The camshaft is an important component that ensures the timely opening and closing of valve in marine diesel engines. Due to the poor contact lubrication state and excessive friction excitation，it is easy to cause larger interface torque on the camshaft. Considering the effects of transient excitation and interfacial friction，the tribo-dynamics model of the valve camshaft in V20 diesel engine is established. The forced vibration results of the camshaft are obtained，and the friction and lubrication performance of the cam-tappet pair is also analyzed under the fluctuating speed. The results show that，by thoroughly considering both the transient excitation and frictional excitation of each cam pair，the additional stress in each shaft section of the valve camshaft increases by about 4 MPa，while the transient speed fluctuation at the camshaft end increases by roughly ±30 r/min. Under the combined effects of speed fluctuation and surface roughness，the film thickness is dramatically reduced in some positions，especially in the cam base circle section where the film thickness decreases by about 0.3 μm. At the reverse motion position and nose of the cam，the temperature rise at the interface of the tappet exceeds the material’s scuffing temperature，thereby increasing the risk of scuffing wear.

Four multi-disk rotors with the same structure size are used as the research basis. The precision wire cutting method is used to prefabricate transverse cracks of different depths at different positions of the four rotors. The vibration characteristics of the cracked rotor system with changed crack parameters are tested and the relationship between the dynamic response characteristics of the cracked rotor and the crack location and crack depth is analyzed. The test results show that the 2× resonance phenomenon in the 1/2 critical speed zone and the 3× resonance phenomenon in the 1/3 critical speed zone are the typical characteristics of the rotating shaft crack failure. The 2× resonance peak value increases rapidly after the crack depth reached a critical point. While the 3× resonance peak value，which is different from the results of existing studies，drops abruptly after the crack depth reached a critical point. Also，there is a correlation between the critical depth that triggered an abrupt change in the peak 2× and 3× resonance and whether the crack location is at the root of the disc.

Rotor dynamic response sensitivity analysis is widely used in rotor model updating，parameter identification and structural optimization. In this paper，a first-order，second-order and mixed sensitivity analysis method for dynamic response of rotor system based on multi-complex domain perturbation method is proposed. The design parameters are perturbed in two complex directions respectively，and the motion equation of the rotor system in the double complex domain is obtained. Using the real matrix expression of the complex number，the complex motion equation is extended to obtain the equivalent real motion equation. By solving the equivalent real motion equation，the system response，first-order sensitivity and second-order sensitivity can be obtained simultaneously，and the Hessian matrix of dynamic response sensitivity can also be obtained. The numerical simulation analysis of single-disk rotor system and gas generator rotor system is carried out to verify the correctness of the rotor dynamic response sensitivity analysis method of multi-complex domain perturbation method. Compared with the traditional finite difference method，the multicomplex domain perturbation method shows insensitivity to the error caused by the perturbation step size，and the solution accuracy is higher.

The energy transfer efficiency and energy dissipation of coupled piecewise linear stiffness energy sink are studied. The equation of systematic slow-varying equations of the two-degree-of-freedom system coupled with the piecewise linear stiffness energy is derived by the complex variable-averaging method under 1∶1 internal resonance. The approximate expression of two extreme points of the slow-invariant manifold is obtained by using the polynomial approximation method，and the energy transfer efficiency equation and energy dissipation equation of the coupled piecewise linear stiffness energy sink system are obtained. The effects of piecewise gap and piecewise linear stiffness on energy transfer efficiency and the relationship between damping coefficient of the main structure and dissipation time are analyzed. The results indicate that the energy transfer efficiency of the system decreases as the piecewise gap of the coupled piecewise linear stiffness energy sink increases，while it increases with an increase of piecewise stiffness. Additionally，it decreases with an increase of the damping system of the main structure. Therefore，adjusting structural parameters，the piecewise linear stiffness energy sink can effectively mitigate vibrations within the main structure.

In order to grasp the influence of wear clearance of spherical pair on dynamic response characteristics of spatial parallel mechanism，a dynamic modeling and response analysis method for spatial parallel mechanism considering the wear of spherical joints is proposed. The 3SPS-S spatial parallel mechanism is taken as the research object. The wear model of the spherical joint clearance is established based on the Archard wear model，the worn ball head and ball socket are obtained by calculating the wear depth and surface geometric reconstruction，and the dynamic model of the parallel mechanism considering spherical joint wear is established. The numerical results are obtained by solving the above dynamic model. The change of dynamic response of mechanism before and after wear is compared and analyzed，and the influence of initial clearance value and load on dynamic response of mechanism after wear is obtained. The results show that the worn irregular clearance has adverse effects on the dynamic characteristics of the parallel mechanism，and the increase of clearance value and the introduction of load can reduce the stability of the parallel mechanism.

Ultra-long beam structure has large vibration frequency span. To control the wide frequency vibration of ultra-long beam structures，amplitude-enhanced dynamic vibration absorbers with damping are arranged periodically on the beam. The amplitude magnification device artificially magnifies the amplitude at the controlled point，thereby increasing the operating ability of the absorber. To be able to consider the effect of damping，a complex band structure analysis model is established，and a new complex band structure calculation method is proposed based on the artificial spring model and the energy method. This method is used to analyze the effect of amplification device type，absorber damping and magnification factor on the complex band structure in detail. The effect of the relative position of the connection points of the ungrounded magnification device on its vibration damping performance is studied. The results show that the magnitude amplification device type，absorber damping and magnification factor have great influence on the complex band structure. The suitably relative position can significantly improve the working ability of the ungrounded magnification device.

