最新刊期
期 1 ， 2019
- 摘要：Most studies on the vibration of variable density paper web are limited to the discussion of small deflection linear problems. There are few researches on nonlinear vibration problems with large deflection in variable density printing web.However,in practice,the density of the web is varied due to the difference in the distribution of the printed image. In this paper,the nonlinear vibration characteristics of moving printing web with variable density are studied. Based on the von Karman plate theory,the vibration equation of the large deflection motion of the axially moving paper is deduced. The differential equation is divided by the Bubnov-Galerkin method,and the differential equation is solved by elliptic integral method. The frequency expression of the nonlinear vibration is obtained. The influence of density coefficient,dimensionless velocity and aspect ratio on the complex frequency of large deflection vibration of moving paper under different initial conditions is analyzed. This study provides a theoretical basis for improving the stability of printing equipment.关键词：Nonlinear vibration;Variable density;Printing paper web;Bubnov-Galerkin method
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发布时间：2022-09-22 - 摘要：High damping rubber bearing（ HDRB） as a kind of isolation bearing has the functions like bearing capacity,restoring force and damping（ energy absorption）. In this paper,a regular continuous girder bridge isolated with high damping rubber bearings was taken as a research object. A simplified Two Degrees of Freedom mechanical model was established in Opensees software,and compared with the FEM model established in SAP2000 to study the feasibility and accuracy of the simplified mechanical model. The results show that the response amplitude of the isolation bridge can be accurately calculated by the simplified mechanical model. Under the same seismic waves,the analysis results obtained from the simplified mechanical model meet the engineering accuracy and agree with the FEM model.关键词：Isolated bridge;High damping rubber bearing（HDRB）;Mechanical model;Dynamic Analysis;Finiteelement simulation
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发布时间：2022-09-22 - 摘要：The layerwise/solid element method（ LW/SE） was used to study the static and free vibration problems of lattice sandwich structure under different boundary conditions. First,the layerwise theory was used to analyze the behavior of the shell of composite face sheets,and the three-dimensional solid elements were employed to obtain the governing equations of the core. And then,based on the governing equations of the face sheets and core,the finial governing equation of sandwich structure was assembled by using the compatibility conditions,which was used to ensure the compatibility of displacements at the interface between face sheets and core. The numerical results of the proposed method were compared with those obtained from the 3 D elastic model developed in finite element software,and good agreements are achieved. Furthermore,a series of numerical analyses are conducted to further explore the effects of the thickness of the face sheets on the static responses and free vibration responses of composite lattice sandwich structures.关键词：Pyramidal lattice sandwich structure;Static analysis;Free vibration analysis;Layerwise/solid element method
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发布时间：2022-09-22 - 摘要：According to shearer vibration problems in the practical work,using multi-body dynamics theory,considering the connection characteristics between walking unit of shearer and scraper conveyor,the support characteristics of adjustment height oil vat,the stiffness of rocker arm of shearer,the connection characteristics between the parts of shearer,vibration angle of shearer,6 degrees of freedom dynamic model in the vertical direction of shearer was established.The vertical direction of shearer drum load was used as an external excitation,and the effect of different coal and rock hardness on vertical direction vibration characteristics of shearer were solved by using numerical analysis method. The results show that the mean of coal cutting impedance has great influence on vibration displacement of front and rear cutting unit when the range is 200 kN/m ～ 400 kN/m,the displacement range of front and rear drum is 13. 42 mm ～ 26. 83 mm、8. 19 mm ～ 16. 37 mm,and the displacement range of front and rear rocker arm is 5. 31 mm ～ 10. 62 mm、3. 32 mm ～ 6. 65 mm.Finally,the results of model is verified by experiment.关键词：Shearer;Coal and rock hardness;Vibration;Numerical analysis;Experimental study
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发布时间：2022-09-22 - 摘要：Mechanical transmission is widely used in vehicles,machine tools,construction machinery and other engineering fields,the study of mechanical transmission reliability,damage mechanism,fault diagnosis and signal processing method has great significance and value.The traditional signal processing algorithms,such as FFT algorithm,the fast Fourier transform algorithm,since its fast speed,stable spectrum analysis,has been widely used in engineering. But the signals of engineering practice are very complex,nonlinear,and non-stationary,Within the external noise interference coupled,makes the analysis and processing more difficult,which lead to the spectral analysis based on FFT method has been very limited. For the advantages of computation speed,features and stability of FFT algorithm,the secondary FFT,third FFT algorithm,n-FFT algorithm（ 2 npoints less than the signal sample points） were discussed in theory and research,the theory was explored and verified by experiment signals. It was applied in the classification study of gear signal. Analysis shows that n-FFT algorithm is fast,with high feature accumulation,is beneficial to the classify and fault monitoring and diagnosis of gear operating state.关键词：N-FFT;Compressed sensing;Sparse representation;Feature extraction;Gear system
