最新刊期
卷 46 ， 期 6 ， 2024
- 摘要：A method for the calculation of structural external excitation and the reconstruction of structural response based on improved strong tracking Kalman filter was proposed.Firstly,the external excitation of the structure was derived by using the state-space model,and the external excitation and structural modal coordinates were combined to form a new state vector and an augmented rank state-space model was constructed.Secondly,an improvement based on the traditional strong tracking Kalman filter algorithm was carried out,which can deal with colored noise.Finally,the acceleration responses of some measuring points in the structure were used to calculate the external excitation of the structure and reconstruct the velocity and acceleration responses of the unmeasured points,the numerical simulation and experimental analysis of the two-dimensional truss and extended beam were respectively carried out to verify the proposed method.The results show that the proposed method can effectively reconstruct the structural external excitations,the velocity and acceleration responses of the unmeasured points,and its response time-history curve is in good agreement with the calculated response time-history curve or the measured response time-history curve.关键词：Structural response reconstruction;State-space model;Excitation calculation;Improved strong tracking Kalman filter algorithm;Colored noise13|0|1更新时间：2025-04-28
- 摘要：Aiming at the vibration signal of rolling bearing with problems of nonlinear,small sample size and traditional machine learning based diagnosis algorithm required expert experience,a convolutional deep forest(CDF)based rolling bearing fault diagnosis algorithm was proposed.Firstly,the one-dimensional vibration signal was preprocessed through normalization and transformation into image.Then the convolution neural network was exploited to train the image to complete the end-to-end feature extraction,and the cascade forest was used to analyze and classify the features.Finally,the effectiveness of CDF was verified on the bearing data set.The experimental results show that CDF can achieve high accuracy for small or big sample data under four loads.In addition,the accuracy of convolution neural network and CDF based on two-dimensional image are higher than one-dimensional,which proves the effectiveness of data preprocessing operation based on signal to image.关键词：Fault diagnosis;Rolling bearing;Deep forest;Convolutional neural network10|0|0更新时间：2025-04-28
- 摘要：In recent years,ultrasonic guided wave technology has been widely used in nondestructive detection of long distance pipelines due to its advantages of short detection time and wide detection range.In order to further improve the recognition accuracy,a new detection method that combines the theory of cross correlation and wavelet transform with Duffing oscillator system was proposed.The collected signal was pretreated by cross-correlation and wavelet transform,and then input into Duffing system for detection.The results of numerical simulation show that the hybrid measurement method based on the combination of traditional method and Duffing oscillator,can reduce the detection signal-to-noise ratio to-38.4 dB,which is lower than the detection result when Duffing vibrator is used alone-23.9 dB,greatly improving the defect detection accuracy and sensitivity.The research results are of great significance for extending the detection range of an ultrasonic guided wave and improving the detection sensitivity of small defects in practical engineering.关键词：Nondestructive detection;Pipeline;Ultrasonic guided wave;Duffing oscillator9|0|0更新时间：2025-04-28
- 摘要：Aiming at the new challenges in efficiency and reliability in the field of fault diagnosis in recent years,a coarsefine fault diagnosis method for induction motors based on the symmetrized dot pattern(SDP)was proposed.In this method,firstly,the vibration signals of each faulty motor were converted into snowflake images by SDP method,and then a two-stage fault diagnosis framework of coarse-fine classification was designed for image feature extraction and classification.In the coarse classification stage,the color histogram features and the support vector machine(SVM)were used to diagnose the samples,and a threshold was selected to determine the samples for the coarse classification.In the fine classification stage,Gist features that can extract image details and SVM were used to diagnose the remaining samples.Experimental results show that the proposed method combines the advantages of color histogram features and Gist features,can achieve the most reliable diagnosis with relatively high efficiency,and has certain anti-noise ability.关键词：Symmetrized dot pattern;Visual characteristics;Support vector machine;Two-stage fault diagnosis7|0|0更新时间：2025-04-28
