Study On Wrinkling And Dynamic Characteristics Of Space Membrane

Winkles exist extensively in space membrane structures as a local buckling phenomenon. For high precision membrane structure, wrinkles are the main factors related close to the surface accuracy. At the same time, wrinkles may have significant influences on the stability of the structure and dynamic characteristics of the structure. Nowadays, with the development of high precision membrane structure's application research, the studies on the wrinkling problem have become a hot topic.Tension field theory is the earlier membrane wrinkle theory. This method introduced parameters to modify the constitutive relation on the membrane wrinkle's region so as to avoid the compressive stress on the membrane. Winkle problem of tension membrane can be solved by tension field theory very well. Due to that wrinkle analysis based on tension field theory can not achieve the out-of-plane deformation of wrinkles; it is not suit for wrinkle analysis requirement of high-precision space membrane structure.In order to describe the out-of-plane deformation accurately, the concept of wrinkle configuration is proposed in this paper. Parameters such as wavelength, amplitude and direction of the wrinkle are used to describe the wrinkle configuration. According to nonlinear large deflection equation, a general approach Stress Extreme Method(SEM) is established to describe the wrinkle configuration parameters. The relationship between half-wavelength and tensile stress of wrinkle's direction is established. The relationships between wrinkle configuration parameters are then determined. Shear membrane wrinkle and rectangular membrane under corner load are studied by using stress extreme method, and the wrinkle's configuration parameters are obtained in the end.The wrinkling process of membrane is divided into two stages: the initial buckling and the post-buckling. The mechanism of wrinkle's formation and expansion are analyzed in theoretical corresponding to these two different stages. The critical load formula of shear membrane at the initial buckling stage is established and the principle of wrinkle's formation and expansion are then studied at this stage. For the analysis of post-buckling process, initial imperfections will be introduced into the analysis of the membrane wrinkle. The analytical model of membrane wrinkle within initial imperfections is then established, and the law of stress distribution in wrinkle region is analyzed finally. According to the obtained law, expansion process of wrinkling mechanism in the post-buckling is then researched. Combined with theoretical analysis, the probably second buckling phenomenon is also discussed in the post-buckling.Based on the stability theory, a numerical analysis method Direct Disturbances Method is established to analyze the membrane wrinkle, and this method deals with the problem of unremoved imperfections in the conventional nonlinear buckling analysis. Using the direct disturbance method, the critical load in the initial buckling process and the law of wrinkle's formation and expansion are analyzed. The configuration parameters of membrane wrinkle at post-buckling process are obtained. The balance path of the membrane buckling is also studied. By using numerical method, the secondary buckling phenomenon is researched both in initial buckling process and post-buckling process. The comparison between numerical analysis and theoretical analysis is done in the end.The experimental study of shear membrane wrinkle is performed by using digital photogrammetry system. Through digital photogrammetry system, non-contact measurement of small out of plane deformation can be obtained. The experimental device of shear membrane is designed for high precision measurement requirements. This device can achieve accurate control of the loading process, which is convenient to analyze the entire membrane buckling process. By using high precision digital photogrammetry system, the configuration and configuration parameters of wrinkles are obtained, and in the experiment the second buckling phenomenon can be observed. The validity of the numerical analysis is verified by the results compared with numerical analysis.Dynamic characteristics of membrane buckling are analyzed. Eigenvalue equation of membrane vibration with out-of-plane deformation is established. Numerical method of dynamic analysis is set up based on direct perturbation method. According to this method, vibration characteristics of shear wrinkle membrane and rectangle wrinkle membrane on corner load are studied. Variation rules of nature frequency and fundamental mode are analyzed after wrinkles appear, and so as to influence of wrinkle amplitude on vibration characteristics. The corresponding relationship between vibration mode of wrinkle membrane and wrinkle membrane configuration is reached.In this paper, the formation process and the formation mechanism of membrane wrinkle are studied. The deformation characteristics of membrane wrinkle and dynamic capability of membrane after buckling are also researched. These results provide a theoretical basis for in-depth study of space membrane structure in surface accuracy control, stability control and vibration control.