最新刊期
期 5 ， 2016
- 摘要：The in-plane dynamic crushing behavior of a new honeycomb structure-the multi-re-entrant honeycomb and reentrant honeycomb topology possessing negative Poisson’s ratio was analyzed here. Firstly the finite element method of ANSYS /LS-DYNA was applied to examine the deformation modes of multi-re-entrant honeycomb and re-entrant honeycomb under different impact loads,where the physical mechanism for the auxetic effect on improving the dynamic crushing strength is revealed. Then the empirical formula of the dynamic crushing strength was deduced based on the classical theory model,where comparisons with the finite element results revealed the effectiveness of the proposed empirical formula. Higher dynamic crushing strength reveals that the re-entrant honeycomb possesses better energy absorption ability than conventional hexagon topology due to its antitraditional deformation mechanism.关键词：Multi-re-entrant honeycomb;Finite element simulation;Negative Poisson’s ratio;Dynamic crushing strength;Empirical formula
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发布时间：2022-09-22 - 摘要：The modal analysis of steering system was made because of the excessive vibration of a certain forklift truck when the engine at medium and low speed conditions at first in this paper. The vibration optimum design was put forward to reduce the vibration of steering wheel by the method of Uniform Design. the test results show that the stiffness of improved steering system is increased and the vibration is decreased obviously on the basis of the invariability of costs,especially when the engine at low speed,the acceleration of vibration on direction x,y,z are reduced 83. 8%,90. 3%,83. 7% respectively. The optimum method provides references for the optimum design of body and frame type structures.关键词：Internal combustion forklift truck;Modal analysis;Uniform design;Vibration optimum
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发布时间：2022-09-22 - 摘要：A fault diagnosis method of the intrinsic mode components symbolic analysis is proposed on the basis of empirical mode decomposition. Firstly,the extension fault signal is decomposed into several intrinsic mode functions under different time scales with empirical mode decomposition. Secondly,analyze the symbolization of intrinsic mode functions in order to find relationship between different faults hidden in them. At last,calculate entropy of symbolized sequence to establish a characteristic vector which can express fault in some way. And then realize the fault diagnosis with the help of some kind of pattern recognize method. The results show that there is a good recognition effect for typical bearing fault and printing machine fault. Bearing failures in offset printing under different rotational speed are detected successfully. The method has a good effect at features extraction in time domain and reduces computation in frequency domain compare with similar research. The symbolic entropy has good application prospects in engineering.关键词：Rolling bear;Fault diagnosis;Empirical mode decomposition;Symbolic signal
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发布时间：2022-09-22 - 摘要：For the problem of Local Mean Decomposition（ LMD） was easily affected by noise interference when in the extraction of fault features,a rolling bearing fault diagnosis method which based on LMD and Independent Component Analysis（ ICA） was proposed. Firstly,original signal was decomposed into a series of production functions（ PF） by the LMD method.Secondly,the estimate of PF was obtained after the PF components had been separated by ICA method,and the noise was effectively removed. Then,mutual information,correlation coefficient and approximate entropy which were extracted from the estimate of PF components were grouped together as a feature vector. Finally,the fault feature vectors were classified by SVM.The results of the feature extraction and fault diagnosis experiments show that the fault recognition rate of LMD-ICA method is significantly better than the traditional LMD method.关键词：Rolling bearing;LMD;ICA;SVM
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发布时间：2022-09-22 - 摘要：When refiner gearbox has incipient failure,its vibration signal,with hidden impulse component veiled by strong background noise,is usually very weak,which results in difficultly of gear fault diagnosis. In this paper,the concept of M-shift correlated kurtosis( KC,M) was introduced,and the method of maximum correlated kurtosis deconvolution（ MCKD） was derived.Firstly,estimate interest period T of deconvolution through calculating the maximum KC,Mvalue for the faulty signal. Then,select the appropriate M-shift for the maximum correlated kurtosis deconvolution. Finally,through envelope demodulation analysis to the MCKD filtered signal,the fault feature of root slight crack from gear 8（ Z8= 28） on the shaft V was successfully extracted. In addition,the MCKD method was compared to the method of fast spectral kurtosis. The application result and comparison analysis verify the effectiveness of the method of maximum correlated kurtosis deconvolution（ MCKD） applied to incipient fault diagnosis of gearbox.关键词：Rubber refiner gearbox;Fault diagnosis;Maximum correlated kurtosis deconvolution（MCKD）;Envelope demodulation
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发布时间：2022-09-22 -
ONBOARD FUEL PUMP FAULT DIAGNOSIS BASED ON IMPROVED SUPPORT VECTOR MACHINE AND EXPERIMENTAL RESEARCH
摘要：Aiming at solving lacking of failure data and inefficiency,high-cost of now available fault diagnosis methods,a experimental platform of fuel transfer system is developed and a fault diagnosis method based on wavelet packet analysis and improved support vector machine（ ISVM） is presented. Based on the vibration signal and the outlet pressure signal obtained from the airborne fuel oil system,the energy of different frequency bands of vibration signal extracted by wavelet packet decomposition can be regarded as characteristic parameters to structure fault feature vector as well as the mean outlet pressure. The genetic algorithm is presented to optimize the parameters of SVM. Meanwhile,the fault feature vectors are used to train and validate this classification model. The experimental results show that this method not only can improve the classification accuracy on fault diagnosis,but also can optimize the use of sensors by using only one vibration sensor and one pressure sensor to recognize the fault signals.关键词：Fuel pump;Experiment platform;Wavelet package analysis;Support vector machine;Genetic algorithm- 2
