最新刊期
期 2 ， 2021
- 摘要：The research of ball automatic balancing device mainly focused on single ball automatic balancing device and mostly to study its plane motion. A two-plane ball automatic balancing device for rigid rotors was analyzed. The mathematical models of two-plane automatic ball balancing device for double eccentric disk were established and derived the vibration differential equation by the Lagrange equation,the autonomous system was obtained by rotating coordinate transformation. The stability was analyzed by Lyapunov first approximation theory. Then,the numerical simulation was carried out by Matlab software to analyze the vibration suppression characteristics of two-plane ball automatic balancing device and the movement rule of the balance ball at different rotational speeds and eccentric phases. The research result shows that the two-plane ball balancing device can restrain the plane motion and the space rotation significantly above the second-order critical speed.关键词：Two-plane;Ball automatic balancing device;Rigid rotor;Lyapunov;Vibration suppression characteristics
- 4
- |
- 118
- |
- 1
发布时间：2022-09-22 - 摘要：Wind Turbine Gearbox is an important part of the wind turbine,in the long-term operation will inevitably occur various types of faults,its inspection and maintenance methods will become the focus of scholars. By analyzing the research status of condition monitoring methods and means,fault feature extraction methods and maintenance strategies for wind turbine gearbox,the main problems in the research of inspection and maintenance methods are summarized. Some suggestions are put forward,such as the research of on-line monitoring method and means of wind turbine gearbox based on multi-sensor,the research of intelligent fault diagnosis method of wind turbine gearbox based on multi-source information fusion,the research of preventive maintenance strategy of wind turbine gearbox based on life distribution and real-time monitoring data,etc. It can be used for reference for the research of wind turbine gearbox inspection and maintenance method.关键词：Wind turbine gearbox;Condition monitoring;Fault diagnosis;Maintenance strategy;Status and development
- 5
- |
- 413
- |
- 2
发布时间：2022-09-22 - 摘要：The fault impact signal of bearing on large-scale wind turbine is usually disturbed by complex loads and strong background noise,and its incipient faults are not easy to detect. To solve this problem,in this paper,an improved multi-scale morphological analysis method based on information entropy（ IE） and feature energy factor（ FEF） is proposed. Morphology gradient product operation（ MGPO） is an effective morphology operator for extracting rolling bearing impact signals. This paper proposes a multi-scale morphological analysis method based on MGPO operator in order to extract more detailed fault feature information,and for improving the inadequacy of the kurtosis criterion and the signal-to-noise ratio in selecting the optimal scale,in this paper,a comprehensive scale range selection method based on information entropy and characteristic energy factor is also proposed. Experimental and comparative results show that the algorithm proposed in this paper has a certain of advantages.关键词：Wind turbine;Multi-scale morphology;The information entropy;Characteristic energy factor;Fault diagnosis
- 4
- |
- 187
- |
- 2
发布时间：2022-09-22 - 摘要：A rotor system in rubbing is shown to exhibit complex phenomena including period-doubling bifurcation,quasiperiodic and chaotic motions due to itsstrongly nonlinear dynamic characteristics. Based on the mechanical model of a single-disk flexible Jeffcott rotor,the fourth-order Runge-Kutta method with variable step size was used for numerical simulation. The essential relationship between the model parameters and the dynamic characteristics of the system is studied by used periodic bifurcation diagrams,axis trajectory diagrams,Poincaré section diagrams and maximum rubbing force diagrams. The simulation results show that the change of stiffness ratio has great influence on the dynamic characteristics of the system. With the increase of damping coefficient,the type of periodic motion mode of the system decreases obviously,and the chaotic region decreases accordingly. When the eccentricity ratio increases,the dynamic characteristics of the system become more complex. Meanwhile,the maximum rubbing force increases significantly,and the rubbing events of the rotor system become more serious. The calculation and analysis in this paper may be helpful for avoided rubbing events and limited maximum friction in the design of single-disk flexible rotor.关键词：Rubbing;Periodic motion;Nonlinear;Bifurcation
- 5
- |
- 198
- |
- 3
发布时间：2022-09-22 - 摘要：In order to accurately obtain the fracture mechanics parameters of the cast E-grade steel material,and to study the crack propagation law and influencing factors of material,a fatigue crack growth test of the CT specimens of the cast E-grade steel was carried out. The Paris formula was used for characterization. Taking the crack growth calculation model of CT samples as an example,the fatigue crack growth length and load cycle period results of 5 groups of samples were calculated by using the M-integral numerical method. The relative error was within 10%,which had better consistency. Through further comparison and analysis of the reasons for the error between the test and the simulation,it is shown that the load amplitude is the main error factor,and the initial crack position,propagation rate parameters,and crack length parameters have little effect,so as to provide a reference for the prediction of three-dimensional fatigue crack propagation rules for complex structures.关键词：Cast E grade steel;Paris crack growth rate curve;CT specimen;M interaction integral
