Soft Release Mechanism Design Of New Generation Launch Vehicle

The hold down and soft release (HDSR) during the liftoff phase is a key technology in developing high reliability launch vehicle in China. Taking the development of the soft release mechanism (SRM) in the HDSR system of the new generation launch vehicle as background, this dissertation studies the related problems including the finite element analysis method of contact problems, the shape design sensitivity analysis method of contact problems, the experimental test method of the SRM's soft release characteristics, the shape optimal design method of the SRM and the launch vehicle's structural transient response analysis method systemically. The main research contents and results in this dissertation are summarized as follows.A new algorithm for the finite elemnt analysis of two-dimensional multi-body finite deformation elastoplasiticity frictional contact problems is proposed. The constraint conditions in the contact boundary are treated with the active set strategy and mortar method. The same nominal penalty parameters are adopted in the normal and tangential directions of mortar contact segments. The contact constraint conditions are regularized with the moving friction cone algorithm based on the nominal penalty parameters. The corresponding formulations of contact tangential stiffness matrix and contact force vector are derived. The advantages of the moving friction cone algorithm and the mortar method are inherited in this algorithm, whose formulations are concise and convenient to program. The accuracy and efficiency of this algorithm are illustrated by numerical examples.A new SRM design project is proposed and a primary SRM which fulfils the integrative design department's requirements is designed. The soft release characteristics of the SRM are studied systemically by the proposed contact algorithm. The basic soft release course of the SRM is analysed. The influence of machining errors on the soft release force vs. displacement curve and the curve's adjustable characteristics are discussed. And the basic soft release characteristics of the SRM are studied experimentally.A new analytic algorithm for the shape design sensitivity analysis of two-dimensional multi-body finite deformation elastoplasticity frictional contact problems is proposed. Differentiating the discretized governing equations of the proposed contact algorithm with the shape design variables, the new analytic shape design sensitivity analysis formulations of this path-dependent problem are obtained. The nodal displacement sensitivity equations can be solved at each increment step without iterations. The accuracy and efficiency of this shape design sensitivity analysis algorithm are illustrated by numerical examples. In comparison with the classical shape design sensitivity analytic algorithms of two-dimensional multi-body frictional contact problems, the proposed algorithm is more concise and convenient to program.An innovative shape optimal design method of the SRM is proposed and an optimal SRM is obtained. The outside shape of the tube in the SRM is characterized by the cubic B-spline curve. The coordinates of given data points on the curve are used as the design variables. Minimizing the weighted square sum of the distances between finite points in the SRM's soft release force vs. displacement curve and object curve is used as the optimal object. The sensitivities of the optimal object function to these coordinates are computed by the proposed sensitivity analysis algorithm and then an optimal shape of the SRM is achieved. The soft release characteristics of the optimal SRM are studied by the numerical simulation and experiment methods.A new numerical simulation method for the launch vehicle's structural transient response analysis during the HDSR phase is proposed. In this method, the fields function, selected group analysis function and the CBUSH1D element's nonlinear displacement vs. load function of MSC.Patran/Nastran are used effectively. The new generation launch vehicle's structural transient responses during the HDSR phase are analyzed. The soft release efficiencies of the SRM are evaluated.In conclusion, some advance in the theory and method related to designing SRM of the new generation launch vehicle is achieved in this dissertion. The related results would provide some valuable references to the integrative design department in SRM design.