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Delta Rosette
The preceding development has been applied to the rectangular rosette, but the same procedure can be used to derive corresponding data-reduction equations for the delta rosette shown below. When grid angles , + 60 degrees, and + 120 degrees are successively substituted into Eq. ( 515.1 ), the resulting three equations can again be solved simultaneously for the principal strains and angle. Thus, for the delta rosette:

   (515.6)

Delta rosette (l) installed on a test surface, with Grid 1 at the angle from the major principal strain direction, (r) rosette grid axes superimposed on Mohr's circle for strain. Note that Grid 2 is to be viewed as +60 degrees (CCW) from Grid 1 in the rosette, and +120 degrees in Mohr's circle.

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