The vibration reduction efficiency of a tuned mass damper（TMD）is closely related to the inherent parameters of the structure and TMD. Accurate identification of the structure and TMD inherent parameters from the response of the structure-TMD coupling system is necessary for the evaluation of the vibration reduction performance of in-service TMD. This paper offers a parameter identification approach based on NSGA-Ⅱ（Nondominated sorting genetic algorithm）that can identify the parameters of‘bare structure’ and‘bare TMD’ from the coupled structure-TMD response in order to solve the issue of state evaluation of TMDs in service. The structure-TMD coupling equation is constructed. It is reduced and transformed into a two-degree-of-freedom system of the structure-controlled mode and TMD coupling. Two objective functions are constructed by means of the system state space matrix. The genetic algorithm is used to find the optimal solution corresponding to the minimum error between the theoretical value and the experimental value，so as to identify the modal parameters of the structure and TMD. The numerical simulation analysis of parameter identification of single-degree-of-freedom structure-TMD coupling system and multi-degree-of-freedom structure-TMD coupling system is carried out. The results show that the proposed method can accurately identify the inherent parameters of structure and TMD from the dynamic system response of the coupling system.

The axial compression of the landing gear strut can directly lead to the change of system stiffness and rotational inertia，but the effect of strut axial displacement is mostly ignored in existing models of nose landing gear shimmy. A nonlinear dynamic model of six-degree-of-freedom dual-wheel nose landing gear shimmy with axial displacement and longitudinal bending of struts is established. The bifurcation theory is applied to study the effect of introducing axial displacement on the shimmy region，and the maximum compression stroke of the buffer is combined with sliding speed，vertical load，and wheel rotational inertia，respectively. The combined parameters are analyzed by two parameter bifurcation. The fourth order Runge-Kutta method and fast Fourier transform are used to calculate the time-frequency characteristics in the stable shimmy region，and the interaction between the degrees of freedom of torsion，lateral bending，and longitudinal bending of the strut is studied. The results show that under certain conditions，considering the influence of axial displacement of the strut，the areas of torsional and lateral shimmy of the strut have a tendency to shrink. In the bistable region of double wheel nose gear shimmy，when the initial excitation is close to zero equilibrium state，the longitudinal shimmy occurs near 2 times the natural frequency of torsional vibration. When the initial excitation is far from the zero equilibrium state，longitudinal shimmy occurs near 2 times the natural frequency of lateral vibration.

In response to the galloping issue faced by ice-covered multi-split transmission lines，this study proposes a method based on the probability density evolution approach for dynamic tension stochastic analysis and reliability evaluation of such transmission lines. A stochastic analysis method for the dynamic tension in ice-covered multi-split transmission lines is established by integrating the finite element model with the probability density evolution technique. A tensile failure criterion for ice-covered multi-split transmission lines is developed by using the equivalent extreme value distribution method，and a framework for reliability evaluation of the transmission lines is constructed. Stochastic dynamic response analysis and reliability evaluation on a single-span ice-covered four-split transmission line are conducted. The analysis of the example shows that：The method in this paper can efficiently analyze the stochastic dynamic tension of the ice-covered four-split transmission line，and the stochastic dynamic tension is influenced by multiple modes after the transmission line enters the stable galloping stage；The tensile failure reliability probability of transmission lines during galloping does not exhibit a monotonous relationship with the increase of initial sag；The initial wind attack angle plays a crucial role in determining the tensile failure reliability probability of the transmission line，and the reliability of the transmission line is relatively low when the initial wind attack angle falls within the range of 20° to 60°.

The wind uncovering effect of the roof of a large-span terminal building is one of the important factors affecting its structural safety. Existing studies only consider the benign wind climate and static wind load effects，which are difficult to explain the real wind uncovering pattern and occurrence mechanism of the roof structure under the strong typhoon dynamic load. Based on WRF，CFD and LS/DYNA，this paper carries out the numerical simulation of continuous wind damage of a large-span terminal building under the action of typhoon. The wind field simulation of typhoon "Hegeby" was carried out firstly. The continuous wind uncovering process of the terminal roof under the typhoon was simulated by taking an international airport terminal building as an example，and the wind damage pattern and wind damage rate of the roof cover under different wind angles were compared and analyzed to reveal the wind damage mechanism of the large-span terminal building under the typhoon. The results show that the extreme wind pressure at the windward edge of the terminal roof is higher，and the effect of upward and downward pressure is obvious，and the maximum pressure difference coefficient is 12.41. When the critical wind speed is reached，the windward edge of the roof is partially lifted by the wind，and then the "chain effect" triggers the continuous wind damage of the roof，and the tearing direction of the roof is consistent with the incoming flow direction. The energy failure index K is given based on the law of internal energy change before and after the failure of roof units，which can be used to guide the design of large-span terminal building roofs against wind uncovering.