最新刊期
卷 47 ， 期 1 ， 2025
- 摘要：The misalignment of the dual-rotor system for the aero-engine will lead to abnormal increase of the vibration which results in the rotor-stator rubbing and affects the safty and stability of the rotor operation.The dual-rotor system was taken as the research object.Considering the combination misalignment-rubbing fault, the dynamic model of the rotor system is established based on the lumped mass method.The differential equation of the system motion was established according to the Lagrange equation, and the Range-Kutta method was used to solve it.The influence mechanism of the key parameters such as the speed, the misalignment angle and the coupling misalignment on the nonlinear dynamic characteristics of the system was studied.The results show that the system presents complex dynamic characteristics such as periodic, multi-periodic, quasi-periodic and chaotic motion with the increase of the rotor’s speed.When the speed is in the range of 1 500-2 200 rad/s, the system switches between periodic 2 motion and chaotic state through multiple paroxysmal bifurcations and paroxysmal inverted bifurcations.There are nonlinear phenomena such as jump in the bifurcation diagram of the vibration response with the change of the parallel misalignment of the coupling.As the misalignment angle of the bearing increases, the chaotic interval of the high speed decreases, and the stable periodic motion interval increases.关键词：Bearing misalignment;Coupling misalignment;Rubbing;Coupling fault;Nonlinear0|0|0发布时间：2025-01-23
- 摘要：In response to the challenging task of fault feature classification in the current working conditions of pumping units，which results in poor adaptability and low recognition rate of the established diagnosis model. The dynamometer card was pretreated by mathematical morphology through the analysis of the motion state of the pumping unit valve and the sucker rod. Then, two methods of obtaining valve opening and closing points and load variation characteristics were proposed, and 54 new features of global faults of pumping units were extracted, and the characteristic database of working conditions of the pumping unit was established.Finally, the algorithm of decision tree, logistic regression and support vector machine was used to verify that the feature database has good classification effect under different working conditions. The characteristic indexes of different fault conditions were evaluated, and the private rule database of each working condition was obtained. The research results demonstrate that the proposed features in this study are capable of effectively identifying comprehensive faults in pumping units, exhibiting a high level of recognition accuracy.关键词：Oil pumping machine;Dynamometer card;Feature extraction;Fault identification;Valve0|0|0发布时间：2025-01-23
- 摘要：The torsional vibration of reciprocating compressor crankshaft system can cause major problems such as burnt bearings and shaft fracture.In order to understand the torsional vibration response of the compressor rotor system, a torsional vibration mechanics solution method for the flexible rotor system of the compressor considering the bushing-pin collision clearance and the oil film clearance of the crankshaft-bearing was proposed, which provided a new idea and method to avoid the natural frequency of the crankshaft system.Based on the multi-body dynamics and Hertz contact theory，the torsional dynamic response of the crankshaft system with collision clearance was solved.The results show that the torsional vibration amplitude of the 4th column crank pin is the largest, the torsional angular displacement amplitude is 0.051°, and the dynamic angular velocity peak value is 156.026 rad/s.Based on this, the crankshaft-bearing oil film clearance was considered, the oil film pressure of sliding bearings was calculated by the finite difference method and the over-relaxation iterative method, and the dynamic characteristic coefficients of bearings were solved according to pressure perturbation method.The effects of the bushing-pin collision clearance and the crankshaft-bearing oil film clearance on the dynamic response of the crankshaft system were comprehensively considered in the modal analysis of the crankshaft system under preload.The resonance of the crankshaft with and without oil film clearances was compared. The results show that the natural frequencies of the 3rd and 8th orders of the crankshaft system decreases by 44.64% and 21.23%, and when considering the reduction of the resonant speed point of the crankshaft with comprehensive clearance in the same speed range, the 2nd order critical speed is reduced by 38.55%, and the probability of resonance increases.关键词：Reciprocating compressor;Collision clearance;Oil film clearance;Rigid-flexible coupling;Crankshaft torsional vibration;Resonance0|0|0发布时间：2025-01-23
