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LS-DYNA v971 has an improved capability to add offsets to shell elements. This can be done in two ways:
- use the NLOC parameter on *SECTION_SHELL card 2. This parameter is a multiplier on the shell half-thickness, and
can vary from -1.0 to 1.0 in v970 or to any value in v971. This was previously only available for the Hughes-Liu shells, but has been extended to all the shells in v971.
- use the new option _OFFSET on the *ELEMENT_SHELL keyword. When this option is used, an additional line of input is
given which contains one parameter, the offset, in units of length. A uniform offset is applied at each node.
Even though the D3HSP mass property summary doesn’t say so, inertia is increased when a shell reference surface offset is invoked, either by NLOC or by *ELEMENT_SHELL_OFFSET. Mass is unaffected by shell offsets. The direction of the shell reference system offset makes no difference to the inertia calculation since the overall shape of the part is unknown to the code when the calculation is made.