最新刊期
卷 46 ， 期 5 ， 2024
- 摘要：The principal⁃parametric joint resonance of an axially variable⁃speed moving beam with elastic restraint at both ends was studied.Based on Hamilton principle,the magneto⁃elastic nonlinear vibration equation of the beam was derived,in which magnetic field generated by parallel current⁃carrying wires was introduced in modelling.The mode shape function was obtained by means of elastic boundary conditions,and then the Galerkin method was employed to separate time⁃items and space⁃items from each other.The approximate analytical solution and the stability of steady⁃state motion were achieved by multi⁃scale method.In analyzing the computational results,the reliability of the analytical solutions were verified by numerical calculation results corresponding to parameters.In addition,the effects of different parameters on the resonance amplitude and frequency were analyzed.The results show that the stiffnesses of springs and the external excitation force may only affect the amplitude of the system,and the axial velocity,the current and the axial force may lead to the variation of the amplitude and frequency of the resonance,where the stability region increases with the increase of the stiffness of springs.3|0|0更新时间：2025-04-27
- 摘要：Aiming at the problem that the early weak fault feature was difficult to extract of rolling bearing under the strong noise background,combined with the advantages of adaptive local iterative filter(ALIF)and non⁃local means(NLM)method,an ALIF⁃NLM bearing weak fault feature extraction method was proposed.Firstly,a weighted kurtosis⁃energy ratio criterion was constructed to filter the intrinsic mode function(IMF)components of the ALIF decomposition and reconstruct the signal.Secondly,the minimum energy entropy⁃kurtosis ratio index was constructed by combining the sensitivity of kurtosis to the impact signal with the evaluation performance of energy entropy to the uniformity and complexity of signal energy distribution,and using this index as the fitness function,the adaptive selection of parameter combinations in NLM method was realized by particle swarm optimization(PSO)algorithm.Finally,the fault feature of the reconstructed signal was extracted with the adaptive NLM.The simulation and experimental results show that this method can effectively extract the weak fault feature information of rolling bearing under the strong noise background.关键词：Strong noise;Rolling bearing;ALIF;Particle swarm optimization;NLM;Weak feature extraction2|0|0更新时间：2025-04-27
- 摘要：A dynamic model of vibration system with single degree of freedom with dry friction-rigidity constraint was established,and the dynamic constraint conditions of piecewise smooth vibration system considering the coupling conditions of dry friction and collision were given.At the same time,the nonlinear stiffness factor was introduced,and the response periodic motion types and distribution regions of the system were obtained by co-simulation method.The dynamic characteristics of motion viscosity and displacement viscosity of mass blocks were discussed,and the basic periodic transition rule in the low frequency and small clearance parameter domain was quantitatively characterized.The results show that the velocity viscosity response between the mass block and the belt is mainly affected by the excitation frequency.Due to the existence of dry friction,the velocity of the first collision between the mass block and the restraint surface is more complicated.The crash-vibration response between the mass block and the rigid constraint has a strong correlation with the clearanceδand excitation frequencyω,and abundant dynamic response characteristics appear in the parameter domain of low frequency and small clearance.关键词：Dry friction;Rigid constraint;Velocity of sticking;Displacement of sticking;Chattering-impact2|0|0更新时间：2025-04-27
- 摘要：There is a certain height difference between the two belts at the transfer point of the belt conveyor in the coal preparation plant.Affected by factors such as the size of the coal block on the upper end face and the water content,it will cause different degrees of vibration impact on the belt conveyor,thus affecting the service life of the belt conveyor body and the roller.In order to explore the influence of the material flow on the vibration impact of transfer point,combined with field investigation and related theories,it was concluded that the main influencing factors of blanking impact are material flow particle size level and water content.Then,the field test was carried out by using optical fiber vibration sensor,data acquisition card and Labview test system.The vibration signals of the belt conveyor under the blanking port under the impact of different material flows were collected and processed.The test results show that the vibration impact of different particle size material flows on the transfer point is different.The peak value of the vibration waveform of the small particle size material flow on the transfer point is 20%of the large particle size material flow,and the peak value of the self-power spectrum waveform is 0.625%.Different water content has different vibration impact on the transfer point.The peak value of the vibration waveform of the material flow with less water content is 60%of the material flow with more water content,and the peak value of the self-power spectrum waveform is reduced to 45%.The research results provide a reasonable method for reducing the vibration impact of the belt conveyor transfer point.关键词：Belt conveyor;Transfer Point;Vibration shock;Light vibration sensing2|0|0更新时间：2025-04-27