- 摘要：A two-degree-of-freedom collision system with gap and elastic constraint was used as the research object, and the regional distribution and transitions of the periodic motion of the system under low frequency conditions were studied by numerical simulation.It was obtained that with the decrease of excitation frequency, the p/1 periodic motion occurs with grazing bifurcation transitions to （p+1）/1 periodic motion.When the number of collisions was large enough, the Chattering-impact characteristics were presented.Then a circuit model that was completely equivalent to the collision system was established and simulation experiments were carried out.The results show that the results generated by establishing the equivalent circuit are consistent with those generated by numerical simulations, and the equivalent circuit is more efficient in simulation experiments, which can realize fast modal transitions and parameter adjustments，making it more convenient and providing a research method for the study of nonlinear dynamics.关键词：Vibration system;Modal conversion;Numerical simulation;Chattering-impact motion;Equivalent circuit0|0|0发布时间：2025-01-23
- 摘要：In order to avoid large vibration response and transcritical motion instability of ultra-high speed centrifugal impeller rotor system caused by unbalanced excitation, the unbalanced excitation response of ultra-high speed centrifugal impeller rotor system was analyzed by using Ansys rotor dynamics response analysis module and comprehensively considering the stiffness and damping of sliding bearing, the dynamic response of ultra-high speed centrifugal impeller rotor system under different unbalanced excitation was obtained.At the same time, DEWESoft vibration test system was used to track and record the rotating frequency vibration value of ultra-high speed centrifugal impeller rotor system, and compared with the unbalanced response analysis results, it was concluded that the dynamic balance accuracy level of the ultra-high speed centrifugal impeller rotor system should be better than G1 level. The unbalanced excitation response analysis and control method has been well verified by tests, which has important engineering application significance.关键词：High speed centrifugal compressor;Ultra-high speed rotor system;Unbalanced excitation;Dynamic response;Transcritical0|0|0发布时间：2025-01-23
·Vibration·Noise·Monitoring·Diagnosis·
- 摘要：In order to determine the sensitive vibration characteristic parameters of coal and gangue in the process of top coal caving and improve the intelligent identification accuracy of coal and gangue, the dynamic characteristics of the tail beam of the hydraulic support were studied. Firstly, the rigid-flexible coupling dynamic model of top coal caving hydraulic support and coal gangue was established, and the vibration acceleration of the tail beam of the hydraulic support in the process of coal caving was calculated. Secondly, the acceleration response was decomposed by variational mode decomposition (VMD) to obtain the intrinsic mode function (IMF), and the time domain and frequency domain characteristics of each IMF component were analyzed. Thirdly, the t-distributed stochastic neighborhood embedding (t-SNE) method was used to reduce the dimension of these features, and the average silhouette coefficient (ASC) of different features was calculated. The vibration characteristics of the tail beam under the impact of coal gangue were compared and studied. Finally, the bench of the top coal caving hydraulic support was built to verify the calculation results of the model. The results show that the energy, singular value, mean frequency, peak frequency, spectral centroid and frequency variance in the IMF component of the vibration acceleration of the tail beam are sensitive to the characteristics of coal and gangue, which can be used as the characteristic parameters of the coal and gangue identification.关键词：Top coal caving;Coal gangue identification;Finite element method;Discrete element method;Variational mode decomposition0|0|0发布时间：2025-01-23
- 摘要：Considering the actual excitation load, the nonlinear dynamics characteristics of the bolted structure have a certain impact on the whole mechanical system. The dynamics model of actual bolted structure is more complex with considering joint surface morphology parameters and plasticity index. Therefore, with considering the influence of the surface mopography parameters, plastic index on the normal contact stiffness, contact damping and under the various conditions such as external harmonic excitation, the existing normal contact model of bolted structure was modified, and the obtained nonlinear normal contact stiffness and nonlinear contact damping were applied to the dynamics response characteristics analysis of forced vibration of bolted joints structure. The influences of surface morphology parameters and plasticity index on the dynamics characteristics of bolted structure were studied.关键词：Bolted structure;Rough joint surface;Surface morphology parameter;Plasticity index;Nonlinear characteristic0|0|0发布时间：2025-01-23