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发布时间：2022-09-22 - 摘要：Usually satellite is under complex dynamic load during the launch phase,it’s easy to cause satellitestructure damageto influence spacecraftmission. Mechanical environment tests show that spacecraftstructure damage always occurs because of larger acceleration response of equipment such as large mass or high center of mass,and affecttedthe project development.Difference from the usual engineering solutions,a method based on gap elastic impactting is studiedto reducing damage. By constructing mechanical model,simulation and analysis has been done to a designated parameter structurepanel and equipment,results show that the methed as one of solutions of lower damage is valid to reducing defomation and load located at connection between equipment andstructure.关键词：Satellite structure;Acceleration response;Damage;Impact limitamplitude;Stimulation;Reduce damage failure
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发布时间：2022-09-22 - 摘要：In engineering practice,the non-linear vibration isolation systems are widely founded on the flexible foundation,and its application and research are seriously restricted to the analysis of vibration characteristic. First of all,basing on the hysteresis dry friction vibration isolation system which contains cubic nonlinear stiffness,a kinetic equation is derived by means of vibration separation method. Combing with the incremental harmonic balance method,the response of the system are obtained in the case that the flexible plate undergoes any order of main vibrations. Then,the formula of force transfer rate of the system is deduced basing on the fundamental harmonics term,and the influences of the parameters of the vibration isolator on the force transfer rate of the system are analyzed qualitatively according to the formula. It is found that the reduction of the stiffness coefficient,the increase of the damping coefficient and the increase of the static friction limit can effectively reduce the force transfer rate of the system. The research provides a reliable reference for the practical application of the system.关键词：Flexible foundation;Dry friction;Nonlinear vibration;Incremental harmonic balance method
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发布时间：2022-09-22 - 摘要：This paper analyses the vibration modes of a simply supported beam with vibration table. Firstly,the one dimensional vibration theory is used to acquire the beam vibration mathematical model. Following to use Bernoulli Euler beam theory to calculate the beam vibration differential equation,in addition to the beam set specific boundary constraint conditions to calculate each order modal parameters,using the Workbench beam finite element simulation analysis for the first five order natural frequency and vibration mode. In the end,the experimental modal algorithm based on Poly IIR is applied to identify the modal parameters of simply supported beam. The modal frequencies and mode shapes are obtained in this paper. It is keeping 3%about the consistency of the simulation value and experiment result,Which can subsequent beam or plate and so on EMA elastomer complex structure analysis and research to provide certain reference.关键词：Cantilever beam;One-dimensional vibration;Experimental modal;Hammering method
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发布时间：2022-09-22 - 摘要：A mixed-mode I-II fracture fixture and modified compact tensile specimen are designed to investigate mixed-mode I-II fracture behavior of FV520 B stainless steel used in centrifugal compressor impeller. The results show that this mixed-mode fracture belonged to micro-porous coalescence ductile fracture mechanism. With loading angle increasing,some dimples on the fracture surface were slightly stretched along the crack propagation direction and became shallow,which was caused by the increasing shear component of stress. As the loading angle increased,total fracture toughness increased,of which the values at loading angles of 22. 5 ° and 45 ° were 1. 8 and 4. 4 times higher than that under pure I mode,respectively,moreover,both mode I and mode II components of the total fracture toughness,and the crack initiation angle increased,which could be well predicted by using mixed-mode J integral fracture criterion. This study can provide some insight into mixed-mode fracture analysis of centrifugal compressor impeller.关键词：Mixed-mode Ⅰ-Ⅱ fracture;FV520B steel;J-integral;Fracture initial angle
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发布时间：2022-09-22 - 摘要：Selective Laser Melting（ SLM） can directly fabricate parts that are difficult or time-consuming for processing or even can not be processed in traditional way. And SLM is one of most promising addictive manufacturing techniques. The current study is mainly concentrated on statics performance,such as tensile and compression properties. However,in many cases,the dynamic performance is required. This research Based on Ti-6 Al-4 V powders as the experimental material,SLM under different post-processing pieces for the rolling contact fatigue performance study. It was found that the roughness and hardness is main factors of rolling contact fatigue performance. Polishing and heat treatment can improve the rolling contact fatigue life. Big roughness causes wear failure of the SLM-fabricated titanium alloy parts,and small roughness mainly leads to spalling failure.关键词：Selective laser melting;Ti-6Al-4V;Rolling contact fatigue;Failure analysis
