According to a problem of the vibration and noise suppression of an engineering vehicle cab, a dynamical model of the engine-frame-cab system was established to describe the vibration transmission path. The method of calculation of the vibratory power flow, which is transmitted from the vibration source engine to the cab through the frame and isolators, was deduced. And then an optimization strategy for the frame structure and the corresponding analysis algorithm process were proposed based on the objective function of power flow. The method proposed was validated through an application to a practical example, which would have practical value in the field of vehicle vibration reductions and optimization design of frame structures.

The application of double-layer shell structure is very common in some situations that require complex loads and vibrations, such as key components such as the shell and wings of aerospace engines, and the shell of underwater vehicles. Many authors have conducted research on the vibration and acoustic radiation characteristics of double-layer cylindrical shells. By adding reinforcement and ribs between the double-layer cylindrical shells and optimizing structural design, passive vibration control techniques can effectively solve high frequency vibration problems, but the impact on mid to low frequency vibrations is still limited. Therefore, this article conducts theoretical research on a novel active vibration control method that inserts an active actuator between a double-layer cylindrical shell to achieve better mid low frequency vibration control effects. Firstly, the substructure admittance method is applied to analytically and dynamically model a double-layer cylindrical thin shell structure with active support, and the vibration power flow of the system is theoretically derived to evaluate the vibration reduction effect. Then, numerical simulation analysis was conducted on the influence of different configurations of six feedback control parameters, time delays, and other factors on the vibration power flow. Finally, based on the image, the conclusion is drawn that all six feedback control parameters can improve the vibration control effect of the coupled system to a certain extent, but not every feedback control parameter has a prominent effect, and the effective range of some parameters is relatively narrow.

Cylindrical shells containing complex elastic coupling systems are the main structural form of underwater vehicles. Therefore, in this paper, the vibroacoustic radiation problem of underwater cylindrical shells containing complex internal elastic coupling systems is studied. Firstly, the dynamics model of the complex elastic coupled system is established through the method of integrated conductivity. The sound pressure distribution law and the general magnitude relationship between the performance index of hydroacoustic radiation and vibration isolation are investigated through numerical simulation. A strategy of global sensitivity analysis and related parameter optimization is carried out, by applying the Sobol’ method to the dynamics model. It could be concluded that the main flap of sound pressure at low and medium frequencies appears in the direction of the excitation force or the perpendicular to the excitation force, the magnitudes correspondence between the vibration level drop—power flow—hydroacoustic radiation at low frequencies can be expressed as a relatively simple function, and the vibroacoustic transmission of the system at lower order resonance frequencies is dominated by the parameter configuration of the vibration isolation device, while at higher frequencies is more influenced by the modalities of the base structure. The transfer power flow and the level drop are used as objective functions to optimise the acoustic radiation index of the coupled system, with the best results obtained when the transfer power flow and the level drop are used together as objective functions.

The low-frequency vibro-acoustic characteristics of a mechanical equipment-floating raft-cylindrical shell-underwater acoustic field coupled system with nonlinear supports are studied in this paper. Firstly, the state space equations were established by a modal superposition theory for the coupled system, and a modal parameter identification method was deduced and verified for the cylindrical shell-underwater acoustic field coupled subsystem. On this basis, the formulas were derived for transmitted power flow in the coupled system, and the nonlinear stiffness constitutive relation of the vibration isolation supports was expressed by softening and hardening characteristics. Finally, dynamic simulations were carried out by the Runge-Kutta method to analyze the effect of nonlinear stiffness characteristic parameters on the low-frequency vibration modes and vibro-acoustic transfer characteristics in the coupled system. The research shows that a superharmonic phenomenon is common in the steady vibration mode of the coupled system with a nonlinear softening (or hardening) stiffness characteristic under harmonic excitation. The stronger the softening (or hardening) stiffness characteristic is, the more complex the vibration form is, and the smaller (or larger) the low-frequency vibro-acoustic transfer level in resonance regions is.

The double-layer plate structure in passive sound insulation systems can improve the high-frequency sound insulation performance, but it is still not ideal in the low-frequency region. The actuator of the active sound insulation system can adjust the stiffness and damping in real time, with strong adaptability and adjustability. Therefore, in this paper, active actuators and feedback control strategy are applied to a double-layer plate structure to improve the low-frequency sound insulation performance of a water-filled acoustic cavity system. The theoretical model of a sound insulation system with a double-layer plate structure and active feedback control strategy is established for a water-filled acoustic cavity. The average energy transfer is used as an evaluation index for the active sound insulation effect of the system, and the calculation method of this index is derived. Then, the MATLAB numerical simulation is used to analyze the effect of six feedback control parameters on the average energy transfer of the system. Finally, it is concluded that when the feedback parameters are within the effective range, all six feedback control methods can produce significant effects on the low-frequency sound insulation of the system, but the effective range of some parameters is narrow.

