最新刊期
期 4 ， 2020
- 摘要：The change in the internal contact state caused by the failure of the rolling bearing is an important factor that causes the change in its vibration characteristics. According to the contact form of the fault and the rolling element,this paper considered the different sizes of the fault evolution process,and established the dynamic finite element model of the multi-body contact of the cylindrical roller bearing with different degrees of failure. The effectiveness of the model was verified by the experiment on the outer ring fault of the rolling bearing. Based on the explicit dynamics method,the dynamic contact force between the rolling element and each component and the contact strain of the fault area was analyzed,then the influence law of different fault degrees on the internal dynamic characteristics of the bearing and the change law of the contact deformation under the fault condition were revealed. The results show that the contact force of the rolling elements with the components is reduced when the defects are crossed. As the degree of failure increases,the fluctuation of the internal contact force of the bearing becomes more and more intense,but the fluctuation frequency and amplitude of the contact strain decrease. In the loading area,the rolling elements of faulty bearing are in contact with both sides of the cage pocket,which causing a negative contact force. The fault tends to expand along the rolling direction of the rolling element. The research conclusion can provide a theoretical basis for fault diagnosis and residual life prediction of rolling bearings.关键词：Rolling bearing;Failure;Contact form;Dynamic characteristics
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发布时间：2022-09-22 - 摘要：Macro fiber composites（MFC） have a good application prospect in aeroelastic buffeting control. The MFC actuator was modeled using the load simulation method. The aerodynamic forces were simulated by the doublet-lattice method and the control laws were designed applying the negative velocity feedback algorithm. The influences of airflow velocity on the inherent characteristics of vertical tail and the control mechanism of buffeting active control were studied. The results show that the airflow velocity affects the inherent characteristics of the vertical tail. The additional aerodynamic force,mainly including the part which is inverse phase with the velocity,plays an additional damping role on the system below the flutter velocity. The piezoelectric driving force can even do positive work,but can make the additional aerodynamic force consume more energy so that the total energy consumption of the system increases. The results can provide useful reference for the practical buffeting active control and its application.关键词：Buffeting control;Macro fiber composites;Airflow velocity;Negative velocity feedback;Control mechanism
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发布时间：2022-09-22 - 摘要：Aiming at the problems of traditional bearings fault diagnosis methods had such shortcomings as largely dependent on expert prior knowledge and difficulty in fault feature extraction,a method based on compressive sensing（CS） and improved deep wavelet neural network（DWNN） was proposed. Firstly,the collected vibration data of bearings were de-noised and compressed by CS. Secondly,the improved wavelet auto-encoder was designed to construct the DWNN,and the " crosslayer" connection was introduced to alleviate the gradient disappearance of the network. Finally,unsupervised pre-training of DWNN was performed using a large amount of unlabeled compressed data and supervised and fine-tuned with a small amount of tagged data to realize fault discrimination. The experimental results show that the method can effectively identify the bearings with multiple fault types and multiple fault severities,which is less affected by prior knowledge and subjective knowledge and avoids complex artificial feature extraction process. The feature extraction ability and recognition ability of proposed method are superior than artificial neural network,deep belief network,deep sparse auto-encoder and so on.关键词：Rolling bearing;Fault diagnosis;Compressive sensing;Deep wavelet neural network
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发布时间：2022-09-22 - 摘要：To improve damage identification efficiency,a damage identification method based on Kriging model was proposed. Sample points were chosen based on Latin hypercube sampling,and Kriging model was built using acceleration frequency response functions corresponding to the damage parameters;then,Kriging model with good precision was used to replace the finite element model to participate in the optimization process. Cuckoo algorithm was used to obtain the damage parameters,where the objective function with the minimum frequency response deviation was constructed. Plane truss model was used to verify the effectiveness of the proposed method. The results show that single damage of location and extent,multiple damages of extent can be both accurately and quantitatively identified by only one measuring point;the maximum error of identification is less than 1%;noise and location of measuring points have a little influence on damage identification results.关键词：Damage identification;Kriging model;Acceleration frequency response function;Extent identification