- 5
- |
- 361
- |
- 1
发布时间：2022-09-22 - 摘要：Cohesive zone model（ CZM） is widely in used integrity evaluation for composites with delamination damage,and accurately obtaining the CZM parameters has important effects on the evaluation results. In this paper,the inversion of CZM parameters is studied,and double-cantilever beam（ DCB） tests are carried out to obtain the load-displacement data at the loading point. Combined with the outputs of the corresponding forward finite element（ FE） model,an objective function is constructed and artificial bee colony（ ABC） algorithm is employed to optimally identify the CZM parameters. Numerical and experimental results have demonstrated that,ABC algorithm has better convergence and optimization ability than genetic（ GA） algorithm and particle swarm optimization（ PSO） algorithm; it has certain anti-noise capability that can optimally obtain the CZM parameters under different levels of measurement noise,and the simulated load-displacement data with the inversely identified parameters match the actual test ones well.关键词：Cohesive zone model;Parameter inversion;Artificial bee colony algorithm;Double-cantilever beam tests;Finite element simulation
- 3
- |
- 200
- |
- 1
发布时间：2022-09-22 - 摘要：Aiming at 304 austenitic stainless steel paramagnetic material,a multi-class classification support vector machine LIBSVM algorithm was carried out for the magnetic anomaly inversion of weak magnetic signals. Orthogonal test design was used to make 4 testing samples with an artificial defect. The characteristics of artificial defect such as width,amplitude,and area were extracted for the collected magnetic anomalies of the defect signals. The LIBSVM algorithm was used to establish the relationship between the magnetic anomalies of the defect signals and the artificial defects. A total of 16 groups testing results indicate that 10 of the 16 defects inversion are correct in length and width,and 8 defects inversion are correct in depth. The inversion accuracy of defect length,width and depth is high,which provides a reference basis for the study of magnetic anomaly inversion for weak field signals,related experimental methods and equipment development.关键词：304 austenitic stainless steel;Artificial groove defect;Support vector machine LIBSVM;Weak magnetic detection;Inversion
- 2
- |
- 200
- |
- 1
发布时间：2022-09-22 - 摘要：Plasma nitriding of the quenching and tempering 42 CrMo steel was carried out at 530 ℃ using two different N2-H2 atmospheres: 3% N2 and 80% N2,which prepared two types of samples with different compound layers,ε + γ’ compound-phase andγ’ single-phase,respectively. Impact wear tests were performed using the impact wear test rig controlled by kinetic energy. The effect of nitrided-layer microstructure control on impact fretting wear property of 42 CrMo steel was studied. The results show that the impact wear properties of 42 CrMo steel can be improved by plasma nitriding,the hardness of the plasma nitrided samples are higher than that of the 42 CrMo steel samples,and the peak impact force and energy absorption rate of the plasma nitrided samples were lower. Compared with the γ’ single-phase sample,the ε + γ’ compound phase sample show better impact wear properties due to its higher hardness and better impact dynamic response. The impact wear mechanism of 42 CrMo steel is plastic deformation,peeling wear and oxidative wear. The impact wear mechanism of nitrided samples is fatigue spalling,slight abrasive wear and oxidative wear. Plasma nitriding significantly reduces spalling and oxidation of 42 CrMo steel during impact wear,and the degree of oxidation of the wear scars on γ’ single-phase samples was slighter than that of ε + γ’ composite phase samples.关键词：42CrMo steel;Plasma nitriding;Impact wear;Compound layer;Wear mechanism
- 4
- |
- 291
- |
- 1
发布时间：2022-09-22 - 摘要：For achieving high hardness and high performance alloy coating,the high entropy coating of FeNiMoCoCrTi was prepared by laser cladding on the surface of 45# steel. The process parameters were optimized by using the orthogonal test method,for getting the best combination of process parameters,the measured data were sorted out and summarized by a combination of Mathematical Polarity and Variance analysis method,XRD phase analysis and hardness test were carried out. The results show that the main factors that affect the hardness and performance of the coating are the laser power and scanning speed,and the defocusing amount mainly affects the hardness. The preferred combination of process parameters is laser power 3000 W,scanning speed 0. 015 m/s,defocusing amount 50 mm. The main phase composition of the coating is FCC + BCC + Simple cubic1+ Simple cubic2+ Simple cubic3+ Laves phase.关键词：Laser cladding;Technological parameters;Orthogonal method;Mathematical variance analysis
- 2
- |
- 555
- |
- 1
