最新刊期
期 3 ， 2019
- 摘要：Screw drive is widely used in the focusing mechanisms in space cameras, and the self-locking ability is required to resist the shock and vibration in the process of launching. The paper establishes a non-linear simplified mechanical model of thread fit clearance with two degrees of freedom. The dynamic response of the system under the vibrating inspiration is achieved by numerical simulation method. The result shows that non-dimensional kurtosis indexes can be used as an indicator to evaluate the degree of self-locking failure of screw drive. Finally, The simplified model is verified by finite element simulation analysis, and it shows kurtosis indexes is effective to analyze the influence of thread fit clearance on self-locking ability.关键词：Screw drive;Focusing mechanism;Fit clearance;Self-lock;Kurtosis indexes
- 4
- |
- 333
- |
- 3
发布时间：2022-09-22 - 摘要：To multi-faults of a gearbox, the strong fault feature vibration of gearing always interfered with rolling element bearing weak fault vibration. The traditional methods are difficult to extract the weak bearing fault feature. In order to solve the problem, a vibration analysis scheme for multi-faults vibration of gearbox based on discrete random separation（DRS） is proposed. In the proposed method, the resonance parameters of the gearbox vibration is obtained based on the fast kurtogram algorithm at first, built a bandpass filter that included resonance parameters, and the envelope is extracted by Hilbert transform. Then, converted envelope to the angle domain based on the equi-angle increment resampling to remove speed fluctuation. Next, the SANC is performed to separate the envelope in the angle domain. As a result, the gear fault corresponding envelope component and the bearing fault related envelope component are obtained; Finally, the spectrum analysis is carry out on the two envelope components respectively for the fault diagnosis information. Test results show that this method can be used to extract the gear and bearing fault features effectively.关键词：Multi-faults;Gear;Rolling element bearing;Discrete/Random separation;Envelope analysis
- 6
- |
- 302
- |
- 1
发布时间：2022-09-22 - 摘要：Aimed at the difficulty in identifying the equivalent stiffness of rotor bearing joint, an equivalent stiffness identification method of combining finite element modal analysis, experimental modal analysis and back propagation neural network was proposed. Firstly, the finite element model analysis of a rotor bearing system was built with the Abaqus, and the respective natural frequencies were obtained. Secondly, the first four bending natural frequencies of the rotor bearing system were acquired with experimental modal analysis. Finally, the equivalent stiffness and natural frequencies were trained and identified by BP neural network. Research results showed that the maximum relative error of the radial and axial equivalent stiffness identification of the rotor bearing system were 1.75% and 5.43% respectively. The research work provides a reference for parametric identification on mechanical structure joint.关键词：Rotor bearing;Joint;Modal;BP neural network;Equivalent stiffness
- 4
- |
- 236
- |
- 2
发布时间：2022-09-22 - 摘要：In order to diagnose fault effectively by using sensitive features contained in the feature set, KFDA was improved in this paper and a fault diagnosis method based on improved KFDA individual feature selection was proposed. Firstly, the mixed feature of the fault vibration signal was extracted from different angels, and the original high-dimensional and multi-domain feature set was constructed. Then, an improved kernel Fisher feature selection method was proposed and used to select individual sensitive feature subset for each pair of class. Finally, a one-against-one approach was applied to train several relevance vector machine（RVM） binary classifiers, and sensitive feature was input into the multi-class fault diagnosis model for recognizing the fault types. The experimental results of gear indicate that the proposed method is of high diagnostic accuracy.关键词：KFDA;Individual feature selection;Fault diagnosis;Gear
- 4
- |
- 101
- |
- 5
发布时间：2022-09-22 - 摘要：Rolling bearing as a key component of rotating equipment, its performance seriously affect the safe operation of the equipment. As the equipment condition is complex, the impact component of the fault feature is often submerged by the noise signal, therefore the fault feature cannot be extracted effectively. A method was proposed based on improved complete ensemble empirical mode decomposition with adaptive noise（CEEMDAN） and kurtosis index by this paper. Firstly, the improved CEEMDAN method is used to add adaptive white noise to each signal in the decomposition process, a unique residue was computed to obtain each intrinsic model function（IMF）, compared with ensemble empirical mode decomposition（EEMD）, the decomposition is complete. Secondly, the kurtosis index is calculated of each IMF to select the reconstructed IMF component and the kurtosis index is used to select the most suitable reconstructed signal. Finally, the bearing fault feature is obtained by envelope demodulation. The results confirm that this method has better decomposition effect, better adaptability and highlight the impact of the bearing fault.关键词：CEEMDAN;Kurtosis;Signal reconstruction;Rolling bearing;Fault diagnosis
- 3
- |
- 459
- |
- 4
发布时间：2022-09-22 - 摘要：This paper based on nonlinear rectangular thin plates with butt welding residual stress as the research objects. According to the theory of nonlinear vibration, It has study the influence of the welding residual stress on the natural frequency and the maximum value of amplitude in nonlinear component and explain that the parameters of VSR in theoretically. In addition, It’s obtains that the relationship between maximum amplitude and the natural frequency with steady-state response of nonlinear rectangular plates is nonlinear variation according to the welding residual stress. The conclusion is that maximum amplitude is reducing as the welding residual stress increasing, the natural frequency is reducing with the welding residual stress reducing.关键词：Welding residual stress;Nonlinear;Rectangular thin plate;Natural frequency;Maximum value of amplitude