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发布时间：2022-09-22 - 摘要：The accuracy of dynamic threshold is low by using the weighted average method. In order to solve this problem,a dynamics threshold calculation method for swashplate bearing based on Bayesian inference is proposed by using the characteristics of the probability density of normal data and different fault type data. Firstly,the singular value decomposition was used to preprocess the vibration signal,and the influence of noise on the dynamic threshold calculation result was filtered out.Secondly,the fault frequency energy feature extracting method was used to extract the features of normal data and inner ring,outer ring and ball fault data. Finally,Bayesian inference method was used to calculate the dynamic threshold of normal data and inner ring,outer ring and ball fault data respectively. The data were obtained by using the fault implantation method,and the dynamic threshold experiments were carried out. The experimental results show that the proposed method which has higher true positive rate and lower false positive rate can correctly find the dividing point between the probability density curve of normal data and different fault type data. The proposed method improves the calculation accuracy of dynamic threshold.关键词：Bayesian inference;Bearing of swashplate;Dynamic threshold calculation;Probability density;Feature extraction
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发布时间：2022-09-22 - 摘要：The indicator of bearing degradation is one of the most important parts in the study of bearing. The effective indicators can help warn of degradation before bearing failure. In this paper,the entropy with time parameter is proposed as the degradation index. By introducing time parameter,the entropy based on wavelet packet transform is improved,and the Gaussian model is used to optimize the expression of the indicator. The data of run-to-failure is from FEMTO-ST Institute to verify the feasibility of the method. The experiment result shows that the indicator is less affected by the optional conditions. It can also characterize the degradation state under different working conditions and realize the early warning of bearing failure by calculating the its rate of change.关键词：Bearing degradation;Entropy with time parameter;Gaussian model;Failure warn
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发布时间：2022-09-22 - 摘要：Surface hardness is an important index for evaluating the quality of surface processing. Ultrasonic rolling and extrusion technology plays a very significant role in surface strengthening. Taking 42 CrMo bearing steel as the object,the range analysis was carried out on the orthogonal experiment results of ultrasonic rolling extrusion,and the significance of process parameters on surface hardness was obtained. The reliability and accuracy of BP neural network model and stepwise regression model were compared and analyzed in sections by using k-fold cross validation method. This process fully considers the fitting ability and prediction ability of the model. The results show that the validation error range and average error of the stepwise regression model are smaller,and the prediction accuracy of the model is higher. Finally,the established prediction model of surface hardness has strong overall and coefficient significance,which can be applied to the optimization and improvement of surface quality in ultrasonic rolling extrusion.关键词：Ultrasonic rolling extrusion;BP neural network;Stepwise regression;Prediction model;Surface Hardness
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发布时间：2022-09-22 - 摘要：Combined simulation and test to investigate the collapse failure mode and energy absorption characteristics of wingding carbon fiber reinforced composite（CFRP[± 45°/90°]）/Al hybrid thin-walled circular tube under quasi-static axial compression load. Failure mode,Load-displacement curves and energy absorption characteristics were obtained under quasi-static axial crushing tests. A finite element model of hybrid tube was established according to samples. The simulation results with good agreement with the test were obtained by ABAQUS/Explicit,and the crushing failure behavior of the hybrid tube under quasistatic load was reproduced. Based on the simulation results,it was found that the initial crushing load,average crushing load,specific energy absorption and load efficiency of the mixing tube were increased by 97. 6%,93. 3%,57. 8% and 5. 9%,respectively. compared with the aluminum tube. The staged peaks and valleys of the crushing load were selected to analyze the shape of hybrid tube and the failure state of the fiber damage. The results show that when the hybrid tube is complete the fiber plays the main bearing role. In the crushing failure stage,the fiber damage failure mode changes with fiber winding angle,the crushing morphology of aluminum tube and the bonding interface state of CFRP/Al. Subsequently,the energy absorption characteristics of CFRP/Al hybrid circular tubes with three different structure forms were compared. It was found that hybrid circular tube with CFRP[90°/± 45°] wrapped the outside of the aluminum has the best energy absorption.关键词：CFRP/Al;Hybrid thin-walled circular tube;Numerical simulation;Damage failure;Energy absorption characteristic;Structure form
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发布时间：2022-09-22 - 摘要：Based on the fatigue test of three-row parallel holes without prefabricated cracks,the law of multiple site damage（MSD） for multi-detail structures with similar stress levels was studied. In order to study the interference effect between the cracks in the MSD structure,the FRANC2 D/L was used to calculate and analyze the crack stress intensity factor of four cracking modes:main crack,equal-length double-sided crack,equal-length single-double crack and single-hole isometric crack. The calculation results show that the crack is mainly affected by the interference of the stress concentration of the cracked hole in the initial stage of crack propagation. The dimensionless stress intensity factors of the cracks are similar in the four modes. As the crack length increases,both the test and finite element results show that the interference between the cracks significantly accelerates the crack propagation rate.关键词：Multiple site damage;Structure containing holes;FRANC2D/L;Crack interference;Stress intensity factor
