最新刊期
期 5 ， 2020
- 摘要：Deep learning is good at abstract features from massive data and has good generalization ability,which has attracted more and more researchers’ attention. The Convolutional Neural Network（ CNN） is a classic structure of deep learing and which is being widely and successfully used in the fields of computer vision,target detection,natural language processing,and speech recognition. Based on a detailed analysis of the current status and needs of mechanical system fault diagnosis,this paper introduces the structure of CNN,and summarizes the application of CNN in the field of mechanical faults from the aspects of input data type,network structure design and migration learning. The problems of deep feature extraction and visualization are also discussed,and finally,the difficulties in mechanical fault diagnosis are analyzed and several problems to be solved in the field of mechanical fault diagnosis based on CNN are prospected.关键词：Deep learning;Convolutional neural network;Big data;Condition monitoring;Fault diagnosis;Transfer learning;Feature extraction
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发布时间：2022-09-22 - 摘要：In order to improve the rolling bearing fault diagnosis accuracy,this paper presents a fault diagnosis method based on Ensemble Empirical Mode Decomposition（ EEMD） and Convolution Neural Networks（ CNN）. At first,using the EEMD decompose the signal. After that,choose appropriate IMFs according to the correlation coefficent and kurtosis calculating results to reconstruct the signal. After calculating a series of indexes of reconstructed signals,using CNN and various methods to diagnose faults. The results shows that the method used in this paper can effectively carry out fault diagnosis. The accuracy can reach 96. 7%. It has certain application significance to fault diagnosis.关键词：Ensemble empirical mode decomposition;Convolution neural network;Fault diagnosis;Machine learning
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发布时间：2022-09-22 - 摘要：In order to extract effective features of complex signals,a fault diagnosis method combining short-time Fourier transform and two-dimensional convolution neural network is proposed. First,a short-time Fourier transform is performed on the rotating mechanical vibration signal to obtain a time-frequency map. Then,the time-frequency map is input into a two-dimensional convolution neural network for identification,and a final classification result is obtained. The method is applied to the fault diagnosis of rolling bearing and gearbox,and has achieved good results in the data of the Case Western Reserve University and the PHM2009 dataset.The correct rate is better than the direct comparison of the original signal into CNN,which verifies the superiority of the method.关键词：Rolling bearing;Gearbox;Fault diagnosis;Convolution neural network;Short-time Fourier transform
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发布时间：2022-09-22 - 摘要：With the continuous improvement of the running speed of the EMU,the wear of the wheels during the operation is intensified,which increases the maintenance cost and deteriorates the service environment of the train. In severe cases,it will threaten the safety of driving. Aiming at the polygon problem caused by wheel running wear,the dynamic high-speed EMU of a certain type of line is taken as the research object. The dynamic model was established by SIMPACK,and analyzed the influence of wheel polygon（ polygon number 1 ～ 11,wheel polygon amplitude 0. 1 mm ～ 0. 5 mm） on the vertical vibration response of high-speed wheel-rail system. In order to visually observe the relevant changes,a coefficient of decision was introduced and the curve is fitted to its variation. The results show that the influence of the wave depth of the wheel polygon on the vertical vibration response is more significant. The obtained fitting curve provides reference for the detection and maintenance and safety assessment of the high-speed EMU.关键词：High-speed EMUS;Wheel polygon;Vertical force;Acceleration;Fitting curve
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发布时间：2022-09-22 - 摘要：It is difficult to extract the fault features of gearbox gears under the condition of variable rotation speed,because of the order signals interfere with each other. To solve this problem,a fault feature extraction method for gearbox gears based on VMD（ Variational Mode Decomposition） and order tracking technology is proposed. The method resamples the vibration signal in angular domain by computed order tracking technology. After obtaining the resampled signal,it would be adaptively decomposed by VMD according to the different center order,and then select the fault signal fron the IMFs（ Intrinsic Mode Function） by kurtosis criterion. Finally,the fault signal is processed by the fast kurtogram,filter and squared envelope demodulation. Through the gear fault test and comparative analysis of gearbox at variable rotation speed,it shows that this method can effectively extract the gear fault characteristics of gearbox at variable rotation speed. It has obvious noise reduction effect and clear features,which is suitable for gear fault feature extraction of variable rotation speed gearbox.关键词：Variable rotation speed;Order tracking;VMD;Gearbox;Fault feature extraction
