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Can I use generalized displacements to estimate joint rotations in a model that consists of solid elements only?
Yes, suppose the position vector from joint 1 to 2 is given by (dx,dy,dz). Then you can define a generalized displacement of type rotation for the rotation about the Z axis as Rz = dx*dUy – dy*dUx. Thus the coefficients to define the generalized displacement are for Joint 1: (dy, -dx, 0, 0, 0, 0), and for Joint 2: (-dy, dx, 0, 0, 0, 0).
Separate rotational generalized displacements can be defined for Rx and Ry, if needed. Once defined, these can be plotted and output in tables.
Can I use generalized displacements to calculate strains?
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page is devoted to *frequently asked questions* (FAQ) related to [generalized displacements|kb:Generalized displacements]. {info} \\ {on-this-page} h1. Can generalized displacements approximate joint rotations in a solid-element model? Yes, this will work for a model consisting only of [solid|kb:Solid] elements. Suppose the position vector from [joint|kb:Joint] 1 to 2 is given by (dx, dy, dz). A generalized displacement of type _rotation_ may be defined for rotation about the Z axis, then given as Rz = dx*dUy -- dy*dUx. Coefficients which define generalized displacement for Joint 1 are then (dy, \-dx, 0, 0, 0, 0), and for Joint 2, (-dy, dx, 0, 0, 0, 0). If necessary, separate rotational generalized displacements can be defined for Rx and Ry. Once defined, plots and tabular output are available. h1. Can generalized displacements calculate strain? Yes, when element strain is not directly reported, strain values from joint displacements may be calculated using generalized displacements. This is done through the Define > Generalized Displacements menu. |