Research On Bending-wrinkling Characteristics Of Inflated Beams

Inflatable deployable structure is an emerging class of supporting structuresfor deployable spacecrafts in aeronautics and astronautics, which has theadvantages of light weight, small compact volume, high reliability, and large loadsbearing capacity, etc. Inflatable beams are main typical inflatable deployablestructures. In order to improve their loads bearing capacity, this research establishedtheoretical analyzing method, and conducted numerical analysis and experimentalvalidation for inflatable beams to investigate their loads bearing performance.Bending load will induce local compressive stress on inflated beam, andwrinkles occurred when bending load is larger than wrinkling load. Along withincreasing of bending load, wrinkled region will be further extended. When bendingload reaches collapse load, inflated beam are instable, and it could not undertakeany larger load. For inflated beam, load bearing performance and bending-wrinkling characteristic can be described by wrinkling load, collapse load andwrinkled region.This investigation analyzed bending-wrinkling characteristics of inflated beamunder bending load systematically. Including wrinkling occurrence, wrinklingevolution, stiffness degeneration mechanism as well as grid reinforced structures.All parameters were analyzed theoretically, numerically and experimentally. Themain contexts in this dissertation are as follows:This investigation based on wrinkling evolution of inflatable beams underbending load. For wrinkled region extended along axial direction, we proposedbending-wrinkling factor to characterize wrinkled region. Based on bending-wrinkling factor, we established theoretical analyzing model for wrinkle axialevolution of varying cross-section inflated beams, set up wrinkling bendingmoment predicative model, wrinkled region predicative model, wrinkled regionaxial boundary predicative model and collapse load predicative model, etc. For wrinkled region extended in circumferential direction, we established wrinklingangle and central axis offset predicative model based on bending-wrinkling factor,obtained wrinkling angle and central axis offset distribution based on polynomialmethod, got the method for analyzing wrinkling occurrence and extension ofvarying cross section inflated beams, and fully characterized wrinkled region.Besides, experimental system was set up for bending-wrinkling test of varyingcross section inflatable beam, combined with finite element analysis, which verifiedand validated the wrinkling occurrence predictive methods and extension analyzingmethods.Based on bending-wrinkling mechanical model of inflated beams, weintroduced equivalence pressure method and set up equilibrium bending momentanalyzing model, which for establishing inflatable pressure, central axis offset,deformation range and tube stiffness, etc. We set up varying stiffness analyzingmodel and further examined their stiffness variation and anti-bending equilibriummechanism. We got relationship between anti-bending stiffness and bending-wrinkling factor as well as wrinkling angle, obtained varying stiffness analyzingmodel considering wrinkled region and curvature variation of wrinkled region.Finally, all results were compared with numerical analyzing calculation, and ournew bending-wrinkling varying stiffness analyzing model for inflated beams aretestified to be correctly.Finite element models for inflated beams considering wrinkled region andcurvature variation of wrinkled region were brought out, corresponding shapefunction as well as stiffness expression were given, and solution process forbending-wrinkling inflated beams were established. By adopting finite elementanalyzing programs, loads bearing characterizes with different loads condition andvarious structural modals were numerical analyzed, effects of wrinkling evolutionand geometrical large deformation on inflatable beam loads bearing performancewere achieved. Those results were compared with archive references, and newbending-wrinkling inflatable beam elements introduced in this research were validated.The load deflection curves of grid reinforced inflatable beam were comparedusing bending-wrinkling inflated beam element brought in this paper and finiteelement refining analyzing model under the same condition, correctness andeffectiveness of this new inflatable beam element were validated throughexperimental test. In order to analyze grid reinforced beam with this bending-wrinkling inflated beam element, equivalent engineering constants of thin walledgrid reinforced beam were analyzed firstly, and then it was validated byexperimental and numerical analysis.All research achievements within this dissertation lay a foundation for efficientloads bearing performance analysis, structural optimization design, and bending-wrinkling characterization of large inflatable structures.