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发布时间：2022-09-22 - 摘要：In this paper,the single disk flexible rotor which is supported by the fixed-tilting pad journal bearings is studied,and the model of the rotor system is established by the rotor dynamics theory. The Reynolds equation is solved by the method of Castelli based on the dynamic Reynolds equation and the boundary conditions,at the same time,the oil film force data base of single pad is established in its coordinate system. Through the coordinate transformation,the oil film force of the fixed-tiling pad journal bearing is obtained by the assembly method. When the oil film force is calculated,two situations are considered,i. e.considering the inertia of the pad and neglecting the inertia of the pad. Firstly,the comparison of the rotor orbit is complemented at the two situations. Then,the dynamic behaviors of the rotor are analyzed at the situation of considering the inertia of the pad,and the comparison of pendulum angles of tilting pads and the orbits of the rotor are implemented at different preloads and pad pivot ratios.关键词：Fixed-tilting pad bearings;Nonlinear dynamics;Stability;Data base;Oil film force
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发布时间：2022-09-22 - 摘要：Mechanical running noise should be controlled in many occasions,the micro ＆ special motor system is one of these. Here,the mechanical analysis of the noise reduction plan of a kind of household vegetable spray system was investigated,the force balance equation was employed to deduce the relation between the suspension line deflection angle,the suspension line length,the moment of the resistance and other parameters,and the tension force of the suspension line was given; the methods and formulae of computing the spring stiffness coefficient and the weight were also obtained,an example was given to illustrate the variations of the moment of resistance and the spring stiffness coefficient to the suspension line deflection angle respectively,and the numerical iteration method was employed to compute the suspension line deflection angle with known moment of resistance,the results showed the feasibility of the method. The methods introduced here have significant conferences to further discussions on the system dynamic vibration and noise control.关键词：Suspension motor system;The spring stiffness coefficient;Deflection angle;Force balance equation;Numerical iteration
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发布时间：2022-09-22 - 摘要：Gear is a main component of the machinery transmission. Reducing gear failure and prolong its life is a crucial issue in industrial production. It summarized the research progress of gear fault diagnosis technology for nearly 50 years. The gear fault diagnosis methods are classified,mainly including the time domain method,frequency domain method,time-frequency domain method,the intelligent diagnosis method and oil detection. This paper elaborates their application example in the gear failure and analysis the characteristics and application example of gear fault diagnosis technology. It expounds several kinds of typical fault diagnosis technology and signal processing method in the modern application of gear fault diagnosis. Comprehensively reviewed the research status of signal measurement technology and the development. It summarized characteristics of modern gear fault diagnosis technology and pointed out the gear fault diagnosis technology in detail later. It will towards to the development of intelligent,diversification,efficient direction and provides the basic basis for the fault diagnosis of the gear system and test under the running state,to ensure the safe operation of the gear. The study of gear fault diagnosis technology has a certain significance.关键词：Gear;Fault type;Diagnosis;Signal processing;Status and development
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发布时间：2022-09-22 - 摘要：Corrosion medium such as CO2-Cl-causing corrosion pits in the pipe wall exist usually in the service environment of well tubing. These pits will become the fatigue source of the fatigue damage of oil tubing under cyclic loading. In this paper,tubing steel of 13 Cr used in oil well is selected as research object,and CO2-Cl- corrosive environment is selected for simulating the service condition of tubing. In the corrosive environment,fatigue experiments are performed on standard CT specimens to study crack propagation behavior of 13 Cr steel. Crack propagation rate of the 13 Cr steel under cyclic loading is measured in air environment,in Cl- environment and in CO2-Cl- corrosive environment respectively. The change of corrosion fatigue crack propagation rate under the three environment condition is carried out. With the observation of fracture morphology, the mechanism of corrosion fatigue failure of the 13 Cr steel in the CO2-Cl- corrosive environment is analyzed.关键词：Corrosion fatigue;Crack propagation;Cl-pitting;CO2 corrosion
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发布时间：2022-09-22 - 摘要：The plastic zone in crack tip influences life prediction result when using crack propagation method to predict fatigue life of spot welds. Most of the methods used to predict fatigue life don’t take plasticity into consideration. In this paper,TS specimen fatigue life of several high strength steels are tested and crack propagation method is used to predict theoretical fatigue life of TS specimen. Plasticity in crack tip is taken into consideration to modify the life prediction result. Predicted life in high cycle fatigue area barely change while life in low cycle fatigue area decrease after plastic modification. The modified life prediction result is in good agreement with experiment data. In high cycle fatigue area,plastic zone radium is small and has little influence on fatigue life because of low load. In low cycle fatigue area,plastic zone radium is big and influence life prediction result because of high load.关键词：Crack propagation;TS specimen;Fatigue life prediction;Plasticity