- 摘要：The vibration response simulated by the dynamic model of a bearing with spall failure mainly depends on the energy change of the rolling element as it passes through the defective area.In order to establish a dynamic model based on the energy fluctuation of the rolling body when it passes through the defective area,the motion track of the rolling body peeling fault at different slopes was deduced according to the geometric relation.Based on the Hertz contact theory and the law of conservation of energy,the corresponding time-varying energy formula was constructed.The dynamic model was introduced for simulation,and the relation between the energy change and the vibration response of the rolling body when it passed was quantified.The simula⁃tion and experimental results are in good agreement,which proves the relation between the vibration response of the bearing with spall failure and the energy fluctuation of the rolling element.The established dynamic model can effectively predict the vibration signal of the bearing with spall failure.关键词：Rolling bearing;Spall defect;Dynamic modeling;Conservation of energy10|0|0更新时间：2025-04-28
- 摘要：The existing miniaturized vehicle intelligent fragrance devices in China generally have problems such as small air volume and high noise,resulting in poor user experience.In view of the above problems,firstly,a miniaturized vehicle intelligent fragrance device based on Catia software was designed.Secondly,based on the computational fluid dynamics(CFD)method,the flow field simulation analysis of the vehicle intelligent fragrance device was carried out,and the air volume was optimized by improving the air path and the size of the air outlet.The optimized air volume is 1.2 m3/h,which is 16.7% higher than that before optimization,which verifies the feasibility of the optimization method.Finally,based on Siemens Simcenter Testlab system,the noise reduction of the vehicle intelligent fragrance devices was studied.The scheme of isolating vibration source and adjusting motor subdivision was proposed to reduce noise.The experimental results show that the noise of the whole machine is reduced by 5.61 dB(A),which verifies the effectiveness of the noise reduction method.The structural design method,air volume optimization method and noise reduction technology scheme provide a strong reference for product development in the field of vehicle electronics.关键词：Vehicle intelligent fragrance;Computational fluid dynamics;Flow field simulation;Structural design;Noise reduction technology scheme13|0|0更新时间：2025-04-28
- 摘要：Taking the middle ear system as the research object,the nonlinear vibration characteristics of the human ear under narrow-band random acoustic excitation were studied.According to the three-degree-of-freedom nonlinear model of the middle ear,the nonlinear random vibration equation was established and the regular matrix was introduced to obtain the nonlinear vibration equation in the regular coordinate.The amplitude-frequency characteristic equation of the first-order primary resonance of the middle ear system was obtained by the multi-scale method.Through the bifurcation diagram and the maximum Lyapunov index,it was found that the middle ear system produces different motions under different excitations.The Ito stochastic dif⁃ferential equation of the middle ear system was derived,the approximate expression of the second-order moment of the system was obtained by using the rectangular method,and the influence of the random disturbance intensity on the middle ear system was verified.The results show that the resonance area of the system increases with the increase of the external excitation.When the random disturbance intensity increases,the thickness of the limit cycle of the phase diagram becomes thicker.关键词：Middle ear system;Nonlinear;Primary resonance;Bifurcation;Narrow-band excitation7|0|0更新时间：2025-04-28
Vibration · Noise · Monitoring · Diagnosis
- 摘要：Focus on the influence of high-temperature and thermal exposure on the strength of the aluminum alloy riveted structure commonly used in aircraft,finite element analysis(FEA)and test research are carried out with joints composed of 2024-T3 sheets and NAS1097KE5 rivets in room temperature,high temperature and thermal exposure.The detail FEA which consider of material nonlinearity and properties attention after high temperature and thermal exposure,results in a good agreement with tests,which the differences are less than 5%.The formed finite element method(FEM)can accurately simulate the strength performance of this type of aluminum alloy riveted structure in the environments of room temperature,high-temperature and thermal exposure.The differences of joint strength after thermal exposure between test results and formulas prediction fitting from FEA analysis are less than 4%.After conservative revision,the formulas can be applied to engineering practice.The established joint strength calculation method of aluminum alloy riveted structure under high-temperature and thermal exposure can be extended to other similar structures.关键词：Aluminum alloy;Rivet;High temperature;Thermal exposure;Strength;Test;Finite element analysis0|0|0更新时间：2025-04-28