- 摘要：The thermal management system of new energy vehicles directly affects the overall vehicle performance,placing stringent demands on the performance and reliability of the scroll compressor for air conditioning,with particular emphasis on the mass imbalance response of the scroll compressor drive shaft for its performance and service life.For a certain type of scroll compressor drive system with a design speed of 0~7000 r/min,based on the distributed mass model,the intrinsic characteristics of the shaft system and the unbalance response at different speeds were analysed by using the modal method.Considering the robustness of the simulation speed setting,the rotor system was set at 0~7000 r/min,and the first six orders of the intrinsic frequency,vibration mode and the positive vortex criticality were obtained.The first six orders of intrinsic frequencies,vibration mode and critical speeds of positive eddy currents were obtained for the rotor system at 15452 r/min and 32839 r/min,and the deformations and stresses of the spindle eccentric pins,the balancing block and the tail section were analyzed by the harmonic response analysis under the excitation of the gas loads to obtain the variation of the frequencies.Finally,the prototype was experimented,and the measured acceleration time-domain and frequency-domain response curves were obtained.The results show that the scroll compressor does not reach the critical speed under the design speed of 0~7000 r/min;the unbalanced vibration at 271.96 Hz and 517.01 Hz and its side frequency has a greater impact on the rotor,which is consistent with the results in the harmonic response analysis.The study provides a reference for the vibration finite element analysis and structural optimization of the scroll compressor.关键词：Scroll compressor;Modal analysis;Critical speed;Harmonic response analysis2|0|0更新时间：2025-04-27
Vibration · Noise · Monitoring · Diagnosis
- 摘要：Percentage elongation after fracture is a typical index to characterize the plasticity of the pipe,and the partial size of the pipe such as the welded joint can not carry out a single⁃axis tensile test,and it is necessary to complete the sampling and testing with the help of micro⁃specimen test methods.As a micro⁃specimen test method,the small punch test can be used to obtain a variety of mechanical property parameters.In the current study,the key parameters such as the maximum displacement,the corresponding displacement of the maximum load and the arc length after fracture are correlated to the percentage elongation after fracture of the material mainly through the empirical correlation method.However,the applicability of the above method to pipeline steel is not clear,making it impossible to directly apply to pipeline steel materials.In view of this problem,firstly,the applicability of the above⁃mentioned empirical association method based on different characteristic parameters to pipeline steel was discussed,and then a simplified calculation method for arc length after fracture was provided,and an empirical association formula based on the arc length after fracture for the pipeline steel was formed.On this basis,the thickness effect correction was carried out,and the empirical formula for determining the percentage elongation of pipeline steel material after fracture was established based on small thickness specimens and the reliability was verified.The results show that the maximum error of the percentage elongation after fracture determined by the empirical association formula based on the simplified calculation method of arc length after fracture is 5.08%,and the maximum error of the thickness effect correction formula for the calculation result of small thickness specimen is 5.53%,which proves that the established empirical association formula has good fitting effect and good applicability to pipeline steel,which can provide a theoretical basis for the calculation of percentage elongation after fracture in the local area of other steel grade pipelines.关键词：Small punch test;Uniaxial tensile test;Percentage elongation after fracture;Pipe steel;Arc length after fracture;Thickness effect2|0|0更新时间：2025-04-27
- 摘要：In order to evaluate the reasonable simplified form of local wide and shallow corrosion pits on 24 steel specimens,two commonly used simplified characterization methods of semi⁃ellipsoid and spherical cap shape were selected respectively.Firstly,the calculation formulas for the volume of corrosion pits and the curvature radius of the profile of the cross section were derived.Then,the test errors of electrochemical accelerated corrosion were analyzed,and the uniaxial tension finite element analysis results of four typical steel specimens with corrosion pits were compared with their actual fatigue fracture situations.The results show that under a certain power on time,compared with the predetermined rust volume calculated by Faraday′s law,the maximum deviation of the semi⁃ellipsoidal corrosion pits′volume obtained from the measured sizes of corrosion pits reaches 53.2%,with an average deviation of 20.26%,while the maximum deviation of the spherical cap shaped corrosion pits′volume is only 32.3%,with an average deviation of 12.8%.The maximum stress points of the semi⁃ellipsoidal corrosion pits are located at the edge of the top,while the maximum stress points of the spherical cap shaped corrosion pits are mostly located at the bottom.Only when the ratio of depth to radius is larger,it is located on the trisection point of the connecting line between the bottom and the top,near the pit mouth.The danger areas indicated by the spherical cap shaped corrosion pits are in better agreement with the initiation positions of the main cracks in the fatigue fracture process of the specimens.Under two simplified forms,the differences between the pits corrosion volume and the curvature radius of the cross section profile on the specimens increase with the decrease of the ratio of depth to radius,and the relative deviation of the latter can be more than 90%,which is the main reason for the larger differences in the stress distribution.关键词：Wide and shallow pit;Simplified form;Electrochemistry;Accelerated corrosion;Fatigue fracture4|0|0更新时间：2025-04-27
