最新刊期
期 5 ， 2021
- 摘要：Based on Reissner’s sandwich plate theory,the nonlinear dynamic equations of the circular sandwich plate under static load are established by using the Hamilton principle. The axisymmetric nonlinear vibration differential equation of the plate under static load is obtained by Galerkin method. The amplitude-frequency response equation of the primary resonance system is solved by means of a method of multiple scales,and the stability criterion of the steady motion of the system is obtained based on the Lyapunov stability theory. Through the numerical example,the amplitude-frequency response curves of primary resonance of the system with simply supported edge are obtained. The curves of the amplitude varying with static load,excitation and thickness of the core layer are plotted,respectively. The effects of different parameters on the resonance amplitude are discussed,and the stability of steady-state motions of the system is analyzed.关键词：Circular sandwich plate;Static load;Primary resonance;Stability;Method of multiple scales
- 4
- |
- 158
- |
- 0
发布时间：2022-09-22 - 摘要：Aiming at the nonlinear and instability characteristics of the wind turbine gearbox bearing fault signal,a method based on the Fuzzy Entropy and Grey Wolf Optimizer Support Vector Machine（ GWO-SVM） for the fault diagnosis of gearbox was proposed in this paper. Firstly,EEMD was used to decompose the vibration signal into the several intrinsic mode functions（ IMFs）. Secondly,calculated the IMFs’ fuzzy entropies in each state and constructed feature vectors. Finally,the vectors were adopted as the input parameters for the GWO-SVM to diagnose the fault. The results prove that the fuzzy entropy of gearbox vibration signals in different states has a certain degree of discrimination,it can be identified and classified by GWO-SVM accurately. Meanwhile,GWO-SVM is compared with PSO-SVM and GA-SVM,it has shorter time and higher accuracy,the mean accuracy can up to 92. 5%.关键词：Wind turbine gearbox;Fault diagnosis;Ensemble empirical mode decomposition;Grey wolf optimizer;Support vector machine;Fuzzy entropy
- 5
- |
- 551
- |
- 5
发布时间：2022-09-22 - 摘要：In this paper,the characteristics of flexural vibration suppression of a beam using rotational dynamic vibration absorbers are studied. Vibration equations of the beam carrying rotational dynamic vibration absorbers are established using the spectral element method. Then the influences of the installation location,the moment of inertia of the rotational dynamic vibration absorber on the wide band vibration attenuation are analyzed. The numerical analysis result shows that rotational dynamic vibration absorbers have a good performance of suppressing flexural vibrations of beam structures. A widest vibration reduction bandwidth and a maximum energy absorption capacity can be obtained when the rotational dynamic vibration absorbers are installed on the position of maximum modal angular displacement. The increase of the moment of inertia of the rotational dynamic vibration absorbers can also improves the vibration attenuation performance. Finally,the vibration attenuation effect of the rotational dynamic vibration absorber is verified by the experiment. The experiment result also illustrates the advantages of the rotational dynamic vibration absorber that it can improve the vibration reduction performance without increasing the additional mass.关键词：Rotational dynamic vibration absorber;Beam;Flexural vibration attenuation;Wide band;Spectral element method
- 5
- |
- 142
- |
- 0
发布时间：2022-09-22 - 摘要：Aiming at the problem that the fault feature information of rolling bearing is weak under the strong background noise environment,and the single use of the complete ensemble empirical mode decomposition with adaptive noise（ CEEMDAN）method is not effective in extracting the fault feature,a method based on parameter optimized multi-point optimal minimum entropy deconvolution adjusted（ POMOMEDA） and CEEMDAN was proposed. Since the filter effect of MOMEDA is greatly affected by its parameters — fault period T and filter length L,the variable step size search method was proposed to optimize them. Firstly,the fault period T and filter length L of MOMEDA were selected by using multi-point kurtosis and permutation entropy to realize adaptive MOMEDA noise reduction for the original signal. Then,the CEEMDAN method was used to decompose the de-noised signal,and the signal reconstruction was carried out by selecting the intrinsic mode function（ IMF） containing rich fault information according to the weighted kurtosis（ WK） index. Finally,the reconstructed signal was analyzed by envelope spectrum and the fault feature information was extracted. The analysis results of simulated signals and measured signals show that the proposed method is able to extract the weak fault feature frequency of rolling bearings and has certain reliability.关键词：POMOMEDA;CEEMDAN;Weighted kurtosis;Rolling bearing;Feature extraction
- 4
- |
- 342
- |
- 1
发布时间：2022-09-22 - 摘要：In order to accurately diagnose the fault of rolling bearing,a wavelet base construction method based on Gaussian function is proposed. In this method,the superimposed Gaussian function is used as the initial model to construct the wavelet basis function. The coefficients of the wavelet basis function are determined by fitting the initial model with the vibration signal of rolling bearing. Through the analysis of fault signals of outer ring,inner ring and rolling element of 6205 rolling bearing,the results show that the new wavelet basis can effectively suppress the noise component in the signal,extract fault features,and realize accurate fault diagnosis of rolling bearing. Under the same decomposition conditions,the new wavelet basis can diagnose the running state of rolling bearing more accurately than Gaussian wavelet,so it has higher application value.关键词：Gauss function;Rolling bearing;Wavelet basis;Data fitting