- 摘要：Aiming at the research on intelligent identification of caving coal and gangue, in order to provide a complete and effective vibration signal acquisition scheme of coal and gangue, an optimal layout strategy of tail beam sensors of caving coal hydraulic supports based on vibration characteristics of coal and gangue was proposed. Firstly, the modal analysis of the tail beam model was carried out, extracting the vibration mode matrix， and the effective independent method was used to select the measuring points. Secondly, the vibration signals of coal falling and gangue falling at the corresponding primary measuring points from the tail beam test bench were obtained, and the feature extraction was carried out. Thirdly, the extracted features were visualized by t-distributed stochastic neighbor embedding （t-SNE） dimensionality reduction, and five features which were sensitive to the distinction between coal and gangue signals were selected as target features. Finally, the probability density functions of target features were estimated by the kernel density estimation method. The K-L（Kullback-Leibler） divergence was used to evaluate the approximation between combined signal of each measuring point and the complete signal and the difference between characteristics of coal and gangue. The evaluation indexes of coal and gangue vibration signals were constructed. Combined with Fisher information matrix criterion, a comprehensive evaluation index was formed to determine the optimal scheme of tail beam sensor arrangement. The results show that the sensor arrangement scheme determined by this method not only reduces the number of sensors on the basis of satisfying modal observability, but also makes the measured vibration signals have better coal gangue difference and information integrity.关键词：Top coal caving;Vibration signal;Optimal sensor placement;Hydraulic support tail beam;Effective independence method;K-L divergence0|0|0发布时间：2025-01-23
- 摘要：The planetary gear system is widely used in aircraft transmission equipment because of its small size, light weight and large load capacity，but the problem of bias load caused by various errors cannot be avoided, and a serious bias load condition will lead to under utilization of the advantages of the planetary system cannot be fully exploited.The influence mechanism of the flexible change of the inner gear ring on the bias load behavior of the system was investigated by taking a certain type of aeronautical planetary gear system as the research object.The deflection，stress and strain of the inner gear ring were measured by experiments with different number of planets and different rim thicknesses, and the mechanism of bias load was analyzed and the degree of influence of the number of planets and rim thickness on the bias load behavior of the system was evaluated.The advanced simulation calculation and analysis of a large aeronautical planetary system was completed by using a hierarchical finite element model to quantify the influence mechanism of the variation of inner gear ring flexibility on the load distribution and gear ring deflection of the system.The accuracy of the simulation results was evaluated by fitting the experimental and simulation results to the same parameter range for comparison.The research results provide targeted structural optimization guidance for the development and design of internal gear rings of large aeronautical planetary gear systems, which can greatly reduce the cost of this type of large aeronautical equipment in the design and iteration process.关键词：Aerospace planetary gear system;Inner ring flexibility test;Bias load analysis;Simulation calculation0|0|0发布时间：2025-01-23
- 摘要：Based on the low temperature tensile test data of the rubber, Ansys software was used to fit the Mooney-Rivlin hyperelastic constitutive model of rubber material parameters, and the thermo-solid coupling simulation was carried out on the U-shaped rubber outer windshield according to three real working conditions, and the influence of different working conditions on the U-shaped rubber deformation was studied.The low temperature test was carried out on U-shaped rubber outer windshield and three rubber samples with different batten thicknesses， the influence of temperature and batten thickness on its deformation was studied.The results show that the U-shaped rubber deformation is mainly caused by the temperature change, the U-shaped rubber height decreases obviously, and the shape variable of the side wall thickness and the rubber length is small.In addition, the batten thickness has a greater influence on the rubber shape variable at the bolt hole.Compared with the batten of 5 mm and 6 mm thickness, the 4 mm batten produces a larger deformation under the bolt preload action, resulting in a larger deformation at the bolt hole, and then increasing the batten thickness can effectively reduce the hole removal risk.Comparing the finite element simulation data with the low temperature test results, it is found that the two results are basically consistent，which indicates the finite element analysis feasibility and the low temperature test reliability.The research results provide some guidance basis for the U-shaped rubber outer windshield under low temperature application reliability.关键词：U-shaped rubber outer windshield;Mooney-Rivlin hyperelastic constitutive model;Thermo-solid coupling;Finite element analysis;Low temperature test0|0|0发布时间：2025-01-23