- 3
- |
- 123
- |
- 1
发布时间：2022-09-22 - 摘要：In order to make accurate diagnosis for the scraper conveyor speed reducer failure study. This paper proposes a improved firefly algorithm to optimize neural network based fault diagnosis method. Firstly, the characteristics of the fault characteristic parameters of the blade conveyor are extracted. The second application feature data sample for fault diagnosis model based on neural network training. Using the improved firefly algorithm to optimize neural network weights and threshold, to speed up the optimum value of, get the optimal model of the network. Preliminary studies suggest that the improved firefly algorithm combined with BP（back propagation） neural network can effectively solve the neural network slow convergence speed, easily falling into the master problem, can make accurate diagnosis for the failure of scraper conveyor speed reducer.关键词：Improved firefly algorithm;BP neural network;Fault diagnosis;Scraper conveyor;Reducer
- 3
- |
- 404
- |
- 3
发布时间：2022-09-22 - 摘要：The three-layer constrained damping structure is often used in the design of vibration and noise reduction for engineering structures. A "transition layer" can be added in the middle of the viscoelastic layer and the base layer to form a new kind of constrained damping structure with transition layer in order to increase its anti-vibration performance. Based on the first-order shear deformation theory and Hamilton principle, the finite element model is established, and the corresponding vibration and damping characteristics are analyzed. In order to verify the correctness of the model, the two results are in good agreement compared with the analytical solution. Taking the cantilever damping beam as an example, compared with the traditional constrained damping beam, the calculation results show that adding the "transition layer" can improve the loss factor of the structure and energy consumption. At the same time, the material of the transition layer selection and influence of its parameters on the natural frequency and the loss factor of the system are discussed, which lay a good foundation for further optimization and engineering practice.关键词：Constrained damping beam;Transition layer;Finite element method;Damping characteristic
- 4
- |
- 139
- |
- 0
发布时间：2022-09-22 - 摘要：Reciprocating compressor vibration signal is typical nonlinear and non-stationary,and the vibration information interference coupling, owing to this problem,a fault diagnosis method of reciprocating compressor on the resonance-based sparse signal decomposition with optimal Q-factor was proposed.The method use resonance sparse decomposition to find the low resonance component which its kurtosis is maximum, optimize Q-factor with genetic algorithm and particle swarm optimization to get the optimal Q-factor;then use resonance sparse decomposition to decompose reciprocating compressor vibration signal by the optimal Q-factor;the result shows that this method can diagnose the oversized bearing clearance fault effectively.
- 3
- |
- 248
- |
- 2
发布时间：2022-09-22 - 摘要：Crack is one common damage in key cantilever beam structures and early crack identification is much significant for increasing safety and reducing accidents. However, classical methods based on displacements are less sensitive to small cracks. By introducing the concept of vibration power flow analysis, a vibration power flow model of a cantilever beam with a breathing crack is proposed in this paper. Then the simulations are performed to explore the effects of the depth and location of the crack on instantaneous dissipated and input powers, and sub-/sup-harmonic responses due to small crack are observed. The results demonstrate that the proposed method is much sensitive to small cracks than classical methods and provides a new way of detecting early cracks.关键词：Breathing crack;Cantilever beam;Vibrational power flow;Nonlinear vibrations
- 4
- |
- 243
- |
- 1
发布时间：2022-09-22 - 摘要：In order to improve diagnosis accuracy of support vector machine（SVM） in mechanical fault diagnosis, fruit fly optimization algorithm was improved and a fault diagnosis method based on SVM optimized by improved FOA was proposed. In improved FOA（IFOA）, history location information was introduced when fruit fly update its location, thus improved diversity of fruit fly group and the ability of jump out local optimum and better parameters of SVM can be obtained and classification performance of SVM was improved. Gear fault diagnosis experiment results validated that IFOA improved the identification accuracy of SVM and has a certain superiority when compared with some other methods.关键词：Improved fruit fly optimization algorithm;Parameters optimization;Support vector machine;Fault diagnosis
- 3
- |
- 386
- |
- 4
发布时间：2022-09-22 - 摘要：In order to better identification the degradation state of bearing, a degradation state feature extraction method for bearing named LCD-Hilbert relative spectrum entropy is proposed based on relative entropy for characterizing the probability distribution difference among different signals. The analysis results of simulation signal demonstrate the availability and relationality of the proposed LCD-Hilbert relative frequency energy spectrum entropy（LHFE）, relative instantaneous energy spectrum entropy（LHIE） and relative singular spectrum entropy（LHSE） used as degradation feature. The degradation feature vector is composed of the three features. The practical vibration of bearing with inner race fault and outer race fault which in different degradation state are analyzed, and the support vector machine is further used to identification degradation state and the results demonstrate the ability of the proposed method.关键词：LCD-Hilbert;Relative entropy;Feature extraction;Bearing;Degradation state
