Multigrid finite element method in the calculations of three-dimensional composite plates and beams of irregular form

To calculate the stress and strain state of three-dimensional elastic composite plates and beams of heterogeneous structure, irregular shape and static loading the method of multigrid finite elements is provided when implemented on the basis of algo-rithms of finite element method (FEM), using three-dimensional homogeneous and composite multigrid finite elements (MFE). MFE differs from existing final elements (FE) given below. At creation of m-net FE m of enclosed grids are used. Small grid generates splitting which considers non-uniform structure and FEM difficult form the others m - 1 large grids applied to decrease the dimension of FEM and with the increase in m dimension of MFE decreases. The peculiarity and advantage of FEM are the following: at the creation of FEM as much as small basic splittings composite plates are used, the beams consisting of one-net FE of the 1-st or-der i.e. in fact microapproach in finite element form is used. Such small grids allow to consider in FEM, i.e. in basic discrete models of composite plates, beams, difficult non-uniform, micronon-uniform structure and form, difficult nature of loading and fixing and to describe as precisely as possible in-tense deformed state the equations of three-dimensional theory of elasticity without introduction of additional simplifying hypotheses. Short essence of FEM is as follows. On basic splitting (on a small grid) a net final element, m ≥ 2 total potential ener-gy as the function of many variables which nodal movements of a small grid is defined. On the other m - 1 large grids (enclosed in a small grid) on FEM the function of movements used for decreasing dimension of function allowing to project FEM of small dimension is built. The procedures of creation of FEM of lamellar and frame types of complex type are stated. The advantages of FEM are in generat-ing discrete models of small dimension and net de-cisions with a small error. The example of calcula-tion of a composite beam with application of three-dimensional two-net FE of difficult form is given.