- 摘要：Due to the simple construction,fillet welds are often widely used in the connection of metal components.However,the non-self-balancing welding residual stress in the fillet weld is obvious,and the existing evaluation codes and standards still lack a clear stress checking method.In the assessment codes such as Code for design of steel structures,the influence of bending moment load and welding residual stress of fillet weld isn't considered in the given strength calculation criterion,which limits the application range of related methods.Based on the experimental test and theoretical research on the strength of fillet weld joints,a method of strength evaluation based on the flow stress of weld material was proposed.The strength experiment results of fillet weld connectors show that the weld strength corresponding to the maximum tensile load is very close to the mean value of the difference between the tensile and yield strength of the experimental test.It can be considered that the welding residual stress in the fillet weld is close to the yield stress,and the failure occurs when the stress in the fillet weld increases to the tensile strength during the loading process.Under pure shear condition,the maximum load of fillet weld connector is close to the value under tensile load.Under the condition of considering the welding residual stress of fillet weld material,the material evaluation coefficient of fillet weld evaluation criterion based on flow stress is set to be 0.8,and the evaluation criterion of fillet weld connector under tensile and bending moment load is also indirect given.关键词：Fillet weld;Strength analysis;Flow stress;Experimental research7|0|0更新时间：2025-04-28
- 摘要：The front anti-collision beam system is an important component to improve the safety of the whole vehicle.Among them,the structural parameters of the energy-absorbing box and the beam directly affect the crash resistance of the vehicle body.In order to obtain the optimization scheme of the energy-absorbing box-type front anti-collision beam system,firstly,from the three perspectives of crushing form,initial peak force and specific energy absorption,the impact of the cross-section structure of the energy-absorbing box on the crash-worthiness performance was studied.Then,the impact of the cross-section structure of the beam on the crash-worthiness performance was studied from the two dimensions of bending strength and energy absorption value.Finally,the crash-worthiness performance of the optimized energy-absorbing box-type front anti-collision beam system in the case of frontal collision and partial collision was studied.The results show that,the regular hexagonal section has a good energy absorption effect;the tripple channel beam has high flexural strength and good energy absorption effect;the new energy-absorbing box-type front anti-collision beam system compared to traditional systems,in the case of frontal collision and partial collision,the energy absorption values increase respectively by 11.5% and 31.6%,and the intrusion amount decreases respectively by 53.2% and 16.1%.The support for the research on the safety performance of the optimized anti-collision beam system is provided.关键词：Automotive engineering;Anti-collision beam;Energy-absorbing box;Collision safety8|0|0更新时间：2025-04-28
- 摘要：The semi-reentrant honeycomb structure has the characteristics of zero Poisson's ratio,and is a hybrid form composed of hexagonal honeycomb structure and reentrant honeycomb structure.Therefore,the deformation characteristics of a semi-reentrant honeycomb cell can be obtained through deformation coupling of a hexagonal honeycomb cell(with a positive angle)and a reentrant honeycomb cell(with a negative angle).Based on the different mechanisms of bending,tensile,hinge,and shear deformation of hexagonal honeycomb cells and reentrant honeycomb cells,and considering the influence of the cell wall thickness,a deformation mechanism of semi-reentrant honeycomb cells was established.An equivalent theory of mechanical properties of in-plane deformation was derived to predict its elastic modulus and Poisson's ratio in different directions in the plane.The effects of geometric parameters(tilt arm length l,vertical arm length h,angle α,angle β,structure thickness d and unit wall thickness t)on in-plane tensile properties(elastic modulus and Poisson's ratio)of semi-reentrant honeycomb structure were analyzed using the finite element method.By comparing the finite element simulation results with the prediction results of the equivalent theory,the effectiveness and accuracy of the equivalent theoretical model were verified.Comparing the prediction results of different equivalent theories shows the importance of considering the effects of different deformation mechanisms and wall thickness to accurately predict in-plane tensile properties.关键词：Semi-reentrant honeycomb structure;Equivalent theory;Finite element method;Elastic modulus;Poisson's ratio;Tension properties7|0|0更新时间：2025-04-28
- 摘要：Mining scraper conveyors operate in complex environments for a long time,and the sprocket will suffer different degrees of wear,which will have a great impact on the dynamic performance of the scraper conveyor.Ttaking the ring chain transmission system of the SGZ 1000/3*1000 mining scraper conveyor as the research object,and firstly the wear sprocket model was established.Then the dynamic simulation of sprocket drive process under different wear degree was carried out to analyze the influence of sprocket wear on the dynamic characteristics of the system,and it was verified by experiments.The results show that,compared with no wear,sprocket wear intensifies the speed fluctuation of the chain during operation,and increases up to 3 times.The meshing contact force between the sprocket and the chain ring is increased to 3 times the original;The connecting force between the links increases to twice the original,while the connecting force fluctuation increases up to four times the original.This study provides a theoretical reference for the design of the drive system of the scraper conveyor.关键词：Scraper conveyor;Wear sprocket model;Ring chain drive system;Dynamic characteristic6|0|0更新时间：2025-04-28