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发布时间：2022-09-22 - 摘要：Coal is the important basic energy in China,while the coal freezing adhesion seriously restricts with coal mine safe and efficient production in winter. Pressure as a secondary factor of coal freeze condition,it has an important influence on coal freezing adhesive strength. Through the freezing adhesive strength test device designed by ourselves,under conditions of- 25 ℃temperature and 3h freezing time,freezing adhesive characteristic of six different materials with moisture content 40% of the coal slime were tested. Studies have shown that pressure usually makes the coal freezing adhesive strength increase,such as Q235,normal freezing adhesive strength of under prepressure is 6. 2 times bigger than under no pressure’s,tangential freezing adhesive strength of under prepressure is 5. 9 times bigger than under no pressure’s. But only PTFE’s normal and tangential freezing adhesive strength under the condition of pressure both do not increase among six materials. In a sense,pressure will increase the hydrophilic material freezing adhesive strength,instead it will reduce the hydrophobic material freezing adhesive strength. The excellent characteristic of PTFE material shows wide application prospect in cold area of coal transportation,it deserves further study.关键词：Coal;Freezing adhesion;Pressure;Q235;PTFE
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发布时间：2022-09-22 - 摘要：Gear transmission system is a series system. However,it is different from the traditional series system in many aspects such as the relationship between system and elements,the manner for the system functioning,the time-dependent system configuration,etc. System classification is discussed firstly to meet the demand of system reliability modeling. For the purpose of system reliability analysis,a gear transmission system is taken as a time-dependent varying configuration system,which is different from the traditional series system with changeless configuration in space. According to different function,different configuration and different load characteristics,specific system oriented reliability analysis and modeling method are studied.Taking simple gear transmission system as an example,several system reliability models are developed,the reliability variation with load number and the differences between the new model and traditional model are illustrated.关键词：Reliability;Gear transmission system;Series system in time domain;Non-constant series system
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发布时间：2022-09-22 - 摘要：According to the problem of structural dynamical topological reanalysis for continuous two modifications,a new method for dynamic reanalysis of topological modified structure with added degrees and two continuous modifications was proposed in this paper,which is combined independent mass orthogonalization strategy with Rayleigh-Ritz analysis and the coupled condensation method. Comparing with the direct finite element analysis（ FEA）,the high computational effort for FEA is greatly decreased by utilizing the proposed reanalysis procedures,which is also easy to operate and implement. The numerical example shows that the proposed method for dynamical topological reanalysis of continuous two modifications is effective.关键词：Twice continuous modifications;The coupled condensation;Dynamical topological reanalysis;Mass orthogonalization
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发布时间：2022-09-22 - 摘要：which the singular element appears in the optimum process and the result may be a partial optimum solution are two disadvantages when using the ESO method to optimize 2- D model. In this paper,two algorithms are proposed for solving these disadvantages. One is filter and rejection algorithm based on the trait of singular element. Using this algorithm,only one parameter is needed to control filtering and deleting,and the parameter is determined by the number of elements linked around singular element. The other is interval approximation algorithm. Minimum initial rejection rate R0minwhich fulfill removed conditions was ascertained by using this algorithm and it was used as starting value,thus other initial rejection rate R0 were obtained by setting certain increment. Two algorithms mentioned above were implanted in the existing ESO method,then optimizing respectively with different initial rejection rate which were obtained before and the available structures from the results was filtered out in terms of performance parameters. The results of optimization for numerical 2-D structures indicate that the improved ESO method has better suitability and stability than the existing one,and it avoids shortcoming that the result may be a partial optimum solution when using the existing ESO method.关键词：Topology optimization;Evolutionary structural optimization;Singular element;Finite element
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发布时间：2022-09-22 - 摘要：To solve the large computation and low efficiency of stress approximation in structural topology optimization with stress constraints,a method of the first-order approximation of internal force is put forward to express explicitly stress constraints.And the comparison with the full stress method（ that is,the zero-order approximation of internal force） and the first-order approximation of stress with reciprocal variable is carried on. Their advantages and disadvantages,and their effect on the solution efficiency are studied. To illustrate and analysis clearly iterative history data of the design variables,the objective function and constraints for different methods of stress constraint approximation during the optimization process,the design variable linking technology is adopted to reduce the number of design variables in topology optimization examples with stress constraints. The results of the topology optimization show that the first-order approximate of internal force is better than full stress method and the first-order approximation of stress with reciprocal variable. The number of iterations is the least. The solution efficiency is the highest. The optimal structure is the lightest.关键词：Structural topology optimization;Stress constraint;Stress approximation;First-order approximation of internal force;Full stress method