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发布时间：2022-09-22 - 摘要：In order to investigate the fatigue characteristics of an airborne module under random vibration loading,the general expression of structural vibration fatigue life is derived,based on the power spectral density function,which is simplified by Gaussian three interval method,the effect of random signal clipping in vibration test on stress amplitude probability distribution is also considered. Then,we analyze the relationship between the structural vibration fatigue damage and vibration modal which can be used to obtain the dynamic response of the crucial fatigue point under the given vibration loading. Finally,the vibration fatigue life of the module is given. It is shown that the numerical results coincide well with the experimental data.关键词：Random vibration;Power spectral density;Vibration fatigue life;Gaussian three interval method;Dynamic respond;Durability test
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发布时间：2022-09-22 - 摘要：The experiments under the coupling of the multi-physics field don’t have the conditions to be carried out in the heat exchange tubes fouling test. And it’s very important to establish the accurate ultrasonic propagation model for achieving the numerical simulation of selecting the detection frequency. Based on the finite element method,the three-dimension model with different heat exchange tubes had been established under the COMSOL Multiphysics condition. The varied relationship of the ultrasonic wave propagation,the different heat exchange tubes and echo exciting frequency were discussed respectively. The characteristic frequency and echo vibration mode of multi-layer tubes were found. The results show that the relationship between different characteristics of the heat exchange tubes（ material and wall thickness） and pressure load is similar. The ultrasonic time-domain reflectometry technology to detect the thickness of the tube fouling needs to select 5 MHz echo exciting frequency at least for inhibiting the pseudo-Gibbs oscillation. The optimal detection frequency is 10 MHz,and the detection effect is the best when the thickness at 3 mm ～ 5 mm. The numerical simulation agrees with the test results,and ultrasonic detection produces an error around ±5% in examining tube fouling deposit. These results provide a basis for quantitative detecting basis to select the characteristic frequency under the different tubes.关键词：Heat exchange tube fouling;Ultrasonic echo;Characteristic frequency;Numerical simulation;Detection
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发布时间：2022-09-22 - 摘要：To study the change of grain size for the hot extrusion deformation of half shaft bushing,according to the dynamic recrystallization theory,the paper establishes the dynamic recrystallization model of material and uses the finite element analysis software Deform-3 D to study the shape of half shaft bushing in the mold work under the condition of different variation of hot extrusion deformation process of material grain size. The results show that while doing the extrusion in the shape of straight line and circular arc and spline curve with three kinds of work,the grain sizes are at different levels of detail. The circular mold material makes grain size smaller and more symmetrical. The result has important significance on the improvement of performance and quality of the sleeve.关键词：Half shaft bushing;Dynamic recrystallization;Die working belt;Grain size
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发布时间：2022-09-22 - 摘要：A mixed top-down/bottom-up hierarchical method was introduced to manufacture massively aligned nanoscale domains’ arrays by using the self-assembly of asymmetrical poly（ styrene-block-ethylene/butylene’s-block-styrene）（ SEBS）triblock copolymers. Silicon substrates of assorted microstructure that is made by AFM that machines approach is used to template the ball-shaped and high-aspect-ratio cylindrical polymer domains’ alignment. The poly domains’ regular arrays were orientated via AFM micromachining technique’s introduction as an implement for dominating triblock copolymers’ self-assembly procedure locally by using the silicon substrate’s topography. This graph epitaxial methodology is exploitable in interbred hard/soft that is condensed substance systems for a variety of applications. Furthermore,pairing bottom-up and top-down methods is a bright,and perhaps basic,bridge between the parallel self-assembly of molecules and the morphological constraint of prevailing technology.关键词：Self-assembly;Polymer;Microstructure template;AFM machining technique
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发布时间：2022-09-22 - 摘要：In order to evaluate the vehicle performance of a certain type of light bus,this paper establishes the vehicle performance evaluation system and investigates the user driving needs,user scores the performance according to the satisfaction of driving needs. Analytical hierarchy process,grey relational degree method,structure entropy weight method are proposed for determining the weights of the performance. Combining the weights with the user score,the result of vehicle performance evaluation is obtained. The evaluating results of the three methods are consistent. Compared with the other two methods,the structure entropy weight method pays most attention to the situation of the user driving needs. Thus,according to the result of the structure entropy weight method,the recommendations for improvement of light bus performance are proposed.关键词：Light bus;Driving needs;Analytical hierarchy process;Grey relational degree method;Structure entropy weight method;Vehicle performance evaluation
