Papers by Author: Zhi Chun Yang

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Authors: Ming Yang, Zhi Chun Yang
Abstract: To penetrate into the study of POGO vibration, by taking the LRC equivalent circuit analyzing method, based on two boundary conditions in document [, taking the flow pulse drive into consideration, this paper proposes four boundary conditions specific to the propelling flow system in liquid rockets, and at the same time, complements the mathematic model. Further, by way of network function, under the liquid system flow parameter, this paper infers transfer function expressions, and makes the accurate solution of the natural frequency under every boundary condition. At last, from the statistic point of view, by the method of correlation coefficient, this paper studies the influence that the flow parameter may have on the system natural frequency, and set the major influential liquid flow parameter to the system natural frequency of liquid propelling flow system in liquid rockets.
Authors: Yuan Dong Li, Xin Ping Zhang, Ying Song Gu, Zhi Chun Yang
Abstract: Normal mode and flutter analysis are conducted for a high aspect ratio aft swept flying wing model, and body freedom flutter is found to be the most critical aeroelastic instability for this air vehicle model. To determine the influence of various kinds of design parameters on BFF characteristics, eight factors are considered in the parametric study, i.e. wing vertical bending stiffness, weight and center of gravity of the wing root payload and the wing tip mass balance, wing half span, aft swept angle and the station of wing body blended line. After the parametric analysis, the mass and center of gravity of the wing root payload are selected as design variables, and the baseline model is utilized in the design optimization study subject to critical flutter speed constraint. Finally, the optimal mass balance design is suggested to suppress the body freedom flutter phenomenon passively and maximize the payload.
Authors: Zhe Feng Yu, Zhi Chun Yang
Abstract: A new method for structural damage detection based on the Cross Correlation Function Amplitude Vector (CorV) of the measured vibration responses is presented. Under a stationary random excitation with a specific frequency spectrum, the CorV of the structure only depends on the frequency response function matrix of the structure, so the normalized CorV has a specific shape. Thus the damage can be detected and located with the correlativity and the relative difference between CorVs of the intact and damaged structures. With the benchmark problem sponsored by ASCE Task Group on Structural Health Monitoring, the CorV is proved an effective approach to detecting the damage in structures subject to random excitations.
Authors: Yang Gao, Zhi Chun Yang, Jiang Xie
Abstract: This paper investigates the stability issues of functionally graded material (FGM) panels subjected simultaneously to both aerodynamic and thermal loads. Finite Element Method is employed to model the panel structures and the supersonic aerodynamics is calculated by the first-order piston theory. The critical buckling temperature elevation of the panels is at first predicted. The nonlinear static analysis of the panels is then implemented at certain interval of temperature elevation before buckling onset to obtain structural stiffness matrix. The flutter speed of the panels with updated stiffness matrix corresponding to a certain temperature elevation is estimated. The results show that the FGM panels can offer beneficial effects, especially prevention from buckling. However, if FGM panels integrated with TPS are to be applied on supersonic vehicles, one should pay more attention to the boundary conditions to guarantee the dynamic stability.
Authors: Ying Song Gu, Zhi Chun Yang
Abstract: Mu method is a flutter solution technique based on frequency domain mu-analysis, which directly applies perturbation to dynamic pressure in aeroelastic equation of motion. In a previous study, the dynamic pressure perturbation was modeled as a purely real uncertainty, which could not guarantee the continuity of mu. To improve the continuity of mu, a small amount of complex perturbation is added to the dynamic pressure in addition to the real perturbation. Thus the mu method is improved with this mixed real/complex perturbation. Formulations and algorithm of the improved method are presented and validated with sample test cases. It is demonstrated that the improved mu method is more feasible and conservative than the original mu method due to the mixed perturbation.
Authors: Zhi Chun Yang, Wei Xia
Abstract: An investigation on the stability of heated panels in supersonic airflow is performed. The nonlinear aeroelastic model for a two-dimensional panel is established using Galerkin method and the thermal effect on the panel stiffness is also considered. The quasi-steady piston theory is employed to calculate the aerodynamic load on the panel. The static and dynamic stabilities for flat panels are studied using Lyapunov indirect method and the stability boundary curve is obtained. The static deformation of a post-buckled panel is then calculated and the local stability of the post-buckling equilibrium is analyzed. The limit cycle oscillation of the post-buckled panel is simulated in time domain. The results show that a two-mode model is suitable for panel static stability analysis and static deformation calculation; but more than four modes are required for dynamic stability analysis. The effects of temperature elevation and dimensionless parameters related to panel length/thickness ratio, material density and Mach number on the stability of heated panel are studied. It is found that panel flutter may occur at relatively low aerodynamic pressure when several stable equilibria exist for the aeroelastic system of heated panel.
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