SURFACE GEOMETRY MODELLING FOR LOGGING BALLOON SHELLS BY THE DATE BASE COMPONENTS

surface geometry modelLing for logging balloon shells BY THE DATE BASE COMPONENTS

Slepovichev A. (Forestry Academy / LenNIIProject, Saint Petersburg)

Рассмотрены вопросы генерации конечно-элементных моделей мягких (баллонных) и жестких (цельнометаллических) оболочек аэростатов для трелевки леса. Даны примеры построения адаптивных сеток конечных элементов на поверхностях аэростатов сферической и эллипсоидальной форм средствами систем компьютерной алгебры и баз данных.

Investigated are stages and features of the FEM-modelling for the soft (compressed-air) and rigid (all-metal) closed shells of logging balloons (zeppelins). By the Date Base environment [1] the follow stages are realized: 1) the rational cutting of the soft/rigid shell surfaces; 2) the adaptive FEM-grid generation on the double Gaussian curvature surfaces; 3) the stress-strain parameter sensitivity analysis of shell finite elements by variation their nodal coordinates, meridian geometry and stiffness parameters.

A set of the algorithms are applied by solution: 1) the recursive algorithm of trajectorial grid generation on the spherical & ellipsoidal surfaces [2,5]; 2) an automatic grid generation algorithm for three- and four-nodes finite elements [4] by Computer Algebra System Maple and the tabular processor Excel ; 3) an algorithm of the goal function representation for shell optimal design problem in symbolic or mixed (symbolic/numerical) form [3].

Based on these algorithms, some adaptive FEM-grids for the spherical & ellipsoidal surfaces are generated (Fig. 1,2). The principal features of these grids are follow: 1) the fluently reducing of grid step in the direction to poles (the points of nodal forces action, f.e. by collision of shell with barrier); 2) possibility of an independent generation of grid set by variation their nodal coordinates in the different domains of shell model [2,5]; 3) compatibility of the Date Base components [1] and well-known FEM-software (LIRA/Scad) file formats. The spherical & ellipsoidal shell models picted on the Figs. 1,2 are included: 1) 1296 nodes, 1272 four-nodes shell elements (Fig. 1,a); 2) 36150 nodes, 36000 four-nodes shell elements (Fig. 1,b); 3) 18075 nodes, 35925 three-nodes shell elements (Fig. 1,c); 4) 11442 nodes, 3792 eight-nodes isoparametrical shell elements (Fig. 2,a); 5) 15264 nodes, 15168 four-nodes shell elements (Fig. 2,b); 6) 7632 nodes, 15168 three-nodes shell elements (Fig. 2,c). Obtained results are used by modelling of the geometry [2,5], stiffness parameters [4] and by formulation of an optimal design problem [3] for the soft/rigid shells of logging balloons/zeppelins.

References

1. Slepovichev A. Symbolic and mixed sensitivity analysis of structures by Date Base LA_FEM.ME // OFEA-2001: - Proc. of the Intern. Conf., June, 2001. - StPetersburg, 2001. - Pp. 64-66.

2. Slepovichev A. The FEM-grid generation recursive algorithms for the double Gaussian curvature surfaces // Urban Building, Engng. Security & Ecology Problems: III Int. Scient. Conf. Reports. – Part II. – Penza. – 2001. – S. 174-176. (In Russian).

3. Slepovichev A. The goal function representation in discrete optimization problem for cyclic shell strucrures // Math. Meths & Inform. Tech. in the Economycs, Sociology & Eds: XII Int. Scient. & Tech. Conf. Reports. – Penza. – 2003. – S. 95-97. (In Russian).

4. Slepovichev A. The soft/ridgid elliptic thin-walled shell construction modeling // Modern Tech. in Mech. Engng-2003: VI Russian Scient. & Tech. Conf. Reports. Scient. Conf. Reports. – Penza. – 2003. – S. 182-184. (In Russian).

5. Slepovichev A. Uniform grid generation algorithms for spherical shells by the Date Base arrangement // Inform. Environment of University: XI Int. Scient. & Tech. Conf. Reports. – Ivanovo. – 2004. – S. 548-550. (In Russian).

Fig. 1

Fig. 2