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发布时间：2022-09-22 - 摘要：In order to study the loosening mechanism of the flange joint bolt in the lateral vibration,the transverse fretting wear test of simulated fasteners was carried out by means of transverse vibration fatigue testing machine,and then the pretightening force and pre-loading of bolt joints under different lateral loads and frequencies were observed.,and measure the amount of wear and surface damage. The experimental results show that the bolt preload reduction is divided into two stages:the plastic deformation stage in which the pre-tightening force decreases rapidly and the fretting wear stage in which the pre-tightening force decreases slowly. The pre-tightening torque drop is divided into three stages:the first stage is not obvious due to the high local contact stress;the second stage is rapidly degraded due to the plastic deformation,and the third stage bolt enters the fretting wear. At the third stage,the pre-tightening torque begins to slowly decrease. Under low frequency vibration of the bolt,the amount of mass change is not sensitive to small changes in frequency. The surface wear of the bolt in contact with the clamp increases as the alternating amplitude load increases;it decreases as the frequency increases.关键词：Bolt connection;Lateral vibration;Pre-tightening force;Pre-tightening moment;Fretting Wear
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发布时间：2022-09-22 - 摘要：The π-joint is put forward and the configuration is designed to meet the need for capacity of pull-off and lateral bending,considering the influence of temperature condition. The test result demonstrates that filler area is the weakest part of the sandwich π-joints where the damage first appears,and determines the capacity of structure. The capacity of π-joint under pull-off load highly than lateral bending load,and the failure mode of sandwich π-joint is sensitive to elevated temperature too cold temperature dry condition.关键词：Composite material;π-joints;Temperature;Filler;Failure
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发布时间：2022-09-22 - 摘要：In view of the problem that the feeder often fails due to insufficient strength,the transient dynamics of a certain type of vibrating feeder under typical working conditions is analyzed based on the finite element method（FEM）. At the same time,the dynamic stress measurement under the corresponding working conditions is carried out. The results show that the main reason for the failure of the feeder is the unreasonable design of the spring upper seat structure. Therefore,based on the variable density method and substructure technique,a topology optimization model of constrained stress and volume fraction is established with the combined strain energy of spring upper seat as the optimization objective function,based on sensitivity analysis and least square method,a response surface model of first order torsion,bending frequency and total mass is established. At last,genetic algorithm is used to carry out the multiple object optimization to the response surface model,and the optimal solution set of Pareto is obtained. The results show that the natural frequencies of the optimized structures are increased by 4. 17% and 6. 30%,respectively. The maximum dynamic stress is reduced by 46. 4% and the overall stiffness and structural reliability of the feeder are improved.关键词：Vibrating feeder;Topology optimization;Sensitivity analysis;Genetic algorithm;Multi-objective optimization
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发布时间：2022-09-22 - 摘要：In order to reduce the weight of the steerable crash cushion,based on the collision resistance topology optimization method of hybrid cellular automata,the multi-condition topology optimization analysis of the energy absorption box of the steerable crash cushion was carried out,and the topology configuration of the energy absorption box was extracted. Moreover,the cross-sectional parameters of the rectangular cross-section energy absorption box are optimized by using orthogonal test design method and taking the maximum acceleration in the multi-condition collision of the vehicle as an evaluation index,and the optimal parameter combination of the rectangular cross-section energy absorption box is determined. Finally,the multi-condition finite element simulation analysis of the crash cushion before and after orthogonal test optimization is carried out,and the acceleration of the optimized crash cushion under forward collision condition is compared with that of the existing crash cushion.The results show that the energy absorption box obtained through optimization has better buffering performance than that before optimization,and can better protect the safety of passengers.关键词：Crash cushion;Crashworthiness topology optimization;Orthogonal experimental;Finite element
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发布时间：2022-09-22 - 摘要：In order to study the jitter problem of the left rear door of a certain SUV on the washboard road with speed of（12 ～ 15） km/h,a transfer path analysis（TPA） model is established by combining the working load test with the transfer function simulation. Based on the complex stiffness method,the dynamic load of the connecting point between the chassis and the car body is obtained. At the same time,the transfer function of the left rear door of the Trimmed Body（TB） model is obtained by the CAE method. The contribution of each transfer path to the target point is calculated. The reliability of the TPA model is verified by compared the combined value of each transfer path with the experimental value. According to the contribution of each path,it is found that the left connection between the lateral stabilizer rod and the car body is the main transfer path. Then,the dynamic stiffness of the connection of the transfer path is optimized to reduce vibration transmission ratio. The result shows that the peak value of the jitter acceleration is reduced from 8017 to 4236（mm/s~2）.关键词：Complex stiffness method;TPA model;Transfer path contribution;Dynamic stiffness