- 5
- |
- 292
- |
- 2
发布时间：2022-09-22 - 摘要：The blade surface of milling-formed aero-engine blisk is a free-form surface with large curvature variation,which seriously restricts the uniformity of polished surface. In order to master the influence rule of the flexible polishing technological parameters for abrasive cloth wheel on materials cutting depth,the single factor polishing experiment of TC4 specimen was carried out based on the polishing technological equipment of “NC machine + flexible grinding head + elastic grinding tool（ abrasive cloth wheel） ”,the process parameters influence on materials cutting depth was analyzed,and the materials cutting depth prediction model was established by orthogonal test,the results show that the cutting depth is the most sensitive to the amount of compression,the more sensitive to the rotational speed,the less sensitive to the feed speed and the less sensitive to abrasive size. Finally,the polishing experiment was carried out,it’s results show that the measured contour is consistent with the predicted contour,and the prediction model is reliable and can be used to predict the materials cutting depth.关键词：Flexible polishing;Abrasive cloth wheel;Cutting depth;Technological parameters;Influence law
- 5
- |
- 91
- |
- 0
发布时间：2022-09-22 - 摘要：For the impact of underground pressure,the roadway support equipment has poor anti-shock capability and is vulnerable to impact failure. A variable gradient thin-walled cylinder energy-absorbing and anti-shock component for anti-shock bracket is proposed. Design of different wall thickness difference and number of segments of variable gradient thin-walled cylinder energy absorbing members,The impact-crushing experiment of each parameter variable-gradient thin-walled circular tube was carried out,and the relevant energy-absorbing and anti-shock performance parameters were analyzed. The results show that the increase of the number of segments and the difference in thickness of the thin-walled circular pipe members will reduce the initial wall thickness of the thin-walled pipe,and reduce the initial peak force. Under the same average wall thickness,the average supporting reaction force and total energy absorption of the variable gradient thin-walled tubes with different wall thickness differences and number of segments are higher than ordinary thin-walled tubes by 9. 3% ～ 178%. In the variable-thickness thinwalled circular tubes with different parameters,the initial peak force,the absorbed energy,the average supporting force and the supporting force fluctuation performance parameters of the variable-gradient thin-walled circular tube members with four sections and thickness difference of 0. 5 mm are superior,which is ZQ3300 anti-shock bracket ideal anti-shock energy absorbing member,The design of the variable-gradient thin-walled circular pipe member can change the position and quantity of the plastic hinge formed by the ordinary thin-walled circular pipe member,so that the deformation of the thin-walled member tends to be more stable in the diamond mode and the mixed mode,and the energy absorption and anti-shock ability is improved.关键词：Rock burst;Anti-impact hydraulic support;Energy absorbing components;Energy absorbing and scouring performance
- 5
- |
- 180
- |
- 0
发布时间：2022-09-22 - 摘要：The smooth specimens,notched specimens and impact crater specimens of ZM6 material were prepared. The fatigue test of these specimens was carried out,and the fatigue life of these specimens under different stress levels was obtained.Based on the theory of continuum damage mechanics,a new multi-axial fatigue damage evolution model is proposed to describe the fatigue damage of local material with impact pits. ABAQUS was used to simulate the formation process of the impact pit crater,and the geometry of the pit crater and the local residual stress-strain field were obtained. By using the ABAQUS subroutine USDFLD,the material constitution and damage evolution were coupled,so as to realize the calculation of the fatigue life of the structure with impact pit crater. The results shows that the predicted median life was consistent with the test median life,and the error was within twice the error band,white meet the requirements of the engineering application.关键词：ZM6;Impact pit;Fatigue life;Continuum damage mechanics;Residual stress
- 3
- |
- 165
- |
- 0
发布时间：2022-09-22 - 摘要：The finite probability information refers to the incomplete probability information,which caused that the reliability indexes of the product cannot be accurately calculated based on the existing information. The paper,using reliability design theory and sensitivity analysis method,set rated pressure as threshold value,established the reliability design model of hydraulic pipeline with finite probability information,and deduced the matrix formula of reliability and reliability sensitivity of hydraulic pipeline,carried on the reliability and reliability differential sensitivity analysis methods with finite probability information of hydraulic pipeline,determine the reliability differential sensitivity of hydraulic pipeline by simulation,and put forward the changing rule of reliability and reliability sensitivity with respect to the parameters. The results indicated that the influence of design parameters change for the reliability of hydraulic pipeline. At the same time,it assists to solve the reliability engineering problems of Hydraulic pipeline under fluctuation impact environment. It realizes the reliability sensitivity of the Hydraulic pipeline under hydraulic surge impact environment through a computer program.关键词：Hydraulic pipeline;Rated hydraulic pressure;Finite probability information;Hydraulic fluctuation impact;Reliability differential sensitivity