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发布时间：2022-09-22 - 摘要：The dynamics modeling of Delta parallel mechanism is established by using of Kane’s equation,and dynamics equation is expressed by simple generalized active force and inertial force. The maximum of joint driving torque in the whole program space is regarded as the global performance indices to quantify the dynamics performance of mechanism,meanwhile requirement of program space is treated as constraint of structure parameter. Dynamics performance of the mechanism is optimal based on the performance index,and both demand of programming space and dynamics performance are considered. Be the performance index as the multiple functions of structural parameters,quantitative the direction and magnitude of performance index variation with the aid of sensitivity,in order to avoid the blindness of the process. Performance index is not sensitive to parameter perturbation,good for the body to maintain its excellent raw performance for a long time.关键词：Parallel mechanism;Dynamics Performance;Optimal design;Programming Space;Sensitivity
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发布时间：2022-09-22 - 摘要：Multi-state system reliability is very important for complex systems which have a range of performance levels from perfect functioning to complete failure. The research works on reliability optimization of multi-state system promote the applications of multi-state system reliability. The paper provides a broad overview of recent research on reliability optimization of multi-state system,and discusses the further research directions. In particular,six issues are analyzed: redundancy allocation problem,maintenance / redundancy allocation problem,optimal allocation of elements,optimal reliability enhancement,multiobjective optimization,and optimization algorithms. The further research can be focused on fuzzy reliability optimization,reliability optimization in the presence of dependent failure,reliability optimization based on RAMS + C,and so on.关键词：Multi-state system;Reliability optimization;Universal generating function;Multi-objective optimization
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发布时间：2022-09-22 - 摘要：Two 3D finite element approaches for unidirectional hybrid composites were built to represent failure process in scales of individual fiber and fiber tow,respectively. The first scale approach was defined as iso-type fibers and epoxy composed fiber tow in which micro damages concerned including failures of individual fiber,matrix and fiber / matrix interface. The second scale approach assembled with different type fiber tows. In this scale,failure regularities of tow and interface between adjacent tows were considered and the former was obtained from first scale model. Cohesive zone model was used to simulate the damage and failure of component materials,this method could reflect the distribution and propagation of the crack in composites. Explicit FEM was used for both the two scale models to characterize the impaction of energy released from the broken fiber or tow. Weibull type distribution was used to describe strengths of fiber and fiber tow in the two scale approaches for charactering the randomness of failures. The two scale approaches were employed to simulate the progressive failure of carbon / glass fiber hybrid unidirectional composites under tensile load. Two distribution patterns of carbon tow in hybrid composites,i. e. coaxial and dispersed were taken into account,meanwhile for each pattern different volume ratio of carbon fiber and glass fiber was considered. The study reveals that when volume fraction of carbon tows is equal or less than 10% the second damage phenomenon is obvious,meanwhile the critical elongation and strength for coaxial hybrid composited are slightly bigger than those for dispersed one. Otherwise,the two patterns hybrid composites behave in brittle way and little discrepancy between their strengths has been found.关键词：Hybrid composites;Finite element analysis;Cohesive zone model;Weibull distribution;Tensile behavior
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发布时间：2022-09-22 - 摘要：In measurement of interlayer stress between cylindrical or spherical contact convex-concave interfaces with related big curvature,the flat sensitive element will be curved to the form of the measured contact surfaces,which can cause measurement errors. This issue must be considered in developing sensors applied to measuring such kind of contact interfaces stress. For this application background and taking the cylindrical contact interfaces issue as an example,a finite element model consisting of a loading part with a convex cylindrical surface,a soft piezomagnetic sensitive material sheet,and a fixed part with a concave cylindrical surface is developed by using the approximate numerical method for analyzing combined structure with soft foam parts suggested previously by the author. Through numerical computation and related experiment,the axial compressive stress-strain curves of the sheets are obtained for several different curvatures of the loading surfaces and the effects of curvature on mechanical behaviors of piezomagnetic material sheets were analyzed. It is indicated that the bigger the curvature radius of the loading surface is,the bigger the slope of the approximate linear segment of the axial stress-strain curve is. The result is useful for development of sensors for measurement of interlayer pressurized force between cylindrical or spherical contact interfaces with related big curvature.关键词：Contact surface curvature;Soft piezomagnetic sensitive material;Mechanical properties;Sensitive element of sensor;Cylindrical contact interfaces pressure sensor