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发布时间：2022-09-22 - 摘要：With mechanical system becoming more and more complex. It is very important to research time-dependent kinematic reliability. In order to improve the efficiency and accuracy of mechanism kinematic reliability analysis. By means of the analysis of mechanism kinematic error by probability method. Based on the theory of maximum entropy and random process,the reliability model of time-domain error is established. The object of study is a 6-axis robot mechanism. The static and dynamic kinematic error was synthesized. Kinematics simulation analysis was conducted by using ADAMS. The solution could be computed with Monte Carlo method. Select 100 error samples for the first 5 periods. The kinematic error was estimated by ARIMA model.The principle of maximum entropy was applied to derive probability density function. The time-dependent kinematic reliability was then estimated by the model of time domain error. Compared with the simulation method,The correctness and validity of the time-domain error reliability model in the study of kinematic reliability are verified,which can provide the reference for future research.关键词：Mechanism;Model of time domain error;ADAMS;Monte Carlo method;Time-dependent reliability
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发布时间：2022-09-22 - 摘要：The present method of calculating equivalent failure probability did not take into account the influence of noncritical state of components on the reliability of valve system,which leads to insufficient reliability evaluation results. Therefore,a new calculation method of equivalent failure probability was proposed in this work. The failure probability data considering the difference of failure consequence were obtained by comparing the failure data with equivalent fault coefficient in Failure Mode and Effect Analysis（FMEA）. On this basis,Markov model and mathematical expectation method in probability theory were used to obtain the expected state transition times,and combined with the existence probability of all states. The failure probability data of non-critical state influence of components were quantitatively analyzed. The key components of the system were determined by the equivalent failure probability of parts and components using the method of Birnbaum importance calculation and analysis. The results show that the equivalent failure probability calculated method is better than the traditional that,in same condition.关键词：Equivalent failure probability;Reliability assessment;Markov model;Birnbaum reliability importance
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发布时间：2022-09-22 - 摘要：To solve problems of heavy calculation burden and low solution accuracy for redundant robot in inverse kinematics problem,a solution method based on improved fruit fly optimization algorithm（IFOA） was proposed. On the basis of FOA,the evolutionary equation is optimized by adding an improved strategy of learning worst individuals. The ability of the IFOA to break away from the local optimum and to find the global optimum is greatly enhanced. Experimental results of several typical functions show that IFOA has better global search ability,faster speed,higher accuracy and reliability,compared with FOA. In the application of inverse kinematics problem of the redundant robot,the accuracy,speed and stability were improved effectively,and is thus applicable to solve the inverse kinematics problem of redundant robot.关键词：Fruit fly optimization algorithm;Improved strategy;Redundant robot;Inverse kinematics problem
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发布时间：2022-09-22 - 摘要：Based on vehicle-track coupled dynamics and Archard wear models,the influence of different axle loads,friction coefficients and running speeds on the rail wear characteristics of small radius curve section in metro were analyzed and discussed.The results indicated that the left rail wear concentrated on the shoulder and the right rail wear concentrated on the middle of the rail head,and the cumulative wear amplitude of the left rail was greater than that of the right rail. When the axle load increases,both the left and right rail wear increases. When the friction coefficient increases,both the left and right rail wear increases. When the speed increases,the left rail wear increases and the right rail wear tends to decrease. Relative to the speed of 80 km/h,the left rail wear tends to develop towards the shoulder at 40 km/h,the middle of the rail head at 60 km/h,and the right rail wear is basically unchanged. Through analysis of the prediction of rail profile,it can be concluded that the left rail wear concentrates on the middle and shoulder of rail head. The wear on the shoulder is relatively large,and the maximum value is located at the rail transverse position 18. 506 mm,reaching 0. 820 mm. The right rail wear appears to varying degrees. The wear on the middle of the rail head is relatively large,and the maximum value is located at the rail transverse position 2. 082 mm,reaching 0. 170 mm.关键词：Metro;Rail wear;Vehicle-track coupled dynamics;Archard wear model;Profile prediction