Experimental Research · Testing Technology
- 摘要：The reliability of mechanical structures is crucial for their safe operation,to address the problem of low accuracy and low efficiency in reliability analysis of complex mechanical structures,a new active learning surrogate model based reliability analysis method was proposed.The spatial location characteristics of excellent fitting samples were studied and three constraints,such as surface constraint,distance constraint,and domain constraint,were proposed accordingly.Correspondingly,three control functions were established to achieve the three constraints.Then,three control functions were organically collaborated,and an effective new learning function,collaboration-mean point constrained learning(CPCL)function was proposed.Combined with the augmented radial basis function(ARBF),a collaboration-mean point constrained active learning surrogate model(ARBF+CPCL)reliability analysis method was established.Finally,three cases were employed to verify the high computational accuracy and computational efficiency of ARBF+CPCL reliability analysis method,and the application ability of ARBF+CPCL method in practical engineering cases was proved through the reliability analysis example of the turbine disk.关键词：Mechanical structure;Reliability analysis;Active learning;Turbine disk;Fitting sample8|0|0更新时间：2025-04-28
- 摘要：In order to solve the reliability evaluation under the competitive failure of multiple performance aero-engines,multiple performance data was fused into an overall degradation data by the matrix similarity,and a nonlinear Gamma process with random effects was used to fit the overall degradation data to obtain the reliability function under multivariate degradation.Assume that multiple performance of the aero-engines have sudden failures,the optimal sudden failure distribution was selected by Anderson-Darling(AD)distribution test,the reliability function under sudden failures was obtained by the mixed distribution.Assume that degradation failure and sudden failure were independent,the reliability evaluation of the multiple performance aeroengines under competitive failure was realized.Finally,the effectiveness and accuracy of the model were verified by the case analysis.关键词：Competitive failure;Matrix similarity;Gamma process;Mixed distribution6|0|0更新时间：2025-04-28
- 摘要：The reliability of engine and chassis system is the key factor affecting the performance of commercial vehicles.Accurate and comprehensive evaluation of its reliability is of great significance to guide the improvement of commercial vehicle reliability.Based on big data of faults,a reliability evaluation was conducted for the engine and chassis of four commercial vehicles within a specific manufacturing enterprise.All the fault data of the four commercial vehicles in 2021 were collected for preliminary statistical analysis,and a random sample was drawn to form an analysis sample.Based on the U-test to test the difference between the sample and the overall data distribution,the probability density distribution function of the engine and chassis system fault interval was fitted,and it was inferred that the distribution law satisfied the Weibull distribution.The traditional median rank method and kernel density estimation method were used to mutually verify and calculate the distribution parameters of the system.The Kolmogorov-Smirnov(K-S)hypothesis test was used to verify that the sample data of the fault interval time followed the Weibull distribution.The reliability evaluation indexes such as reliability,failure rate and mean time between failures were calculated.After 500 days of driving,the reliability of the four commercial vehicles were 0.002,0.003,0.007 and 3×10-9.The fault rates were 0.021,0.016,0.015 and 0.063.The average time between fault were 146.088,129.492,149.755 and 70.897 days.Based on the reliability evaluation results and fault contents of engine and chassis system,the optimization scheme was proposed to provide reference for the reliability improvement of the commercial vehicle system.关键词：Reliability evaluation;U-test;Median rank;Kernel density estimation;Weibull distribution;K-S hypothesis test7|0|0更新时间：2025-04-28
