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.

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.

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.

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.

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.

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 Chatteringimpact 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.

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.

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.

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.

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.