- 摘要：The pre⁃folded energy absorber is the only energy absorber structure used in rock burst mine at present.It has excellent energy absorption characteristics,but there are some problems in the buckling deformation process such as large load fluctuation and spark due to friction.In view of the above situation,a sinusoidal bellows(reduced diameter round pipe)filled with emulsion was designed to form a solid⁃liquid coupling body energy absorption component(composite component).The effects of three factors,namely wall thickness of the bellows,amplitude of the busbar and diameter of the liquid outlet,on the energy absorption characteristics of the energy absorption component were studied.The prediction model of average load,load fluctuation coefficient and specific energy absorption was established.The smoothed partiole hydrodynamics(SPH)particle algorithm of Abaqus finite element software was used for fluid⁃structure coupling analysis of the model.The structural parameters of energy absorption components were optimized by response surface method and the optimization results were obtained.The results show that when the wall thickness of corrugated pipe is 3.959 mm,the amplitude of busbar is 3.721 mm,and the diameter of outlet is 22.161 mm,the energy absorption characteristics of the member are the best.The average load is 438.684 kN,the load fluctuation coefficient is 1.178,and the specific energy absorption is 12.123 kJ/kg.Through comparison and verification,the results have high reliability,which provides a superior energy absorption component for the energy absorption link of anti⁃impact support equipment.关键词：Energy absorbing component;Fluid⁃structure interaction;Response surface;SPH particles2|0|0更新时间：2025-04-27
- 摘要：Three kinds of micro-sample thicknesses(0.4 mm,0.5 mm and 0.6 mm)and three kinds of chamfer radii(0.5 mm,0.8 mm and 1.0 mm)of the original main pipe material were taken as the research objects to analyze the influence of restraint intensity in hydraulic bulging test,and to build a correlation model of yield strength,tensile strength and hydraulic bulging elongation.The fitting error of yield strength and tensile strength and the dispersion of hydraulic bulging elongation were studied.The results show that with the gradual increase of microspecimen thickness,the peak load increases obviously,while the peak displacement generally decreases,but the overall curve trend changes little.With the gradual decrease of the microsample chamfer radius,the peak displacement decreases obviously.The test stability is best under the test conditions of microsample thickness 0.5 mm and chamfer radius 1.0 mm.关键词：Hydraulic bulging;Restraint intensity;Yield strength;Tensile strength;Chamfer radius2|0|0更新时间：2025-04-27
Experimental Research · Testing Technology
- 摘要：Extreme climatic conditions,such as hot,cold and hot-humid environment,affect the bearing performance and the life expectancy of composite and metal hybrid structural components in aircraft,which have a great impact on the flight performance and safety of the aircraft.Due to the large coefficient of thermal expansion mismatch between the composite and metallic structures,the temperature change in the actual flight condition induces high thermal stresses in both composite component and metallic component.This additional stress would alter load transfer and internal stress distribution in fastened hybrids of composite and metallic structure.Thermal/mechanical behavior of the large-scale,multi-joint hybrid composite/metal structure was investigated experimentally in different temperature conditions,as well as bearing axial load under different temperatures.The internal stress distribution of different components and fasteners in hybrid composite/metal structure under different temperature and load conditions was obtained by the strain gage method.关键词：Composite material;Hybrid structure;Temperature effect;Thermal stress2|0|0更新时间：2025-04-27
- 摘要：For improving the quick‑return characteristics of the sley movement,an optimal mathematical model for maximum curve displacement Sm of the connectingarm pin was proposed through beating‑up principle analysis and mechanism deduction.A multivariable design space was constructed by use of the component length(lc,lh,lr,lf)and crankangleα.The parametric functional model development of the four‑bar beating‑up with short connecting rod was realized,and its kinematic posture and centroid trajectory were analyzed and verified through mechanism simulation.The results of the case study indicate that the variable lc andαhave more greater influence on the sensitivity of the objective function F(X),and multivariable(DV_1,DV_2,DV_3)coupling can effectively enhance the design plasticity of the quick‑return characteristics of the sley.When the maximum curve displacement Sm of the connectingarm pin increases to 71.41 mm,the extreme position angleθand the travel speed ratio coefficient K are increased by 10.96°and 0.131 respectively,and the quick-return motion effect of the sley is obviously improved.The optimization results accord with the conditions of rod length and mechanism transmission requirement,which are conductive to the design innovation and performance improvement of the four‑bar beating‑up system.关键词：Four⁃bar beating⁃up;Quick⁃return characteristic;Connecting rod;Transmission angle;Optimiza⁃tion;Posture;Sensitivity2|0|0更新时间：2025-04-27