- 摘要：U-shaped containment ring is usually used as protection device for turbine starters.Under the condition that the turbine rotor is contained,structural optimization of the U-shaped section containment ring was carried out to obtain a light and inclusive structure,which improved aircraft safety and thrust-to-weight ratio.An optimal design method for U-shaped cross section containment ring was proposed.The method adopted the optimal Latin hypercube design,numerical simulation,response surface modeling,and multi-island genetic algorithm to achieve the optimal design of multiple parameters of containment rings cross section.By combining simulation and experiment,the influence weights of different structural parameters on the residual kinetic energy of debris and the volume of containment rings were analyzed.The influence of different structural parameters of Ushaped containment ring on the containment results was studied.Containment test was carried out to verify the optimized containment ring.The results show that the thickness of the containment ring has the greatest influence on the residual kinetic energy of the debris,and the weight ratio is 38%.The main structural parameters affect the inclusion effect are thickness and groove depth.The error of inclusion ring deformation is less than 2%in the comparison between simulation and test results,which indicates that the optimization design method proposed is reasonable and reliable.The research results can provide prior knowledge and optimization methods for the quality reduction of U-shaped containment ring structures.关键词：Air turbine starter;U-shaped section containment ring;Structural optimization design;DOE sample library;Response surface modeling;Multi-island genetic algorithm7|0|0更新时间：2025-04-28
- 摘要：In order to optimize the titanium alloy workpiece surface finish and reduce the deterioration effect of surface residual stress caused by temperature gradient during grinding,a optimization of grinding process based on electromagnetic induction preheating was proposed.Firstly,the corresponding grinding process was modeled by 3D finite element method,and the grinding process under different grinding parameters and conditions were simulated and analyzed.Secondly,the results under different grinding parameters and conditions were analyzed to determine the influence mechanism of different parameters and conditions on grinding results.Finally,a set of simulation parameters were selected for corresponding experimental analysis and compared with the simulation results.The results show that the grinding process based on electromagnetic induction preheating can optimize the distribution of residual stress on the workpiece surface to a large extent,and the previous inference about the deterioration effect of temperature gradient in the grinding process can be verified by the corresponding results.关键词：Grinding;Finite element;Electromagnetic induction;Preheating;Residual stress7|0|0更新时间：2025-04-28
Optimzation · Reliability
- 摘要：Composite stiffened panel structure is widely used in modern aircraft,which is prone to buckling under working conditions.A large number of tests show that the aircraft composite stiffened thin-wall structure has considerable post-buckling bearing capacity.The design scheme of the stiffened fuselage curved panel with inner cladding and without inner cladding was proposed.The buckling load,bearing capacity and failure mode of the two kinds of curved panels with inner cladding and without inner cladding were calculated by using Abaqus under axial compressive load,pure shear load and compressive shear combined load.In the model,the Tsai-Wu criterion was used as the failure criterion of composite materials,and the damage evolution was realized by the subroutine Usdfld.It is found that the inner cladding of the hat stringer can significantly improve the post-buckling capacity of the structure and prolong the post-buckling process.关键词：Composite;Curved fuselage panel;Inner cladding layer;Hat-stringer stiffened;Post-buckling7|0|0更新时间：2025-04-28
- 摘要：As a typical negative Poisson's ratio structure,the concave hexagon is commonly used in modern energy absorption devices.Based on the honeycomb structure and the concave hexagon,five kinds of structures were firstly obtained through space intersection design.The deformation mechanism and structural mechanical characteristics of five kinds of structures were discussed by finite element simulation and compression test.Then,the transient equivalent calculation method of structural counter-force was given by using vector analysis method,and the calculation formulas of counter-force,collision velocity and acceleration were derived.Counter-force calculation results were compared with compression test,and the test results were basically consistent with the theoretical results.Finally,the optimal structure was filled into the crash box,and the collision simulation analysis was processed with the new crash box.It is found that the mechanical properties of concave honeycomb stucture(CHS)cells with negative Poisson's ratio are better than those of the traditional honeycomb structure(THS).In the second type of structure,C-C structure can increase the structural deformation and reduce the stress.And the stress distribution of C-C structure is more uniform than that of the other structure.The collision simulation results show that the C-C structure crash box can greatly reduce the peak values of speed and acceleration,and the acceleration value is far less than the 40g,which reaches standard in the vehicle collision specification.At the same time,compared with the traditional crash box structure,the energy absorption of the new designed sandwich structure crash box is improved by more than 3 times.关键词：Concave hexagon;Negative Poisson's ratio;Honeycomb structure;Energy absorption;Crash box8|0|0更新时间：2025-04-28