发布时间：2022-09-22 - 摘要：Aiming at the problem that Al7050 alloy is easy to deform in cutting process,the JC constitutive model suitable for practical cutting is established. Based on Oxley’s theory,a solution model was established. The JC constitutive model parameters of Al7050 alloy were obtained by using genetic algorithm and experimental data,and the JC constitutive model was verified by using cutting force as evaluation index. The results show that the strain range of JC constitutive model is 0. 80 ～ 1. 01,the strain rate range is 1. 6 × 10~3 s-1～ 2 × 10~4 s-1,and the temperature range is 96. 48 ℃ ～ 213. 07 ℃ . The average errors of the simulation and test values of the main cutting force and feed force using the custom material model are 4. 79% and 16. 08%,respectively. The average errors of the simulation and test values of the main cutting force and feed force of the material model with the software are 15. 08% and 25. 97% respectively,and the conclusion that the simulation value of the cutting force with the custom material model is more consistent with the test result is drawn.关键词：Al7050 alloy;Oxley’s theory;Orthogonal cutting;Genetic algorithms
- 3
- |
- 215
- |
- 1
发布时间：2022-09-22 -
MULTI-OBJECTIVE OPTIMIZATION OF VEHICLE/TRACK PARAMETERS BASED ON RBF NEURAL NETWORK SURROGATE MODEL
摘要：The RBF（ Radial Basis Function） neural network surrogate model that employed to explore the multi-objective optimization problems of vehicle and track parameters is to improve the dynamic performance of vehicles. The sensitivity of dynamic performance on vehicle and track parameters was analyzed by constructing a vehicle-track coupling dynamic simulation model of high-speed train and using the UM and Isight joint simulation technology. The eight parameters with the highest sensitivity ratio were used as the design variables,and a surrogate model of RBF neural network was established on the response of the dynamic performance. Then the model was performed to optimize the vehicle/track parameters. The results show that the optimization rate of the optimal solution for the derailment coefficient is 13. 14%,and the optimization rate of the wheel load reduction rate is 14. 63% after the vehicle and track parameters are optimized,which demonstrates that the optimization effect is remarkable,and the dynamic performance of the vehicle has been significantly improved.关键词：High speed train;Agent model;Radial Basis Function（RBF）;Multi-objective optimization;Sensitivity analysis- 3
- |
- 519
- |
- 1
发布时间：2022-09-22 - 摘要：Improving the efficiency of tidal turbine is the key research of oceanenergy development. The focus of improving the efficiency of tidal turbine lies in the geometry of the turbine blades. Based on the hydrofoil of NACA4412,the method of Joukowski conformal transformation was used to build the parameterized model,the genetic algorithm was realized by MATLAB programming and an optimal solution was found on the basis of using high lift-drag ratio as the objective function under the design variables and constrains. After obtain the optimal solution,use the CFD software was used to simulate the initial hydrofoil and the optimized laminar hydrofoil. According to the results,we can find that the optimized hydrofoil hada great improvement in the liftdrag ratio and lift coefficient compared with the initial hydrofoil. The lift coefficient and the maximum lift-drag ratio of the hydrofoil are increased by 18. 72% and 46. 84% respectively,and the angle of attack is smaller when the hydrofoil reaches the maximum lift-drag ratio after being optimized. The results validate the rationality and validity of the proposed optimal solution and provide a theoretical basis for the subsequent optimization design of tidal turbine hydrofoils.关键词：Tidal turbine;Hydrofoil optimization;Genetic algorithm;Blade element momentum theory;Numerical simulation
- 3
- |
- 270
- |
- 1
发布时间：2022-09-22 - 摘要：In view of the problems such as poor bearing capacity and large motion error of hexapod robot with series leg structure and plane multi-link structure,The parallel leg hexapod agricultural robot mechanism with one translational and two rotations（ 1 T2 R） was proposed. Firstly,the kinematics position,speed and acceleration of the parallel leg mechanism were analyzed. Secondly,the working space of the parallel leg mechanism was analyzed based on the structural constraints. Finally,three-dimensional modeling and simulation analysis of the hexapod agricultural robot mechanism were carried out. Theoretical analysis and simulation results show that the forward and inverse kinematics equations of the parallel leg mechanism can be solved analytically,and the forward equation has at most four groups of solutions. The partial motions of the mechanism are with inputoutput decoupling and the mechanism can be controlled easy. The parallel leg mechanism has a large working space and is composed of multiple spherical crowns. The hexapod robot can move forward and backward,left and right without turning. The mechanism design is reasonable,which is suitable for the use of agricultural robot walking mechanism.关键词：Hexapod agriculture robot;Parallel leg;1T2R;Kinematics;Workspace;Simulation analysis
- 5
- |
- 453
- |
- 1