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发布时间：2022-09-22 - 摘要：Stair-climbing function of Micro Mobile Robot（ MMR） conflict with their portability. The Beijing Institute of Technology has developed a four-wheeled MMR which can climb stairs by flipping chassis. This robot weights 2. 5kg,so it is portable and can be deployed by throwing in short distance. In allusion to that robot,three concerns as well as assessments in dropping process have been put forward. The hyperelastic model of rubber and elastic-plastic model considering strain rate of metals were established,and a finite element model（ FEM） was established with ABAQUS furthermore. The FEM was tested on three typical working conditions of dropping horizontally,vertically and side-vertically by 1m height. Problems of the original structure were discussed and optimization measures were put forward,concerning tire,shell and motor shaft and so on.Simulation experiments have been done to confirm the validity of those measures. The results show that the dropping resistance is improved,and the optimized structure can sustain drops of 3 m.关键词：Micro Mobile Robot;anti dropping impact;hyperelastic;elastic-plastic
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发布时间：2022-09-22 - 摘要：To study frictional contact problem between rubber tube and the casing,The friction coefficient is measured with Vertical universal friction and wear testing machine that type is MMW- 1. Based on Mooney-Rivlin model of rubber material,using the principle of penalty function and coulomb friction and Combining with rubber nonlinear large deformation problems,the frictional contact problem of Rubber tube and casing is analyzed by the finite element with measured data. The results shown that the friction coefficient of contact is the maximum and 0. 514 in the absence of lubricant,the minimum and 0. 122 under oil lubrication,and others is 0. 122 0. 514. With the increase of friction coefficient,friction stress increase gradually,but the contact pressure decrease as a whole. Equivalent stress of rubber tube first increases then decreases. When friction coefficient is0. 3,contact pressure can be better. With the increase of axial loading,contact pressure,friction stress and the equivalent stress of packing element increases gradually. Keep axial loading,the width of rubber tube has greatly influenced on contact problem.Finally,the structure of rubber tube has been optimized to obtain a better structure which is entire circular arc.关键词：Rubber tube;Friction coefficient;Equivalent stress;Numerical simulation
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发布时间：2022-09-22 - 摘要：In order to evaluate the impact process induced by uncontained failure,numerical simulation for one-third HPT（ High Pressure Turbine） disk impact was carried out under different obliquity angles and residual fuel volumes in the wing structure. The study,which resulted in continuous dynamic response,focused on the interaction among debris,turbine cowl and integral fuel tank. The constitutive material mode and failure criteria proposed by Johnson-Cook were applied in solid element definition,while SPH（ Smooth Particle Hydrodynamics） model was used for fuel particles. The analysis involved the debris velocity history,fuel tank deformation along with the stress distribution changes during the whole process. It is shown from the results that with the increase of obliquity angle and residual fuel volume, the velocity loss and energy reduction rise correspondingly. The turbine cowl absorbs most of the debris energy while fuel also contributes to the absorption due to its viscidity. Hydrodynamic ram fails to cause lethal destruction of the tank structure under large debris impact. In the last part,fuel tank boundary design has been discussed qualitatively according to the simulation results.关键词：Uncontained failure;Large engine debris;Turbine cowl;Integral fuel tank;Numerical simulation
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发布时间：2022-09-22 - 摘要：The mechanical model of meshing pair was built. Force of two meshing pairs and turning arm bearing were analysed. The contact stress of hypocycloid and epicycloid tooth surface was deduced with Hertz theory. Their stress change curves were drawn with different tooth number. The results show that the contact stress decreases when the tooth number increases. And,the maximal contact stress presents to the inner tooth surface of hypocycloid groove. Real example is built and the maximal contact stress is calculated by Matlab. This research provides important theory basis for the design application of the cycloid ball planetary transmission.关键词：Two-stage;Cycloid ball planetary transmission;Stress;Strength;Meshing pair
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发布时间：2022-09-22 - 摘要：Althought Simple jack-up type intelligence stereo parking space to ease the parking problem in public,its bedplate frame occurred deformation in the process of rising. reduced stereo parking space stability,shorten the working life of the stereo parking space. Deformation of the frame belongs to the nonlinear structure problem. First established the mechanical model framework to solve the deformation of frame,and caculated the overturning moment,bearing force,the strength of the frame.Second using finite element analysis software ANSYS-workbench module to the rotary column in the 0°and 90°two condition of the framework for the calculation of mechanical property simulation,in order to obtained the deformation amount,the deformation direction the principal stress and the maximum stress position under the two conditions. Finally,the deformation test of the sample machine with software of test system. According to the test result validates the mechanical model,according to the analysis result showed the problems,and proposed frame suggestions for improvement,provided an important reference value to improve the stereo parking space stability.关键词：Stereo parking space;Framework;Mechanical model;Workbench;Mechanical analysis