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DESIGN AND PERFORMANCE ANALYSIS OF A TWO-STAGE REDUCED MICRO-MOTION SYSTEM WITHOUT ADDITIONAL MOTION
摘要：In order to achieve a smaller reduction ratio and thus obtain a flexible motion space with higher motion precision,a micro-motion system composed of a two-stage reduction micro-motion mechanism without additional motion and a piezoelectric ceramic actuator was designed,and its driving performance,motion performance and dynamic performance were studied.Based on the principle of flexible hinge lever and the principle of additional motion balance,a two-stage reduction micro-motion mechanism without additional motion was designed,which could realise the precision reduction of input displacement;a piezoelectric ceramic actuator was used to drive the two-stage reduction micro-motion mechanism to form a two-stage reduction micro-motion system;the finite element method was used to complete the analysis of the system's driving performance,kinematic performance and dynamics,and the experimental method to complete the analysis of the system's driving performance and dynamics.The analysis results show that the micro-motion system drive has the advantages of high linearity,small error,etc.,the system has excellent positioning performance,the system dynamic performance is good and will not resonate in the movement process.The research has an important reference value for the design and performance analysis of the micromotion system.关键词：Micro-motion system;No additional motion;Two-stage reduction;Drive performance;Dynamic performance7|0|0更新时间：2025-04-28
Design · Calculation
- 摘要：Dissolved oxygen is one of the main environmental parameter affecting of stress corrosion cracking of austenitic stainless steel in high temperature water environment.Based on the slip-dissolution of stress corrosion theory,a coupled diffusion and cohesion model was built for simulating stress corrosion crack.The stress corrosion cracking behavior of 316L austenitic stainless steel in high temperature water of 325℃ with dissolved oxygen was simulated by finite element analysis using cohesive element.The effects of dissolved oxygen content and cold working on crack growth rate(CGR)were analyzed.The results indicate that,by appropriately calibrating the model parameters,the built model can predict the CGR of stress corrosion cracking under different dissolved oxygen contents,showing that the calculated CGR agrees well with the experimental results reported in the literature.Furthermore,the relationship between the stress corrosion crack growth rate and the yield strength of 316L stainless steel can be fitted as CGR∝σy2.028 in the simulated high temperature water and stress intensity factor conditions.关键词：Finite element analysis;Stress corrosion;Cohesive zone model;Dissolved oxygen6|0|0更新时间：2025-04-28
- 摘要：By changing the geometric parameters such as the size,shape ratio and depth of semi-elliptical surface cracks and elliptical buried cracks in cross-welded joints and oblique welded joints commonly used in high-speed rail bogies,the influence of the geometric parameters on the type I stress intensity factor KI at the crack front was analyzed by a contour integral method.A mathematical expression for solving KI was fitted by a multivariate nonlinear regression method,and the sensitivity of KI to the change of crack size and shape ratio was analyzed by a countour integral method.The results show that KI increases with the increase of crack and gradually diverges or converges according to the difference of joint and crack form.KI decreases and converges gradually with the increase of the crack shape ratio.The location of the maximum point of KI was determined by crack size,crack shape ratio and crack location.The error of the fitted mathematical expression for solving KI was within 5%,and the accuracy is high.Among the four crack forms,the sensitivity of the surface crack KI of the cross joint to the crack shape ratio is obviously lower than that of the other three crack forms,and the sensitivity of the buried crack of the oblique joint to the crack size is obviously higher than that of the other three crack forms.关键词：Welded joint;Stress intensity factor;Strange cell method;Crack size;Crack shape ratio7|0|0更新时间：2025-04-28
- 摘要：As one of the core parts of RV reducer,the fatigue life of cycloidal gears has an important impact on the life of the whole reducer.WorkBench finite element analysis was used to determine the contact stress state and structural weak points of the cycloid gear.On this basis,the mathematical model of contact fatigue life of cycloidal gears was established by Miner linear damage accumulation theory and S-N curve correction theory,and then nCode Designlife,a fatigue life analysis software,was used to analyze the contact fatigue life of cycloidal gears with the maximum contact stress,and the result was 7.6%different from the design life of cycloidal gears under the same load condition.The maximum point of contact fatigue damage of the cycloidal gear was determined.Finally,the reliability of the cycloidal gear was determined based on the contact fatigue life analysis data,which provides a reference for the structural optimization design and reliability analysis of the cycloidal gear.关键词：Cycloidal gear;Basquin equation;S-N Curve;Fatigue life;Reliability8|0|0更新时间：2025-04-28