发布时间：2022-09-22 - 摘要：Absrtact Aiming at the safety problem of the hydraulic keyless sleeve coupling caused by the increase of bearing power of a ship’s CPP,studied the interference installation of coupling sleeve-cone sleeve-tail shaft for transferring torque and thrust. Firstly,analyzed the composition and working principle of hydraulic non-key sleeve coupling,then studied the thick-wall cylinder theory of the coupling interference fit,according to the formula of the stress and deformation amount at a certain diameter of the thick-wall cylinder,calculated the interference amount of coupling sleeve cone surface and axial displacement of coupling sleeve when transferring 2. 8 times rated torque. Then,calculated the tangential stress and synthesized the principal stress at the mean diameter of the sleeve-in conical surface at 2. 8 times of the rated torque,checked the strength of the coupling. Then,according to the stipulation that the maximum compressive stress of the cone surface was not more than 0. 7 times the yield strength,calculated the maximum cone surface interference and the maximum hoop sleeve axial displacement. Then,studied the influence of the installation and measurement error of the coupling on the transmission capacity. Then,considered the interference loss caused by surface roughness,selected the design values of interference and axial displacement within the allowable range of the code. Finally,studied the technical of the interference fit of the coupling. The results show that the design interference value and hoop sleeve axial displacement meets the ship inspection regulation of transferring 2. 8 times rated torque,and the cone surface compressive stress does not exceed 0. 7 times yield strength of the material,which meet the application requirements,and the research results and installation technology can be used for reference by peers.关键词：Hydraulic keyless sleeve coupling;Transfer torque;Stress;Strength check;Interference
- 3
- |
- 57
- |
- 1
发布时间：2022-09-22 - 摘要：Frame-type combined spindles are widely used in precision products such as CNC rotary tables and aerospace flight simulators. Due to the multiple geometric errors in their component parts,the rotary precision of the frame-type combined spindle is directly affected,which further affected the accuracy of the whole axis. In this paper,by correcting the small displacement torsor expression of the cylindrical pair,the three-dimensional cylindricity tolerance was integrated into the Jacobian torsor tolerance analysis model of the frame-type combined spindle. It made up for the deficiency that the Jacob torsor model could not deal with the form tolerance. On this basis,the rotary datum of the frame-type combined spindle was modeled and characterized. The coaxiality error of the two working shaft segments in the frame-type combined spindle was solved,and the limiting rotary precision of the frame-type combined spindle under the influence of the multinomial form and position errors was predicted. The measurement results proved the correction of the method.关键词：Jacobian-torsor;Tolerance analysis;Cylinder tolerance;Rotary accuracy
- 3
- |
- 139
- |
- 0
发布时间：2022-09-22 - 摘要：Based on fractal theory,continuous smooth exponential model of elastic-plastic contact,and considering the influence of friction factors and applying an improved W-M function that simulating three-dimensional fractal profile surface,the fractal model of energy dissipation for tangential contact in joint interfaces and its equivalent viscous damping model are proposed.It is shown from the models that the tangential contact damping dissipating energy of joint interfaces decreases with the increase of normal load on joint interfaces,the friction coefficient,but increases with the increase of plastic index of contact materials,the ratio of the tangential dynamic load amplitude to normal contact load,the fractal dimension,the fractal roughness of joint interfaces. The variation rule of the tangential contact damping dissipating energy of joint interfaces with the fractal dimension is very complex. The tangential equivalent viscous damping of joint interfaces decreases with the increase of friction coefficient,the fractal roughness of joint interfaces,but increases with the increase of normal load on joint interfaces,the ratio of the tangential dynamic load amplitude to normal contact load,the plastic index of contact materials. The tangential contact equivalent viscous damping of the joint surface increases at first and then decreases with the increase of the fractal dimension,and the maximum value is taken when the fractal dimension is equal to 2. 7. There is an obvious nonlinear relationship between the tangential contact equivalent viscous damping of joint interfaces,when fractal dimension D value is between 2. 1 and 2. 5. There is an obvious linear relationship between the tangential contact equivalent viscous damping of joint interfaces and the normal contact load,when fractal dimension D value is between 2. 5 and 2. 9.关键词：Tangential contact damping;Energy dissipation;Three-dimensional fractal;Joint interface
- 4
- |
- 170
- |
- 0
发布时间：2022-09-22 - 摘要：Aiming at the problems of poor mixing effect and uneven material mixing in the practical production of the multifunction wood plate double screw mixer. In this paper,the mixing structure is optimized,and the original single-axis double-helix mixing structure is replaced by the double-axis double-shear double-helix mixing structure. With waste wood chips,magnesium oxide and other additives as raw materials,EDEM simulation software was used to simulate the motion of the stirring process and the mixing simulation of different added materials. It is concluded that the improved double-shaft mixer works better than the structure before the improvement. On the basis of this conclusion,by modifying the Angle parameter of the stirring blade and changing the rotation speed of the stirring shaft,it is concluded that the installation Angle of the stirring blade is about 45 ° and the stirring speed is about 180 r/min. Finally,the dynamic finite element analysis of the actual mixing process is carried out to ensure the feasibility of the optimized design.关键词：Double spiral mixer;Discrete element method（EDEM）;Mixing degree;Dynamic finite element analysis
- 3
- |
- 367
- |
- 2