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发布时间：2022-09-22 - 摘要：In order to solve the problem of complex fault diagnosis of gearbox,the DCNN（ Deep Convolution Neural Network） was combined with the XGBoost（ e Xtreme Gradient Boosting） algorithm to establish the fault diagnosis model. Firstly,the DCNN Model was used to adaptively extract the feature matrix of the original vibration acceleration signal. Secondly,the feature matrix was used as input data,and the parameters of XGBoost algorithm were adjusted by lattice parameter method,then the XGBoost model was obtained. Most after that,the XGBoost model was trained by the feature matrix,so the gear box fault diagnosis model of DCNN-XGBoost was obtained. In order to verify the validity of the model and the superiority of XGBoost algorithm,the model was compared with three models: DNN-BP（ Back Propagation neural network） model,DCNN-RF（ Random Forest） model and DCNN-SVM（ Support Vector Machine） model. The DCNN feature matrix and the artificial feature matrix were analyzed by t-SNE visualization algorithm,the results show that the visualization effect of DCNN feature matrix obtained is better than that of artificial feature matrix; Compared with XGBoost,the stability of Random Forest is not as good as that of XGBoost algorithm; Compared with BP neural network, XGBoost algorithm has some advantages in preventing over-fitting; The combination of SVM and DCNN has some limitations. Finally,the diagnostic accuracy and time of DCNN-XGBoost model is better than that of other models.关键词：Gearbox;Fault diagnosis;Convolutional neural network;XGBoost
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发布时间：2022-09-22 - 摘要：Taking advantage of the EUM-25 K20 tension-torsion fatigue testing machine by CARE,the cryogenic uniaxial ratcheting tests were carried out for the S30408 specimens with and without weld,and with 0%,8%,and 12% pre-strains at110 K. It is shown that ratcheting behavior of specimens with and without weld is closely related to mean stress,amplitude stress and loading history. Because of the softening effect of a small amount of ferrite in weld metal,the initial ratcheting strain of weld specimen and ratcheting strain of weld specimen under small cyclic stress is larger than that of base metal. However,with the increase of plastic deformation,the higher content of alloying elements in weld metal has a more obvious strengthening effect,which makes the subsequent ratcheting strain of weld specimens with a certain number of cycles smaller than that of base metal under larger cyclic stress. The ratcheting strain of specimens with and without weld decreases with the increase of the pre-strain at cryogenic temperature. The accumulation of ratcheting strain can be completely restrained by pre-strain at a small cyclic stress level. S30408 is rate-dependent material at 110 K,and ratcheting strain decreases with the increase of loading rate.关键词：Ratcheting effect;Cryogenic;S30408;Experimental study
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发布时间：2022-09-22 - 摘要：In order to obtain the cold roll-beating spline surface roughness processing parameter domain suitable for different working conditions. Based on the principle of cold roll-beating spline forming,carry out cold roll-beating spline surface roughness test,using the test results to construct a surface prediction model for surface roughness response of cold roll-beating spline,using the analysis of variance,test sample test and comparison of experimental and predicted values,it is verified that the predictive model is feasible. Analyze the variation of the rotational speed of the rolling wheel,the feed rate of the workpiece and the surface roughness,the processing parameter domain of the surface roughness of the cold roll-beating spline is determined based on the surface roughness accuracy level comparison table. The results show: The rotational speed of the rolling wheel is 976 r/min ～ 2936 r/min,and the workpiece feed rate is in the range of 7 mm/min ～ 56 mm/min,with the gradual increase of the rotational speed of the rolling wheel and the feed rate of the workpiece,the surface roughness shows a trend of decreasing first and then increasing. Five sets of processing parameters were randomly extracted from the processing parameter fields corresponding to each accuracy level,and the maximum relative error between the surface roughness test value and the predicted value was 2. 75 %.Therefore,it is shown that the determined cold roll-beating spline surface roughness processing parameter domain is accurate and reliable. The research results have important application value and certain theoretical guiding significance for controlling the surface roughness of cold roll-beating spline.关键词：Spline of cold roll-beating;Surface roughness;Predictive model;Processing parameter field
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发布时间：2022-09-22 - 摘要：In this paper,the Stelllite6 corrosion-resistant coating was prepared on the surface of Q960 steel plate by laser cladding technology. To improve the wear resistance of the coating,the WC powder with mass fractions of 15%,20%,30%,35% and 40% was added to the coating,respectively. The coating’s microstructure and phase were analyzed by Metallographic microscopy and X-Ray Diffraction（ XRD）. The stellite6/WC coating’s microhardness and electrochemical property were tested by microvickers hardness tester and electrochemical workstation. The results show that,with the increase of WC content,the complex phase of cobalt carbon is formed in the composite coating,and a few pores and cracks appear. The wear resistance of the composite coating is improved obviously and the corrosion resistance of the composite coating is getting worse. Comprehensive analysis of corrosion resistance and wear resistance,the stellite6 coating with 30%WC has the best comprehensive performance.关键词：Laser cladding;Stellite6/WC;Wear resistance;Corrosion resistance