- 6
- |
- 107
- |
- 0
发布时间：2022-09-22 - 摘要：Triangular track wheels of emergency rescue vehicles need high mobility and reliability under various terrain conditions. Aiming at overlong time of multi-working fatigue optimization calculation,ensemble of surrogate model is used to accelerate the optimization solution. In order to ensure convergence accuracy,a new evaluation index of surrogate model is proposed. First of all,fatigue life of support frame of replaceable triangular track wheel under four working conditions is analyzed.Then,based on Kriging model and response surface model,ensemble of surrogate model is constructed for mass and fatigue life.In order to approach global optimal point more easily,ensure same concavity and convexity between predicted value and observed value,local trend deviation is proposed as evaluation criterion of constructing ensemble model. Finally,size optimization of support frame is constructed. Results show ensemble of surrogate model not only ensures calculation accuracy,but also has robustness. Fatigue life of triangular track wheel after lightweight design is increased by 43. 59%.关键词：Triangular track wheel;Multi-working size optimization;Ensemble of surrogate model;Fatigue life;Local trend deviation
- 3
- |
- 218
- |
- 1
发布时间：2022-09-22 - 摘要：To solve the multi-objective optimization problem of functionally graded plates with cutouts,a method integrating extended isogeometric analysis（ XIGA） and material distribution variation is proposed. For the mechanical calculation of functionally graded plates with cutouts,the third-order shear deformation theory is introduced,and the extended geometric analysis is adopted. To improve the numerical accuracy,the quadtree adaptive gauss integral is used in the hole boundary region.The B-spline function is used to replace the traditional functional grade material distribution function in the description of material properties. In the optimization process,the control points describing material distribution are taken as design variables to establish multi-objective optimization problems with the largest first natural frequency,the smallest plate mass and the largest buckling critical parameters. The NSGA-II algorithm is selected as the optimization algorithm. The effectiveness of the proposed algorithm is demonstrated by some examples in this paper.关键词：Extended isogeometric analysis;Functionally grade plates;Cutouts;Multi-objective optimiztion;Material distribution;Third-order shear deformation theory
- 5
- |
- 140
- |
- 0
发布时间：2022-09-22 - 摘要：To provide a basis for selecting formulas or extending their applied ranges,applying probability theory and mathematical statistics,a comparison and evaluation method of formula stability and precision was established. Based on the study that the ratio of actual burst pressure to the formula calculated value was basically in accordance with the normal distribution random variables, comparing and evaluation the formula stability from the variation coefficient of distribution parameters fluctuation range,comparing and evaluation the formula precision from the distribution parameters value interval contact ratio.When the bilateral confidence was 98% and in the applied range of the formula,the stability and precision of Mid-diameter formula,Tresca formula,Faupel formula and Rheological stress formula were compared and evaluated. The researching results shown that:（ 1） It is the basic conditions for selecting formulas or extending their applied ranges that stability and precision not reduced.（ 2） For pressure-bearing single-layer cylinder,the applied range of the Mid-diameter formula for measured burst pressure specified by the standard,it can be extended from no more than 105 MPa to no more than 329. 6 MPa,the stability of the Mid-diameter formula is obviously improved and the precision is not reduced. The applied range of the Tresca formula for measured burst pressure specified by the standard,it can be extended from between 91. 0 MPa and 300 MPa to no more than329. 6 MPa,the stability of the Tresca formula is obviously improved and the precision is not reduced. If the measured burst pressure was not exceed 329. 6 MPa,the stability and precision is no significant difference between the Mid-diameter formula and the Tresca formula. When the applied range of the Rheological stress formula for measured burst pressure was not less than 220 MPa,and the applied range of the Faupel formula for measured burst pressure was not less than 250 MPa,the precision of the two formulas is not significantly different,and the stability of Rheological stress formula is obviously better than Faupel formula.For Mid-diameter or Tresca formula with measured burst pressure not exceeding 329. 6 MPa,and for Rheological stress formula with measured burst pressure not less than 220 MPa,the stability of Mid-diameter or Tresca formula is obviously better than the Rheological stress formula,and the precision is higher than the Rheological stress formula.（ 3） For flat steel ribbon wound pressure vessel with measured burst pressure was not exceed 209. 7 MPa,the precision and stability of Mid-diameter formula is lower than that of four predictor formulas of burst pressure for pressure-bearing single-layer cylinder.关键词：Pressure-bearing cylinder;Burst strength;Predictor formula;Precision and stability