- 摘要：Lattice structures have become a research highlight in the fields of aviation, aerospace and automobile because of its high specific strength and stiffness. The development of additive manufacturing technology makes it possible to manufacture mechanical metamaterials with complex geometric shapes and special mechanical properties. However, traditional additive manufacturing processes are difficult to coordinate the contradiction between the cost, geometric size and accuracy of such structures.In view of this, a mechanical metamaterial structure concept of reversible assembly and the connection method of its basic voxels were proposed, which can effectively overcome the size limitation of manufacturing equipment, and can construct a macro lattice structure with rich mechanical properties through different combination sequences. Aiming at the basic voxel type of reversible assembly, the influence of voxel geometric parameters, relative density and voxel numbers on its mechanical properties through parametric modeling method was analyzed, and the experimental results were compared. The results show that the three basic voxels have great rigidity difference, and Poisson’s ratio covers the range from negative to positive.Therefore, different combination sequences of these three basic voxels can produce macro structures with different mechanical property distributions, which proves the rationality of using these three basic voxels as the basic voxels of the reversible-assembly structure.In addition, the mathematical relationship between geometric parameters and mechanical properties can provide guidance for the engineering application of such mechanical metamaterials.关键词：Reversible assembly;Mechanical metamaterials;Parametric modeling;Lattice structure;Performance characterization0|0|0发布时间：2025-01-23
- 摘要：An online measurement method of a dynamic unbalance force of the geotechnical centrifuge was carried out based on monitoring the change of the axial preload of anchor bolts. Firstly, the change model of the axial preload of the anchor bolt under different unbalanced force states was deduced theoretically, which proved the feasibility of indirectly measuring the unbalanced force of the centrifuge. Then, the typical testing case was carried out on the TLJ-500 centrifuge, and the law of the dynamic unbalance moment changing with the counterweight was obtained. By fitting the change of the axial force at the measuring point, the relation between the axial force at the measuring point and the unbalance mass and the running gravitational acceleration g value of the centrifuge was established.Finally, the relation between the change of the axial preload of anchor bolts, acceleration of the centrifuge and counterweight mass were obtained by measuring the preload change of one anchor bolt and fitting the response surface. The results show that it is feasible to obtain the unbalanced force of the centrifuge operation by monitoring the change of anchor bolts’ pre-tightening force， and the centroids of different counterweights should be kept consistent in the test. When calculating the counterweight mass to balance the rotating arm according to the fitting formula, a larger acceleration should be used as far as possible to reduce the error caused by the centrifuge not being leveled.关键词：Anchor bolt;Axial pretension force;Geotechnical centrifuge;Unbalancing force;Fitted model0|0|0发布时间：2025-01-23
·Experimental Research·Testing Technology·
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Study on constraint of mixed mode crack and failure assessment diagram of pressure-bearing structure
摘要：The crack tip constraint and failure assessment diagram （FAD） in both plate specimen and pipe structure were studied to find out the compatibility and correlation of between the sample and piple.Based on the finite element method, constraints at crack tip of central cracked plate （CCP） specimen and cracked pressure pipe were obtained.It was found that crack tip constraint of CCP specimen under uniaxial loading is better matched with thick-walled pipeline under axial tensile loading, while CCP specimen under biaxial loading is better matched with thin-walled pipeline under internal pressure.In addition, the failure assessment diagram of CCP specimen and pipeline were obtained.It was found that FAD of CCP specimen is less related with thickness, when the thickness of pipe is within the range of thick wall or thin wall; was also pointed out that stress parallel to the crack direction increases the failure assessment curve （FAC） of the structure. Finally, it is found that FAC of the central crack plate specimen is higher than that of the pressure bearing pipeline, for the two structures with the same constraint level，and crack tip mixed mode degree and loading mode. That is, it is unsafe to use FAD of CCP specimen to evaluate pipeline.