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发布时间：2022-09-22 - 摘要：Explosive welding technology is a high-energy processing technology,which has been widely used in industrial practice. The residual stress produced by explosive welding process has an important influence on the strength and stability of the structure. So it is necessary to study the reasonable range of residual stress and seek to predict,control and adjust the residual stress. In this paper,the hole-drilling method is used to test the residual stress of 316 L/SA516 explosive welding plate. The basic principle of hole-drilling method for measuring the residual stress,the preparation of the test and the matters needing attention in the test process are introduced. The residual stresses measured by hole-drilling method mainlyanalysis explosive residual stresses,normalized residual stresses and residual stresses in the direction of explosive thickness. The development rule of the measurement results is basically consistent with the actual situation.关键词：316L/SA516;Explosive welding plate;The hole-drilling method;Welding residual stress;Test
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发布时间：2022-09-22 - 摘要：The fatigue characteristic of TC4 titanium alloy by selective laser melting（ SLM） with two different surface roughness is investigated. The detail fatigue rating（ DFR） values are achieved based on the fatigue tests. The fatigue fractography is observed by scanning electron microscope to find the reason for surface roughness modification. The results indicate that DFR value of as-built surface specimen is 235. 1 MPa and machined surface specimen is 283. 3 MPa. So the SLM TC4 specimen in machined surface has superior fatigue property. The surface roughness has a significant effect on the crack initiation site. The fatigue crack in as-built specimen initiates from surface. Fatigue crack in machined specimen initiates from inside to subsurface.The latter is flat and the former is relatively rough.关键词：Selective laser melting;Surface roughness;Detail Fatigue Rating（DFR）;Fatigue fractography
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发布时间：2022-09-22 - 摘要：A method for calculating the tearing force of a new type of tearing device for aerostat was studied based on the theory of linear elastic fracture mechanics. Firstly,the critical strain energy release rates GICand GIIICof the film materials were obtained by fracture tests of type I and III. The FEA Models of the tears-I,tears-III and the tearing device were constructed by Debond and VCCT technology. The Power model was selected as the crack extension criterion,and the index in the Power model was fitted by the FEA results and test results of Type I and Type III tearing respectively. Finally,the tearing force of the tearing device was calculated based on the finite element model and the power model. The effectiveness of the results was verified by physical experiments,indicating that the calculation method of the tearing force for the new tearing device is feasible.关键词：Membrane tear;FEA;Fracture mechanics
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发布时间：2022-09-22 - 摘要：In order to improve the bearing capacity of ship-mounted universal coupling,a certain type of cross-shaft universal coupling fork was taken as the research object,and the analysis process of the fork was established by Abaqus. In comprehensive consideration of manufacture, structure and assembly of the original fork, the fork was simplified and a mathematical model of the fork was established. A new method based on particle swarm optimization algorithm was put forward for size optimization of the fork,then an Abaqus script written by Python was used to complete parametric modeling and analysis of the fork. Based on the optimization method,a new type of universal coupling fork was developed and the performance test was carried out. The results show that the method can improve bearing capacity of the fork effectively,providing an example for structural optimization or design of similar products.关键词：Universal coupling fork;ABAQUS;Parametric modeling;Particle swarm algorithm;Size optimization
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发布时间：2022-09-22 - 摘要：In order to design a horn for small hole extrusion machining with ultrasonic vibration,an optimization method of composite horn was proposed. Three surrogate models,Polynomial Response Surface,Kriging and Support Vector Regression,were employed to predict the performance parameters of the horn according to its dimension parameters. The accuracy of the surrogate models were compared. Based on genetic algorithm and the model with the higher accuracy,the optimization of the composite horn was investigated. The simulation results confirm the validity of the optimization method. The experimental results show that the horn meets the requirements of use and the machining effect is ideal.关键词：Small hole extrusion machining with ultrasonic vibration;Ultrasonic horn;Surrogate model;Genetic algorithm;Optimization method