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发布时间：2022-09-22 - 摘要：RNGk-ε turbulence model was chosen to analyze the defrosting of automobile front-windshield. To research the influences of computational domain on simulation results,the front B-pillar part of cabin and full-scale crew cabin models were established respectively. The both models contained the driver,passenger and seats to ensure accuracy. During the simulation,the driver and passenger were considered as heat sources. The results show that,simulation convergence time of full-scale crew cabin increases 44% than the front B-pillar cabin’s,but two models’ differences in air flow distribution and steady wind speed are very small. Besides,there are obvious differences in average temperature of windshield and liquid fraction of frost layer. In transient simulation of defrosting,the full-scale crew cabin is better compared with the experiment. In addition,the simulation results of full-scale crew cabin can reflect the temperature of driver’s breath point accurately. Therefore,the forward B-pillar of crew cabin can be used to study the air flow distribution of defrost duct. But when studying defrosting transient effect or evaluating automobile’s thermal environment,it is necessary to establish full-scale crew cabin model to get accurate results.关键词：RNGk-ε turbulence model;Front-windshield;Defrosting;Computational domain
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发布时间：2022-09-22 - 摘要：In order to solve the problems of much heat during braking process,and poor stability in high speed condition of the automobile wet brake,a new type of wet brake based on the layout of real time temperature control was proposed by analyzing the working principle of the layout scheme,a new type of wet brake model was established,finally,the feasibility of the new type wet brake was verified by the bench test method. The theoretical calculation and experimental verification show that both results are consistent basically,the brake torque fluctuation of the wet brake based on the real-time temperature control system are obviously suppressed,and the brake torque stability of the brake process is obviously improved,and the brake torque of each stage is large than the traditional wet brake; the coolant temperature of the wet brake based on the real time temperature control system can be controlled in the vicinity of 70℃,which has a positive effect on improving the performance of the automobile brake system.关键词：Wet brake;Temperature control system;Real time;Brake torque;Coolant temperature
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发布时间：2022-09-22 - 摘要：The relationship between the size of inner diameter of induction heating coil and induction heating result was analyzed based on the transformer series equivalent circuit model of induction heating coil,the data of induction heating result under different inner diameters were calculated by using finite element model,they were processed by using polynomial fitting method to get the best fit polynomial,the change law of the data was reflected. The result shows that the relationships between the temperature difference between center and surface,power and the size of inner diameter present a decreasing trend,the relationship between the heating time and the size of inner diameter presents a increasing trend. The inner diameter optimization model was established based on the best fit polynomial,the optimization model was solved by using genetic algorithms,the optimal solution of inner diameter is 49. 15 mm,it provides a theoretical basis for induction heating coil optimized design.关键词：Steel strand;Induction heating coil;Structural parameter;Finite element analysis;Genetic algorithms
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发布时间：2022-09-22 - 摘要：Bending deflection is the main form of welding deformation,which is liable to occur in the Y-joint. Therefore,this paper investigated the strain distribution of Y-joint under the tensile test with digital image correlation（ DIC）. The study results showed that the strain distribution on the groove angle bisector is in approximate linear. On the inner side of groove angle bisector,the compressive strain is the largest,and on the outside of groove angle bisector the largest strain is tensile strain. The strain concentration is occurred in the groove area,however,the strain distribution curves are different with the areas. In order to reduce the strain concentration,the welding specimen was treated by annealing and the results showed that the strain distribution is more uniform compared with no annealing processing.关键词：Welded joint;Digital image correlation technology;Bending deflection;Strain concentration
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发布时间：2022-09-22 - 摘要：The fatigue life scatter factor is an important reliability index of the assessment of aircraft fatigue life. At present,the safe-life of a fleet is gotten by using the total test hours and the fatigue scatter factor. Usually,the environment scatter factor caused by the different service environments is not considered,and the fatigue scatter factor mainly includes two parts,one is the load scatter factor caused by the load spectrum difference of fleets; the other is the structure scatter factor caused by the difference of material and manufacturing quality. The expressions of scatter factor of fatigue life obeying the log-normal distribution and Weibull distribution are introduced and analyzed. To the situation that the structure fatigue life of the same aircraft model under different load spectrums obeys the log-normal distribution,the condition that the fatigue scatter factor is the product of the load scatter factor and the structure scatter factor is deduced. To the situation that the structure fatigue life obeys the different distributions,the service flying hours can be converted into the equivalent flying hours under the same test load spectrum based on the equal damage principle,the structure scatter factor under this spectrum can be calculated and can be taken as the fatigue life scatter factor,the safe-life calculated by this scatter factor can be seen as the reference value for the management of individual aircraft life.关键词：Aircraft structure;Fatigue life;Scatter factor;Log-normal distribution;Weibull distribution