- 3
- |
- 68
- |
- 0
发布时间：2022-09-22 - 摘要：In order to improve fault diagnosis effect of bearing used in NC machine, a fault feature extraction and diagnosis method of bearing based on LCD multi dispersion entropy was proposed. The vibration signal was decomposed adaptively with local characteristic-scale decomposition（LCD） to obtain the components in different scales of the original signal. Considering the ability of the dispersion entropy in distinguishing the complexity of different signals effectively, the dispersion entropy of intrinsic scale components（ISCs） by LCD was calculated. Thus the complexity metric in different scales of the original signal was gained, which was consequently taken as the feature parameter to describe different bearing states. The feature parameters were then put into SVM for diagnosing the bearing faults. Bearing different fault type and different fault degree diagnosis results show that the proposed method can improve diagnosis effect and has certain superiority when compared with some other methods.关键词：LCD;Multi dispersion entropy;Feature extraction;Fault diagnosis;NC machine
- 3
- |
- 295
- |
- 1
发布时间：2022-09-22 - 摘要：In order to obtain the properties of 2219 aluminum alloy welding joint, this work uses digital image correlation（DIC） method, then the whole strain history within the welding zone of 2219 aluminum alloy friction stir welded joint subjected to tensile load is obtained, which in turn facilitates a continuous yield strength curve for the welding zone. The elastic-plastic constitutive equation is employed to describe mechanical properties of the welding zone with its parameters determined by the measured strain history. Then, the relationship between the distances from any location to the weld zone center and parameters in the equation can be established by fitting. Finally, a numerical simulation of welding joint subjected to tensile load is conducted using the mechanical properties given by the obtained relationship. The simulation results agree well with the experimental data. Therefore, it is proposed that the mechanical properties of the welding zone in a welding joint can be accurately obtained by analyzing its stress-strain curves measured by DIC method.关键词：2219 aluminum alloys;Welding joint;Digital image correlation method;Tensile properties
- 6
- |
- 494
- |
- 2
发布时间：2022-09-22 - 摘要：It is required to conduct repeated multi-frequency test to determine the best detection frequency when taking traditional tone burst as the guided wave excitation of dirt pipe, which had problems of blindness, time and resources consuming. A conversion algorithm from broadband chirp to tone burst was put forward based on broadband chirp guided wave excitation of dirt pipe. All tone burst responses in the broadband of chirp signal is similarly extracted during post-processing. The best detection frequency was determined through the comparing energy distribution and modal purity of the different frequency guided wave responses that it was calculated from the chirp response, and combined with time-frequency analysis method to determine the appropriate waveguide frequency interval according to the distribution of the response waveform energy of the dirt pipe. It had shown from simulation analysis and experiment studies that: the center frequency of about 175 kHz was the most appropriate for guided wave detection of investigating dirt pipe. The method could determine the best guided wave detection frequency of dirt addresses both test at multi-frequency and minimize acquisition time, which would lay a foundation for achieving guided wave detection from the ‘point’ to ‘line’ of the pipe dirt.关键词：Dirt detection;Ultrasonic guided wave;Chirp excitation;Time-frequency analysis
- 3
- |
- 134
- |
- 1
发布时间：2022-09-22 - 摘要：In order to verify the strength of polyvinyl chloride（pvc） plastic sheet lap joint with different surface roughness, the pvc plate was polished with different mesh sandpaper（polished length was 30 mm）. The surface roughness was measured with a surface roughness instrument and the surface was examined with a high power microscope. The results show that different types of sandpaper abrasive sheet will produce different surface roughness. 60 mesh to 400 mesh sandpaper polished sheet surface roughness decreased gradually, the performance of the Ra value from 10.840 μm reduced to 1.503 μm. Tensile strength test was carried out by bonding the sheet with different surface roughness to the silicone rubber, and the overlapped plate material with different surface roughness produced different overlapping strength. The maximum tensile force that can be sustained by the lap joint with 60 mesh to 100 mesh sandpaper increased from 1.858 kN to 2.063 kN, and the overlap strength increased gradually. The maximum tensile force that can be sustained by the lap joint with 100-400 mesh sandpaper was reduced from 1.563 kN to 1.567 kN, and the overlap strength is reduced gradually. The control group has no surface treatment of the plate lap joints, can withstand the maximum tensile force of 1.380 kN, is the lowest overlap strength. So for the pvc plastic sheet and silicone rubber lap joints, with 100 mesh sandpaper grinding,the lap performance is the best.关键词：Polyvinyl chloride;Surface roughness;Bonding;Lap strength
- 4
- |
- 125
- |
- 0
发布时间：2022-09-22 - 摘要：The intersection of neutral layer and the transverse section is called neutral axis. The position of neutral-axis will be changed when the corresponding beam structure is damaged. In this work, the static loading test of recycled concrete beam is carried out to verify the damage detection method based on neutral axis position. Experimental results show that structural damage can be detected by the change of the neutral-axis position.关键词：Neutral axis;Damage identification;Beam structure;Recycled concrete