发布时间：2022-09-22 - 摘要：Aiming at the lubrication characteristics of spherical hybrid sliding bearings（ SHSBs） for an ultra-high precision grinding machine,the Reynolds equations often adopt more assumptions,and the calculation accuracy cannot meet the design requirements of ultra-high precision bearings. The pressure and temperature field distribution characteristics of SHSBs was analyzed by CFD software based on N-S equations. And the variation law of structural parameters and working parameters on load capacity,flow and temperature rise,as well as the coupling effect between various parameters was explored. Based on this,the orthogonal experimental design method was used to obtain the optimal parameter combination of SHSBs under the premise of meeting the multi-objectives of high load and low temperature rise. The results show that these parameters significantly affect the bearing capacity and temperature rise of the bearing,and there are also cross-coupling effects. The analysis results are instructive for further research on the design of SHSBs.关键词：Spherical hybrid sliding bearings;Computational fluid dynamics;Coupling effects;Static characteristics;Temperature rising characteristics
- 4
- |
- 146
- |
- 1
发布时间：2022-09-22 - 摘要：The design of the self-stabilizing structure is the key to the design and research of semi-submersible unmanned boat,which directly affects the self-stabilization state of the boat in the water. By calculating and adjusting the center of gravity and buoyancy of the structure of the boat,it can sail stably in large wind waves and water currents. The structure of the boat adopts the modular idea design method. By changing the weight and volume of the module,the center of gravity and the floating center of the whole structure are more easily adjusted; based on the theoretical calculation of the center of gravity and the floating center,the arrangement and installation between the hull modules can be adjusted. In addition,the initial stability of the boat was analyzed and a Matlab program was calculated. The verification of the calculation results shows that the design of the selfstabilizing structure of the boat meets the requirements. The lake test and the sea test prove that the boat can effectively resist the wind and water flow interference,and verify that the overall self-stable structure design of the boat is reasonable and effective. At the same time,the research results can also provide some reference for the design of the semi-submersible unmanned boat.关键词：Semi-submersible unmanned boat;Stability;Overall structure;Modular
- 4
- |
- 223
- |
- 0
发布时间：2022-09-22 - 摘要：Based on the generalized Mian and Spencer plate theory,the problem of graphene reinforced functionally graded circular plates subjected to concentrated force and temperature field is studied. By virtue of the modified Halpin-Tsai model,the effects of temperature dependence and defect size of graphene nanoplatelets on the Young’s modulus of graphene reinforced composites are considered. Three kinds of distributions of graphene nanoplatelets（ GPLs） along the thickness direction are studied. When the circular plate is subjected to a concentrated force at the center,the problem is transformed into that of an annular plate subjected to uniformly distributed shear forces along the inner boundary. The nonlinear temperature field caused by heat conduction is considered along the thickness direction of the plate. Through comparison with available results in the numerical example,the validity of the method in this paper is verified,and the influences of GPL distribution,defect size,temperature field and boundary conditions on the thermoelastic response of circular plates are discussed.关键词：Graphene nanoplatelets;Functionally graded circular plate;Concentrated force;Temperature field;Elastic response
- 2
- |
- 85
- |
- 1
发布时间：2022-09-22 - 摘要：The key components in aircraft will be subjected to typical asymmetric loads in service,thus their fatigue behavior can be inevitably strongly affected by the mean stress effect. The modified Walker model employs the multiple-nonlinearfitting method to deal with fatigue test data under various stress ratios,by which the influence of material and maximum stress on mean stress effect can both be considered. Eighteen sets of fatigue test data from twelve kinds of aeronautical materials in various loading conditions were employed to validate the predict accuracy of modified Walker model,and the results were compared with other commonly used models. The study shows that the influence of maximum stress on mean stress effect varies with materials,while the prediction accuracy of the modified Walker model for each group of test data is better than that any other candidate models to varying degrees.关键词：Fatigue life;Mean stress effect;Modified Walker model;Multiple nonlinear fitting
- 6
- |
- 219
- |
- 2
发布时间：2022-09-22 - 摘要：Among the fatigue life models of honeycomb sandwich structures,the most researched is the S-N curve model.This paper classifies and summarizes the commonly used forms of honeycomb sandwich structures’ S-N curve model. At the same time,the fatigue tests data of honeycomb sandwich structure is collected and normalized according to the relevant mechanical principles,and some general results were obtained. Based on the material properties of the honeycomb core,several influence factors on the fatigue performance of the structure are discussed.关键词：Honeycomb sandwich structures;Fatigue life model;S-N Curve;Influence factors on the fatigue performance
- 3
- |
- 268
- |
- 1