- 摘要：The enhancement of truck mounted attenuators(TMAs)crashworthiness is an important way to protect vehicle safety.A new porous structure was generated by Voronoi algorithm.Firstly,the influence of the parameter,the seed number n,porosity of the structureρand irregularityαof porous structure on geometric topology was studied.The mathematical model between the specific energy absorption and the three parameters was established.Then,by the finite element method,the energy absorption of the new structure was analyzed,and the reliability of the mathematical model was confirmed.The optimal structural parameters were determined by orthogonal experiment.Finally,the new porous structure was filled into the TMAs as a sandwich,and the crashworthiness of the vehicle under three working conditions(forward collision,side collision and oblique collision)was discussed.It is found that the new porous structure can effectively reduce the peak impact force,and its energy absorption performance is far better than that of traditional TMAs and cylindrical sandwich TMAs,which can effectively protect the safety of crashed vehicles and drivers.关键词：Voronoi algorithm;Porous structure;Sandwich structure;Parameter optimization;Crashworthiness2|0|0更新时间：2025-04-27
- 摘要：Taking the E⁃type multi⁃link rear suspension system of a domestic SUV as the research object,its topological structure and kinematic relationship were analyzed.The rigid⁃flexible coupling rear suspension system motion model was established by using Adams/Car and Hypermesh software.Taking the change of wheel camber and camber toe⁃in as the optimization objective,the coordinate values of the inner and outer points of the upper control arm and toe tie rod were set as design variables.Then,the design was optimized in Adams/Insight.Through the comparison of simulation curves before and after optimization,it is shown that the change of wheel camber and toe is reduced,and the kinematics characteristics are improved to some extent.At the same time,the accuracy of the simulation results is further verified in the actual vehicle suspension ride test.关键词：Adams/Insight;E⁃type multi⁃link rear suspension system;Optimal design;Ride test2|0|0更新时间：2025-04-27
Optimzation · Reliability
- 摘要：For the patients with lower extremity motor dysfunction caused by stroke and aging,a new weight loss system for double axillary support lower limb rehabilitation based on barycentre trajectory of human body was developed.Firstly,the influence of weight loss support training on plantar pressure was analyzed and studied.Secondly,based on ergonomics theory and the study of barycentre trajectory of human body,the overall structure was analyzed and designed,and the relevant size was determined.Thirdly,the reliability of the structure was verified by statics analysis.Finally,the kinematics analysis and dynamic simulation of the weight reduction module were carried out.The system can help the patients with lower extremity motor dysfunction realize the rehabilitation training of imitating the normal walking.关键词：Lower limb rehabilitation;Weight reduction support;Barycentre trajectory of human body;Plantar pressure;Structural design;Dynamic simulation2|0|0更新时间：2025-04-27
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PARAMETER ESTIMATION AND CONFIDENCE LIMIT CALCULATION METHOD OF THREE-PARAMETER WEIBULL DISTRIBUTION
摘要：A correlation-regression method was proposed to solve the problem of low accuracy of parameter estimation and confidence limit calculation of the three-parameter Weibull distribution.The method was combined by the correlation coefficient method(Fu method)and the nonlinear regression method which makes full use of the convenience of Fu method and the excellent estimation effect of the nonlinear regression method in estimating the three-parameter Weibull distribution.In order to verify the effectiveness of the proposed method,the correlation-regression method,Fu method and the method combining maximum likelihood estimation and empirical formulae(referred to as the“MMPDS method”)were applied to the parameter estimation and confidence limit calculation of the data distribution of a certain alloy strength value with different sample sizes,and calculation consequence of different methods was compared and analyzed.Results show that the correlation-regression method has higher parameter estimation and confidence limit calculation accuracy among the above methods.When the sample size is less than 100,its advantage is more significant,and it can accurately calculate the parameters and confidence limits of the Weibull distribution.