- 4
- |
- 149
- |
- 2
发布时间：2022-09-22 - 摘要：The fatigue crack growth tests for 2024-T62 aluminum alloy were conducted under three stress levels, the dispersion of fatigue crack growth were analyzed by using experimental data based on mathematical statistics. The analysis results indicate that the experimental data of fatigue crack growth obey the log-norm distribution. The standard deviation and coefficient of variation（COV） both increase with the loading cycle raising. The stress levels have some effect on dispersion of fatigue crack growth sizes, when the loading cycle increases, the standard deviation of fatigue crack growth under high stress level is greater than the standard deviation of fatigue crack growth under low stress level, and the increasing speed of standard deviation and COV of fatigue crack growth under high stress level is faster than the increasing speed of standard deviation and COV of fatigue crack growth under low stress level. The stochastic fatigue crack growth model is verified by experimental data.关键词：2024-T62 aluminum alloy;Fatigue crack growth;Distribution rule;Statistical variables;Crack exceedance probability
- 3
- |
- 324
- |
- 2
发布时间：2022-09-22 - 摘要：Micro-milling can fabricate 3 D free-form surface and complex components and has a promising prospect. However, due to sharp decreases of the tool scale and machining parameters, micro-milling process shows remarkable differences from traditional milling, thus researchers conduct broad studies on micro-milling technology recent years. The process of micro-milling is complicated and involves many aspects, the domestic and overseas researches in micro-milling are summed up in this paper, the development of minimum chip thickness, cutting force, surface roughness, tool wear, and other aspects of researches are summarized. The development trend of micro-milling and the application prospect are discussed.关键词：Micro-milling;Minimum chip thickness;Cutting force;Surface roughness;Tool wear
- 4
- |
- 732
- |
- 6
发布时间：2022-09-22 - 摘要：For high-speed CAM with clearance in the process of running with reduced stability and increasing noise and wear and so on and on the basis of the characteristics of structure dynamics and kinematics, a kind of high speed CAM mechanism with clearance based on kinematics and dynamics multiple targets was put forward for optimization design. Optimization results show that we can find that the optimized CAM curves improve overall performance and part of the performance curves approach or exceed high-speed CAM common cycloid CAM curve when the three coefficients polynomial CAM curves and the standard CAM curve are compared. Among them, the weight seven variable coefficient polynomial CAM curve comprehensive performance is best and its noise is reduced accordingly. So it has higher engineering application value from these findings.关键词：Multi-objective optimization;Clearance;High speed cam mechanism;Polynomial variable coefficient
- 3
- |
- 374
- |
- 2
发布时间：2022-09-22 - 摘要：In order to realize the rapid reliability evaluation of long-life and high reliability products at a normal stress level, the reliability statistical model of Arrhenius—Weibull was established, by using the Weibull distributions products with the consistent failure mechanism and a log-linear acceleration life test model between characteristic life and stress level. The minimum variance of the product median lifetime estimate at normal stress level as optimum object was considered, the number and quantity of test stress level, samples allocation proporation and censoring time at each stress level are determined as design variables, put forward a reliability optimum scheme of time-censoring constant-stress ALT（CSALT） for weibull distributions. The Fisher Information Matrix is obtained for constructing asymptotic confidence intervals for the model parameters. As the example analysis shows that the reliability optimum scheme of CSALT is effective.关键词：Constant-stress accelerated life test;Accelerated life test model;Optimum design;Reliability
- 4
- |
- 171
- |
- 1
发布时间：2022-09-22 - 摘要：In order to solve the problem of reliability sensitivity analysis of tracked vehicle transmission gears in the presence of different failure modes, the random perturbation theory, the fourth moment method and Edgeworth series are employed to calculate the statistical correlation and reliability index of each performance function of the failure modes, and the reliability of the failure modes of the mechanical component with the arbitrary random distribution parameters. According to the future that only a few potential failure modes existed in the component and the overall fails when a failure mode occurs in parts, the failure of the component is regarded as the failure of a series system. On this basis, the calculating formulas of reliability sensitivity of the mean and variance of random variables are derived with the gradient method. The example illustrates that this method could effectively estimate the reliability sensitivity of mechanical components with multiple failure modes and provide reference for the optimization design of mechanical components.关键词：Multiple failure modes;Arbitrary distribution parameter;Sensitivity analysis;Transmission gear;Fourth moments;Reliability
- 4
- |
- 297
- |
- 2