- 3
- |
- 97
- |
- 1
发布时间：2022-09-22 - 摘要：In order to achieve lightweight and high efficient load transfer requirements an well as cost reduction in the strut design process of civil aircraft. In this paper,it firstly combines engineering theoretical formulas to develop a calculation program using Python,and then integrates the program into Isight platform. It utilizes multi-island genetic algorithm for optimization analysis,and an iterative optimization process for the follow-up strut analysis is established. In the case of most severe local load during axial compression,considering the actual failure model of the strut,the minimum weight of strut is taken as optimization object and the margin of safety is introduced as constraint condition,then the optimization of cross-section geometry characteristic parameters of typical strut for a certain aircraft type are carried out. Under the condition that load bearing capacity requirement and the minimum weight of strut are both met,an optimized set of cross-section geometric parameters of strut is obtained,and to achieve weight reduction of the strut by 20. 4%,which could provide a guidance for the structural weight loss design of the cabin.关键词：Cabin strut;Optimization design;Failure mode;Margin of safety;Structural weight loss
- 4
- |
- 332
- |
- 2
发布时间：2022-09-22 - 摘要：In order to effectively solve the motor dysfunction of lower limbs caused by spinal injury,brain injury,cerebrovascular disease and orthopaedic surgery, a multi-purpose detachable exoskeleton design scheme for lower limb rehabilitation was proposed. A high integrated force-assisted joint with force-sensing based on torque sensor was designed. Based on the design of generic size structure of legs,a two-way synchronous fast adjusting mechanism with threaded transmission was proposed to realize the function of fast adjusting the length of exoskeleton leg with one hand. Considering the movement balance safety and wide applicability of exoskeleton,the lower limb rehabilitation exoskeleton was combined with the liftable mobile protector organically. The whole structure of the lower limb rehabilitation exoskeleton and the liftable mobile protector frame were put forward,which ensured the balance safety in the process of exoskeleton movement,and was also suitable for the patients with different degrees of lower limb movement dysfunction,such as mild,moderate and severe patients with dysfunction. In order to rationally plan the gait of lower limb rehabilitation exoskeleton movement,gait data of leveling,ascending,descending,ascending and descending stairs was collected and processed. The control system was established. In order to verify the theoretical research results, a experimental prototype was processed, and relevant experimental verifications were carried out. The experimental results show that the torque sensor has high real-time and accuracy,and the exoskeleton has a wide range of adaptability. Combined with the mobile protector frame,it can provide an effective weight reduction for patients. The exoskeleton can achieve the functions of standing up,sitting down,walking on the ground,climbing and descending the slope and stairs.关键词：Integrated force-assisted joint;Exoskeleton;The liftable mobile protector;Gait;Control system;Experimental verification
- 10
- |
- 564
- |
- 0
发布时间：2022-09-22 - 摘要：Based on the background of frequent cracking failures of the cab floor of a light commercial truck,the cause analysis and optimization designs of the strength of the cab floor of this brand commercial vehicle were carried out. First,the CAE modeling and simulation of the light truck floor cab were carried out,and the time domain data onto the strain of each measuring point of the road driving of the light commercial truck was measured using the electrical measurement method. The calculation results show that the stress extreme value of the CAE calculation simulation results reaches 160. 7 MPa,and the stress extreme value of the same part measured by the electrical measurement method reaches 250. 3 MPa,which is far beyond the yield strength limit of the cab material. Then,on this basis,the nature of the problem is judged,and the force analysis and calculation are carried out on the turning mechanism. The calculation results show that the theoretical difference between the torque limits of both sides is only 3 424. 2 N·m,and the reason for the crack is that the strength of the cab body is too low. Finally,on the basis of experiments and theoretical analysis,this paper proposes two structural strength optimization measures,including strengthening plates and welding seams,and adding structural adhesive,and conducts comparative analysis in various aspects to provide a reference for the subsequent engineering structure optimization and strength analysis.关键词：Cab;Electrical measurement method;CAE;Stress
- 4
- |
- 94
- |
- 1
