The Short Time Transient Responses And Power Flow Control Of Structures With Finite Size Based On The Wave Theory

With the development of the aerospace project, the spacecraft structures become more complicated, and more and more initiating explosive devices are used. The high level acceleration in early short time can be produced by the shock of the initiating explosive devices and it may cause damage to the sensitive electronic instruments housed in the spacecraft structures, which may lead to the catastrophic accident of spacecraft. Meanwhile, the spacecraft take on more and more tasks, and the requests for the control precision and stability of the spacecraft also become stricter. The medium and high frequency disturbances in the spacecraft become prominent increasingly. The structural power flow can be effectively used to describe the medium and high frequency disturbance propagation in structures. Consequently, in order to insure the spacecraft working in the more secure and stable environment, it is very important to investigate the structure early short time transient response subjected to the impact loads and the propagation and control of the structural power flow.For the solution and analysis of the early short time transient respones which mainly contain the high frequency response, the steady finite element method and mode superposition method are not applicable, and the analysis methods based on the wave theory are always used. Many works have been done on the investigation, while it is not enough to study the early short time transient response and the power flow control of structures with finite size. Recently, to our best knowledge, there has been no published work on the early short time transient responses for finite plate structures under the impact loads by the generalized ray method (GRM) and the method of reverberation ray matrix (MRRM).In this paper, the early short time transient response and the power flow control of finite structures are investigated. The existing analysis methods on the basis of wave theory are developed. The GRM and MRRM are used to study the early short time transient responses for finite plate structures under the impact loads, which provide an effective approach for solving problem of the kind. The main contents in this paper are as follows:Firstly, the generalized ray method (GRM) and the method of reverberation ray matrix (MRRM) are extended to investigate the early short time transient response of finite plate structures subjected the impact loads. The GRM and MRRM have been effectively and accurately employed to study the transient responses in the beams, planar trusses and space frames. In this paper, based on the Mindlin plate theory, the ray groups propagating in the finite rectangular plate under the impact loads are determinded by the GRM. The ray groups propagating in the finite L-shaped plates are studied by the GRM and MRRM. The early short time transient responses of the finite plates are calculated, and the effects of the plate thickness, material properties, and different shock signals on the early short time transient responses of the finite plates are also analyzed. Comparing with the experimental results, the analytical results of the early short time transient response of finite plate structure are validated.Secondly, based on the study of above chapter, the MRRM is extended to research the early short time transient responses of the stiffened laminated composite plates subjected to impact loads. Through the Laplace transform, on the basis of the first order shear deformation laminated plate theory, each ray group propagating in the stiffened laminated composite plates can be studied by the MRRM. The early short time transient responses of the rib-stiffened laminated plates under various impact loads are calculated by the FFT algorithm. Furthermore, the influences of the stiffener number and different impulse signals on the early short time transient responses of the stiffened laminated composite plates are also studied.Thirdly, the GRM and MRRM are extended to investigate the early short time transient responses of laminated composite cylindrical shells with finite size under impact load. Based on the first order shear deformation shell theory and Laplace transform, the ray groups transmitting in the laminated cylindrical shells under the shock load are yielded by the GRM and MRRM. The early short time transient responses of the laminated composite cylindrical shells under impact loads are calculated using the FFT algorithm, and the results by the GRM are compared with those by the MRRM. Moreover, the effects of the thickness and stacking sequence of the composite cylindrical shells and impulse types on the early short time transient responses of the laminated composite cylindrical shells are also analyzed.Fourthly, the structure vibration control based on the reactive power flow is presented in this paper. Many researchers have studied the propagation and control problems for structural active power flow. In this paper, we calculate the medium and high frequency dynamic resonpses for beam structures by the wave method, and analyze the physical meaning of the structural active and reactive power flow in detail. The active vibration suppression of the finite L-shaped beam is performed based on the structural active and reactive power flow, and acceleration response. It can be seen that the structural vibration can be effectively suppressed by the active control for minimizing the reactive power flow. The effects of the locations of error sensor and the small error of the control forces on the control results are also analyzed.Finally, we investigate the active control of vibration power flow in finite coupling connected plate structures. Much attention has been formerly paid to the power flow of the beam-like and plate-like structures, to our knowledge, there has been no published work on the active control of power flow transmission through the junction of the finite coupling connected plate structure in the open literatures. In this paper, on the basis of the classical thin plate and Mindlin plate theories, the structural active and reactive power flow of finite coupling plates are investigated by the wave method, and the effect of the structural damping on the active and reactive power flow is also studied. The active power flow at the junction of the connected plate is suppressed by the feedforward active vibration control, and the effect of small error of the control forces on the control results is also studied.