
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发布时间：2022-09-22 - 摘要：Aiming at the problem of thermal fatigue of solder joints for airborne electronic equipment, the evaluation method of thermal fatigue life of solder joints suitable for engineering application was studied, considered that the empirical equation based on strain energy was suitable for multiple components on PCBA. The accelerated test method of thermal fatigue life of solder joints was discussed, the accelerated test case proved that the test was feasible, and the simulation was credible. The results indicated that the simulation and accelerated test method of thermal fatigue life of solder joints were suitable for engineering application.关键词：Airborne electronic equipment;Solder joints;Thermal fatigue life;Simulation;Accelerated test
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发布时间：2022-09-22 - 摘要：In order to more accurately grasp the health status of key parts of heavy-haul wagon, the crack initiation life of the structure under existing service conditions is one of the important links of the research. In order to accurately analyze the fatigue crack initiation life of heavy-haul wagon coupler knuckle, an analysis manner of fatigue crack initiation life based on the separated body model is proposed. Firstly, the uniform load model based on strain test points, the contact force model based on contact nonlinearity, and the load distribution model based on load-bearing characteristics were constructed respectively, three types of knuckle crack initiation life models under different load conditions; Then, the finite element simulation under the three load-bearing conditions and bench test results of the knuckle are compared and analyzed, and it is proved that the elastic strain calculation results of each test point in the uniformly distributed load model based on strain test points are in good agreement with the results of bench test; Finally, based on the uniform load model and the local stress-strain method, the fatigue crack initiation life analysis of the heavy-haul wagon coupler knuckle is carried out. It shows that the dangerous part of the knuckle fatigue damage is the roots of the upper and lower traction flanges. Under specific load spectrum conditions, 95% confidence and 90% survival rate, its fatigue crack initiation life is 12 200 kilometers.关键词：Heavy-haul wagon coupler knuckle;Local stress-strain method;Fatigue damage;Crack initiation life
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发布时间：2022-09-22 - 摘要：In order to avoid dependence of structural local detailed strain/stress spectrum of the traditional Time Correlated Fatigue Damage Editing method, a Spectra Two-dimension Time-domain-threshold Editing（STTE） method was proposed for the problem of spectrum compilation of vehicle road-load-simulation testing. Taking vehicle road-load-simulation testing as an example, the testing target spectrum was developed by applying the STTE method combined with the pseudo damage retention principle. Theoretical analyses and test bench results showed that the developed accelerated spectra not only shorten test time effectively, but also well retain characteristics of the original load spectra. Additionally, the accelerated spectra well realized spectrum simulation and durability evaluation effect under the test bench condition. The proposed STTE method can provide reference for load spectrum editing of vehicle road-load-simulation testing.关键词：Road-load-simulation test;Load spectrum compilation;Accelerated durability testing
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发布时间：2022-09-22 - 摘要：Rack-pinion pumping unit is widely used in Xinjiang oilfields. In order to analyze the pitting damage and fatigue life of gear in rack-and-pinion pumping unit, Firstly, the model of rack-and-pinion was established, the elements of tooth surface and root were extracted for static strength analysis, and then compared with contact theory; Secondly, Pitting defects of different sizes were established by elements editing, and the influence of pitting growth on contact stress was analyzed; Finally, fatigue life under different pitting effects was calculated based on linear fatigue damage theory. The results show that with the growth of pitting defects, the contact stress increases and the fatigue life decreases; The pinion interference occurs in the transition section, the stress concentration is worst, and the fatigue life is low, the overall fatigue damage starts from the tooth top; The pitting extend along the tooth profile direction mainly affects the duration of stress concentration, and along the tooth width mainly affects the amplitude of stress change.关键词：Rack-Pinion pumping unit;Long ring rack;Pitting defects;Pitting growth;Fatigue life
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发布时间：2022-09-22 - 摘要：The failure of the welding seam between the end of 100 plunger and the shaft head of the multi-stage hydraulic cylinder used in off-highway dump truck occurred in the mining area. Through the chemical composition, weld microstructure and microhardness of the weld of the failed parts and the micro detection of the fracture weld, the failure reason was found out. Optimized design was carried out from the aspects of parts material, weld structure, process control and part structure. Based on ABAQUS software, fatigue simulation analysis and bench test were carried out on the weld, which effectively verified the consistency of design optimization and bench test and reduced the failure rate. It has certain guidance and reference significance for similar products.关键词：Multi-stage hydraulic cylinder;Fracture;Fault;FEA;Bench test
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发布时间：2022-09-22 - 摘要：So far, most of the numerical studies on shot peening are limited in the effects of shot peening parameters on the residual stress and surface morphology. There is still lack of numerical research on shot peening parameters on the hardness. Against this issue, studies are carried out for shot peening parameters on the hardness of 18 CrNiMo7-6 alloy steel based on a random multi-shot finite element model and empirical relationship between yield strength and Vickers hardness. Numerical results show that the surface hardness increases with coverage rates, and the thickness of hardness layer increases with the radius and velocity of shots.关键词：Shot peening;Vickers hardness;18CrNiMo7-6 alloy steel;Random multi-shot finite element model