发布时间：2022-09-22 - 摘要：Based on linear materials, two kinds of equivalent tire models were proposed, which are single solid element structure and solid element + beam element mixed structure, taking TBR tire 11.00 R20 18 RP as the research object. The impact of different elastic modulus of each layer on the static stiffness of two equivalent models was analyzed using ANSYS. And on this basis, the parameter optimization analysis of elastic modulus of materials was carried out. Based on the optimization results, the modal property of the two equivalent models were studied, and the effective range of the equivalent models was analyzed by comparison with the experimental results. The was shown that the tire equivalent model composed of solid element + beam element mixed structure based on linear material can better simulate the static stiffness, tangential mode and axial mode of tire, but the radial mode frequency is relatively low; in the study in which only the radial property is concerned, such as in a vehicle-road coupling simulation, the radial mode frequency can be improved by reducing the density of the bundle layer, so that the equivalent model is more effective.关键词：TBR tire;equivalent model;Finite element analysis;Static characteristics;Modal characteristics
- 3
- |
- 137
- |
- 1
发布时间：2022-09-22 - 摘要：In order to realize the protection of broken conveyer belt with different moving direction, the scheme of broken belt protector with bidirectional and arc shaped catching scheme was proposed, and the main parameters were designed taking the GX1000 type conveyer belt as application example. The virtual prototype simulation of the broken belt protector catching process was done, and the velocity characteristic of main components was obtained. The model prototype with 1/2 structure size of the prototype machine was manufactured, and the test of catching process and the catching force were carried out. And the catching force parameters of prototype machine were derived based on small-scale model similarity theory. Consequently, the virtual and model prototype of broken conveyer belt protector with bidirectional and arc shaped catching scheme can carry out catching motion by different directions acorrding to the direction of broken belt motion, and wedge-shaped space for catching is formed and catching brake is finished. The broken belt protector single machine can realizes bidirectional catching. The limit catching force of prototype machine is higher than 56.4 kN, and the limit catching force is higher than theoretical cutting force which is 23.15 kN, and the demand of catching brake safely is met.关键词：Conveyer belt;Broken belt protector;Bidirectional and arc shaped catching scheme;Virtual prototype;Model prototype
- 4
- |
- 84
- |
- 1
发布时间：2022-09-22 - 摘要：In order to improve the comprehensive performance of backhoe hydraulic excavator, a multi-objective optimization design of backhoe hydraulic excavator working device was carried out on the basis of considering the theoretical digging force, static strength and dynamic performance.The strength analysis and modal analysis of the working device are carried out in ANSYS Workbench. By using the optimal Latin hypercube experimental design and response surface methodology, the approximate model of boom strength, bucket strength, working equipment quality, 1 order modal and 2 order modal is established, and the optimization efficiency is improved. Using NSGA-II algorithm, the multi-objective optimization design of the working device is carried out, and the Pareto solution set is obtained. The optimization results show that the quality of the working device decreases, the dynamic performance is improved, the theoretical digging force is increased, and the overall performance of the working device is improved when the constraint is satisfied.关键词：Working device;Multi-objective optimization;Optimal Latin hypercube design;Response surface methodology
- 3
- |
- 425
- |
- 7
发布时间：2022-09-22 - 摘要：A precision adjusting mechanism of six-degree-of-freedom（SDOF）based on Stewart structure with high accuracy and high stiffness is designed in this paper. Firstly, the configuration of adjusting mechanism was designed and the kinematics analysis was conducted; Then, the error model was established and the precision of the configuration of parallel platform was analyzed. After that, the structure of adjusting mechanism was designed according to the theoretical analysis results, including the single displacement actuator and the offset hinge; Finally, the stiffness of the adjusting mechanism was analyzed. This article obtaining the analysis results that the repeatability of the SDOF adjusting mechanism were ±2 m in X and Y direction,±0.54 m in Z direction, ±6.13 rad in Rx, Ry, Rz direction, and the fundamental frequency of the transverse vibration was 104.3 Hz and the axial stiffness was 61.3 N/μm. The analysis results showed that the SDOF precision adjusting mechanism fulfilled the design requirements, and the rationality for structure design of adjustment mechanism was verified.关键词：Stewart platform;Adjusting mechanism;Monte Carlo simulation;Stiffness analysis
- 4
- |
- 327
- |
- 1
发布时间：2022-09-22 - 摘要：To study the interaction mechanism of shearer and the surrounding rock,using the MG500/1180-WD shearer model as research objects,EDEM discrete element simulation software is used to establish the three-dimensional simulation model,Considered the effect of the factor which is coal fragmentation and roof pressure on the performance of shearer cutting. Study on the dynamic process of shearer cutting.Using single-factor method to study the effect of coal seam dip angle on the factor of coal loading rate、cutting resistance and special energy consummation for cutting. Study on the wear of cuttings under different working conditions. The results show that when the dip angle is in the range of 0 ° ～ 10 ° in the range of-20 ° ～ 0 °, the effect on the working performance of the shearer is small, which can satisfy the coal loading efficiency of the shearer. Cutting stability. When the absolute value of the dip angle is large, the inclination angle is negative or the absolute value is large, it has a significant effect on the working performance of the shearer. It may be considered to change the working parameters of the shearer, such as reducing the drum speed, Speed, adjust the cutting depth to improve the performance of coal miners, in order to achieve efficient cutting shearer provides an improved reference.关键词：EDEM;Drum work performance;Coal seam dip angle;Coal loading rate;Cutting resistance;Special energy consummation for cutting