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发布时间：2022-09-22 - 摘要：Pursuiting cutting efficiency and surface quality during machining monocrystalline silicon can improve the quality of the wafer itself and reduce the production cost. The second-order model of variable parameter voltage,pulse on time,pulse interval,wire saw speed and process result is established by response surface method,The variance analysis shows that the model equation is significant. The improved non-dominated genetic algorithm（ NSGA-II） is used to optimize processing process,and we can get a set of non-dominated solutions. These non-dominated solutions can satisfy the needs of engineering workers under different conditions. The corresponding experimental proving the non-dominated solution is feasible.关键词：Wire electrical discharge machining;Monocrystalline silicon;Response surface method;NSGA Ⅱ
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发布时间：2022-09-22 - 摘要：Pre-strain on austenitic stainless steel was a method in order to obtain good mechanical properties,the pre-strain effect evaluation was the basis of improving the production process of the steel. Applying the theory of probability and mathematical statistics,the evaluation system of pre-strain effect was established: the pre-strain effect on the mechanical properties parameter standard deviation was evaluated,using F-distribution; the pre-strain effect on the mechanical properties parameter mean value was evaluate,using t-distribution. For example of pre-strain effect on austenitic stainless steel S30408,based on the effective tensile test data at liquid nitrogen temperature,and the bilateral confidence was 99%,the effect of 9%-prestrain on the steel was evaluated: 1) 9%-pre-strain significantly increases the yield strength of steel S30408,and the standard deviation is basically unchanged; 2) for steel S30408 tensile strength,9%-pre-strain is no effect on the mean and the standard deviation.关键词：Pre-strain;Effect evaluation;Tensile test data;Steel S30408
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发布时间：2022-09-22 - 摘要：According to the load characteristics and speed regulation characteristics of the engine,the steady-state torque model is established and the optimum power and economy curves of engine are determined. Then the engine target speed is obtained by using the economic weighting coefficient method. The power transmission system is simplified into a double rotating mass model. Through mathematical model of the whole vehicle,the physical model is established by using Simulink,and a speed ratio fuzzy control method based on the speed regulation characteristic of engine is proposed,then the starting condition,braking condition and circulating condition are simulated respectively. The simulation results show that the following effect of actual speed ratio to target speed ratio can be realized well. It shows that the speed ratio fuzzy control method based on the characteristics of engine speed regulation can be well applied to speed ratio control.关键词：Speed regulation characteristics;Fuzzy control;Continuously variable transmission（CVT）;Ratio
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发布时间：2022-09-22 - 摘要：To explore the difference of the factors influencing stress distribution for large-scale component,an automatic mechanism of acquiring stress distribution characteristics and influence knowledge was established. For the large-scale component with continuous changing geometry,a stress survey method was proposed to extract maximum stress of each sub-region for every sample. After evaluating the danger situation,some characteristic regions were determined and the characteristic stress sets were acquired. Furthermore,the influences of structural parameters for characteristic stresses and lightweight index were analyzed. By constructing knowledge reasoning model based on multi-states adjusting strategy,the main influence factors as well as their saliency under different expectations were acquired to reflect the priority of structural parameters for adjusting. Finally,the gooseneck-type boom was taken as an example,which demonstrates that the process of modeling,analysis,feature extraction and knowledge acquisition can be realized automatically and the useful knowledge can be acquired efficiently and flexibly for the intelligent optimization of large-scale component.关键词：Large-scale component;Stress survey;Characteristics stress;Influence knowledge;Automatic acquisition
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发布时间：2022-09-22 - 摘要：Based on the theory of rigid-flex coupled multi-body system dynamics,systematic research has conducted on transmission system of a coal winning machine’s cutting part. By using the software of Recur Dyn,the model was established including transmission gears,drive shaft and bearing. Considering the flexible characteristics of drive shaft,the rigid-flexible coupled model was built.Transmission system of a coal winning machine’s cutting part was simulated dynamics analysis before contact parameter setting on the parts of transmission system. The working process of shearer transmission system was described intuitively and dynamically. Results showed that 11 th gear mesh together is the biggest,11272634. 4 N.4 th. The maximum strain,measured at the axes of 4,is 0. 081. It reveals the difference of Gear meshing force curve and its frequency-domain information between Rigid-flexible coupling system and Stiff systems. Results provide a basis for optimum design of the transmission system and prediction of fatigue life.关键词：Coal winning machine;Transmission system;Contact dynamics