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发布时间：2022-09-22 - 摘要：As the real load is very complicated during the process of harvester operation,it is of great significance for the prediction of fatigue life to describe the load characteristics and distribution form accurately. In order to obtain the probability density distribution model of the load cycles. Take RF-half shaft torque as the research object,the mixture Gaussian fitting method based on EM was suggested. n Code software was used for rain flow counting and the load cycle was described with the vector S.The cluster number and cluster center loading were got from the clustering of the loading cycle by the SPSS software,and using EM algorithm to resolve the mean and covariance matrix of Gaussian component. The index value of SSE and RSME are close to0,but R and Raare both up to 0. 85 based on the index model. It showed that the Gaussian mixture indeed fitting out of the original data of load-cycle. The results of research can provide a theory evidence for the fatigue life analysis and load spectrum extrapolation.关键词：Harvester;Mixture of Gaussian function;Parameter estimate;Rainflow method;Distribution estimation
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发布时间：2022-09-22 - 摘要：Based on univariate dimension reduction method（ UDRM）,edgeworth series and the relation of statistical moment,a method for calculation of failure probability of mechanical components is proposed. The univariate dimension reduction method is applied to calculate the response origin moments of fundamental input random variables. Edgeworth series is used to estimate failure probability of mechanical components by using first few response central moments. The non-normal random parameters need not to be transformed into equivalent normal ones. Two numerical examples are employed to illustrate the accuracy and efficiency of the proposed method and the second moment method by comparing the failure probability results.The results obtained by the proposed new method and the second moment method are compared with those obtained by Monte-Carlo Simulation（ MCS） respectively. The results show that the new method can calculate the failure probability of mechanical components effectively.关键词：Univariate dimension-reduction integration;Failure probability;Edgeworth series;Origin moment;Center moment
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发布时间：2022-09-22 - 摘要：Taking the gear transmission mechanism of a five-gear transmission as the research object,the simulation model of the gear transmission mechanism of the transmission is established by using Romax Designer software,and the load-bearing situation,transmission error and load distribution on the tooth surface of the 4 th gear are simulated and analyzed. According to the theory of tooth lead modification and tooth profile modification,the variable range of three-dimensional modification parameters of the 4 th gear is analyzed by orthogonal experiment principle. Then the genetic algorithm is used to optimize the modification parameters of gear,and the optimal combination of modification parameters is obtained. The validity of this method is verified by vehicle test. By comparing the results before and after optimization,it can be seen that the three-dimensional gear modification technology can greatly reduce the stress of the gear,reduce the fluctuation amplitude of the transmission error of the gear,optimize the stress distribution of the gear tooth surface,and reduce the vibration noise. At the same time,it can be proved that this method can effectively improve the meshing condition of gears and is an effective means to optimize the meshing performance of gears.关键词：Transmission;Gear modification;Transmission error;Genetic algorithm;Performance optimization
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发布时间：2022-09-22 - 摘要：Hertz contact is a ideal contact status which supposes the contact surfaces as not moving,completely smooth and no lubricant,but real surfaces of meshing gears are rude,exiting relative motion and lubricating,and which is a kind of nonHertz contact. Based on EHL theory,this paper proposes a new gear design theory and method,called gear design theory and method of non-Hertz contact. The new theory and method comprehensive considers every factors of influencing strength and lubrication of gears,and which can ensure the designed gears meet the dual requirements of strength and elastic hydrodynamic lubrication. Specific formulas of are given out and a large number of engineering examples are used to verify the new theory and method proposed in the paper,and the results show that the conformity of new design theory and method and the actual engineering examples are very well,and which can directly apply to practical engineering design to meet the requirement of engineering design. In particular,to design of high speed and heavy duty gear transmission,the new theory and method of this paper has important theoretical significance and practical value.关键词：Non-Hertz contact;Gears;Contact strength;EHL;Design theory and method
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发布时间：2022-09-22 - 摘要：Liquid Impact Forming（ LIF） of bimetallic thin-walled tubes is a composite forming technology developed on the basis of tube hydroforming and stamping. Internal pressure required for the formation of the bimetallic thin-walled tubes under liquid impact loading is derived from the compression of the volume of the tube blank,and its size varied with the compression of liquid volume. For this purpose,investigation on forming mechanism and variation law of the internal pressure of the bimetallic thin-walled tubes is proposed.Firstly,forming principle of LIF of bimetallic thin-walled tubes was introduced. Secondly,theory of internal pressure was analyzed in the process of the axial impact hydraulic performing and the radial forming of bimetallic thinwalled tubes. Mathematical model between the internal pressure and volume change in the tube blank cavity was obtained.Thirdly,generation regularity of internal pressure of the axial and the radial liquid impact of the bimetallic thin-walled tubes was performed using ANSYS WORKBENCH. Through comparison of numerical simulation and theoretical analysis,it is not difficult to find that they were a good consistency,and the internal pressure model is optimized by the model error revision,which lays a good theoretical and application basis for further research on LIF of bimetallic thin-walled tubes.关键词：Bimetallic thin-walled tubes;Liquid impact forming;Tube hydroforming;Internal pressure;Finite element simulation