发布时间：2022-09-22 - 摘要：In view of the insufficient strength,vibration deformation and fracture of the sley system of the beating-up mechanism in the existing loom,the structure of the sley system is optimized. According to the finite element modal calculation theory,the vibration equation of the new multi-degree-of-freedom sley foot system is established. The modal and mode of the sley foot are analyzed in ANSYS. The rigid-flexible coupling model of the new beating-up mechanism is established in ADAMS,and the flexible dynamic simulation and stress analysis are carried out. The results show that the new sley system is easy to manufacture and install,and can meet the requirement of mechanical properties of beating-up motion. The possibility of resonance deformation of the new sley is very small. The beating-up acceleration curve of the flexible sley foot fluctuate more than that of the rigid body,and the change of the loom speed have a great influence on the acceleration of the beating-up mechanism. The stress distribution of the main body of the new sley is less than that of the original sley.关键词：Rapier loom;Beating-up mechanism;Modal analysis;Rigid-flexible coupling;Adams Simulation;Stress analysis
- 4
- |
- 154
- |
- 0
发布时间：2022-09-22 - 摘要：In order to solve the problem that the MEMS accelerometer used the external ballistic information measurement cannot withstand the high overload during projectile launching and is easy to cause damage to the device,a low-range capacitive accelerometer with high overloading resistance was designed. Platforms modeled on the bridge fender structure were placed at the end of the beam where the stress was relatively large and easy to be broken by impact. The structure can absorb a part of the energy during an impact with its own deformation,thereby reducing the deformation of the sensor itself. The finite element simulation results indicated that the stress of the proposed accelerometer under the condition of 30 000 g overload was reduced from 994. 88 MPa to 70 MPa. Therefore,the possibility of device damage and fracture was greatly reduced,which meets the design expectations of improving the sensor’s anti-overload capability.关键词：Low range;Anti-overload;Accelerometer;Protective structure;Micro-electro-mechanical systems（MEMS）
- 4
- |
- 179
- |
- 0
发布时间：2022-09-22 - 摘要：In order to prolong the service life of the swing check valve and reduce the energy loss,by establishing the valve flap motion model,combined with the structural dynamics model,using the analysis module of Fluent and ANSYS/LS-DYNA finite element software,the valve flap movement and impact collision during the valve closing process were simulated and analyzed. Through analysis,it was shown that the fluid backflow has a hysteresis,the movement speed of the valve flap shows a parabolic rise,and the dynamic torque presents a process of slowly decreasing to suddenly increasing in the reverse direction when the valve is closing. Vortex phenomenon obvious occurs at the bottom of the valve flap,and there is a time difference in the change of fluid flow direction on the center line of the flow channel; In the process of collision and rebound,the peak stress appeared at the rounded corners of the back of the flap and the rocker rib,and the valve flap swings slightly and collides with the valve seat many times in a short time. The study results provided a reference for the design and optimization of the structural parameters of the valve.关键词：Swing check valve;Flap motion;Impact collision;Ansys/LS-DYNA;Dynamic simulation analysis
- 3
- |
- 155
- |
- 1
发布时间：2022-09-22 - 摘要：Thermoplastic composites have excellent comprehensive mechanical properties and widely applied prospects. A static model was established and elastic-plastic characteristics were analyzed for a plane curved beam,which was made of thermoplastic composites and subjected to bending. Based on the single parameter plastic modal,the associated flow rules and the linear strain hardening law,the governing equations of curved beams were derived according to the basic equations of plane stress problem in polar coordinates. The analytical solutions of stress and displacement were then obtained. The influence of geometrical size on stress distribution at the cross-section of the curved beam was analyzed. Also,the failure mode of the curved beam was judged in virtue of the Hashin failure criterion. The results demonstrate the efficiency of the proposed model for elastic-plastic characteristics analysis of thermoplastic composite curved beams subjected to bending. And the failure mode of curved beams is associated with the radius-thickness ratio.关键词：Thermoplastic composites;Plane curved beam;elastic-plastic;The single parameter plastic modal;Hashin failure criterion;Radius-thickness ratio
- 3
- |
- 159
- |
- 0
发布时间：2022-09-22 - 摘要：The residual stress of structural parts of welding machine tools at home and abroad was investigated. The welding bed,column and sliding saddle used in a vertical machining center were manufactured. And the tracking measurement of residual stress and deformation after welding and combined aging treatment were carried out. The results indicated that a large residual stress existed in the structural parts of welding machine tools which was over than 100 MPa. After welded,the maximum initial residual stress of the column,bed and sliding saddle reached 154. 9 MPa,274. 4 MPa and 300. 6 MPa,respectively. The maximum residual stress of the column guide rail,sliding saddle and bed respectively reached 1. 22 mm,2. 24 mm and 2. 88 mm,which approaching or exceeding yield strength of materials so that easily caused large deformation. Through the combined aging treatment of “post-welding-thermal aging-semi-finishing-vibration aging-finishing ”,the stress and deformation of the welding bed,sliding saddle and column are significantly reduced,the maximum residual stress respectively is reduced to 41. 9 MPa,39. 8 MPa and 18. 1 MPa,which all lower than 10%Rm,and the maximum straightness respectively is 36. 69 μm,23. 57μm and 19. 17 μm. After about six months,the deformation of the guide surface is 1 μm/1000 mm ～ 3 μm/1000 mm,which means good accuracy retention. The welding structure can be used for high precision CNC gold cutting machine tools and gear boxes.关键词：Welding lathe body;Residual stress;Precision;Aging treatment