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发布时间：2022-09-22 - 摘要：The current structural optimization steps are the first finite element modeling,followed by optimization analysis.In order to improve the accuracy of the analysis and ensure the rationality of the structural optimization results,the finite element model needs to be verified. In this paper,finite element analysis is carried out for the left end cap of a heavy load transmission box in China. According to the finite element analysis results,the measured points are selected and the loaded is measured. The finite element model is verified by the measured load spectrum of the end cap. It is found that the dynamic load generated by the gear meshing is about 1. 1 to 2. 5 times of the static load,but the pre-finite element analysis does not take into account the effect of dynamic loading,which can lead to early failure of the end cap during service. Finally,the boundary condition of the load is modified by indirectly obtained dynamic load factor,which makes the modified finite element model more accurate. Which provides an accurate model for the later optimization design.关键词：End cap;Finite element analysis;Model validation;Dynamic load factor
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发布时间：2022-09-22 - 摘要：In order to study the nonlinear dynamic characteristics of the cutting system of the shearer with gap,a dynamic model of the gear system of the shearer cutting machine is established,and the function of meshing stiffness and damping in the model is established. The influence of the tooth clearance on the meshing force of the gears of the shearer’s drive system is studied by using the runge-Kuatt method. The results show that the gears are increased by the gears The change of the meshing force and the amplitude of the frequency multiplication of the meshing frequency. Increasing the amplitude of the tooth side increases the fluctuation range of the engaging force,causing a large impact force in the transmission process,accelerating the wear of the tooth surface,The gears are broken in gear due to overload. Improve the stability and service life of the gear train of the shearer cutting section,and reduce the torsional vibration degree and reduce the tooth clearance. This study provides a theoretical basis for the optimal design and research of gear transmission system.关键词：Shearer rocker arm;Tooth side clearance;Gear drive system;Engagement force
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发布时间：2022-09-22 - 摘要：Structure of vehicle body is designed to absorb kinetic energy,transform impact force and keep survival space during crash. Light weight design of BIWcan realize better power performance and fuel economy,decrease exhaust emission. In this paper,collision of vehicle body structure is decomposed into axial crushing and transverse bending. Thin walled structure’s ability inenergy absorption and bending resistanceis researched,which is based on high strength steel and different filling materials. After applied the research conclusion in a SUV’s body optimization,the crash simulation result shows that it improved passive safety and reduced body weight effectively.关键词：Crash worthiness;Light weight;High strength steel;Filling materials
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发布时间：2022-09-22 - 摘要：This paper studied methods to predict the tensile strength of stiffened-welded plate structure for civil aircraft welding. Based on the law of elastic modulus in the composite material mechanics,a theoretical formula is proposed to estimate the tensile strength of the aircraft welding plate structure,and through the introduction of the mechanical properties of the welded joints,out of plane moment,long truss shape,skin stress concentration four the coefficient,reflecting the influence of factors on the strength of the welded plate structure. The results show that the theoretical calculation is 3. 81% larger than the experimental value,and the error is small,which proves that the theoretical formula established by this study has certain reliability and correctness. The estimation method can provide a reference for the selection of stiffened-welded plate structure material,the improvement of process performance and the aerospace designers ’ estimated strength value of aircraft stiffened-welded plate structure. In addition,the tensile mechanical behaviors of two groups of welding plate with different welding states were simulated and analyzed by using the finite element method. The results show that the cracking state of the weld has no great influence on the tensile strength of the stiffened-welded plate,and through the finite element stress cloud can be observed in the welding plate of the high stress area,showing the failure process,in the future for the new civil welding wall structure design and selection of preresearch stage. The finite element simulation is used to replace the tensile test of large structural members of aircraft siding,reduce the cycle and cost of pre-research,and improve the efficiency of the test.关键词：Civil aircraft structure;Tensile strength estimation;Stiffened Welded Plate;Finite element analysis