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发布时间：2022-09-22 - 摘要：Bolt holes take place fracture on air compressor bearing of a dry mortar truck,it leads to bolt are easy to be pulled out. Because of the special structure of air compressor,air compressor bearing bolt holes are exerted on dynamic load,the dynamic load is difficult to directly get in the test. Uses the dynamics simulation software adams,the coupled model is set up,use spring replace bolts,to simulation analyze the stress of the bolt,Finally get the tensile force of the bolt holes,and determine the cause of the bolt holes occurred fracture. Results show that the maximum tensile stress on the bolt holes are more than tensile strength,resulting in bolt holes occurred fracture.关键词：Bolt holes;Dynamic;Bolts;Simulation
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发布时间：2022-09-22 - 摘要：ASME NH high-temperature design code put limits on inelastic strain. However,there are several arguments about this provision. For instance,the multi-axial effect and different design margins for different materials were not considered.In this paper,a 316 stainless steel 90°elbow at 550℃ was simulated to study impact of multi-axial effect on creep design strain margin. A continuum damage constitutive model was used,also new damage variables were defined based on multi-axial creep ductility theory. These damage variables were investigated when strains of the elbow reached corresponding limits in order to judge whether ASME NH strain limits are conservative. It is shown that all the damage variables are well below unity when the membrane strain of the elbow reaches the strain limits of 1%. It is thus concluded that ASME NH strain limits is still conservative when multi-axial effect is considered in a 316 stainless steel structure and can be used for design and verification at this temperature.关键词：316 stainless steel;ASME NH;Multi-axial effect;Strain linerization;Creep ductility
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发布时间：2022-09-22 - 摘要：Strengthening problem of short-edge hole of titanium lug is an important task during a new aircraft development stage,Force Mate steel bushing process has been carried out to study the fatigue life of short-edge hole. Research the interference of 0. 5% 、1. 0% 、1. 5% 、2. 0% 、2. 5% how to effect the stress and strain around the hole with FEA,and comparisons with shortedge hole and normal hole are made as well. Then apply a cycle load on the lug to predict the fatigue life and provide a theoretical guidance for the optimum technology parameter.关键词：Short-edge hole;Steel bushing;Interference-fit;Fatigue life
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发布时间：2022-09-22 - 摘要：J integral of elastic-plastic curved crack in hardened material under quasi-static loads has been mainly studied,and curved crack tip J integral has been calculated as a practical application of a second order perturbation method and theorem of surname KA,where the effects of quasi-static applied stresses and quasi-static normal and shear stresses on the boundaries of plasticity area are synthetically taken into considerations. Diagrams have been constructed to analyse the transformation relationships between curved crack J integral and hardening exponents. Curved crack J integral will decrease when hardening exponents increase in hardened material. Curved crack J integral decrease extent will be more and more severe when hardening exponents increase evenly. Curved crack J integral will decrease when external loads decrease with the same hardening exponents. A theoretical model where J integral of elastic-plastic curved crack was calculated has been established in hardened material.关键词：Quasi-static loads;Hardened material;Curved crack;A second order perturbation solution;J integral
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发布时间：2022-09-22 - 摘要：Based on the ANSYS software,this paper puts forward an accurate simulation method of applying the bolt pre tightening force to the interference fit joints of high locked bolt. By considering the bolt interference fitting,the bolt pre-tightening force,etc,the 3D finite element elastic-plastic model of the aircraft typical joint was established. The effect of the different plate friction on the maximum von mises of the dangerous part of the joint was calculated,and the variation law of the two points strain value was analyzed,then it was concluded the reason why the maximum von mises of the dangerous part of the joint changed. The result shows that with the increase of the coefficient of friction between plates,the maximum von mises presents the first decrease then increase. And this is due to the friction force between the plates on the load transfer and the upper and the lower free end of the joint tilted outward. The results of the analysis can provide reference for the finite element analysis and durability design of such joints.关键词：Joint;Friction between the plates;Pre-tightening force;Finite element analysis
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发布时间：2022-09-22 - 摘要：Designing large-span and micro-deformation load bearing crossbeam for the vertical loading force. the designing span of Crossbeam is 3422 mm. Horizon displacement is 1100 mm. Reruirement crossbeam’s deformation amount less 50 μm.when loading vertical force in the destination of working plane. Using the steel with the thickness of 16 mm as the main material,imitating I-steel’s strong compressive behavior and equal intensity beam anti-deformation ability to design coincidence working condition’s non-standard microdeformation and soft Weight crossbeam,making it to reach design deformation amount and allowable stress by ANSYS Workbench. Using the crossbeam’s total deformation and equivalent stress tiny as the objective function,imitating I-steel and equal intensity beam’s key structures which is P3,P4,P5,P6 as the design variable to optimize the crossbram structure. Through the vertical loading force experimental analysis for non-standard crossbeam,the system maximum deformation is 38 μm when the loading force is 10 k N,ANSYS Workbench solving is 40 μm,the relative error is 5% of them,crossbeam meets the conditions required by optimization.关键词：Micro-deformation beam;Vertical loading;Response surface;Structure optimization