关键词：Weibull distribution;Parameter estimation;Confidence limit2|0|0更新时间：2025-04-27 - 摘要：The prosthetic stalk contacting with the femur is the main component of the artificial hip joint and plays an important role in total hip replacement surgery.The topology optimization method of solid isotropic material with penalization(SIMP)and the multi⁃scale parallel topology optimization method were used to obtain the two femoral⁃stalk structures of type A and type B,and the sensitivity of the two femoral stalks to the change of load direction was compared with the amplitude of the flexibility of the femoral stalk structure as a comparison index.The finite element method was used to analyze the stress of the corresponding femur under multiple conditions of type A femoral stalk and type B femoral stalk.The results show that under the three working conditions,the average stress of type A femoral stalk and type B femoral stalk to the femur is 14.80,22.55,16.94 MPa and 10.89,20.92,16.50 MPa.The pressure loading experiment was performed on a type B femoral stalk.The experimental results show that for the inner measurement point,the average error between the strain values and simulated values of this experiment is-1682με,and the average relative error is 20.3%.For the outer measurement point,the average error between the strain values and the simulated values is 1281με,and the average relative error is 19.5%.This method provides an effective reference for the reliablilty design of the femoral prosthesis stalk structure.关键词：Topological optimization;Femoral stalk structure;Finite element analysis;Reliability2|0|0更新时间：2025-04-27
- 摘要：The tissue engineered bone provides an important method for repairing large segmental bone defects.However,how to design a prosthesis that matches the mechanical properties of host bone remains to be studied.Therefore,this study aimed to explore the scaffold mechanical properties based on selective laser melting(SLM)fonning printing technology for scaffold and apply to mandibular reconstruction.Firstly,hexahedral(HE),octahedral(OC)and body centred cubic(BCC)unit cell porous scaffolds with different porosity(50%-80%)were established,and the porous scaffold mechanical properties were analyzed by finite element analysis.Secondly,the porous Ti6Al4V scaffolds with strong mechanical properties were prepared by SLM forming technology,and the scaffold mechanical properties were evaluated by the compression test.Finally,the least square method was used to fit the scaffold porosity⁃elastic modulus curve,so as to obtain the porous prosthesis with mechanical properties matching the mandibular defect region.The results show that the maximum stress of porous scaffold increases with the increase of porosity and is closely related to the configuration(BCC>OC>HE).The compression test shows that the scaffold elastic modulus with different porosities is significantly different,and the porosity is inversely proportional to the elastic modulus.According to the Gibson⁃Ashby model of hexahedral unit cell scaffold,the ideal prosthesis porosity is 53.1%.Additionally,the safety of the prosthesis is verified by finite element analysis.The finite element analysis and compression test confirmed that the scaffold mechanical properties with different porosities are discrepant,and the optimized prosthesis with appropriate porosity can better match the mechanical properties of host bone,which provides valuable insights for implant design.关键词：SLM;Porous scaffold;Elastic modulus;Porosity;Mandibular prosthesis3|0|0更新时间：2025-04-27
- 摘要：The lightweight design of diaphragm pump base structure has an important impact on the processing and production of diaphragm pump.Based on the research of the frame structure of a certain type of diaphragm pump,the equivalent model was established for the actual working environment and the finite element analysis was carried out.The design variables were defined according to analysis results to improve the calculation efficiency.The uniform test design method was adopted for the test design,and the relationship between the design variables and the stress and deformation was calculated through simulation fitting.The lightweight optimization mathematical model was established for the diaphragm pump base structure by using the multi-objective optimization algorithm.On the premise of meeting the performance requirements,some materials were reasonably configured,and the stress,deformation and natural frequency of the diaphragm pump base structure were as small as possible.The frame structure after the lightweight optimization design was simulated and analyzed,and compared with the structure before optimization.The results show that the structural properties of the engine base remain unchanged after lightweight,and the weight is reduced from 25372 kg to 24582 kg,with a weight reduction of 790 kg.The weight reduction effect is good,the maximum stress value is reduced by 45.1%,and the maximum deformation is reduced by 12.3%.The optimization effect is remarkable,which provides a basic support for the finite element analysis and lightweight optimization design of the new diaphragm pump structure.关键词：Diaphragm pump;Base;Multi-objective optimization;Lightweight;Uniform design method2|0|0更新时间：2025-04-27
Design · Calculation