- 3
- |
- 336
- |
- 3
发布时间：2022-09-22 - 摘要：The crowd reducer gears of large mining electric excavator are low speed,heavy-duty and hard surface gears.In the mining process, the phenomenon of gear unbalanced load is inevitable.Through the modification of gears,it is possible to improve its carrying capacity and contact state. Using the thin slice gear model,statistical average load of excavator mining process is taken as the reference load of modification,the minimum contact stress of gears at the excavator mining position withmaximum statisticalcrowd force is regarded as the objective,the slope modification of the two stage pinion（driving wheel） of the crowd reducer is carried out.Further, no edge load at tooth surface in each mining location is regarded as the objective,the crown modification of the two stage pinion of the crowd reducer is carried out.In the process of excavator mining,compare with pinion without modification,the maximum stress（including contact stress of tooth surface and bending stress of tooth root）of thepinionwith modification decreases significantly,and the edge contact condition of tooth surface is obviously improved.After modification,when the gear is subjected to the statistical maximum load of excavator mining process,the stress value of the gearis still less than the allowable stress.Simulation results show that,axial modification of crowd reducer gears of large mining electric excavator has positive significance for improving carrying ability and contact condition of gears.关键词：Mining electric excavator;Crowd reducer;Gear;Axial modification
- 4
- |
- 122
- |
- 1
发布时间：2022-09-22 - 摘要：The foamed aluminum filled crash-box with induction grooves on the side wall was made finite element analysis in the impact process by LS-DYNA,and the parameters influence of induction grooves on the energy absorption characteristics of crash-box was studied. The results was dealt with the LS-Prepost, considering the energy absorption, peak impact force, the average impact force and energy absorption ratio, when crash-box was made two radius of 2.5 mm semicircle grooves in the upper 50% part of the side wall, in the impact process of a symmetrical stack the ideal type of shrinkage deformation, depressed peak impact force without affecting energy absorption, higher energy absorption ratio and compression efficiency wound be gotten. The finite element simulation of the impact process was feasible when the crash-box body was made the impact test by the vertical and horizontal hydraulic impact test platform.关键词：Foam aluminum;Crash-box;Energy absorption;Impact force peak;Energy absorption ratio;Compression efficiency
- 4
- |
- 332
- |
- 4
发布时间：2022-09-22 - 摘要：T4 link is the critical load-bearing component for nozzle element of a certain engine. Whether the nozzle load meets the requirements or not at high temperature is the key factor in the structural integrity of the nozzle unit. It’s analyzed that strain response of the T4 link was resulted from mechanical load, thermal gradient and material parameter using the thermo-solid coupling method. The T4 link load at high temperature was measured with the high temperature strain gauge on bed test. The process for bonding and assembling the high temperature strain gauge was developed. the equation extension method of the load calibration was deduced, the measurement method containing load calibration, thermal correction, and date processing for the high temperature load were established. The aero-engine bed test shows that the variation tendency and value of the thermal-output strains vary much between T4 links. The maximum error for T4 link is 0.27 kN, the maximum measured tension is 62.1% of the designed load value, the maximum pressure is 58.46% of the designed load value, and the structural strength design of T4 link meets the operating requirements.关键词：Aero-engine;Load-bearing component for nozzle element;Load at high temperature;High temperature strain gauge;Thermo-solid coupling analysis
- 4
- |
- 125
- |
- 2
发布时间：2022-09-22 - 摘要：In view of the structural failure caused by laser welding residual stress, with the target DCT dual clutch transmission inner plate carrier and the spline as the study object,a three-dimensional finite element numerical model was established by SYSWELD finite element software and the numerical simulation of the welding process was carried out. The thermal cycle curves of the transient temperature field and characteristic points were obtained, the characteristics of the weld seams were basically in line with the actual welding seams. On this basis, the evolution of the metallurgical structure and the distribution of the residual stress in the weld were obtained.The results show that the microstructure of the weld area after cooling is mainly martensite, and the welded joint has good strength and toughness. The tangential residual stress reaches the peak value of tensile stress at about 2 mm from the center of the weld. This is where the weld is most vulnerable to the crack.关键词：DCT duael clutch transmission;Clutch inner plate carrier;Simulation of laser welding process;Temperature field;Tangential residual stress
- 3
- |
- 130
- |
- 1