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发布时间：2022-09-22 - 摘要：The surface roughness data of test-pieces with transverse profiles were firstly measured by a roughness profile measuring analyzer. With the help of the Fourier nonlinear approximation the measured data were used to form a roughness function which was superimposed to film thickness equation and a mixed thermal elastohydrodynamic lubrication model was then established. Based on the model,280 sets of numerical calculations were carried for both medium and heavy duty transmissions through changing the roughness values. The results show that the contact stress τmax,rfor rough teeth surfaces is increased by 5%compared with the contact stress τmax,sfor smooth teeth surfaces when the root mean square roughness of tooth surface σ≤0. 3μm; While the τmax,ris increased by 15- 20% compared with the τmax,swhen σ ≥ 0. 5 μm. At the end,several theoretical formulas for determining the roughness factors are created based on the multiple regression analysis of the above calculated results.关键词：Gear transmission;Contact stress;Transverse rough features;Roughness factors
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发布时间：2022-09-22 - 摘要：If the hoisting position is bad during the engineering application of the lifting pipe,which may bring the serious influence when the pipe smoothly enters the grave,even happen stuck pipe and tube flat accidents. Through the mechanical analysis of the pipe lifting,themathematical model about lifting point position and the grave angle was established,which on the basis of reasonable assumptions. The location of the lifting point 2 affects on the size of the grave angle more than lifting point 1by mathematical model analysis. And then compared with the calculated value of mathematical model and the value of test measurement,the relative error of theoretical calculation value and experimental value that is about 5. 8% was discovered.Therefore,the mathematical model can be used to guide the actual construction.关键词：Directional crossing;Lifting point;Pipe;Grave Angle
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发布时间：2022-09-22 - 摘要：The structure of connecting point between a large acrylic sphere and stainless steel truss outside was designed preliminarily,and its loading capacity was verified by finite element method using ABAQUS software. Multiple nonlinear problems involved in the FE model was simulated,and stress under different boundary conditions was compared. But results of loading experiment of preliminary structure did not reach expectations. Then preliminary structure of connecting point is improved,in accordance with the result of loading experiment,and loading capacity of improved structure was verified. Finally,testing results of loading experiment of improved structure was in line with expectations and met well with results of FEA.关键词：Jiangmen underground neutrino observation（JUNO）;Connecting point;Nonlinear finite element analysis;Model experiment
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- 100
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发布时间：2022-09-22 - 摘要：To establish a rigid modle and a rigid-flexible coupling model of the transmission system of a coal winning machine haulage part,based on the theory of non-linear contact theory and multi-body dynamic. Applying ANSYS software to the rigid gear of flexible,and importing the model into the multi-body dynamics software RecurDyn for simulation analysis. The gear meshing process was described intuitively and dynamically under the simulation animation environment,and according to the simulation results to optimize the transmission system. The comparison of the simulation results of the rigid modle and a rigidflexible coupling model showed that the dynamic performance of rigid-flexible coupling model is more consistent with the actual.The problems of a large mechanical transmission mechanism’s multi-body contact simulation were solved,the theory laid the foundation for the applications of gear multi-body dynamics model in engineering.关键词：Gear transmission;Non-linear contac;Multi-body dynamic;RecurDyn
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发布时间：2022-09-22 - 摘要：A new parallel symmetric mechanism that can get greater output force was introduced in this article,which was composite of the lever force increasing mechanisms bearing a length effect and the toggle force increasing mechanism based on an angle effect. The working principle of the mechanism was explained in detail,meanwhile,the mechanical analyses were carried out and the characteristic curves were drawn. Finally,the application of this mechanism was given. The mechanism was simple and high-efficiency because it was parallel in construction and function in series.关键词：Double working positions;Toggle mechanism;Lever mechanism;Fixture;Punch
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发布时间：2022-09-22 - 摘要：This paper presents a bicycle saddle height adjustable system,which makes saddle lifted fast. The new system is based on the traditional structure of the bicycle,locates a rigid lockable gas spring under the saddle. Through the gas spring mathematical model,with MATLAB software,obtained the relationship between speed and reaction time,and the displacement curve. Analyzed these variable relationship had made a conclusion that gas spring does it well in lifting the saddle.关键词：Bicycle;Gas spring;MATLAB;Saddle
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发布时间：2022-09-22
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