- 2
- |
- 100
- |
- 1
发布时间：2022-09-22 - 摘要：In order to accurately predict the forming limit curve of DP780 steel sheet under the condition of warm forming,the ductile fracture prediction model was introduced into the numerical simulation. Based on the unidirectional tensile test results analysis of DP780 steel sheet in the temperature range of 573 K ～ 873 K and strain rate range of 6. 67×10-4 s-1～ 6. 67×10-3 s-1,the warm forming performance of DP780 steel sheet is better under the condition of temperature of 673 K and strain rate of3. 33×10-3 s-1 determined by the product of strength and ductility. And through the simple tensile test and simulation under this deformation condition,determined the main factors affecting the ductile fracture of DP780 steel sheet. Thus a model for predicting tensile fracture and shear fracture of DP780 steel under different strain paths was developed,by combining it with the warm forming constitutive model and the Hill ’48 yield criterion,the finite element simulation of the rigid mold bulging test was realized,and the forming limit curve of DP780 steel sheet at the temperature of 673 K was predicted,The mathematical model of forming limit was established. The results show that the forming limit results predicted by this method have better precision.关键词：Advanced high strength duplex steel;Forming limit;Prediction model of ductile fracture;Finite element analysis;Warm bulging
- 3
- |
- 198
- |
- 0
发布时间：2022-09-22 - 摘要：The research work was carried out on the mechanical performance testing and characterization of an engine cylinder head material,and the prediction of the cylinder head thermal engine fatigue life. The fluid-solid coupling method was used to obtain accurate results of the thermal boundary and temperature field of the cylinder head. The calculated temperature field is consistent with the measured results. According to the thermal shock test specifications of the whole machine,the Sehitoglu model was used to predict the thermal fatigue life of the cylinder head. The simulation results show that the minimum life of the cylinder head occurs in the nose bridge area on the exhaust side of the second cylinder fire surface,which is mainly caused by environmental damage. The service life is 6 860,which meets the design requirements. At the same time,the cylinder head has successfully passed the heat engine fatigue bench test of the whole machine.关键词：Internal combustion engine;Cylinder head;Thermal mechanical fatigue;Life prediction
- 2
- |
- 187
- |
- 1
发布时间：2022-09-22 - 摘要：The three-dimensional finite element model of the pantograph was established by the finite element software,and the propagation characteristics of fatigue crack at the end of the upper frame for the pantograph were studied by the fracture analysis software Franc3 D. The fatigue crack propagation life under normal temperature,atmospheric environment and corrosion environment were predicted. The results show that when a 2 mm surface crack has been produced at the end of pantograph upper frame,it will penetrate the pipe wall when it continues to expand to a surface length of about 15 mm. For normal temperature and atmospheric environment,the operation mileage of fatigue crack extension from 2 mm surface crack to 50 mm through crack is about 240 000 km. In the corrosive environment,the operation mileage of surface cracks extension to the same length is about31 900 km.关键词：Pantograph;Fatigue;Crack;Propagation;Life;Corrosion environment
- 6
- |
- 238
- |
- 1
发布时间：2022-09-22 - 摘要：In order to effectively evaluate the fatigue life of a light bus body structure,the multi-body dynamics body model was built with ADAMS,the accuracy of the model was validated by calibration with measurement data. Based on measured road load data,with comprehensive application of virtual iteration and fatigue life analysis methodology,the acceleration,displacement and force response signal which acquired at proving ground were reproduced,the internal forces between body and suspension were extracted,the fatigue life of body was calculated. The rounded corner of back row seat bracket reinforcing rib exists fatigue failure risk,which is consistent with failure result of road durability test. With improvement of material trademark,the body structure was ultimately passed the durability validation of proving ground,which has shown that the engineering practicability of this methodology. The practice has proved that the combination of virtual iteration and fatigue life analysis can effectively support the fatigue life evaluation of body structure,which has reasonable engineering reference value.关键词：Multi-body dynamics;Measured road load data;Virtual iteration;Fatigue life analysis
- 6
- |
- 254
- |
- 0