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发布时间：2022-09-22 - 摘要：Based on the re-entrant mechanism,the microstructure of the star and the re-entrant hexagon is combined. This paper designs a new re-entrant honeycomb structure model（X-shaped structure）. For the structure model,the relative density is given to achieve the purpose of weight reduction. The axial tensile mechanical behavior of the structure is studied by finite element software ABAQUS. Tip re-entrant angle,the variation of cell wall thickness,external angle and material properties on effective elastic modulus and Poisson’s ratio are obtained. The numerical results show that the important factor of affecting the structure is the external angle. With the increase of the external angle,the effective elastic modulus and Poisson’s ratio will increase. When the external angle reaches about 67°,the structure is zero Poisson’s ratio structure. Meanwhile,with the increase of the cell wall thickness,the negative Poisson’s ratio effect of the structure is more obvious,and the effective elastic modulus is also larger. When the tip angle is smaller,the negative Poisson’s ratio effect is stronger. The results can be provided a new reference for the optimization design of the new negative Poisson structure.关键词：Negative Poisson ’s ratio;Re-entrant honeycomb structure;Mechanical properties;Lightweight structure
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发布时间：2022-09-22 - 摘要：Based on ABAQUS,the process of the high-energy pipeline rejection and anti-whipping performance of the Ω-shape anti-whipping restraints of the nuclear power plant are simulated and analyzed. By analyzing of the deformation and failure process of common U-shaped anti-whipping restraints,the Ω-shape anti-whipping restraint is proposed to replace U-shaped antiwhipping restraints and the specific geometric dimensions of the Ω-shape anti-whipping restraint are given. The model of pipe-Ω-shape anti-whipping restraints system is established,and its whipping process is analyzed by FEM software ABAQUS,which discloses that the Ω-shape anti-whipping restraint is able to remarkably reduce the stress peak and the maximum whipping force of the pipe--anti-whipping restraints system,thus improve the safety of the high-energy pipe system.关键词：High energy pipe;Anti-whipping;The U-type anti-whipping restraint;The Ω-shape anti-whipping restraint;ABAQUS
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发布时间：2022-09-22 - 摘要：Angular contact ball bearing is an important kind of component in the feed system of CNC machine,and its speed change during acceleration has great influence on its dynamic characteristics. Taking angular contact ball bearing 7603025 as investigation object,a dynamics analysis model of multi-rigid-body for angular contact ball bearing was established. Based on ADAMS method,the dynamic simulations of angular contact ball bearing in the acceleration process for different radial load,axial load and angular acceleration conditions were performed. The influence of radial load,axial load and angular acceleration on its dynamic characteristics including cage speed,centroid trajectory of cage and the contact force between rolling ball and cage in the acceleration process were studied,and the experimental verification was carried out. The study results show that the increase of radial load and angular acceleration will increase the impact force of rolling ball on cage,which cause the fluctuation of cage speed increase and the movement of cage centroid more unstable,and the increase of axial load will decrease the impact force of rolling ball on cage,which make the fluctuation of cage speed reduce and the movement of cage centroid more smooth. The simulation results were in good agreement with the experimental results,and the validity of the dynamic analysis model was verified.关键词：Angular contact ball bearing;Dynamics;Acceleration process;Cage
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发布时间：2022-09-22 - 摘要：Through the analysis of the transmission mechanism of the vehicle transmission system,the torsional vibration model of the 12-DOF multi-gap nonlinear powertrain system was established,and the transient shock response characteristics under various working conditions were studied. Taking the angular acceleration of the main reducer gear as the evaluation index of transient impact,the transient shock response characteristics of the transmission system with Declutch condition and Tip out condition were compared and analyzed. The results show that the dynamic decoupling between the engine and the transmission system will cause the transmission system to "oscillate". The corresponding relationship between the torsional characteristics of the torsional vibration damper and the transient impact of the transmission system under the tip out condition is studied by the control variable method. The results show that the stiffness of the first-stage of the clutch has more influence on the transient impact strength than stiffness of the second-stage,the transient impact of the transmission system is more obvious by adjusting the stiffness of the first-stage.关键词：Automotive transmission system;Sudden torque condition;Transient shock;Clutch torsional damper
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发布时间：2022-09-22 - 摘要：The catenary of full-compensated simple chain suspension widely used at present china railway was taken as the research object,and a dynamic simulation model of pantograph-catenary was established using the finite element method. The pantograph and catenary model were established as three dimensional flexible multibody systems,while the droppers were simulated as non-linear spring model. The coupling of pantograph-catenary system was found by the contact of pantograph and catenary. The form-finding analysis of catenary was carried out before the transient dynamic analysis of catenary. Results shows that fluctuating range of contact force between the pantograph and catenary increase gradually. In the same span,the largest force fluctuations appear in number1 and 7 droppers,tension and compression states appear in one cycle,It is more prone to damage than the rest of droppers which only bear tension force.关键词：Pantograph;Catenary;Dropper;Dynamic force