- 摘要：The 4%weight percentage TiC reinforced FeCrB based anti⁃wear composite was designed and prepared by powder metallurgy technology.The effects of sliding speed and load on the dry friction and wear properties of the composite were systematically studied by reciprocating dry friction experiments with GCr15 steel ball pairs.The X⁃ray diffraction(XRD),scanning electron microscope(SEM)and other techniques were used to analyze the phase composition and micro morphology of the composite.The experimental results show that the phase of the composite isα⁃Fe,FeCr,TiC,Cr2B and Fe2B.The addition of TiC significantly increases the hardness of the material and slightly decreases the density.With the increase of sliding speed and load,the friction coefficient decreases generally and the wear rate increases significantly.The pinning strengthening effect of TiC on the Fe matrix composite inhibits the spalling and deformation of the material,and the wear resistance of the material is significantly improved.Through comprehensive analysis,TiC can effectively improve the dry tribological properties of FeCrB alloy,and its wear mechanism is mainly delamination wear and abrasive wear.关键词：Fe matrix composite;TiC;Dry friction;Wear resistant;Wear mechanism2|0|0更新时间：2025-04-27
Weld · Casting · Forge · Thermal Material
- 摘要：Mechanical parts such as gas turbine blades are often subjected to low cycle fatigue caused by low⁃frequency centrifugal force and high cycle fatigue caused by high⁃frequency vibration loads during the working process,and the damage caused by the combined cycle loadings is one of the important factors for fatigue.The damage generated under the combined high and low cycle loading is not a simple damage superposition,and the coupled damage due to the interaction of high and low cycle loading also needs to be considered.On the basis of Miner′s rule,through considering the coupled damage caused by the interaction between high and low cycle loading,combined high and low cycle fatigue life prediction model was established.The proposed model was compared with the Miner model and the Trufyakov⁃Kovalchuk model through the material test data.The results show that the proposed model has a good prediction accuracy.关键词：Combined high and low cycle fatigue;Coupled damage;Fatigue life;Low cycle fatigue;High cycle fatigue2|0|0更新时间：2025-04-27
- 摘要：The macroscopic failure behavior of metal materials is closely related to the damage evolution of microstructure.In addition to in⁃situ loading experiments,advanced numerical methods are used to simulate and predict the microstructure evolution of metal materials,which has gradually become an effective tool to study the multi⁃scale damage evolution mechanism of metal materials.At present,the dislocation motion inside polycrystalline metal grains can be simulated by crystal plastic finite element method,but there are still challenges in the simulation of damage accumulation and microcrack initiation caused by dislocation.For most metal polycrystalline materials,dislocations are usually plugged at grain boundaries leading to stress concentration and then cracking at grain boundaries.Therefore,the simulation of the whole process requires the construction of a numerical model that can describe both dislocation motion and grain boundary cracking.In order to solve this problem,combining the crystal plastic finite element model with the cohesive zone model to achieve a uniform description of material microscopic deformation and damage,and a global finite element model to describe dislocation motion and grain boundary cracking was established.Then,taking polycrystalline Cu⁃Ni⁃Si alloy as the research object,the microstructure evolution process from deformation,crack initiation,crack propagation to fracture was simulated,and the mechanism from local intergranular fracture to global failure was revealed,and the effect of grain orientation on initial fracture location and crack propagation was clarified.This model provides a feasible methodology for multi⁃scale damage evolution simulation of the failure behavior of various metal materials.关键词：Crystal plastic;Cohesive zone;Finite element modelling;Polycrystalline metal;Deformation and fracture2|0|0更新时间：2025-04-27
- 摘要：The numerical simulation along the C-axis stretching process of a single crystal magnesium model with preset cracks and void defects was carried out by molecular dynamics method,and the effect of void defects at different positions on crack propagation in single crystal magnesium was studied.The simulation results show that under the same characteristic size,the yield strength of the single crystal magnesium model is affected by the voids at different location.When the voids are located in the crack[101—0]direction,the yield strength of the model is the lowest.The void can alleviate the stress concentration of the crack in the void direction,and affect the twins growth rate of the crack.The twin growth rate near the void of the crack is relative slowly,and the twin growth rate is the slowest when the void is located at[101—0]direction.The voids have a little influence on the propagation direction of the crack.Generally,the crack extends in the tensile direction after combining with the voids,and the overall appearance is a more symmetrical cone expansion.But,when the voids are located in the crack[0001]direction,there is no obvious connection between the cracks and the voids.关键词：Single crystal magnesium;Void;Crack;Twin;Molecular dynamics2|0|0更新时间：2025-04-27