发布时间：2022-09-22 - 摘要：Stress intensity factor（ SIF） for cracked engineering structures under different loading is one of the core issues of fracture analysis. A slender fin-shaped shell possesses both shell and beam characteristics,in the cross-section of which some typical periodic cracks,such as the periodic cracks on fins and circumferential cracks,may arise usually. There will be different singular stress fields next to crack tips for a cracked fin-shaped shell under bending. Based on the conservation law and the elementary mechanics,a technique to determine SIFs has been proposed in this article,which is simple and easy to understand.The SIFs calculated by using of the present method agree well with the FEM results.关键词：Conservation law;Stress intensity factors;Fin-shaped shell;Cracks;Finite element method
- 5
- |
- 91
- |
- 0
发布时间：2022-09-22 - 摘要：For crane metal constructions,fatigue cracks during long-term services easily occurs. A combination of crack stop-hole and CFRP for repairing cracked metal structures can achieve better results than single repairing methods. For the crack initiation stage of the crack stop-hole edge after composite repair,by utilizing ABAQUS and FE-SAFE to establish a finite element analysis model,the influence of factors such as the reinforcement method,the radius of the stop-hole,the length of the fatigue crack and the distance from the crack tip to the edge of the crack stop on the crack initiation life were analyzed and verified through experiments. The results show that it is feasible to use ABAQUS and FE-SAFE to analyze the durability of the composite repaired structure,which can provide references for the formulation of plans to repair.关键词：Carbon fiber reinforced polymer（CFRP）;Crack stop-hole;Composite repair;Crack initiation;Fatigue analysis
- 3
- |
- 179
- |
- 1
发布时间：2022-09-22 -
SIMULATION OF FATIGUE CRACK INITIATION LIFE OF TC4 TITANIUM ALLOY BASED ON ITS MESOSCOPIC PROPERTIES
摘要：This paper presents that the prediction model of fatigue crack initiation life of TC4 titanium alloy,and the feasibility of the model in predicting the fatigue crack initiation life of TC4 titanium alloy is verified by experiments. Based on the micro dislocation model of crack initiation and Tanaka mura’s formula of crack life,considering the surface roughness,a finite element model for fatigue crack initiation of TC4 titanium alloy is proposed,and the validity of the simulation model is verified by experiments. The results show that the crack initiation forms of the model are different under different load levels. At high stress levels,the model has a large number of independent microcracks in addition to the initiation and propagation of the main cracks,with a large crack density. At low stress levels,the model has a small number of independent microcracks,with a small crack density.关键词：Titanium alloy;Fatigue life;Crack initiation;Simulation model;Meso mechanics- 3
- |
- 433
- |
- 1
发布时间：2022-09-22 - 摘要：Owing to the dispersion of material and structure property,the fatigue life of a structure part depends on all its high stress sites. A multi-site damage structure is a series system with many weak links（ damage sites） in probability sense.Therefore,the fatigue life（ a random variable） of a complex structure part with multiple damage sites will be less than the life of the weakest site on the part. Owing to test equipment and conditions,the loads and stress state of a test part cannot exactly reproduce the real structure part in service. The present paper analyzed fatigue life influence factors for a large-size structure part test,expressed the relationship between fatigue life and number of high stress sites,studied fatigue life equivalence method when changing the fully reversed cyclic load in service into pulsation cyclic load in test. Through damage site number based load level adjustment and mean stress modification,this paper provides a load equivalence method to simplify fatigue test of large size multisite-damage parts. The results indicate that through such load transformation,the loading frequency of the electric-hydraulic servo test system can be increase from 2 Hz to 4 Hz,while the fatigue life distribution of the tested part keeps nearly the same as that of the service part.关键词：Multi-site-damage;Serial system;Fatigue test;Mean stress effect;Fatigue life equivalence
- 5
- |
- 185
- |
- 1
发布时间：2022-09-22 - 摘要：In order to improve the wear resistance of titanium alloy,the plasma chromizing treatment of the duplex TC4 sample was carried out by vacuum glow plasma surface alloying technology. The local hardness and modulus of the sample were tested by nanoindentation. The fatigue properties of the specimens were evaluated by a rotary bending fatigue machine under a given load. The results show that the chromium alloy layer obtained after 5 hours of 850 ℃ treatment is composed of four sublayers,namely the Cr deposit layer,TiCr2 layer,Ti4Cr layer and Cr-Ti solid solution layer. The elastic modulus and hardness of the adjacent sub-layers are significantly different,while the plasma chromizing treatment deteriorates the fatigue properties of the TC4 titanium alloy,and the fatigue life of the plasma chrome-plated sample can be increased by shot peening,which is attributed to The sample has the highest residual compressive stress,significant work hardening and a good balance of hardness and toughness.关键词：Plasma chromizing;Shot peening;Titanium alloy;Fatigue behavior
- 4
- |
- 97
- |
- 0