发布时间：2022-09-22 - 摘要：The fatigue crack of the wheel rims often explodes in the inclusions gathering area, and the accumulation of large inclusions will affect their fatigue life. In this article, through dynamic simulation and finite element simulation combined with material fatigue test to determine the probability of containing inclusions wheel rim method of fatigue life at different speeds. In order to estimate the fatigue life of the train wheel rim with inclusions at different speeds, the vehicle dynamics model and the wheel axle with inclusions finite element model of EMUs CRH5 were established. Then obtain the random load time history of the wheel and the stress time history of the dangerous parts at different speeds. Based on the different confidence degrees、survival rates of the S-N curve and the Miner criterion to establish fatigue life of the wheel rim containing inclusions. The results show that under the same confidence degree and survival rate, as speed increases, the fatigue life of wheel rim containing inclusions will obviously shorter; under the same speed and confidence degree, as survival rate increases, the fatigue life of wheel rim containing inclusions will obviously shorter; under the same speed and survival rate, as confidence degree increases, the fatigue life of wheel rim containing inclusions will obviously shorter.关键词：Train;Wheel rim;Inclusion;Speed;Fatigue life
- 3
- |
- 168
- |
- 1
发布时间：2022-09-22 - 摘要：The purpose of this paper is to research problems of cracks at a circular hole, which is a common crack configuration in aircraft structures. The Muskhelishvili complex function method and the Cauchy integral method are combined to develop crack surface displacement equation for two cracks with arbitrary length emanating from a circular hole in an infinite plate under pressure on part of crack surface, and calculate the crack-surface opening displacements for two cracks with arbitrary length emanating from a circular hole. When two cracks are symmetric, the calculated results were compared with the weight function method, the maximal relative error is 16.21%. The results show that the complex variable function method and the Cauchy integral method used to calculate crack surface opening displacements can be applied for two-symmetric（or asymmetric） cracks emanating from a circular hole in an infinite plate. The present study provides a research foundation for fatigue crack closure and crack opening stress analysis for double cracks with arbitrary length emanating from a circular hole.关键词：Hole edge cracks;Crack surface opening displacement;Complex variable function method;Conformal maps;Partially loaded crack
- 4
- |
- 135
- |
- 3
发布时间：2022-09-22 -
RESEARCH ON FATIGUE CRACK PROPAGATION CHARACTERISTICS AND REMAINING LIFE AT THE TOOTH ROOT OF A GEAR
摘要：Based on the FEM, the fatigue crack propagation of a involute cylindrical gear is numerically simulated. Firstly, through analyzing the meshing gear of a pair of healthy teeth, the maximum bending stress of the tooth root is determined, And it is taken as the starting point of the crack. The cracks are divided into crack and non crack blocks. The initial crack is preformed in the crack block and the block is remeshed with isoparametric singular element. The crack block and the non cracked block is connected by a multi-point constraint. The stress intensity factor and crack propagation angle are measured in crack propagation process, Based on Paris formula,tooth crack propagation trajectory and remaining life of gear is numerically simulated. The influence of load as well as initial crack length on residual life was analyzed.关键词：Gears;Fatigue crack;SIF;Crack growth angle;Fatigue life- 8
- |
- 732
- |
- 4
发布时间：2022-09-22 - 摘要：Due to the fluctuations for high-pressure gas, the displacement of reciprocating air compressor needs to follow the change in requirements. At present, the regulating methods can be applied, including the refluxing regulation, the variable speed adjustment and the pressing-off inlet valve regulation. Among them the pressing-off inlet valve regulation has the best effect, but its control technique and structural modification are relatively difficult. In this paper, according to the demand of the air capacity regulation for reciprocating compressor, an improved operating cycle model of air compressor under the capacity regulation was established. The behaviors of the netted valves and the changes of the pressure in cylinder were analyzed. Additionally, different control parameters in the air capacity regulation system were numerically simulated, the different regulating effects are obtained. The influence of the above parameters was analyzed, which lays the foundation for the system optimization design.关键词：Reciprocating compressor;Air capacity regulation;Netted valve;Numerical simulation
- 3
- |
- 131
- |
- 0
发布时间：2022-09-22 - 摘要：Due to the risk of the billet hitting the marking equipment, it is necessary to design a set of anti-collision mechanism. When the billet hits the marking equipment, the marking gun goes back and the positioning pins are pulled out by a scotch-yoke mechanism. Then the support arms lift to avoid the billet. Before the impact, the anti-collision mechanism performs as a gun frame, carrying the gun moving. However, the vibration may have an adverse impact on the marking effect. The maximum force appears when the marking gun is moving in the accelerative stage in X and Y orientations. The load and boundary conditions were set according to the actual load condition of the anti-collision mechanism. The harmonic response analysis calculated the amplitude of X and Y orientations of the marking gun at different frequencies. Then the structure of the anti-collision mechanism was improved and the harmonic response analysis was done again. The results show that the amplitude of the improved structure has been reduced dramatically and the marking effect has been improved.关键词：Anti-collision mechanism;Scotch-yoke mechanism;Vibration;Harmonic response analysis
- 3
- |
- 142
- |
- 1