- 摘要：For the equivalent strain model,the additional strengthening effect of the material cannot be considered during multiaxial non-proportional loading,resulting in a defect with a large error in fatigue life prediction,based on the pro-interface theory,the maximum shear strain amplitude was used as the main fatigue damage parameter.At the same time,the phase difference,maximum normal stress and shear stress were composed of an additional damage coefficient as a secondary damage parameter to reflect the additional strengthening effect of the metal material under multiaxial non-proportional loading,and the shear stress on the maximum shear surface in the damage coefficient normalized the maximum normal stress to reflect the influence of the interaction between the two stresses on the fatigue life.The proposed model not only retains all the advantages of the equivalent model parameters without introducing additional empirical fitting constants,but also helps to discover the mechanism of crack generation and reflect the direction of crack elongation.The proposed model and three classical models were verified by using six kinds of metal material data of thin-walled round tubes,after analyzing the data verification results of each model,it is found that the prediction results of the proposed model have higher accuracy and more stable data distribution.关键词：Multiaxial fatigue;Equivalent strain;Non-proportional additional reinforcement;Shear force;Phase difference2|0|0更新时间：2025-04-27
- 摘要：Aiming at the safety and economic requirements in practical engineering,a type I fatigue crack propagation rate prediction model was proposed based on the Hutchinson-Rice-Rosengren(HRR)stress-strain field.The stress-strain distribution state of the crack tip region was described by the HRR stress-strain field,and a crack tip damage area was defined under the premise of considering the cyclic load and strain energy density theory.At the same time,in order to eliminate the problem of stress singularity value of the crack tip,a passivation radius calculation method considering the passivation effect of crack tip was established.Combining RICE′s plastic superposition method with plastic strain energy failure criterion,a type I fatigue crack propagation rate model was developed.The crack propagation rates of nine metallic materials were calculated using the proposed LIUX(HRR)prediction model,and the calculation results of the two crack propagation prediction models of Pandey(HRR)and CHEN-CAI Rice-Kujawski-Ellyin(RKE)were compared.At the same time,based on the different requirements of R2 fitting effect and fatigue crack propagation in the three stages,the scoring results of three prediction models were given,and corresponding scores were given from three aspects,safety,accuracy and economy.The final results show that the LIUX(HRR)prediction model in this paper has a wider scope of application,better fitting effect,and can better meet the needs of economy and safety in practical engineering.关键词：Crack tip;HRR stress-strain field;Plastic strain energy failure criteria2|0|0更新时间：2025-04-27
- 摘要：It is impossible to overlook the impact of residual stress on the fatigue strength and service life of gears.The research on the mechanism of residual stress on the fatigue strength of gears is of great significance for extending the gear's operational lifespan and enhancing its service performance.Although a great deal of research has conducted,no consensus has yet been achieved regarding the mechanism of residual stress in gear fatigue.Firstly,a systematic description of the generation mechanism and control method of residual stress was provided.The research progress on the impact of residual stress on gear fatigue properties and the existing testing methods of residual stress was summarized.Ultimately,the challenges encountered in the present study were sorted out,and three areas of future research were explored:quantitative research,regulation approaches and residual stress testing technologies.关键词：Gear;Residual stress;Fatigue property;Measuring and testing technique;Regulation approach3|0|0更新时间：2025-04-27
- 摘要：In view of the materials fatigue life prediction problem under step blocks specturm,especially the calculation parameters of the existing nonlinear models depend on a large number of test data or it is difficult to select a suitable reference value,which leads to the limitation in practical engineering application.A new effect coefficient αi=(Si+1/Si)1/b lg K based on adjacent load was proposed,in which the two parameters b,K were derived from the fatigue life relation S=KN-b.The fatigue damage models and the results which combined with the previous experimental results of two-,three-and four-stage loading were calculated and compared.The results show that the new model has better fatigue life/damage predicted results than Miner model,Manson model,Subramanyan model and Hashin model,which can be predicted more accurately in fatigue life/damage under step blocks spectrum.关键词：Step blocks spectrum;Fatigue damage;Fatigue life;Multi-stage stress;Effect coefficient2|0|0更新时间：2025-04-27
- 摘要：The prediction of real and extreme irregular crack front growth paths directly determines the accuracy of evaluating residual fatigue life of structures.A method for studying the distribution of stress intensity factor(SIF)along the extremely irregular crack fronts was developed by using a notched member,which was geometrically most similar to an engineering structure,as the cracked body.Firstly,the local curvature changes caused by convex,concave,and small curvature radii along the crack front were characterized by high-resolution spline curves.Then,based on the sub-model method combined with adaptive meshing technique,the growth trajectory of irregular crack front was iteratively simulated to obtain the irregular crack propagation law.Finally,by comparing the predicted crack geometry with the experimentally measured crack location,size,and other information,the reliability of crack propagation driving force simulated by Franc3D was verified through examples.The results show that the predicted crack front trajectory basically coincides with the actual,and the SIF values along any normalized growth path are basically equal.The predicted residual life is very close to the experimental life,with an error of only 2.4%.关键词：Stress concentration;Adaptive meshing;Submodeling method;Irregular crack front;Growth law2|0|0更新时间：2025-04-27