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发布时间：2022-09-22 - 摘要：Based on the three-dimensional W-M fractal function, a three-dimensional rough surface was bulidt by SOLIDWORKS, and then the three-dimensional ball-rough surface contact numerical model of torsional fretting with the energy wear law being introduced by the user subroutine UMESHMOTION was established by ABAQUS. Thus, the influence of initial surface roughness on the frictional wear process of torsional fretting was studied. Firstly, the reasonability of the rough surface model was verified by the analytical solution of dimensionless contact area in G-W model. Simultaneously, in comparison with experimental wear results, the accuracy and validity of the numerical model for predicting torsional fretting wear was proved. The research results show that the change of surface roughness has a significant effect on torsional fretting wear. To be specific, wear volume, friction dissipation energy, and wear rate all increase with the increase of surface roughness, which indicates that initial surface roughness can aggravate surface wear. And friction activation energy decreases with the increase of surface roughness. It is clear that the rougher the surface, the lower the threshold for wear activation. Therefore, reducing initial surface roughness can effectively alleviate the torsional fretting wear.关键词：Torsional fretting;Energy wear law;UMESHMOTION subroutine;Wear activation energy
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发布时间：2022-09-22 - 摘要：Aiming at the phenomenon that the output gear of a shift actuator developed by an enterprise breaks in the working process, using the finite element analysis method to simulate the multi-body dynamics of the gear system. The stress distribution cloud diagram of the output gear and the output shaft during the movement shows that the maximum equivalent stress value of the output gear has exceeded the yield strength of the material, and the maximum equivalent stress value of the output shaft is close to the yield strength of the material. Improve the structural weaknesses of the output gear and output shaft, simulate the improved gear system and carry out the overload test to verify. The results show that the maximum stress value of the output gear and the output shaft is significantly reduced, which meets the strength requirements of the gear system and improves the reliability and safety of the shift actuator.关键词：Shift actuator;Gear system;Simulation;Structural improvement
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发布时间：2022-09-22 - 摘要：Circular arc tooth line cylindrical gear is a kind of cylindrical gear with convex and concave curve teeth which is processed by spiral bevel gear milling machine. The tooth line of this kind of gear is circular arc, and has the characteristics of symmetry about the central section of tooth width. The mathematical model of circular arc tooth profile circular arc tooth line cylindrical gear is established according to spiral bevel gear milling principle, and the 3 D solid model of double-arc tooth profile gear and quadruple-arc tooth profile gear is established according to the gear mathematical model. Finally, the contact stress analysis of the gear is carried out by using the finite element analysis software, and the static contact stress are obtained, the contact stress of quadruple-arc tooth profile gear is about 80% of the double-arc tooth profile gear. The research results can provide a theoretical basis for the design and application of circular arc tooth profile circular arc tooth line cylindrical gear.关键词：Circular arc tooth profile gear;Circular arc tooth line cylindrical gear;Finite element method;Contact stress
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发布时间：2022-09-22 - 摘要：In order to improve the fault diagnosis accuracy of railway vehicles pantograph, a fault diagnosis method of pantograph based on variational mode decomposition（VMD） dispersion entropy（DE） and support vector machine（SVM） was proposed in this paper. Firstly, VMD was used as the fault signal decomposition method to realized pantograph signal in different states adaptively decomposition, and obtained several intrinsic mode functions（IMF）. Secondly, DE was used as feature extration method to calculated each IMF DE value and obtained the fault feature vectors. Finally, SVM was used as pattern recgnition method to identified the fault features and the diagnosis results are obtained. An example of pantograph fault diagnosis shows the effectiveness of the method.关键词：Variational modal decomposition;Dispersion entropy;Support vector machine;Pantograph;Fault diagnosis
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发布时间：2022-09-22 - 摘要：In order to improve the optimization effect of the fruit fly optimization algorithm（FOA） on support vector machine（SVM） parameters, the evolution strategy of FOA was improved, and the duoble group coevolution fruit fly optimization algorithm（DGCFOA） was proposed in this paper. The DGCFOA was used to optimize the parameters of SVM and then used to gearbox fault diagnosis. Diagnosis results show that DGCFOA algorithm can obtained better SVM parameters when compared with FOA, it significantly improved fault diagnosis accuracy of gearbox. In addition, the diagnosis results also show that DGCFOA has higher diagnostic accuracy and more obvious advantages when compared with some other methods.关键词：Fruit fly optimization algorithm;Coevolution;Support vector machine;Gearbox;Fault diagnosis
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发布时间：2022-09-22 - 摘要：Somoss Imagine 8000 photosensitive resin was used to prepare test parts with various shapes, such as plane, bridge, round hole, nut, etc., by stereo lithography appearance. The surface accuracy, dimensional accuracy, tensile properties and printing time of different shapes under different layer thickness were studied. The results show that the surface accuracy of the test piece is the worst when the thickness is 0.06 mm, and the best when the thickness is 0.08 mm. The dimensional accuracy of the upper support surface of the test piece decreases with the increase of the thickness of the layer. If the thickness is too small, the “Z” axis surplus phenomenon appears, which leads to the increase of the dimensional accuracy in the height direction. However, the thickness of the layer has little effect on the dimensional accuracy in horizontal direction. The dimensional accuracy of the bridge, the fine gap, the wall thickness and the nut were the worst when the layer thickness was 0.06 mm.The dimensional accuracy is better when the layer thickness is 0.1 mm and 0.08 mm.When the thickness increases from 0.08 mm to 0.1 mm, the tensile strength decreases from 48.98 MPa to 46.62 MPa, which decreases by 4.8%.Elongation decreases from 2.4% to 1.6%, all less than 5%, indicating that the strength of the material can be improved by appropriately reducing the thickness of the layer. The layer thickness is inversely proportional to the printing time. When the layer thickness increases from 0.06 mm to 0.1 mm, the printing time is shortened by 67% and the printing efficiency is improved.关键词：Stereo lithography;Dimensional accuracy;Surface accuracy;Tensile strength
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发布时间：2022-09-22
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