关键词：Mixed mode crack;Constraint;Failure assessment diagram;Pressure structure29|13|0发布时间：2025-01-23 - 摘要：In order to clarify the influence of different working conditions on the wear of tapered roller bearings, the wear state of tapered roller bearings was carried out.A quasi-statics model of tapered roller bearings including roller balance equation and inner ring balance equation was established, and a wear depth calculation model suitable for wear analysis of tapered roller bearings was derived based on Archard wear theory.The wear distribution characteristics of bearing inner and outer raceways and roller elements under light load, medium load and heavy load conditions were comparative analyzed.The results show that the wear depths of the tapered roller and the inner/outer raceways on the contact line show bimodal distribution characteristics, and the wear distribution of the outer raceway is closely related to the positions of the rolling elements.For light load condition, the peak wear depth of bearing raceways and roller elements increases by 20% as bearing speed increases 25%, and for heavy load condition, the peak wear depth of bearing raceways and roller elements increases more than 17% as bearing load increases 16%.The comparison of bearing wear peaks under the three working conditions shows that the product of the equivalent load and the speed of the bearing is not the determining factor controlling bearing wear，and the load change has a significant impact on the bearing wear.关键词：Tapered roller bearing;Wear depth;Contact pressure;Sliding speed;Working condition1|0|0发布时间：2025-01-23
- 摘要：In order to solve fatigue fracture problem of the transverse stabilizer bar link of a pickup truck, taking the measured load spectrum as support, the fatigue analysis and structural improvement of bar link was carried out based on multi-body dynamics load decomposition method. The load spectrum acquisition test of stabilizer bar link was carried out, and the correlation analysis between sensor signals was conducted, and the validity of the collected signals was verified. Through the kinematics compliance（KC） test, the accuracy of suspension dynamics model was verified, by using virtual iteration method, the accuracy of the vehicle dynamic model is verified by the measured load spectrum signal as excitation. The critical load of bar link was obtained by means of multi-body dynamics load decomposition method, compression rod instability theory method and bench test method respectively, the strength of link was checked and compared with the measured load value, and the accuracy of the three methods was evaluated. The results show that multi-body dynamics load decomposition method can accurately predict the critical load, the bench test method have some errors, and the the compression rod instability theory cannot be directly used for strength check of link. Fatigue simulation and optimization of link were carried out by combining nominal stress method and load spectrum of multi-body dynamics decomposition. The fatigue mileage predicted by simulation is 12 143 km, the relative error value with real life is 14%, which proves validity of simulation method. The structural improvement of the dangerous part of link body port eliminates stress concentration of it, and makes the design life of link meet the service requirements.关键词：Load spectrum;Multi-body dynamics;Virtual iteration;Fatigue damage0|0|0发布时间：2025-01-23
- 摘要：In order to investigate the relation between abrasion and crack initiation in the welded zone of rails and axle weight and friction coefficient, through the field measurement of a large number of uneven weld zones, two kinds of typical weld zone uneven data were fitted, and two kinds of typical uneven wheel-rail contact finite element models of upper convex and lower concave weld zones were established. Combined with the friction work model and Archard wear theory, the maximum wear cross section of the welded zone was predicted, and the crack initiation life of the welded zone was predicted based on the Jiang-Sehitoglu model. It is found that with the increase of axle load, the abrasion rate of both the upper convex and lower concave weld zone increases, and the abrasion rate of the upper convex weld zone increases significantly when the axle load reaches 16 t, while the abrasion rate of the lower concave weld zone increases significantly when the axle load reaches 18 t. When the friction coefficient increases from 0.2 to 0.35, the maximal abrasion amount of the two types of weld zones of the upper convex and the lower concave is 1.93 mm and 1.08 mm, respectively. The abrasion rate of the upper convex type increases significantly at a friction coefficient of 0.3, while the abrasion rate of the lower concave type increases significantly at a coefficient of 0.35. When the axle load increases from 12 t to 18 t, the service life of the upper convex weld zone decreases less, while the service life of the lower concave weld zone decreases more. In addition, when the friction coefficient is increased from 0.2 to 0.35, its effect on the service life of the upper convex weld zone is significantly smaller than that of the axle load （12-18 t）. However, when the friction coefficient is increased from 0.2 to 0.35, the effect on the service life of the lower concave weld zone is comparable to that of the axle load （12-18 t）. The results show that with the increase of axle load and friction coefficient, the influence of concave irregularity on the life of rail welding zone is more significant. In the process of engineering maintenance, we should pay attention to the appearance of concave welding zone and mark and repair it in time.关键词：Railway engineering;Wheel-rail relation;Wear prediction;Crack initiation prediction1714|5|0发布时间：2025-01-23
·Fatigue·Damage·Fracture·Failure Analysis·
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