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发布时间：2022-09-22 - 摘要：The bolt is the main connecting part of the RV reducer. Its mechanical properties affect the transmission accuracy of the whole machine. According to the principle of generating the profile of the cycloidal gear. Combining vector method to establish the profile equation of cycloidal wheel after shaping. Apply the principle of deformation coordination. Mechanical analysis of each component of the whole machine. Calculate the force of the bolt in theory; Considering the modification of the cycloidal wheel and the diameter error of the center circle of the pin tooth. Multi-body dynamics analysis in ADAMS. Through simulation analysis,we can know: Different initial mounting angles or different angles of rotation. Different bolts have different trends and different degrees of change. Different angles of rotation. Bolt force is not in the same order. As the angle of rotation of the cycloid increases,the overall force of the bolt increases first and then decreases. As the load increases,the bolt is gradually increased in force. As the load increases,the magnitude of the increase also increases.关键词：Bolt;Vector method;Deformation coordination principle;ADAMS;Force characteristics
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发布时间：2022-09-22 - 摘要：In order to study the difference of vibration response of TBM driving system under uncertain geology and how to select reasonable driving forms according to different geological conditions,a dynamic analysis method of TBM driving system in uncertain geology is proposed. Firstly,a geological equivalent model and typical working condition model are established,and a multi-degree-of-freedom coupled dynamic model of TBM driving system is established by the lumped mass method. Then,according to different geological conditions and combined with interval theory,the interval loads of each working conditions corresponding to geological conditions are obtained,and the interval loads are substituted into the dynamic model to obtain the dynamic response of various driving modes under uncertain geology and working conditions. Finally,by comparing the dynamic response intervals of different driving modes under maximum thrust conditions,the results are as follows:（ 1） When the geology of TBM tunneling is complex rock strata,the driving form of symmetrical distribution is relatively stable.（ 2） When the geology is homogeneous strata,the uniform distribution is stable.（ 3） With the increase of the number of hard rock in geology,the influence of the layout of driving system on vibration is gradually increasing.关键词：Driving system of TBM;Uncertain geology;Lumped mass method;Dynamic model;Interval load;Dynamic Analysis
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发布时间：2022-09-22 - 摘要：Finite element analyses on thermal deformation process of polyvinyl chloride insulation of cable were carried out by using quasi-static analysis based on ABAQUS/Explicit. The finite element results were verified by the experimental results,indicating an adequate solution of thermal deformation behavior. Meanwhile,thermal deformation behaviors for various structural parameters were studied. The fitting functions of the indentation percentage and structural parameters of insulation were obtained,as well as that of the structural parameters and cross-sectional areas for a given indentation percentage level.The work can provide some references for characteristic prediction and insulation thickness design of wire and cable products.关键词：Polyvinyl chloride cable;Insulation;Thermal deformation;Finite element analysis
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发布时间：2022-09-22 - 摘要：A thermo-magneto-elastic problem for a current-carrying shell with clamped perimeters in a magnetic field was studied. Based on the kinetic equations, geometric equations, physical equations, and electrodynamics equations, the fundamental equations of a current-carrying shell under the interaction of a mechanical field,an electromagnetic field,and a temperature field were given. The nonlinear partial differential equations including 10 basic unknown variables were established.Using Newmark’s stable finite equidifferent formulas,normal type which can be solved by the discrete-orthogonalization method was obtained. For the shell with clamped perimeters,the expressions for the Lorentz force,the temperature field,and the integral eigenvalues of the temperature field were derived. The change rules of stresses,temperatures,and deformations in the currentcarrying shell with the electromagnetic parameters were analyzed. It is proved that the stresses,strains,and temperatures in plates and shells can be controlled by changing the electromagnetic and mechanical parameters through the example calculation. This provides a method of theoretical analysis and numerical calculation for changing the service conditions and intensity researches of plate and shell structures in an electromagnetic field.关键词：Shell with clamped perimeters;Thermo-magneto-elasticity;Displacement;Stress;Discrete-orthogonalization method