发布时间：2022-09-22 - 摘要：According to the cracks in the gearbox of a certain type of diesel locomotive,the finite element model of gear box was established to make the life prediction by using the random vibration fatigue theory and the linear fatigue cumulative damage theory of Palmgren-Miner. The life prediction of the original structure differs from the actual statistical results by only 26 000 km,and two optimized structures are proposed based on the finite element results of the original structure. The predicted fatigue life of the two optimized structures is higher than that of the original structure by 1. 032 million km and 1. 763 million km respectively.After modal and excitation frequency analysis,it is concluded that transverse excitation is the main cause of structural resonance.By comparing the modal frequency and excitation frequency of the three structures,it is found that the lower the excitation frequency energy value corresponding to the modal frequency is,the longer the fatigue life is. Therefore,the frequency corresponding to the high excitation energy should be avoided when optimizing the structure of the gearbox.关键词：Gearbox;Random vibration;Fatigue life;Resonance;Structural optimization
- 4
- |
- 388
- |
- 3
发布时间：2022-09-22 - 摘要：With the aid of applying decomposed loads,a method is suggested to construct primary structure and obtain the primary bending stress for the tubesheet of fixed tubesheet heat exchanger. The favorable redundant rotation constraint of the cylinder to the tubesheet can be remained in the primary structure. Taking a methyl alcohol synthetic reactor as example,the mentioned method is used in the FEA to solve the problem without primary structure analysis. It is founded that the allowable load yielded by the mentioned method is comparative to that by direct limit load analysis,which indicates the feasibility of the mentioned method. It should be noted that the conode simplication of the tube and the tube hole are generally non-conservative. If the stress intensity evaluation line is located on the tube hole,a suitable stress intensity enlargement factor should be employed.关键词：Fixed tubesheet heat exchanger;Tubesheet;Design by analysis;Primary bending stress;Finite element method
- 4
- |
- 95
- |
- 0
发布时间：2022-09-22 - 摘要：The stator stiffness and strength are systematically analyzed according to the characteristics of stator structure and load condition in order to achieve the goal of stator lightweight design of large-capacity outer rotor permanent magnet wind turbine generator set. The stress and deformation of the stator are obtained,and the optimal area of the stator are determined. Under the condition of ensuring the stiffness and strength of the stator,the initial topology optimization of stator is designed by variable density method. On this basis,the dimension parameters that have great influence on the stator mass,stiffness and strength are determined by sensitivity analysis and optimized by response surface method. After optimization,the maximum stress and strain of the stator are in the allowable range. The mass of stator is reduced by 1 199 kg,which means that it is 11. 25% lighter than the original stator. Therefore,the optimization method studied in this paper works well for the lightweight target.关键词：Permanent magnet generator set;Topology optimization;Sensitivity analysis;Response surface optimization;Lightweight design
- 2
- |
- 158
- |
- 2
发布时间：2022-09-22 - 摘要：Taking the railway passenger car water tank as the research object,the bidirectional fluid-solid coupling method is used to model and numerically analyze the liquid impact sloshing problem in the passenger car tank using the finite element analysis software ANSYS Workbench. By studying the continuous impact load on the water tanks with different water contents in the longitudinal direction of the vehicle,the change history of the tank structure stress with time and the deformation history of the tank structure with time are obtained. The results show that the maximum stress and maximum displacement of the box gradually increase with the increase of water content. Through analysis,the weak position of the box structure is determined,By plotting the comparison curve between the test value and the simulation value of each measuring point,The consistency between the calculation model of the water tank and the actual model was verified. Shows that the two-way fluid-solid coupling method and water tank model used in this paper have good reliability,which provides a reliable analysis method for the design and optimization of the water tank structure of the railway passenger car.关键词：Railway passenger car water tank;The finite element;Two-way fluid-solid coupling;Strength analysis
- 3
- |
- 206
- |
- 1
发布时间：2022-09-22 - 摘要：In order to achieve the movement demands of sprained ankle patients in different rehabilitation stages,this paper proposes a kind of metamorphic parallel mechanism for ankle rehabilitation,which can obtain the switch of 3 SPS/PS motion and 3 SPS/S motion by locking or driving the prismatic pair of（ P） S branch chain. The initial configuration of the switch had instantaneously one movement and three rotations in space. Among them,3 SPS/PS configuration has four degrees of freedom,namely the rotation of the moving platform around the x axis,y axis and zaxis and the displacement along the z axis. 3 SPS/S configuration has three degrees of freedom,namely the rotation of the moving platform around the x axis,y axis and z axis,respectively. Finally,the conclusion is verified by screw theory analysis and Adams simulation.关键词：Metamorphic;Parallel mechanism;Degree of freedom;Screw theory