Propulsion shafting plays an important role in the overall structure of naval ships. The control effect of shafting vibration determines the safety performance of the ship to a great extent. The dynamic characteristics of the sliding bearing distributed on the shaft, especially the stiffness, have a significant influence on the vibration transmission characteristics of the propulsion shafting. The study of the influence of bearing stiffness characteristics on the coupling vibration of propulsion shafting and hull is beneficial to promote the optimal design of shafting and improve the safety performance of ships. In this article, according to the general structure of ship propulsion shafting, the theoretical model of ship-shaft coupling system bending vibration is established, and the calculation model of average energy input of each shaft section is deduced. The oil film stiffness characteristics of various bearings on the stern drive shaft are simulated and analyzed. The results show that the bearing liquid film stiffness is proportional to the shaft speed and inversely proportional to the main resonance peak frequency. The stiffness of bearing liquid film is proportional to the strength of low frequency vibration energy transmission dissipation, but has little effect on the dissipation process of high frequency vibration energy transmission.

采用CFD方法计算目标螺旋桨的敞水性能,通过Fourier变换得到轴承激振力的频域特性.结合舰艇推进轴系的一般结构形式,建立桨—轴—艇耦合系统纵向振动动力学模型,将先前计算所得的螺旋桨激励特性与振动能量传递相结合,讨论了纵向振动形式下螺旋桨激励振动功率流的传递和振动能量传递耗散的特性,从能量角度分析纵向振动在系统耦合振动中的影响,进而基于模拟工况探讨振动能量在轴系耦合振动中的传递机理.

Dynamics of mechanical system has received more and more attention in the undergraduate and postgraduate course of mechanical specialties.And how to improve the quality of education through case teaching has become a mutually concerned subject of teaching methods reform.In view of shortage of combination of theory and practice in current mechanical dynamics teaching, through a concrete example of dynamics modelling and simulation with Simulink of a propelling shafting-hull coupled vibration system, the paper makes a discussion about the fundamental work of case teaching, i.e. the design and writing of novel teaching cases, including synthesizing the basic problems and methods of dynamics with practical engineering cases, transforming complicated engineering system into mechanic model, choosing study breakthrough point and analysis key point, constructing an integrated environment of modelling, simulation and analysis of dynamical system by theoretical analysis and software aided calculation, etc..And the problem and its resolution of practical complicated flexible coupled dynamics system is demonstrated in classroom via visualized simulation.

对于舰船推进轴系的螺旋桨激励,由于其工作环境和结构条件的限制,很难在实际工况下进行直接测量.通过测量轴系的振动响应对螺旋桨激励进行估计是一种可行的方法.本文根据激励反演理论,从推进轴系的一般结构形式出发,提出了适用于由轴系振动响应估计螺旋桨激励的理论模型.由等截面均匀轴入手,通过轴段的波动解来分析纵向振动;结合边界条件,推导了波幅系数递推关系,进而建立了推进轴系纵向振动的一般波导模型.根据振动响应和建立的波导模型来识别波幅系数,并反演螺旋桨纵向激励.将模态法与波导法相结合,对一般的变截面非均质轴段的波导模型和轴段间波导传递关系进行了论证.结果表明,模态法与波导法结合,可作为一般方法,根据实测振动响应对复杂轴系结构的波导模型进行识别.

The work of this paper is aiming at a reasonable description or hypothesis of mechanical platform excitation of sonar array cavity on board the ship, which is necessary for comprehension of mechanism of the mechanical self-noise in sonar cavity. Through analytical deduction of the mechanical excitation transfer function between the source equipment and the sonar platform in a SPR (Source-Path-Receiver) system and corresponding numerical simulation, the excitation transmission characteristics is investigated. It is proved that weaker coupling between the solid sound propagation path and the sonar platform is essential for attenuation of sonar platform excitation. And in the condition of weak coupling, the excitation transmitted to the sonar platform is mainly dependent on the intrinsic vibration mode of the solid sound path.

Affected by some difficult factors such as bearing stiffness and lubricant film stiffness and so on, the calculation of the lateral vibration response of the ship shafting is difficult to guarantee high calculation accuracy. A mathematical model of the propulsion system-submarine hull coupling bending vibration was established by mathematical physics, and the bearing excitation of the propeller was calculated. A mathematical model of the bending vibration response of the propulsion shaft system and the transmission of vibrational power to the hull was established to calculate the transmitted power flow. The vibration response and bending vibration power flow of the shafting under the lateral excitation of the propeller were solved. Through MATLAB simulation calculation and analysis, the influence of system parameter variation on the bending vibration flow transmission of each node in the power flow transmission path was obtained.

The mechanical self-noise of the sonar is one of the important factors affecting the performance of the sonar. Therefore, studying the prediction of the mechanical self-noise of the sonar is of far-reaching significance for the effective performance of sonar detection. In this paper, the theoretical modeling of the propagation channel is carried out, and the transfer characteristics of the excitation of the vibration source device into the sonar platform region are numerically simulated. A method for predicting the mechanical self-noise of the sonar part based on the equivalent excitation spectrum analysis is proposed.

