If the section Poisson's ratio is defined as zero, the shell thickness will remain constant and the elements are, therefore, suited for small-strain, large-rotation analysis. The underlying formulation is described in Small-strain shell elements in ABAQUS/Explicit, Section 3.6.6 of the ABAQUS Theory Manual.įor conventional shell elements in ABAQUS/Standard you must specify a section Poisson's ratio as part of the shell section definition to allow for the shell thickness in finite-strain elements to change as a function of the membrane strain. Although solution accuracy may degrade as membrane strains become large, the small-strain shell elements in ABAQUS/Explicit provide a computationally efficient alternative to the finite-membrane-strain elements for appropriate applications. Many impact dynamics analyses fall within this class of problems, including those of shell structures undergoing large-scale buckling behavior but relatively small amounts of membrane stretching and compression. In ABAQUS/Explicit element types S3RS, S4RS, and S4RSW are provided for shell problems with small membrane strains and arbitrarily large rotations. The change in thickness with deformation is ignored in these elements. In ABAQUS/Standard the three-dimensional “thick” and “thin” element types STRI3, S4R5, STRI65, S8R, S8RT, S8R5, and S9R5 provide for arbitrarily large rotations but only small strains. For a multi-layered shell the temperature at the top of each layer is the same as the temperature at the bottom of the next layer. If a single section point is used for the cross-section integration, there is no temperature variation through the thickness of the shell and the temperature of the entire shell cross-section is degree of freedom 11. For a single-layer shell is the total number of integration points used through the shell section. A maximum of 20 temperature degrees of freedom can exist at a node. The temperature on the top surface is degree of freedom. The temperature on the bottom surface of the shell (the surface in the negative direction along the shell normal-see ∽efining the initial geometry of conventional shell elements, Section 23.6.3) is degree of freedom 11. Only Simpson's rule can be used for integration through the shell thickness. For shell sections integrated during the analysis ( Using a shell section integrated during the analysis to define the section behavior, Section 23.6.5) you can specify the number of section points used for cross-section integration and thickness-direction temperature interpolation at each node. The temperature variation is assumed to be piecewise quadratic through the thickness, while the interpolation on the reference surface of the shell is the same as that of the corresponding stress elements. Temperature variation through the shell thickness Furthermore, the thickness strain mode may yield a small stable time increment for thin continuum shell elements in ABAQUS/Explicit (see Shell section behavior, Section 23.6.4).Ĭontinuum shell elements are more accurate in contact modeling than conventional shells, since they employ two-sided contact taking into account changes in thickness no matter how thick the elements are compared to other element dimensions. Care should be taken when stacking a small number of continuum shell elements, because the convergence may not be monotonic (see Performance of continuum and shell elements for linear analysis of bending problems, Section 2.3.5 of the ABAQUS Benchmarks Manual). Stacking continuum shell elements allows for a richer transverse shear stress and force prediction and allows for the prediction of through-thickness pinching force. Unlike conventional shells, continuum shell elements can be stacked to provide more refined through-thickness response. These elements include the effects of transverse shear deformation and thickness change.Ĭontinuum shell elements employ first-order layer-wise composite theory. The continuum shell elements are general-purpose shells that allow finite membrane deformation and large rotations and, thus, are suitable for nonlinear geometric analysis. These elements have displacement degrees of freedom only, use linear interpolation, and allow mechanical and/or thermal (uncoupled) loading for static and dynamic procedures. Continuum shells discretize an entire three-dimensional body, unlike conventional shells which discretize a reference surface (see Shell elements: overview, Section 23.6.1). The stress/displacement continuum shell elements in ABAQUS can be used in three-dimensional analysis.
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