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发布时间：2022-09-22 - 摘要：A three-dimensional thermal-mechanical coupling finite element model of disc brake is established,and the thermal-mechanical coupling characteristics and friction-induced vibration characteristics in two modes: drag braking and startstop braking is studied,in addition,the influence of different deceleration behaviors on thermal-mechanical coupling and vibration characteristics in start-stop braking mode is discussed. Results show that: under the effect of thermal-mechanical coupling,the thermal deformation forms of the brake pad on both sides of the disc are completely different,resulting in significant differences in the temperature distribution of the friction discs on both sides. As the temperature increases,the vibration intensity of the brake system gradually decreases. Due to the difference in temperature leads to the difference in thermal deformation level on both sides of the brake disc. Therefore,the vibration intensity of the brake piston side is greater than that of the finger side.The deceleration behavior of the brake disc has a significant influence on the thermal-mechanical coupling characteristics and friction-induced vibration characteristics of the system. In the fast braking mode,the heat exchange between the brake and the outside environment is significant,the interface temperature is low but the vibration intensity is large. In the slow braking and step braking modes,the interface temperature increases rapidly,but the vibration intensity of the system is low due to the slow friction process. Especially in the case of step-by-step braking,the vibration intensity at a certain stage may be very weak. These results have certain guiding significance for understanding the temperature distribution characteristics of brake system and improving the brake vibration noise.关键词：Disc brake system;Thermal-mechanical coupling;Friction-induced vibration;Brake;Simulation analysis
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发布时间：2022-09-22 - 摘要：In the process of underbalance drilling,the rubber core of rotating control head is subject to the alternating cycle load,which is prone to fatigue failure.Firstly,the sealing principle of rotating control head is analyzed and the stress of rubber core in dynamic sealing process is obtained.Then,the Yeoh constitutive model in the deformation process was established by the tensile test of the rubber core material. Then ABAQUS software was used to establish the finite element model of the dynamic sealing of the rubber core,and the simulation of the sealing process of the rubber core during the drilling and the optimization analysis of the factors affecting the fatigue life of the sealing surface of the rubber core were carried out.In this paper,the inner diameter of rubber core is optimized,and the inner diameter size of rubber core should be matched with different outer diameter drill pipes is optimized.The paper also optimizes the lowering and lifting speed of drill pipe under different wellhead pressures.The higher the well pressure,the more likely the rubber core fatigue failure will be. The safe lowering and lifting speed of drill pipe under different pressures is obtained.At last,according to the Chinese standard,indoor seal test and field application test were carried out in the well control equipment quality supervision and inspection center of China national petroleum industry to confirm the reliability of finite element optimization,which is of great practical significance to improve the service life of rubber core and oilfield operation safety.关键词：Underbalanced drilling;Rotating blowout preventer（RBOP）;Finite element simulation;Experiment and field application
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发布时间：2022-09-22 - 摘要：The effect of multilayer interphase on the transverse cracking behavior of ceramic matrix composites（ CMCs） was simulated by micromechanical finite element method. The sub-layers of interphase were created according to their real thickness within a RVE model to describe the microstructure of multilayer interphase of CMCs. The finite element method was applied to analysis the stress by defining different material properties for the interphase sub-layers. On this basis,the cracking and debonding were simulated by extended finite element method and cohesive interfacial model,respectively.. After all,a simulation method for transverse cracking in the multilayer interphase was developed. The simulation results for cracking path within monolayer BN interphase,and multilayer interphase of different structure（ BN/Si C/BN and BN/Si C/BN/Si C/BN） were compared. It can be seen that the interfacial debonding occurs at the interface between fiber and interphase for CMCs with multilayer interphase. Moreover,the transverse cracking strain of multilayer interphase is higher than that of monolayer interphase and the location of cracks for the two cases is very different.关键词：Ceramic matrix composites;Multilayer interphase;Extended finite element method;Cohesive model
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发布时间：2022-09-22 -
ANALYSIS ON LIMIT LOAD AND J-INTEGRAL FOR EMBEDDED AND PROPAGATED CRACK PLATES UNDER BIAXIAL LOADING