发布时间：2022-09-22 - 摘要：The fracture reason analysis of oscillator wire was performed of vertical log-periodic antenna,which mounted somewhere in the north of China in 2018. Through the analysis of two possibilities of brass material fracture,the results show the reason of brass oscillator wire fracture is fatigue damage. The main causes of fatigue damage are the tension adjustment of the antenna cable and the large local temperature difference,which results in the stress of the oscillator wire far exceeding the original design stress. According to the reason breakage of the brass oscillator wire,an improved scheme is proposed to meet the antenna requirements in this area.关键词：Vertical log-periodic antenna;Cable;Brass oscillator wire;Fracture analysis;Fatigue damage
- 5
- |
- 58
- |
- 0
发布时间：2022-09-22 - 摘要：Based on the extended finite element method（ XFEM）,the dynamic propagation behaviors of interface cracks and sub interface cracks in bimaterials are studied. A dynamic growth analysis model of bimaterial plate with interface crack and sub interface crack is established. In this model,the centralized mass matrix is used to replace the traditional consistent mass matrix to improve the efficiency,and the Newmark method is used for time integration. This model is compared with the dynamic response and energy value calculated by the two-dimensional elastic model established in the finite element software. Through numerical examples,the effects of strain rate and material properties on the interface and sub interface crack growth in circular and linear bimaterials are studied.关键词：Dynamic propagation;Interface crack;Subinterface crack;Propagation finite element method
- 3
- |
- 242
- |
- 1
发布时间：2022-09-22 - 摘要：The actual tooth surface is hardly obtained utilizing the existing simulation machining method. Therefore,a highprecision simulation machining method for gear shaping is proposed. Based on the CATIA platform,the spatial motion relationship between the cutter and the gear blank is analyzed by establishing the model of the cutter and the gear blank. The high-precision insertion of the cylindrical spur gear is completed considering the commands of CATIA translation,rotation,Boolean operation and secondary development functions. The tooth surface accuracy is confirmed with the actual processing parameters by measuring the normal distance between the standard involute and the tooth surface of the simulation model. Finally,the simulation model is reconstructed. The simulation model and the reconstruction model are separately solved by finite element. By comparing the simulation model and the reconstruction model solution results,the effectiveness of the simulation model obtained by this method is verified.关键词：Cylindrical spur gear;Simulation machining;Gear shaping;High-precision meshes
- 2
- |
- 277
- |
- 1
发布时间：2022-09-22 - 摘要：The transmission characteristics of the precision RV reducer is mainly determined by the mesh state between the cycloid gear and pin shell parts,and vibration modal characteristics of the cycloid gear have important effects on the dynamic characteristics of the whole reducer. Based on the 3 D model of the RV reducer,the vibration modal characteristics of the cycloid gear considering three states,namely the free,bearing support and mesh states,are obtained using the finite element method.Simulation results show that the modal characteristics of the cycloid gear in the meshing state matches better with the working mode of the RV reducer than the other states,The natural frequencies the cycloid gear increase remarkably,and the vibration modes are changed accordingly. These works are useful for the analysis on the dynamic transmission characteristics of the RV reducer.关键词：RV reducer;Cycloid gear;Mesh state;Modal analysis;Finite element method
- 5
- |
- 312
- |
- 3
发布时间：2022-09-22 - 摘要：In order to analyze surface crack effects on SRM grain structural integrity,the-50℃ ignition test was conducted for the SRM with preseted inner surface crack which was 0. 6 mm in depth. At the same time cracks with various depths in the SRM grain were preseted firstly. Then J integral of cracks was respectively calculated based on finite element method. With the engineering case analysis,fracture toughness and the ultimate value of J resistance were obtained under-50℃ ignition test. The results show that the structural integrity of grain was even worse under such conditions,which means the surface cracks growing easily,but the cracks could arrest when reached the shell.关键词：Solid rocket motor;Grain;Ignition;Crack;J integral
- 3
- |
- 158
- |
- 3
发布时间：2022-09-22 -
SIMULATION AND ANALYSIS OF TIPOVER STABILITY OF WHEELED MOBILE MULTI-ROBOT COORDINATED TOWING SYSTEM
摘要：In the process of mobile multi-robot coordinated towing,the mobile robot will cause a series of problems such as system damage,operation failure,and casualties due to its overturning. First,the system is divided into two parts: the mobile manipulator and the towing system. The kinematics models are established respectively. The Lagrangian method and the NewtonEuler method are used to establish the two parts of the dynamic model. The numerical method is used to solve the inverse kinematics of the system,and then to analyze the stability of the system based on the force-angle stability measure. Finally,Matlab software is used to compare the stability angles corresponding to the inverse kinematics of each group of manipulator to obtain a set of most excellent solution. The result lays the foundation for the further study of system motion stability,trajectory planning and system control.关键词：Mobile manipulator;Multi-robot system;Towing system;Inverse kinematics solution;Stability analysis- 5