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发布时间：2022-09-22 - 摘要：The overall performance of aeroengine blades greatly affects the safe and stable operation of the aircraft. In this paper,after electron beam welding of TC4 titanium alloy blades of an aero-engine,fatigue cracks often appear in the welding seam during service,which lead to the failure of the blades. Combined with X-ray diffraction method and finite element simulation analysis results. The distribution of residual stress in welding seam and surrounding area of titanium alloy blade was studied and analyzed,and the change of residual stress before and after strengthening was explored. The experimental results show that the tensile stress appears on the weld seam and the surface of the surrounding area,and the vertical weld direction stress value is about + 36 MPa after welding;after strengthening,there is a large and uniform compressive stress on the surface,and the stress value is about-200 MPa. The results of finite element simulation show that the blade surface changes from tensile stress to compressive stress,and the stress state is improved obviously,and then the fatigue resistance of blade is improved. It provides theoretical basis and technical reference for anti-fatigue manufacturing of aeroengine blade surface.关键词：TC4 titanium alloy blade;Vacuum electron beam welding;The surface strengthening technology;The residual stress
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发布时间：2022-09-22 - 摘要：The initial residual stress and deformation of welded body was measured respectively with blind-hole method and digital level. The test of residual stress after vibration aging,thermal aging and shot peening and the test of deformation after processing were done. The results show that the initial residual stress of welded body can reach up to 300. 6 MPa. The maximum deformation of the guide rails is 2882. 07 μm,which means obvious deformation. After complex aging process,the maximum residual stress of two welded bodys respectively is reduced to 43. 8 MPa and 12. 1 MPa,which both below 50 MPa. After processing,the maximum straightness of the guide rail respectively is 26. 7 μm and 25. 4 μm,which is significantly reduced.关键词：Welding lathe body;Residual stress;Heat aging;Vibration aging;Shot peening;Straightness
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发布时间：2022-09-22 - 摘要：Based on the large size and high precision worm gear pair after the temperature rise of deformation as the research object,analyses the deformation characteristics of the deformation of parts,combined with the calculation of the different parts of the deformation,the main factors affecting backlash is determined. On the other hand to explore the influence of temperature rise on the indexing accuracy principle and level. For this kind of turntable under different temperature conditions at the time of assembly back gap value provides a calculation method,as well as provides a quantitative reference for practical use and maintenance.关键词：Temperature rise;Worm gear;Backlash;Indexing accuracy
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发布时间：2022-09-22 - 摘要：Surface defect is the main fatigue failure source of helicopter metal dynamic components. Depth data of impact pit defects on surface of aluminum alloy critical dynamic parts of helicopter were collected,and statistical analysis was conducted. Statistic results show that the depth of impact pits obey the exponential distribution,and a standard size is confirmed according to the size coverage of 90%. The impact pit formation and fatigue crack initiation life of aluminum alloy（2 A12）commonly used in aviation were investigated using finite element method combined with continuum damage mechanics theory,and the rationality of the method was validated through fatigue test results. The study shows that a rational fatigue analysis of impact pit defect must take the local residual stress and plastic strain into account.关键词：Defect statistics;Fatigue life;Impact pit;Finite element method;Continuum damage mechanics
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发布时间：2022-09-22 - 摘要：In order to improve the fatigue performance of the aviation lug structure,a finite element（FE） model of composite strengthening process which contains cold expansion and interference fit has been established. The influence of technological parameters on plastic deformation around hole and fatigue life of lugs has been analyzed. The residual stress test around the lug hole was carried out to verify the accuracy of the FE model. The results indicate that the plastic flow of the hole wall material with the mandrel makes the deformation of the hole wall unevenly distributed in the thickness direction. And the elastic-plastic boundary transfers to the outer side of the lug with the increase of the expansion amount. Further research shows that the maximum stress amplitude is always located at the wall of the hole and the mean stress level is the highest at the entrance when the lug structure is subjected to alternating loads. For the structure of TC4 titanium alloy lug,the increment of fatigue life can reach the maximization when the process parameters consist of 3% cold expansion and 1% interference fit.关键词：Titanium alloy;Lug structure;Composite strengthening;Process parameters;Fatigue life