摘要：Ligament rupture occurs for embedded crack plate under biaxial loading. Then,embedded crack will propagate as surface crack,through-thickness cracks or extended surface cracks. The mechanical strength of components with different types of cracks under biaxial loading has become the focus of research. As a typical biaxial loading condition,an end tensile/compressive force applied at the centroids of the end sections of the plate perpendicular to the crack plane,a tensile/compressive stress parallel to the crack plane and a cross-thickness bending moment applied at the end sections of the plate,has been considered. Taking a plate with embedded elliptical crack is as the research object,comparison results of limit load and J-integral solutions for embedded elliptical crack,propagated surface half-elliptical crack,propagated through-thickness cracks or extended surface cracks have been given,provided basis for users to use defective components reasonably.关键词：Embedded cracks;Biaxial loading;Limit load;J-integral;Reference stress method- 3
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发布时间：2022-09-22 - 摘要：In engineering,cracks are usually regarded as semi-elliptical surface cracks. It is not easy to establish a complete finite element model of a semi-elliptical surface crack,thus a quarter of the crack model is generally used to calculate the stress intensity factor by finite element method. This paper adopts APDL and UIDL technologies for secondary development of ANSYS software,establishes a complete model of semi-elliptical surface crack by simple interface operation with the method of model block processing. Using this method,the stress intensity factors of the central semi-elliptical crack and the oblique semielliptical crack were solved respectively. The results are basically consistent with the theoretical solution and the results in the literature,which shows that it is accurate and reliable to use the complete crack model established by this method to calculate the stress intensity factor. The combined development modeling function can be used to solve the stress intensity factors in complex structures under complex loads,and has important value for practical application of engineering.关键词：Semi-elliptical surface crack;Stress intensity factor;ANSYS secondary development;Complete crack model
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发布时间：2022-09-22 - 摘要：With the development of offshore wind farms,the probability of collision between offshore wind turbines and ship will gradually increase. Studying the anti-collision performance of offshore wind turbines has important application background and value. Piles-soils coupling as a condition,contrast the rubber、aluminum foam crashworthy device,and explict dynamics software LS-DYNA is used to simulate the process of marine wind turbines being hit by ships. Compared with foam aluminum guards,rubber guards and unprotected wind turbines,the wind turbine is subjected to the dynamic response of the ship collision process.The results show that With the increase of the speed of the ship,the maximum contact force of the rubber material increases,while the foam aluminum material increases first and then decreases,and its energy absorption characteristics are enhanced after the 6 m/s; with the comparison of the protective device aluminum foam、rubber and non-protective device,the aluminum foam material has the best inhibition to the structure response; the more dense the plastic strain contour line,the larger the plastic deformation,and the plastic deformation is easy to occur when the oblique support is connected with the column.关键词：Offshore wind turbine;Collision;Aluminum foam;Crashworthy device;Dynamic response
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发布时间：2022-09-22 - 摘要：The contact fatigue damage of the roll body caused by cyclic contact stress between rolls in four high mill will not only influence the wear of it,but also subsequent grinding and using life. It is of great significance to analyze the distribution of contact stress between rolls under different rolling process parameters for analyzing the damage of rolls and roll maintenance. The finite element method was used to study on the influence of different process parameters on the contact stress distribution and stress distribution uniformity of rolls used in a four high PC mill of 1880 rolling line.The fatigue damage distribution in the axial section of roll body was theoretically calculated by model established based on the damage accumulation theory. The tested fatigue hardening distribution was used to comparing with the theoretical distribution and it is revealed that the theoretical results have some rationality.关键词：Four high mill;Contact stress;Fatigue damage;Hardening
- 5
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- 177
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- 1
发布时间：2022-09-22 - 摘要：Elastic cushion plays an important role in alleviating the dynamic interaction between train and its running foundation. The ratio of static stiffness to dynamic stiffness is the key parameter to determine the alleviation performance of elastic cushion. Aiming at a new type of honeycomb mesh-type elastic cushion plate structure,a three-dimensional finite element model was established,and the mechanical properties of rubber material were simulated by super-elastic and viscoelastic constitutive models. Under the condition that the material parameters of elastic cushion plate were unchanged,the effects of the change of key parameters such as mesh thickness and aperture on the dynamic and static stiffness of mesh-type elastic cushion plate were studied,and the traditional groove elastic cushion plate was compared. The results show that: under the condition of constant mesh aperture,with the increase of mesh wall thickness,the static stiffness of elastic cushion plate