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According to the structural parameters of an actual turbofan aeroengine, the dynamics modeling and vibration analysis of multi-stage blade-disk-shaft integrated structure with three-dimensional crack are conducted. Based on the theory of fracture mechanics, the stress intensity factor is considered as a fracture criterion. This paper proposes a three-dimensional (3-d) equivalent notch model which is simpler and more convenient than the traditional crack simulation model. Moreover, its validity is analyzed. Aiming at the harsh working environment of the blades, the penetration crack is considered at the edge and the middle of a blade root, respectively. The influence of the crack on the strength failure of the rotor system is studied. Results show that the appropriate small angle equivalent notch model can be convenient and effective to simulate the fracture cracks, in which 5° is proved to be the best angle. The crack aggravates the vibration of blades obviously. A parametric study is conducted, with a particular focus on the effects of pressure load and centrifugal load on the stress intensity factors and displacement fields.

In turbo-machinery, wide-chord blades are widely used due to the advantages of improving fan efficiency and aerodynamic performance. The rotor with multiple wide-chord blades is spaced from the outer casing. The small clearance may cause rub-impact fault between wide-chord blades and the casing, which induces different damage severity or the destruction of the whole machine. Numerical simulation is necessary to analyze this kind of rub-impact fault, but the solution process becomes complicated because of the coupling of geometric nonlinearity, local vibrations of wide-chord blades and gyroscopic motion of the rotor. This paper develops a rubbing rotor model with multiple wide-chord blades considering the gyroscopic effect and geometric nonlinearity induced by rub-impact. Based on the rub-impact model established for wide-chord blades, the high-order nonlinear governing equations of the bladed rotor are derived. Vibration responses are solved, and a series of dynamic characteristic analysis is carried out. The results reveal that high-order nonlinearity has a little effort on vibrations during slight rub-impact. But with the increase of transverse deformation induced by severe tip-rub, its influence cannot be ignored. Besides, localized rub-impact phenomenon of blades induced by external synchronous forces is found. Instead, external asynchronous force makes all blades rub, one after another along the circumferential direction of the disk, and there is a phase difference Δ φ = 2 π / Ω ± ω N b between the vibration responses of adjacent blades. Then, we found that the swing motion intensifies the difference of transverse deformations along the chord direction of wide-chord blades with tip-rub, which may induce the edge failures. Also, the swing motion intensifies the steady rub-impact fault. It could weaken or eliminate its divergence and instability when the rotor with multiple wide-chord blades is unstable. The gyroscopic effect could weaken the swing motion, and then weakens the stable rub-impact fault.

High speed motor with magnetic bearings has been developing due to its advantages of small size, high power density, no mechanical wear and low maintenance cost. In order to reduce vibrations, dynamic characteristics of the flexible rotor system of high speed motor for operation rotation speed 200000r/min with magnetic bearings are investigated. Results show that high speed motor may pass through some critical speeds and it is accurate to consider the motor shaft as a flexible rotor. Meanwhile, it is necessary to take measures to reduce the amplitude of resonance region of high speed motor such as increasing system damping. The critical speed increases with the increase of the bearing stiffness, which is a good way to remove the critical speed below working rotation speed.

In a hypersonic wind tunnel, the motion of the electric putter Y mechanism needs to be controlled synchronously, and the accuracy or control performance of the system's synchronous motion control directly affects the running quality of the wind tunnel. Based on the deviation coupling mechanism of output displacement, the paper puts forward the synchronous control system of the model mechanism electric putter Y mechanism, and establishes the dynamic model of the mechanical system, current control ring, speed control ring and position control ring of the electric putter Y mechanism. A closed-loop synchronous three-ring control system is designed, and performance simulation is carried out. The results show that the system has fast synchronous response speed, high accuracy of synchronous displacement and synchronous speed control, and the system has strong robustness.

In some products or systems, the redundant parts, components or subsystems must be configured for their high reliability, in addition to the high reliability of parts and components. But the systems would pay more "cost" of resources such as cost, weight or volume, than those without redundancy of parts, components and subsystems. Therefore, the study of redundant reliability optimization for the system would be carried out. This paper presents several models for basic component structures of reliability based on the block diagram. According to the block diagram model for series-parallel reliability of components and subsystems, a mathematical model and its optimization method for system redundant reliability optimization are established, which are based on dynamic programming. Then the ball screw actuator system was taken as an example, and the redundant reliability of its parts or subsystems was calculated with the dynamic programming method based on the control sequence method. And the optimized result of the ball screw actuator system was gotten with the system constraints conditions. The redundancy of components at all levels is obtained with the greatest reliability.

Incoming wakes significantly affect vibration characteristics of rotating blades in turbomachines. This paper develops a periodic incoming wake mathematical model to consider the influence of pressure variations. Considering thickness variations along both the chord to reduce vibrations and the span to decrease centrifugal stress, a wake-induced vibration model based on rotating large deformation cantilever plates is established. Natural frequencies calculated by different methods show that the present method has a high degree of accuracy. And analysis of incoming wake-induced vibrations indicates the incoming wake model can analyze effects of important parameters of such wakes on vibration characteristics. With the aggravation of wakes induced-vibrations, geometric nonlinear vibrations become more remarkable, which indicates the necessity of large deflection analysis. Discussions on variable thickness demonstrate that increasing thickness on the fixed end or maximum thickness along the chord not only reduces vibrations caused by incoming wakes, but also decreases the centrifugal stress, which are two better ways to reduce this kind of vibrations.