Description: Finite element analyses require the modeling of spatially varying element properties. Element properties include geometric information, such as shell thickness, and modeling information, such as material orientation. You can use element property assignments to redefine on an element-by-element basis the thicknesses, offsets, section stiffness matrices, and material orientations for single-layer shell elements from the values assigned by shell section definitions. It is also possible to use element property assignments to redefine the material orientations for non-composite continuum elements from the values assigned by solid section definitions.

In some applications the element properties may vary significantly. It is not uncommon for aerospace and marine applications to have thousands of different thicknesses, offsets, and material orientations for the shell elements in a model. In such cases creating separate section definitions and element sets to accommodate the different element properties may be inconvenient. An alternative approach that can be used in certain situations is to use the section definitions to define default element properties and to redefine, as needed, specific element properties for selected elements using element property assignments.

The following example illustrates a simple use case of redefining the offset of a shell element with an element property assignment. Consider the four-element shell model shown in Figure 8–3.

Suppose that all four shell elements have a thickness of 1.0 and their constitutive behavior defined by the same material. Further suppose that shell elements 1 and 2 have the same offset of 0.1, but elements 3 and 4 have offsets of 0.3 and 0.4, respectively. One approach is to partition the model with three separate section definitions to accommodate the different offsets. Since elements 1 and 2 share common element properties (including their offsets), they can share the same shell section definition.

An alternative approach is to use a single section definition to define a default offset value of 0.1 for all four elements; then redefine the offsets for elements 3 and 4 with an element property assignment. You would define an element-based scalar distribution for elements 3 and 4 and use this distribution in the element property assignment to modify the shell element offsets. Since only elements 3 and 4 would be included in the distribution definition, the offsets for elements 1 and 2 would remain unchanged from the default value specified in the shell section definition.

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