increases and the ratio of dynamic stiffness to static stiffness decreases; under the condition of constant mesh wall thickness,with the increase of mesh aperture,the static stiffness of elastic cushion plate decreases and the ratio of dynamic stiffness to static stiffness increases;compare with the traditional grooved elastic cushion plate with similar static stiffness,the meshed elastic cushion plate has the characteristics of lower dynamic and static stiffness,smaller maximum stress value and more uniform stress distribution.Therefore,reasonable adjustment of mesh wall thickness and aperture size can make mesh elastic cushion plate suitable for track structures with different stiffness requirements,and the application of mesh structure to under rail elastic cushion plate can enhance the force transmission characteristics of cushion plate and prolong the service life of cushion plate.关键词：Urban rail traffic;Under rail elastic cushion plate;Finite element simulation;Static stiffness;Stiffness ratio
- 3
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- 175
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- 3
发布时间：2022-09-22 - 摘要：Historically,there have been many restorations and explorations of the structure of the Houfeng seismograph,but there are unreasonable points. This has caused the public and some scholars to question its authenticity,so a reasonable principle model needs to be proposed. We found a stable inverted pendulum structure that does not require the use of springs. It have a low natural frequency while ensuring the size and manufacturing process in line with historical facts,and can be used to develop the Houfeng seismograph that meets the requirements of the later Han. And we simulated the structure in matlab. The result proves that the structure can respond to the seismic wave and issue a warning. It is a reasonable model of the Houfeng seismograph.关键词：Houfeng seismograph;Inverted pendulum structure;Low natural frequency;Seismic wave;Vibration simulation
- 3
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- 133
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- 2
发布时间：2022-09-22 - 摘要：A new type of upper extremity exoskeleton rehabilitation robot is designed,which have 5-degree of freedom.Firstly,the mechanical structure of the robot is analyzed. D-H coordinates of the robot are established based on D-H parameter method.According to its coordinates,its kinematics equation is obtained. In order to make the rehabilitation training in patients with comfort and stability,point out a linear interpolation function of quartic polynomial that based on the same time interpolation points,the purpose is to plan the trajectory of the upper limb exoskeleton rehabilitation robot. Finally,trajectory planning of multiple joints and drawing images are carried out.In ADAMS,the upper extremity exoskeleton rehabilitation robot based on 1: 1 model is simulated to verify the correctness of the function.By Analysing of trajectory planning parameters for single and multiple joints,then the results are compared with the simulation data in ADAMS to prove the feasibility and stability of this method,which can be used in the trajectory planning of rehabilitation robot.关键词：D-H parameter method;Kinematics equation;Quartic polynomial;Linear interpolation;Adams Simulation
- 4
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- 307
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- 2
发布时间：2022-09-22 - 摘要：The composite materials component with embedded cable three point bending stress finite element analysis model was established,and the influence of cable embedding position,resin enrichment zone length and cable diameter on the bending stress of the component was analyzed under the three point bending load to the same bending load. The results show that the closer the cable is embedded in the composite surface,the greater the bending stress of the component. With the length of the resin enrichment zone increase,the bending stress of the component increases. With the diameter of the cable increase,the bending stress of the component increases. With 90% confidence,the cable embedding position has a significant influence on the maximum bending stress,the resin length and cable diameter have no significant effect on the maximum bending stress of the component. The cable embedding position,cable diameter,resin length affect the maximum bending stress of the component in a descending order. The research conclusion provides a theoretical basis for the cable embedded composite technology.关键词：Composite materials component;Bending stress;Three point bending load;Finite element analysis
- 4
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- 187
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发布时间：2022-09-22 - 摘要：Based on random vibration theory and fatigue analysis method in frequency domain,with finite element software to construct the battery pack failure model of random vibration fatigue analysis and to calculate the fatigue life of the structure,the analysis results are in good agreement with the test results. Analyze the failure mechanism of the structure and carry out structural design improvement,the simulation and test results show that the fatigue life of the improvement scheme is significantly improved,and it has better anti vibration durability.关键词：Battery pack;Random vibration;PSD spectrum;Fatigue life;Design improvement
- 7
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- 638
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- 6
发布时间：2022-09-22
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