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发布时间：2022-09-22 - 摘要：Using the damage editing theory,the random spectrum of road simulation test can be compiled to achieve the purpose of removing the small load and achieving the accelerated test. However,less literature dealed with the key technical issues of how to smoothly connect and reconstruct the retained payload fragments after the small payload is removed. In this paper,a random spectrum connection and reconstruction method based on signal windowing overlap is proposed. Comparing the effects of several common window functions on the connection reconstruction of measured random spectra,it is found that the Hanning window not only effectively solve the problem of smooth connection reconstruction of two-stage signals,but also does not introduce extreme load. Based on the measured load of a vehicle test field,combined with the time domain damage editing method,the experimental acceleration spectrum was constructed by using the Hanning window method. The validity and rationality of the windowed spectrum were analyzed from the amplitude and frequency domains. It is verified that the windowed spectrum completely retains the damage of the non-windowed spectrum and the power spectral density curves of the two are highly coincident. Finally,the vehicle simulation experiment is established by applying the accelerated spectrum. The experimental response spectrum is highly consistent with the target spectrum,and the effectiveness of the method is verified.关键词：Time domain damage editing;The window function;Durability test;Accelerated spectrum compilation
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发布时间：2022-09-22 - 摘要：The fatigue crack initiation of the fuselage structure skin under the uniform supercharged cyclic load of 0 ～ 7. 8 Psi was experimentally studied by the self-made aircraft fuselage skin uniform supercharged fatigue simulation device. The location of the fatigue crack initiation of the fuselage structure skin and the sequence of fatigue crack initiation are studied by finite element analysis. The research showed that under the uniform supercharged fatigue load,fatigue crack initiation occurred on the left and right sides of the nail holes. The fatigue crack initiation sequence is mainly related to the maximum Von-Mises stress value at the initiation site,but also related to the tightness of the connection between the skin and the stringer.关键词：Fuselage skin;Uniform supercharged;Fatigue crack;Initiation
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发布时间：2022-09-22 - 摘要：The main drive system of rolling mill is a complicated electromechanical system,as the main device of transmitting motion and torque. The factor of electromechanical coupling is one of the important reasons for the abnormal variation of torsional vibration. The paper mainly researched that the dynamic analyses of the torsional vibration of main drive system of rolling mill. Comparative analysis the torsional vibration of main drive system is obtained between considering electromechanical coupling and not considering electromechanical coupling. Then,the mechanical and mathematical models of the main drive torsional vibration system are established. Based on Matlab/Simulink simulation,the unstable state of the main drive torsional vibration system is used to be studied,and then the influences of the uncertain parameters on the torsional vibration of main drive system are analyzed. The results could be revealed the oscillation law for the torsional vibration of main drive system of rolling mill and provided a theoretical foundation for the formulation of control strategy.关键词：Main drive system;Torsional vibration;Electromechanical coupling;Rotational inertia;Natural frequency
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发布时间：2022-09-22 - 摘要：In order to reduce the vibration and possible damage in the shipping process,introducing negative stiffness in the vibration isolator,broadening the vibration isolation frequency,reduce the starting vibration isolation frequency,at the same time,proposed a nonlinear speed feedback control method of active control is used to suppress resonance. the research results show that the vibration isolator has good low frequency vibration suppression,high frequency of the vibration isolation effect,it can effectively reduce the vibration harm of missile;Linear velocity feedback combined with cubic velocity feedback can effectively suppress resonance and reduce the effect of non-resonance isolation.关键词：Negative stiffness;Missile storage and transportation;Vibration;Control
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- 97
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发布时间：2022-09-22 - 摘要：Wa-ri heavy load railway is taken as the research object in the paper,the rail profiles are observed before and after grinding. Based on the wheel/rail contact wear theory and the finite element model of high-speed wheel/rail steady rolling contact established by the mixed Lagrangian/Eulerian method,the four kinds of railway grinding profile are contacted with LM wheels,the optimal rail profile was selected. Results show that,the profile 1 TQI and wear rate are the maximum,When the profile 1 contact with LM,the distribution of contact point pairs is relatively concentrated,equivalent conicity is largest,the mass flow density and wear power maximum are the biggest,wheel/rail wear is biggest. the profile 3 TQI and wear rate are the minimum,the contact point distribution between profile 3 and LM tread is good,equivalent conicity is least,the mass flow density and wear power maximum are the least. Therefore,only from the perspective of wear control,the research shows that the profile 3 is the optimal grinding profile.关键词：Heavy load railway;Rail grinding;Wheel/rail contact finite element simulation;Wheel/rail abrasion;Creep characteristics
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- 148