- 摘要：In response to the delamination phenomenon of composite materials,combined with a trilinear cohesive force model considering brittle fracture of materials,an Abaqus user subroutine was written using Fortran language to establish a three⁃dimensional progressive damage analysis model for composite laminates with a hole.Uniaxial tensile tests were conducted for four different layering methods,and modeling was conducted by using the commercial finite element analysis software Abaqus to analyze the hole edge damage of laminated plates.The results indicate that the proposed model can effectively predict the ultimate load and damage morphology of uniaxial tensile failure of composite laminates with a hole,and the failure zones of laminated plates are mainly concentrated at the hole edge.The research methods and results of this model can provide a reference for the design and maintenance of composite laminates.关键词：Composite laminates with a hole;Delamination growth;Brittle fracture;Uniaxial tensile;Progressive damage2|0|0更新时间：2025-04-27
Fatigue · Damage · Fracture · Failure Analysis
- 摘要：Taking the constant velocity universal joint drive shaft of a car under torsional load as an example,a heat treatment-hardness gradient design method based on the strength gradient was proposed.That was,the ideal strength gradient distribution was obtained according to the maximum stress and its gradient distribution of the dangerous section of the structure.Then,the ideal hardness gradient distribution was obtained from the hardness-strength conversion relation.Finally,the actual hardness gradient was matched according to the ideal hardness gradient distribution combined with the material end quenching curve.The hardness gradient matching of the drive shafts made of 40Cr,UC2 and 38B3 materials was carried out respectively,and the static strength test of the transmission shaft after the hardness gradient matching was carried out.The test results show that the static strength of the transmission shafts made of different materials can meet the test requirements after the heat treatment-hardness gradient matching.关键词：Hardness gradient;Strength gradient;Heat treatment;End quenching curve;Static strength2|0|0更新时间：2025-04-27
- 摘要：The fatigue test of industrial pure titanium notched specimens was carried out.Combined with digital image correlation(DIC)technology,the surface strain field of the specimen,the local strain at the notch root,and the fatigue crack propagation length were obtained,and the fatigue crack initiation and propagation stages were divided and characterized.The experimental results show that,in the fatigue crack initiation stage,the strain concentration factor obtained by DIC increases as the notch radius decreases,which is consistent with the theoretical stress concentration factor.When the cyclic strain at the notch root accumulates to a certain extent,the micro-cracks initiate.At this time,the increase of load causes the local strain rate to increase sharply,then decrease briefly and increases again until the appearance of macro-cracks.When macro-cracks appear,the fatigue crack propagation of TA2 is characterized by the stress intensity factor,which increases with the increase of load and crack length.The results show that the notch fatigue crack initiation and propagation can be characterized based on DIC technology,which can provide a basis for the safety assessment of titanium equipments.关键词：Notch fatigue;Digital image correlation;Fatigue crack initiation;Fatigue crack growth3|0|0更新时间：2025-04-27
- 摘要：The ultrasonic nanocrystal surface modification(UNSM)technique can build a strengthened layer with good surface integrity on the metal surface,and this layer improves the mechanical properties of metals.The effect of multiple UNSM on the surface integrity of 304 stainless steel was investigated,and a good strengthened layer was obtained.The surface of 304 stainless steel sample was strengthened by multiple UNSM technique,and the strengthened layers with different depths were prepared on the surface of the material.The hardness gradient,residual stress gradient,microstructure gradient and surface morphology of the sample were measured by using the microhardness tester,X⁃ray residual stress analyzer,3D morphometer and metallographic microscope.The results show that the grain size of 304 stainless steel is obviously refined after multiple UNSM treatment,and the thickness of the strengthened layer increases with the increase of treatment times.Comparing with the untreated sample,after two times of UNSM treatment,the residual stress on the surface of the sample increased from-156 MPa to-425 MPa,the depth of residual compressive stress reached 0.7 mm,and the surface microhardness increased from 185 HV0.2 to 350 HV0.2.The results show that the UNSM technology can build a deeper strengthening layer,but it needs to be optimized.关键词：Ultrasonic nanocrystal surface modification;Surface roughness;Microhardness;Residual stress;Strengthened layer2|0|0更新时间：2025-04-27
Research Notes
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