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发布时间：2022-09-22 - 摘要：A finite element model including piston,connecting rod,cylinder liner etc.,has been established,which simulates the piston loading characteristics during its working process to the greatest extent. A coupled thermo mechanical analysis of the piston was presented in the paper. It creates an analytical and numerical model of the oil film and the contact pressure in the contact surfaces between piston and piston pin,piston pin and bush,piston skirt and cylinder liner. Moreover dynamic load and acceleration of the piston and con-rod are calculated at different crank angle using corresponding full engine dynamic model with a commercial software. Engineering application shows that the above analytical model is feasible and reliable,and the results agree with that of the corresponding experiment. The established analytical model can accurately reflect the real stress status of the piston pretty well during its working process. It is able to assess and evaluate the piston skirt pressure,stress and fatigue life of the concerned areas quantitatively. As a conclusion, it provides basic data for the optimization design of engine piston.关键词：Piston;Oil film;Thermal mechanical stress;Contact pressure;Fatigue
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发布时间：2022-09-22 - 摘要：The creep test of high pressure steam pipe of a thermal power plant was carried out at 566 degree by using SPT technology. The deflection curve with time under different stress levels was obtained. In order to obtain the steady-state creep characteristics of the material,the Chakrabarty model and inverse finite element method on small punch creep test results were analyzed,obtained the material parameters of A and n in Norton equation. At the same time,the material parameters of uniaxial creep test and small punch test analysis of the comparative analysis results show that the small punch creep test results and uniaxial creep test results are consistent with each other,but different methods of analysis results of different accuracy.关键词：Small punch test;Creep property;Norton equation;Membrane stretch model;Inverse finite element analysis
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发布时间：2022-09-22 - 摘要：The article has done some research on multiaxial low cycle fatigue life evaluation methods at home and abroad,summarized multiaxial low cycle fatigue life prediction models based on Critical-Plane method and strain path and analyzed the advantages and disadvantages compared with models and applicability. It has been shown that most of the empirical prediction methods could suitable for only one or few materials so far. When they are applied on other materials,the results are usually disappointing. Meanwhile,the multi-axial fatigue failure of materials are very complicated. The current massive research work was mainly done under constant temperature and load while the studies carried out on high temperature,varying temperature and load are few. If taking notch effect,size effect,surface roughness,residual stress into account,the situation would be even more complicated. Current research on multi axis fatigue is interested in establishing life prediction model,To carry out related fatigue test,Little in-depth study of its micro mechanism The multi-axial fatigue is still a problem needing further studies.关键词：Multi axis;Low cycle fatigue life;Prediction models;Critical-plane;Strain path
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发布时间：2022-09-22 - 摘要：Based on fracture mechanics theory,the calculation formula of shaft with oblique crack under six loads,including axial force,moment and torque etc. along the main coordinate axis,was deduced at arbitrary inclination angles. The relationships between the stiffness and some parameters,including the crack inclination,the crack depth and the slenderness ratio etc. were discussed in a static and fully open crack. The calculation results show that the stiffness of the slant crack is increased with the decrease of crack inclination; And the stiffness of the oblique crack increases with the increase of the slenderness ratio; When the crack depth is small,the stiffness is changed slowly,But when the crack depth is greater than half the shaft radius,the impact of full loads should be considered,Meanwhile partial crack coupling stiffness is calculated,and coupling vibration affects the rotor’s dynamic performance.关键词：Rotor;Slant crack;Stiffness;Fracture mechanics;Strain energy density function
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发布时间：2022-09-22 - 摘要：Rotor blades are one of the most important parts of helicopter,and its can be used as lifting surface,pulling surface and control surface in flight. The fatigue life evaluation of rotor blades is the very important problem in helicopter engineering development. The history on fatigue life evaluation for helicopter composite blades is simple reviewed in this paper.Then,the main methods of fatigue life evaluation for composite blades are introduced in detail,including to damage tolerance method,flaw tolerance method and its flow chart,practical application,key problems etc. Furthermore,aim to the practical engineering application,existing problems in the three methods are analysed in-depth. Next,the unconventionality fatigue life evaluation methods are introduced,including to residual strength method,progressive damage method,the method based on dynamic characteristic,and the examples of these methods are presented. At last,based on personal knowledge,the authors summarize some thinking to the fatigue life prediction for composite blades,and these thinking is perhaps helpful to related researcher.关键词：Helicopter;Composite blades;Fatigue life evaluation;Review