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发布时间：2022-09-22 - 摘要：Aiming at the complex working environment and high failure rate of the gear transmission system,the dynamic analysis of the transmission system was carried out and the failure mechanism was explored. Considering the centrifugal force of the bearing steel ball,the time-varying stiffness model of the deep groove ball bearing is established according to the Hertz contact theory. The time-varying mesh stiffness of normal and crack-containing gears is obtained by the energy method. The gear-bearing coupling dynamics model of the gear transmission system is established by the lumped parameter method.Considering the parameter excitation factors such as transmission error and time-varying stiffness of the gear transmission system,the dynamic characteristics of the gear transmission system are simulated and analyzed,and the Vibration acceleration of the transmission system is obtained. The influence of crack failure on the dynamic response of the gear is analyzed. The correctness of the model was verified by bench test. The results show that the established dynamic model can well describe the dynamic characteristics of the fault-containing gear transmission system. In the time domain waveform diagram,a periodic shock signal is generated due to the presence of a crack fault,and a sideband is generated around the meshing frequency in the spectrogram.关键词：Time-varying stiffness;Root crack;Deep groove ball bearing;Dynamic response
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- 230
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发布时间：2022-09-22 - 摘要：Aiming at analyzing the looseness of skirt lock during operation,lateral vibration test was carried out. The effects of initial preload,transverse cyclic excitation ’s amplitude,removal times and thread type were investigated. The finite element simulation analysis was carried out to verify the effectiveness of the results. The test results show that the larger the initial preload and the smaller the amplitude,the less the skirt lock loosens. The removal times have no effect on the skirt lock loosens. Under the same conditions,the ordinary thread is more difficult to loosen than the trapezoidal thread. But because of the working nature of the skirt lock,the trapezoidal thread is selected. The research results are significance to the analysis of the causes of the looseness of the skirt lock and the design of anti loosing.关键词：Skirt lock;The alternating lateral load;Self-loosening ability;Preload
- 3
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- 41
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发布时间：2022-09-22 - 摘要：The vibration failure issue of the motor control unit during the vibration test was studied,and the reasons of the failure were analyzed by applying spectrum analysis method,the results showed that the coupled vibration is the main reason of the vibration failure. The optimization schemes against this problem were designed,the octave criterion was applied to design the component for avoiding coupled vibration,and the damping was increased to decrease the peak of the vibration response. The optimization schemes were verified by simulation and experiment,the results showed the vibration acceleration decreased by 23% ～ 31% using octave criterion design,and decreased by 25% ～ 34% through increasing damping. The conclusion can be drawn that two optimization ways can decrease vibration acceleration level obviously,and the fatigue durability of the product was improved.关键词：New energy vehicle;Motor control unit;Vibration fatigue;Durability;Damping
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发布时间：2022-09-22 - 摘要：QPQ treating solves rusty problems for concrete pump truck boom connecting pins. Analysis and comparison are implemented in the pins’ fatigue lives with QPQ and ordinary thermal refining. Method feasibility is verified,fatigue reliability being the theoretical basis. Maximum bending moment helps calculate the allowable fatigue load. Test-tooling simulates the assembly structures and actual working conditions. The results show that QPQ treatment slightly influences the surface hardness and fatigue life. References and bases are provided for the design calculation and surface treatment. QPQ treatment pins are trialproduced and they do well in some concrete pump trucks.关键词：Pins;Quench polish quench（QPQ）;Fatigue reliability theory;Test-tooling;Fatigue life
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- 129
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发布时间：2022-09-22 - 摘要：The microscopic mechanism of crack propagation behavior of single crystal tungsten under uniaxial loading was investigated by means of molecular dynamics. The effects of temperature and crystal orientation on crack propagation were analyzed. The results show that at different temperatures,the main deformation mechanism of the crack in the [001] direction were slip band,dislocation and blunting. As the temperature increases,the yield strength decreased as the crack propagation. At300 K and 500 K,the crack showed a rapid expansion after yield deformation,while at 700 K and 900 K,the crack showed a secondary yielding phenomenon. Besides,crack models of different crystal orientation were established. The results showed that the yield strength of the crack was the largest when stretching in the [111] direction,[110] is the second,[001] is the smallest,and the yielding platform appeared in the stress-strain curve of the [110]crystal orientation,indicating better plasticity and tensile properties,the main deformation mechanism were slip bands when the crack propagates germination. The crack in[111]orientation formed dislocations during the expansion process,and the crack expanded in the form of blunting and voids.The above showed that the crack in different crystal orientation had different microstruction evolution at crack tip.关键词：Molecular dynamics;Mechanical properties;Crack propagation
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发布时间：2022-09-22
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