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MODELING OF FATIGUE CRACK PROPAGATION IN TITANIUM ALLOY TC4 MATERIAL BASED ON THE PERIDYNAMIC THEORY
摘要：In order to more accurately predict the fatigue crack propagation behavior of titanium alloy TC4 under cyclic load,a new prediction model based on peridynamics theory was proposed.Within a finite near-field radius,a material point damage model was constructed to simulate the initiation and propagation of cracks.By establishing the plastic deformation damage model of the"bond",the mechanism of fatigue crack initiation and propagation was deeply analyzed in this study.In order to improve the prediction efficiency and stability of the model,the critical damage factor of material point was introduced,and an improved adaptive dynamic relaxation method is adopted.The static solution can be obtained in each loading cycle,and the reliability of the model was further verified by the convergence analysis of the crack propagation results under different loading conditions.The experimental results show that the fatigue crack growth prediction model based on peridynamics theory can accurately predict the crack initiation location and crack growth rate without relying on additional crack growth criteria.In addition,the fatigue life predicted by the model is in good agreement with the experimental data,which proves the validity and practicability of the model in predicting fatigue crack growth of titanium alloy materials.关键词：Peridynamic model;Domestic titanium alloy TC4;Fatigue cracking;Crack propagation;Fatigue life6|0|0更新时间：2025-04-28 - 摘要：The aging aircraft fuselage skin contains multiple hole edge cracks,and the skin holes will change from circular holes to elliptical holes under loads.The calculation of stress intensity factors for multiple elliptical hole edge cracks is an important problem in a fracture mechanics analysis.An analytical calculation method based on a complex function theory and an approximate superposition method was used to solve the stress intensity factor of multiple elliptical hole edge cracks under the farfield stress,and the change rules of stress intensity factors under several modes of symmetric cracks at the edge of double elliptical holes,inner cracks at the edge of double elliptical holes,outer cracks at the edge of double elliptical holes and cracks on the same side of double elliptical holes were analyzed.The numerical examples show that the stress intensity factor of the crack at the edge of multiple elliptical holes is affected by the crack length,the half-axis ratio of elliptical holes and the spacing of holes.As the crack tip approaches gradually,the interference phenomenon between cracks tends to be significant.8|0|0更新时间：2025-04-28
- 摘要：It's an important task that choosing appropriate fracture parameters and predicting the fatigue crack growth rate accurately considering the different degrees of plastic deformation at the crack tip.The relation between crack tip fracture parameters and a fatigue crack growth rate was investigated by theoretical calculation and experimental analysis under four different fatigue loading conditions.Finally,a suitable model for predicting a fatigue crack growth rate was provided by formulas and the parameter fitting.The results indicate that ΔK representing a fatigue crack growth rate loses its rationality and effectiveness gradually with increases of the load ratio and the load amplitude.At the early stage of the crack propagation,the crack propagation resistance of high load ratio is higher than low load ratio.At the later stage of the crack propagation,the gap between high and low load ratios and the crack growth resistance decreases. ΔJ'ac is the suitable fracture parameter for the fatigue crack propagation of the industrial pure titanium among all of the fracture parameters discussed.On this basis,the corresponding prediction model of the fatigue crack growth rate was proposed.关键词：Fatigue crack growth;Fracture parameter;Prediction model;Load ratio;Load amplitude5|0|0更新时间：2025-04-28
- 摘要：In order to investigate the vibration fatigue characteristics of thin-walled stiffened structures under random vibration loading,a random vibration test was carried out.The structure inherent frequency and modal response were obtained by using the hammering and the sine-sweep method,the cracking time and pattern were recorded.The method for obtaining the fatigue life curve under random stress by revising the fatigue life curve under equal amplitude stress was deduced.Then based on MSC/Patran&Nastran simulation finite-element software,the dynamic response on the fatigue danger point and its random vibration fatigue life were obtained,the effects of creating model methods on the inherent frequency were studied,and the change of damping impacts on the vibration properties was analyzed.The results show that the model stiffness with using mixed element are much closer to the actual structure than only solid or shell,the modal responses under the nonlinear damping are more consistent with the sweep results.Finally,the calculated fatigue life and failure position are in good agreement with the experimental results.关键词：Thin-walled stiffened structure;Random vibration;Power spectral density;Vibration S-N curve;Gaussian three interval method;Dynamic response6|0|0更新时间：2025-04-28
