Tee Rosettes having two elements at 0-90 deg. The relationships given here for stress do not generally apply to such materials.
Calculations are valid only for homogeneous, isotropic materials in the linear-elastic strain range.
The equations above for calculating principal strains and stresses from rosette strain measurements assume that the grid elements are numbered in a particular manner. Treating the latter situation first, it is always necessary in a rectangular rosette that grid numbers 1 and 3 be assigned to the two mutually perpendicular grids. Any other numbering arrangement will produce incorrect principal strains and stresses. Similarly, in a delta rosette, Grids 2 and 3 must be 60 deg and 120 deg away, respectively, in the same direction from Grid 1. By definition, is the angle from the axis of Grid 1 to the nearest principal axis.