- |
- 175
- |
- 0
发布时间：2022-09-22 - 摘要：In order to improve the service life of rubber joints of standard subway gearbox boom,the causes of fatigue failure of rubber joints are analyzed,the characteristics of different structures of rubber joints are studied,a new rubber joint with oblique linear rubber free surface and rubber thickness gradient is designed,the friction amplitude and stress concentration of rubber free surface are reduced,and by using finite element analysis software,the fatigue resistance of the new structure is optimized to improve by optimizing the fatigue resistance of the new structure using FEA software,the structural design defects are improved and the service life of the product is increased.关键词：Fatigue optimization;Rubber joints;Structural design
- 4
- |
- 95
- |
- 0
发布时间：2022-09-22 - 摘要：It is very important to determine the reasonable shutdown stress of air-conditioning piping,and it is related to the piping reliability and development cost. Firstly,the piping shutdown stress was studied through a large number of stress tests and statistical analysis methods. Then the piping shutdown fatigue life was calculated based on the force number and S-N fatigue life curve. Finally,the fatigue acceleration tests of pipe fitting under single part and complete machine assembly are carried out respectively. The results show that: The piping will be subjected to 2 ～ 3 stress shocks at the shutdown moment,the average number of shocks is 2. 6 times; The first impact stress is the largest,and the subsequent impact stress attenuates slightly;Vibration table and counterweight block can be used to generate stable stress impact,which can reach millions of times in a short time,and the component fatigue can be verified quickly; Piping bending will reduce the piping fatigue life,the operating pressure and temperature have little influence on pipe fatigue life,welding has little influence on piping,since there is a distance between the welded part and the bent part; In order to ensure the piping reliability under the limit state,the piping shutdown stress should be below 62 MPa.关键词：Air conditioning piping;Shutdown stress;Fatigue life;Limit value
- 3
- |
- 86
- |
- 1
发布时间：2022-09-22 - 摘要：A method of simply wind turbine time history loads have been studied in the article,it can be converted the time history loads into some number of load duration distribution. It is based on the standard of ISO6336 by considering 6 degrees of freedom. The loads gotten by this method can be used to the designing loads of the wind gearbox by inputting it to the currently commercial gearbox designing software to calculated the system deformation. A comparison between the calculated loads spectrum and the torque spectrum provided by wind turbine factory have performed based on gear strength,the results presented slightly difference,but the calculating time decreased a lot. The method provided a preference to the wind gearbox manufacturer and other gearbox manufacturer process and program the design loads,and have some values of practical applications.关键词：Wind gearbox;Time history loads;Load processing;Load duration distribution
- 5
- |
- 130
- |
- 0
发布时间：2022-09-22 - 摘要：In order to consider both material damage of the crack tip and the initial fracture toughness,a corrected cohesive zone model（ CZM） that considers the influence of material damage of the initial crack propagation has been proposed. The corrected cohesive zone mode obtained from the end notch flexure（ ENF） test has been implemented in the ABAQUS/Standard.The results show that it is necessary to consider both material damage of the crack tip and the initial fracture toughness,and the corrected cohesive zone mode can accurately simulate the crack propagation.关键词：Composite;Cohesive zone mode;Crack propagation;FEM
- 4
- |
- 314
- |
- 2
发布时间：2022-09-22 -
RESEARCH AND VERIFICATION OF CONTACT STRESS CALCULATION METHOD FOR FIVE-BALL FATIGUE TESTING MACHINE
摘要：To accurately calculate the contact stress of the five-ball fatigue testing machine tooling,the tooling design contact angle is determined by the geometric size relationship. According to the load deformation relationship and the formula derived,the balance equation is established between the external load and the working contact angle. The equation is solved using the iteration method. The working contact angle under load is calculated,and the tooling contact stress is obtained. For the actual size of the 9. 525 mm diameter steel ball tooling,the contact stress comparative analysis is calculated by the numerical algorithm and finite element method respectively. The calculation result deviation is less than 2%. It shows the contact stress numerical algorithm is reliable,it can be used for the test protocol formulation and provide guidance for the test tooling design.关键词：Five-ball fatigue testing machine;Contact stress;Working contact angle;Finite element method;Reliable- 3
- |
- 52
- |
- 0
发布时间：2022-09-22
- Technical support is provided by Beijing Founder electronics co., LTD 豫ICP备05013835号-4
京公网安备11010802024621 - It is recommended to read the content of this site in Chrome&IE9+. Please switch to extreme mode in browser 360.
- Cookies We use cookies to help provide and enhance our service and tailor content. By continuing, you agree to the use of cookies.
0