Dynamic Analysis Of Strap-on Space Structure

Strap-on carrier rocket is a kind of complex space structure. Owing to its importance, the dynamic analysis should fulfil higher requirements. Not only the eigen-frequencies computed should be of higher precision, but also the corresponding vibration modes should be close to experimental results.After briefly reviewing the references concerning dynamic substructure techniques and semi-analytical ring element, for shells of revolution the thesis mainly present the modelling and numerical analysis of strap-on carrier rocket done by auther:(1) The strap-on rocket is modelled as the shells of revolution connected with rods and beams. Central stage, four boosters and connecting members are regarded as different substructures. Compatibility conditions between substructures and modal systhesis equations are derived using piese-wise generalized variational principle .(2) The strap-on rocket is modelled as substructures of revolutional shells connected with substructures consisted of three-dimensional finite elements. The regular regions of central stage and boosters are formulated with substructure of revolutional shell, while the geometrical irregular regions and connecting regions subjected by concentrated forces are formulated with substructure of three-dimensional finite elements. The compatibility conditions between these two kinds of substructures and modal synthesis equations are also derived using piese-wise generalized variational principle. A scheme of partial-fixed-interface modal synthesis iS proposed. This scheme can be used to further reduce interface degrees of freedom, especially for the above mentioned substructure model. A discussion on its convergence is also given.(3) A quarter of a strap-on rocket instead of the whole struture is modelled by using of the geometrical symmer-try. For the revolutional shell of central stage, the terms of Fourier series can be decoupled into four subgroups . The unknowns in each group can be solved independently. In this way the high efficiency of the numerical analysis has been achieved.(4) A testing model of strap-on rocket consisted of a central stage surrounded with four boosters is computed, the numerical results obtained are compared with the experimental results and available numerical results using multi-beam approximation.(5) In addition, a scheme of re-analysis is suggested to improve the accracy of the dynamic analysis using semi-analytical ring element of revolutional shells.The numerical examples show that the three models stated above for the dynamic analysis of strap-on rocket and the dynamic re-analysis scheme for semi-analytical finite elements are reasonable, feasible and quite effective. the...