launch vehicle's soft release characteristic control based on the new shape design sensitivity analysis algorithm and optimization of elasto-plasticity contact problems with friction

Paper number

IAC-08.C2.8.10

Author

Dr. Wan Jun, National University of Defence Technology, China

Coauthor

Dr. Guo-jin Tang, National University of Defense Technology, China

Year

2008

Abstract

The hold down and release system can improve the liftoff reliability of launch vehicle, but it often causes the transient loads during the release phase. To reduce the transient response of the launch vehicle, the soft release mechanism (SRM) was considered to be added to offer the restrain force to the launch vehicle via the contact and plastic deformation between the flight side and ground side of the SRM. In a large number of numerical simulations, it was found that the characteristic of the SRM’s restrain force-displacement curve was very important to efficiently reduce the launch vehicle’s structure transient response during the release phase. An innovative approach was proposed to control the launch vehicle’s soft release characteristic based on the shape design sensitivity analysis and optimization of the SRM.

Due to the drawbacks of global finite difference sensitivity method and semi-analytical sensitivity method, a new analytical shape design sensitivity analysis algorithm of multi-body two-dimensional contact problems with friction was proposed in this study. In the direct analysis of contact problems, the normal and tangent contact conditions were regularized by the moving friction cone algorithm and the discretized equations governing the direct problem were formulated. In the shape design sensitivity analysis, the incremental (path-dependent) sensitivity problem was derived by the direct differentiation of the discretized equations governing the direct problem. Contrast to the current shape design sensitivity algorithm of frictional contact problems, the algorithm proposed in this study was not required to divide into normal and tangential direction and then was more concise and convenient to program. 

To the aim of controlling the soft release characteristic, a novel SRM was proposed in our study. The SRM was moderate manufacturing difficulty and tolerant of machining errors. The shape of the SRM was represented by the cubic B-spline curve, and the control points of the B-spline were used as the design variables. The sensitivity of the restrain force with respect to the control points was obtained by the proposed shape design sensitivity algorithm. And the restrain force–displacement curve which could effectively reduce the launch vehicle’s structure transient response during the release phase was used as the optimization objects. Then an optimal shape of the SRM was obtained by the proposed approach. Numerical examples indicated that the optimal SRM could efficiently reduce the transient response of the launch vehicle during the release phase.

Abstract document

IAC-08.C2.8.10.pdf

Manuscript document

IAC-08.C2.8.10.pdf (🔒 authorized access only).

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