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发布时间：2022-09-22 - 摘要：In this article,fatigue crack growth（ FCG） experiments were conducted on cracked round bar（ CRB）specimens manufactured from PE100 pipes at different R-ratios. In addition, these experimental data were employed in extrapolating to the case of creep crack growth（ CCG） on the basis of linear elastic fracture mechanics（ LEFM）. Afterwards,critical crack depth as well as corresponding stress intensity factor for pipes with circumferential crack were determined under service time 50 years.关键词：Fatigue crack growth;Internal circumferential cracks;Residual lifetime estimation;SIFs
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发布时间：2022-09-22 - 摘要：In critical plane method,a proper cycle counting method should be selected when processing shear components history which perpendicular to each other and parallel to the critical plane such as Case B crack. The MWB method is discussed and optimized firstly and a new multiaxial loading counting method based on critical plane was developed. The new method regarded shear strain as main channel and normal strain as auxiliary channel. According to memory rule for material deformation,counting interval was divided into sub-interval and independent interval step by step. Finally,the new method,Wang-Brown method and MWB method was applied to count a non-proportion multiaxial loading and predict rake dozer H-frame fatigue life respectively,the results show the new method can extract damage event and predict fatigue life accurately.关键词：Multiaxial fatigue;Critical plane method;Cycle counting;Wang Brown method;MWB method
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发布时间：2022-09-22 - 摘要：In this paper,the design of a blade retractable vane pump was demonstrated. The combination of a vane pump with a plug-in type pilot-operated directional control valve can achieve the shift between the two states of oil supply and unloading of the vane pump. In addition,the damping effect of the directional valve makes it possible for the extension of the vane even in the high pressure portion. The axial clearance model was established to calculate the leakage power loss and the shear loss of the oil film. The relationship between the total power loss and the axial clearance was set up to obtain the optimal axial clearance.Furthermore,the condition of blade retraction under unloaded state was concluded and the temperature increase caused by oil film shear was calculated based on the theory of hot wedge oil film. Force exerted on the blade due to oil film expansion under the increased temperature was also verified. The conclusion of blade retraction condition during unloading of the vane pump enables the potential for future applications and further researches.关键词：Vane pump;Retractable blade;Leakage;Optimum clearance;Hot wedge oil film
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发布时间：2022-09-22 - 摘要：The virtual prototyping technology and the finite element analysis method were used to simulate the motion mechanism of a type of air conditioner panel in order to reduce the possibility of the mechanism failure at the design stage. First,the motion of air conditioner panel is analyzed by ADAMS software and load is exported. The results show that the overall motion of the panel is stable,but a large speed change occurs when the panel is fully open. The maximum load appears in the process of air conditioning start-up. Second,the software ABAQUS was used to analyze the stress. It is indicated that the maximum stress region is the contact position between the gear and the rack when the air conditioning starts up. The maximum stress area is the contact position for rack and pinion when the panel is fully open. In both cases,the maximum stress values satisfy the strength requirements. Finally,the simulation analysis is verified by experimental results of Lab VIEW platform.关键词：Motion mechanism;Dynamics simulation;Finite element analysis;Strength check
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发布时间：2022-09-22 - 摘要：This paper study on some enhanced spacers and then get it `s static mechanical properties through the finite element analysis software of ANSYS. The research use the horizontal tension and compression load and radial force load that spacer can bear to simulate the conductor icing and short-circuit working condition. The research considered the spacer`s material nonlinear and the advanced contact nonlinearity of spacer multibody systems. Compared with experiment result,it shows that the weakest part is the spacers ` wire clamp. Rubber mat can reduce the collision between components and play a role in energy storage. The research result provide a good reference for the spacers` design、improvement and usage. And it lays the foundation for the fine simulation analysis of transmission line system.关键词：Spacer;Multibody nonlinear;Statically analysis
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发布时间：2022-09-22 - 摘要：In order to raise the efficiency of the structure vibration simulation of gearbox-base coupling system,the equivalent mass and stiffness of the base on each connection point was extracted using substructure method,and the base was equivalent to some mass elements and spring elements. Based on this,the structure vibration simulation model of the gearbox-base coupling system was established and the structure vibration simulation was completed. The simulation results were compared with the simulation results using the full finite element method. The results show the difference between the equivalent acceleration levels on each connection point obtained by using the substructure method and that obtained by using the full finite element method does not exceed 3 dB,and the simulation time of the substructure method only accounts for 38. 5% of that of the full finite element method.关键词：Gearbox-base coupling system;Structure vibration;Simulation;Substructure method