The work of this paper is backgrounded by prediction or evaluation and control of mechanical self-noise in sonar array cavity. The vibratory power flow transmission analysis is applied to reveal the overall vibration level of the fluid-structural coupled system. Through modal coupling analysis on the fluid-structural vibration of the fluid-filled enclosure with elastic boundaries, an efficient computational method is deduced to determine the vibratory power flow generated by exterior excitations on the outside surface of the elastic structure, including the total power flow entering into the fluid-structural coupled system and the net power flow transmitted into the hydroacoustic field. Characteristics of the coupled natural frequencies and modals are investigated by a numerical example of a rectangular water-filled cavity with five acoustic rigid walls and one elastic panel. Influential factors of power flow transmission characteristics are further discussed with the purpose of overall evaluation and reduction of the cavity water sound energy.

Detection of sonar platform excitations has been a formidable obstacle towards the estimation and evaluation of mechanical self-noise in the sonar cavity. In view of the complexity of transmission of excitations from mechanical vibration equipments to sonar platform, an inversion technique, i.e., indirectly estimating the outside excitations by means of measurement of vibratory responses, would be the most applicable and feasible. An equivalent excitation method is proposed in this paper, by the hypothesis that responses resulted from equivalent excitations would be equal to that from actual excitations, to deal with the excitation inverse problem in situations where there is no knowing about the location and distribution of dynamic excitation forces acting on structures. Influential factors in estimation of equivalent excitations, including determination of master modals, number and arrangement of observation points and equivalent excitation points, are well reasoned based on modal theory of panel structures, with analytical analysis method. And it could be concluded that the equivalent excitation inversion would be a practical method for evaluation of environmental excitations.

Considering increase of stiffness caused by size effect, equivalent Young's modulus was introduced for futher analysis. Experimental platform was established to test vibration characteristics. Dynamic equation for micro piezoelectric cantilever beam considering size effect was studied with finite element analysis and experiment. Results shows it is accurate. Based on that, dynamic model for micro vibration energy harvester was improved, a T-type micro vibration energy harvester was designed and fabricated. Resonant frequency, tip displacement and output voltage of the harvester were obtained. Comparing with macroscopic model for vibration harvester, improved one reduces errors by 13%, 35% and 22%.

In this paper, the characteristics of the mechanical self - noise in sonar array cavity are studied by using the elastic flatbed - filled rectangular cavity parameterization model. Firstly, the analytic derivation of the vibration differential equation of the single layer, sandwich elastic wall plate structure and internal fluid coupling is carried out, and the modal method is used to solve it. Finally, the spectral characteristics of the acoustic field of rectangular cavity of different elastic wallboard materials are simulated and analyzed, which provides a theoretical reference for the prediction and control of sonar mechanical self-noise. In this paper, the sandwich board as control inside the dome background noise of a potential means were discussed, the dome background noise of qualitative prediction analysis and control has important theoretical significance.

In the plastic injection molding process, the barrel temperature as a key factor affects the product quality directly.According to the characteristics of the barrel heating system, a variable universe adaptive fuzzy PID control system was designed, combining the thought of variable universe and the adaptive fuzzy PID control method.The modeling and simulation analysis in the Matlab were carried on, as well as the operational temperature data was analyzed among variable universe adaptive fuzzy PID, adaptive fuzzy PID and traditional PID.The results showed that the variable universe adaptive fuzzy PID control system had the optimal dynamic and steady performance, highest actual temperature accuracy ,up to±0.2℃.

A novel type energy harvester composed with n masses and n beams was proposed to solve the problems of high-frequency and narrow band of cantilever energy harvester to improve its energy conversion efficiency, and broaden its application. Firstly, We taken micro beam as the research object, improved its dynamic model with size effect, then verified it by experiments. Secondly, the dynamic model was established based on the improved one, and its response and the output voltage of the external excitation was deduced formula. Finally, the performance was studied when n=2. The results show that resonance frequency was obvious reduced, and there are two frequency points less than 50Hz, 15.25 Hz and 23.08 Hz. Moreover, when the effective output voltage reached 80 mv, the effective frequency band was 20.32 Hz, which can make up for the energy conversion efficiency of single resonant frequency harvester.

In view of the destructive influence of mechanical self-noise on sonar's detection capability at lower frequencies, a parametric model composed of panels and a water filled rectangular cavity is established for investigation of characteristics of hydroacoustic field caused by mechanical excitation loaded on sonar platform area. The analytical derivation and numerical simulation analysis of differential vibration equations provide theoretical reference for prediction and control of mechanical self-noise.

T he meshing gear subsystem of bend torsion coupling vibration model ,the axis subsystem of elastic bending vibration and torsional vibration model and the elastic box board subsystem of transverse vibration model are established to get the w hole vibration model through the bearing multi‐dimensional stiffness matrix and deformation coordinate relations between the subsystems .Phase diagram and poinca‐re map are utilized here to get the movement characteristics of gear box system .And vibration energy is also studied by theory of power flow to have a better understanding of the system performance influenced by the external motivation ,bearing stiffness ,which provides a new analysis method and theoretical basis for vibration control and structure design of gear box system .