Fatigue · Damage · Fracture · Failure Analysis
- 摘要：The load capacity of the rack and pinion mechanism is limited by the contact strength of the gear tooth surface.In order to improve its load capacity,multiple pairs of gears and single rack meshing were adopted.In order to simplify the structure of the transmission system,a single drive multi-point meshing gear rack and pinion transmission mechanism was proposed,which has the characteristics of strong load capacity,small size,light mass and low cost.However,the mechanism has the gear tooth interference problem,and the gear tooth interference amount was studied to solve the problem,and based on the characteristics that the center distance can be changed by gear tooth displacement,the gear tooth interference problem was solved by the modification coefficient compensation method.The rack and pinion mechanism after modification was analyzed by the gear tooth force.The results show that the gear teeth have no interference and the force is uniform.The solution of the gear tooth interference problem greatly improves the load capacity of rack and pinion transmission,so that rack and pinion transmission can be used for heavy-duty conditions.关键词：Rack and pinion transmission;Gear tooth interference;Gear shifting;Finite element simulation6|0|0更新时间：2025-04-28
- 摘要：As the pressure-bearing part of the floating coupler,the strength of the spherical cover directly affects the pressure-bearing and sealing function of the floating coupler in the process of lowering the casing.Firstly,the theoretical analysis and simulation of the stress of the spherical cover were carried out,and the strength calculation formula of the spherical cover was established based on the spherical shell model under three-way stresses,taking into account the material and compression the damage failure form.Borosilicate glass was selected as the material and its compressive strength was obtained by the compression test.The stress state of the spherical cover was obtained by simulation calculation and the dangerous area was determined.Then the burst pressure of the spherical cover was obtained by the pressure test,and the test and calculation results were compared.The results show that the opening pressure of the spherical cover was 46.2 MPa±3.8 MPa,and no residual glass was inside the floating joint after breaking.The maximum broken particles are less than 10 mm×9 mm×3 mm,which meets the strength requirement of the spherical cover.The results of the study are of great significance to the application of floating coupling in horizontal wells under casing.关键词：Floating coupling;Spherical cover;Borosilicate glass;Opening pressure5|0|0更新时间：2025-04-28
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DYNAMIC CHARACTERISTICS ANALYSIS OF DEEP GROOVE BALL BEARINGS'CAGE UNDER VARIABLE WORKING CONDITIONS
摘要：The dynamic performance of deep groove ball bearings is greatly influenced by the variable operating conditions,mostly the fluctuation of speed of the new energy motor.Taking the 6207 type deep groove ball bearing as the research object,considering the flexible deformation of the cage,the explicit dynamics analysis model of deep groove ball bearings was established in the Ansys/Ls-Dyna software.The influence of different angular acceleration conditions and different rotation fluctuations on the stability and contact characteristics of the cage was analyzed.The results show that the increase of angular acceleration can lead to the increase of velocity fluctuation and the decrease of cage stability.Compared with the stable condition,the contact force and instability between the steel ball and the cage are obviously increased under the rotation fluctuation condi-tion.The influence of speed fluctuation condition on the stability of the cage in descending order is rectangular fluctuation,triangular fluctuation,sinusoidal fluctuation and steady working condition.关键词：Deep groove ball bearing;Dynamics;Variable working condition;Cage stability6|0|0更新时间：2025-04-28 - 摘要：Aiming at the fatigue fracture phenomenon of the pump's circlip,it is necessary to determine the circlip's fracture factors and formulate improving measures.By analysing the force of axial and radial movements of the circlip,it was determined that under normal assembly conditions,the axial impact generated during the opening and closing process of the valve will not lead to the fatigue fracture of the circlip.However,in the abnormal assembly state,metal impurities accumulated in slot and circlip's fillet smaller than the radius of the slot will cause frequent radial shrinkage of the circlip,which were the main factors for the fracture of the circlip.From the perspective of piston pump repair,circlip's fracture suppression measures such as controling the circlip and the slot matching size were formulated,which effectively reduced the possibility of the circlip sliding along the groove rounded trajectory.It is of certain significance to the maintenance application of the plunger pump.关键词：Circlip;High-circle fatigue;Fracture analysis;Simulation analysis7|0|0更新时间：2025-04-28
Research Notes
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