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发布时间：2022-09-22 - 摘要：A method about fatigue strength analysis of high-strength joint bolts was proposed on the background of gearbox housing joint design of the wind turbine. The method was based on the theory of multi-axial fatigue. And the calculation process of the method described as following: first,the multi-axial non-proportional loads,which loading on the hub blade because of natural wind,were transformed into corresponding stress spectrum after the process of the stress calculation of housing FE model and the stress treated according to the rain-flow counting rules. Second,the Mises stress was synthesized at the calculation nodal location of the bolt cross section from the multi-axial stress spectrum. And third,the fatigue damage of the nodal location was calculated according to the VDI2230 standard under the consideration of the bolt material S-N curve. Finally,the fatigue safety factor of the joint bolts was obtained according to the theory of Palmgren-Miner. Application software was programmed according to the method. With the software,a case of high-strength joint bolt fatigue strength was analyzed,and the fatigue safety factor is1. 819 within the design life of 20 years. The paper proposes a new way to evaluate the fatigue strength of high-strength joint bolts under complex loading condition.关键词：Multi-axial fatigue;Nonproportional loading spectrum;High-strength joint bolts;Main gearbox of wind turbine
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发布时间：2022-09-22 - 摘要：The intermediate pressure outer cylinder of steam-turbine of new units fractured during the 168 h running. The cracks were also found on the other bolts used on the intermediate pressure outer cylinder. It showed by the failure analysis that the brittle fracture occurred because of the high axial stress. The stress distribution was studied based on finite element analysis.The full screw thread and fine grid blocks were used to gain the higher calculation accuracy. It said that the stress of the screw thread was closely influenced by the stress of the mean stress of screw and the stress-strain curve. The force on the three screw threads which near the screw was higher than other screw threads.The maximum stress on the screw threads was 2.5 times of the screw and reached 82.8% of yield strength at the operating condition. The loading process was simulated and it showed that the stess was influenced by the loading process. Considering the service condition of the bolts,the fracture of the bolts was mainly caused by the lack of safety tolerance and the additional stress.
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发布时间：2022-09-22 - 摘要：Aiming at the automobile gearbox shell local deformation failure problem,an evaluation method based on the dynamic stiffness of the critical point of the target shell is proposed. In a front transverse gearbox as the research object,using Hyperworks software to establish the finite element model of shaft hole in the key points of the incentive target the input method of transfer function,the vibration characteristics,vibration frequency analysis of vibration response of transmission after strong shell,obtained after the transmission housing mounting point acceleration frequency response curve and the frequency response curve of dynamic stiffness. Furthermore,the structure of the rear shell of the transmission is improved,and the improved structure is verified by software. Research shows that the dynamic stiffness of the frequency response curve evaluation method is an intuitive and accurate relationship with the deformation response of shell structure,can accurately find the effective method to frequency range and location of improved housing, and the housing structure improvement can effectively improve the vibration characteristics of the shell structure.关键词：Transmission housing;Vibration transfer function;Vibration characteristic;Dynamic stiffness;Structure improvement
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发布时间：2022-09-22 - 摘要：This paper introduces the structure and working principle of a device for supporting bomb with the combination of ratchet and crank-slider. The virtual prototyping technology is used to analyze the working process of the device,and that the dynamic relationship between the components and the curve of spring force in the buffer mechanism is obtained. The results show that it is feasible to apply the one-way rotation characteristic of ratchet wheel and the quick-return characteristic of crank-slider mechanism to the device. The device for supporting bomb with the principle can realize the cushioning and the locking positioning of the projectile. It meet the projectile transport stability requirements. The device shows the features of intensive structure,small occupied space and wide applicability. It provides a new design idea for the design of the sabot device. While in the mechanical field,it also has a positive significance for extending the scope of combination organization.关键词：Ratchet;Crank slider;Sabot structure;Virtual prototype;Dynamic simulation
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发布时间：2022-09-22
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