发布时间：2022-09-22 - 摘要：The simulation model of 2 mm thick 2 A12 aluminum alloy thin plate impacted by blade projectile was established by using the ABAQUS finite element software, including impact of yaw and oblique, and the yaw angle is 0-90° and the incidence angle is 0-60°. The effect of impact angle on the impact process, the ballistic limit of the target and the energy absorption of the target were investigated. The simulation results show that the target is mainly shear failure when the yaw angle is 0°, and a long plug and rectangular reaming are remained. When the yaw angle is 15°-60°, the failure mode of the target is ductile expansion and the hole area increases with the increase of the yaw angle. For the yaw angle ranges from 75° to 90°, the target is tore by tensile and the damage is serious. The failure mechanisms of target is both plug and petal damage when oblique impact. The ballistic limit of the target increases with the increase of the yaw angle, and the energy absorption of the target is related with the yaw angle and impact velocity of the projectile. The energy consumption of the target is not independent of the incidence angle.关键词：Aluminum alloy thin plate;Blade projectile;Yaw angle;Numerical simulation
- 4
- |
- 215
- |
- 3
发布时间：2022-09-22 - 摘要：The connecting rod breaked in the logo position at the middle of the connecting rod body, when it was subjected to cyclin load fatigue experiment. The material and manufacturing process of the experimental samples were checked and there was no defect. The three-dimension solid model of the experimental connecting rod was built by 3-D modeling software, and the stress concentration had occurred at the same location logo with the experimental sample connecting rod by using finite element method. Then three schemes were designed and the influence on the distance between the logo words, the height of logo to connecting rod body surface and the positing of the logo to stress were analysis, the results showed that: the stress was reduced by appropriately increasing the spacing between logo words. The depressing logo could greatly reduce the stress comparing with the protruding logo. The positon of the logo had the most influence to the stress, and the stress concentration of the connecting rod disappeared when the logo moved from middle of the connecting rod to the outside of the connecting rod cap.关键词：Engine;Connecting rod logo;Fatigue strength;Scheme optimization
- 3
- |
- 95
- |
- 0
发布时间：2022-09-22 - 摘要：Reciprocating compressor stepless capacity control system in the petrochemical industry are widely used, unloading device as a key component of the system actuator, the action characteristics of the relationship between the quality of the system directly related to the efficiency of the air intake system and compressor valve life. In this paper, ANSYS/Ls-dyna explicit dynamics software is used to simulate the automatic opening process of the intake valve at the rated speed of the compressor. The displacement of the valve is measured by the eddy current displacement sensor. On the basis of this, the operation of the unloader under different oil supply pressure and different ejection time is simulated, the ideal hydraulic ejection force and the ejection phase are determined. It is concluded that the reasonable action of the unloader can effectively relieve the vibration of the valve plate and improve the force of the valve.关键词：Reciprocating compressor;Capacity regulation;Unloader;Valve plate
- 4
- |
- 119
- |
- 1
发布时间：2022-09-22 - 摘要：According to the working process and fault characteristics of belt conveyor, a safe and reliable intelligent control system solution is proposed. The solution consists of centralized control system and field control system. It adopts the control mode of PLC and host computer. PLC is used to collect and control the data of the equipment in the whole belt conveyor. The intelligent control of belt conveyor is realized by issuing control commands to the system equipment through the interface of the upper computer and displaying the operation status and fault alarm information of each equipment intuitively and dynamically. The main technical points of the system are introduced from the aspects of overall solution, hardware selection, software design and control flow.关键词：Belt conveyor;Intelligent control;Fault warning;Automatic speed regulation
- 5
- |
- 239
- |
- 1
发布时间：2022-09-22 - 摘要：The nonlinear effects of geometry, material and contact are considered, the finite element analysis（hereinafter FEA） method of composite stringer out-of-plane tension failure is established precisely by using Hoffman material failure criteria and Newton-Raphson increment iteration method. A verification test is designed to test the failure load and failure mode of three different stringer configurations.Then the load-displacement curve is drawn to verify the validity of the FEA method.The influence factors of out-of-plane tension failure of composite stringer are studied, which can guide the strength design of aircraft.关键词：Nonlinear;Composite meterial;Stringer;Out-of-plane tension
- 3
- |
- 241
- |
- 1
发布时间：2022-09-22 - 摘要：The suspension structure is the key bearing structure of airborne missiles. In this paper, two methods are used to analyze the strength of the suspension structure. First, the inertia release method is used. This method can accurately simulate the boundary conditions of the hang up flight but the ground static test can’t be carried out accordingly. So the boundary constraint method is put forward according to the structural characteristics of airborne missile. By comparing the numerical results of these two methods, it is found out that the boundary conditions that can meet the analytical accuracy requirements and are suitable for carrying out ground static test. Finally, ground static test was carried out accordingly. Which further validates the adaptability of the suspension structure to the flying load.关键词：Suspension structure;Inertia release;Boundary constraint;Static test
- 4
- |
- 133
- |
- 1
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