- 4
- |
- 178
- |
- 0
发布时间：2022-09-22 - 摘要：Taking the left-front door of a certain vehicle as an object,the method of combining the welding plate and the adaptive response surface method（ ARSM） was applied to optimization of the thickness of door parts for lightweight research. The finite element model was established in Hyperworks and its modal and stiffness were analyzed. Then Hypermesh common-node model was used to simulate the laser tailor-welded technology,the front and rear parts of the original spot-welding door inner plate were connected by tailor-welded blank（ TWB） for optimal design. Through sensitivity analysis,some parts were selected to use adaptive response surface method in the Hyper Study for optimal design. The quality of the optimized door decreased by 6. 01%compared with the original ones. The modal and stiffness of the optimized door structure were analyzed again,The feasibility of TWB and Hyper Study optimization method to door lightweight research was verified.关键词：Modal;Stiffness;Tailored-welded blank;Adaptive response surface method;Lightweight
- 3
- |
- 300
- |
- 3
发布时间：2022-09-22 - 摘要：Aimed at the low frequency of traditional ultrasonic transducers in low frequency domain,a new theoretical model of microbridge was designed,with analysis and research of the mechanical behavior. Solid modeling,modal analysis and electrostatic analysis were carried out with COMSOL 5. 4 for the silicon-based microbridges of the antiferroelectric thick film,which can produce the effect of phase-transition induced strain. Applied with the orthogonal design,the reasonable structure sizes of the microbridge component with small stress and large frequency were obtained. They can provide an important basis for the following fabrication. When the microbridge is 800 μm（ L） × 100 μm（ W）,the corresponding stress is 0. 352 GPa and the resonant frequency equals to 115. 19 kHz,which is superior to traditional ultrasonic transducers in the aspect of better performance based on the smaller sizes.关键词：Ultrasonic transducer;Microbridge;Antiferroelectric thick film;Effect of phase-transition induced strain;Orthogonal design
- 3
- |
- 149
- |
- 2
发布时间：2022-09-22 - 摘要：For the wave cylinder,three wavelength models were established. The large eddy simulation method is used to analyze the flow characteristics of wave members with convection angle under high Reynolds number. The velocity and pressure distribution laws of wave members with different wavelengths were investigated,and characteristics about time-domain and frequency-domain of the circumferential pressure coefficient,drag and lift were discussed. The results show that the larger the surface inclination,the higher the surface pressure variation. The smaller the wavelength is,the larger the resistivity of the member and the main peak ranges. According to the characteristics of flow fields,a wave member with a spatial AOA of λ/Dm=3. 26 obtains better drag and vibration reductions,compared λ/Dm= 5. 5,λ/Dm= 3. 26 and λ/Dm= 2. 24. These findings are vitally significant and valuable for researches and applications about flow characteristics of wave cylinder.关键词：Wave cylinder;High reynolds number;Space angle of attack;Flow field;Aerodynamic characteristics
- 4
- |
- 36
- |
- 0
发布时间：2022-09-22 - 摘要：In order to verify the bending effect of quartz wafer,a special elastic ring clamping structure was designed to install and position the sensitive element. According to elastic mechanics and piezoelectricity,the calculation formula of bending stress and polarization of quartz wafer were deduced and the stress analysis of the elastic ring wafer clamping structure was carried out. In order to reduce the influence of structural deformation on sensor application performance,using the energy principle of elastic mechanics the static stiffness formula of the elastic ring wafer clamping structure under load was calculated. Using the finite element method the strength and stiffness of the elastic ring wafer clamping structure was verified. The theoretical calculation,finite element analysis and experimental measurement results show that the rigidity of the elastic ring wafer clamping structure is more than 10 kgf/um,which meets the requirements of sensor design. The research can provide technical support for the structural design of the new cantilever force sensor and micro actuator.关键词：Elastic ring clamping;Stiffness;Finite element method;Strength;Deformation
- 3
- |
- 56
- |
- 0
发布时间：2022-09-22 - 摘要：Aiming at welding fracture problem of EGR cooler with eccentric intake structure,numerical simulation based on sequential fluid-solid coupling was presented and the improvement of eccentric intake structure was taken. Flow field mesh and solid finite element mesh were set up based on 3 D modeling. The sequential fluid-solid coupling with flow field analysis,heat conduction analysis and thermal stress analysis was taken to study the relation among intake structure,gas side streamline,solid temperature,thermal stress range and the fracture. An improvement scheme with increasing a hump was proposed to improve gas uniformity and reduce local thermal stress range. The results indicate that the sequential fluid-solid coupling is feasible in engineering practice,the partial fracture of EGR cooler will caused by unreasonable eccentric intake structure and will be solved by optimization of flow passage.关键词：Sequential fluid-solid coupling;Eccentric intake structure;Fracture analysis;EGR cooler
- 4
- |
- 99
- |
- 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